Red deer are seasonal and generally experience a period of low growth in winter. Previous research has demonstrated that individuals vary in the degree of their seasonality. Mechanisms that drive the differences in seasonality are not well understood. Six sires paired by 12-month weight estimated Breeding Value (eBV) but with contrasting seasonality were used to generate progeny to investigate the mechanisms that influence seasonal growth. Progeny were fed ad-lib on pasture year-round to allow expression of genetic potential with liveweight monitored fortnightly. Feed intake and efficiency were estimated during a 10-day period in each season. Analysis of seasonal liveweight gains indicated that predicted seasonal growth rates were repeatable within sire lines. Significant differences within paired sire lines in growth rates were expressed during winter for the two lower 12-month weight eBV paired groupings. Winter intakes were estimated to be lower than spring intakes although absolute values were considerably higher than expected. Variations in estimated feed efficiency between sire-line pairings were significant in all seasons apart from summer however, more research is required to correlate this estimation technique against actual feed efficiency. This research demonstrated that variation in the degree of seasonality between sires does exist and could be exploited for management decisions.

BR, Thompson, DR Stevens, JF Ward, KG Dodds, and GW Asher

New Zealand Journal of Animal Science and Production, Volume 82, Online, 50-56, 2022
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