Growth and carcass characteristics of lambs sired by Dorper and Dorset rams.
- 1 May 2004
- journal article
- research article
- Published by Oxford University Press (OUP) in Journal of Animal Science
- Vol. 82 (5), 1323-1328
- https://doi.org/10.2527/2004.8251323x
Abstract
Growth and carcass merit of Dorset- (DO) and Dorper-sired (DP) lambs were compared over 3 yr in matings with 50% Dorset, 25% Rambouillet, 25% Finnsheep ewes. The DP were slightly lighter (P = 0.09) at birth than the DO lambs. In the first year of the study, DP lambs produced by AI using imported South African sires were heavier than DO lambs when weaned at 60 d of age (21.7 vs. 19.5 kg; P = 0.05). In yr 2 and 3, however, offspring of natural-service Dorper sires produced in the U.S. did not differ in weaning weight from DO lambs (16.9 vs. 17.8 kg; P = 0.02 for breed × year interaction). Lamb survival was also affected by breed × year interaction (P = 0.04). In 2000 and 2001, with 12 to 16% triplet or larger litters, mortality was higher for DP lambs (14.9 vs. 7.7%; P = 0.12). However, in 2002, with approximately 33% triplet or larger litters and with higher mortality levels in all birth types, DP lambs had fewer death losses than did DO lambs (23.2 vs. 36.1%; P = 0.11). No differences between DO and DP lambs were observed in postweaning gain during summer grazing or in drylot in autumn. At chilled carcass weights of approximately 25 kg, DP lambs were somewhat fatter than DO lambs, with greater body wall thickness (P < 0.01; 22 vs. 19 mm) and slightly greater backfat thickness (P = 0.15; 6.4 vs. 5.5 mm) and yield grades (P = 0.15; 2.9 vs. 2.6). The DP lambs also had more desirable leg scores (P = 0.01; 11.6 vs. 10.9) and slightly larger LM area (P = 0.13; 14.1 vs. 13.5 mm2) than did DO lambs, confirming acceptable muscling and conformation in carcasses from Dorper-sired lambs. However, differences were not observed in the percentage of carcass weight in the leg or loin, or in the lean:bone ratio in the dissected leg. Ultrasonic measurements of backfat thickness and LM area taken in live lambs before slaughter were positively associated with direct measures on chilled carcasses with correlations of 0.77 for backfat thickness and 0.51 for LM area.Keywords
This publication has 16 references indexed in Scilit:
- The development of the Dorper, its nutrition and a perspective of the grazing ruminant on veldSmall Ruminant Research, 2000
- The history of the Dorper sheepSmall Ruminant Research, 2000
- Productive performance of Dorper sheepSmall Ruminant Research, 2000
- A comparative assessment of Dorper sheep in different production environments and systemsSmall Ruminant Research, 2000
- The effect of nutrition in mid pregnancy and ewe liveweight change on birth weight and management for lamb survival in highly fecund ewesAustralian Journal of Experimental Agriculture, 1992
- Factors influencing lamb survival in a high fecundity Booroola Merino × South Australian Merino flockTheriogenology, 1990
- Behaviour at parturition and lamb survival of Booroola Merino sheepLivestock Production Science, 1985
- Influence of birth weight and litter size on lamb survival in high fecundity Booroola-Merino crossbred flocksNew Zealand Journal of Agricultural Research, 1985
- Productivity of Purebred and Crossbred Finnsheep. I. Reproductive Traits of Ewes and Lamb SurvivalJournal of Animal Science, 1981
- Performance of Finnish Landrace Crossbred Ewes under Accelerated Lambing. II. Lamb Growth and SurvivalJournal of Animal Science, 1980