Effect of ruminally protected fat on in vitro fermentation and apparent nutrient digestibility in buffaloes (Bubalus bubalis)

Abstract 

Experiments were conducted to evaluate effects of supplementation of calcium salts of long chain fatty acids (Ca-LCFA) as a rumen inert fat (PF) on in vitro fermentation and apparent nutrient digestion in adult buffaloes fed wheat straw based diets. For the in vitro fermentation study, five total mixed rations (TMR) consisting of a concentrate mixture (CM), green Sorghum bicolor, WS and supplemented without (C) or with 30g/kg dry matter (DM) rice bran fatty acid oil (RBO) (30 RBO) or 20g/kg RBO+10g/kg PF (20 RBO/10 PF) or 10g/kg RBO+20g/kg PF (10 RBO/20 PF) or 30g/kg PF in the DM in the ratio of 340:50:580:30 were prepared. The in vitro DM degradability (IVDMD), TN, trichloro acetic acid precipitable N (TCA-N), non-protein N (NPN) and ammonia N (NH₃-N) were similar among groups. Within the fat supplemented groups, total volatile fatty acid (TVFA) concentration increased linearly (P=0.025) with PF supplementation. Apparent nutrient digestibility was determined on 20 adult buffaloes divided into five equal groups fed CM supplemented without (C) or with 300g RBO (30 RBO) or 200g RBO+100g PF (20 RBO/10 PF) or 100g RBO+200g PF (10 RBO/20 PF) or 300g PF (30 PF) along with limited green S. bicolor and WS maintaining forage: concentrate ratio of 650:350. Fat supplementation had no effect on the DM intake and apparent digestibilities of DM, organic matter (OM), crude protein (CP), total carbohydrate (TCHO) and neutral detergent fiber (aNDF). Within fat supplemented groups, inclusion of PF increased digestibilities of DM, OM, ether extract (EE), TCHO, aNDF and ADF. Supplemental fat also increased the digestible energy (DE) and metabolizable energy (ME) content of the diet, which also increased linearly with PF supplementation. All buffaloes were in positive N, Ca and P balances. We conclude that 200–300g supplemental PF in the form of Ca-LCFA can be included in straw based diets fed to buffaloes to increase its energy density without adversely affecting DM intake and digestibility.

Abbreviations: ADF, acid detergent fiber expressed inclusive of residual ash, aNDF, neutral detergent fiber assayed with heat stable amylase and expressed inclusive of residual ash, BW, body weight, Ca-LCFA, calcium salts of long chain fatty acids, CM, concentrate mixture, CP, crude protein, DE, digestible energy, DM, dry matter, DMD, DM degradability, EE, ether extract, IVDMD, in vitro DM degradability, ME, metabolizable energy, NH₃-N, ammonia N, NPN, non-protein N, OM, organic matter, PF, ruminally protected fat, RBO, rice bran fatty acid oil, RL, rumen liquor, SRL, strained rumen liquor, TA, total, ash, TCA-N, trichloro acetic acid precipitable N, TCHO, total carbohydrate, TMR, total mixed ration, VFA, volatile fatty acids, WS, wheat straw

Keywords: Concentrate mixture, Protected fat, Rice bran fatty acid oil, Total mixed rations