Feeding rumen-protected methionine during the peripartum period improved milk fat content and reduced the culling rate of Holstein cows in a commercial herd.

The transition period is defined as the three weeks before and three weeks after calving. It is a period of high demand for nutrients, as there are drastic metabolic and hormonal changes that carry over to lactation. These changes may introduce greater disease incidence, often resulting in involuntary culling. As early lactation is also a critical time to evoke high milk production and effective reproduction, the avoidance of metabolic and infectious problems is imperative, because they can carry through to the whole of lactation. The approach should be to strengthen the immune system during the transition period, and one way to do so is by supplementation of rumen-protected methionine (RPM). This sulphur containing amino acid is essential, as it has a prominent role due to its wide range of functions in animal organisms. Moreover, the literature suggests an improvement in liver health and functionality when cows are supplemented with RPM. However, although it has had highly promising results on performance and health, there is still no consensus on the productive and metabolic responses of RPM supplementation in commercial dairy herds during the transition period, which thus is the objective of the cited study.

One hundred sixty-six Holstein cows, 58 first-calf heifers and 108 multi-lactation, were randomly assigned to one of two dietary treatments, consisting of TMR top-dressed with RPM (Rumenprotected methionine: 2.35% and 2.24% for close-up and fresh cows, respectively) or without (CONTROL -  2.03% and 1.89% Non-rumenprotected methionine for close-up and fresh cows, respectively), fed from 21 ± 6 days before calving until 16 ± 5 days after calving. From 17 days in milk (DIM) until dry-off, all cows received RPM. Daily milk yield was recorded, and milk samples were collected in the first and second weeks after calving to determine their composition. Blood samples were collected before the morning feeding on −14, −7, +1, +7, and +14 days relative to calving. Mortality and morbidity were recorded during the first 60 DIM.

The cows supplemented with RPM had greater milk yield during the first 16 DIM (31.76 vs. 30.37 kg/day; SEM = 1.04, respectively), and had greater milk fat content (4.45 vs. 4.10%; SEM = 0.11, respectively), but not milk total protein (3.47 vs. 3.39%; SEM = 0.04, respectively) and casein contents (2.74 vs. 2.66%; SEM = 0.04, respectively) than the CONTROL cows. Also, the cows in RPM had increased plasma methionine concentrations than the CONTROL cows (24.9 vs. 21.0 μmol/L; SEM = 1.2, respectively). Although morbidity was similar between treatments, the culling rate from calving until 60 DIM was lower for the RPM cows than for the CONTROL cows (2.4% vs. 12.1%; SEM = 0.02).

It was concluded that RPM supplementation was effective, because the plasma methionine concentrations were higher in the RPM cows compared with the CONTROL cows; the RPM supplementation during the transition period resulted in an increase in milk yield and milk fat in the first 16 days; and the culling rate from calving until 60 DIM was lower for RPM cows compared with CONTROL cows.