Effect of lysozyme feed supplementation level on growth performance and apparent nutrient digestibility in Holstein calves

Eighteen Chinese Holstein calves weighing (36.72 ± 0.96) kg were randomly divided into three groups of six calves each that were fed milk containing different doses of lysozyme as follows: the control group was fed no lysozyme; group A was fed 7.5 g lysozyme per head per day; and group B was fed 15 g lysozyme per head per day. At 50～56 days old, the three groups of calves were fed milk with the different lysozyme levels plus the same weight of calf starter to study the effects of these different doses of lysozyme on the growth performance and digestive capability (measured as apparent nutrient digestibility) of the calves. The results were as follows. 1) The average 28-day-old body weights of calves in group A and group B were significantly higher than that of the control group (P < 0.01), the average 42-day-old and 56-day-old body weights of calves in group A were significantly higher than those of group B and the control group (P < 0.01), and the average daily gain of calves in group A was significantly higher than those of group B and the control group (P < 0.05); the body height of group A at 42 days was significantly greater than those of group B and the control group (P < 0.01); the oblique lengths of the 28-day-old and 42-day-old calves in groups A and B were significantly greater than those of the control group (P < 0.01), while the oblique length of the 56-day-old calves only in group A was significantly greater than that of the control group (P < 0.01); the chest circumferences at 14 and 56 days of group A was significantly greater than those of group B and the control group (P < 0.05), while the chest circumference of group A at 28 days was significantly greater than that of the control group (P < 0.01), and the group A chest circumference at 42 days was significantly greater than those of both group B and the control group (P < 0.01); and the circumferences of the 28 and 42 day old calves in group A were significantly greater than those in group B and the control group (P < 0.01), while that of the 28 day old calves in group B was significantly larger than that of the control group (P < 0.01). 2) The digestibility of dry matter and crude protein in group A was significantly higher than in group B and the control group (P < 0.05). These results show that growth performance and digestive capability of calves was improved by adding lysozyme during lactation, and that the addition effect of 7.5 g·(head·d)^-1 was better than that of 15 g·(head·d)^-1. This finding can be used as a reference in practical production.