Livestock: February 2002

Low-fat diets have been touted in the past as being a good way for human beings to lose weight.  Some recent research has found that the reverse logic is true for beef cows.  Adding fat to the diet of a cow before calving and/or before breeding can have some substantial benefits in several areas.

Fats are made up of chains of carbon atoms surrounded by hydrogen atoms called fatty acids.  This is a very efficient way to store chemical energy, and, pound for pound, fats contain about 2.5 times as much energy as carbohydrates, such as starch.  Fats can be classified as either saturated or unsaturated, depending on the carbon:hydrogen ratio.  Fats from plants tend to be unsaturated or poly-unsaturated, and these fats seem to have the most value for supplementing cattle.

Most nutritionists try to keep the level of fat in the diet of beef cattle at or below four percent.  Forages in the dormant season typically contain only one percent fat or less.  Therefore, there is some room to add a little fat to the diet without disturbing rumen function. 

Fats are a good way to supplement energy in cattle diets because they are extremely energy-dense supplements.  However, the beneficial effect of fat in a breeding cow's diet may extend beyond the simple nutritional value.  Fats are needed as precursors to several hormones, and increasing fat levels in the diet may stimulate hormones that control estrus, ovulation and early embryonic development.

To see the most effect of supplementing fats, focus on cows that need the most help.  These would be cows in low body condition score (4.0 or less on a nine point scale) or those consuming very low quality roughage.  Feed about 3.5 pounds of whole cottonseed or 1.5 pounds of high-oil sunflower seed per cow, per day.  Whole soybeans are also a good supplement.  In fact, if corn costs $2.50 a bushel and soybean meal is $250 a ton, whole soybeans are worth about $7 a bushel, based solely on the nutritional value.  Whole soybeans could be purchased in December 2001 for $4.80 a bushel, or $8/cwt.  Feeding three pounds per day, therefore, costs $0.24 per day.  Several commercial supplements also contain vegetable fats.  Remember that the cows will need adequate levels of forage, crude protein, vitamins, minerals and water.

Supplemental fat is not a silver bullet.  However, in situations where cows need a little extra help getting in shape for breeding time, supplemental fats can work well.