Effects Of Dietary Protein Level On Growth And Reproductive Performance Of Shanbei White Cashmere Goat Bucks

This study was conducted to explore the effects of dietary protein level on the growth performance, serum biochemical parameters and semen quality of Shanbei White Cashmere goat bucks by using feeding experiments and digestion experiments. According to the experiments, the protein requirements of goat bucks has been determined, which laid the foundations for establishing the nutrients requirements model of Cashmere goats in China, thereby providing the theoretical and application basis for enhancing the productive performance and feed utilization efficiency of domestic Cashmere goat. Exp.1 Effects of dietary protein level on body weight and nutrients degradation of Shanbei White Cashmere goat bucksA total of 12 bucks were divided into 4 groups with 3 bucks in each group. The bucks in different groups were feed on diets with 5.10%,7.11%,8.07%,9.35% crude protein according to 70%, 85%, 100%, 115% of protein recommendation of NRC, respectively. The whole study had three period: pre-breeding period(50 d), breeding period(40 d; 20 d for the ejaculate frequency of twice every five days, and 20 d for four times every five days), recovering period(30 d). Digestion experiments were used to determine the nutrients degradation in each period. The results showed that:(1) there had significant differences among treats in ADG, which increased with the increasing dietary protein level(P<0.05);(2) significant differences existed among treats in CP digestibility, which increased with the increasing dietary protein level(P<0.05), while no differences had been observed among treats in DM, CF, NDF and ADF digestibility(P>0.05).Exp.2 Effects of dietary protein level on serum biochemical parameters, reproductive hormones and semen quality of Shanbei White Cashmere goat bucksA total of 12 bucks were divided into 4 groups with 3 bucks in each group. The bucks in different groups were feed on diets with 5.10%,7.11%,8.07%,9.35% crude protein according to 70%, 85%, 100%, 115% of protein recommendation of NRC, respectively. The whole study had three period: pre-breeding period(50 d), breeding period(40 d; 20 d for the ejaculate frequency of twice every five days, and 20 d for four times every five days), recovering period(30 d). Semen was collected using artificial vagina and blood was collected from jugular vein. The results showed that:(1) dietary protein level had no significant influences on GPT, GOT, TP, ALB, GLO, A/G and glucose in serum of bucks(P>0.05), while BUN was increased with the increasing dietary protein level(P<0.05);(2) no significant differences were seen among treats in FSH, LH and testosterone of bucks(P>0.05), whereas breeding period significantly influenced the FSH and testosterone(P<0.05);(3) dietary protein level had significant influences on ejaculate volume(EV), sperm density(SD) and effective sperm count(ESC), which were raised with the increasing dietary protein level(P<0.05). Although dietary protein level failed to affect the sperm motility, it showed an uptrend effect on sperm motility(P>0.05). Exp3. Study on the protein requirements of Shanbei White Cashmere goat bucksTo study the protein requirements of Shanbei White Cashmere goat bucks in different breeding periods, regression and factorial methods were applied. Also the results of experiment were taken into consideration. The regression equations of crude protein requirements and degradable crude protein requirements were showed below:Pre-breeding period:CPI 5.095 W.0.844ADG(R2=0.997,P=0.001)DCPI 2.296 W.0.772ADG(R2=0.978,P=0.007)Breeding period:CPI 5.095 W.44.20n(n, ejaculate frequency)DCPI 2.296 W.38.15 n(n, ejaculate frequency)Recovery period:CPI 4.312 W.0.841ADG(R2=0.977,P=0.008)DCPI 2.215 W.0.803ADG(R2=0.963,P=0.012)Based on the above experiments, there were significant influences of dietary protein level on ADG, CP digestibility, BUN, EV, SD, ESC of bucks, which all increased with the dietary protein level.