Dissertations / Theses on the topic 'Animal physiology-systems'

Cooling systems used to reduce heat stress in dairy operations require high energy, water usage, or both. Steady increases in electricity costs and reduction of water availability and an increase in water usage regulations require evaluation of passive cooling systems to cool cows and reduce use of water and electricity. A series of experiments were conducted to evaluate the use of heat exchangers buried as components in a conductive system for cooling cows. In the first experiment six cows were housed in environmentally controlled rooms with tiestall beds, which were equipped with a heat exchanger and filled with 25 cm of either sand or dried manure. Beds were connected to supply and return lines and individually controlled. Two beds (one per each kind of bedding material) constituted a control group (water off), and the other 4 (2 sand and 2 dried manure) used water at 7°C passing through the heat exchangers (water on). The experiment was divided in 2 periods of 40 d, and each period involved 3 repetitions of 3 different climates (hot and dry, thermo neutral, and hot and humid). Each cow was randomly assigned to a different treatment after each repetition was over. Sand bedding remained cooler than dried manure bedding in all environments and at all levels of cooling (water on or off). Results from this experiment demonstrated that bed temperatures were lower and heat flux higher during the bed treatment with sand and water on. We also detected a reduction in core body temperatures, respiration rates, rectal temperatures, and skin temperatures of those cows during the sand and water on treatment. Feed intake and milk yield numerically increased during the bed treatment with sand and water on for all climates. No major changes were observed in the lying time of cows or the composition of the milk produced. The efficiency of conductive cooling as a heat abatement technique in dairy production is highly correlated with the distance between the cooling system and the skin of the cow and the type of bedding material used. A second experiment was conducted to identify possible improvements in the utilization of conductive cooling for cooling cows. Heat exchangers buried 12.7 cm below the surface as components in a conductive system ware evaluated in this study. Six cows were housed in environmentally controlled rooms with tie-stall beds, which were equipped with a heat exchanger and filled with 12.7 cm of either sand or dried manure. Beds were connected to supply and return lines and individually controlled. Two beds (one per bedding material type) constituted a control group (water OFF), and the other four (two sand and two dried manure) used water at 7°C passing through the heat exchangers (water ON). The experiment was divided into two periods of 40 days and each period involved three repetitions of three different climates hot dry (HD), thermo neutral(TN) and hot humid (HH). Each cow was randomly assigned to a different treatment after each repetition was over. The sand and water on treatment was the most efficient treatment under heat stress conditions (humid or dry heat). Cows in stalls with the sand and water on treatment demonstrated lower rectal temperatures, respiration rates, skin surface temperatures and core body temperatures compared to the other three treatments. Additionally, the sand and water on treatment increased milk yield and resting time of cows under heat stress. Also, the sand and water on treatment had the lowest bed surface temperatures and highest heat exchange compared to the other treatments. From these two experiments we confirm that heat exchangers are a viable heat abatement technique that could reduce the heat load of heat stressed cows; however, this system should be paired with additional cooling systems (e.g. fans and or misters) to most efficiently reduce the negative effects of heat stress on dairy production. Additionally, Sand was superior to dried manure as a bedding material in combination with heat exchangers. To make further recommendations of the use of heat exchangers in commercial dairy farm, a third study was developed. Based on the data obtained in the previous experiments, a comprehensive energy balance was developed to fully understand conductive cooling in two different environments (HD and HH), two bedding materials (sand and dried manure) and two depths between cows and the heat exchangers (25 vs. 12.5 cm). The energy balance estimates indicated that sand is the most efficient bedding material when utilized as bedding material with conductive cooling in both hot dry and hot humid environments. In the hot-dry environment there was an increase in the conductive heat exchanged with the reduction in bedding depth to 12.5 cm, however this did not result in a reduction in the heat storage of cows. In the hot-humid environment when heat exchangers were placed 12.5 cm from the top of the bed there was an increase in both the conductive heat loss and heat storage of cows when compared to 25 cm. Additionally, results demonstrated that the efficiency of heat exchangers as measured by heat flux was improved when heat exchangers were at a depth of 12.5 cm. The sensibility analysis indicated that a reduction in the depth and/or an increase in the thermal conductivity of both bedding materials would maximize conductive heat exchange. These results should be utilized as recommendations for the utilization of heat exchangers and conductive cooling in commercial dairy farms. Evaporative cooling is widely used in dairy farms located in arid environments. Even though, these cooling systems have been shown to effectively reduce the heat stress of lactating dairy cows, a growing shortage of water and rising cost of electricity compromise its future usage. An experiment was developed to compare two evaporative cooling systems, their interaction with lactating dairy cows and their usage of natural resources. The efficacy of 2 evaporative cooling systems (Korral Kool, KK, Korral Kool Inc., Mesa, AZ; FlipFan dairy system, FF, Schaefer Ventilation Equipment LLC, Sauk Rapids, MN) was estimated utilizing 400 multiparous Holstein dairy cows randomly assigned to 1 of 4 cooled California-style shade pens (2 shade pens per cooling system). Each shaded pen contained 100 cows (days in milk = 58 ± 39, milk production = 56 ± 18 kg/d, and lactation = 3 ± 1). Production data (milk yield and reproductive performance) were collected during 3 months (June–August, 2013) and physiological responses (core body temperature, respiration rates, surface temperatures, and resting time) were measured in June and July to estimate responses of cows to the 2 different cooling systems. Water and electricity consumption were recorded for each system. Cows in the KK system displayed slightly lower respiration rates in the month of June and lower surface temperatures in June and July. However, no differences were observed in the core body temperature of cows, resting time, feed intake, milk yield, services/cow, and conception rate between systems. The FF system used less water and electricity during this study. In conclusion, both cooling systems (KK and FF) were effective in mitigating the negative effects of heat stress on cows housed in arid environments, whereas the FF system consumed less water and electricity and did not require use of curtains on the shade structure. Results of this research indicate that effective use of conductive cooling in combination with efficient evaporative cooling systems offer opportunities to reduce both water and electricity consumption on dairy farms under both hot dry and hot humid environments.

