This study examined how breed and trace mineral sources affect growth and diarrhea incidence during periods of nutrient restriction and grazing. Breeds consisted of ½ Angus × ½ Nelore (ANE) and Nelore (NE) heifers, whereas mineral sources included sulfate (SUL) or hydroxychloride (HYD) sources of copper, manganese, and zinc offered to heifers from days 0 to 49. Hay intake was restricted for 34 d (nutrient restriction period; days 0 to 34). Thereafter, heifers were transferred to pastures and grazed forages in early maturity for 14 d (days 35 to 49). During nutrient restriction, NE heifers had greater body weight gain than ANE heifers. While both breeds had a similar incidence of diarrhea, NE heifers had greater serum concentrations of insulin-like growth factor 1 (an indicator of energy metabolism) and less concentrations of inflammation markers. Heifers offered HYD supplement had greater growth performance during nutrient restriction, had fewer incidences of diarrhea during grazing, and temporarily had less serum concentrations of cortisol compared to heifers offered SUL supplement. Overall, breed differences affected growth performance during nutrient restriction but did not modulate growth and diarrhea incidence during grazing. The hydroxychloride supplement positively increased growth performance during nutrient restriction and reduced diarrhea incidence during grazing.

Read the full article in the Journal of Animal Science.