The net energy value of balanced diets for growing pigs

A new mathematical model for combining growth and energy intake in animals: The case of the growing pig

“…When a q value of 326 kJ/(day× kg 0.75 ) (Just, 1982) was used in the left plot, NE was overestimated in relation to measured NE intake. In the right plot, a q value was estimated from data by minimizing the weighted least sum of squares so that estimated NE would be in accordance with the measured NE intake.…”

“…The total net energy intake is calculated as the net energy content of the diets (Table 1) multiplied by the cumulated feed intake in the corresponding periods of use. For the present analysis, we assume that the methods for prediction of net energy contents of the seven diets (Just, 1982;Boisen and Fernandez, 1997) are valid in the entire growth period from 7 -450 kg BW. This is somewhat simplistic, but is nevertheless supported by the findings of Noblet et al (1994b).…”

“…The maintenance component ș 4 in the model was estimated to be in the range of 232 -303 kJ/(day× kg 0.75 ) with a mean of 268 kJ/(day× kg 0.75 ) and a CV of 8.6%. In net energy systems the maintenance component is usually estimated by regressing the daily energy retention or heat production on daily ME intake, then the intercept represents the maintenance requirement (Just, 1982;Noblet et al, 1994). (Table 4).…”

“…There are several explanations to this fact: 1) the maintenance requirement was represented by one parameter in the model and it is likely that this representation is to simplistic because the chemical composition of the body, organ size etc. changes during the course of growth (Tess et al, 1984); 2) fasting heat production measurements are usually conducted in the BW range of 20-110 kg and thus little information is available beyond this point; 3) the net energy contents of the seven diets used in the present study were calculated from dietary characteristics using the method proposed by Just (1982) and Boisen and Fernandez (1997). We will direct focus towards estimating a maintenance requirement based on slaughter data because these can be used for validation.…”

“…If complete records of growth and energy intake trajectories from individual animals are available, estimation of model parameters could be possible. In the following, we define dietary energy as net energy because net energy systems are currently the recommended energy evaluation system for formulating diets for growing mammals (Just, 1982;Noblet et al, 1994a;NRC, 2000).…”