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Growth Patterns of Range-Grazed Rambouillet Lambs¹

South Dakota State University, Brookings 57006

Abstract

Data from 4,566 lambs taken over a period of 11 years were used to study growth patterns of suckling lambs grazing on the range with their dams. Growth curves are presented for male singles, male twins, female singles, and female twins up to 170 days of age. Lambs made rapid growth for the first 70 to 80 days, then gained at a decreasing rate. Only in years 1960 and 1961 did growth curves plateau or decline after lambs reached 130 to 140 days of age. Birth weight, weaning weight, and rate of gain from birth to weaning were influenced (P<.01) by year, sex and type of rearing (type of birth for birth weight). Male singles were heavier at birth (4.92 kg vs 4.66 kg) and weaning (35.8 kg vs 34.8 kg) and gained faster (194 g/day vs 188 g/day) than female singles. Female singles were heavier at birth and weaning and gained more rapidly than male twins. Female twins were lighter at birth (3.76 kg vs 4.00 kg) and weaning (30.4 kg vs 31.0 kg) and had a slower rate of gain (162 g/day vs 166 g/day) than male twins. The quadratic effect of birth weight was significant for rate of gain from birth to weaning. Birth weight accounted for 20% of the variability in rate of gain.

¹ Published with the approval of the Director of the South Dakota Agricultural Experiment Station as Publication No. 1462 of the Jorunal Series.

² Department of Animal Science