Partum and postpartum characteristics on the postpartum rebreeding in beef cattle

Influence of weaning management at 30, 75 and 180 days of age on non-esterified fatty acids and reproductive performance in beef cows

This study aimed to investigate the effect of age at weaning of calves on non-esterified fatty acids (NEFA) and reproductive parameters of beef cows. Animals (n = 65) were randomly assigned to three treatments after calving: hyper-early weaning (W30) at 32 ± 0.89 days, early weaning (W75) at 77 ± 0.95 days, and conventional weaning (W180) at 183 ± 0.82 days. Body weight (BW) and body condition score (BCS) were evaluated at parturition (AP) and at 30, 45, 64, 81, 100 and 115 days postpartum (dPP). Blood samples were collected to analyze NEFA levels and progesterone (P4) at 30, 45, 64 and 81 dPP. Higher BW and BCS were observed from 64 to 115 dPP in W30 cows than W180 ones (p < 0.05). Cows subjected to W30 condition had higher levels of NEFA at 30 dPP compared to 64 and 81 dPP (p < 0.05). We also observed that cows from W180 group showed decreased levels of NEFA at 30 dPP compared to 45 (p < 0.01) and 64 dPP (p < 0.05). The highest P4 level was observed at 64 dPP in W30 cows compared to W75 and W180 (p < 0.05). We also observed higher CR of W30 (86%) compared to W180 (47%) at 45 dPP (p < 0.05). The overall pregnancy rate (PR) was higher for W30 (95.5%) than W180 (73.9%). In addition, higher BW at calving and P4 levels at 30 dPP were positively correlated with the possibility of pregnancy (p < 0.05). Improvement in BW and BCS were observed in cows subjected to hyper-early weaning management. However, levels of NEFA decreased as the postpartum period progressed. We concluded that cows who weaned calves hyper-early have greater chances of increasing cyclicity and PRs.

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

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 turnout to pasture removal (158 and 156 days in year 1 and 2, respectively). Consecutive day weights were taken from cows and calves at pasture turnout 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 turnout 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 turnout (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.