ABSTRACT
The present study focused on energy and protein metabolism in pregnant and lactating mares, including the suckling and weaned growing horses, in order to determine feed availability, as also the energy and protein requirements. The authors found that the feeding diets, consisting of alfalfa hay, oats and compounds, had different availability values in terms of energy and protein, according to animal physiological conditions and age. Thus, the pregnant mares utilized the metabolizable energy (ME) and digestible crude protein (DCP) intake in average proportions of 64.5 +/- 3.2%, 54.6 +/- 3.0%, respectively, while in the lactating mares the values were 60.1 +/- 2.8%, respectively, 50.1 +/- 4.0%. However the amount of energy and protein required for maintenance was similar in these two animal physiological conditions: 531 kJ, ME/kg0.75, 529 KJ, ME/kg0.75 and 3 g DCP/kg0.75, respectively. The suckling colts had a daily average gain between 1405 and 891 g and the young horses after weaning up to 2 years of age between 773 and 447 g. The net efficiency of ME and of DCP for growth in the suckling colts was of 40.6 +/- 2.1% and 46.1 +/- 3.2%, respectively and in young horses after weaning had similar values of 40.3 +/- 4.0%, respectively 44.4 +/- 2.2%, but the maintenance requirement of energy and protein differed from 506 kJ, ME/kg0.75 and 4.51 g DCP/kg0.75 respectively to 587 kJ, ME/kg0.75 and 3.51 g DCP/kg0.75, respectively.
