Academic literature on the topic 'Sow lactation oestrus'

Research in any area of animal production can provide the opportunity to change how the system operates and is managed. The reliance on having to wean lactating sows to re-mate them has limited the commercial options for sow management. The desire to limit lactation length to maximise the litters per sow per year concurrently creates major challenges for such-aged piglets weaned abruptly. These issues are discussed in the review. This management system also fails to recognise that sows have the potential to spontaneously ovulate in lactation even when housed in farrowing crates. Inhibition of luteinising hormone release is the basis of lactational anoestrus with the suckling stimulus providing the strongest afferent signal to this inhibitory system. Any management strategy that reduces this inhibition has the potential to trigger lactational oestrus. In this review, group housing of sows, boar exposure and intermittent suckling are identified as strong stimuli that can promote lactational oestrus. Removing the need to wean sows to mate them offers further opportunities to change the way lactating sows are managed. One option is a two-stage lactation system in which the sows are housed in farrowing crates for the first 10–14 days and then moved to group accommodation for the remainder of lactation. This system provides welfare benefits for the litter in the early stage of lactation and then the benefits of less confinement for the sows in later lactation. Group lactation would also lend itself to the implementation of stimuli to assist the mating of sows in lactation, such as piglet separation and/or boar exposure. It also accommodates the mating of sows that spontaneously ovulate in lactation. Removing the need to wean sows to re-mate them provides the opportunity to increase weaning age and implement a gradual weaning, helping to attenuate the post-weaning growth check and potentially limiting antimicrobial use in weaner pigs.

It is generally recognised that the nutritional and metabolic status of the sow during lactation can influence its subsequent reproductive capacity. Thus sows which mobilise large quantities of body weight during lactation have extended weaning to oestrus intervals and reduced litter sizes. However, it is not known how nutrition during lactation may influence metabolic efficiency in the post-weaning period, especially in relation to the accumulation of body reserves. The present experiment was therefore designed to investigate the effect of feeding level during lactation on nutrient partitioning and metabolic efficiency in the weaned sow.

AbstractOne of the more promising techniques for the improvement of sow productivity has been the use of partial weaning or the separation of the sow and litter for periods of between 3 to 12 h/day towards the end of lactation. The purpose of the present study was to examine changes in steroid hormone concentrations, oestrus and fertility responses in lactating sows subjected to altered sucking, boar exposure and gonadotropins in mid lactation and at weaning. Thirty-two crossbred sows were allocated at random to one of four experimental treatments. Treatment 1 sows (no. = 8) were separated from their respective litters for 3 h/day from 12 days post partum through until weaning which was carried out at 21 days post partum. Treatment 1 sows were also given in-pen boar exposure for 1 h/day between day 12 post partum and weaning. Treatment 2 sows (no. = 8) were given the same protocol of litter separation (LS) and boar exposure (BE) as in treatment 1 and they were also given a combination of gonadotropins (Gn) on day 17 of lactation. Treatment 3 sows (no. = 8) were given LS + BE as above and the sows were injected with Gn on the day of weaning. Treatment 4 sows were controls given no LS, BE or Gn (no. = 8). During lactation, treatment 1 sows exhibited significantly (P < 0·05) reduced progesterone concentrations compared with treatment 2 sows. There were no other significant effects of treatment for any of the periods considered. The separation of sows from their piglets with or without gonadotropic treatment did not result in lactational oestrus in any treated sows. No significant treatment differences were found in the subsequent litter size (piglets born alive or total number of piglets). In conclusion, the present results have demonstrated no significant effects of LS, BE and Gn treatment during lactation on sow and litter performance. This was associated with low levels of peripheral plasma progesterone in all lactating sows.

The occurrence of ovulation in the sow after parturition is usually inhibited for the duration of suckling. A system of management in which lactating sows are mated and conceive, therefore routinely commencing a successful pregnancy concurrent with lactation, would obviate the need for early weaning of piglets and promote adoption of economic systems incorporating more extensive lactation housing. Previous studies have shown that first parity sows rarely show ovulation during lactation when group-housed in multisuckling systems with multiparous sows, and suggested that reduced food intake through social competition and/or higher suckling intensity were responsible for this (Hulten, 1997). The object of this experiment was to investigate, in a more controlled way, the factors contributing to this parity effect by removing the possibility of social interactions between primiparous and multiparous sows, and investigating possible dietary influences within parity.

