DDGS和酵母培养物对奶牛生产性能和乳成分的影响

选择16头泌乳天数为127±52d经产荷斯坦泌乳牛用于评价酵母培养物(达农威益康XP)和玉米酒糟及其可溶物(DDGS)在试验日粮中含有限草料纤维数量(草料中的中性洗涤纤维含量为19.3%,干物质基础)之情况下对产奶量和乳成分的影响及其它们之间的互作效应。本次试验采用4重复4×4拉丁方设计,试验时间为4个星期。处理组均按照2×2因子排列而设定,其中:1)日粮中不含酵母培养物和DDGS(对照组);2)日粮中含有20%DDGS,无酵母培养物(DDGS组);3)日粮中含有60g/d的酵母培养物益康XP(XP组);4)日粮中含有20%DDGS和60g/d的益康XP(XP+DDGS组)。本次试验结果表明:各处理组之间对奶牛体重和体况评分无显著的影响。日粮的处理并不影响干物质采食量(DMI),在使用草料纤维含量较低且添加20%DDGS的日粮情况下乳脂率会降低。添加益康XP的确能够提高产奶量及乳蛋白产量,但却不能够完全阻止因DDGS所造成的乳脂率下降的趋势。无论日粮中是否含有DDGS,益康XP都能够提高奶牛的生产性能。     

Suppression of testicular function using two dose rates of a reversible water soluble gonadotrophin releasing hormone (GnRH) vaccine in colts

Objective: To investigate the effect of two dose rates (200 and 400 ng) of a gonadotrophin releasing hormone (GnRH) vaccine on testicular function. Design: A vaccination dose rate experiment. Procedure: Two injections were administered 4 weeks apart to six colts in each treatment group. To maintain immunosuppression until the end of the breeding season, a third injection was given if antibody titres fell below 1000. Results: Effective antibody titres were present for 12 to 27 weeks. Testosterone concentrations decreased from 2.22 to 0.31 nmol/L 6 weeks after primary vaccination. Androstenedione concentrations decreased from 1.78 to 0.28 nmol/L 5 weeks after vaccination. Testosterone and androstenedione concentrations above 0.69 and 0.87 nmol/L were attained 31 to 43 weeks after vaccination. Mean scrotal widths and lengths decreased over 29 weeks from 9.2 cm and 9.7 cm to 6.7 cm and 7.6 cm. At surgical castration these dimensions were 10.1 cm and 11.0 cm. Mean semen characteristics before vaccination and after recovery were: gel-free volume 16.5 and 13.5 mL, sperm concentration 295.5 times 10⁶ 315.6 times 10⁶/mL, total sperm per ejaculate 4041 times 10⁶ 4657 times 10⁶ live normal spermatozoa 32% and 60%. Histologically, the testes showed active spermatogenesis. The mean testicular parenchyma weights for the 200 and 400 mg groups were 129.0 g and 109.8 g. Daily sperm production per testis and per gram of testis for the 200 and 400 mg groups were 3.7 times 10⁸ 2.8 times 10⁶ 2.3 times 10⁸ 2.0 times 10⁶. Conclusions: Both dose rates suppressed testicular function. Data showed that the vaccine effects were reversible. Individual immune response was less varied in the 200 mg group. Further work is necessary to achieve a less variable response in the immunosuppression of testicular function.