| The feeding trials and digestive test were carried out for the studies of energy intake levels on average day gain(ADG), serum biochemical indicators, nutrient digestibility and semen quality of Shanbei white cashmere goat bucks, and determined the energy requirement of bucks in probationary, mating period and recovery period, so as to provide basical parameters for establishing and completing feeding standards of Shanbei white cashmere goats.A total of 12 bucks with an average body weight of(54.95±2.21 kg), good health and similar semen quality were selected and divided into 4 groups according to randomized block design with 3 replicates per group, each replicate included 1 buck. Four diets were formulated by the recommendation of NRC(1981, 2007) at 85%, 100%, 115% and 130%. The trial lasted for 120 d. The trial was divided into three periods: probationary(50 d), mating period(40 d) and recovery period(30 d). The digestive test was carried out by exogenous indicator method with indicator of Cr2O3 in last 10 d in every period. The results showed that:(1) There were an extremely significant effect of different energy intake levels on ADG of bucks in every period(P<0.01); The weight of bucks in group 5.95 MJ/kg and group 7.00 MJ/kg increased firstly then decreased while there were a trend of increasing firstly then decreasing then increasing again in group 8.05 MJ/kg and group 9.10 MJ/kg.(2) In this test, GE and DM digestibility increased notably with dietary energy intake levels improving(P<0.05). In probationary and mating period, dietary energy intake levels had a significant effect on CP digestibility(P<0.05), while there were no remarkable effect on NDF and ADF digestibility, but NDF and ADF digestibility of bucks showed a trend of increasing with energy intake levels improving. In recovery period, dietary energy intake levels had no significant effect on CP and ADF digestibility, but influented NDF digestibility of bucks significantly(P<0.05).(3) Different energy intake levels had no significant effect on glutamic-pyruvic transaminase(GPT) and glutamic-oxalacetic transaminease(GOT) activities. With erergy intake levels rising, the contents of glucose(GLU), triglyceride(TG) and total cholesterol(TC) increased while urea nitrogen(UN) decreased.(4) In the whole mating period, semen collection frequency had an extremely significant effect on serum testosterone concentration and ejaculation of bucks(P<0.01). Dietary energy intake levels affected the number of effective spermatozoa extremely notly(P<0.01) and influented ejaculation and sperm density significantly(P<0.05). There was no significant effect on sperm motility of bucks(P>0.05). The ejaculation, sperm density and the number of effective spermatozoa in group 8.05 MJ/kg were optimum. Semen quality under the frequency of two times per five days were superior to the frequency of four times per five days. The semen collection frequency×dietary energy intake levels interaction had no significant effect on ejaculation, sperm motility, sperm density and the number of effective spermatozoa(P>0.05), while influented serum testosterone concentration extremely significantly(P<0.01).(5) The digestible energy(DE) and metabolizable energy(ME) regression formula of Shanbei white cashmere goat bucks were as follows:Probationary:DE(MJ/d)= 0.642W0.75+ 0.083ADG(R2=0.993,P=0.002)ME(MJ/d)= 0.527W0.75+ 0.068ADG(R2=0.992,P=0.005);Mating Period:DE(MJ/d)=(0.642+0.4644n)W0.75ME(MJ/d)=(0.527+0.3800n)W0.75;Recovery Period:DE(MJ/d)=0.555W0.75 + 0.064ADG(R2=0.996,P=0.001)ME(MJ/d)=0.455W0.75+ 0.053ADG(R2=0.992,P=0.004).(6)It was recommended that the appropriate range of ME concentration in diet for Shanbei white cashmere goat bucks was 8.05 MJ/kg~8.99 MJ/kg. |
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