Animal genetics / Frederick B. Hutt.

  • Frederick Hutt
Date:
[1964]
Catalogue details

Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Animal genetics / Frederick B. Hutt. Source: Wellcome Collection.

    530/578 page 508
    508 ANIMAL GENETICS Readers of this book who are trained in orthodoxy might rehsh some of the dehghtful heresy to be found in the following headings of sections in Reid's report of his studies : Sanitation fails to reduce incidence Disinfection of udders, teats, and teat cups ineffective Bactericides useless in udder washes Cleaning and disinfecting stable floors of little avail Segregation of mastitic cows helps very little At the same time, Reid did not decry sanitation, and pointed out its importance in the production of milk of good quality. He also emphasized the fact that, as one might expect, susceptibility was aggravated by poor housing, lack of adequate bedding, exposure to inclement weather, and other adverse environmental conditions. Organisms causing mastitis are not likely to be eradicated, hence the disease must be considered as enzootic.^ Obviously some cows are genetically able to withstand it. It would seem sensible to mul¬ tiply that kind. This has not yet been done to any extent in prac¬ tice. Here is an opportunity for people who supervise the breeding of cattle, perhaps for some reader of this book. Further evidence of genetic resistance to mastitis has been reviewed elsewhere (Hütt, 1958). Resistance to Pullorum Disease in the Fowl The cycle by which pullorum disease is passed through the egg from one generation to the next was explained in Chapter 14. An obvious method of control is to break that cycle by eliminating from the breeding pens all hens that carry the causative organism. Sal¬ monella pullorum. Fortunately most of such birds are readily de¬ tected by an agglutination test, and, by routine tests of all breeding flocks and elimination of reactors therefrom, pullorum disease has been practically eliminated in some parts of the world. For animal geneticists, pullorum disease has some merits that entitle it to more than passing inteiest. For one thing, there are natural, inherent differences among breeds in susceptibility to it. Heavy breeds like Rhode Island Reds and Plymouth Rocks are three to five times as susceptible to it as are White Leghorns. This was demonstrated by the proportions of reactors in the two classes among flocks tested for the first time in programs aimed at-eradication of the disease from entire states or provinces. It was confirmed by ex¬ perimental inoculation of chicks. It has been shown, moreover, that 2 Let us leave epidemic and endemic for people, not cows.
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