Effects of Gestational Status on Apparent Absorption and Retention of Copper and Zinc in Mature Angus Cows and Suffolk Ewes

Six mature purebred Angus cows ($3.5{\pm}1.5$ years of age, $631.36{\pm}8.63kg$), three pregnant ($250{\pm}7$ days pregnant) and three non-pregnant and eight mature Suffolk ewes ($5{\pm}1.2$ years of age, $68.18{\pm}2.3kg$) four pregnant $115{\pm}5$ days pregnant) and four nonpregnant were utilized in a five-day metabolic trial to determine the effects of gestational status (pregnant vs. non-pregnant) on apparent absorption and retention of copper (Cu) and zinc (Zn). Animals were selected based on body weight, age, and gestational status, and randomly assigned to metabolic crates for total fecal and urine collection. Animals were allowed to acclimate to their new environment for seven days. Pregnant and non-pregnant cows and ewes were then paired (within a species) by body weight and pair-fed throughout the 5 day collection period. Copper and Zn intakes were similar for pregnant and non-pregnant animals within a species. Apparent absorption of Cu (p<0.06) and Zn (p<0.04) were higher in pregnant cows relative to non-pregnant cows. Pregnant cows also had a higher apparent retention of Cu (p<0.05) and Zn (p<0.06) relative to non-pregnant cows. Pregnant ewes had a higher (p<0.01) apparent absorption and retention of Zn compared to non-pregnant ewes. However, apparent absorption and retention of Cu were similar for pregnant and non-pregnant ewes. These data indicate that certain physiological and/or metabolic parameters are altered in pregnant cows and ewes consuming an alfalfa-based diet that enhance the apparent absorption and retention of certain trace minerals.