Effects of diets with different solid-to-liquid feed ratios with the same dry matter intake on the growth performance and gastrointestinal development of male Holstein calves

Abstract This study investigated the effects of diets with different solid-to-liquid feed ratios with the same dry matter intake on growth performance, blood metabolites, rumen development, and gastrointestinal development in male Holstein calves. Calves (n = 36; average 28 ± 2 days of age; 46.4 ± 0.78 kg body weight) were randomly assigned to three groups: the control group (n = 12; solid to liquid feed ratio = 1:2 at 28 days of age (d 28), then, the solid feed supply was increased by 200 g per week until the ratio was changed to about 1:1 at d 56), high liquid (HL) group (n = 12; solid to liquid feed ratio = 1:2 at d 28, then, the solid feed supply was increased by 100 g per week until the ratio was still about 1:2 at d 56), and high solid (HS) group (n = 12; solid to liquid feed ratio = 1:2 at d 28, then, the solid feed supply was increased by 400 g per week until the ratio was changed to about 1:0 at d 56). The calves were reared with three different feed types while maintaining the same dry matter feed supply and dry matter intake among the three groups before weaning. The calves from both the control and HL groups were weaned at 56 days of age with approximately 1 kg and 0.5 kg of daily solid feed intake, respectively. The calves from the HS group were weaned at 42 days of age with approximately 1 kg of daily solid feed intake. Calves were weighed at 2-week intervals, and both blood and rumen fluid samples were also collected at 2-week intervals. Calves were slaughtered, and various organs were collected for analysis. Compared with the control and HL diets, the HS diet increased the daily solid feed intake. The average daily gain did not differ among the three groups until 56 days of age, but the HS diet increased the average daily gain compared to the HL diet from 56 to 84 days of age. Compared with the HL diet, the HS diet increased the ruminal molar proportion of acetate and butyrate and the total volatile fatty acid concentration at 84 days of age. Compared with the HL diet, the HS diet improved blood IgG and insulin-like growth factor 1 concentrations, and increased the weights of the rumen and whole stomach and increased the papilla length and tunica muscularis thickness of the rumen, especially the tunica muscularis thickness of the duodenum. In conclusion, feeding an HS diet along with early weaning at 42 days of age increased solid feed intake and resulted in improved growth performance, molar proportion of butyrate in the rumen, blood immune index levels and gastrointestinal development of post-weaned Holstein male calves.