Production Differences between Registered Cows and Their Nonregistered Herd-mates.

Within-herd contemporary comparisons of the first-lactation production of registered and nonregistered cows in herds enrolled in the New York Dail T Herd Improvement Associations suggest only small genetic differences between registered and nonregistered cows. In general, the registered Holsteins exceeded in production their nonregistered herd-mates, whereas the nonregistered cows had a slight advantage over their registered herd-mates for the Ayrshire, Guernsey, and Jersey breeds. Artificially sired cows had consistently higher production than their naturally sired herd-mates for all breeds. A definite increase in this advantage was noted for Holsteins in more recent years. No trend was apparent in the comparison of artificially sired registered and nonregistered cows for any of the breeds. The problem of comparing the production of registered and nonregistered cows has not received much attention. Qureshi (1) has reported that the genetic progress of progeny of grade sires was more rapid than the progress of progeny of registered sires for Holstein and Jersey data in Texas. The registered groups, however, had over-all higher genetic merit and average production than the grade groups. This study was to ascertain the current status of improvement for production of milk and fat of nonregistered cows. Comparisons were made between the first-lactation performance of registered and nonregistered cows within the same herd and year-season of freshening. The influence of artificial insemination (A.I.) was estimated by making further comparisons for these groups of cows : natural service INS) registered vs. NS nonregistered, A.I. registered vs. A.I. nonregistered, all A.I. vs. all NS, and NS registered vs. A.I. registered. These comparisons were made for five breeds (Ayrshire, Guernsey, Holstein, Jersey, and Brown Swiss) in herds on the New York DHIA program. M E T H O D S AND DATA The contemporary comparison procedure described by Robertson and Rendel (2) in Great Britain and later by Tucker et al. (3) in the United States was used to estimate the genetic difference between any two classes of cows. The comparisons were within herd and year of freshening. Only one season of freshening was considered per year (August through March). Records of cows freshening in other months were ignored. A comparison of registered vs. nonregistered cows for a particular herd-year l~eceived for publication February 19, 1965. was of the form (am) I n + m ) -I ( x y ) where x was the average of registered cows, y the average of nonregistered cows, n the number of registered cows, and m the number of nonregistered cows. For each year, comparisons were made for all herds having at least one animal in each of the pair of classes being compared. These comparisons were summed over all herds in that year and divided by the sum of the weights over all herds. All cows in the comparisons were less than 35 months of age at first freshening. First-lactation records (305-day, 2 ×, mature equivalent) were chosen to minimize effects of selection. All records were from the files of the New York Dairy Records Processing Laboratory. To be classified as registered, the cow and both her dam and sire had to be coded as registered. This procedure was to reduce errors due to miseoding in the DHIA files. Those classified as nonregistered were coded as nonregistered, but both parents had to be classified as the same breed as the cow. Many cows were excluded because either sire or dam information was missing; this was to eliminate any bias due to including crossbred cows in the nonregistered groups.