Effect of zinc methionine supplementation on productive performance of lactating friesian cows

Ano: 2011 | Volume: 2 | Número: 1

Palavras-chave: digestibility, rumen activity, milk yield and composition, feed conversion, economic efficiency

Resumo Inglês:

Twelve lactating Friesian cows with body weight of 450 to 550 kg and at 2nd to 5th lactating season were used after 8 weeks of calving in a complete switch–back design. The cows were fed the basal ration consisted of 35% concentrate feed mixture + 40% berseem + 25% rice straw (on DM basis) without supplementation (G1) or supplemented with 5 g zinc methionine per head per day for G2 and 10 g zinc methionine per head per day for G3. Nutrients digestibility coefficients and nutritive values were increased significantly (P<0.05) by zinc methionine supplementation. Cows in G2 had the highest feed intake of total digestible nutrients (TDN) and digestible crude protein (DCP) followed by G3, with lowest feed intake in G1 (P<0.05). Ruminal total volatile fatty acids (TVFA's) concentration increased and ammonia nitrogen (NH3-N) decreased significantly (P<0.05) by zinc methionine supplementation. Cows in G3 showed the highest plasma total protein, albumin and globulin concentrations (P<0.05). Zinc methionine supplementation led to significant decrease (P<0.05) in the activity of AST and ALT. Significant increase (P<0.05) was observed in the yield of milk for G2 (2.54 kg/day or 18.1%) and G3 (1.95 kg/day or 14.2%), compared with the control group. The corresponding increase of 4% FCM was 2.85 and 2.03 kg/day or 21.63 and 15.74% for G2 and G3, respectively. Cows in G2 had the highest fat, total protein and TS contents and the yield of all milk constituents and animals in G3 showed the highest contents of lactose, SNF and ash. Zinc methionine supplementation improved feed conversion, leding to reduce the quantities of DM, TDN and DCP required to produce one kg of 4% FCM (P<0.05). Average daily feed cost per kg of 4% FCM decreased and average income from milk production increased with zinc methionine supplementation (P<0.05). From quadratic analysis, it is showed that the optimal level of zinc methionine supplementation is at a level of 6 g per head per day in terms of milk yield and net revenue.