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The aim of this study was to evaluate the effects of vaccination against gonadotropin-releasing factor (GnRF) on testicular development, testosterone secretion, and physical activity in pubertal bulls. The experiment was performed using 44 bulls aged between 6 and 7 mo. Twenty-three animals were vaccinated twice 4 wk apart with 1 mL of Bopriva (Pfizer, Animal Health, Parkville, Australia) and 21 bulls served as matched controls. Serum GnRF antibody titer and testosterone concentration as well as body weight and scrotal circumference were determined in all bulls for 24 wk from the first vaccination. In addition, physical activity was analyzed in 11 vaccinated and in 10 control animals using the ALPRO DeLaval activity meter system (DeLaval AG, Sursee, Switzerland). The results show that vaccination significantly (P < 0.05) influenced all parameters evaluated except body weight. Antibody titers to GnRF began to rise 2 wk after the first vaccination and reached peak values 2 wk after the second injection. Significant group differences in anti-GnRF titer were present for 22 wk following the first vaccination. Testosterone concentrations were significantly lower between weeks 6 to 24 after first vaccination in bulls with Bopriva compared with control animals. In vaccinated bulls testicular development was impaired after the second injection and scrotal circumference was significantly smaller between weeks 8 to 24 after first vaccination. Physical activity of vaccinated bulls was reduced after the booster injection with significant group differences for a continuous period of 106 days. In conclusion, vaccination against GnRF with Bopriva in pubertal bulls decreased testosterone levels in peripheral blood, testicular development, and physical activity but did not affect weight gain. AbstractThe aim of this study was to evaluate the effects of vaccination against gonadotropinreleasing factor (GnRF) on testicular development, testosterone secretion and physical activity in pubertal bulls. The experiment was performed using 44 bulls aged between 6 and 7 months. Twenty-three animals were vaccinated twice 4 weeks apart with 1 mL of Bopriva ® (Pfizer Animal Health, Australia) and 21 bulls served as matched controls. Serum GnRF antibody titer and testosterone concentration as well as body weight and scrotal circumference were determined in all bulls for 24 weeks from the first vaccination. In addition, physical activity was analyzed in 11 vaccinated and in 10 control animals using the ALPRO  DeLaval activity meter system (DeLaval AG, Sursee, Switzerland). The results show that vaccination significantly (P < 0.05) influenced all parameters evaluated except body weight. Antibody 2 titers to GnRF began to rise 2 weeks after the first vaccination and reached peak values 2 weeks after the second injection. Significant group differences in anti-GnRF titer were present for 22 weeks following the first vaccination. Testosterone concentrations were significantly lower between weeks 6 to 24 after first vaccination in bulls w...

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Faecal stable isotope compositions reflect wildlife diets, if digestive processes along the gastrointestinal tract (GIT) do not alter diet-faeces isotopic relationships in an unpredictable way. We investigated 13 C and 15 N compositions of digesta along the ruminant GIT, using Saanen dairy goats kept on pure grass hay or browse for >20 days. Isotopic changes occurred in the ventral rumen, and in the small intestine, where digesta had significantly higher δ 13 C and δ 15 N (associated with lower C or higher N content, respectively) values relative to other GIT sites. However, effects on isotope fractionation were small (∼1.0‰ for δ 13 C and∼2.0‰ for δ 15 N), and were reversed in the hindgut such that faecal isotope compositions did not differ from the foregut. No other substantial isotopic changes occurred across GIT sites, despite the morphophysiological complexity of the ruminant GIT. We found similarly small differences across GIT components of rheem gazelles (Gazella leptoceros) fed a mixture of C 3 lucerne and C 4 grass, although in this case faeces were N abundance is needed. Finally, we note high levels of isotopic variability between individuals fed the same diets, even accounting for the relatively short duration of the experiments, suggesting an important influence of stochasticity on isotope fractionation.

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