Producing Better Beefsteaks

by RALPH W. PHILLIPS

NO FORMULA can assure an adequate supply of beef at all times, although something like 15 million head of cattle are slaughtered every year in the United States to provide for a per capita consumption of 70 pounds. We have no formula for making all cuts tender. But new research points to many ways in which beef breeding and production can be improved. These include improvement in reproduction, efficiency of selection procedures, breeding methods, utilization of feeds, and management practices.

Cattle breeders use selection as a chief tool to improve their stock. They choose what look to be their best animals and mate them, hoping for offspring better than the parents. Of course, the point hinges on "best" and "better," for many factors of heredity are not apparent to even the trained eye of the cattleman or, indeed, the trained geneticist. The extent to which selection can improve cattle is determined largely by the degree to which the characters selected for are inherited. Many pairs of genes, the units of inheritance, are responsible for the inheritance of each of the characteristic's that cattle breeders would like to see in all their Young stock, like heavy weight when born, ability to grow fast, and tenderness of the steaks when the steer is slaughtered.

Bradford Knapp, Jr., of the Department, and Arne W. Nordskog, of the Montana Agricultural Experiment Station, studied the records of 177 steer calves sired by 23 bulls, and determined that several traits vary in the degree to which they are passed on from one generation to another. These figures for heritability—the degree of persistence of characters in successive generations—actually indicate the progress that a cattle grower should be able to make by selection in his herd. If the weight of calves at weaning time is 12 percent inherited, for example, and a cattleman chooses for breeding a group of animals that are 10 pounds above the average of the herd in weaning weight, the offspring of those selected animals should average about 1.2 pounds more in weight than offspring of the breeding stock if no selection for this character had been made.

Some of the estimates of heritability seem too high in view of the results with other classes of livestock and the probable effects of environment on final weight, rate of gain, and efficiency of gain in the feed lot, and so on. Pending further investigation, the figures cannot be taken as generally representative, but they do indicate that selection should be effective in improving many characteristics. Conversely, they indicate that selection for higher dressing percent would not be effective.

If selection is to be based on characters other than those that a stockman can see, he needs measures of performance--yardsticks that he can apply to his animals. Measuring performance in beef and dual-purpose cattle is complicated. Measuring milk production is relatively simple, because milk can be weighed and the percentage of butterfat found. Weighing meat animals tells us their rate of gain, but efficiency of feed utilization, value of the live animal when ready for slaughter, merit of the carcass, and milk production in beef cows that are nursing calves are more difficult to determine.

Several men have tried to determine the relationship between the rate at which a beef animal gains weight and its ability, or efficiency, to turn feed into flesh. Knapp, J. R. Quesenberry, and R. T. Clark drew the conclusions from their study in 1941 that rate of gain and efficiency of feed utilization may not be highly correlated when all steers are fed for the same period; and that neither efficiency of gain nor rate of gain in the feed lot can be accurately predicted from rate of gain during the suckling period or from score on conformation at weaning time.

Knapp and A. L. Baker of the Department later studied 66 steers that were fed individually for 273 days, and obtained a correlation of 0.49 between rate and efficiency of gain. The steers weighed 298 to 492 pounds at the beginning of the feeding period and 759 to 1,134 at the end. After suitable corrections for differences in weight, the correlation was 0.83. The men concluded that comparisons of gross efficiency should be made only between animals of the same size and that selections based on gross efficiency are misleading when all animals are fed for the same length of time.