Feed Intake with Adjustments of the Maintenance Energy Requirement - Angora Goats
(Non-lactating, Not in Late Pregnancy)
Feed intake prediction equations were developed from data with goats in confinement and without appreciable impact of factors such as acclimatization or grazing (Luo et al., 2004). Similarly, it was not possible to address gender. However, the physiological premise on which the equations were based suggests that they could be appropriately used with maintenance energy requirements adjusted for various factors. Therefore, it was felt desirable to include as an option a feed intake calculator that includes adjustments. But, since the efficiency of energy use for gestation is markedly different than for maintenance, feed intake would not necessarily be predicted accurately for a goat in the last 56 days of gestation. Also, because the method of intake prediction involved assumed efficiencies of energy metabolism for different functions and maintenance energy requirements, an adjustment for body condition score as influenced by previous nutritional plane, which may influence both factors, was not included. Other considerations mentioned for Option A, such as doubtful accuracy in early lactation and suggested caution when there is considerable tissue loss and unlikely predictions with unreasonable inputs, are applicable for this option as well.
Let's assume a 35-kg Angora with 0 tissue gain or loss and 11 g/day of clean mohair fiber growth is consuming a diet with 11% CP and 11 MJ/kg dry matter (DM) of metabolizable energy (ME). For these conditions, based on the Angora Goat Feed Intake Calculator without adjustment of the maintenance energy requirement (Option A), predicted DM intake is 0.79 kg.
However, if we assume that this is a mature female goat, predicted DM intake is 0.79 kg. These adjustments were made assuming that the maintenance ME requirement is 5% less for mature than for growing Angora goats and 15% less for females and wethers compared with intact males.
If the maintenance energy requirement is then adjusted for a grazing factor of 1.13 (grazing plus walking time = 7 hours; distance traveled = 4 km; terrain score = 2), predicted DM intake is 0.88 kg.
If the maintenance energy requirement is also modified for an acclimatization adjustment of 0.12 MJ (average daily temperature for the previous 30 days = 18 degrees C; mid-point temperature of the thermoneutral zone = 20 degrees C), predicted DM intake becomes 0.89 kg.
The sources used in this calculation method are:
Luo, J., A. L. Goetsch, I. V. Nsahlai, T. Sahlu, C. L. Ferrell, F. N. Owens, M. L. Galyean, J. E. Moore, and Z. B. Johnson. 2004. Prediction of metabolizable energy and protein requirements for maintenance, gain and fiber growth of Angora goats. Small Ruminant Research 53:339-356.
Luo, J., A. L. Goetsch, I. V. Nsahlai, J. E. Moore, M. L. Galyean, Z. B. Johnson, T. Sahlu, C. L. Ferrell, and F. N. Owens. 2004. Voluntary feed intake by lactating, Angora, growing and mature goats. Small Ruminant Research 53:357-378.
NRC. 2000. Nutrient Requirements of Beef Cattle, Update 2000. National Academy Press, Washington, DC.
Sahlu, T., A. L. Goetsch, J. Luo, I. V. Nsahlai, J. E. Moore, M. L. Galyean, F. N. Owens, C. L. Ferrell, and Z. B. Johnson. 2004. Nutrient requirements of goats: developed expressions, other considerations and future research to improve them. Small Ruminant Research 53:191-219.