While the use of milk ingredients in brood cow diets is unusual, these feed ingredients can be used as supplemental carbohydrate sources. Under certain economic and weather conditions, such as government drought relief program, cattle producers may have the opportunity to incorporate milk ingredients into grazing brood cow diets. One such milk ingredient is nonfat dried milk.

Non-fat dried milk is the reside obtained by drying defatted milk and, typically, moisture level is limited to no more than 8%. Dried milk products are typically used in the feed industry in milk replacers and feeds for young animals. A typical analysis of dried skim milk (AAFCO terminology for dried skim milk is analogous to non-fat dried milk) is shown in Table 1.

Non-fat dried milk contains high levels of lactose (50%), a simple sugar, that is readily fermented in the rumen. This rapid fermentation of lactose can lower rumen pH and increase lactate production in the rumen, resulting in potential digestive disorders (namely acidosis).

This was evidenced in a SDSU study on the effects of lactose supplementation on rumen characteristics in sheep fed hay diets. Almost all of the lactose was fermented in the rumen, resulting in low pH and high lactate concentrations after meals, predisposing the sheep to acidosis.

Proper diet formulation is necessary to optimize the use of non-fat dried milk in the diets of cattle grazing pasture. Work conducted at KSU on the effect of supplemental carbohydrate source (similar in structure to lactose) on the utilization of low-quality, tall grass-prairie hay by steers shows the importance of sufficient degradable intake protein (DIP) in the diets. Researchers observed that when protein intake was inadequate, supplemental carbohydrates depressed fiber digestion; however, no depression in fiber digestion occurred when adequate supplemental protein was fed. Hence, the importance of ensuring diets provide sufficient DIP when feeding supplemental carbohydrates.

With proper nutritional management, non-fat dried milk can be used in grazing brood cow diets. Management suggestions for using non-fat dried milk in grazing brood cow diets include:

• With typical feeding situations, non-fat dried milk can be fed at 2 lb/hd daily without gradual introduction into the diet.

• If amounts greater than 2 lb/hd daily of non-fat dried milk will be fed, use a gradual step-up program to acclimate cows to non-fat dried milk.

• Supplemental DIP requirements must be met to optimize the use of non-fat dried milk for cattle fed forage diets.