70 Effects of copper, zinc, and manganese intake in late gestation on milk, cow plasma, and calf plasma trace mineral concentrations post-calving in beef cattle

Abstract Multiparous, fall-calving beef cows [n = 48; 649 ± 80 (SD) kg BW; 5.3 ± 0.5 BCS] were individually-fed tall fescue-based hay (12.2% CP, 61.5% NDF) and supplemented to meet/exceed nutrient recommendations except Cu, Zn, and Mn. From approximately 90 d pre-calving to 11 d post-calving, cows received: no additional Cu, Zn, or Mn (CON); Cu, Zn, and Mn sulfates (ITM) or metal methionine hydroxy analogue chelates (CTM, MINTREX®, Novus International) supplying 133% NASEM recommendations; or Cu, Zn, and Mn sulfates and chelates supplying 100% recommendations (reduce and replace, RR). Treatment, sampling day, their interaction, and breeding group were fixed effects with cow as the experimental unit. Colostrum and milk Cu and Mn and plasma Mn were generally not detectable. Colostrum Zn was greater (P ≤ 0.03) in CTM and ITM than CON and RR. All treatments had greater (P < 0.001) colostrum Zn than d 35 milk, which was greater (P ≤ 0.03) than d 60. Treatment did not affect (P ≥ 0.19) cow or calf plasma Cu or Zn post-calving. Calf plasma Zn decreased (P ≤ 0.02) from 0 to 35 d of age. Calf plasma Cu increased (P < 0.01) from 0 to 35 d, then decreased (P = 0.01) from 35 to 60 d. Cow plasma Zn and Cu were greater (P ≤ 0.02) at lactation d 35 and 60 than 1 h post-calving. Pearson correlation coefficients were used to determine relationships among cow and calf mineral status. There were weak positive correlations (P ≤ 0.06) between calf plasma and milk Zn at d 35 and 60. Cow and calf plasma Zn immediately post-calving had a weak negative correlation (P = 0.04). These results indicate greater Zn concentration in beef cow colostrum than milk, and suggest calf circulating Zn is partially dependent on milk Zn concentration.