Methane production and microbial protein synthesis in adult sheep fed total mixed ration as mash and as complete feed block

Abstract

Tree leaves of Ailanthus excelsa, Ziziphus nummularia and Prosopis cineraria were fed in complete feed block (CFB) to 36 weaner (91 d) lambs distributed equally (20.6 ± 0.55 kg) in three groups (T1, T2 and T3). The CFB of T1 consisted of 40% A. excelsa leaves, which was replaced at 50% level with phytochemical rich Z. nummularia leaves in T2 and P. cineraria leaves in T3. There was decline (p<0.05) in methane emission per kg digestible OM intake by 10.7 and 15.5% in T2 and T3 compared to T1. Rumen fermentation pattern showed an increased trichloroacetic acid precipitable N with decreased ammonia N and ciliate protozoa population in T3 compared to other two groups. Ruminal microbial protein synthesis as assessed from urinary purine derivatives excretion was higher (p¼0.012) in T3 than T1, while T2 had an intermediate value. There was decreased (p<0.05) digestibility of dry matter, organic matter (OM) and ADF in T3, and that of crude protein (CP) and NDF in both T2 and T3. Lambs in T1 and T2 had higher (p<0.05) intake of digestible OM, metabolizable energy (ME) and digestible CP than T3. There was improved (p¼0.038) N utilization efficiency with a reduced (p¼0.041) excretion through urine, but increased (p¼0.004) excretion through feces in T2 and T3 compared to T1. The live weight gain was lower in T3 compared to T1 with an intermediate performance in T2, but feed conversion ratio with respect to digestible OM and ME intake was similar in all the three groups. It is inferred that inclusion of Z. nummularia and P. cineraria leaves in CFB reduced methane emission, improved ruminal attributes including microbial protein synthesis and N utilization, but lower digestibility and ME intake lead to lower gain. Thus, ration with phytochemicals-rich tree forages would support finished lamb production under greener environment.