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Selection on ram 18-month weight to improve lamb growth rate

  • D. Croston (a1), J. L. Read (a1), D. W. Jones (a1), D. E. Steane (a1) and C. Smith (a2)...

Abstract

Thirteen pairs of Suffolk rams were selected on high and low 18-month adjusted live weight from six farms over 2 years, to establish the relationship between 18-month weight and early lamb growth. Progeny were first produced in recorded crossbred flocks (618 lambs) and then in an experimental flock of crossbred ewes (1083 lambs). Different results were obtained from the recorded and experimental flocks. The regressions of lamb 12- to 13-week weight on ram 18-month weight (within farm deviation) were 0·053 ± 0·022 kg and –0·004 ± 0·020 kg, respectively. These regressions for indirect selection correspond to ‘effective’ heritabilities for direct selection for lamb growth of 0·18 ± 0·07 and 0·02 ± 0·06 respectively. Improvement of early Iamb growth is discussed and it is concluded that selection for 18-month weight is unlikely to be a useful method.

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References

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Bowman, J. C. and Broadbent, J. S. 1966. Genetic parameters of growth between birth and sixteen weeks in Down cross sheep. Anim. Prod. 8: 129135.
Fitzhugh, H. A. JR, Taylor, St C. S. 1971. Genetic analysis of degree of maturity. J. Anim. Sci. 33: 717725.
Martin, T. G., Sales, D. I., Smith, C. and Nicholson, D. 1980. Phenotypic and genetic parameters for lamb weights in a synthetic line of sheep. Anim. Prod. 30: 261269.
Owen, J. B., Brook, L. E., Read, J. L., Steane, D. E. and Hill, W. G. 1978. An evaluation of performance-testing of rams using artificial rearing. Anim. Prod. 27: 247259.

Selection on ram 18-month weight to improve lamb growth rate

  • D. Croston (a1), J. L. Read (a1), D. W. Jones (a1), D. E. Steane (a1) and C. Smith (a2)...

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