Supplemental protein concentrate to postpartum dairy cows increases milk production with positive carry-over effects

Previous studies have demonstrated that abomasal infusion of casein to postpartum transition dairy cows can increase milk yield (MY) by around 7 kg/d for the first 4 weeks in milk (Larsen et al., 2014), but longer-term carry-over effects have been difficult to obtain with practical diets. This on-going pilot study aimed to assess the carry-over effect of short-term protein supplementation in early lactation on milk production of dairy cows. Twenty-five Danish Holstein cows were included in the experiment, of which 10 calved into second and 15 into third or fourth lactation. Within parity group, cows were assigned to one of two treatments: 1) a standard lactation diet (CON; 16.7% CP of DM, 32.8% NDF, and 17.0% starch) and 2) CON + protein concentrate [BOOST (42.3% CP, 7.9% NDF, 12.2% starch); 4 kg/d from 1 to 7 DIM, then reduced by 200 g/d until 27 DIM]. The cows had ad libitum access to the basal diet in a Roughage Intake Control system (RIC; Insentec BV). The protein concentrate was provided in a separate RIC bin and allowance was adjusted according to DIM. Daily intake of basal diet and protein concentrate, and MY were recorded. Data were analyzed using the lmer function in R with treatment, DIM and their interaction, and parity as fixed and cow as random effects. Daily intake of protein concentrate from 1 to 7 DIM averaged 3.24 kg (SEM = 0.499), and decreased on average 204 g/d from 8 to 27 DIM. Milk yield was 7.1 kg/d greater (P ≤ 0.01; SEM = 1.96; n = 13 cows/treatment) for BOOST vs. CON cows on 1 to 7 DIM. During the gradual decrease of BOOST until 27 DIM, the difference in MY persisted, being on average 47.0 vs. 39.0 kg/d (P ≤ 0.001; SEM = 1.98; n = 13). After discontinuation of BOOST, from 28 to 45 DIM, MY continued to be around 5.7 kg/d greater (P ≤ 0.02; SEM = 2.09; n = 8 to 11) for the BOOST cows. Total dry matter intake did not differ between treatments (P = 0.58) and averaged 18.2 kg/d (SEM = 1.46) from 1 to 7 DIM, 22.2 kg/d (SEM = 1.46) from 8 to 27 DIM, and 24.9 kg/d (SEM = 1.71) from 28 to 45 DIM. These preliminary results indicate that providing a metabolizable protein boost as a separate concentrate feed in the very first days of lactation can improve milk production with positive carry-over effects into at least the first 6 weeks of lactation. This on-going study will further test the effects of BOOST on milk composition, nitrogen utilization, and metabolic and physiological parameters throughout lactation.