1528
Peripartal supplementation of Smartamine M has positive effects on blood neutrophil activation in dairy cows
An effective immune response relies on efficient activation of polymorphonuclear neutrophils (PMN). We evaluated mRNA expression of genes associated with metabolism of Met, glutathione, and glucose as well as inflammation, cellular receptors, and oxidative stress in PMN during the peripartal period. Twenty-eight multiparous Holstein cows in a randomized complete block design were fed a controlled-energy diet (CE, n = 9; 1.24 Mcal/kg DM; high-straw) during the dry period (approximately 50 d), switched to a moderate-energy (ME, n = 9; 1.54 Mcal/kg DM) during the last 21 d before calving, or ME plus Smartamine M (SM, n = 10; Adisseo France S.A.S.). After calving all cows received the same lactation diet (1.75 Mcal/kg DM). The SM (0.07% of DM) was top-dressed over the ME diet from -21 through 30 DIM. Daily dry matter intake (DMI) and milk yield were recorded. Whole blood leukocyte phagocytosis (Phagotest®) was assessed and RNA from PMN was extracted from samples collected at -10, 3, and 21 DIM. Data were analyzed using the MIXED procedure of SAS. Although prepartal DMI was not affected (P = 0.21) by diet, postpartal DMI was lower (P < 0.005) in ME than CE and SM. Milk yield was also lower (P < 0.05) in ME than CE and SM. There was a greater (P < 0.001) phagocytosis in CE cows than ME and SM. Although phagocytosis decreased (P = 0.02) from -10 to 21 DIM regardless of treatment, there was a trend (P = 0.10) for an increase in phagocytosis in SM. The selectin L (SELL) mRNA expression was greater in SM cows at 21 DIM than CE (P < 0.001) and to a lesser extent (P = 0.11) than ME. In fact, SELL increased (P < 0.001) in SM cows from -10 to 21 DIM, while it decreased (P = 0.006) in CE and was unchanged (P = 0.87) in ME. The diet×time effect (P = 0.005) for superoxide dismutase 2 (SOD2) expression was associated with greater (P < 0.06) expression at 21 DIM in SM than CE and ME cows. This was reflected in a linear decrease of SOD2 expression in CE (P < 0.001) and ME (P = 0.001), while it remained unchanged in SM (P= 0.65). The lower performance in cows fed ME might be related to impaired neutrophil activation, which appears to have been corrected by SM supplementation.
Keywords:
Immune function, transition cows, methionine