Hostname: page-component-78c5997874-mlc7c Total loading time: 0 Render date: 2024-11-02T19:26:22.708Z Has data issue: false hasContentIssue false
  • English
  • Français

614. Variations in the chemical composition of milk with particular reference to the solids-not-fat: II. The effect of heredity

Published online by Cambridge University Press:  01 June 2009

Alan Robertson ,
R. Waite  and
J. C. D. White
Alan Robertson
Affiliation:
Institute of Animal Genetics, Edinburgh
R. Waite
Affiliation:
The Hannah Dairy Research Institute, Kirkhill, Ayr
J. C. D. White
Affiliation:
The Hannah Dairy Research Institute, Kirkhill, Ayr
Get access Rights & Permissions [Opens in a new window]

Extract

1. A statistical analysis has been made of lactation records from 500 dam-daughter pairs of the Ayrshire breed. Measurements were taken of milk yield, fat, S.N.F., crude protein, casein and lactose.

2. A correction was made for the age of the cow. This contributed a substantial fraction of the total variation for milk yield, S.N.F. and lactose contents. Month of calving had a trivial effect on the lactation average for the characters when compared with the individual variation between cows.

3. After correction for age, the variation between lactations was highest for fat content (standard deviation 0·35%) and slightly less for S.N.F. (0·26%).

4. The heritability was estimated by the dam-daughter correlation within herds. Values in the neighbourhood of 0·5 were obtained for S.N.F., crude protein, casein and ‘ash’ (determined by difference), about 0·35 for fat and lactose, 0·25 for milk yield and 0·13 for non-casein nitrogen.

5. The phenotypic correlations between yield and lactose were positive for both dam and daughter groups. The correlations between yield and the other constituents were more negative in the daughter group than in the dam group. The correlation between yield and S.N.F. was, in fact, positive in the latter. The correlation between fat and S.N.F. averaged 0·36, being derived mainly from the correlation between fat and casein (0·43), though that with lactose was also positive (0·13).

6. The variation in S.N.F. was mostly determined by that in casein (r=0·85). There was a positive correlation between lactose and casein (0·24), and a negative one between lactose and non-casein nitrogen (–0·41). Lactose was negatively correlated with ‘ash’ (–0·31). ‘Ash’ was positively correlated with non-casein nitrogen (0·23)

7. There were positive and significant genetic correlations between casein and both fat and lactose, and that between the last two was almost significant.

8. No significant genetic correlations were found between yield and the chemical constituents, although figures of practical importance may exist which did not reach significance in an experiment of this size.

9. The practical significance of these results is discussed. It is concluded that selection for yield alone is not likely to cause any great decline in S.N.F. content of the milk, and that this could probably be held in check by paying some attention to the fat content of the milk.

Type
Original Articles
Information
Journal of Dairy Research , Volume 23 , Issue 1 , February 1956 , pp. 82 - 91
Copyright
Copyright © Proprietors of Journal of Dairy Research 1956

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

(1)Hansson, A. & Bonnier, G. (1949). Acta agric. suec. 3, 179.Google Scholar
(2)Hansson, A., Skjervold, H. & Carli, B. (1950). Acta agric. Scand. 1, 112.CrossRefGoogle Scholar
(3)Hancock, J. (1953). N.Z. J. Sci. Tech. 35, 67.Google Scholar
(4)British Oil and Cake Mills Ltd.. (1954). 1st Bull Progeny Test, Final Rep. 34 pp. (Lond.)Google Scholar
(5)National Milk Records (1947). Annual Rep. p. 55.Google Scholar
(6)Mahadevan, P. (1951). J. agric. Sci. 41, 80, 94.CrossRefGoogle Scholar
(7)Danish, Research Laboratory (1952). 257th Rep. Afkomsprøver med Tyre, 6.Google Scholar
(8)Provan, A. L. Private communication.Google Scholar
(9)Milk Marketing Board. (1952). Prod. Div. Rep. no. 3.Google Scholar
(10)Lonka, T. (1947). Maataloust. Aikakausk. 19, 8.Google Scholar
(11)Tocher, J. F. (1925). Variations in the Composition of Milk. Edinburgh: H.M.S.O.Google Scholar
(12)Hazel, L. N. (1943). Genetics, 28, 476.CrossRefGoogle Scholar
(13)Rendel, J. M. & Robertson, A. (1950). J. Genet. 50, 1.CrossRefGoogle Scholar