Influence of nutrition on testicular growth in Corriedale rams during spring

To study the effect of nutrition on spring testicular growth, four adult Co rriedale rams were allowed to graze enough to maintain weight (maintenance group), while another fi,ur rams, in addition to forage, received a supplem ental grain-based ration (increased gradually from 100 to 400 g during the first 5 d and kept at 400 g thereafter) daily for 63 d (supplemented group) . Body weight, scrotal circumference, inguinal hyperaemia and testicular co nsistency were assessed. Blood concentrations of LH and testosterone were m easured for 24 h on the day before supplementation began, the day after the animals were fed 200 and 400 g, and 12 and 28 d after animals began to rec eive the supplement. On these occasions blood contents of non-esterified fr ee fatty acid and beta-hydroxybutyrate were measured when animals were fast ing. Supplemented feeding increased body weight within 21 d and scrotal cir cumference within 35 d (P < 0.01). Scrotal circumference also increased in rams of the maintenance group (P < 0.01) but a lower rate than the suppleme nted group (P < 0.001). In both groups, testicular consistency and inguinal hypereamia increased (P < 0.01). In the supplemented group a transient inc rease (P < 0.01) in LH pulsatility occurred the day after rams had received the full supplement (400 g) and 5 d later(day 12). However, no difference was found in total testosterone release between groups. In conclusion, impr oved nutrition accelerated the testicular growth in spring, although only a transient increase in LH pulsatility was observed. The scrotal circumferen ce of rams kept on maintenance diet did also increase, which indicates that nutrition is not the only environmental cue responsible for the vernal tes ticular redevelopment in Corriedale rams. (C) Inra/Elsevier, Paris.