Indian Journal of Animal Sciences 93 (3): 287–292, March 2023/Article https://doi.org/10.56093/ijans.v93i3.121010 Dietary supplementation of Ficus hookeri leaves as herbal feed additive affects nutrient utilization and growth performances in growing crossbred calves A SANTRA 1* , T TAKU 2 , S TRIPURA 1 , S K DAS 1 and T K DUTTA 1 ICAR-National Dairy Research Institute, Eastern Regional Station, Kalyani, West Bengal 741 235 India Received: 2 February 2022; Accepted: 22 February 2023 ABSTRACT The objective of this study was to evaluate the efect of dietary supplementation of Da qing shu (Ficus hookeri) leaf meal as herbal feed additive on nutrients utilization and growth performance of growing crossbred calves. Ten Jersey male cross-bred calves (~ 4 months of age) were divided equally into two groups (G1 and G2) and were fed ad lib. under stall feeding on a paddy straw based mixed ration consisting of 50% paddy straw and 50% concentrate mixture for a duration of 140 days. Two types (C1 and C2) of iso-nitrogenous concentrate mixtures were prepared. Four per cent (w/w) wheat bran in concentrate mixture (C2) of test group (G2) was replaced by sun dried ground Ficus hookeri leaf meal. Experimental calves of test group (G2) were fed Ficus hookeri leaf meal @ 2% of the diet. Daily dry matter intake (g/d) was similar among the calves of two experimental groups. Apparent digestibility of DM, OM, NDF, ADF and cellulose improved in the Ficus hookeri leaf meal fed calves (G2). DCP value of the ration was similar while, TDN value of the ration was higher in the calves of Ficus hookeri leaf meal supplemented group (G2). However, plane of nutrition among the calves of both experimental groups was similar. Average fnishing body weight, daily body weight gain, feed conversion efciency and blood glucose level were higher in Ficus hookeri leaf fed calves (G2). Therefore, it may be concluded from the results of the study that dietary supplementation of Da qing shu (Ficus hookeri) leaf meal as herbal feed additive @ 2% of total mixed diet signifcantly improved the fbre digestibility, average daily body weight gain and feed conversion efciency in growing Jersey male crossbred calves. Keywords: Calves, Feed additive, Feed conversion efciency, Ficus hookeri, Growth, Nutrient utilization Present address: 1 ICAR-National Dairy Research Institute, Eastern Regional Station, A-12 Block, Kalyani, West Bengal. 2 Rajiv Gandhi University, Rono Hills, Doimukh, Arunachal Pradesh. * Corresponding author email: santraashok@redifmail. com Feed additives such as ionophores, defaunating agents, antibiotics have proved very efective in reducing dietary energy and protein losses; however, contemporary biosecurity threats have restricted their use in many European countries in animal feeds (Malik et al. 2019). Use of chemical feed additives in ruminant diets for improving nutrient utilization, is controversial now-a- days because of the risk of their transmission into meat and milk as well as the antimicrobial resistance, focussing the concern of new alternatives to chemical feed additives in the feld of animal nutrition (e Silva et al. 2021, Swelum et al. 2021). In recent years, there has been an increased interest to use natural products containing plant secondary/ bioactive compounds instead of chemical feed additives to modify rumen fermentation for improving feed utilization and productive performances of ruminant animals (Taku et al. 2019, Bhatt et al. 2021, Uushona et al. 2022). Tropical plants normally contain wide spectrum of secondary compounds. Tree leaves contain diferent classes of bioactive compounds such as tannins, saponins, favonoids and many other plant secondary metabolites which have been shown to potentially improve rumen microbial fermentation (Chaturvedi et al. 2021, Santra et al. 2021) and improve animal productivity (Santra et al. 2020, Jiao et al. 2021, Tilahun et al. 2022). Several in vitro studies showed that plant secondary metabolites seem to have the potential to favourably manipulate rumen fermentation to reduce ruminal methane emissions and ciliated protozoal population for efcient use of dietary energy and protein (Bhatta et al. 2017, Singh et al. 2018, Malik et al. 2019, Akanmu et al. 2020). Lemon grass (Cymbopogon citratus), a medicinal herb contains essential oil citronella, which has proven benefcial efect on digestibility, rumen ecology, microbial population and protein synthesis and meat quality in ruminants (Bhatt et al. 2021). Phyto-chemicals present in the Australian Acacia leaves reduced the ruminal methanogenesis and improved the nutrient utilization, growth performances and meat quality in ruminants (Uushona et al. 2022). However, in vivo studies on plant secondary metabolites to use as natural feed additive to manipulate rumen fermentation for efcient utilization of dietary energy and protein to improve productivity of animals is almost lacking/very 47