Serum creatinine is a poor marker of a predicted change in muscle mass in lactating sows.

Serum creatinine (SCr) in humans has proven to be a reliable biomarker of body protein breakdown and/or muscle mass change. This study set out to investigate the potential of SCr to indicate a loss in sow muscle mass over lactation, validated against 3 methyl histidine (3MH) and blood urea nitrogen (BUN), markers of dietary and/or body protein breakdown. A total of 40 sows were allocated to four treatment groups aimed to induce body weight changes by restrictively feeding sows using a stepwise percentage reduction model. Data were pooled and reallocated into three groups representing the 25th , 50th and 75th percentiles based on body weight change over lactation in the range -22.3 to -4.1% (treatment 25), -4.0 to 6.2% (Treatment 50), and 6.3-15.2% (Treatment 75). Indirect measures for the prediction of protein (3MH, BUN) or fat change (caliper, P2) were taken on entry into the farrowing house, day 5 of lactation, and at weaning. Serum was collected on these days, and SCr, 3MH and BUN were analysed. Piglet weaning weight and average daily feed intake did not differ between treatments (p > .05). There were no changes (p > .05) in indirect measures of body composition (sow caliper score, P2) and analytes (SCr, 3MH, BUN) over lactation. By day 20, those sows in treatment 25 had higher (p < .05) 3MH concentrations whilst changes from day 5 to 20 were not different (p > .05) and did not correlate with SCr change (p > .05) but were highly correlated to BUN change (R2 = 0.691, p < .001). The data suggested that concentrations of SCr and BUN may have been the result of dietary and/or body protein breakdown and/or changes in muscle mass. In the current testing conditions, SCr was not a reliable marker of changes in muscle mass.

Scrotal circumference of Australian beef bulls.

Normal range for scrotal circumference in Australian beef bulls was established using more than 300,000 measurements of breed, management group, age, liveweight, and scrotal circumference. The data used were derived from Australian bull breeders and two large research projects in northern Australia. Most bulls were within 250 to 750 kg liveweight and 300 to 750 days of age. The differences between breeds and variances within breeds were higher when scrotal circumference was predicted from age rather than liveweight, because of variance in growth rates. The average standard deviation for predicted scrotal circumference from liveweight and age was 25 and 30 mm, respectively. Scrotal circumference by liveweight relationships have a similar pattern across all breeds, except in Waygu, with a 50 to 70 mm range in average scrotal circumference at liveweights between 250 and 750 kg. Temperate breed bulls tended to have higher scrotal circumference at the same liveweight than tropically adapted breeds. Five groupings of common beef breeds in Australian were identified, within which there were similar predictions of scrotal circumference from liveweight. It was concluded that liveweight and breed are required to identify whether scrotal circumference is within normal range for Australian beef bulls that experience a wide range of nutritional conditions.