The effects of feed restriction (60% of anticipated feed intake; Restrict; n = 60) during the last week of a 21-day lactation in primiparous sows compared with feeding at 90% of anticipated feed intake (Control; n = 60) on sow metabolic state, litter growth and sow reproductive performance after weaning were compared. Metabolisable energy (ME) derived from feed was lower, ME derived from body tissues was higher and litter growth rate was reduced (all P < 0.05) in Restrict sows during the last week of lactation. Treatment did not affect weaning-to-oestrus interval, pregnancy rate, ovulation rate, embryonic survival or the number of live embryos (P > 0.05) at Day 30 of gestation: However, embryo weight was greater (P < 0.05) in Control than in Restrict sows (1.55 ± 0.04 vs 1.44 ± 0.04 g, respectively). These data suggest the biology of the commercial sow has changed and reproductive performance of contemporary primiparous sows is increasingly resistant to the negative effects of lactational catabolism. Overall, catabolism negatively affected litter weaning weight and embryonic development of the next litter, but the extent to which individual sows used tissue mobilisation to support these litter outcomes was highly variable.

AbstractThe effects of different energy sources in the lactation diet on sow and piglet performance were assessed in association with effects on the metabolic state of the sow around peak lactation. Either maize starch (S) or soya-bean oil (F) was added to a basal diet to provide 0·34 of total digestible energy (DE) intake, such that the experimental diets provided the same daily intakes of DE and crude protein. Twenty-four multiparous sows were allocated between two groups at farrowing, each given one of the two dietary treatments for a lactation period of 28 days. Sow weight and backfat (P2) as well as individual piglet weights were measured on a weekly basis. Litter sizes were standardized to 10 piglets. Milk samples were collected from sows on days 8, 12, 17, 21 and 25 of lactation to measure milk composition and prolactin concentrations. Blood samples were taken via an ear vein catheter from a subsample (7 S, 6 F) of sows on day 14 of lactation; two pre- and seven post-feeding samples were taken at 60-min intervals to measure plasma prolactin, insulin, glycerol, triglyceride, non-esterified fatty acid, urea, b-hydroxybutyrate and glucose concentrations. There was no effect of energy source on sow weight or P2 loss or on subsequent weaning-to-oestrus interval. Sows offered starch weaned more piglets than sows offered soya-bean oil (9·4 v. 8·4, P < 0·05). Litter weight gains were higher for S than F sows in week 3 of lactation (2·2 v. 1·7 kg/day, P < 0·05), irrespective of litter size. Significantly increased plasma urea and b-hydroxybutyrate concentrations and lower post-prandial increases in plasma glucose and insulin concentrations were observed in F sows around peak lactation. Neither milk nor plasma prolactin concentrations were significantly affected by dietary treatments. The metabolic indices indicated that the F diet was more limiting in dietary glucose availability, which was associated with impaired milk yield as indicated by poorer litter performance. In conclusion, this study suggests that starch is superior to fat as an energy source in sow lactation diets, particularly in the later stages of lactation.

Confinement of sows in farrowing crates and early weaning of piglets are two major areas of concern in relation to animal welfare in intensive pig production systems. In this project, two alternative lactation systems in which these potential stressors are absent or reduced were evaluated.36 sows and litters were used in an experiment to evaluate, from weekly performance records and observations of behaviour, two alternative strategies for housing and management during lactation in comparison with a conventional current system: (1)Family system (F): Sows were housed throughout in groups of four with voluntary access farrowing pens. Piglets remained with the sows for 12 weeks and a boar was introduced after 3 weeks to induce oestrus.(2)Multisuckling system (M): Sows farrowed in individual crates but were grouped in fours in straw pens after 2 weeks. Piglets remained with the sows for 12 weeks and a boar was introduced after 3 weeks.(3)Conventional commercial system (C). Sows remained in part-slatted, unbedded farrowing crates throughout a four week lactation. Piglets weaned into flat decks and transfered after four weeks into fully slatted grower pens.

