LAUSR

Abstract There are worldwide a number of by-products with a strong potential for use in animal feeding to cover purposes as farm economic profitability enhancement or searching of functional food ingredients. Probably fruit and vegetable industry (i.e. olive milling wastes) are amongst the most representative sectors. Two experiments were performed with lactating Murciano-Granadina goats. In Experiment 1 the objective was to assess the effect of the partial replacement of the forage in the diet with olive by-products or tomato silages supplemented with sunflower oil (SFO, 20 g/kg DM) on the nutrient utilization, rumen fermentation parameters and microbial abundances, methane production and milk yield and composition. Eighteen goats were distributed in three experimental groups and fed control diet (CD) against diets containing olive by-products silage (OBSD) or tomato surplus silage (TSD). Both OBSD and TSD resulted in higher fat intake and apparent digestibility, higher digestible and metabolizable energy and total purine derivatives excretion. The rest of measured parameters remained unaffected. Diets OBSD and TSD promoted higher milk content in C18:1 trans-11, C20:2 and CLA. Milk fat of goats consuming TSD had the lowest content in C4:0, C6:0 and C8:0, while OBSD produced more total saturated FA (SFA) and less C18:1 n-9 cis and both total mono- and polyunsaturated FA. The acetate concentration was lower in the rumen of animals fed silages, while the butyrate and protozoa concentrations were higher in OBSD. The CH 4 production (L/kg DMI) tended to be lower in goats consuming TSD. Experiment 2 was conducted to test the persistence (over 90 days) and in a larger number of animals (n = 24) of the effects observed with TSD diet in experiment 1. The TS diet promoted higher DM intake and body weight and lower acetate:propionate ratio than CD, whereas milk yield and composition were not affected. The FA profile was modified by increases in SFA and reducing monounsaturated FA and CLA. It may be concluded that the strategy of partial replacement of conventional forage by local by-products silage combined with SFO supplementation is valuable nutritional strategy in dairy goats since it may improve the animal energy balance while ruminal fermentation, nutrients utilization and milk yield are not compromised.