Physiological responses, body temperature, enteric methane and ruminal microbiota of lambs fed sugarcane silage and Tithonia diversifolia

Abstract This study evaluated the effects of replacing sugarcane silage with Tithonia diversifolia silage on physiological responses, body temperature, enteric methane (CH 4 ) production, and selected ruminal microbial populations of lambs raised under tropical conditions. Twenty uncastrated crossbred lambs (½ Santa Inês × ½ Dorper), approximately 120 days old and with an initial body weight of 25.74 ± 2.47 kg, were assigned to two dietary treatments: exclusive sugarcane silage (SCA) or a 50:50 mixture of sugarcane silage and T. diversifolia silage (SCA + TD). Diets were formulated with a 60:40 forage-to-concentrate ratio. Physiological parameters, surface and infrared temperatures, enteric CH 4 production, and ruminal microbial populations were evaluated. Data were analyzed using mixed models in R software. Lambs fed SCA showed greater respiratory rate (RR) and higher surface and infrared temperatures in most evaluated body regions compared with lambs fed SCA + TD ( p < 0.05). Rectal temperature was not affected by dietary treatment ( p > 0.05). No significant differences were observed for enteric CH 4 production variables between treatments ( p > 0.05). Dietary treatment affected Ruminococcus flavefaciens abundance, which was greater in lambs fed SCA + TD ( p < 0.001), whereas the remaining ruminal microbial populations were not affected. The inclusion of T. diversifolia in sugarcane silage improved physiological and thermoregulatory responses of lambs and increased the abundance of a fibrolytic ruminal microorganism, although it did not reduce enteric CH 4 production under the conditions evaluated in this study.