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Abstract
Extract
Literature concerning a possible relationship between level of milk production and infertility in dairy cows varies in its conclusions. Most authors (Boyd et al., Citation1954; Crowley, Citation1959; Boyd and Reed, Citation1961; King, Citation1968) have found no significant differences in fertility between high and low producing cows or between herds with different average productions. Currie Citation(1956) compared the production of mature Jersey cows in New Zealand conceiving to first service with that of cows not conceiving to first service. There was no significant difference. A previous analysis of production and fertility in New Zealand cows (Anon., Citation1941) had suggested that fertility was higher in herds producing less than 280 lb of butterfat per cow per year, than in herds with a greater average annual production. Dawson Citation(1963) found that, of 18 Israeli dairy herds with infertility problems, all were above the national average in terms of milk production and 11 were in the top 25% of the nation's dairy herds. It was considered that the “stress” of lactation, especially in younger animals, had a considerable influence on subsequent fertility (Dawson, Citation1964).