Quantification of methane emissions from Murrah buffaloes fed different energy diets during various temperature humidity index periods in a tropical environment

Abstract

The objective of the present study was to quantify the enteric methane emission in Murrah buffalo heifers at high (summer) and low (winter) temperature humidity index (THI) period fed different energy level diets. Thirty-six growing Murrah buffalo heifers of average bodyweight (158.51 ± 16.5 kg) were distributed into three groups of six animals each separated based on their bodyweight and fed for the period of 120 days each during summer (high THI, 78–85) and winter (low THI, 50–61). The animals were fed on three different levels of metabolisable energy (ME) content and the Control ration (T1) having ME content according to ICAR (2013) and T2 and T3 were having 115% and 85% ME than the Control respectively, in total mixed-based ration. The SF6 tracer gas technique was used to quantify the enteric methane emission by the animals. Methane emission (g/day) of Control and the high energy (T1 and T2) group was lower (P < 0.05) than the low energy (T3) fed group in both seasons. Methane losses as percentage of gross energy intake was lower (P < 0.01) during the winter season. However, in the low energy treatment group (T3) at both seasons these values are higher than the IPCC recommended value (6.5%) for calculation of national inventory of greenhouse gas emission from enteric sources. In between season average daily gain (kg) was higher (P < 0.01) in the winter season and among the treatment groups it was higher (P < 0.01) in the high energy group (T1, T2). Higher (P < 0.01) digestibility of dry matter, organic matter, neutral detergent fibre and acid detergent fibre was reported in the Control and high energy-fed group. Whereas in the summer season digestibility of dry matter, organic matter, crude protein and acid detergent fibre was higher (P < 0.01) than in the winter season. It can be concluded that energy levels significantly (P < 0.05) affect methane emissions and was lower in the Control and high energy-fed group (T1 and T2). However, while quantifying methane emission in changing THI period at different seasons it did not show any significant variation.