The relationship between production and infertility in dairy cows

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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., 1954 Boyd, L. J. , Seath, D. M. and Olds, D. 1954. Relationship between level of milk production and breeding efficiency in dairy cattle. J. Anim. Sci., 13: 89–93. [Google Scholar] ; Crowley, 1959 Crowley, J. W. 1959. High production and reproductive failure. Vet. Sci. News, 13: 9–11. [Abs. in Progress in Cattle and Sheep Practice, Part 2. p. 301. Am. Vet. Publ., Illinois (1969)]. [Google Scholar] ; Boyd and Reed, 1961 Boyd, H. and Reed, H. C. B. 1961. Investigation into the incidence and causes of infertility in dairy cattle: Influence of kale feeding, milk production and management factors associated with “farming intensity”. Br. vet. J., 117: 192–200. [Google Scholar] ; King, 1968 King, J. O. L. 1968. The relationship between conception rate and changes in bodyweight, yield and SNF content of milk in dairy cows. Vet. Rec., 83: 492–494. [Google Scholar] ) have found no significant differences in fertility between high and low producing cows or between herds with different average productions. Currie (1956) Currie, Elizabeth J. 1956. The influence of milk yield on fertility in dairy cattle. J. Dairy Res., 23: 301–304. [Google Scholar] 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., 1941 Anon. N.Z. Dairy Board, 17th Annual Report 1941 60 61 [Google Scholar] ) 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 (1963) Dawson, F. L. M. 1963. Effect of high milk production on fertility. Refuah vet., 20: 235–242. [Abs. in Progress in Cattle and Sheep Practice, Part 2, p. 302, Am. Vet. Publ., Illinois (1969)]. [Google Scholar] 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, 1964 Dawson, F. L. M. 1964. Report to the Government of Israel on bovine infertility, FAO/ETAP Rep. No.1827 10–10. Rome FAO of United Nations. [Abs. in Vet. Bull., 35: 63 (1965)]. [Google Scholar] ).