Dietary inclusion of mature lemon grass and curry leaves affects nutrient utilization, methane reduction and meat quality in finisher lambs

Abstract

Meat production from ruminants is allied with huge environmental cost that needs to be addressed for sustainable animal agriculture. Nutritional interventions based on use of plant bioactive rich human inedible biomass in animal diets may be a potential strategy for eco-friendly and quality meat production. Therefore, the present experiment is aimed for methane mitigation and functional meat production by incorporating mature lemon grass (Cymbopogon citratus) and curry leaves (Murraya koenigii) in the diet of finisher lambs. Thirty six male Malpura lambs (∼ 4 months age) were divided equally into three groups (C0, T1 and T2) and fed ad lib complete feed block consisting of concentrate, molasses and roughage in the ratio of 55:5:40 for a duration of 3 months. Roughage in the control diet was black gram (Vigna mungo) straw whereas, in the treatment diets 10 percent black gram straw was replaced by dry chaffed mature lemon grass and curry leaves in T1 and T2, respectively. Digestibility of dry matter and hemicellulose was improved (P < 0.05) in T2 along with higher (P < 0.05) N balance. Rumen fermentation parameters showed higher (P < 0.05) propionic and lower (P < 0.05) acetic acid in lambs of T2 group. In case of rumen metagenomic analysis, higher population (P < 0.05) of Butyrivibrio fibrisolvens and lower population (P < 0.05) of methanogenic archaea and total protozoa was observed in lambs fed mature curry leaves. Consequently, enteric methane emission was lower (P < 0.05) by 12.6 percent per kg organic matter intake and microbial N synthesis was improved (P < 0.05) by 15 percent in lambs fed blocks consisting of matured curry leaves than control. Daily gain was higher by 9.9 percent and feed conversion ratio was improved by 6.5 percent in lambs fed T2 blocks compared to control however, results in mature lemon grass fed lambs were at par to that of control. Analysis of Longissimus thoracis (LT) muscle showed higher (P < 0.05) C18:1n9c, C18:2c9t11 CLA (conjugated linoleic acid) and lower C18:0 contentinT1 and T2 groups than C0. Likewise, adipose tissue showed similar trend like LT muscle except CLA content along with lower thrombogenic index (TI) in lambs of T1 and T2 groups than C0. Hence, from the present findings it can be concluded that among both the unconventional feed ingredients, dietary inclusion of 10 percent mature curry leaves has a dual impact on environmental sustainability and meat quality attributes in ruminant production.