Plant polyphenol extract supplementation affects performance, welfare and the Nrf2-oxidative stress response in adipose of heat stressed dairy cows.

We examined the effects of a supplement of plant polyphenols extracts of green tea, capsicum and fenugreek, and electrolytes [(Na+, K+), AXT; Axion ThermoPlus, CCPA, France] during summer heat load on production, welfare, and oxidative stress proteins in adipose tissue (AT) of dairy cows. Forty-two multiparous mid-lactation cows were divided into 3 groups during summer, and were fed for 2 wks either a standard milking cows' diet (CTL, n = 14), or supplemented with 100 g/d of AXT (100AXT, n = 14), or 150 g/d of AXT (150AXT, n = 14), while being cooled 5 times a day; then, half of the cows from each dietary treatment were cooled (CL) or not-cooled (NCL) for 2 wks, after which the CL/NCL were switched for additional 2 wks. Cows were milked 3 times a day and milk composition was analyzed at the end of each 2 wk period. Vaginal temperature (VT) was measured for 3 consecutive days in each period. Biopsies of subcutaneous AT were taken from 10 NCL cows (5 CTL and 5 150AXT) at the end of the period, and examined by LC-MS/MS proteomics analysis. Data were analyzed with PROC MIXED of SAS; the model included the effects of dietary treatment, cooling regimen, period, and their interactions. Protein and mRNA abundances and proteomic data [P ≤ 0.05 and fold change (FC) ± 1.5] were analyzed by t-test. Milk yields and 4% FCM were higher in 100AXT than in CTL; milk components were not different. DMI was higher in 100AXT than in CTL. The effect of cooling and the interactions of period × cooling were significant for DMI, 4% FCM, ECM and milk/DMI. The proportion of time that VT was > 39°C was lower in 100AXT and in 150AXT than in CTL. Daily rumination time was higher in 150AXT than in CTL, and lying time was higher in 100AXT and 150AXT vs. CTL. Proteomics of AT demonstrated that 150AXT had increased abundances of peroxidasin (FC = 1.6), microsomal glutathione S-transferase 2 (FC = 2.5) and heme oxygenase 1 (FC = 3.6) compared with CTL. Top enriched canonical pathways included acute phase response signaling, Nrf2-mediated oxidative stress response, and LPS/IL-1-mediated inhibition of RXR function. Immunoblots of AT showed a higher abundance of the transient-receptor-potential-vanilloid-1 and of lipopolysaccharide-binding protein in AT of 150AXT vs. CTL. Supplementation of AXT increased DMI, milk, and 4% FCM, lowered VT, improved welfare indices, and enriched the AT with Nrf2-oxidative stress response and acute phase response proteins in heat-stressed dairy cows.