This thesis focuses on the renin-angiotensin system and atrial natriuretic factors (ANF) two hormonal systems which are stimulated and which may exert important antagonizing actions on the regulation of mean arterial pressure (MAP) and body fluid homeostasis during pregnancy. All experiments were conducted in healthy nonpregnant and/or pregnant (gestational age of 105 to 140 days, term = 145 days) mixed breed ewes, using a facility designed for studies of large animals. Findings from the first study with unilateral denervated kidneys provide evidence that renal nerves are a necessary component in the control of renin secretion in both nonpregnant and pregnant ewes. The second study demonstrates that angiotensin II (AngII) and ANF do not account for the dramatic suppression of renin secretion in response to the reduction of renal perfusion pressure in sheep with bilateral renal denervation. The data from these two studies suggest that the renal baroreceptors influence renin secretion indirectly through activation of renal afferents rather than by a direct action on the juxtaglomerular apparatus. In order to study the possible effects of increased plasma AngII on ANF production during pregnancy, four doses of AngII (0.5, 5, 20, 40 ng/kg/min) and nitroprusside were simultaneously infused to separate indirect hemodynamic actions on ANF secretion from direct hormonally mediated effects on ANF secretion by AngII. The data clearly show that AngII increases plasma ANF in a dose-dependent manner but: only in the presence of the AngII pressor effect. A striking finding was the demonstration that the natriuretic and diuretic responses to intrarenal artery infusion of three doses of ANF (0.3, 1.5, 3.0 pmol/kg/min) are increased during ovine pregnancy and these responses are solely limited to actions on the distal part of the nephron without altering renal vascular or glomerular function. Finally, a study with 10 days of intrarenal artery infusion of low dose AngII (1 ng/kg/m

To evaluate the effect of two different cooling systems on production, physiological, and hormonal responses, 37 Holstein and 26 Brown Swiss dairy cows were allotted to three treatments. A control group of cows had access to only shade (C). A second group was cooled with spray and fan (S/F) and the third group was under an evaporative cooling system called Korral Kool&circR; (KK). The trial lasted from May to September with a daily maximum temperature-humidity index from 73 to 85. Milk production differences in Holstein cows were significantly increased by KK and S/F. No treatment differences in milk production were observed in Brown Swiss cows. Protein percentages were higher in C group compared to Korral Kool group only in Brown Swiss cows, while fat percentage were similar among treatments in Holstein cows. Rectal temperatures and respiration rates of the C group were higher than S/F and KK in both Holstein and Brown Swiss cows. Triiodothyronine levels in milk were significantly higher in KK group compared to S/F and C groups, while cortisol levels were lower in C group than S/F and KK. Similar differences were observed in body weight and body condition score changes between treatments in Holstein or Brown Swiss cows. Pregnancy rate was increased in the groups under the cooling systems in Holstein cows, however this effect was not observed in Brown Swiss cows where C group had a higher pregnancy rate than cooled groups. The cows under cooling systems spend more time eating and outside of the shade in the early afternoon (12:00 to 15:00) than control group. Cows injected with bST (bovine somatotropin) increased milk yield significantly only in Brown Swiss cows, whereas respiration rates were increased in both breeds by bST but rectal temperatures were similar between bST and non-bST cows. These results demonstrate that both cooling systems are an alternative to increase productive and reproductive performance and comfort of Holstein cows during summer in hot-dry climates. The physiological responses of Brown Swiss cows indicated a better adaptation to a hot climate, however their milk production was lower than in Holstein cows.

Erythropoiesis maintains stable tissue oxygenation in the basal state, while accelerating red cell production in anemia, blood loss or high altitude. The principal regulator of erythropoiesis is the hormone erythropoietin (Epo). In response to hypoxic stress, Epo can increase a 1000-fold, driving erythropoietic rate by up to 10-fold. It’s been suggested that survival pathways activated by the Epo receptor (EpoR) underlie its regulation of erythropoietic rate. A number of apparently redundant EpoR survival pathways were identified in vitro, raising the possibility of their functional specialization in vivo. Here I assessed the roles of three survival pathways activated by EpoR in erythroblasts in-vivo: the suppression of cell-surface Fas and FasL, the suppression of the pro-apoptotic regulator Bim, and the induction of the anti-apoptotic regulator Bcl-xL. I used the novel CD71/Ter119 flow-cytometric method of identifying erythroblast maturation stages in vivo to measure these apoptotic pathways in fetal liver and adult erythropoietic tissues. I found that these pathways differ markedly in their regulation of erythropoietic rate. Using mouse genetic models, I found that apoptosis mediated by interaction between erythroblasts that co-express cell-surface Fas and FasL plays a key autoregulatory role in stabilizing the size of the erythroblast pool in the basal state. Further, mice mutant for Fas or FasL showed a delayed erythropoietic response to hypoxia or high Epo. This suggests that Fas and FasL accelerate the stress response by providing an apoptotic ‘cell reserve’ that can be rescued by Epo in stress. I also examined the in-vivo behavior of two cell-intrinsic apoptotic regulators, Bcl-xL and Bim, previously unexamined in stress. The induction of Bcl-xL was rapid but transient, whilst the suppression of Bim was slower but persistent. My data suggest that Bcl-xL is a key mediator of EpoR’s anti-apoptotic signal very early in the stress response, before Bim and Fas are suppressed. Bcl-xL adaptation to high Epo occurs through inhibition of Stat5 activation, and resets it for the next acute stress. My findings suggest that in vivo, Epo regulates erythropoietic rate through erythroblast apoptosis, and that various apoptotic regulators play distinct and unique roles in this process. My work provides new molecular insights into erythropoiesis that are relevant to cytokine biology and to clinical approaches of disease treatment.

