Effect of season and nutrition on scrotal circumference of Merino rams

Abstract

In 3 experiments, groups of 5 Merino rams were individually fed a pelleted ration at maintenance (1 kg/day), with or without 750 g/day of lupin grain, and kept indoors under conditions of natural light and temperature. Measurements of scrotal circumference and liveweight were made during winter, spring-summer and autumn, for periods of 42-49 days. Ambient temperatures and daylengths were recorded. The season of the experiment affected the rate of change of scrotal circumference. Rams fed the maintenance diet showed a pattern of increasing scrotal circumference, starting in late spring after the spring equinox and reaching a maximum in autumn-early winter, then decreasing in mid-late winter after the winter equinox. Scrota1 circumference responded to increased nutrition under all daylength regimes and the magnitude of this response was influenced by the season.