Effects of partial substitution of alfalfa hay with green tea waste on growth performance and in vitro methane emission of fat-tailed lambs

In this study, the effects of partial substitution of alfalfa hay (AH) with green tea waste (GTW) on feed intake, growth performance, digestibility, nitrogen (N) retention, ruminal fermentation, serum metabolites and methane emission of fattening fat-tailed lambs were evaluated. Methane emission was determined in in vitro condition using gas production technique. Twenty Chall male lambs with an initial body weight of 34.36 ± 3.35 kg were randomly assigned into four isoenergetic and isonitrogenous diets in which AH was replaced with different levels [(0 (control), 20, 40 or 60 g/kg dietary dry matter (DM))] of GTW for a period of 84 days. The replacement of AH by GTW did not affect dry matter intake (DMI). The replacement of AH up to 60 g/kg GTW significantly decreased average daily gain (ADG) (linear (L) and quadratic (Q), P < 0.05) and increased feed conversion ratio (FCR) (L, P < 0.05). The highest crude protein (CP) digestibility was observed in lambs receiving 20 g/kg GTW in the diet (L and Q, P < 0.05). N retention in the 20 g/kg GTW recipient group was similar to the control, but it was significantly more than other treatments (L and Q, P < 0.05). Increase in the proportion of GTW in the diets decreased ammonia-N in the rumen fluid (L, P = 0.003). When the levels of GTW in the diets were increased, serum concentration of urea-N decreased (L, P < 0.05). Dietary treatments decrease the amount of methane emission (L and Q, P < 0.05). According to the results, substitution of AH with GTW at 20 g/kg DM level in the diet of fat-tailed lambs can improve growth performance by improving digestibility, N retention and reducing methane emission.