By Dr. Roy Burris, Beef Extension Professor, University of Kentucky
Is fat a bad word? Not necessarily. Simply put, fat is just the body’s storage form of energy. If an animal consumes more energy than it uses, the excess calories will be stored as fat – money in the bank to be used in an energy shortage (think cows calving in late winter). Fat also imparts flavor to food (like a T-bone steak) but it also adds calories. So managing fat can be a delicate issue in the cattle business.
Presently, eating quality of beef is estimated to a large degree by the amount of marbling (intramuscular fat) that it contains. Tenderness is also important but is generally a function of age (younger is better). Marbling generally increases after the animal attains some maturity and external fattening has occurred. External fat is frequently used as an indication of when cattle will have enough marbling to grade choice or prime. I know what you are thinking – why don’t we just measure marbling. We’re getting to that with ultrasound technology and it would allow us to avoid over finishing (high yield grades) of fed cattle.
Ideally, marbling would occur in feedlot cattle with very little external fat being present. We would like to have Choice and Prime quality grades with yield grades of 2 or 3 for our fed cattle. But . . . If we bred cattle to meet this criterion, what would it mean to the beef cow herd? Don’t ever take fleshing ability away from the brood cow herd! It will have a negative effect on reproduction.
It is important to understand how cattle fatten so that we can manage cattle accordingly. Fat is “laid down” from front to back and top to bottom. The fore ribs and spinous processes are covered first then the fat cover continues backward and downward. That’s why folks look for cod fat (in the scrotal area) as an indicator of when cattle are finished. It is the last place to fatten. Loss of body fat happens in reverse order. Fat cover is the basis for condition scoring in beef cattle.
Body condition has a definite impact on reproductive performance. Cows should generally be at a Body Condition Score (BCS) of five at the beginning of the breeding season. A cow with a BCS of 5 will have some fat reserves – with fat cover over all the ribs. As cows lose condition (in the reverse order that it was put on) a BCS 5 would become a BCS 4 when they lose condition so there is no cover over the last two ribs. This would mean that the cow has very marginal energy reserves for good reproductive performance. If this loss of condition (fat reserves) continues so that you can see the foreribs (BCS 3), then you have a real problem. Conception rates will suffer.
Loss of condition generally happens after calving when dietary energy needs have increased dramatically and feed supplied isn’t meeting those needs. The cow has to “withdraw, from the bank” to meet her nutritional needs. It is important that some energy reserves are available.
And what about the herd bulls(s)? We need some energy reserves so that bulls can stay active during the breeding season but … bulls are athletes. They should have muscling, sound feet and legs and be able to sire a large number of calves in a short period of time. At least that is what we say we want but then we frequently buy young, fat bulls that look great at the start of the breeding season and are a wreck before the season is over.
Why does this happen? Probably because we confuse fat with muscling. We are looking at thickness as a sign of muscling but it could just be a layer of fat. Fat can “plaster over” thin-muscled cattle. Fat doesn’t move but muscles will “ripple”. Watch the animals as they move. Observe the hindquarters and shoulders. Remember – “if it ain’t movin’, it ain’t muscle”!
So managing fat (or condition) is important in the cattle business, especially in the cowherd for optimum reproduction. Fat is important – both too much or too little can be a problem. Astute producers recognize the importance of efficient cattle that can maintain adequate energy reserves without wasting feed resources.