ESTIMATION OF ENTERIC METHANE EMISSIONS IN SMALL-SCALE BOVINE MILK PRODUCTION SYSTEMS UNDER DIFFERENT FEEDING STR

Abstract

Background: Small-scale dairy systems are a development option, and in Mexico they represent over 78% of dairy farms providing 37% of milk production. They are a source of employment and income in rural areas that enable dairy families to overcome poverty. However, ruminant production systems emit 17% of world methane, a greenhouse gas that affects climate change. Strategies must be devised to reduce the environmental footprint of dairy systems through increase productivity. Objective: The objective was to estimate the methane emission from enteric fermentation in small-scale dairy systems in the highland valleys of central Mexico with four feeding strategies. Methodology: Twenty four small-scale farms, with herds between 7 and 18 dairy cows participated in the study, which had implemented different feeding strategies that were assigned to the following groups: (CC) five farms that had a conventional management based on the cut-and-carry of temperate irrigated pastures, use of concentrates and straw, (CC+EM) six farms that use cut-and-carry of pastures plus maize silage in the dry season, (PCI) six farms that manage intensive continuous grazing of pastures, (PCI+EM) seven farms with continuous grazing of pastures, and use maize silage in the dry season. Farms were visited monthly during a whole year to record individual milk yields, milk composition and live weight of cows, to sample feeds for chemical analyses and record amounts of used feed. This information enabled to define a diet type per month, and dry matter and gross energy intakes were estimated subtracting the energy contribution of the supplements from total requirements. Methane emissions were estimated from a model derived by a global meta-analysis that includes variables of feed intake, diet composition, milk composition, and cow live-weight. A hierarchical experimental design was used where 288 records were subjected to analysis of variance to detect differences among the groups (alpha P≤0.05).  Results: Farms that implemented grazing of pastures as a source of fresh quality herbage (PCI) in mean generated 10.5% less enteric methane and 13.9% les intensity of emission (P<0.05) compared with those that incorporated cut and carry or implemented corn silage for the dry season. Implications: Results show the potential of small-scale dairy systems to reduce their methane emissions and intensity of emissions by implementing grazing of temperate irrigated pastures. Conclusions: The implementation of fresh quality herbage through continuous grazing of temperate irrigated pastures with the use of moderate supplementation without incorporation of corn silage is a viable methane mitigation strategy in small-scale dairy systems in the highlands of Mexico.