In this research we observed the effects of basil on stress modulation and immune response in vertebrates in vitro and in vivo.

The in vitro study was done on mice spleen cell cultured with Holy basil and Thai basil to observe their proliferation stimulation to spleen cells and spleen T cell. The study was done in presence and absence of Concanavalin A (Con A)- a mitogen known as a T cell proliferation stimulator. A single cell suspension of mice spleen cells was incubated with four different dilutions of Holy and Thai basil (1:1, 1:5, 1:25, and 1:125). No significant differences have been found between control groups (cells without factor) and treatments suggesting the basils did not show any stimulation to spleen cell or spleen T cell proliferation.

The in vivo study was conducted with tilapia reared in aquaponics system to observe the stress modulating property of Holy basil. The physiological and immunological responses and growth performances of stressed and basil fed tilapia have been observed. There were four groups of fish- Control (unstressed) fish fed with commercial feed, Stressed fish fed with commercial feed, Control (unstressed) fish fed with basil-supplemented commercial feed, and Stressed fish fed with basil-supplemented commercial feed. The experiment was six weeks long. The parameters which have been recorded were- serum cortisol, packed cell volume, plasma protein, hepatosomatic index, spleen-somatic index, lysozyme activity, macrophage phagocytic capacity, length, weight, and condition factor. The results did not suggest any effects of basil on stress response. But the harmful effect of stress on fish growth and immune response was evident, as the stress groups showed significantly lower length, weight and condition factor.

The aquaponics system used in this study was also investigated for its production of the crops. Total fish production after eight weeks of placing the fingerlings in the aquaponics system were as follows- Control group: 6.00 g/L, Stressed group: 3.98 g/L. It suggests that stress can result in far less profit in aquaponics production.

Total plant production after 5 months is 6,521.10 g/sq. m (leaf with stem of marketable size) for Holy basil and 7219.73 g/sq. m for Thai Basil. This result suggests that basils are a viable crop in aquaponics and Thai basil would be more productive as the plant crop than Holy basil when grown on aquaponics.

This thesis documents the annual profiles of the primary reproductive steroids testosterone (T), 17beta-oestradiol (E2) and progesterone (P4), in the reproductive cycles of male and female blue-tongued lizards, Tiliqua nigrolutea. Data collected from a large captive population over three consecutive reproductive seasons are included. Reproductive cycles are discussed in the context of other viviparous squamate reptiles, while a broader comparative approach is used to consider patterns of steroid biosynthesis and peripheral metabolism. The annual patterns of circulating concentrations of T, E2 and P4 have been characterised for both sexes. In males, peak plasma T (10.9 +/- 3.00 ng ml-1) and E2 (778.0 +/- 120.00 pg ml-1) concentrations occur coincident with late spermatogenesis and observations of mating, respectively. Plasma P4 concentrations remain basal (< 1.2 ng ml-1) throughout the annual reproductive cycle. In females, increasing plasma E2 concentrations (275.2 +/- 33.87 pg ml-1 - 715.1 +/- 106.68 pg ml-1) are associated with vitellogenesis and plasma T peaks (6.3 +/- 0.63 ng ml-1) in the mating and peri-ovulatory period. In pregnant females, plasma P4 concentrations are elevated for the first two thirds of gestation, peaking in the second trimester at 12.7 +/- 1.27 ng ml-1 and falling rapidly prior to parturition. Concurrently, plasma P4 concentrations in non-reproductively active adult females remain basal (1 - 2 ng ml-1) throughout the year. There is good circumstantial evidence for a multiennial reproductive cycle in females. Parturition occurs late in the active season, presumably leaving little time for females to store sufficient fat reserves to become vitellogenic in the following spring: reproductive opportunities are effectively missed in at least one year following a reproductive effort. Observed reproductive behaviours, including agonistic male - male interactions, mating, and parturition, are documented. An investigation of gonadal steroid biosynthetic pathways in this viviparous squamate is presented. This compares variation in the relative contributions of the delta-4 and delta-5 steroidogenic pathways according to sex and reproductive condition. The delta-4 pathway predominates in both sexes, aligning this species phylogenetically with other reptiles. However, there are clear differences between sexes and with changing reproductive condition in the patterns of production of pathway intermediates and end-products. Additionally, detection of a possibly novel polar steroid as a major end-product of steroid biosynthesis in both sexes is reported. Peripheral (extragonadal) metabolism of T and E2 in a number of reproductively relevant steroid target tissues is compared at times of year chosen to represent three clearly distinctive reproductive conditions in each sex. There are differences both between sexes, between tissue types and with changing reproductive condition in the relative proportions of steroid conjugates and non-conjugated derivatives produced. Biosynthetic pathway activity and peripheral steroid metabolism both appear to be plastic in response to changing reproductive condition in Tiliqua nigrolutea. With a comprehensive database of information about the reproductive endocrinology and physiology of Tiliqua nigrolutea, this species is now available as a model to further examine selected aspects of the steroid hormone control of reproductive physiology and behaviour in a cool temperate, viviparous reptile.

