Effects of a high-protein, low-energy diet in finishing lambs: 2. Weight change, organ mass, body composition, carcass traits, fatty acid composition of lean and adipose tissue, and taste panel evaluation

An experiment was conducted to evaluate the effects of a high protein – low energy diet on body composition of feedlot lambs The objective was to assess the capability of such a diet to reduce body fat while preserving lean body mass. Three dietary regimens were compared: a typical feedlot diet (CON), barley straw at libitum (STR), and barley straw supplemented with fish meal (SFM). The latter two diets caused an energy deficit in the experimental animals. Significant treatment effects on mass of metabolic organs, body composition, and carcass data were observed. Conventional analysis of sensory data and fatty acid profiles of adipose and muscle tissue identified few significant dietary effects, yet discriminant analysis clearly separated all treatment groups. It was concluded that protein supplementation of ruminants in the catabolic state does not conserve protein mass. Given the high cost of protein supplementation, the post hoc modification of body composition of feedlot lambs is not a viable option. It is suggested that the production of feedlot lambs with a desirable degree of fatness should employ a feeding strategy dynamically adapted to the changes in protein – energy balance required by the growing ruminant.     

Interaction of parasitism and nutrition and their effects on production and clinical parameters in goats.

Weaned wether goats (n = 144) approximately 6 months of age were placed in a 2 x 3 factorial design experiment for 5 months to test the main effects and interaction of two levels of nutrition (growth + maintenance, NUT1; twice growth + maintenance, NUT2) and three levels of Haemonchus contortus burden (0, 500 and 2000 larvae administered every 2 weeks: W0, W500 W2000, respectively) on weight, feed intake, level of infection and packed cell volume (PCV). The rationale for the experimental design was based on the lack of information concerning the interaction between nutritional status and worm burden. Results indicated significant effects of worm burden levels on PCV, faecal egg contents (eggs per gram of feces (EPG)), actual worm numbers, feed intake and efficiency of feed utilization. Nutrition x worm burden interactions were also significant for PCV and EPG. However, the differences detected for PCV and actual worm numbers did not translate into large or consistent differences in body weight. Goats on NUT2, after an initial period, showed little difference in body weight, irrespective of worm burden. Within the NUT1 level, W0 kids weighed more than W500 or W2000 kids throughout the study. Although not statistically significant, this constitutes a trend towards an interaction between nutrition and worm burden. In both nutrition levels, there were no body weight differences between W500 and W2000 until the last 14 days. Feed intake was depressed in the first 3 months of the experiment for infected animals, but was subsequently followed by a compensatory reaction. Lower establishment rates, based on actual worm counts, were observed for the higher infection level, but in both infection levels establishment rates tended to decrease with time. Nutrition was found to be more important to counteract the consequences of a parasitic infection than to counteract the establishment of that same infection.     

Serologic response of Babesia equi-infected horses as measured by complement-fixation and indirect fluorescent antibody tests

Both the complement-fixation test (CFT) and the indirect fluorescent antibody test (IFAT) were conducted on weekly serum samples from nine Arab geldings for 28 days before and 256 days after their exposure to Babesia equi of European origin. On an average the IFAT became positive 8 days before the CFT and showed higher relative serum titer increases. Both test procedures successfully detected infection and neither showed an appreciable drop in titer during this time frame, with the exception of the CFT, which showed a transient drop immediately following treatment with imidocarb. A test conducted 540 days after infection showed four of the eight surviving, and presumably infected, horses to be negative on CFT, where as all eight were still positive on IFAT. Comparisons made with the IFAT, on horse sera from B. equi infection of both European and North American origin, utilizing homologous and heterologous antigens, showed significantly higher titers with homologous antigens.     

Comparative costs of programmes to conserve chicken genetic variation based on maintaining living populations or storing cryopreserved material

1. There have been substantial losses of chicken lines kept for research in recent years and the objective of this research was to critically review alternative methods of preserving genetic resources.

2. The costs of programmes using living populations, semen cryopreservation and reconstitution, and ovary and semen cryopreservation and reconstitution were evaluated over 20 years using biological parameters of cryopreservation and population reconstitution that were derived from the literature.

3. Keeping live populations was most cost effective for periods of up to three years, but keeping live populations is increasingly difficult to justify with longer periods and any research population that will not be used within five years should be cryoconserved and in situ maintenance discontinued.

4. The rapid reconstitution possible using ovaries and semen would allow the inclusion of cryopreserved material in a short-term research project with the cost of recovery included in the budget. The low cost of cryoconservation suggests that all avian material should be conserved and reconstituted when needed for research.