Cow performance and methane emissions from sorghum silage diets in small-scale dairy systems of Central Mexico
摘要
Climate change generates reduced rainfall or increased dry spells, a challenge for the sustainability of small-scale dairy systems (SSDS). Sorghum silage may be an alternative in the highlands, as sorghum is more resistant than maize to dry conditions and its tannin content may reduce methane emissions. The objective was to evaluate sorghum silage for dairy cows in SSDS in performance and estimated methane emissions. Eight Holstein cows were assigned to two treatments in a continuous design for 28 days. Cows on maize silage treatment (MSL) were offered 9.5 kg DM/cow/day of maize silage, while cows on sorghum silage (SRG) received 7.6 kg DM sorghum silage + 1.9 kg DM maize silage/cow/day. Cows also received 3.6 kg DM/cow/day of a commercial concentrate, 2.4 kg DM of alfalfa hay, and 2.4 kg DM/cow/day of maize straw. Milk yield, milk fat and protein content were recorded, feed chemical composition determined, and enteric methane emissions estimated. Inclusion of sorghum silage in the diet did not affect milk or 3.5% FCM yield (P > 0.05), but reduced milk fat content and dry matter intake (P < 0.05). The nutritive value of sorghum silage was higher than maize silage, resulting in increased (P < 0.05) estimated CH4 emissions for MSL, but no differences in CH4 yield (g/kg DM) or intensity (g/kg 3.5% FCM), but with higher (P < 0.05) energy lost as methane and in terms of CO2 equivalent per kg of 3.5% fat corrected milk in MSL. In conclusion, under the on-farm experimental conditions, sorghum silage may be a forage alternative for small-scale dairy systems the highlands of central Mexico, with no significant differences in the productive performance of dairy cows, but with lower methane emissions.