THE EFFECT OF HOUSING AND FOOD RESTRICTION DURING WINTER ON GROWTH OFMALE RED DEER CALVES

Low winter growth is a characteristic of male red deer and is caused, in part by a combination of reduced appetite and higher energy expendi ture due to cold weather. This study aimed to determine whether housin g during winter could reduce energy expenditure and increase the growt h rate of male red deer calves. An additional aim was to investigate w hether food restriction in winter would be compensated for by increase d spring growth. In each of two consecutive years, 80 calves were rand omly allocated to eight groups (no. = 10) comprising two replicates of four treatments during winter. Groups were housed inside (I) or outsi de (O) and given food either ad libitum (AL) or restricted (R) to main tain live weight. Winter treatments (southern hemisphere) ran from 12 May to 25 August (year 1) and from 5 June to 5 September (year 2). Dur ing these periods, animals were weighed weekly and group food intake r ecorded daily. At the end of winter animals were moved outside onto pa sture and weighed monthly until the end of spuing (27 November, year 1 and 7 December, year 2). In year 2 weighing continued during summer, until 4 April. The animals were slaughtered on 28 November and 18 Janu ary (year 1) and 5 April (year 2). The effect of housing on live-weigh t gain (LWG) and dry-matter intake (DMI) in AL groups was not signific ant in either year. However in R groups, O had a higher DMI than I in both years (P < 0.05) and a higher LWG than I in year 1 (P < 0.05). LW G was lower in R than in AL groups in winter in year 1 (P < 0.05) and year 2 (P < 0.001) and live weight was lower in R than in AL groups at the end of winter in both years. Live weight was still lower in R tha n in AL groups at the end of spring in both years (P < 0.01). In year 2, this live-weight difference was not significant by the end of summe r. Hot carcass weight (HCW) was greater in AL animals than R animals ( P < 0.05) and dressing proportion was higher in R than in AL (P < 0.05 ) in year 1. GR (an index of body fatness) was greater (P < 0.05) in O than I in year 1 and was greater (P < 0.05) in AL than in R animals i n year 2. Differences in GR between treatments were not significant in either year, with HCW as a covariate. In conclusion, housing calves g iven food ad libitum during winter did not reduce DMI or increase grow th rate. When normal growth rates were prevented by restricting food i ntake, housing lowered DMI requirement, although such a situation is u nlikely to be a useful farm management practice as recovery from the g rowth check was slow. Annual variations in climate may determine both the food savings made by housing and the extent of compensatory growth of food-restricted animals in spring.