Effect of protected-glutamine supplementation on performance, milk composition and some blood metabolites in fresh Holstein cows.

The present study was conducted to study the effect of protected-glutamine (Gln) supplementation on dry matter intake (DMI), milk yield (MY) and composition, somatic cell counts (SCC) and blood parameters in fresh cows. Forty Holstein cows at zero day of parturition (calving day = day 0) were divided into four groups (n=10), and fed (ad libitum) with one of the diets including: basal diet (control), basal diet supplemented with 150 (low Gln, LG), 250 (medium Gln, MG) or 350 (high Gln, HG) g of Gln protected with formaldehyde/cow per day. The DMI and MY were recorded from 0 to 21 days post-calving. Milk fat and protein were assessed on days 7, 14 and 21, and blood was collected on days 0, 7, 14, and 21 after parturition. The DMI and MY at 21 days in milk (DIM) in HG group were compared with control (P<0.05). The DMI at 14 and 21 DIM and the MY at 21 DIM were higher in MG group compared with control group (P>0.05). Glucose concentration at 7, 14 and 21 DIM increased in both HG and MG groups compared with control group (P>0.05). The milk SCC of Gln groups was lower (P<0.05) compared with control, at 14 and 21 DIM. Glutamine supplementation increased the blood concentrations of total protein and albumin, but lowered the β-hydoxybutyrate (BHBA), non-esterified fatty acids (NEFA) and aspartate amino transferase (AST) concentrations (P<0.05). These results indicate that rumen protected Gln supplementation at 250 g/heat/day to fresh Holstein cows improved the SCC in milk and health status.