Nature of Carbohydrates in Agro-industrial By-products (AIBP) Scarcely Support Rumen Microbial Protein Production but Sustain Milk Composition

Abstract

Background: The microbial protein (MBP) production in rumen has quantitative influence on protein availability to host animal and also influence milk composition, particularly milk protein. Few native breeds produce low levels of milk that should sustain economically on agro-industrial by-products (AIBP). However, the nature of carbohydrates in AIBP how far support the MBP in rumen is seldom quantified. The objective of the study was to evaluate the cell wall carbohydrates of AIBP as a source of energy for rumen MBP production and milk composition in Bos indicus cows. Methods: Twenty Deoni breed cows in mid-lactation were divided in complete randomized block design into 5 groups of 4 each based on milk yield, body weight, parity and days in lactation. Basal roughage was finger millet straw ad-lib. The cows in treatment groups were supplemented with wheat bran (T1), or hyacinth bean grit (T2), or soy husk (T3), or 50% green gram grit plus 50% pigeon pea husk (T4) and compared with a control group (CG) supplemented with sorghum grain. All the supplements were made 18% isonitrogenous with commercial urea and fortified with 2% common salt and 3% minerals and vitamins mix. The diets were fed for 7 weeks including a digestibility trial of 5 days duration. Result: Total diet intake was comparable between CG and TGs. CP, hemicelluloses, celluloses (P≤0.01) and, EE (P≤0.05) digestibility were higher in TGs than CG. Energy efficiency was comparable between grain and AIBPs. Rumen MBP was lesser in TGs than CG. Higher rumen MBP among TGs was observed in T4 (180 g d-1) but it was 45 g d-1 lesser than CG. Milk total solids (TS), fat and solids-non-fat (SNF) were comparable between CG and TGs. The coefficient of variation in daily milk yield was reduced in TGs. The concentrate supplement with 50% grit and 50% husk combination was only suitable to moderately sustain rumen MBP production and also support milk production otherwise, AIBP as the sole concentrate supplement had limited benefit for rumen MBP production.