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<p><strong>Background: </strong>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. <strong>Objective: </strong>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. <strong>Methodology: </strong>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).  <strong>Results</strong>: 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&lt;0.05) compared with those that incorporated cut and carry or implemented corn silage for the dry season. <strong>Implications:</strong> 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. <strong>Conclusions:</strong> 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.</p>

In dairy production systems, the efficient use of resources is required to guarantee its sustainability. Worldwide, the efficiency of feed utilization and its effects have been widely studied. However, few studies have quantified animal nitrogen use and its corresponding soil contribution in small-scale production systems. Therefore, this study aimed to determine the efficiency of feed utilization and quantify the soil chemical composition in small-scale production systems using two different feeding strategies. Twelve dairy farms were evaluated from May 2016 to April 2017. Data analysis was performed using an ANOVA following a completely randomized model and using feeding strategies as treatment. Regarding the feeding systems' characteristics, significant differences (P < 0.05) were only observed in land surface and land used to produce mixed-grass and corn. Nitrogen (N) input and output in dairy cattle were significantly different (P < 0.05) for crude protein intake. The highest results were observed in grazing feeding systems. The cut and carry strategies excreted 71% of the consumed N in the manure; grazing strategies excreted 72%. The efficiency of feed utilization (EFU) is low; only 19% of the consumed N is recovered during milk production. As for the soil chemical composition, significant differences (P < 0.05) were observed in the percentage of total N and the carbon to nitrogen (C:N) ratio. The remaining components behaved similarly in both feeding systems. Systems that include crops and livestock can positively change the biophysical and socioeconomic dynamics of agricultural systems.

Livestock production in some tropical regions is characterized by the use of naturalized forages in extensive management with low production rates. The use of improved grass-legume associations represents a sustainable intensification opportunity for this type of agroecosystems. The objective was to evaluate the production in establishment of forage associations for grazing systems in the dry tropics of Colombia. In a randomized complete block design with slope as the block factor and experimental units of 2700 m2 with four replications, the agronomic and nutritional quality characteristics of six treatments were compared: Urochloa hybrid cultivar Mulato II, U. brizantha cultivar Toledo and Megathyrsus maximus cultivar Mombasa, established alone or associated with Canavalia brasiliensis, against the control Dichantium aristatum, a naturalized forage of the region. Mulato II, Toledo and Mombasa alone and in association showed greater (p ≤ 0.05) vigour, height, cover and forage production than the control. Mombasa produced 10.7 Mg ha-1 MS (Megagrams of dry matter per hectare), exceeding (p ≤ 0.05) by 74, 53 and 84 % that were recorded in Mulato II, Toledo and control, respectively. C. brasilienses promoted higher productivity in the association with Mulato II and improved nutritional characteristics in the associations with Toledo and Mombasa compared to specific monocultures and the control. The improved grasses alone or associated with C. brasiliensis were a better forage option than Dichantium aristatum. It was concluded that M. maximus and Urochloa hybrid associated with C. brasiliensis are relevant forage options for agroecologically similar regions to the Colombian dry tropics.