The Effect of Monensin vs. Neem, and Moringa Extracts on Nutrient Digestibility, Growth Performance, Methane, and Blood Profile of Merino Lambs

SIMPLE SUMMARY: Modulating the rumen environment can help to improve the efficiency of feed utilization, minimize methane gas production, or improve the overall health of the animals. Leaf extracts of Moringa and Neem plants were tested as potential phytogenic rumen modulators in growing merino lambs while also evaluating the effect on the performance and health of the animals. The doses tested did not have any negative effect on the health and performance of the animals. However, the leaf extracts from Moringa and Neem tended to reduce methane emissions, and thus necessitating testing of higher inclusion levels and standardization of the plant extract using key bioactive compounds associated with methane inhibition. ABSTRACT: Plant secondary compounds are potential rumen modifiers that can improve nutrient utilization in ruminant animals. This study evaluated the effect of Moringa (Moringa oleifera) and Neem (Azadirachta indica) leaf extracts on nutrient digestibility, growth performance, and enteric methane production in South African Mutton Merino lambs. Forty 4-month-old ram lambs with a mean body weight of 35 ± 2.2 kg were blocked by weight and from each block, lambs were randomly allocated into one of the following treatments: (i) diet only (fed a total mixed ration TMR-negative control), (ii) Monensin (fed TMR containing Monensin sodium, 15 mg/kg DM), (iii) Moringa (fed TMR, drenched with Moringa extract 50 mg/kg feed DM intake), and (iv) Neem (fed TMR, drenched with Neem extract 50 mg/kg DM intake). Extracts were administered via oral drenching at a concentration determined based on the previous week’s feed intake. There were no differences in dry matter intake, average daily gain, feed conversion efficiency, digestibility, and nitrogen retention across the treatments. However, the extracts tended to reduce methane emitted both in g/head/day (p < 0.08) and g/ kg dry matter intake (p < 0.07). Extracts did not influence any of the blood metabolites in the ram lambs. Although the benefits of utilizing these medicinal plants as rumen modifiers under prolonged feeding conditions is justified, further evaluation is recommended to test Moringa and Neem leaf extracts at higher inclusion levels. Our research group is currently exploring a variety of phytogenic tools for the identification and standardization of key bioactive compounds linked to methane inhibition, in these leaf extracts.