Contrasting feeding management in the first 21 days postpartum in Holstein dairy cows: direct and residual milk responses

The transition period and its management affect how dairy cows face physiological challenges. Total mixed rations ( TMR ) have been shown as a strategy to address pasture-based system limitations and improve milk production, without consistent information about their use in short periods and residual responses. The study aimed to evaluate contrasting feeding management in the first 21 days postpartum on direct and residual milk production responses until 60 days in milk ( DIM ). Sixty-seven mixed parity Holstein dairy cows were used in a completely randomised block design in two treatments across two trials: MD-MD, cows fed a mixed diet ( MD ) with grazing and supplementation with mixed ration, from calving until 60 DIM, TMR-MD: confined cows with TMR provided ad libitum during the first 21 DIM in a compost-bedded pack barn and changed to MD at 22 until 60 DIM. During the first 21 DIM (direct response), cows fed TMR produced 11.7% more milk than those on MD-MD. Multiparous ( M ) TMR-MD obtained 18.6% higher milk yield than M MD-MD cows, but no significant differences were detected between primiparous ( P ) cows. After the switch at 22 DIM (residual response), no significant differences were detected between treatments in milk yield. However, the interaction between treatment and parity indicates that M TMR-MD cows exhibited 3.6% more milk than those in MD-MD, as a carryover effect. In contrast, P cows did not differ between treatments. In the first 21 DIM, TMR-MD cows achieved a higher fat concentration and protein yield than MD-MD. Fat yield tended to increase in TMR-MD compared to MD-MD, without treatment effect for lactose yield. In the residual period, TMR-MD cows had higher protein concentrations and tended towards higher fat concentrations than MD-MD cows. The interaction between treatments and parity showed that P TMR-MD cows had higher protein and exhibited a trend towards higher fat concentration than P MD-MD cows. The differential feeding management during the first 21 DIM did not generate differences in body condition score ( BCS ), between treatments or parities. In the residual period, TMR-MD cows achieved a higher BCS than MD-MD cows without differences between parities. No differences were found between treatments in grazing and ruminating time, reflecting a successful adaptation of TMR-MD cows. In conclusion, feeding TMR during the first 21 DIM is an effective strategy for increasing milk yield and achieving short-term carryover effects in M, but not in P cows.