Estrus synchronization (ES) in goats and sheep is achieved by control of the luteal phase of the estrous cycle, either by providing exogenous progesterone or by inducing premature luteolysis. The latter approach is not applicable during seasonal anestrus, whereas exogenous progesterone in combination with gonadotropin can be used to induce and synchronize estrus in anovular does and ewes. In the United States, ES in small ruminants is limited by the availability of appropriate pharmaceuticals, and there is a need for use of products designed and approved for the major livestock species (cattle and swine). The traditional product of choice for ES in goats and sheep is the intravaginal sponge impregnated with progestagen (e.g., flurogestone acetate or methyl acetoxyprogesterone) for 9 to 19 d followed by PMSG injected -48 to 0 h from sponge removal. Alternative choices of progesterone/progestagen have been controlled internal drug release (CIDR) devices, supplying natural progesterone, norgestomet implants, and orally active melengestrol acetate. Other products used alone or in conjunction with progestagens are PGF_2α or an analogue (cloprostenol), a combination of PMSG/hCG, and zeranol. This review summarizes some of the research efforts in the 1990s to establish optimal dose levels and timing of administration, particularly for extra-label use products, achieve tighter synchrony in support of timed insemination, and use the male effect and short-term nutritional manipulation in nonpharmacological approaches to induce ovulation and enhance ovulation rate. Copyright © 2000. American Society of Animal Science . © 2000 American Society of Animal Science

The effects of breed type (purebred or crossbred) and supplementation of agro-byproducts on the growth, carcass characteristics, and meat quality of landrace hair (Barbados Blackbelly; BB and St. Croix; SX) lambs was evaluated. Thirty-six 7.5-month-old purebred hair (BB and SX; body weight = 24.1 ± 4.26 kg) and terminal sire (Dorset; DO) crossbred lambs (DO × BB and DO × SX; body weight = 31.4 ± 3.50 kg) rotationally grazed predominantly on Jesup tall fescue pasture during spring with or without agro-byproduct supplementation (soyhull or corn gluten feed at 2% of BW). Following a 77d grazing period, the lambs were harvested, and their carcass characteristics and meat composition were evaluated. Both supplementation and crossbreeding significantly increased their carcass weight and primal cuts, whereas only supplementation increased (p < 0.01) the dressing percentage, and crossbreeding increased the shear force (p < 0.01). Regardless of breed type, supplementing agro-byproducts improved the lipid oxidation stability and texture properties of the fresh lamb, whereas the pasture-only lambs had healthier fatty acid profiles compared with the supplemented lambs. The results indicate that both terminal sire crossbreeding and byproduct supplementation can be used to affect the carcass characteristics and meat composition of landrace hair sheep lambs.

Consumer acceptance of pasture-raised hair sheep lamb was investigated. Food hub participants (n = 284) from Richmond, Virginia, were recruited to receive ground lamb and provide product quality ratings before and after product preparation. Over 96% of survey respondents specified that they would purchase local ground lamb if available, 35% indicated that they would purchase it at least once a month, and 43% indicated that they would pay a premium for it. Animal management pertaining to breed and supplementation had little effect on consumer ratings. The findings suggest that ground meat from hair sheep lambs could provide an opportunity to enhance profitability for small-scale producers in Virginia. Extension educators may be able to apply the findings in assisting sheep producers with lamb marketing.

Varicocele, a condition of abnormally dilated veins within the pampiniform plexus, is associated with reduced male fertility in several species but its frequency and impact in rams is not well documented. Semen was collected and pampiniform plexus ultrasound performed in early December during breeding soundness examinations (BSE) of mature Composite-IV rams over a three-year study. A portion of rams were evaluated in multiple years and data from a total of 129 collections on 90 rams were available for analyses. Semen parameters were estimated by computer-assisted sperm analysis (CASA). Imaging software was used to quantify the cross-sectional area of five vessels per testis and average areas of the left testis (AAL), right testis (AAR), and both testes (AAT) were calculated. The correlation between AAL and AAR measured on the same ram within a year was moderate and positive (0.51; P < 0.001). However, correlations between AAL, AAR, and AAT measured on the same ram in consecutive years were not different from zero. Average vessel area was analyzed with fixed effects of testis side (AAL or AAR), year (2020, 2021, or 2022), ram age (2, 3, or ≥ 4 yr-old) and a random effect of ram. Across years, AAL was 23 to 25% greater than AAR and 16 to 18% greater in ≥ 4-yr-old than younger rams (P < 0.01). Unilateral varicocele (UV) was diagnosed when AAL/AAR or AAR/AAL ratio exceeded 1.5 in a ram and, for rams sampled in multiple years, those diagnosed in one year were considered affected for all subsequent years. Within year, prevalence of UV ranged from 16 to 36%. Scrotal circumference (SC) and CASA parameters were analyzed with fixed effects of year, ram age, and UV status and a random effect of ram. Within 2- and 3-yr-olds, sperm from UV rams had lower motility than unaffected rams (42.1 ± 6.7% vs 62.2 ± 4.1% and 47.8 ± 7.4% vs 70.1 ± 4.7%, respectively; P ≤ 0.02) but no differences were observed within 4-yr-old rams. Across ages, sperm from UV rams had a lower percentage of normal than unaffected rams (91.5 ± 1.1% vs 94.3 ± 0.74%; P = 0.03). Sperm concentration, progressive motility, and SC were unaffected by UV status. Future studies will evaluate the effect UV status on siring capacity. Ultrasound methodologies previously refined to diagnose varicocele in boars helped identify sub-fertile rams that would not have been classified by routine BSE procedures. However, these methodologies would benefit from concurrent machine learning and software development to ensure imaging consistency across technicians and streamline procedures for real-time decision making. USDA is an equal opportunity provider and employer.

Compared to intact males, castrated lambs generally grow slower and have lighter and fatter carcasses. However, short-scrotum lambs can retain growth and carcass composition of intact males. This study evaluated carcass traits of castrated and short-scrotum Barbados Blackbelly (BB; n = 16) and St. Croix (STX; n = 15) hair sheep lambs. Ram lambs born in December (DEC; n = 10) and April (n = 21) were used in the study and were either rendered short scrotum (SS; n = 17) or castrated (CA; n = 14) using elastrator bands at weaning (63 d). All lambs transitioned in dry lot for 2 mo before return to pasture. Lambs co-grazed in a rotational system, were moved based on visual assessment of forage availability and provided Bermuda grass hay when forage was limiting. Lambs were provided soy hull at 3% BW to ensure diet continuity between forage environments. At target weights of 40 kg, SS and CA lambs were slaughtered and carcass data recorded. Carcass data were analyzed with reproductive status, breed and season born as main effects. DEC (230 d) and STX lambs (251 d) attained target weights earlier (P < 0.02) than APR (307 d) and BB (317 d) lambs. APR lambs had lower (P < 0.04) breast (0.9 kg) and loin cut weights (2.1 kg) than DEC lambs (1.1 and 2.4 kg, respectively). Carcass length was greater (P < 0.05) for SS (109 cm) than CA lambs (106 cm). There were also significant interactions (P < 0.05). APR-STX lambs had the lowest dressing% (42%) compared to APR-BB (48%), DEC-STX (47%) and DEC-BB (46%) lambs. DEC-STX (109 cm) and APR-BB (109 cm) carcasses were longer than DEC-BB (104 cm) and APR-STX (106 cm) lambs. DEC-SS lambs (84 cm) had the greatest leg circumference, while CA-STX (16 mm) lambs had the greatest body wall thickness in this study. Data suggest that reproductive status, breed and birth season all had varying influences on carcass traits of lambs in this study.