INFLUENCE OF DIETARY ENERGY AND PROTEIN INTAKE ON YIELD AND COMPOSITION OF MILK IN CROSSBRED

Abstract

The study was carried out on 120 crossbred Holstein X Shahiwal dairy cows for a period of 150 days to quantify the influence of dietary energy and protein intake on yield and composition of milk. Total 12 dairy farms having similar housing systems and holding at least 20 dairy cows in between mid to late lactation were selected for study purposes. The farms were located in the peri-urban and urban areas of Chittagong, Bangladesh. Milk samples were collected from individual cow. Milk from cows having same BCS were mixed together to make a composite sample. Chemical analyses of the samples were carried out in triplicate for fat, protein, lactose, total solids (TS), solids not fat (SNF) and ash. Dietary Metabolizable Energy (ME) and crude protein (CP) intake were measured by analyzing the amount of total mixed ration ingested by the individual cow. Results indicated that, ME intake (MJ/d) significantly (P<0.01) influenced milk yield, milk fat and TS content of milk in crossbred Holstein Friesian dairy cows. Similar to ME, CP intake (g/d) also influenced (P<0.01) milk yield, fat, protein, lactose, TS and ash content of milk. Correlation coefficient matrix indicated that, milk yield was positively correlated with ME and CP intake. However, there was a negative association between ME or CP intake and milk protein, lactose, TS and SNF of milk even though the strength of association was variable. It could therefore be inferred that, adequate dietary ME and CP intake is important to optimize milk yield and milk composition in crossbred Holstein X Shahiwal dairy cows reared under intensive farming systems in tropical regions