This thesis documents the annual profiles of the primary reproductive steroids testosterone (T), 17beta-oestradiol (E2) and progesterone (P4), in the reproductive cycles of male and female blue-tongued lizards, Tiliqua nigrolutea. Data collected from a large captive population over three consecutive reproductive seasons are included. Reproductive cycles are discussed in the context of other viviparous squamate reptiles, while a broader comparative approach is used to consider patterns of steroid biosynthesis and peripheral metabolism. The annual patterns of circulating concentrations of T, E2 and P4 have been characterised for both sexes. In males, peak plasma T (10.9 +/- 3.00 ng ml-1) and E2 (778.0 +/- 120.00 pg ml-1) concentrations occur coincident with late spermatogenesis and observations of mating, respectively. Plasma P4 concentrations remain basal (< 1.2 ng ml-1) throughout the annual reproductive cycle. In females, increasing plasma E2 concentrations (275.2 +/- 33.87 pg ml-1 - 715.1 +/- 106.68 pg ml-1) are associated with vitellogenesis and plasma T peaks (6.3 +/- 0.63 ng ml-1) in the mating and peri-ovulatory period. In pregnant females, plasma P4 concentrations are elevated for the first two thirds of gestation, peaking in the second trimester at 12.7 +/- 1.27 ng ml-1 and falling rapidly prior to parturition. Concurrently, plasma P4 concentrations in non-reproductively active adult females remain basal (1 - 2 ng ml-1) throughout the year. There is good circumstantial evidence for a multiennial reproductive cycle in females. Parturition occurs late in the active season, presumably leaving little time for females to store sufficient fat reserves to become vitellogenic in the following spring: reproductive opportunities are effectively missed in at least one year following a reproductive effort. Observed reproductive behaviours, including agonistic male - male interactions, mating, and parturition, are documented. An investigation of gonadal steroid biosynthetic pathways in this viviparous squamate is presented. This compares variation in the relative contributions of the delta-4 and delta-5 steroidogenic pathways according to sex and reproductive condition. The delta-4 pathway predominates in both sexes, aligning this species phylogenetically with other reptiles. However, there are clear differences between sexes and with changing reproductive condition in the patterns of production of pathway intermediates and end-products. Additionally, detection of a possibly novel polar steroid as a major end-product of steroid biosynthesis in both sexes is reported. Peripheral (extragonadal) metabolism of T and E2 in a number of reproductively relevant steroid target tissues is compared at times of year chosen to represent three clearly distinctive reproductive conditions in each sex. There are differences both between sexes, between tissue types and with changing reproductive condition in the relative proportions of steroid conjugates and non-conjugated derivatives produced. Biosynthetic pathway activity and peripheral steroid metabolism both appear to be plastic in response to changing reproductive condition in Tiliqua nigrolutea. With a comprehensive database of information about the reproductive endocrinology and physiology of Tiliqua nigrolutea, this species is now available as a model to further examine selected aspects of the steroid hormone control of reproductive physiology and behaviour in a cool temperate, viviparous reptile.

Heart rate variability (HRV), or the variation in time between adjacent heart beats over time, is a non-invasive proxy measure of autonomic nervous system (ANS) function that has been used regularly in studies focused on evaluating livestock stress and welfare. The autonomic nervous system regulates involuntary physiological processes (e.g. respiration and heart rate) and consists of two main components, the parasympathetic (PNS), and sympathetic (SNS) branches, which act to maintain bodily homeostasis (PNS) or stimulate the “fight-or-flight” response after exposure to a stressor (SNS). Traditional linear HRV measures provide an estimation of overall autonomic activity or changes to the balance between the PNS and SNS branches by evaluating changes to the mean, variance, or frequency spectra of the R-R intervals.

To interpret HRV data obtained via linear HRV measures, particularly spectral HRV analysis, a linear assumption has to be assumed where SNS and PNS activity act in a purely antagonistic manner. However, this assumption is not always met. In many cases, ANS activity is altered in a nonlinear manner, which is reflected to some degree in the variability of heart rate output. Therefore, HRV measures that evaluate nonlinear changes to organizational or structural aspects of the R-R interval variability may be a useful compliment to traditional linear HRV measures for distinguishing between stressed and non-stressed states. The purpose of this dissertation was to evaluate the use of nonlinear HRV measures for evaluating dairy calf disbudding pain, piglet castration pain, growing pig heat stress, and as potential indicators of the subsequent immune response to a lipopolysaccharide (LPS) challenge in growing pigs.

