Feeding fat can help fuel cattle
by Dr. Jim White, MFA Director of Livestock Nutrition
Type of fat must be taken into consideration. Various fat sources can affect the net energy of the diet differently, resulting in variation in animal performance.
A limited amount of supplemental fat can be an excellent way to increase the energy density of the diet for beef cattle herds. Pound for pound, supplemental fats contain more than two times the net energy 
of cereal grains and provide essential fatty acids that play a key role in physiological functions such as immune health and reproductive performance.
A variety of fat sources exist that can be included in beef diets, such as oilseeds, grains, rendered animal byproducts or yellow grease from the food service industry. The accompanying table shows examples of the net energy value of tallow and soy oil compared to corn and whole soybeans.
Once consumed, fats go through a structural change in the rumen called biohydrogenation. This change can lead to an increase in the amount of propionic acid, one of the major volatile fatty acids produced and a precursor to glucose. Increased propionic acid production provides more energy to the animal.
Using fat in finishing cattle rations is known to improve feed efficiency, but the performance response is quite variable. Type of fat must be taken into consideration. Various fat sources can affect the net energy of the diet differently, resulting in variation in animal performance.
Quality of the fat source must also be considered. Measurements of quality include moisture, rancidity, percentage of free fatty acids and toxic compounds. Lower-quality fats can have a negative effect on palatability and feed intake.
Another factor to consider is level of supplementation. As dietary fat levels increase, intestinal digestion and absorption of fat decreases. Increased levels of supplemental fat can result in reduced dry matter intake, negatively affecting performance. For these reasons, fat supplementation levels should not exceed 5% to 6% in finishing diets for cattle. This is different than with hogs, which can effectively use a higher fat content in their rations than cattle.
The reproductive performance of beef cows is impacted by their dietary energy intake and body condition. Feeding fat increases dietary energy density, and it can have positive effects on reproduction when fed at specific times during gestation. Supplementing fat to cows during the final 60 days of gestation can improve pregnancy rates the following breeding season, whereas fat supplementation during the postpartum period does not affect pregnancy rate.
Cattle on high-forage diets can only consume a limited amount of supplemental fat. Increased fat in the diet results in decreased ruminal fiber digestion. Therefore, the amount of supplemental fat in high-forage diets should be limited to 3% to 4% to ensure no negative effects on digestibility occur.
Calves born to mothers supplemented with fat 60 days before calving have a greater response to cold stress and a higher survivability rate compared to calves born from unsupplemented cows. If calves are expected to be born in adverse weather conditions, feeding fat to their mamas during this period can be an effective strategy to help newborns combat the environmental challenges.
There is still a lack of information about whether fat supplementation increases the pregnancy rate of replacement heifers or if fat supplementation is of little value in a well-developed replacement heifer program. However, there is an indication that fat supplementation can result in positive physiological changes when heifers are supplemented 60 to 90 days prior to the breeding season to increase pregnancy rate.
Additionally, producers should consider body condition. Over-conditioned heifers fed diets with supplemental fat can have delayed estrus compared to heifers in adequate body condition. Replacement heifers are typically fed high-forage diets during the growing phase. As with mature cows, fat supplementation for replacement heifers should not exceed 4% of the diet’s dry matter to limit negative effects on fiber digestion.
Visit with your MFA solutions provider to learn more about supplementation options and effective feeding programs for your cattle this winter.