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Effects of dietary antioxidants and modulators of immune response on milk fatty acids as determined by mid-infrared spectroscopy in Holstein cows during heat stress.

A. Ruiz-González

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06-24-2020

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Abstract:

W96
Effects of dietary antioxidants and modulators of immune response on milk fatty acids as determined by mid-infrared spectroscopy in Holstein cows during heat stress.
A. Ruiz-González,2, W. Suissi2, L. H. Baumgard3, P.-Y. Chouinard1, D. Santschi4, R. Gervais1, D. E. Rico2. 1Universit� Laval Quebec, QC, Canada, 2CRSAD Deschambault, QC, Canada, 3Iowa State University Ames, IA, 4Lactanet Ste-Anne de Bellevue, QC, Canada.

Mid-infrared spectroscopy can be used to obtain predictions of milk fatty acid (FA) profiles and thus serve to identify risk of heat stress in cows. Twelve multiparous Holstein cows (42.2 � 5.6 kg milk/d; 83.4 � 27.1 DIM) were used in a split-plot design testing the effects of mineral and vitamin supplementation on milk FA during heat stress. The main plot was the level of dietary vitamin E and Se: 1) HVE: 200 IU/kg and 1.2 ppm; LVE: 20 IU/kg and 0.3 ppm; respectively). Within each plot, cows were randomly assigned to 1) heat stress (HS), 2) Pair-feeding (PF), or 3) HS with Vitamin D and Ca supplementation (HS+DCa; 1820 IU/kg and 1.5% Ca) in a Latin square design with 14-d periods. Milk FA were analyzed by mid-infrared spectroscopy in milk samples from d 0, 3, 7, 10, and 14. This statistical model included the effect of cow and period as random effects, and the fixed effects of plot, treatment, day and their interactions. A main plot x time interaction was observed for milk fat concentration of FA <16C (de novo origin; P = 0.08) with a progressive decrease over time in both groups, but lower concentrations on d 3, 7, and 14 in the LVE than in the HVE group (−7%; P < 0.05). A 3-way interaction was detected for the concentration of 16 C FA in milk fat (mixed origin; P = 0.03), as they decreased in the PF treatment, being lower than in HS and HS+DCa on d 7, 10, and 14 (−14%) in the HVE, and on d 7 and 14 on the LVE group (−13.5%; P < 0.05). A 3-way interaction was detected for FA >16C (P = 0.02; preformed FA) as their concentration in milk fat was higher in PF than in HS and HS+DCa cows on d 7, 10, and 14 in the HVE group (+21%; P < 0.05), but not different at any time point in the LVE group. Hence, mineral and vitamin supplementation modulates the effects of heat stress on milk fatty acid profile. Milk FA profile by mid-infrared spectroscopy could serve as an indicator of heat stress risk in dairy farms.

Keywords: mid-infrared spectroscopy, heat stress, milk fatty acids.