Chapter 1 provides a knowledge base for understanding HRV and its use as a measure of autonomic stress in studies with livestock species. A brief explanation of animal welfare science, measures used to evaluate an animal’s welfare, and a demonstration of need for non-invasive physiological measures is provided before discussing the physiological basis of HRV. Relevant linear and nonlinear HRV measures are explained and examples of their use in livestock stress research are provided. Finally, a rationale for the studies conducted in this dissertation is presented.

Chapter 2 evaluates the use of HRV as an indicator of castration pain in 9-d-old piglets over a 3-d experimental period. Compared to sham castrated piglets, surgically castrated piglets exhibited greater low frequency to high frequency ratios (LF/HF), reduced sample entropy (SampEn), and greater percent determinism (ÞT) during the post-castration period. However, postural behavior was not different between treatments and serum cortisol concentrations only tended to differ between treatments at 1 and 24 h post-castration treatment, with surgically castrated pigs having numerically greater serum cortisol concentrations at both timepoints. These results demonstrate the ability of nonlinear HRV measures (SampEn and ÞT) to complement the physiological interpretation of linear HRV measures (LF/HF) in response to castration. Specifically, pigs who were surgically castrated exhibited more regularity (SampEn) and periodicity (ÞT) in their HRV data, and potentially more sympathetic activity (LF/HF) compared to sham castrated piglets, indicating greater pain-related stress. Additionally, HRV was a more sensitive measure of the stress response to castration than readily identifiable behaviors such as posture and the serum cortisol response.

Chapter 3 evaluates the use of HRV as an indicator of disbudding pain in dairy heifer calves (4 to 7-wk of age) over a 5-d experimental period. Calves who were given lidocaine and meloxicam prior to disbudding exhibited lower mean R-R interval (RR) values and a greater short-term detrended fluctuation analysis scaling exponent (DFAα₁) than sham disbudded calves. Together, these results indicate that calves who received pain mitigation exhibited greater pain-related stress (RR) and reduced physiological complexity in their heart rate signal (DFAα₁). Calves who were disbudded without pain mitigation had an intermediate response compared to sham disbudded calves and calves provided lidocaine and meloxicam. However, their numerical values closely followed those of calves provided lidocaine and meloxicam. These results demonstrate the usefulness of nonlinear HRV measures (DFAα₁) for evaluating nonlinear and correlational aspects of physiological complexity in response to disbudding. Additionally, the HRV results suggest that the provision of meloxicam does not reduce the amount of pain-related stress experienced by calves following disbudding.

Chapter 4 evaluates the use of HRV as an indicator of heat stress in growing pigs exposed to an acute heat episode. Heat stressed pigs exhibited greater body temperatures and spent less time in an active position compared to thermoneutral control pigs. Additionally, heat stressed pigs displayed an altered nonlinear HRV response to the acute heat phase compared to non-heat stressed control pigs. Specifically, heat stressed pigs exhibited lower SampEn and tended to exhibit greater ÞT, but no alterations to linear measures were observed in response to the acute heat episode. The low frequency to high frequency ratio was higher in heat stressed pigs during the period following the acute heat phase. Therefore, nonlinear HRV measures (particularly SampEn) may be more sensitive to the immediate physiological stress response to increased environmental temperature than traditional linear HRV measures.

Chapter 5 evaluates the use of baseline HRV as a potential indicator of the subsequent cortisol and pro-inflammatory cytokine response to an LPS challenge in growing pigs. The time for a pig to approach a human (approach time) prior to LPS administration was inversely related to baseline standard deviation of the R-R intervals (SDNN), and directly related to RR and the mean length of diagonal lines in a recurrence plot (Lmean). This result may have implications for the use of HRV as a measure of temperament in livestock species, since pigs with lower baseline SDNN (i.e. greater stress) and greater baseline Lmean (i.e. increased periodicity length in HRV data; greater stress) values took longer to approach a human observer before LPS administration (which occurred 1 d after HRV measurement). Area under the curve values for approach time following LPS administration were inversely related to high frequency spectral power (HF) and directly related to body weight, where pigs with low baseline HF values (i.e. lower parasympathetic activity) and higher body weights were slower to approach a human observer following LPS administration. Additionally, pigs with greater Lmean values had a greater change in body temperature following LPS administration. In conclusion, while baseline HRV measures were not directly representative of the cortisol or cytokine response following an LPS challenge, HF and Lmean may be useful indicators for evaluating certain aspects (sickness behavior and fever) of the innate immune response to an LPS challenge.

In conclusion, these studies demonstrate the usefulness of nonlinear HRV measures for evaluating livestock stress. Measures such as sample entropy and those derived from recurrence quantification analysis (ÞT, Lmean) seem to be particularly useful for complementing traditional linear HRV measures and, in some cases, are more sensitive measures of the physiological stress response (see chapter 4). Therefore, their inclusion in future studies on livestock HRV is warranted. However, further work is needed to fully elucidate the physiological significance of nonlinear HRV measures and their response to stress.

