Performance of Finnish Landrace Crossbred Ewes under Accelerated Lambing. II. Lamb Growth and Survival

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Abstract
The performance of 1,361 Suffolk-sired lambs out of ½-Finnish Landrace, ½-Rambouillet (½-Finn) ewes; ¼-Finnish Landrace, ¾-Rambouillet (¼-Finn) ewes, and ½-Suffolk, ½-Rambouillet (SR) ewes was compared over a 5-year period. Lambs were born in January, April and September, and litters were reduced to two lambs at birth, with some selection against smaller, weaker lambs. Lambs were weaned at 43 ± 10 days of age and slaughtered at 44 ± 5 kilograms. Lambs from ½-Finn ewes averaged 3.57 kg at birth, which was .75 kg less than lambs from ¼-Finn ewes (P<.001) and .83 kg less than lambs from SR ewes (P<.001). These differences were reduced to .44 kg (P<.001) and .50 kg (P<.01), respectively, when the data were adjusted for litter size. Mean perinatal mortality for all groups was 6%. Perinatal mortality was 8.5% higher (P<.01) among progeny of SR ewes than progeny of ½-Finn ewes, and 3.4% higher (P<.01) among progeny of ½-Finn ewes than among progeny of ¼-Finn ewes (P<.01). When the data were adjusted for litter size, progeny of SR ewes had 14.7% higher (P<.001) perinatal mortality than progeny of ½-Finn ewes and 15.2% higher (P<.001) perinatal mortality than progeny of ¼-Finn ewes. The relationship between birth weight and mortality was quadratic (P<.001); mortality was minimized at birth weights of 5.2 kg for both sexes. Lambs from SR and ¼-Finn ewes grew faster than lambs from ½-Finn ewes both preweaning (303 and 298 vs 279 g/day; P<.005) and postweaning (253 and 241 vs 232 g/day; P<.05) and were heavier at 45 days (18.2 and 17.9 vs 16.4 kg; P<.001) and 150 days (45.3 and 43.3 vs 40.9 kg; P<.005). Lambs from SR and ¼-Finn ewes did not differ significantly in preweaning or postweaning daily gain. Progeny live animal quality grades did not differ between ewe breed groups. Copyright © 1980. American Society of Animal Science . Copyright 1980 by American Society of Animal Science