With the advent of nutrition science and the expansion of livestock farming, intensive dietary standards were developed based on nutrients in foodstuffs as well as livestock requirements at every stage of life. The correct estimation of animal nutritional requirements and the accurate analysis of foodstuffs are two important factors for rationing, since dieting is not the only way to meet the needs of nutrients with nutrient levels. The fact is that the difference in the nutrient content of feeds is not a situation that everyone considers in feeding dairy cows. However, many nutritionists have not looked at why two similar feeds may have different compositions. The difference in the composition of a feed can be divided into three major sources:
- Analytical
- Sampling
- True or real variation