Title: The Effect of Frequency of Ejaculation on the Semen Production, Seminal Characteristics, and Libido of Bulls during the First Post-Puberal Year
Abstract: With the rapid expansion of artificial insemination to the point where thousands of cows are bred to a single sire in a year, it becomes imperative to prove and select sires as early as possible in order to maximize the use of those proven desirable.The usual recommendations are that bulls should not be placed in service at less than 1 year of age and that they be used for not over 25 services during the first year of service.Following these practices, it is possible to prove a bull by the time he is 5 years old, though seldom do sufficient progeny complete lactations to make the proof reliable before the bull is 6 years old.Sperm have been found in the testes of the bull as early as the 224th day (13).This finding suggests the possibility of placing bulls in service earlier than the usual recommendation.The limits of usage consistent with satisfactory fertility in bulls have been studied through surveys of breeding results of bulls being used at various intervals, and by planned experiments.In studies of the first type, Dawson (4) found fertility to be related to the number of services in the preceding month, and Lasley and Bogart (9) found positive highly significant correlations of fertility with the interval from the previous service.In contrast to these reports, Ellenberger and Lohmann (5) found neither the interval from the last ejacula-