A Monitoring Study on the Production Performance and Enteric Methane Emission from the Dairy Cows Under Smallholder Farms in Kilimanjaro Region, Tanzania

A total of 54 lactating dairy cows from 20 farms in Hai District were monitored to assess production performance and methane (CH<sub>4</sub>) emission under different feeding practices and altitude zones. Of the selected farms 8 were in the highland zone and 12 in the lowland zone. In the lowland, cows were managed under zero grazing (FP1), grazing with supplementation (FP2) and extensive grazing (FP3), while all highland cows were managed under FP1. Measurements included body weight, nutrients intake, milk yield and composition and CH<sub>4</sub> emission. Feedstuffs were also analysed for their nutritive values. The results showed that, daily dry matter intake (DMI), crude protein intake (CPI) and metabolisable energy intake (MEI) were higher (P<0.05) in cows under FP1 (11.1 kg, 1.2 kg and 117 MJ, respectively) than those in FP2 (9.8 kg, 938 g and 90 MJ) and FP3 (7.5 kg, 539 g and 45.3 MJ). Similarly, cows in the highland zone had higher (P<0.05) DMI, CPI, and MEI (11.7 kg, 1.3 kg, and 121.9 MJ) than those in the lowland zone (11.1 kg, 1.18 kg, and 117.1 MJ). Weight gain was highest (P<0.05) in FP1 (0.35 kg/d), followed by FP2 (0.21 kg/d), and lowest in FP3 (0.11 kg/d). Cows in the highland zone had significantly higher weight gain 0.46 kg/d) compared to those in the lowland zone 0.35 kg/d). Daily mean milk yield followed a similar trend, with cows under FP1 producing the highest (9.0 kg), followed by FP2 (6.8 kg) and FP3 (4.7 kg). Across zones, milk yield was significantly higher (P<0.05) in the highland (11.2 kg) than in the lowland (9.0 kg). Milk from cows under FP3 had slightly higher (P<0.05) lactose content (4.4%) than those under FP1 and FP2, while cows under FP1 produced milk with higher solids-non-fat (SNF) content (8.5%). Milk from lowland cows contained more (P<0.05) fat (4.0%), protein (3.6%), total solids (12.0%) and solids-non-fat (8.5%) than milk from highland cows. Mean gross methane emission did not differ significantly among feeding practices but was higher (P<0.05) in the highland zone (265 g/d) than the lowland zone (149.9 g/d). Methane intensity was similar (P>0.05) across feeding practices and zones. It was concluded that cows under FP1 achieved higher production performance by producing higher milk yield per unit of methane emitted compared to other feeding practices. Further research is recommended to evaluate the effects of different supplementation levels on production performance and methane emission.