Experiments were conducted to evaluate the ability of prebiotic and probiotic supplementation of commercial fish feed to improve the physiological, immunological, and growth responses of stressed Nile tilapia. To investigate these objectives, tilapia were divided in two major groups: control fish (fed regular commercial feed) and stressed fish (induced by dietary cortisol supplemented to regular commercial feed). Stressed fish were further divided into three sub-groups: stressed fish fed regular feed, stressed fish fed probiotic-supplemented feed, and stressed fish fed a mixture of prebiotic and probiotic supplemented feed. Fish were maintained and tested over an eight-week long experimental period. A variety of physiological, immunological, and growth parameters were measured over the course of the experimental period. These parameters include: serum cortisol, blood glucose, plasma protein, packed cell volume, hepato-somatic index (HSI), spleen-somatic index (SSI), lysozyme activity, feed conversion ratio (FCR), specific growth rate (SGR), protein efficiency ratio (PER), length gain, weight gain, length gain, and condition factor (K). The results of this study does not support the use of these specific prebiotic and probiotic as functional feed additives in Nile tilapia at the levels tested in this study. Further research is needed to determine which probiotic species are best suited for use in Nile tilapia and which prebiotic, when used in combination, will allow these probiotics to have maximum effect.

Stressors in the aquaculture environment can lead to negative impacts on growth and immune health, resulting in susceptibility to infectious diseases. These stressors are expected to increase as the growth of aquaculture continues to rise to meet demands for quality fish protein. Isoflavones, as a crude extract or as a pure isolate, may be effective in modulating the stress response, promoting growth and immunity. The objective of these studies was to examine the effect of various pure isoflavone isolates and crude isoflavone extracts on stress, growth, and immunity. Nile tilapia (Oreochromis niloticus) were stressed by adding hydrocortisone to the feed. In a 7-week study, pure isoflavone isolates of genistein and puerarin were evaluated to determine their respective effects on stress, growth, and immunity. A separate 10-day physiological and 6-week growth study focused on crude isoflavone extracts from kudzu (Pueraria lobata), red clover (Trifolium pratense), and soybean (Glycine max) was performed to determine their respective effects on stress, growth, and immunity. Numerous physiological parameters of the fish were measured (serum cortisol concentration, blood glucose concentration, hematocrit, hepatosomatic index, plasma protein concentration, lysozyme activity, and spleensomatic
index) to determine the effects of these pure isoflavone and crude isoflavone extracts on the modulation of stress and immunity. Many growth parameters were examined (length, weight, condition factor, weight gain, specific growth rate, feed intake, feed conversion ratio, and protein efficiency ratio) as well to determine the effects of these pure isoflavones and isoflavone extracts on growth. The addition of isoflavone and crude isoflavone extracts to the diet of Nile tilapia ameliorated some of the negative consequences of stress. Compared to stressed fish fed commercial feed, genistein and puerarin added to the diet appeared to improve serum cortisol concentrations, which resulted in increased plasma protein, albeit at different durations of stress. Puerarin, as well as all three crude isoflavone extracts, significantly increased spleen-somatic index compared to non-supplemented stressed fish, although the crude isoflavone extracts did not appear to improve serum cortisol concentrations. Crude isoflavone extracts also showed overall increases in lysozyme activity compared to non-supplemented stressed fish, although this was not significant. Genistein, puerarin, and red clover showed increased growth rates, feed conversion ratio, and protein efficiency. Overall, pure isolates of isoflavone appear to be more effective in modulating stress, immunity, and growth than the crude isoflavone extracts, although red clover extract showed promises in the ability to modulate the stress response and improve growth and immunity. There are likely substantial interactions between the isoflavones in the crude extracts that cannot be fully understood by measuring the effects of single isoflavones. Regardless, isoflavone supplementation (pure or crude) appeared to generally have an overall positive impact on stressed Nile tilapia, requiring more research to better understand the effects and mechanisms behind these isoflavones.

Improvements in breeding success are needed for conservation of endangered birds such as the New Zealand kakapo. A potential method to stimulate breeding is treatment with exogenous hormones. Hormone treatment is used in captive breeding programmes for endangered mammals but reliable techniques are not available for birds. Gonadotropin releasing hormone (GnRH), the principal hormone controlling reproduction, has been used to induce ovarian growth and ovulation in seasonally anoestrous mammals. The goal of the research in this thesis was to determine the potential of GnRH for hormone treatment in birds. The Japanese quail (Coturnix coturnix japonica) was used in the current research. Female quail held outdoors with male quail and with access to nesting materials and nest sites showed clear seasonal patterns in the width of the cloacal opening (indicative of oviduct development) and FSH concentrations, whilst LH concentrations were low during winter and increased during spring and summer. Prolactin concentrations were elevated in birds incubating eggs in nests and birds caring for young. Photoperiodically induced gonadal growth and regression were described in detail for male and female quail under controlled conditions. Testicular and ovarian growth was preceded by increased LH and FSH concentrations and accompanied by increased gonadal steroid concentrations. Administration of various types of GnRH stimulated luteinising hormone (LH) secretion in sexually regressed female Japanese quail. LH responses to cGnRH-II were greater than those to cGnRH-I. Low doses of buserelin stimulated similar LH responses to cGnRH-II, whilst high doses of buserelin and D-Lys6Trp7Tyr8-GnRH induced sustained LH secretion. Single daily injections of various doses of cGnRH-II, buserelin or D-Lys6Trp7Tyr8-GnRH in saline or polyvinylpyrrolidone (PVP) did not induce elevated baseline LH or stimulate ovarian growth. Repeated injections of D-Lys6Trp7Tyr8-GnRH did not increase LH concentrations over a short-term period. Continuous infusion of D-Lys6Trp7Tyr8-GnRH by osmotic mini-pump severely blunted the LH response and did not stimulate ovarian growth. Future studies using quail exposed to marginally stimulatory photoperiods will offer the opportunities to determine the effects of GnRH in birds under conditions which mimic photoperiod changes during the breeding season. Further studies on the potential development of a hormone treatment programme will continue to offer a promising future for endangered avian species including the New Zealand kakapo.

