Assessment of performance, oxidative stress status, and plasma AA profiles in peripartal dairy cows supplemented with rumen-protected methionine or choline and with different liver functionality indices

Abstract Text: Objectives were to evaluate performance, oxidative stress status, and plasma AA profiles of peripartal dairy cows with different liver functionality indices (LFI). Forty multiparous Holstein cows were randomly assigned to control (CON), no methionine (MET) or choline (CHO); CON+MET; CON+CHO; and CON+MET+CHO treatments. Cows received the same diet (1.52 Mcal/kg DM) from −21 d (close-up) to calving. Cows were on the same diet (1.71 Mcal/kg DM) after calving and continued to receive the same treatments through 30 d. Blood samples were taken at −30, -10, 4, 14 and 28 d relative to calving. Liver samples were harvested at −10, 7, 20 and 30 d relative to calving. MET supplementation was adjusted daily at a rate of 0.08% (DM basis) of diet and CHO was supplemented at 60 g/cow/d. Main effect of LFI was analyzed using PROC MIXED in SAS. LFI is an index assessing transition cow metabolic health by measuring changes in plasma albumin, cholesterol and bilirubin. A high LFI (better liver function) is characterized by lower bilirubin and higher cholesterol and albumin, and the opposite is true for low LFI. Cows were ranked retrospectively and assigned to low (L, LFI<0), medium-low (ML, 0<LFI<1.5), medium-high (MH, 1.5<LFI<3), and high (H, LFI>3) groups according to LFI regardless of MET or CHO supplementation. Most (13/20) of the MET cows fell into the MH and H groups, while CHO cows were evenly distributed across the 4 LFI groups. Close-up and lactation DMI, milk yield, and protein yield increased (P < 0.01) with higher LFI. Compared with L and ML, cows in MH tended (P = 0.08) to have greater total and reduced hepatic glutathione concentration. Similarly, compared with L plasma paraoxonase was greater (P = 0.04) in MH and H, suggesting better oxidative stress status in cows with higher LFI. A main effect of LFI was detected for essential amino acids (P < 0.01) and branch-chain amino acids (P = 0.04) concentration due to increased (P < 0.05) concentration of Methionine, Lysine, Histidine, Arginine, Tryptophan, Valine, Leucine, and Isoleucine with higher LFI. Concentrations of Serine, Asparagine, Proline, Alanine, Tyrosine, Citrulline, Ornithine, also increased (P < 0.05) with higher LFI, and contributed to greater (P< 0.05) total amino acids concentration. Overall, results indicate that cows with higher LFI had improved production performance, a reduction in oxidative stress, and a better plasma AA profile. 

Keywords: amino acid, liver functionality index, transition cow