Effect of dietary supplements of zinc-methionine on milk composition and subclinical mastitis in extensive dairy awassi sheep herd of bekaa valley of lebanon

An experiment was conducted to investigate the effect of supplementation of organic chelated trace mineral Zinc-Methionine ZM complex (ZINPRO®, Zinpro Corporation, Eden Prairie, MN, USA) on extensive Awassi sheep herd submitted to subclinicalmastitis SCM in Bekaa valley of Lebanon. The effects of ZM complex on milk quality (fat, protein and somatic cell count SCC) were examined. 32 Awassi ewes were randomly assigned after separating them into two groups: ZM- group of 16 ewes affected to a control group that were fed on basic ration with no mineral premix (barley, wheat bran, soybean meal, salt, vitamins and hay) and ZM+ group of 16 ewes affected to an experimental group that received a supplement of ZM in their basic ration with an average of 600 mg/head/day for the first month then 1200 mg/head/day for the next month of the trial. Moreover, each group was separated into 2 sub-groups: CMT+ group (n=8) positive to California mastitis test (CMT) and CMT- group (n=8) negative to CMT. In total, 4 groups of 8 ewes each were assigned: ZM+CMT+, ZM+CMT-, ZM-CMT+ and ZM-CMT-. Treatment affected significantly milk protein percent (3.72 ± 0.03 vs 3.63 ± 0.03 % for ZM+ vsZM-,p<0.05), fat percent (5.60 ± 0.07 vs 5.35 ± 0.07 % for ZM+ vs ZM-, p<0.05), and SCC count (339.82 ± 4.48 vs 324.63 ± 4.48 x103 cells/ml for ZM+ vs ZM-, p<0.05). However, milk protein, fat percent and SCC count were significantly different in the infected halves (CMT+) comparing to the non-infected halves (CMT-) in both groups (milk protein and fat percent was lower in CMT+ comparing to CMT-; 3.55 ± 0.03 vs 3.80 ± 0.03, p<0.001 and 4.99 ± 0.07 vs 5.95 ± 0.07, p<0.001 respectively), while SCC count was higher in CMT+ comparing to CMT-; 377.70 ± 4.48 vs 286.76 ± 4.48 x103 cells/ml, p<0.001). Interestingly, the effect of ZM on the experimental affected group was significant (p<0.05) over time especially in the second month of the trial (increase of 1.83%, 4.55% and a decrease of 12.6% in milk protein, fat percent and SCC count in ZM+CMT+). Finally, supplementation of ZM improved dairy performance and udder health by reducing somatic cell count and increasing protein and fat contents in affected ewes.