With the signing of the Kyoto Protocol, New Zealand must reduce its national greenhouse gas emissions. As New Zealand has a large proportion of its national emissions as methane (~31%), and methane (CH4) has a short atmospheric lifetime, it provides a good target for mitigation strategies. The initial aim of this research was to identify high and low CH4-emitting cattle to assess factors that contribute to low CH4 production. Initial studies using the SF6 tracer technique to estimate CH4 production could not identify consistently high and low CH4 emitters. Research was therefore undertaken to confirm whether this was due to high variation in estimated CH4 yields, and to quantify the within- and between-animal variation in CH4 production when using the SF6 technique. This research showed considerable within- (coefficient of variation, CV = 7-10%) and between-animal (CV = 7-18%) variation in CH4 yield (g CH4/kg DMI) over time when using the SF6 technique. This is larger than the within- (CV = 3%) and between-animal (CV = 10%) variation reported for calorimetry. This led to the recommendation that the SF6 technique not be used in identifying animals for high or low CH4 yield. A power analysis was developed based on the measured variances for the SF6 technique. Results from this analysis provide researchers with important information on the number of animals and measurements per animal required when undertaking CH4 experiments. One of the sources of variation with the SF6 technique is the SF6 release from permeation tubes. Estimated CH4 yield increases by approximately 8.5% when going from a release rate of 3 mg SF6/day to a rate of 5 mg SF6/day. Further, an in vitro study indicated that SF6 release from permeation tubes is approximately 8% lower in rumen fluid than in air. While further research is required to confirm these results, they emphasise the need to allow time for the release rate to stabilise in the rumen for 4-5 days prior to undertaking measurements. It also led to the recommendation that release rates used in experiments should be within a narrow range, and balanced across experimental treatments.

To study the effects of feeding and diet on postnatal development of the small intestine in newborn piglets during the time 0 - 24 hours after birth, three studies were conducted: 1. Unsuckled newborn piglets were fed from a bottle with colostrum or milk from either sows or cows, infant formula, or water. After 24 hours intestinal development was compared with that in piglets at birth and others naturally suckled. Sow colostrum caused greater increases in weight and length of the small intestine than did any of the other diets. The increases were due to mucosal cell swelling caused by cellular protein accumulation, hyperplasia and, in the duodenum, hypertrophy. Feeding sow colostrum increased mucosal lactase activity. Cow colostrum caused decreases in mucosal RNA levels. Increases in the DNA content of the intestinal mucosa occurred in all groups, including the water fed group. Colostrum feeding also enhanced pancreatic growth and feeding infant formula increased liver weight. 2. The effects of enteral feeding on small intestinal development were investigated by feeding nutrient solution to unsuckled newborn piglets by orogastric tube or parenterally. Both groups after 24 hours had greater intestinal development than did the piglets at birth. The development was most pronounced in the duodenum and lower ileum. Apart from a greater small intestinal length in the orogastrically fed piglets there were no significant differences between the orogastrically and parenterally fed groups. 3. To investigate the effects of sucking per se on small intestinal development, groups of unsuckled piglets were fed for 24 hours with either sow colostrum or infant formula by orogastric tube or being allowed to suck from a bottle. Sucking did not affect intestinal development whereas colostrum, regardless of how it was fed, had significantly greater effects on intestinal development than did infant formula. For the colostrum fed piglets the intestinal length, tissue weight, circumference, wall thickness, villous height and width, RNA content, protein:DNA ratio and RNA:DNA ratio were all significantly greater than for those fed infant formula. In the duodenum the estimated cell migration rate was faster and mucosal cell replacement time was shorter than in other parts of the small intestine, regardless of the diet fed. The greater villous height in the piglets fed sow colostrum was most likely due to the combined effects of cellular swelling and an increase in the number of villous cells. These results indicate that (a) sow colostrum causes cellular swelling related to colostral protein accumulation, cell hyperplasia and, in the duodenum, hypertrophy, (b) there is a basal rate of mucosal cell division which contributes to mucosal growth regardless of diet and method of feeding, (c) the duodenum exhibits a greater growth and sensitivity to the trophic effects of colostrum compared to other parts of the small intestine, (d) feeding cow colostrum to newborn piglets causes a pronounced decrease in mucosal RNA content and (e) diets affect postnatal development of the small intestine whereas the route or method of feeding has no significant effects on small intestinal development in piglets during the first 24 hours after birth.

