Breeding and Genetics: Genetics of Efficient Feed Utilization

Sixteen multiparous Holstein cows were used to determine the effect of glutamine (Gln) on immune responsiveness and milk production during the immediate postpartum period, when there are competing demands from the gut, mammary gland, and immune system. Cows received abomasal infusions of either 300 g/d Gln delivered in 10 L of water (8 cows) or water alone (8 cows) for 21 d following calving. During d14-21, treatments did not affect milk yield (39.3 vs. 40.5 kg, P = 0.66), protein content (2.99 vs. 2.98%, P = 0.87) or fat content (3.92 vs. 3.73%, P = 0.46), for water and Gln, respectively. Peripheral blood mononuclear cells (PBMC) were isolated from blood collected by jugular venipuncture on d -25, 4, 11, and 18 relative to calving. Interferon-γ concentrations, the lymphocyte proliferative response to concanavalin A (0.5 μg/ml), and cell subpopulations were determined on the PBMC. Leukocyte counts and differential analysis were also performed on these days plus on d -12, -3 and 1 relative to calving. Interferon-γ concentration did not change over time (P=0.35). Lymphocyte proliferation was not affected by treatment (0.84 vs. 0.71 for water and Gln, respectively; P = 0.38), or by time (P = 0.44). There was a tendency (P=0.09) for a treat*time interaction for the CD4 population, due to a reduction at d4 for the water treatment compared to d 11 and 18, while there was no change for Gln treatment. Leukocyte and neutrophil counts changed over time (P < 0.001), with the counts being higher on d1 than during the treatment period. The data from this study suggest that Gln supplementation does not improve the immune status of postpartum dairy cows. Pretreat1 Treat2 Precalf SEM Day 1 SEM Water Gln SEM P3