Distillers dried grains with solubles and rumen-protected amino acids in rations of dairy cows for improving resource use efficiency in animal nutrition

A feeding trial was conducted to determine the response by dairy cows to total mixed rations (TMR) in which distillers dried grains with solubles (DDGS, Protigrain (R)) replaced solvent-extracted rapeseed meal (RSM). A third TMR contained DDGS and was supplemented with the rumen-protected amino acids (AA) lysine and methionine. Fifty eight lactating dairy cows were assigned to a 3 x 3 Latin square design experiment over six-week periods. Rations were formulated such that DDGS (> 4 kg dry matter [DM]/day) was 100% of the supplemental crude protein (CP) replacing the CP from RSM. All rations averaging (DM basis) 17.9% CP and 17.9% utilisable CP at the duodenum consisted of (DM basis) 62% forage and 38% concentrate. The aim of the study was to investigate how cows would respond when fed with DDGS as the sole supplemental protein source in the diet. Dry matter intake was lower in the DDGS group (p < 0.05). Milk production was similar for cows on the three rations. Milk fat content and milk fat yield were also the same in all rations. Milk protein content (p < 0.01) and milk protein yield (p < 0.05) was lower in the DDGS and the DDGS + AA groups in contrast to the RSM group. If data of cows were separated according to 'high' or 'low' milk yield, higher DM intake was observed in the RSM and the DDGS + AS groups compared with the DDGS group (p < 0.01). Based on economic and nutritional considerations, the supplementation of rumen-protected AA (lysine and methionine) should be further evaluated in rations for high-yielding dairy cows in early lactation.