Increased productivity in Tanzanian cattle is the main approach to reduce methane emission per unit of product

Abstract

Reduction in emission of the greenhouse gas methane is a major global goal, and ruminants are major contributors to methane emission. It is well known that increased productivity will reduce the methane emission per unit of product, but its immense quantitative importance under Tanzanian conditions may not be realised. The aim of this study was to compare the present situation (M0, F0) with two improved scenarios, one where weight gain until maturity is improved by 100 g/day for both male and female (M100-F100), and one where male gain is improved by 200 g/day and female by 100 g/day (M200-F100). Scenario calculations were based on 2003 statistics for Tanzanian cattle number and herd composition, on IPCC (2006) equations for feed energy requirements and methane emission, and on several assumptions to simplify scenario calculations, e.g. that all cattle are Tanzania Short Horn Zebu (TSHZ). Present weight gain was assumed to be 115 g/day for both males and females, and mature weight to be 280 kg for female and 300 kg for male. Increased growth rate reduced total stock number as slaughter weight was reached earlier, but birth of a similar number of calves per year in all scenarios was assured by number of female breeding stock. For scenario M0-F0, M100-F100 and M200-F100, total number of cattle were 17.0 (based on 2003 statistics), 14.6 and 13.7 million, total feed requirement in NE were 312, 351 and 354 million MJ/day, total kg of carcass meat harvested were 163, 246 and 264 million kg/year, and total methane emission were 588, 561 and 520 million kg/year. NE requirement was 699, 522 and 488 MJ/kg carcass, and methane emission was 3.61, 2.28 and 1.96 kg/kg carcass for scenario M0-F0, M100-F100 and M200-F100, respectively, equivalent to a reduction of 37% and 46% of the two scenarios compared to the present situation. In conclusion, the potential for improving productivity and reducing methane emission at the same time in Tanzanian cattle production is immense.