Pigeon Pea Intercropped with Tropical Pasture as a Mitigation Strategy for Enteric Methane Emissions of Nellore Steers

SIMPLE SUMMARY: Intercropping tropical grasses with legumes has the potential to mitigate greenhouse gas emissions in livestock production systems. Here, we evaluate pigeon pea (Cajanus cajan (L.) Millsp.) intercropped with Urochloa spp. for feeding Nellore steers and compared it with a degraded and recovered pasture system during the rainy and dry seasons of the year. We found that including pigeon pea in grazing systems met the nutritional requirements of the animals to obtain higher gains, improving their performance while also reducing the intensity of enteric CH(4) emissions, thus contributing to the sustainability of ruminant production based on pastures. ABSTRACT: In this study, we evaluate the effects of intercropping pigeon pea (Cajanus cajan (L.) Millsp.) with tropical pastures for feeding Nellore cattle and compared animal performance and enteric CH(4) emissions with other pasture-based systems during the dry and rainy seasons of 2021. Thirty-six Nellore steers (with a body weight of 221 ± 7 kg and an age of 15–16 months) were randomly distributed in three treatments with three replicates (in paddocks of 1.5 hectares each): (1) a degraded pasture of Urochloa spp. (DEG); (2) a recovered and fertilized pasture of Urochloa spp. (REC); and (3) pigeon pea intercropped with Urochloa spp. (MIX). Enteric CH(4) emissions were estimated using the sulfur hexafluoride (SF(6)) tracer gas technique, and dry matter intake (DMI) was determined using internal (iNDF) and external (TiO(2)) markers. Forages were collected by hand plucking after observations of ingestive behavior, and feces was collected after voluntary defecation. The proportion of grass and legume intake was estimated by C stable isotopes, and the forage nutritional quality was determined, while animal performance was monitored monthly, and the stocking rate was adjusted by the “put and take” technique. The results indicated that intercropping pigeon pea with tropical grasses is an interesting strategy for sustainable livestock production based on pastures. The MIX treatment was able to meet the nutritional requirements of the animals, which presented higher performance. In addition, there was a reduction in CH(4) emissions up to 70% when expressed per average daily weight gain in comparison to the DEG treatment.