As ectothermic marine megafauna, sea turtle physiology and ecology are tightly intertwined with temperature, seasonality, and oceanography. Identifying how turtles respond when exposed to cold water, how they adapt to cold environments when they need to explore cold environments in order to forage, and what foraging resources are exploited by sea turtles are all components central to their conservation. Cold-stunning is a well-documented phenomenon that occurs when water induced decreases in sea turtle body temperature cause turtles to become immobilized and wash ashore. While most cold-stunned turtles are rescued and rehabilitated, we do not know whether cold-stunning is an acute transient occurrence, or a symptom of a bigger environmental problem. Further, while in some environments avoiding cold water is preferential, in other habitats, sea turtles need to inhabit cold environments in order to forage. Along the Eastern Pacific Rim, discrete upwelling locations are characterized by high primary productivity and unusually cold water. In these environments, avoidance is not possible and sea turtles require physiological adaptions to mitigate body temperature decreases in cold water. Little is known about how turtles handle upwelling environments, despite the fact that sea turtles remain in these habitats regardless of water temperature fluctuations. Because upwelling habitats provide increased nutrient presence, and sea turtles are opportunistic foragers, quantification of diet composition will further our understanding of why sea turtles remain in cold water environments year-round. Diet composition in multiple populations of cohabitating sea turtles revealed partitioning that results in reduced inter-specific competition. Further, flexibility in diets provides a wide range of ecosystem services central to habitat resiliency. Therefore, conservation of endangered sea turtles requires complete ecosystem conservation, and complete understanding of the interconnectivity of sea turtles and their environments is crucial.

Preterm birth is the leading cause of newborn mortality, with 15 million babies born premature worldwide every year. Children that do survive early delivery are more likely to develop cognitive abnormalities, motor deficits, heart disease, cerebral palsy, and more. While little is known about the pathophysiology of preterm birth, several pregnancy-related complications are related to preterm birth, namely cervical insufficiency and preeclampsia. In the former, premature cervical remodeling and softening can result in the shortening of the cervix, increasing a woman’s risk of preterm birth; this condition is called cervical insufficiency (CI), which is the inability of the cervix to remain closed as a result of weakened tissues. CI is currently measured by a one-dimensional sonographic cervical length, where < 25 mm indicates shortening. Preeclampsia is a disorder that can be explained through the Page kidney phenomenon: compression of the left renal vein (LRV) causes renal venous outflow obstruction, leading to elevated intrarenal pressure and hypertension. The supine pressor test (SPT) is a diagnostic tool for preeclampsia where a positive test is defined by an increase of 20 mmHg in diastolic blood pressure (BP) when shifting from the left lateral recumbent to the supine position. Due to the intense risk of morbidity and mortality for both the mother and the fetus, the need to monitor BP changes is critical. Currently, there is an unmet clinical need to characterize the hemodynamic and geometric properties of the female reproductive organs throughout gestation. Utilizing ultrasound imaging can increase our knowledge about the 3D anatomy and systemic changes during pregnancy, unravel risk factors, establish preventative methods, and standardize treatment plans. In this thesis research, we developed a murine model to 1) examine the pathophysiology of renal vein stenosis, and 2) investigate the effects of stenosis on various cervical dimensions. Renal vein stenosis was found to greatly impact blood flow velocities, as well as cervical width (p<0.05). LRV and cervical area and height also trend towards significance, and there is negative damage to the left kidney and placentae within the stenosed cohort. We also conducted a human study that showed reduced change in postural BP in patients with higher body mass index (BMI). Systolic and diastolic BP in the supine position was significantly greater than in the lateral position for all BMIs with a baseline increase in BP of approximately 9-14 mmHg. These findings suggest that therapeutic positioning and close monitoring of BP could mitigate the risk of developing related disorders in pregnancy.

Events around conception such as maternal undernutrition and twinning may have effects on offspring physiology and disease risk in adulthood. Periconceptional undernutrition alters offspring physiology and adult pathology without affecting birth size, while twinning affects birth size and physiology but with inconsistent effects on adult pathology. We investigated the effects of these two periconceptional events and their interaction on maternal cardiovascular adaptation to pregnancy and fetal growth, physiology and endocrinology in late gestation in sheep. Pre and/or postconception undernutrition resulted in increased uterine blood flow in late gestation, but no change in maternal blood volume. Preconception undernutrition alone resulted in a relatively large placenta with a small, slow-growing fetus in late gestation. In contrast, postconception undernutrition alone resulted in a fetus with rapid late-gestation growth that was maintained through a maternal fast. Fetuses of ewes undernourished throughout both periods were similar in growth rate and size to controls. Maternal fasting also demonstrated that plasma levels of C-type natriuretic peptide are acutely and independently regulated by nutrient supply in mother and fetus. Fetuses of ewes undernourished both pre- and postconception had increased glucose disposal following a glucose challenge. Hypothalamic-pituitary-adrenal axis tests in these fetuses showed decreased pituitary adrenocorticotropin hormone response to direct stimulation but increased adrenal response to decreased cortisol negative feedback. Twin fetuses grew more slowly in late gestation than singletons. Twins also had a smaller insulin response to arginine and a greater insulin response to glucose, but periconceptional undernutrition abolished this difference. Twins had suppressed baseline hypothalamic-pituitary-adrenal axis function and decreased adrenal sensitivity compared to singletons, but increased fetal pituitary adrenocorticotropin hormone response to direct stimulation and decreased cortisol negative feedback. These studies suggest that firstly, fetal size is a poor reflection of fetal growth trajectory, physiology and endocrinology. Secondly, pre- and postconception undernutrition affect late-gestation fetal growth in different ways, while undernutrition in both periods alters fetal endocrine status in late gestation. Thirdly, the biology of twin fetal development is fundamentally different from that of singletons, which may explain the inconsistency of the relationship between birth weight and adult disease risk in twins.
Auckland Medical Research Foundation, Health Research Council of New Zealand