Inclusion of lemon leaves and rice straw into compound feed and its effect on nutrient balance, milk yield, and methane emissions in dairy goats

摘要

The objective of this experiment was to study theeffects of incorporating lemon leaves and rice strawinto the compound feed of diets for dairy goats. TenMurciano-Granadina dairy goats (n = 5 per group) inmid-lactation were used in a crossover design experiment(2 treatments across 2 periods). Goats were fed amixed ration with barley grain (control, CON) or CONplus lemon leaves [189 g/kg of dry matter (DM)] andrice straw (120 g/kg of DM) in place of barley grain(LRS). Soybean oil (19 g/kg of DM) was added to theLRS diet to make it isoenergetic (17 MJ of gross energy/kg of DM) relative to CON. After 14 d on their respectivetreatments, goats were allocated to individualmetabolism cages for another 7 d. Subsequently, feedintake, total fecal and urine output, and milk yield wererecorded daily over the first 5 d. During the last 2 d,ruminal fluid and blood samples were collected, alongwith individual gas exchange measurements recordedby a mobile open-circuit indirect calorimetry systemusing a head box. No differences in DM intake were detected,and ME intake in LRS was lower than in CON(1,095 vs. 1,180 kJ/kg of metabolic body weight). Nodifferences were observed in milk production, but milkfat content was greater in LRS (6.4%) than in CON(5.6%). Greater concentrations of monounsaturated(14.94 vs. 11.96 g/100 g of milk fat) and polyunsaturatedfatty acids (4.53 vs. 4.03 g/100 g of milk fat) weredetected in the milk of goats fed LRS compared withCON. Atherogenicity (2.68 vs.1.91) and thrombogenic(4.58 vs. 2.81) indices were lower with LRS comparedwith CON. Enteric CH_4 emission was lower in LRS(24.3 g/d) compared with CON (31.1 g/d), probablydue to the greater lipid content and unsaturated fattyacid profile of lemon leaves and the soybean oil added inthe LRS diet. Overall, data suggest that incorporatinglemon leaves and rice straw into lactating goat diets iseffective in reducing CH_4 emissions while allowing improvementsin milk fat production and milk thrombogenicindex without affecting production performance.Thus, their inclusion in compound feeds fed to smallruminants appears warranted and would have multiplepositive effects, as on efficiency of nutrient use, humanhealth, and the environment.