The Use of Records in Evaluating the Inheritance of Cows and in the Proving of Bulls

Abstract

In summarizing the results of both phases of the investigation, it seems apparent that given the opportunity and barring illness or injury, a cow capable of completing one good record should be able to complete a number of lactations with good yields and thus finish a lifetime with a creditable total production. This is not in any sense an argument against continuous year after year testing. Continuous testing is needed to prove bulls at the earliest possible age. Several records are often needed on many cows to secure one complete lactation in which everything including health, feeding and management, and climatic conditions are fairly normal. Records made following abortions, attacks of bloat, milk fever and mastitis infection, do not give a true picture of a cow's ability at all. Neither are the records made in some sections of the drouth area during recent years, a fair measure of a cow's actual ability. Furthermore, only by continuous testing can a breeder tell definitely when a cow has ceased to be a profitable member of the herd.Because of the necessity to assay the transmitting ability of bulls at the youngest possible age, it is impractical to compare lifetime records of daughters with the lifetime records of their dams. If we compare the average of several records on the dams with the first lactation records completed by the daughters, the results may be misleading. In selecting bulls, if the practice of comparing the highest record of the daughter with the highest record of the dam is used, no allowance is then made for the probability that the daughters will better their early records in later life and this method should improve the chance of a breeder being correct in selecting proved sires. In other words, an additional safeguard is furnished by insisting that the daughters of a bull in one or two trials produce as well or better than their dams were able to do in perhaps five or six trials.If a cow has completed one record of 600 or 700 pounds of butterfat, she obviously possessed the inheritance to produce that amount in a lactation, unhampered by illness, poor management, or drouth conditions and consequently it seems that one record, and preferably the highest record, is suitable for evaluating the sire's ability and in trying to measure the cow's transmitting ability. Breeding operations will be seriously handicapped if breeders are forced to wait until cows have finished a series of four or five or more records, in order to obtain worth while information as to the sire's ability or the cow's own possible transmitting ability.It also seems apparent from the data presented, that neither the highest record nor the average of several records gives a great deal of information concerning the cow's transmitting ability as measured by the correlation with the daughter's production. To attempt to measure this, additional information is essential, such as the records of a cow's sisters and the records of her daughters. In a previous paper by the author (5), it was concluded that the record of a cow together with the records of her daughters and the records of her sisters did give a fair estimate concerning her transmitting ability.Lifetime productions are largely influenced by longevity, opportunity, and perhaps to a certain extent, good fortune. Little if any data have been published concerning the inheritance of longevity. Unfortunately this is often not determined by nature. A high percentage of cows culled from the herds are removed due to disease infection. Is there any reason to believe that a cow, descending from a line of long-lived ancestors, is more immune to mastitis, Bangs’ infection, etc., than is the daughter of a cow living only long enough to complete one or two lactations? Udder attachment is also another factor affecting the length of time cows remain in herds and it may be that some cows with a high inherited producing ability have not inherited a sufficiently strong udder attachment to keep the udder from breaking away and becoming pendulous. However, feeding and management may also be partly responsible for udder troubles. The inheritance of high milk producing ability, longevity, breeding efficiency, disease resistance and strength of udder attachments, all contribute to the end product of profitable lifetime production. Yet, it seems that these are separate problems in themselves and the selection of the highest record of an animal is the best index as to that animal's actual inherited production capacity under normal conditions.