Crude glycerin in the feed supplementation of lactating goats on pasture

Eight Alpine lactating goats with a body weight of 45.2 +/- 7.5 kg and average milk production of 2.3 +/- 0.183 kg/day were distributed in a double 4 x 4 Latin square to evaluate the effect of levels of crude glycerin in the feed supplement on the performance and metabolic parameters managed on Panicum maximum cv. Aruana pastures. The supplement consisted of corn grain, soybean meal, crude glycerin (0, 30, 60, and 90 g/kg in the dry matter of the supplement), calcitic limestone, and a mineral mixture. There was no effect of crude glycerin (CG) addition on the intake and apparent digestibility of dry matter and nutritional components, except for the ether extract. The milk fat content increased with the CG levels. The composition of C18:1 n-9, C18:2 n-6 cis, and C18:2 n-6 trans fatty acids in the milk had a quadratic response to CG levels, and the same effect was observed for the omega 3 and omega 6 polyunsaturated acids. Preprandial glucose levels decreased linearly with the addition of CG levels to the supplement, but were reestablished postprandially. The intake and excretion of nitrogen (N) in milk and the proportions of N absorbed and retained by the animal organism were not changed with the addition of CG to their feed supplement. The proportion of retained in relation to ingested N was higher when CG was added. Crude glycerin added to the supplement of lactating goats on pasture improves the N utilization by the animal organism and acts as a source of glucose in the first hours after feeding, in addition to elevating the polyunsaturated fatty acid content of milk. Therefore, this product can be included at up to 90 g/kg in the supplement of lactating goats on pasture.