Effect of the composition of starter diet fed in the rearing phase on the performance and certain physiological parameters of Holstein calves

The objective of this study was to compare the effects of calf starters of different starch and fibre content on the growth, blood and rumen parameters of Holstein female calves during the pre-weaning period. A total of 60 calves were divided into two groups. Group A/B was fed according to a two-phase calf nutrition system: the calves received calf starter "A" (28.5% starch content, 16% neutral detergent fibre (NDF), 9.2% acid detergent fibre (ADF)) in days 7-45 and then calf starter "B" (14.2% starch content, 32.4% NDF, 14.3% ADF) in days 46-70. Calves of group B received calf starter "B" throughout the experimental period. The calves were weaned between 52 and 61 days of life. The data on body weight, weight gain, starter feed intake, blood metabolites and rumen fermentation parameters were collected individually. In the first phase of experiment, the starter feed consumption of A/B group was higher than that of B group (P < 0.05), but it did not manifest in differences in body weight at weaning time. At some of the sampling times, the different composition of starter diets significantly (P < 0.05) influenced the plasma urea, albumin, glucose and triglyceride concentrations. The consumption of diet with different starch and NDF content had no significant effect either on the composition of the rumen microbiota or on the ruminal concentration of volatile fatty acids (VFA) and ammonia. In some cases significant correlations (-0.83 and -0.93; 0.82 and 0.90) were found between the composition of rumen microbiota and ruminal VFA concentration. Feeding a diet of higher starch content (28.5 vs 14.2%) in the first 45 days of life did not affect rumen fermentation, rumen microbiota and the most important blood metabolites, apart from a few exceptions. The production parameters of calves, including total feed intake and body weight gain, were similar in the experiment.