Uso de metionina para melhorar a utilização da proteína e saúde de vacas leiteiras F1 holandês X GIR em pastagem durante o verão

Abstract

Methionine is an essential amino acid, often identified as the most limiting amino acid for milk production. In addition, it also acts on the immune system and against oxidative stress in mammals. The objective was to evaluate supplementation with protected methionine on the performance of lactating crossbred cows maintained on pastures during the summer. Twenty-four F1 Holstein x Gir multiparous cows, producing 31(± 4) L d-1, with 590 kg of live weight (BW) and 100±55 days of lactation were used in a randomized block design to evaluate two treatments for 63 days for to evaluate the supplementation of a control diet with Methionine Protected from Ruminal Degradation (MPR-Smartamine M®, Adisseo SA) to adjust the lysine/methionine ratio (CNCPS) from 3.1 in the control diet to 2.8 in the supplemented diet. The experimental periods were 21 days, with 14 days of adaptation to the diets. The animals were milked twice a day, at 5:30 am and 2:30 pm. Milk samples were collected during three consecutive days, at weeks 3, 6 and 9 of the experimental period. There was an effect of methionine supplementation on milk production corrected for energy (25.0 vs. 26.4 kg d-1 P = 0.08), protein percentages (3.16 vs. 3.28% P = 0.06 ) and casein (2.48 vs. 2.58 P = 0.09), total solids content (11.89 vs. 12.27 P = 0.09). Total CMS was not affected by treatment (P = 0.89). There was no effect on purine derivatives in urina (371.68 vs 433.2 mmol d-1) and microbial protein production (1618.92 vs 1845 g d-1). NUP values were not affected (P = 0.73) for the control or MPR group. The NEFA concentration was not affected by the treatments (P = 0.83). There was no increase in plasma methionine concentration in the MPR group compared to the control (P = 0.22). Feeding with MPR improved lactation performance by increasing milk production corrected for energy, protein, casein and total solids content.