Comparing the efficacy of forage combinations with different hydrolysable and condensed tannin levels to improve production and lower methane emission in finisher lambs

For determining the efficiency of forage combinations with varying tannin levels in small ruminants, an experiment was conducted on 36 finisher Malpura lambs. Animals were divided into 3 groups (T1, T2 and T3) of 12 each and fed ad libitum complete feed blocks consisting 65, 30 and 5 parts concentrate, roughage and molasses, respectively.The roughages added were 15 parts Vigna sinensis hay and 15 parts Ziziphus nummularia leaves in T1, 15 parts Vigna sinensis hay and 15 parts Acacia nilotica leaves in T2, 15 parts Ziziphus nummularia leaves and 15 parts Acacia nilotica leaves in T3 feed blocks. The content of total tannin was 0.78, 2.37 and 2.9 (g/100 g dry matter) in feed blocks of T1, T2 and T3 group, respectively. Dry matter intake was reduced (P < 0.05) with increasing level of tannins in the diet. Nutrient digestibility and balance of nitrogen were higher in lambs of T2 group as compared to T3. However, total volatile fatty acid production and population of methanogens and protozoa were reduced in T2 and T3 groups than T1. Loss of metabolizable energy through methane was 3.1 and 1.8% lower in T2 and T3, respectively than T1 which subsequently resulted in higher (P < 0.05) microbial nitrogen synthesis in T2 and T3 groups. The average daily gain and feed conversion ratio was significantly improved in T2 and T3 groups as compared to T1. In Longissimus thoracis muscle, higher (P < 0.05) content of n-3 fatty acids was observed in T2 and T3 groups, whereas in adipose tissue lower (P < 0.05) content of saturated fatty acids and higher (P < 0.05) mono unsaturated fatty acids were found in T2 group. From the present findings it can be concluded that feeds blocks consisting Vigna sinensis hay and Acacia nilotica leaves with tannin level of 2.37% is most promising in terms of methane mitigation, higher microbial nitrogen synthesis and weight gain, improved feed conversion and enhanced functional carcass attributes in finisher lambs.