Effect of partial replacement of dietary starch with fiber and fat on performance, feeding behavior, ruminal fermentation and some blood metabolites of Holstein calves

Abstract

Two experiments were conducted to investigate the effects of partly replacing dietary starch with fiber and fat on growth performance, ruminal fermentation, and blood metabolites during preweaning and postweaning periods (experiment 1) and preference for high starch (HS) and high fiber and fat (HFF) diets after weaning (experiment 2) in calves. In experiment 1, a total of 30 Holstein female calves (4 d of age; 41.0 ± 2.0 kg of body weight) were assigned randomly to a 1) HS starter, 2) HFF starter, and 3) a starter feed containing mixture of diets 1 and 2 (MIX). In experiment 2, 20 weaned Holstein female calves (85 ± 2.0 kg of body weight (BW) were involved in a pairwise preference tests 3 and 5 d postweaning between HS and HFF diets. Diets contained alfalfa hay as forage source; HS contained 430 g/kg starch, 35 g/kg fat, and 163 g/kg neutral detergent fiber, whereas HFF contained 82 g/kg starch, 75 g/kg fat, and 336 g/kg neutral detergent fiber. The results of the first experiment showed that dry matter intake was higher in the MIX diet group in the postweaning period than the other groups and had a tendency to increase dry matter intake throughout the study period. Average daily gain, feed efficiency, body weight, and skeletal growth were not different between treatments. Blood glucose and insulin concentrations (d 35 and 70) were higher in calves fed the HS diet compared to the other treatments. Plasma β-hydroxybutyric acid (BHBA) concentration (d 70) of calves fed HFF diet was higher than those of the HS and MIX diets-fed calves. Rumen fluid pH and acetate concentration in calves fed the HFF diet were higher than those fed the HS and MIX diets. Postweaning, time spent eating was highest in HFF group and lowest in HS group. Calves in HS treatment devoted less time to rumination compared with HFF calves during both pre- and postweaning periods. Lying time was lower for calves fed HFF diet during both pre- and postweaning periods than those fed the HS and HFF diets. The result of the second experiment showed that calves preferred the HFF diet over the HS diet. Results of the present study indicated that despite higher short term preference for HFF than HS diet, performance response and skeletal growth were similar for HS and HFF diets. Providing MIX diet rather than HS and HFF diets increased postweaning intakes of starter without improving ADG and final BW. The practical relevance of HFF diet for long-term productivity of dairy calves remains to be determined.