<p> There have been many changes in the United States sheep industry over the years. Decreasing profitability of wool production has shifted the focus of many producers to strictly meat production. In south Texas, extreme high summer temperatures add an additional challenge in raising wool breeds of sheep. Hair sheep are gaining popularity in lamb-only production systems as they are more adapted to hot climates and eliminate shearing costs. The Dorper is the most popular breed of hair sheep throughout Texas due to superior lamb carcasses. Maximizing reproductive efficiency is critical for increasing the profitability of sheep production. Accelerated lambing systems can produce 3 lamb crops every two years versus 1 lamb crop per year. For this to be accomplished, ewes must be capable of breeding early post-partum and at all times of the year. We determined the reproductive characteristics of Dorper ewes. In the absence of a ram, Dorper ewes were anestrous from March until May. We observed considerable variation of ewes when both entering and ending anestrous. During the initial breeding season, 7-d CIDR<sup>® </sup> treated ewes, which conceived 1<sup>st</sup> service, had a significantly lower mean day of birthing (3.2 ± 2.1 d) compared to (10.1 ± 1.9 d) control ewes, resulting in a shorter lambing duration. During the seasonal anestrous period both CIDR<sup>®</sup> treated and control post-partum Dorper ewes were stimulated to ovulate while in the presence of the ram. However, during this time, 9-d CIDR<sup>®</sup> treatment significantly shortened both overall ram to lambing interval (152.8 ± 3.2d vs.165.7 ± 3.0 d) and first service ram to lambing interval (149.3 ± 1.3 d vs. 160.7 ± 1.5 d). Fall-born Dorper ewes with known birth dates had a mean age of puberty of 306.5 ± 4.9 d. Fall-born yearlings and spring-born ewe lambs were exposed to a ram during the first fall breeding season following their birth. While no difference was found in overall conception rate, fall-born yearlings had a significantly greater first service conception rate (83.3 %) compared to spring-born lambs (28.6 %). The findings of this study illustrate that Dorper ewes have the potential to be utilized in accelerated lambing systems in south Texas. By achieving a high conception rate post-partum simultaneous to the anestrous season, we were able to maintain an 8 mo lambing interval during the first two breeding season. We conclude that the reproductive attributes of the Dorper ewe makes them an excellent choice for sheep producers throughout South Texas.</p>
| Identifer | oai:union.ndltd.org:PROQUEST/oai:pqdtoai.proquest.com:1590222 |
| Date | 23 August 2015 |
| Creators | Taylor, Eric Clayton |
| Publisher | Texas A&M University - Kingsville |
| Source Sets | ProQuest.com |
| Language | English |
| Detected Language | English |
| Type | thesis |
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