Effects of monensin feeding on performance, nutrient utilisation and enteric methane production in growing buffalo heifers.

Murrah buffalo heifers (live weight 135 ± 17 kg) were fed a total mixed ration without supplementation (CON), or supplemented with sodium monensin (MON; Rumensin® 200, Elanco Animal Health, Brazil) @ 0.6 mg/kg of body weight for 90 days. Nutrient digestibility and nitrogen retention were estimated during the mid-experiment, and enteric methane production was measured by sulphur hexafluoride tracer technique for consecutive-5 days after the digestion trial. The dry matter (DM) and nutrient intake were not affected but DM intake expressed as percent of body weight was decreased by monensin supplementation (3 vs 2.7% for CON and MON, respectively). The crude protein digestibility was higher for MON whereas, digestibility of other nutrients was not affected. Nitrogen retention (+ 4.59 g/day) and daily body weight gain (+ 56 g/day) were greater for MON-fed heifers without any significant effect on nitrogen intake and nitrogen excretion through faeces and urine. Daily enteric methane production was reduced by 12.61% but the treatments did not differ significantly. Methane emission expressed as gram per unit of DM, organic matter and digestible DM intake was lower for MON than CON and methane conversion rate (Ym) % of GE and ME intake was also decreased by 8-9%. On day 60, blood glucose level was increased and urea nitrogen was decreased in MON-fed heifers. This study indicated that monensin supplementation at 0.6 mg/kg body weight in growing heifers improved daily gain and feed efficiency while it reduced enteric methane production which can reduce feedlot time and consequent life time CH4 production.

Growth performance, and enteric and manure greenhouse gas emissions from Murrah calves fed diets with different forage to concentrate ratios.

The present study investigated the effects of different dietary forage to concentrate ratios on animal performance, and enteric and manure greenhouse gas emissions in growing calves. Fifteen male Murrah calves (153.5 ± 18.17 kg; 6 to 12 months) were randomly assigned to 3 dietary treatments and fed corn fodder, wheat straw and concentrate in 3 different proportions: 20:60:20 (C20); 20:40:40 (C40) and 10:30:60 (C60), for a period of 120 days. Increasing dietary concentrate proportion had no significant (P > 0.05) effect on dry matter intake (DMI) but increased crude protein (CP) and total digestible nutrient intake (P < 0.05). Average daily gain and feed conversion efficiency were significantly higher (P < 0.05) for C60 compared with C20 and for C40, these did not differ with C20 and C60 (P > 0.05). The apparent digestibility of dry matter, organic matter and CP were higher (P < 0.05), but acid detergent fiber digestibility was lower (P < 0.05) for C60 compared with C20 whereas, ether extract and neutral detergent fiber digestibilities were not affected (P > 0.05). Daily methane (CH4) emission (g/d), CH4 energy loss (MJ/d) and CH4 yield (CH4 g/kg organic matter intake [OMI], CH4 g/kg digestible OMI, and CH4 % of metabolizable energy intake) were significantly higher for C20 compared with C60 (P < 0.05). Methane yield as g/kg DMI although lower for C60 compared with C20 but the difference was not significant (P > 0.05). Manure CH4 (g/kg DMI) and nitrous oxide (N2O mg/kg nitrogen) emissions were not affected (P > 0.05), but N2O emission on mg/kg DM basis was significantly higher (P < 0.05) from the manure of calves fed C60 than that for C20. Thus, increasing dietary concentrate proportion improved animal performance, and reduced enteric CH4 emission (g/day) without any significant effect on manure N2O (mg/kg nitrogen) and CH4 emissions.