EFFECT OF VARYING DIETARY RUMEN UNDEGRADED PROTEIN ON NUTRIENT INTAKE, NUTRIENT DIGESTIBILITY AND PRODUCTION PERFORMANCE IN EARLY LACTATING CROSSBRED COWS

The rumen bypass protein has extensively been used in ruminant's diets to enhance their productivity. The objective of this study was to determine the effect of varying levels of dietary rumen undegraded protein (RUP) on nutrient intake and digestibility, milk yield and composition in early lactating crossbred cows. Twenty four early lactating crossbred cows of same parity and similar milk production were divided into 4 groups (6 cows per group). Four iso-caloric and iso-nitrogenous diets were formulated using NRC standards for energy and protein. The rations were formulated to contain 30, 40, 50 and 60% RUP levels. Data regarding nutrient intake, nutrient digestibility, N balance, blood chemistry, milk yield and its composition were collected. The dry matter (DM), neutral detergent fiber (NDF) and acid detergent fiber (ADF) intakes increased (p< 0.05) at higher dietary RUP; however, crude protein (CP) intake remained similar. The DM, CP, NDF and ADF digestibility did not alter at lower RUP level (30 and 40%) but at higher dietary RUP level (50 and 60%) digestibility numerically decreased (p> 0.05). The nitrogen balance was negative in cows fed RUP30 and RUP40 diets but it was positive in cows fed RUP50 and RUP60 diets. The blood pH and blood glucose and differential leukocyte count resulted in similar (p> 0.05) values across all dietary treatments. The blood urea nitrogen, milk urea nitrogen and blood creatinine decreased (p< 0.05) at higher dietary RUP level. The milk yield increased (p< 0.05) as the level of dietary RUP increased. Milk composition (milk protein, milk lactose, solid not fat and totals solids) remained similar across all dietary treatments. However, milk fat content increased (p> 0.05) with increasing level of dietary RUP. In conclusion, the nutrient intake, milk production and milk fat increased by increasing the dietary RUP level. But nutrient digestibility decreased at higher rumen un-degradability of protein.