A Cow a Calf Will Be

by W. W. SWETT

A DAIRY calf takes about 3 years to develop into a milking cow and prove her worth as a producer. That means 3 years or so of her owner's time, labor, feed, barn space, money, and worry, and all the while he has little knowledge as to whether she will be a profitable milker or whether she will be fit only for the butcher. If he could know that when the calf is a few months old he would make tremendous savings—in fact, if all American dairymen could foretell the future of the calves they plan to add to their herds, they would save much of the 250 million dollars they spend each year in raising the heifers that turn out to be unprofitable producers.

There are other reasons why the information would help. The chances are that half of these money-losing culls have left daughters that will prove to be no better. If the farmer could identify potentially high producers early enough, he could better plan a program of herd replacement and improvement. Persons who choose calves for boys' and girls' club members could buy younger animals at lower prices and be assured of getting animals of which their young owners might be proud. Cattle breeders would be able to evaluate roughly the transmitting ability of young herd sires at least 2 years earlier than is now possible.

After years of research, we have a promising basis for prejudging a calf by examining the glandular development in her udder when she is only 4 months old.

To start with, too much attention has been paid to the external size and appearance of the udder. It has long been a common practice to favor a large udder in the young dairy heifer; in the show ring, the judge is apt to take a general look at the udder, maybe pass his hand over its sur­face, and, other factors being equal, give the top award to the heifer with the deep, broad, level udder that is carried well forward and to the rear. Yet there seems to be little evidence that these prize-winning yearlings develop into superior milkers; there is some indication that they do not. Here is shown the mammary gland development of a calf from birth to 18 months of age. Following through from upper left to right: At birth the udder is in the tubular stage, each quarter containing a string-like formation that extends from the teat up toward the body wall. Enlargement begins at about 1 month; at 6 weeks or so a bulge can be felt near the center of each tubular formation. Between 2 and 3 months these bulges develop into firm, oval-shaped bodies and is called the quarter stage. At the 3- to 4-month stage, note that the quarters are shaping up to fit the abdominal wall. From 4 to 6 months the front and rear glands usually make contact and grow together at the base and continue to develop in all directions and fuse together more and more. Although the front and rear quarters appear to be completely fused together at the later half stage, they actually remain as four separate milk secretion systems for the cow's lifetime.

A careful examination of the udders of a number of young heifers by feeling through the skin with the fingers demonstrated that external appearances may be deceptive. Some udders that appeared to be well developed contained little glandular tissue. Others that seemed to be small and undeveloped when viewed externally contained well-developed glands. Fat deposits and the relative position of the glandular formations in the udder affected its external appearance. Marked variations were found among individual calves with regard to mammary development at a given age—in other words, some were advanced, and some were retarded.

To determine the significance of these individual variations, to learn whether advanced development indicated superior production, we began examining the mammary glands of every heifer calf in the Beltsville herd periodically at ages from a month to 18 months. When approximately 100 Holstein and 100 Jersey calves had been examined at each of these ages, an average or standard for each breed was established as a basis for grading other calves in the herd as they reached any given age.

Then analyses were made to determine the relation between the grades assigned to represent the relative degree of advancement and the amount of milk they were able to produce as cows. Fifty-two Holstein and 45 Jersey cows that had been thus graded as calves had completed records of production for at least one lactation period. We found that the calves that were advanced in mammary-gland development at about 4 months of age could produce in the neighborhood of 4,000 pounds more milk, on an average, than those that were retarded in mammary-gland development at the same age. We believe these preliminary findings may offer the indicator dairymen have been looking for.

Our diagrams illustrate the various stages of development to be expected at specified ages. It is of interest that all of the rudiments of the mammary glands are present in calves only 3 months old. The teat canal, the cistern, and the ducts leading from the cistern are definitely formed and can be seen in dissected specimens without magnifying them.

Up to 1 year there is little difference between Holsteins and Jerseys. The Jerseys appear to reach a given stage slightly younger, but there is no significant difference in the size of the glandular formations of the two breeds. Only a limited number of observations have been made on calves of other breeds, but there does not seem to be any marked breed difference in the form or in the rate of their mammary development. Until the breed standards were available, there was no satisfactory basis for evaluating these variations. These yardsticks make it possible to establish a systematic basis for grading individual calves at any age. Nine grades are used, in which nine represents the extreme of advancement, one the extreme of retardation, and five the average. Grades of six, seven, and eight represent degrees of advancement, and four, three, and two represent degrees of retardation.