Seasonal changes in feed intake, diet digestibility and diet composition by lactating and non-lactating goats browsing in a semi-arid rangeland of Argentina

Abstract

We determined the seasonal nutrient and secondary compound intake, in vivo diet digestibility (DD) and diet species composition of goats in different physiological states in a desert rangeland of Argentina. During the wet and the dry seasons, 24 mature female Creole goats (six non-lactating, non-pregnant and six lactating in each season) were used in a 2 × 2 factorial design. Diet botanical composition, DD and dry-matter intake (DMI) were estimated by the combined use of visual observation, microhistological analyses of faecal samples and n-alkane technique. Browse species dominated the goats’ diets (>80%) in both seasons and physiological states, with a twofold increase in the proportion of forbs during the wet season (p < 0.10). Lactating goats showed greater DMI than non-lactating animals, and they also displayed greater intakes of some tanniferous (Mimosa ephedroides) and high-protein (Atriplex lampa) shrubs (p < 0.10). Lactating and non-lactating goats selected diets with adequate crude protein (CP) and fibre content but insufficient energy, although lactating goats tended to increase energy and tannin content in their diets (p < 0.20). Physiological state did not influence DD, but digestibility was greater (p < 0.10) in the wet season, attributed to the greater protein content and lower tannin content of the diet. These results have important implications for managerial interventions on traditional goat production systems in the study area aiming at enhancing goat nutrition and welfare, as well as the sustainability of rangeland resources in the region.