Auswahl der wissenschaftlichen Literatur zum Thema „Food utilization efficiencies“

Homalodisca coagulata (Say) is a xylem feeding leafhopper that is the principal vector of many economically-important diseases resulting from infection by Xylella fastidiosa (i.e., plum leaf scald, phony peach disease, Pierce's disease). Xylem fluid consists primarily of dilute concentrations of amino acids, organic acids and inorganic ions, and thus provides less nitrogen and carbon for herbivorous insects than any other plant tissue. Despite these nutritional constraints, H. coagulata is highly polyphagous. To assess how H. coagulata subsists on this dilute food source we examined host utilization by different instars on Lagerstroemia indica L. (preferred adult food source) and Euonymus japonica Thumb. (preferred ovipositional site). Different instars survived and utilized nutrients at varying rates on the two hosts. Second instar nymphs survived at higher rates on E. japonica and utilized nitrogen more efficiently than on L. indica, yet assimilated nitrogen was less as a result of lower feeding rates. Adults on L. indica were more successful than those on E. japonica, used carbon more efficiently, and assimilated higher quantities of both carbon and nitrogen. Efficiencies of nutrient utilization were high for E. coagulata compared to other types of insects with assimilation efficiencies of specific compounds often exceeding 90%.

The influence of season and management system on the productivity of Friesian cows in a Mediterranean climate was assessed. Intakes of food and water and milk yields were measured in 154 cows over 2·5 years while intensively managed in yards giving access to shelter (free stalls) or that were fully exposed to solar radiation (open lots). Food quality was also monitored to permit estimates of the efficiency of utilization of metabolizable energy for milk production over fortnightly periods.The highest milk yields and energetic efficiencies were recorded during spring. Energy intakes were highest but energetic efficiencies were lowest during winter. Cows consumed the least food during summer and autumn and drank the most water during summer. The only significant effect of management system was for water intake, which was higher in the open lots than in the free stalls. There was evidence of heat stress in summer and cold stress in winter, but there appeared to be little benefit with milk yields through the provision of shelter.

The studies on energetics are concerned mainly with evaluating the energy flow and, therefore, are related to the incorporation of energy into new protoplasm in addition to estimates of maintenance of energy. The work with Criotettix grandis Hanc. has still not been worked upon therefore Quantitative estimation of consumption, assimilation, tissue growth and food utilization efficiencies of the phytophagous insect was calculated and worked out.

ABSTRACTThis study was designed to examine the influence of pre-wilting and season of harvesting of silage on milk production and food utilization by dairy cattle and also the response to protein and fat concentration of the supplement given with silage. Twenty-four lactating British Friesian cows were used i n a four-period, partially balanced, change-over design experiment to evaluate 12 treatments consisting of three silage types (spring harvest unwilted (lUnW), autumn harvest unwilted (3UnW) and autumn harvest wilted (3W), each offered in addition to supplements containing both two crude protein levels (160 and 210 g/kg fresh weight) and two levels of inclusion of a fat supplement (0 and 100 g/kg fresh weight) in a 3 × 2 × 2 factorial arrangement. All supplements were offered at the same rate of 6·8 kg/day. Total diet digestibility and food utilization studies were carried out on all animals at the end of the third and fourth experimental periods.The wilted silage (3W) had a higher digestibility than the unwilted (3UnW) material and animals offered 3W silage consumed proportionately 0·18 more silage DM and produced 1·6 MJ/day more milk energy output than those offered 3UnW. The total ration digesibility and food utilization data showed the animals given the 3W silage consumed 13·5 MJ more metabolizable energy (ME) per day than those offered the 3UnW silage and were less efficient at converting the ME available for production into milk energy output than those given the 3UnW silage (efficiencies were 0·58 and 0·53 for 3UnW and 3W silages respectively).There were no differences between the digestibilities of the spring (lUnW) and autumn (3UnW) silages with the concentrations of digestible organic matter in the dry matter (DM) being 650 and 648 g/kg respectively. However, animals offered lUnW silage consumed proportionately 0·12 more DM and produced 1·05 kg/day more fat-corrected milk than those given 3UnW silage. The food utilization data indicated that this milk production difference could be accounted for by the higher ME intake on lUnW and that the efficiencies of conversion of ME available for production to milk energy output were similar with both seasons of harvests (efficiencies were 0·57 and 0·58 for lUnW and 3UnW respectively).Increasing the crude protein concentration of the supplement from 160 to 210 g/kg increased silage DM intake, milk yield and milk energy output by 0·2 kg, 0·66 kg and 1·9 MJ/day respectively with the response being greatest with lUnW and least with 3UnW silage. Increasing the fat concentration of the supplement depressed silage DM intake but increased milk yield by 0·53 kg/day.The effects of the treatments on total diet digestibility, energy and nitrogen utilization, and the volatile fatty acid concentrations of rumen fluid are also given.