Studies concerning energy and metabolism in horses

The authors studied the energy and protein metabolism in pregnant and lactating mares, young suckling horses, and young weaned horses up to 2 years of age, belonging to the Romanian semi-heavy breed. The following results were obtained: 1. With pregnant and lactating mares fed diets based on alfalfa hay, oats and mixed feeds, the efficiency of feed utilisation as digestible energy ranged between 56.8 + or - 1.10 and 61.1 + or - 2.1 percent and 56.6 + or - 1.3 percent and 64.1 + or - 1.12 percent, respectively; the efficiency of feed utilisation as metabolizable energy ranged between 48.8 + or - 2.1 percent and 51.4 + or - 1.9 percent and between 47.5 + or - 1.2 percent and 53.7 + or - 1.2 percent, respectively. Pregnant mares used the metabolizable energy and digestible crude protein in the feed at levels of 64.5 + or - 3.2 percent and 54.6 + or - 3.0 percent, respectively: the energy and protein requirements for maintenance were 531 KJ, ME/kg0.75 and 3 g DCP/kg0.75, respectively. The energy and protein requirements for maintenance and pregnancy were determined from two parabolic equations (equations 3 and 4). Lactating mares had milk yields ranging between 26.27 and 13.66 kg by using the metabolizable energy and digestible crude protein in the diets at levels of 60.1 + or - 2.8 percent and 50.1 + or - 4.0 percent, respectively; the energy and protein requirements had virtually similar values to those found in pregnant mares (529 KJ/kg0,75; 3 g DCP/kg0.75). 2. Young suckling horses which received the same feed additions as their mothers, had a daily gain ranging between 1405 and 891 g by using 93.50 + or - 0.2 to 68.9 + or - 0.39 percent of the feed as digestible energy, and 83.8 + or - 1.74 to 56.8 + or - 2.02 percent as metabolizable energy. Metabolizable energy content of the feed was used as energy for the gain at levels of 40.56 + or - 2.1 percent, and digestible crude protein, at levels of 46.1 + or - 3.2 percent. The energy and protein requirements for maintenance were 506 KJ/kg0.75 and 451 g DCP/kg0.75, respectively. 3. Young horses after weaning up to 2 years of age fed diets based on alfalfa hay, oats hay and straw, mixed feed and oats, had average gains of 592 g/day by using the feed at levels of 65.6 + or - 1.1 to 57.9 + or - 0.9 percent as digestible energy, and 55.3 + or - 2.1 to 49.1 + or - 1.0 percent as metabolizable energy. Metabolizable energy and crude protein content of the diets were used in proportion of 40.3 + or - 4.0 percent and 44.4 + or - 2.2 percent, respectively. Energy and protein requirements for maintenance were 587 KJ/kg0.75 and 3.51 g DCP/kg0.75, respectively.