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Variations in Type Ratings of Individual Ayrshire Cows

1948; Elsevier BV; Volume: 31; Issue: 1 Linguagem: Inglês

10.3168/jds.s0022-0302(48)92176-6

1529-9066

George Hyatt, William J. Tyler,

Animal Behavior and Welfare Studies

Type classification programs have been adopted by all the major dairy cattle breed associations.With the exception of the Guernsey breed, in order to participate in this program each breeder must submit all of the registered cows in his herd for classification.At a subsequent reclassification of the herd new ratings on previously classified cows will be official only if the new rating is higher than the previous official rating.Before,a definite appraisal of the type classification program can be made, it is desirable to know as much as possible about the amount of variation that occurs when the same cows are classified several times throughout a lifetime.This investigation sought to determine: (a) The degree or amount of variation that occurs when the same cows are classified several times in their lifetime, (b) the degree of agreement between ratings given the same cow by the same inspector and by different inspectors at different times, (c) the possibility that age of animal, stage of lactation, and condition of animal influence the official type rating, (d) the value of photographic records in studying the type of animals from birth to maturity, and (e) the reasons why the ratings of some cows undergo large changes. EXPERIMENTAL PROCEDUREThe data for this investigation were collected from the Ayrshire herd (known as the Reymann Memorial Herd) at the West Virginia Agricultural Experiment Station.This herd represents approximately 25 years of a continuous, carefully controlled breeding project.No females have been brought into the herd in that period of time, and each normal female that is dropped in the herd must be raised and retained through at least one 305-day lactation before her disposal.The feeding and management of the herd has been kept as nearly constant as possible over the 25-year period.Each animal is bred to freshen each year, allowing 6 to 8 weeks for the dry period.From 1942 through 1946 all the females that had calved were rated for type approximately three times yearly.During this period 138 cows were rated.Of this number, 32 were rated once, 26 twice, 17 three times, 8 four times, 6 five times, 9 six times, 12 seven times, 9 eight times, 5 nine times, 4 ten times, 2 eleven times, 3 twelve times, and 5 thirteen times.In