Feeding mango wastes to dairy goats: Effects on diet digestibility, ruminal fermentation, and milk yield and composition

Abstract

The aim of this study was to assess the potential of mango wastes (0.65:0.35 pulp:peels mixture, PP) preserved in multinutrient blocks (MMB) for goats feeding that replaced part of a commercial concentrate for dairy goats, and contained 0.29 of the mango PP. The multinutrient blocks were formulated to have similar protein content than the concentrate. In addition, soybean meal was totally replaced with sunflower meal. Two diets composed of 0.4 of alfalfa hay and either 0.6 of a commercial concentrate (control diet) or 0.4 of concentrate and 0.2 of MMB (MAN diet) were fed to two homogeneous groups of Murciano-Granadina dairy goats of 8 animals each. Feed intake, diet digestibility, milk yield, composition and fatty acid (FA) profile, ruminal fermentation parameters, and urinary excretion of purine derivatives were measured. The daily intake of MMB averaged 83.9 g dry matter (DM) per goat and was accompanied by an average daily decrease of 71.0 g in concentrate intake (P = 0.324) and 41.0 g of increase in alfalfa hay intake. However, there were no differences between groups (P ≥ 0.253) in the intake of total DM, nitrogen and gross energy. Similarly, nutrient digestibility, utilization of both nitrogen (N) and energy, and urinary excretion of purine derivatives were similar (P ≥ 0.103) for both diets. Partial replacement of concentrate with MMB did not affect (P ≥ 0.358) milk yield and composition, but the milk from MAN-fed goats had greater (P = 0.038) saturated FA and lower (P = 0.047) polyunsaturated FA proportions than the milk from goats fed the control diet. Feeding the MAN diet also resulted in greater (P = 0.003) proportions of milk FA with less than 16 carbons and lower (P = 0.009) proportions of FA with more than 16 carbons compared with feeding the control diet. Similar values (P ≥ 0.213) of ruminal pH and concentrations of NH3-N and total volatile fatty acids were registered in both groups of animals, but goats fed the MAN diet had lower (P = 0.003) acetate and greater (P = 0.029) propionate proportions than those fed the control diet. Under the circumstances of the present study, the profit of milk production (€/d) tended (P = 0.056) to be greater for the MAN diet compared with the control diet. Although multinutrient blocks seem to be a feasible option to preserve mango wastes, more studies are needed to increase the intake of MMB by goats.