Effects of supplementation of grazing Nellore cows with ß-carotene and vitamins A + D3 + E + biotin on follicle diameter, oestrus, establishment of pregnancy, and foetal morphometry.

The objectives of this experiment were to evaluate the effects of supplementation of Nellore (Bos indicus) cows with ß-carotene + vitamins A + D3 + E + biotin on body condition score (BCS), oestrus, pregnancy, and foetal morphometry. Lactating cows (n = 497) from two herds were balanced for BCS and calving period [early calving (EC); late calving (LC)] and were assigned randomly to: Control (n = 251)-supplementation with a mineral supplement; and SUP (n = 246)-supplementation with the mineral supplement fed to control + ß-carotene (150 mg/day) + vitamin A (40,000 IU/day) + vitamin D3 (5000 IU/day) + vitamin E (300 mg/day) + biotin (20 mg/day). Cows were supplemented from Days -30 to 30 (Day 0 = timed artificial insemination; TAI). Pregnancy was diagnosed 30 days after TAI and foetal crown-rump distance and thoracic diameter were measured at 30 and 77 days of gestation. Cows in the SUP treatment were more likely to have BCS ≥3.0 on Day 0 (63.0 ± 3.1 vs. 60.2 ± 3.1; p < .01) and were more likely to gain BCS from Days -30 to 30 (57.7 ± 3.3 vs. 44.1 ± 3.3%; p < .01). Fewer LC cows in the SUP treatment were detected in oestrus at the time of the first TAI (Control: LC: 75.4 ± 4.4 vs. SUP: LC: 64.0 ± 5.2 vs. Control: EC: 65.3 ± 4.0 vs. SUP: EC: 71.8 ± 3.7; p = .04). There was a tendency for the SUP treatment to increase pregnancy to the first TAI (64.2 ± 3.0 vs. 56.6 ± 3.1%; p = .08). A greater percentage of SUP cows was detected in oestrus at the time of the second TAI (70.1 ± 5.0 vs. 52.3 ± 4.8%; p = .01). The SUP treatment increased pregnancy to the second TAI among LC cows (SUP: LC: 75.9 ± 8.0% vs. Control: LC: 50.0 ± 8.3% vs. Control: EC: 52.0 ± 5.9% vs. SUP: EC: 41.4 ± 6.5%; p = .02). The SUP treatment increased foetal size (crown-rump; p = .04 and thoracic diameter; p < .01) at 30 days of gestation and, despite decreasing crow-rump length at 77 days after the first TAI among EC cows (p < .01), it increased the thoracic diameter at 77 days after the first TAI independent of calving season. Our results support that pregnancy establishment and foetal growth can be improved when grazing Nellore cows are supplemented with ß-carotene and vitamins A + D3 + E + biotin.

Predicting the response time of an urban ambulance system.

Response time, i.e., the time from dispatch of an ambulance to its arrival at the scene of an emergency, is an important measure of performance in an urban ambulance system. We developed a model that predicts the entire distribution of response time, explicitly accounting for the rate and spatial distribution of demand, variable ambulance velocities, and queueing effects. We tested the model using data sampled from 3,936 ambulance runs in Houston and achieved close agreement between empirical and predicted distributions of response time. Our use of probability theory to predict response times yielded a model that complements those previously reported for planning and evaluating urban ambulance systems.