Effects Of Carbohydrate And Protein Compositions In Milk Replacer On The Growth Performance And Gastrointestinal Development Of The Holstein Calves From 35 To 70 Days Of Age

Years witnessed the improvement of dairy calf rearing,and high planes or even unrestricted levels of milk or calf milk replacer supply have been a global tendency in dairy calf rearing.Alternative carbohydrate and protein sources may decrease milk replacer cost if calf performance is similar.The study was designed to determine whether carbohydrate and protein compositions in milk replacer could influence growth performance,incidence of diarrhea,serum metabolites,and gastrointestinal development in Holstein calves from 35 to 70 days of age.Forty Holstein calves(d 28;25 female calves,56.14 ± 2.24 kg body weight;15 male calves,58.93 ± 3.41 kg body weight)were randomly assigned to 4 milk replacer treatments and 1 control treatment(5 female calves and 3 male calves per treatment).The milk replacer treatments represented a 2 × 2 factorial arrangement of carbohydrate composition(L1,the ratio of glucose to lactose was 0.03;L2,the ratio of starch and glucose to lactose was 0.25)and protein composition(the ratio of a combination of wheat protein and soybean protein to whey proteins was 0.87 in WP1 and 1.87 in WP2).Calves were fed whole milk(WM)in the control treatment.The transition period of milk replacer was from d 28 to d 34,and then calves received 12 L/d of liquid feed from d 35 to d 50.The transition period of weaning was from d 51 to d 60.Calves were weaned at d 60 and female calves remained until d 70.Nine male calves from the L1WP2,L2WP2,and WM treatments(n =3/treatment)were selected at weaning for slaughter.There were no differences in growth performance among MR treatments.The starter intake was affected by the interaction of L × day(P < 0.01).There were differences in weaning withers height with carbohydrate composition(P = 0.047)and final body length with protein composition(P = 0.03).The WP2-fed calves had a lower incidence of diarrhea than those fed WP1(P = 0.01).The L2-fed calves had a higher incidence of depression than those fed L1(P < 0.01).The L2WP2 treatment had a superior rumen papillae length than other treatments(P < 0.01).The L1WP2 treatment had a higher ileum villus length than other treatments(P = 0.01).Overall,the carbohydrate and protein compositions in milk replacer did not influence the growth performance in calves from 35 to 70 days of age;the partial substitution of lactose with starch plus glucose in milk replacer benefits in the developments of rumen and pre-weaning withers height;the partial replacement of whey proteins with plant proteins in MR improved the development of post-weaning body length.Moreover,the combined plant proteins,starch,and glucose for inclusion in milk replacer had no significant negative impact on the development of the small intestine of the calves.