Nitrogen Use Efficiency for Milk Production on Feeding a Balanced Ration and Predicting Manure Nitrogen Excretion in Lactating Cows and Buffaloes under Tropical Conditions

Abstract

A field study on 7090 lactating cows and 4534 lactating buffaloes was conducted to evaluate the effects of feeding a balanced ration on milk production, nitrogen use efficiency (NUE) and to develop models for predicting manure nitrogen excretion (NE). Data were collected from 529 villages, under ration balancing programme being implemented in different states of India. Based on the days of lactation, animals were categorized as early ( 200 d) stages of lactation. On feeding a balanced ration, milk yield increased (P<0.05) by 6.2, 4.5 and 5.9% in early lactating local cows, crossbred cows and buffaloes, respectively. Milk yield was not affected in the mid stage of lactation, however, it improved by 3.7, 2.3 and 5.9% during the late stage of lactation in local cows, crossbred cows and buffaloes, respectively. Average milk fat increased by 1.2, 0.9 and 1.8 g/kg, while cost of milk production reduced (P<0.05) by 24, 16 and 14% in local cows, crossbred cows and buffaloes, respectively. Average dietary nitrogen intake (NI) reduced (P<0.05) by 14.1% on feeding a balanced ration. Percent dietary NE in manure reduced (P<0.05) from 81.6 to 78.0%, indicating improved NUE from 0.18 to 0.21 in all species. Linear regression equations were developed to predict the manure NE and revealed a strong positive correlation between dietary NI and manure NE, indicating dietary NI as the best predictor for manure NE (r2=0.97). Available N models were also compared with our models and Weiss (2009) model fits with our models for predicting manure NE (0.21 kg/d) in lactating animals. Result demonstrates that balanced feeding improved NUE for milk production, by way of improving nutrient utilization and reducing its excretion in manure.