Animal performance and methane emissions in feedlot vs, traditional pastoral systems with concentrate supplementation for Tanzanian Short Horn Zebu and Boran cattle

The current study examined the effect of concentrate supplementation on beef cattle performance and methane (CH 4 ) emissions in traditional pastoral systems in Tanzania. The study used summarized data (least square means, SEM, n) from a previous experimental study conducted in Tanzania in 2007-08, as the raw data are not available. The experiment involved 60 Boran and 60 Tanzanian Shorthorn Zebu (TSHZ) cattle, assigned to five dietary treatments for 100 days: grazing alone (GrazC00), grazing with 50% concentrate (GrazC50), and ad libitum hay with 60%, 80%, and 100% concentrate supplementation (HayC60, HayC80, and HayC100, respectively). The concentrate levels (50%, 60%, 80%, and 100%) were determined relative to the ad-libitum concentrate intake established before the experiment. The experiment measured dry matter intake (DMI) and live weights throughout the experimental periods. The current study calculated average daily weight gain (ADG) and daily CH 4 production (DMP) following the 2019 Refinement to the 2006 Intergovernmental Panel on Climate Change (IPCC) guidelines. The estimated CH 4 emissions were then used to calculate emission intensity (EI) relative to weight gain (EI WG, g CH 4 /kg WG). Statistical analysis used the lme4 package in R and the lm function to fit ANOVA with breed and treatment main effects and their interaction, with significance set at p < 0.05. Results showed that concentrate supplementation increased ADG by 6%–33% and decreased DMP by 3%–35%, regardless of breed. Among treatments, HayC100 had the lowest DMP, indicating greater efficiency at higher concentrate levels. In both breeds, EI decreased as concentrate levels increased from 0% to 100%, with the lowest EI WG observed in the HayC100 treatment (from 396 at GrazC00 to 87 g CH 4 /kg WG at HayC100). The reduction in EI WG was consistent across both breeds, showing that the supplementation effect was similar regardless of breed differences. Overall, concentrate supplementation improved cattle performance and reduced DMP, due to decreased CH 4 conversion factor (Ym), and lower EIs. These findings suggest that concentrate supplementation could be an effective strategy for enhancing beef production efficiency and reducing environmental impact in Tanzania.