RESUMO
BACKGROUND: Main objectives were to determine to what extent Smartamine M (SM) supplementation to a prepartal higher-energy diet could alter neutrophil (PMN) and liver tissue immunometabolic biomarkers, and whether those responses were comparable to those in cows fed a prepartal lower-energy diet (CON). RESULTS: Twenty-eight multiparous Holstein cows were fed CON (NEL = 1.24 Mcal/kg DM) during d -50 to d -22 relative to calving. From d -21 to calving, cows were randomly assigned to a higher-energy diet (OVE, n = 9; NEL = 1.54 Mcal/kg DM), OVE plus SM (OVE + SM, n = 10; SM = 0.07 % of DM) or remained on CON (n = 9). All cows received the same basal lactation diet (NEL = 1.75 Mcal/kg DM). Supplementation of SM (OVE + SM) continued until 30 d postpartum. Liver biopsies were harvested at d -10, 7, and 21 relative to parturition. Blood PMN isolated at -10, 3, and 21 d relative to calving was used to evaluate gene expression. As expected, OVE increased liver lipid content postpartum; however, cows fed OVE + SM or CON had lower concentrations than OVE. Compared with OVE, cows in CON and OVE + SM had greater DMI postpartum and milk production. Furthermore, cows fed OVE + SM had the greatest milk protein and fat percentage and lowest milk SCC despite having intermediate PMN phagocytic capacity. Adaptations in PMN gene expression in OVE + SM cows associated with the lower SCC were gradual increases from -10 to 21 d in genes that facilitate migration into inflammatory sites (SELL, ITGAM), enzymes essential for reducing reactive oxygen metabolites (SOD1, SOD2), and a transcription factor(s) required for controlling PMN development (RXRA). The greater expression of TLR4 on d 3, key for activation of innate immunity due to inflammation, in OVE compared with CON cows suggests a more pronounced inflammatory state. Feeding OVE + SM dampened the upregulation of TLR4, despite the fact that these cows had similar expression of the pro-inflammatory genes NFKB1 and TNF as OVE. Cows in CON had lower overall expression of these inflammation-related genes and GSR, which generates reduced glutathione, an important cellular antioxidant. CONCLUSIONS: Although CON cows appeared to have a less stressful transition into lactation, SM supplementation was effective in alleviating negative effects of energy-overfeeding. As such, SM was beneficial in terms of production and appeared to boost the response of PMN in a way that improved overall cow health.
