Effects of feeding a vitamin and mineral supplement to cow-calf pairs grazing native range

Abstract

Our objectives were to evaluate the impacts of providing vitamin and mineral (VTM) supplements to cow-calf pairs during the summer grazing period on cow and calf performance and liver concentrations of minerals. During a two-year period, 727 crossbred cows and their calves (initial cow BW = 601.7 ± 48.1 kg; calf BW = 87.8 ± 5.0 kg; n = 381 in year 1, n = 346 in year 2) from the Central Grasslands Research Extension Center (Streeter, N.D.) were blocked by parity (young [parity 1 to 3], and old [parity 4+]) and randomly assigned to pastures at the beginning of the grazing season (16 in year 1 and 14 in year 2). Pastures were assigned to receive a free-choice VTM supplement (SUPP) or no VTM supplement (CON) from pasture turn out to pasture removal (158 and 156 days in year 1 and 2, respectively). Consecutive day weights were taken from cows and calves at pasture turn out and removal, and liver biopsies were collected from a subset of cows at both timepoints and from calves at weaning. Cows were bred via AI 37 to 41 d after pasture turn out and by natural service cleanup bulls for a 70 to 80 d breeding season. Calving and weaning data were collected from the calf conceived and gestated during treatments. Data were analyzed for the effect of VTM treatment (SUPP vs. CON), block of parity, and their interaction using the GLM procedure of SAS with pasture as the experimental unit. Year was considered a random effect in the final analysis. Cow pregnancy success was evaluated using the GLIMMIX procedure in SAS with model terms of VTM treatment, parity, and their interaction with year as a random effect. In year 2, cows in differing days postpartum (DPP) groups at pasture turn out (66.1, 48.8, and 34.5 ± 1.04 DPP for EARLY, MID, and LATE groups, respectively) were selected for liver biopsies with cow as the experimental unit. Cow and calf BW and BW change were not impacted (P ≥ 0.20) by VTM access. Pregnancy rate to AI, overall pregnancy rate, gestating calf birth BW and calving distribution were not affected (P ≥ 0.11) by treatment. Liver concentrations of Se, Cu and Co were greater (P ≤ 0.002) at pasture removal and weaning for cows and suckling calves that had access to VTM. Cows considered EARLY calving had greater (P = 0.05) concentrations of liver Se compared with LATE calving cows. Although VTM supplementation enhanced concentrations of key minerals in the liver of cow-calf pairs, reproductive and growth performance was not affected.

Influence of pre-weaning trace mineral exposure on subsequent performance and trace mineral status of beef calves during finishing

“…Treatments for Group 2 were applied to cow-calf pairs on pasture as previously described. 5 Mineral supplement provided to cow-calf pairs, with access to mineral in Group 2 contained: 14.4-17% Ca, 7.7-9.2% NaCl, and a minimum of 8.0% P, 0.6% Mg, 0.18% K, 5,500ppm Mn, 65ppm Co, 2,400ppm Cu, 130ppm I, 34ppm Se, 7,820ppm Zn, 215,000 IU/lb Vitamin A, 53,500 IU/lb Vitamin D, and 2,667 IU/lb Vitamin E a .…”

“…The mineral supplement used in year 2 of the cow-calf portion of the experiment contained 12.0-14.0% Ca, 17.5-21.0% NaCl, and a minimum of 6% P, 2.75% Mg, 3,400 ppm Mn, 38 ppm Co, 3,000 ppm Cu, 300 ppm I, 36 ppm Se, and 9,000 ppm Zn, in addition to a minimum of 250,000 IU/lb Vitamin A, 25,000 IU/lb Vitamin D, and 250 IU/lb Vitamin E. i More information on beef cow management can be found in the following publication. 5 Calves were adapted from a moderate-concentrate to a highconcentrate diet in 5 equal steps over the course of 35 days. The final finishing diet consisted of 52.0% dry-rolled corn, 30% modified distillers grains with solubles, 10% corn silage, 5% grass hay, 2.5% vitamin and mineral supplement, and 0.5% calcium carbonate (DM basis).…”