Date of Award:

5-1960

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Animal, Dairy, and Veterinary Sciences

Department name when degree awarded

Dairy Husbandry

Committee Chair(s)

Lyman H. Rich

Committee

Lyman H. Rich

Committee

Eugene E. Starkey

Abstract

One of the largest problems facing the successful dairyman of today is selection of proper sires to mate to his high producing cows. Many breeders and dairymen have the impression that proven sires will give the same increase in production regardless of the dam's production or the level of environment present. Even though sires come from high producing herds, some as high as 600 pounds of butterfat, the average production of all cows in the state of Utah remains at a much lower figure. The average for all cows in Utah is about 250 pounds of butterfat and the average in 1958 of cows on Dairy Herd Improvement test was 403 pounds. This difference in level of production may be attributed to either genetic or environmental factors and possibly an interaction of the two. Most workers agree that the heritability estimates for milk production and fat yield are from .2 to .3. This means that about 25 per cent of the variance in milk yield is due to inheritance, and the other 75 per cent is due to management or environment. Therefore, there is a need to study daughters of the same sire at various levels of production to determine the amount of increase or decrease found at these levels.

This thesis presents a study of daughters of Holstein sires used in artificial breeding. Sires in artificial breeding were used because they have a larger number of daughters, and their daughters come from a wide range of production and management levels.

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