Effect of castration at 10 months of age on growth physiology and behavior of male feral beef cattle

This study compared the growth performance, plasma testosterone and cortisol levels around castration at 10 months of age, and plasma insulin‐like growth factor (IGF)‐I concentration and flight speed, in intact bulls and steers from 10 to 21 months of age in a feral Spanish breed. Fourteen bulls (366.5 ± 48.5 kg live weight) were assigned at random to one of two treatments: surgically castrated (steers) or intact (bulls), and submitted to an identical fattening period. Steers reared until heavy live weights (21 months of age) grew slowly and had lower plasma IGF‐I concentrations than intact bulls. These differences were mainly highlighted the month after surgery (11 months of age) and the last part of the fattening period (from 19 to 21 months of age). After surgical castration (11 and 12 months of age), steers showed a tendency to display greater flight speed values than intact bulls but baseline plasma cortisol concentration did not differ between groups at this time. At the end, steers and bulls reached nearly similar temperament, as flight speed did not differ between them. The results confirm the role of IGF‐I as a key anabolic hormone in male beef cattle and thus it may reflect growth differences due to altered sex steroids production.     

Erosion of the native genetic resources of brown trout in Spain

Abstract– We analyzed the introduction of hatchery-reared trout in the Riutort Creek, a small stream in the eastern Spanish Pyrennees. We used gene correlation matrices between individuals to analyze the fish coancestry in the Riutort Creek samples and in the hatchery stock. Hatchery fish disturbed the single ancestry in the native population of the creek, and were clearly detected with principal coordinate analysis of the gene correlation matrix. The amount of introgression produced by successful introductions was estimated from the principal coordinate analysis projections of the matrix of F_ST values between the putative native Riutort Creek population, the hatchery stock and the introgressed population. In only two years the amount of introgression rose to 10%, indicating that 5% of the native ancestry is lost each year as a result of the stocking program. Based on these results, we review the present understandings on the genetic impact of hatchery fish on indigenous Spanish brown trout populations. The stocking of these populations involves a non-native broodstock widespread through the Spanish hatcheries, but successful stockings appear to be limited to wild populations subjected to occasional releases in protected or unfished areas. Surprisingly, extensive stocking in fished areas result in a more limited genetic impact on the recipient native population.