Effects Of Isovalerate Acid On Growth Performance, Growth Axis Hormone Receptors Expression And Blood Parameter In Dairy Calves

This was conducted to determine the effects of isovalerate acid on growth performance, growth axis gene expression and blood parameter in dairy calves. Thirty-nine dairy calves (15-day-old) were similar birth weight (45.09±0.90 kg), at 15 d, three dairy calves were determining the body weight and body size, then the dairy calves were slaughtered and the liver and muscle sampled, the other were randomly divided into four groups. The treatments were:control (the basal diet with 0 g/d), LIV, MIV and HIV (the basal diet with 3 g/d,6 g/d and 9 g/d respectively). At 30 d,60 d and 90 d, determining the body weight and body size, then the dairy calves were slaughtered and the liver and muscle sampled. The results showed that:at 15 d and 60 d, the body weight of calves were elevated not significantly (P>0.05), but the body weight of calves improved a lot with 9 g/d isovalerate acid supplementation at 30 and 90 days old (P<0.05). At 15～30 days, the average daily gain of calves in group MIV and HIV was significantly higher than control group and LIV group (P<0.05). At 30～60 days of age, the average daily gain of calves improved but there was no difference between LIV, MIV and HIV groups (P>0.05). Besides, at 60-90 days, average daily gain of calves were significantly higher than control (P<0.05), and there was no significant difference between LIV, MIV and HIV groups (P>0.05). At 60 and 90 days, body height, body length, calf circumference, chest depth and width, waist width of calves were significantly improved by 6g/d and 9g/d supplemental isovalerate acid compared with control and 3g/d groups (P<0.05). Digestibility of calves, including CP, EE, CF, ADF and NDF, was all improved with isovalerate acid supplementation. Digestibility of calves was promoted with 6g/d and 9g/d supplemental isovalerate acid, and there was no significant difference between the MIV groups and HIV groups (P>0.05). In addition, the expression of GH, INS, GF-1 receptor mRNA of muscle and liver tissues (P<0.05) improved a lot with supplemental isovalerate acid, and there was no difference between MIV groups and HIV groups (P>0.05).Compared with control groups, the expression of MSTN receptor mRNA was reduced of calves with isovalerate acid supplementation. Moreover, blood parameter were enhanced a lot by supplemental isovalerate acid (P<0.05). Contents of Glu, Alb, BUN, LA, GOT, GPT, AKP, GH, INS, IGF-I of calves with 6g/d and 9g/d isovalerate acid supplementation were higher than control (P<0.05). At last, the eye muscle area and muscle fat were determined, and there was no significantly influence on the indexes (P>0.05). In summary, the optimum dose of isovalerate acid supplementation was 6g/d.