To estimate the dietary ME concentration, often feed tags list the Total Digestible Nutrient (TDN) concentration. Likewise, most commercial feed laboratories estimate the TDN concentration based on various analyses, such as for CP and fiber fractions.
The approach used to develop predictions of voluntary DM intake
by goats was based on an assumption of constant overall efficiency
of utilization of ME. Therefore, ME
requirements from another study of this project were employed,
along with assumptions of efficiencies of ME utilization.
In accordance, inputs necessary to predict intake entail factors
influencing the partitioning of energy for use in various
physiological functions, including production levels. Although this calculator will predict feed intake with negative tissue gain and use mobilized tissue energy to support mohair fiber growth, the majority of observations in the database used to develop the prediction equations had positive tissue gain or values only slightly less than zero. Hence, caution should be employed when predicting intake with substantial tissue loss. It is also
important to note that input of an unreasonably high level
of production given the characteristics of the animal and
nature of the diet will result in a comparable unlikely estimate
of feed intake.
Data on which this calculator is based were from
goats in pens or stalls, not in late gestation or lactation, and not experiencing
appreciable compensatory growth or effects of acclimatization.
Correspondingly, adjustments of the maintenance ME requirements
available in other calculators are not employed here. Therefore,
caution should be exercised if using this calculator to predict feed intake in early lactation or to determine
if an estimate of feed intake based on a ME requirement calculator
with the maintenance requirement being substantially affected
by adjustments is likely or not. However, some adjustments can be used with the Option B Calculator "Feed Intake with Adjustments of the Maintenance Energy Requirement - Angora Goats."
Examples of predictions of voluntary DM intake for a 35-kg Angora doe consuming a diet containing 9 MJ/kg DM of ME and 12% CP, gaining 25 g/day of non-fiber tissue, and producing 5, 10, and 15 g/day of clean mohair fiber are 0.96, 0.98, and 1.00 kg/day, respectively.