Metabolizable Energy (ME) Requirement For Suckling Goats

Most observations used to determine ME requirements of suckling or preweaning goats were from dairy breeds (Luo et al., 2004). Although, no difference was detected among the different biotypes in the database. Therefore, these requirements can be applied to different types of goats. Because of the manner in which data were reported in studies, it was not possible to directly assess possible differences among genders. Hence, based on NRC (2000), it was assumed that the maintenance ME requirement for females and male castrates is 92.5% of the estimated value (485 kJ/kg body weight^0.75, and that for intact males is 107.5%. Maintenance ME requirements include an activity energy cost typical of confinement rearing systems for suckling goats. The body weight gain requirement is 13.4 kJ/kg.

Our example would require a total of 3.23 MJ of ME (1.89 MJ for maintenance and 1.34 MJ for gain).

After determining the total ME requirement, it can then be divided by the concentration of ME in milk or milk replacer to estimate the quantity of milk required, as shown below. For example milk concentrations noted by Nsahlai et al. (2004) for different goat breeds and stages of lactation, click on this button:

The formula used immediately above to predict the concentration of ME from fat is: MJ/kg = 1.4694 + (0.4025 x milk fat %) (e.g., 3.0% fat = 2.677 MJ/kg; 3.5% fat = 2.878 MJ/kg; 4.5% fat = 3.281 MJ/kg; 5.0% fat = 3.482 MJ/kg). In our example, the requirement of 3.23 MJ divided by 3.079 MJ/kg (i.e., 0.736 Mcal/kg; 1 MJ = 4.184 Mcal) of 4% fat-corrected milk indicates need to feed or consume 1.05 kg of milk.

Likewise, intake and ME concentration of supplemental dry feeds would need to be considered. For example, for this 15-pound female to gain 150 g/day, a total of 3.90 MJ/day of ME is required (1.89 MJ for maintenance and 2.01 MJ for gain). If the kid consumes 68 g/day (dry matter) of a starter feed with a ME concentration of 12.552 MJ/kg (dry matter; 3.00 Mcal/kg), then 0.989 kg of 4% fat-corrected milk is required. This is derived by subtracting ME of the starter diet consumed (0.068 kg x 12.552 MJ/kg = 0.854 MJ) from the total ME requirement, and then dividing by the ME concentration in milk (3.90 MJ of ME required - 0.854 MJ from starter diet = 3.046 MJ needed from milk; 3.046 MJ from milk / 3.079 MJ/kg of 4% fat-corrected milk = 0.989 kg of milk).

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 crude protein and fiber fractions.