Coopworth sheep, a newly available genotype, were compared with
other genotypes in two trials to assess cumulative lamb and wool
production and contributing components related to survival, reproduction
and growth, and for the effects of ewe body weight on reproductive traits.
In a third trial, various genotypes generated in the process of upgrading
native Kaghani sheep, were evaluated for lamb and wool production. In the
first two trials six ewe genotypes, generated by mating Coopworth (C),
Polypay (P) and Suffolk (S) rams to Polypay and Coopworth-type ewes, were
exposed to Hampshire rams for spring lambing from 1986 through 1990.
Overall conception rate averaged 96% and ranged from 93% for S X C ewes to
97% for P X C ewes. Sire breeds were not different in ovulation rate but
daughters of Polypay dams averaged .18 higher ovulation rate than
daughters of Coopworth dams (P<.05). Uterine efficiency for twin
ovulators was .86 with little variation among sire breeds; however,
daughters of Polypay ewes had a mean uterine efficiency of .93 compared to
.78 for daughters of Coopworth ewes (P<.05). Mean litter size at birth
averaged 1.63 and ranged from 1.45 for C ewes to 1.75 for S X P ewes.
Ewes from Polypay dams had higher mean litter size (P<.01) than those from
Coopworth dams (1.73 vs 1.54), but differences between sire breeds were
not significant. Ewes from Suffolk sires weaned the heaviest lambs while
ewes from Polypay sires weaned the greatest number of lambs, resulting in
similar weight of lamb weaned per ewe mated. Adjustment of lamb
production for ewe metabolic body size resulted in Coopworth-sired ewes
being more efficient than the heavier Suffolk-sired ewes. Coopworth-sired
ewes produced 32% more wool than ewes sired by the other two breeds.
Combining lamb and wool production in an index resulted in a range of less
than 2% among sire breeds for gross productivity per ewe mated.
Productivity of Rambouillet ewes studied under Pakistani conditions
declined significantly over time. Crossbred lambs were generally heavier
at weaning than Rambouillets, while wool production was highest in
purebred Rambouillet ewes followed by genotypes related closely to
Rambouillets. In all trials crossbreds generally excelled purebreds in
overall productivity; the degree of superiority depended on genotypes
involved in the crosses. / Graduation date: 1991
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/37512 |
| Date | 13 December 1990 |
| Creators | Nawaz, Mohammad, 1957- |
| Contributors | Meyer, Howard H. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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