For lactating dairy cattle, sampling feeds monthly or whenever the ration changes is a good rule of thumb. However, when feeds have a high degree of nutrient variation, more frequent testing is needed for dry matter and the major nutrients (protein, energy, and fiber) with ration adjustment as needed. Since forages are usually more variable than grains, they usually should be analyzed regularly. More frequent testing can sometimes be justified with larger dairy herds by reducing over- and underfeeding.
Charles Stallings,
Dairy Science, Virginia Tech