The experiment was performed on a large indoor herd during a hot season period in Alföld, Hungary. The post-weaning sows (F1 and F2 of Large White × Landrace mated to Duroc boars (mean parity 3.4 +/-0.7 SD; mean body condition 3.01 +/-0.3 SD, previous lactation length of 28.3 +/-1.5 d) were divided into four groups of similar body condition, lactation length and parity and were treated as follows: Group 1: sows (n = 420) were injected subcutaneously with 400 I.U. of Gonadotropinum sericum (pregnant mare serum gonadotropin, PMSG [eCG]) and 200 I.U. of Gonadotropinum chorionicum (human choriongonadotropin, HCG [hCG]) one day after weaning. Group 2: sows (n = 405) received subcutaneously 4 ml of saline injection one day after weaning. Group 3: sows (n = 425), purposely chosen from among animals that did not show heat within 7 days after weaning, were treated on day 7 post-weaning with PMSG and HCG as the animals in group 1. Group 4: sows (n = 415) purposely chosen from among animals that did not show heat within 7 days after weaning, were treated on day 7 post-weaning as group 2. Sows expressing oestrus, sows ovulating after treatment, treatment to oestrus intervals and follicular sizes were evaluated. The number of sows expressing oestrus, sows ovulating, and treatment to oestrus intervals differed between the groups (group 1 vs. 2: P < 0.05, group 3 vs. 4: P < 0.01). The sows treated with PMSG and HCG on day 7 post-weaning (group 3) had smaller (P < 0.05) follicular diameters compared to the sows that were treated one day after weaning. Group 4 sows had a smaller follicular diameter (3.6 +/- 0.6 mm) compared to group 1 (P < 0.001) and 3 (P < 0.01). The present results show that the gonadotropin treatment one day after weaning or in the case of anoestrus 7 days after weaning overrides the negative effects of the hot summer season and effectively prevents seasonal infertility of the breeding sow.

In lactation, sows are typically anoestrus, with ovulation occurring three to seven days after weaning at approximately 24 days post-partum. Increasing piglet age to greater than 28 days improves piglet performance and welfare; however, it also results in reduced sow farrowing frequencies, making the commercial adoption of increasing piglet weaning age unsustainable. Stimulating a sow to ovulate in lactation represents a solution as it enables lactation length to be increased whilst maintaining reproductive efficiencies. The aims of the research reported in this thesis were to investigate mechanisms to reliably stimulate a lactation oestrus in multiparous and primiparous sows. Secondly, to determine the effect of these strategies on piglet growth, subsequent pregnancy rate, farrowing rate and litter size. The mechanisms investigated were focused on: reducing the suckling input to the sow through split weaning or low-confinement alternative lactation housing; and fence, or full physical, boar exposure. The importance of a reduced suckling input was demonstrated in Chapter Two. The proportion of sows expressing a lactation oestrus increased as the number of piglets weaned on day 18 of lactation increased from zero, three, five to seven. Additionally, early weaning did not compromise growth of the split weaned piglets, with both early and late weaned piglets experiencing similar body weights by day 40 of age. Chapter Three evaluated the effect of full physical boar exposure commencing at day 10, 14 or 18 postpartum on the incidence of lactation oestrus in primiparous and multiparous sows. A high proportion of multiparous sows expressed a lactation oestrus in response to boar exposure compared to first parity sows; however, the summer months impacted this expression. No benefits of commencing boar exposure before day 18 post-partum on lactation oestrus expression were observed. Chapter Four coupled full physical boar exposure with split weaning of piglets at day 18 post-partum within a commercial piggery. Boar exposure was effective at stimulating a lactation oestrus in multiparous sows whereas primiparous sows require, in addition to boar exposure, a reduction in suckled litter size. A high incidence (24%) of lactating multiparous sows that received no stimulation spontaneously ovulated before weaning resulting in a prolonged weaning to oestrus interval. These results suggest that for the modern sow, weaning is not necessary for ovulation. Lastly, Chapter Five demonstrated that low confinement lactation housing from seven days post-partum, in combination with fence line boar exposure, was not sufficient to stimulate a lactation oestrus. Overall, split weaning to seven piglets in conjunction with physical boar exposure resulted in the highest proportion of lactation oestrus expression with this response greater in multiparous sows than primiparous sows. Season affected the proportion of lactation oestrus expression, and this requires further investigation. Furthermore, the incidence of spontaneous ovulation during lactation suggests that the inhibition of LH release during lactation is less severe in modern genotypes. In conclusion, this thesis has demonstrated that boar exposure effectively stimulates lactation oestrus with a further increase observed when a distinct reduction in the suckling stimulus has occurred, particularly in the multiparous sow.
Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Animal and Veterinary Sciences, 2015.