SEASONAL-VARIATION IN VOLUNTARY FEED-INTAKE AND GROWTH IN CASHMERE BUCKS FED AD-LIBITUM DIETS OF LOW OR HIGH-QUALITY

The effects of season and diet quality on voluntary feed intake and gr owth were examined in mature cashmere bucks over a 16 month period at Wollongbar (29 degrees S., 153 degrees E.). Three-year-old bucks were individually housed under natural photoperiod and fed ad libitum diets of High (pelleted lucerne, CP 17.6%, ME 8.3 MJ/kg) or Low (pasture ha y; CP 6.9%, ME 6.6 mJ/kg) quality, between July 1988 and Oct. 1989 (n = 6/treatment). Bucks on both diets exhibited a seasonal pattern in vo luntary feed intake with maximal intakes during spring and summer, and minimal intakes during autumn. The pattern appeared to be circannual with high intakes during spring of both years. Liveweight also varied with season peaking in mid to late summer and reaching a seasonal nadi r in late autumn or early winter. Change in liveweight was closely ass ociated with digestible energy intake (r = 0.87, P < 0.001) resulting in a growth cycle closely resembling that of voluntary feed intake. In both treatments, bucks lost weight throughout autumn, while growth ra tes were maximal between mid-winter and mid-spring. Diet quality did n ot alter the magnitude of the autumnal decline in liveweight with buck s losing 7.6% (Low) and 7.8% (High) of liveweight during this period. However, bucks on the high quality diet exhibited significantly elevat ed growth rates between mid-winter and mid-spring. We conclude that ma ture cashmere bucks exhibit an annual growth cycle with weight loss du ring autumn and maximal weight gains mid-winter and mid-spring; that t he growth cycle is driven primarily by changes in voluntary feed intak e; and that increasing diet quality does not reduce the autumnal decli ne in liveweight but significantly increases liveweight gain during th e seasonal peak in growth.