HEIFER GROWTH IN SEVERAL STRAINS OF HOLSTEINS AND AYRSHIRES AND IN PROGENY OF AYRSHIRE COWS MATED TO BROW SWISS AND NORWEGIAN RED BULLS

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Abstract
Body weights and measurements were compared among several genetic groups from the 496 Holstein-based H line heifers and 344 Ayrshire-based A line heifers. Differences among herds (Charlottetown, P.E.I., Lennoxville and Normandin, Que.; Ottawa, Ont., and Lethbridge, Alta) were large and highly significant (P < 0.01) for age at first calving and all weights and measurements except birth weight. Year and season of birth effects were small and generally not significant (P > 0.05). Birth weights were 4.1 kg lighter for calves from first parity dams and 1.4 kg lighter for second parity dams than fourth or later parity dams. Heifers calving at earlier ages for the first time were generally heavier and larger at 66 and 82 wk than those calving later, reflecting the effects of concurrent pregnancy. H line heifers were significantly heavier and larger in all measurements than A line heifers. Differences among the Canadian, American, and Research Branch Holstein sire groups were small and generally not significant (P > 0.05). Brown Swiss progeny were significantly (P < 0.05) taller at the withers and longer in the rump and generally larger than progeny of other A line sire groups. Norwegian Red progeny were the most similar to the Brown Swiss, followed by the other Ayrshire groups. Key words: Growth, heifers, Holsteins, Ayrshires, Brown Swiss, Norwegian Red

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