The study tested the hypothesis that physiological measurements can predict marathon running performance in a top-level homogeneous group of males and females. Ten male, performance: 2:12:04, coefficient of variation (CV)=2.33%, and 8 female marathon runners, performance: 2:34:53, CV=4.54%, performed an increment test on the treadmill (starting speed, 8 km.h-1; increments, 2 km.h-1; increment duration, 3 min to exhaustion). The heart rate (HR), VO2 and the lactate concentrations were measured at the end of each exercise level. During the recovery time, HR and lactate were measured. Furthermore, echocardiographic, anthropometric and haematologic measurements were made. The results of a stepwise multiple regression analysis using marathon time as the dependent variable yielded R2=0.983 for the male group and R2=0.984 for the female group. The model for the male group used the independent variables lactate value at 10 km.h-1, left ventricular telediastolic diameter (LVD) and lactate value at 22 km.h-1. The model for the female group used the independent variables subscapular skinfold, serum ferritin and sum of six skinfolds. Our study demonstrates that in males and females, physiological parameters can explain the variance in marathon time among elite homogeneous groups.

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With the aim of evaluating how changes in the metabolic status in the last month of pregnancy affects reproductive efficiency, forty six Bos indicus multiparous cows (5.5 ± 2.4 parturitions), were used. Measurements of body weight (BW), body condition score (BCS) and dorsal back fat (BF) were taken in the last month of pregnancy, postpartum period previous to synchronization (average 50 d) and at breeding by natural mating following synchronization with a progestin (average 70 d). Average postpartum days to resumption to ovarian activity were 79.96 ± 16.5 d, and average postpartum days to conception was 88.5 ± 14 d. Days postpartum to resumption of the ovarian activity was positively correlated (0.51, P < 0.01) with days postpartum to conception, also, days postpartum to conception was positively correlated with prepartum back fat (14 d before parturition) (0.44, P < 0.05). It was observed that BF at calving which is an objective measurement had a low correlation with other productive variables such as BCS and BW (always less than 0.39). Body fat might be a more reliable indicator of the current metabolic status of the animal particularly in the last month of pregnancy when the indicators of BCS are somehow more difficult to interpret and subjective.

In order to evaluate the effect of protein supplementation on the productive and reproductive performance of heifers, 45 Bos indicus x Bos taurus heifers, 673 +/- 146 days of age and weighing about 340 kg, were divided into two groups. The control group (n = 23) continued without supplementation, but the supplemented group (SG; n = 22) received concentrate at a rate of 1% BW kg per day. Animals were adapted to the concentrate over a 15-day period and then supplemented for 30 days, after which estrus was synchronized using a progesterone implant. Back fat thickness (BFT) was assessed by ultrasound. The SG had better average daily weight gain than the nonsupplemented group (0.63 +/- 0.16 vs. 0.51 +/- 0.13 kg/day, P < 0.05) and tended to show a better percentage ovulation (P < 0.10, 77% vs. 57%, respectively). However, this tendency was not reflected in the final pregnancy rates. No differences were observed between groups in dry matter intake and body condition scores. SG with a high BFT (>0.70 cm) showed a better ovulation percentage than those with low BFT (<0.69 cm; P < 0.01). Additionally, the pregnancy rate of supplemented heifers with high BFT tended to be better than heifers with low BFT in this same group (67% vs. 30%, respectively, P < 0.10). It is concluded that protein supplementation improved reproductive performance and that ultrasonography to measure BFT may be used to estimate reproductive performance.