Int.J.Curr.Microbiol.App.Sci (2018) 7(11): 2257-2266 2257 Original Research Article https://doi.org/10.20546/ijcmas.2018.711.253 Effect of Variable Protein and Energy Diet on Purine Derivatives Excretion and Quantitative Microbial Protein Production in Crossbred and Indigenous Calves Ajay Singh 1* and Bandla Srinivas 2 1 Animal Nutrition, College of Veterinary Sciences (Sri Venkateswara Veterinary University), Proddatur – 516360, Andhra Pradesh, India 2 I/c Dairy Production Section, Southern Regional Station ICAR-NDRI, Bengaluru – 560030, Karnataka, India *Corresponding author ABSTRACT Introduction Nutrition is the primary entity to be look after for better body growth. Faster growth entails more amounts of nutrients input through the diet. Often growth slumps immediately after weaning due to shift in nutrition from high density nutrient diet to roughage-based diet with supplements. And also, nutrition is all too often neglected between weaning and 9 months of age. Weaning to 9 months of age is a critical time in the life of a calf and is a time of higher nutrient requirements. As rumen capacity is limited during this period, a diet high in protein and energy content should be provided. In absence of adequate nutrition, the average daily weight gain (ADG) of calves would be less than genetic potential and fails to obtain required body weight as per the age. Insufficient growth rates result in an older age at first calving (Van Amburgh et al., 2008) which ultimately affects the overall productive life of the animal. Diet with CP content of 17 to 18% (DM basis) is recommended for calves International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 7 Number 11 (2018) Journal homepage: http://www.ijcmas.com Study was conducted to evaluate the effect of enhanced level of nutrition on nutrient intake and microbial protein (MBP) production of two genotypes; Deoni and HF crossbred calves. Treatment groups of Deoni (DTG) and HF crossbred (XTG) were fed 30% more protein and energy as compared to their respective control groups (CGs). Dry matter intake (DMI) of DTG was reduced by 18% in comparison to DCG. Crude protein (CP) intake in DTG was 312 g/d and was higher by 14% compared to DCG. Whereas, CP intake in XTG was 38% more compared to XCG. Gross energy (GE) intake by DTG was 8.13 Mcal/d compared to 9.70 Mcal/d of DCG. The MBP production in XCG, XTG, DCG and DTG was 239, 229, 143 and 142 g/d, respectively. Quantitative availability of MBP was constant and related to size of the calf. This indicated that the DMI in Deoni calves was regulated by the nutrient density of diet indicating towards the low level of phenotypic plasticity of digestive system in Deoni calves providing less scope for productive improvement by nutritional intervention compared to HF crossbred calves. Keywords Nutrient intake, Genotypes, Phenotypic plasticity, Microbial protein Accepted: 18 October 2018 Available Online: 10 November 2018 Article Info