Effect of supplementation of roasted oilseeds and phytochemical-rich herbages on nutrient utilization, methane emission, and growth performance in finisher lambs

Ruminal methanogenesis is a major contributor to global environmental pollution in the agriculture sector. Dietary intervention modestly abates enteric methane emissions in ruminants. Therefore, the present experiment was conducted to evaluate the combined effect of dietary oilseeds and phytochemical-rich herbages on enteric methane emission, growth performance, and nutrient utilization in lambs. Forty-eight finisher Malpura lambs were divided into 4 groups (RSZ, RSP, RSLZ, and RSLP) of 12 each in a factorial design. Lambs were fed ad libitum concentrate formulated with roasted soybean (RS) or roasted soybean plus linseed (RSL) along with Ziziphus nummularia (Z) or Prosopis cineraria (P) leaves as roughage sources. Variation in the source of roughage significantly affected feed intake, and it was higher ( P < 0.05) in lambs fed Prosopis cineraria leaves (RSP and RSLP). The average daily gain was improved ( P < 0.05) by 28.6 and 25.0% in lambs fed Prosopis cineraria , i.e., RSP and RSLP respectively, than those fed Ziziphus nummularia leaves irrespective of concentrate diets . Overall, microbial nitrogen synthesis (MNS) was higher ( P < 0.05) in lambs fed roasted soybean (RS) than roasted soybean plus linseed (RSL); however, combination of Prosopis cineraria with both the concentrate diets increased MNS, than the combination of roasted oilseeds and Ziziphus nummularia. No significant interaction was observed in the concentration and proportion of volatile fatty acids by feeding combination of roasted oilseed and tree leaves; however, the proportion of acetic and propionic acid was higher ( P < 0.05) in the RSL group compared to RS. Methane emission per kg dry matter intake was reduced ( P < 0.05) by feeding Prosopis cineraria leaves regardless of concentrate mixture. As a result, the loss of metabolizable energy through methane emission was lowered by 0.7 and 4.6% when Prosopis cineraria leaves were combined with roasted soybean (RSP) and roasted soybean plus linseed (RSLP), respectively. From the present findings, it can be concluded that combination of Prosopis cineraria leaves either with roasted soybean or roasted soybean plus linseed reduced enteric methane emissions more effectively than Ziziphus nummularia leaves, and the energy saved was transformed into higher body weight gain and improved feed conversion ratio.