Methane emissions and milk yields from zebu cows under integrated systems

Abstract

Integrated systems are technologies that potentially increase animal production and environmental preservation, but the effect of these systems on the efficiency and methane emissions of dairy cows is still unknown. This study aimed to compare enteric methane emissions, dry matter intake and performance of grazing dairy cows in integrated systems in the Brazilian Cerrado biome, i.e., crop-livestock integration (CLI) or crop-livestock-forest integration (CLFI). Eighteen Holstein-Zebu cows were randomly assigned to the two production systems (n = 9 for each system) based on Monbasa pasture (Megathyrsus maximus cv. Mombaça; Syn. Panicum maximum) under rotational stocking management. Herbage allowance ranged from 12 to 14% body weight, and cows were supplemented with concentrated feed according to milk yield. Herbage samples were collected by simulated grazing to determine nutritional value. Milk yield was determined weekly. Herbage intake was estimated from fecal output and indigestibility of the pasture dry matter. Fecal output was estimated by the external indicator LIPE®, and dry matter digestibility was estimated by the internal indicator NDFi. Enteric methane emissions were estimated by the SF6 tracer gas technique. Data were collected in three sampling periods to characterize the rainy season, the transition from the rainy season to the dry season and the dry season. Data were analyzed in split plots, with animals within the system as the plot and seasons as the subplot. Statistical significance was considered at P < 0.05. The herbage crude protein content was 35.9% higher on average in the CLFI than in the CLI. In vitro dry matter digestibility was 16.7% lower in the CLI than in the CLFI in the rainy season. Milk yield and feed efficiency were similar between systems and seasons. The total dry matter intake in the rainy season was 34.6% higher in the CLFI than in the CLI. The energy loss, production and yield of methane were 29.8%, 35.0% and 31.3%, respectively, lower in the rainy season than in the other seasons. Enteric methane emissions, milk yield and feed efficiency were similar between the integrated CLI and CLFI systems in the Brazilian Cerrado region.