Effects of dietary protein level and rumen-protected pantothenate on nutrient digestibility, nitrogen balance, blood metabolites and growth performance in beef calves

The aim of the study was to evaluate the effects of dietary different levels of crude protein (CP) and rumen-protected pantothenate (RPP) supplementation on nutrient digestibility, nitrogen balance, blood metabolites and growth performance in beef calves. Sixty Blonde d’Aquitaine × Simmental bull calves (in average 12 months of age and 354 ± 2.4 kg of body weight) were randomly assigned to four groups with a 2 × 2 factorial arrangement. Low CP (113,7 g/kg dry matter (DM)) or high CP (133,9 g/kg DM) diets were fed without or with 72 mg RPP per kg DM. The feeding experiment lasted 100 days (10 days of adaptation and 90 days of target feeding and data collection). After feeding experiment, 4 calves per treatment (still fed the same diet) were randomly selected for collection of faeces and urine from day 111 to 120. CP × RPP interactions were not observed. DM intake, average daily gain, digestibility of DM, organic matter, CP, neutral detergent fibre and acid detergent fibre, digestible N (DN), retained N (RN), DN:N intake ratio and RN:DN ratio increased, and feed conversion ratio decreased with increasing dietary CP level or RPP supplementation. Serum total protein and albumin contents increased with increasing dietary CP level or RPP supplementation. Serum urea nitrogen increased with increasing dietary CP level, but decreased with RPP supplementation. Serum concentrations of 3-hydroxy-3-methylglutarylCoA synthetase, pantothenic acid, acyl carrier protein and acetyl-CoA as well as activities of pantothenate kinase and succinyl-CoA were not affected by dietary CP level, but increased with RPP supplementation. So, nutrient utilization and growth performance were improved with increasing dietary CP level or RPP supplementation in beef calves.