Evaluation of zinc methionine as a feed supplement for improving milk quality in dairy goats
2001
Salama, A.
Lactation, methionine administration, and metabolism trials were conducted to investigate the effects of supplementation with Zn-Methionine (Zn-Met) on milk yield, milk composition, milk somatic cell counts (SCC), udder health, N and Zn metabolism in 22 Murciano-Granadina dairy goats machine milked once-a-day. Treatments were: Control (CON) and supplemented (ZnM) with 1 g per d Zn-Met. Average milk yield was not affected, but percentage of milk fat tended to decrease by 8.8 per cent when Zn-Met was supplemented. Milk whey protein and non-protein nitrogen were lowered by 9.7 and 14.7 per cent, respectively as a result of Zn-Met supplementation. The arithmetic and geometric means of milk SCC decreased by 28 and 19 per cent, respectively as a result of supplementation, but control values were reduced and differences between treatments were not significant when halves with persistent infection were excluded from the analysis. Infection incidence was 15 per cent for CON group vs. 5 per cent for ZnM group. During the methionine injection trial, hand milking resulted in a dramatic increase in milk SCC by 86 and 37 per cent in CON and ZnM groups, respectively. For the metabolism trial, N absorption increased (6.6 per cent) and Zn retention was higher (145 per cent) for Zn-Met supplemented goats. Milk content of Zn did not differ between treatments. We conclude that, Zn-Met supplementation improves the udder resistance to mastitis and the stress of hand milking. Zn retention and protein utilization in the whole animal body were also improved when Zn-Met was supplemented
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