Genomic evaluations of sheep in New Zealand

Many New Zealand equine owners/stud managers rely on body condition to adjust feed supply for weight management, rather than objective weigh scales. This cohort observational study examined the inter-relationship of pasture supply with monthly BCS and live weight (LW) in three groups (n = 7, 8, 9) of grazing-horses of median 6/9 BCS (range 4-8). Dry-matter (DM) intake was estimated from weekly pasture mass (using rising-plate meter), monthly pasture cuts, and fortnightly LW records. Total pasture DM at the start of grazing ranged from 559 to 3511 kg DM/ha, and grazed lawns (nutritive areas) ranged from 364 to 2601 kg DM/ha. Total estimated DM offered (including hay when offered) ranged from 1.46 to 26.37 kg DM/horse/day (0.3% to 5.3% of horses LW). Within-horse maximum monthly gains and losses were 8% LW and -13% LW respectively. Median monthly BCS change was 0/9 (range -2/9 to 1/9). There was no significant association between monthly changes in LW and BCS, indicating BCS may lack the sensitivity to manage weight. During periods of reduced DMI (below estimated maintenance) there were no significant decreases in LW or BCS. These data implied that the horses may have altered transit time to improve the relative digestibility of the limited feed on offer.