Effects of a nonforage diet on milk production, energy and nitrogen metabolism in dairy goats throughout lactation

The objective of the experiment was to compare a silage-based control diet (C) with a nonforage diet (NF) in dairy goats throughout lactation in terms of animal performance and energy utilization. Eight Saanen goats were divided into two groups and fed C or NF, a commercial blend that included sunflower meal, cassava, coconut meal, and whole cottonseeds as the main ingredients that was characterized by a small particle size and a high crude protein content. In early, mid, and late lactation (44, 100, and 219 days in milk) the goats were individually tested for dry matter intake (DMI), digestibility, milk yield and composition, milk renneting properties, rumen and plasma parameters, and nitrogen and energy utilization (open circuit respiration chambers). During early and mid lactation, the NF fed goats had a very high DMI: 2946 and 2915 g/ d, respectively. Nevertheless, milk yield was similar for the two treatments: 4369 vs. 4342 and 3882 vs. 3841 g/d for goats fed diets C and NF during the first and second periods, respectively. Milk fat content was not statistically different between the two diets. The protein content and rheological parameters of milk were similar for the two diets. Nonprotein nitrogen and urea levels in milk of goats fed NF were significantly higher than goats fed C. Ruminal ammonia and plasma urea nitrogen were also significantly increased by diet NF, due to its high protein content. Plasma glucose, β-hydroxybutyrate, and nonesterified fatty acids and ruminal volatile fatty acids were not influenced by dietary treatment. Dietary NF significantly decreased energy digestibility (74.5 vs. 65.8%, on average for the lactation, for C and NF, respectively) and had a significantly lower metabolizability (metabolizable energy/intake energy; 66.6 vs 58.0%, on average); however, the efficiency of utilization of metabolizable energy was unaffected by the diet. In conclusion, goats were fed a nonforage diet during the entire lactation without detrimental effect on their health and productive performance.