Effects Of Dietary Nutrition Regulation On Nutrient Metabolism, Lactation And Semen Quality In Holstein Cattle

According to the current status of animal production at home, the effects of protein and energy ratio on rumen fermentation, performance, blood biochemical parameters, nitrogen metabolism and nitrogen efficiency for the early lactating dairy cows were investigated by using dual outflow continuous culture trial, artificial gas production trial, feeding trial and digestion -metabolism trials. In addition, the effects of vitamin and zinc on semen quality and its optimal level in diet were investigated in hot environment as well due to the decline of bull semen quality in hot weather.Exp.1 Twelve dual-flow continuous-culture fermenters were used to evaluate the effects of rumen-degradable protein balance (RDPB) on rumen fermentation. The entire experimental period was 8 days, including 5 days for adjustment and 3 days for sample collection. Six diets including RDPB levels of -16.84, -8.87, -0.87, +7.13, +15.13 and +23.12 g/kg DM were considered. It indicated that RDPB significantly affected the NH₃-N content in the fermenters (P < 0.0001), whereas there were no significant effect on the pH value (P = 0.058), total VFA concentration (P = 0.57) and the acetate concentration (P = 0.70). The decreasing RDPB concentrations led to the reduction of rumen-available N in diets. Compared with the RDPB level of + 23.12 g/kg DM, the rumen-available N contents under the RDPB levels of +15.13, +7.13, -0.87, -8.87 and -16.84 RDPB g/kg DM deceased by 6.22%, 30.45%, 50.03%, 55.35% and 54.22% respectively. The concentrations of total VFA, acetic acid and valeric acid at different incubating time were significantly different among treatment group (P < 0.05). With the increasing RDPB concentrations in diets, the total ammonia nitrogen (NH₃-N) in fermenters and the N losses linearly increased.Exp.2 The influences of RDPB on rumen fermentation, total gas and methane production in vitro were analyzed in Exp.2. Based on the ANKOMRF Gas Production System, a random block design was used, with six RDPB diets of -20, -10, 0, 10, 20 and 30 g/kg DM with 3 replicates for 24 hours. The results showed that: (1) The fermentation pH, acetic acid/propionic acid, amount of gas production and CH4 production in the two groups of 0 g/kg DM or 10 g/kg DM were lower than the other groups; (2) the acetic acid, propionic acid and butyric acid as volatile fatty acids and rumen ammonia concentration increased with the equilibrium values of the degradation, indicating a significant effect on the rumen fermentation by the RDPB levels, while no significant effects on protozoa population and the total volatile fatty acids concentration were observed; (3) the methane concentrations at different time and 24-h methane production were influenced by RDPB. Thus, with culture conditions in vitro, the dietary RDPB affected rumen pH, NH₃-N, VFA concentration, gas production and CH4 production. The results indicated that the optimal RDPB concentrations were between 0 and 10 g/kg DM, according to rumen fermentation and methane production in vitro. Exp.3 The experiment investigated the effects of different dietary NFC/RDP on the digestibility, blood biochemical parameters, nitrogen losses, and performance of lactating dairy cows. Forty-five Chinese Holstein cows at early lactating stage were randomly divided into three groups (n = 15) in a single-factor design. Three experimental diets were used at different levels of NFC/RDP: 3.5 (groupâ… ) , 4.0 (groupâ…¡) and 4.5 (groupâ…¢). The trial duration was 75 days (including the pre-feeding of 15 days and the formal period of 60 days). The results showed that dietary NFC/RDP ratio affected the performance of dairy cows. The milk yield, dry matter intake, milk protein yield and feed conversion ratio in groupâ…¡were highest, which were 29.30 kg/d (P=0.0167), 21.01 kg/d (P=0.0048),913.28 g/d (P=0.0824) and 1.3 (P=0.0003), respectively. Apparent digestibility of dry matter, protein and NDF in groupâ…¡i ncreased by 68.99% (P=0.0015), 73.34% (P=0.0006) and 54.65% (P=0.0076), respectively, in comparison with other groups. With the reducing dietary NFC/RDP ratio from 3.5 to 4.5, manure nitrogen excretion and urinary nitrogen excretion were significantly decreased as well. Apparent total-tract nutrient digestibility varied among different treatments. Although N intakes in groupâ…¡and groupâ…¢were higher (22 g/d and 59 g/d) than groupâ… , the apparent fecal, urinary and milk N outputs were significantly affected, with a major effect of NFC/RDP on urinary N output. The Exp.3 also demonstrated that N utilization and retention were highest in groupâ…¡(49.62% and 20.16%), and feces excretion was the main source of N loss. The antioxidant capacity of dairy cows was also affected by NFC/RDP, NO concentration in serum (P=0.0081) and antioxidant capacity (P=0.4449) in groupâ…¡were highest. When NFC/RDP ratio was 4.0, serum insulin-like growth factor-1 was affected quadratically with the reducing NFC/RDP ratio. Therefore, adjusting dietary NFC/RDP ratio could improve the performance of dairy cow as well as reduce the nitrogen excretion of dairy cow and the environmental pollution caused by animal production.Exp.4 The effects of dietary vitamins (vitamin E and beta-carotene) and zinc on semen quality, antioxidant indicators, cytokines and other blood parameters in hot weather were analyzed in Exp.4. Sixty healthy and purebred Holstein bulls (BW=1010±80kg) were randomly classified into 4 groups (n = 15): groupâ… , control group (basal diet); group II, basal diet +100 mg/kgDM Zn; group III, basal diet + antioxidant (300 mg/kgDM vitamin E and 60 mg/kgDM beta-carotene) and group IV, basal diet +100 mg/kgDM Zn + vitamins (300 mg/kgDM vitamin E and 60 mg/kgDM beta-carotene). The trial duration was 120 days. The results showed that vitamins and zinc could significantly increase the semen quality, vitality of fresh semen (groupâ…£0.649 VS groupâ… 0.575), sperm density (groupâ…£15.16×108/ml VS groupâ… 11.81×108/ml), vitality of frozen semen (groupâ…£0.34 VS groupâ… 0.283) and acrosome integrity rate (groupâ…£45.2% VS groupâ… 41.8%) but decreased the sperm deformity rate significantly (groupâ…£1 3.47% VS groupâ… 16.81%). However, there was no significant effect on ejaculate volume (groupâ…£11.56ml VS groupâ… 10.33ml). In addition, the total SOD activity of serum (P=0.1489) could be enhanced by the vitamins. Also, the serum Cu-ZnSOD activity may be significantly increased by the supplemental vitamins or vitamins+zinc (P=0.0008); the individual or combination of supplemental vitamins and zinc significantly positively affected the serum T-AOC (P<0.0001) activity; supplemental zinc or combination of vitamins and zinc increased serum GSH-PX activity significantly (P=0.0041); the serum MDA (P=0.0535) concentration and hydroxyl radicals (P=0.0698) were markedly reduced as the result of adding vitamins and zinc. Supplemental vitamins significantly increased the total SOD (P=0.0087) and T-AOC (P=0.0001)activities in seminal plasma; the Cu-ZnSOD activity (P=0.0181) in seminal plasma was increased by the addition of zinc. The concentration of testosterone and ceruloplasmin protein in serum and seminal plasma increased strongly due to the supplement of vitamins and zinc (P<0.01); The concentration of seminal metal sulfur protein (P<0.05) rose significantly with the supplemental zinc, while there was no obvious changes in serum metal sulfur protein. Serum IL-6 (P=0.0016), IL-17 (P=0.0003) and TNF-α(P=0.0357) concentrations as well as the seminal IL-6 (P=0.0233) concentrations decreased significantly, which were caused by the supplemental viteamins and zinc. In conclusion, a diet with 300 mg/kgDM of vitamin E, 60 mg/kgDM of beta-carotenoids and 100 mg/kgDM Zn could improve the semen quality in hot weather.