Influence of level of feeding and physiological state on diet digestibility in light and heavy breed horses

Abstract

Four heavy-breed dry mares and five adult geldings of light breed were fed at maintenance level and ad libitum, successively, to determine the influence of feeding level and breed on digestibility. Five heavy-breed mares were fed the same diet ad libitum in late pregnancy (ninth-tenth months) and in early lactation (first and second month) to measure the effect of feeding level and physiological state on digestibility. The animals were fed a diet containing fixed proportions of 85% meadow hay (33.2% crude fibre, 8.0% crude protein in dry matter) and 15% concentrate based on barley (50%) and soybean meal (45%). Intake was adjusted daily for each animal. Diet digestibility was measured by analysis of total faeces collected over a 6-day period in dry heavy-breed mares and light horses fed successively at maintenance level and ad libitum. The same measurements were made in pregnant and lactating mares during the fifth week before and the fifth week after foaling. Diet digestibility was not significantly changed by increase in feeding level. However, it was significantly lower in pregnant mares than in lactating mares and in dry mares fed ad libitum, for dry matter (4.4 and 2.3 points), organic matter (5.0 and 3.5 points) and energy (4.1 and 2.0 points). The differences are due to a lower digestibility of total crude protein content (5.4 and 3.2 points) and crude fibre (3.5 and 3.0 points). Breed had no significant influence on digestibility.