It would not be difficult for weight gain but it will be difficult for bodyweight. So he is looking for the paper now.
I would make estimates using if
IF bodyweight is % chg, there will be % NE chg
IF weight gain is % chg there will be % NE chg
Combining both in the model, I will make 2 calculations
1. At each time point, the NE is based on bw
2. At intervals, the NE is based on gain.
is 100 weight gain for young calf is similar as older calf? Do they require same NE?
The calf have rations, which nicely given based on weight and weight gain. The rations was split to 2 rations, that I need to split for NE calculated above. But I also need rations if Milk replacer was given. Then I can easily divide the NE to 3 different rations.