Effect of Dietary Supplementation on Milk Nutrient Deposition and Enteric Methane Emission in Dual-Purpose Cows from the Colombian Amazon

Dual-purpose livestock farming in the Colombian low tropics faces nutritional limitations that affect productivity and increase enteric methane (CH4) emissions. Therefore, it is necessary to evaluate supplementation strategies that optimize the use of nutrients and reduce environmental impacts. The objective of this study was to evaluate the effects of three types of dietary supplementation—mineralized salt (MS), proteinized salt (PS), and concentrated feed (CO)—on milk production, efficiency in the deposition of dairy nutrients, and enteric CH4 emissions in dual-purpose grazing cows in the Colombian Amazon. Twenty-four F1 Holstein × Gyr cows were used in a completely randomized block design. Nutrient intake, digestibility, composition, and efficiency in the milk deposition of Ca, P, K, and N were measured; additionally, CH4 emissions were assessed using a portable electronic spirometry mask. The results indicated that the treatments did not modify the total intake of dry matter or the production and composition of milk. CO and MS supplementation improved the efficiency of Ca and P (p < 0.03) deposition in milk, while no differences were observed for N and K. CH4 emissions (196 ± 17.9 g/cow/day) were not affected by the supplements and were within the ranges reported for dual-purpose tropical systems. However, with the supplementation with CO was a lower losses of gross energy intake as CH4 (Ym) (p < 0.05). In conclusion, supplementation with the evaluated products did not impact milk production or CH4 emissions, although with CO was lower energy losses as CH4 and, CO and MS improved the use of Ca and P, which highlights the importance of adjusting supplementation to optimize nutritional efficiency without increasing greenhouse gas emissions.