Longitudinal growth analysis of horses following limited and ad libitum feeding

Eighteen colts were assigned to one of two groups: limit or ad libitum feeding. Three periods were evaluated: 1) six to 12 months, 2) 12 to 18 months and 3) 18 to 24 months of age. At 24 months of age, ad libitum fed horses weighed 13 per cent (51 kg) more and were 3.6 per cent (5.2 cm) taller than those fed limited amounts. Total, fore and hind body mass increased quadratically irrespective of dietary treatment. Fore body mass comprised 57 per cent of total body mass for both groups and this did not change with age or dietary treatment. Heart girth was directly related (R2 = 0.96) to total body mass. Average daily gains in total body mass of ad libitum fed horses were 13 and 71 per cent more rapid (P less than 0.05) than for limit fed horses in Periods 1 and 3, respectively. Ad libitum fed horses gained hind body mass 25 per cent more rapidly (P less than 0.05) than limit fed horses only in Period 1. Growth curves of wither and croup heights were quadratic in form. Ad libitum fed horses gained 12 and 13 per cent more rapidly at the wither than limit fed horses in Period 1 and overall, respectively. Ad libitum fed horses grew 33 per cent more rapidly at the croup than limit fed horses but only in Period 2. From six to 12 months of age, the wither and croup grew two-fold and four-fold more rapidly than between 12 to 18 months and between 18 to 24 months of age, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)