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The influence of contemporaneity, genetic variation and herd differences on variation in milk yield and butterfat percentage

  • J. H. Watson (a1)

Extract

1. Paired lactation records of milk yield and fat percentage from experimental twins and commercial twins, full-sisters and half-sisters are used in a study of the influence of contemporaneity, genetic variation and herd differences.

2. The design of the investigation was such that members of a pair were alike in:

(i) both time of calving and lactation number,

(ii) time of calving only,

(iii) lactation number only, or

(iv) neither time of calving nor lactation number.

3. Intra-class correlations between pair members in respect both of yield and fat percentage were highest for contemporary records. Differences in time of calving and in lactation number produced, in aggregate, a decline in correlation of about 20%. However, the separate estimates varied considerably between the different types of pair.

4. The within-pair and between-pair variance components independently confirm these effects of contemporaneity. As the degree of contemporaneity of pair members declines the within-pair variance increases in size and the between-pair component decreases.

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References

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Donald, H. P., 1958. Evidence from twins on variation in growth and production of cattle. Proc. Xth. int. Congr. Genet. (Montreal), 1958, 1: 225.
Johansson, I., 1958. The genetics of milk yield. Proc. Xth int. Cong. Genet. (Montreal), 1958, 1: 236.
Johansson, I., & Hansson, A., 1940. Causes of variation in milk and butterfat yield of dairy cows. K. Lantbr. Akad. Tidskr., 6½, 127 pp.
Kempthorne, O., 1955. The theoretical values of correlations between relatives in random mating populations. Genetics, 40: 153.
KingJ., W. B. J., W. B., & Donald, H. P., 1955. A study of variation in twin cattle. III. Growth. J. Dairy Res., 22: 1.
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Robertson, A., & Rendel, J. M., 1954. The performance of heifers got by artificial insemination. J. agric. Sci., 44: 184.
Watson, J. H., 1960. Milk yield and butterfat percentage of twin and single-born cattle under experimental and field conditions. Anim. Prod., 2: 67.

The influence of contemporaneity, genetic variation and herd differences on variation in milk yield and butterfat percentage

  • J. H. Watson (a1)

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