TRANSFERRIN GENOTYPES AND THEIR RELATIONSHIP WITH BLOOD CONSTITUENTS, FERTILITY AND COW PRODUCTIVITY 1

ERUM transferrins serve as the body's major iron transport mechanism in the blood. The genetic system as reported by Ash- ton (1958) is three segregating alleles, Tf A, Tf D and Tf E, operating on an incomplete dominance basis at one locus. The three al- leles make possible six genotypes: AA, DD, EE, AD, AE and DE. Transferrins were shown to be under genetic control by Ashton (1958) and genotypic differences may influence or be related to milk production (Ashton, 1960) and fertility (Hickman and Dunn, 1961) in cattle. If these differences are caused by or related to diverse transferrin genotypes, then determination of the latter in cattle could serve as a useful aid in selection programs. The purpose of this study was to determine if: (1) transferrin genotypes are related to or influence plasma levels of several blood con- stituents, (2) transferrin differences can ac- count for any part of feedlot performance differences in cattle, (3) transferrins influence maintenance requirements, (4) there are fer- tility differences in cattle related to transfer- tin genotypes, and (5) the transferrin geno- type of the dam influences the weaning weight of her calf.