Effect of milk intake level on performance, skeletal growth and plasma metabolites of Holstein female calves

Milk consumption is one of the most important factors affecting growth and survival of calves in the pre-weaning period. Usually due to the higher cost of milk for feeding calves, it is recommended that the amount of milk intake be maintained at about 10% of body weight (4 liters per day), so that the calf is more encouraged to intake starter diet. In recent years, researchers have been looking for the best milking pattern to support the growth of calf more economically .The aim of this study was to compare the effect of two milk intake patterns, including conventional (4 kg / day) and free milk intake on the performance, skeletal growth, and blood metabolites of Holstein female calves. Thirty newborn Holstein female calves with average BW of 42.7 ± 2.2 kg were used in a completely randomize design. Experimental treatments included of conventional (4 Kg/d) and ad libitum milk intake. The experiment carried out in two periods: pre-weaning (day 1 to day 60) and post-weaning period (day 61 to day 120). Calves fed milk twice daily in the morning and the afternoon and had free access to starter diet and water. Starter intake was measured daily and ADG was calculated in a weekly basis. Skeletal parameters including body length, withers height and pin distance were taken at weaning (day 60) and end of the experiment (day 120). Blood metabolites including glucose, total protein, triglyceride and cholesterol were measured on days 30 and 60 of the study. The results showed that calves fed ad libitum milk intake had lower pre-weaning starter intake (P<0.01) and greater starter intake (P<0.01) during post-weaning and overall periods than those fed conventional milk intake. In calves fed ad libitum milk intake, average daily gain was higher (P<0.01) than the calves fed conventional milk intake during pre-weaning and overall periods but it was lower (P<0.01) during post-weaning period. Feed efficiency was higher during pre-weaning (P=0.05) and lower during pre-weaning period (P<0.01) in calves fed ad libitum than those fed conventional milk but it was insignificant in the overall period (P>0.05). Body weight of calves fed ad libitum milk intake was greater during pre-weaning, post-weaning and overall periods than those fed conventional milk intake (P<0.01). Calves fed ad libitum milk intake had greater (P<0.05) body length than those fed conventional milk intake. Plasma glucose and cholesterol concentrations were greater (P<0.05) in calves fed ad libitum milk intake than those fed conventional milk intake in day 30 of experiment. Plasma total protein and cholesterol concentrations were not affected by milk intake pattern (P>0.05). It is concluded that ad libitum milk intake resulted in better performance of dairy calves