PSXIV-22 Selection for low fecal egg count estimated breeding value correlates with greater circulating antibody in sheep

Sheep selected for resistance to gastro-intestinal parasites have been shown to have greater survivability to weaning. Data from Katahdin sheep indicates that selection based on post-weaning fecal egg count estimated breeding values (PWFEC EBV) may further improve generalized immunity. However, no data exists to confirm this increased circulating antibody occurs in breeds genetically unrelated to Katahdins. In the fall of 2020 post-weaning blood and fecal samples were collected from Shropshire sheep (n = 42) and Polypay sheep (n = 91). The blood samples were analyzed for total immunoglobulin-G (IgG) using ELISA. Shropshire sheep were sorted into low (PWFEC EBV < 0) and high (PWFEC EBV > 0) groups based on fecal egg count (FEC), which were analyzed via a modified McMaster’s method. Polypay sheep were sorted into three groups by PWEC EBV; A (< -50) B (>-50 < +50) and C (>+50). In Shropshire group, individuals with low FEC had greater average IgG concentration (87.9 µg/mL) than those with high FEC (62.4 µg/mL) (P > 0.05). In the Polypay group, sheep in PWFEC EBV group A had numerically higher IgG concentration (86.2 µg/mL) than sheep in group B (71.2 µg/mL) and group C (53.1 µg/mL) (P > 0.05). While data in either breed were not significant, the trend observed across breeds indicate that sheep with a lower PWFEC EBV have numerically greater circulating antibody.

PSIX-18 Effect of chicory silage and se-yeast on peripartum ewes: Immune status via complete blood cell count

Immune status is critical for peripartum animals. Immune cells are highly affected by the oxidative status and level of Se. The use of forages with high content of antioxidants in combination with Se-yeast can improve the immune status in peripartum ruminants. The objective of this study was to test the possibility of improving the immune system of peripartum ewes by feeding a combination of chicory silage and Se-yeast. Approximately one month prior to lambing, 36 pregnant Polypay sheep were moved into single pens and randomly assigned to one of four groups to be fed either grass or chicory silage and supplemented or not with 3.6 mg Se/day (DiaMune, Diamond V). Blood was collected throughout the study to assess the complete blood count (VetScan HM5). Secondary compounds in silages were analyzed via LC-MS/MS. Data were analyzed using GLIMMIX (SAS) with day, silage type, Se and their interactions as fixed effects and ewe as random effect with significance declared at P≤0.05. Compared to grass silage, among measured secondary compounds only resveratrol was larger in chicory vs. grass. Total white blood cell count was larger in animals fed grass vs. chicory silage. Silage type and Se-yeast supplementation had little effects on the other measured parameters. The average hemoglobin inside red blood cells was larger in animals fed grass vs. chicory silage. Only tendencies (P between 0.08 and 0.09) were observed for the effects of Se supplementation, including increased hematocrit and number of circulating monocytes but, the latter, only in grass-fed ewes, and decreased red blood cell volume. Platelet size distribution tended (P=0.08) to increase in grass-fed ewes supplemented with Se but the opposite was observed in ewes fed chicory silage. Together, these data indicate a minimum-to-no effect of the type of silage or Se supplementation on complete blood cell count on peripartum ewes.

Adjustment of lamb birth and weaning weights for continuous effects of ewe age

Procedures for continuous adjustment of lamb birth and weaning weights for effects of ewe age were developed using 18 747 birth and 13 139 weaning weight records of Polypay sheep enrolled in the US National Sheep Improvement Program. Changes in birth and weaning weights across ewe age groups were modelled using hybrid curves that combined asymptotic regression models to describe initial increases in lamb weight as ewes moved into adulthood with secondorder polynomials to describe declines in lamb weights in older ewes. Lamb birth and weaning weights were highest (and the asymptotic and polynomial forms comprising the hybrid curves intersected) at ewe ages of 76 and 52 months, respectively. Across all ewe ages, hybrid curves were superior to second- and third-order polynomials in goodness of fit, producing a parabolic form with a flat top and different decay rates on either side of the ewe ages corresponding to maximum lamb weights. Fourth- and fifth-degree polynomials were equivalent to hybrid curves in goodness of fit, but generally did not produce reasonable predictions for the oldest ewes. Adjustment factors derived from the hybrid curve predicted that lamb birth weight would increase from 76% of maximum in 11-month-old ewes to 90 and 96% of maximum in 24- and 36-month-old ewes, respectively, and then decline to 97% of maximum at 105 months. For weaning weight, 83, 95, 99, and 93% of maximum lamb weight were attained at ewe ages of 11, 24, 36, and 105 months, respectively. Resulting multiplicative adjustment factors avoid discontinuities at boundaries between ewe age categories and are particularly useful in accelerated or other multiple-season lambing systems.

Characteristics of the American Polypay: A review

SummaryThe Polypay sheep breed was developed at the U.S. Sheep Experiment Station with a reproductive capacity markedly superior to that of domestic US western range breeds. The Polypay is a four breed composite of Targhee, Rambouillet, Dorset and Finnish Landrace breeds. It is a medium-sized wool sheep (average mature ewe weight of 72 kg) with a smooth body free of excessive skin wrinkles on the neck and body and a poll head. Comparative studies with other US domestic breeds have shown the Polypay to have earlier sexual maturity higher fertility and prolificacy rates. Mature ewes give birth to an average of 2.4 lambs and wean an average total litter weight of 63.8 kg per ewe at 120 days post partum. Lamb survival rates to 21 and 120 days are greater than those of other breeds compared. Average individual lamb weaning weight at 120 days (36.1 kg) exceeded that for Rambouillet and Targhee lambs (34.5 and 33.8 kg, respectively). Polypay carcasses are similar to those of Rambouillet and Targhee for dressing percentage, body wall thickness, kidney and pelvic fat, and ribeye area. Measures of carcass fat are less in the Polypay when compared to the Rambouillet and Targhee while qualitative leg scores for the Polypay were more favorable. Productive longevity under western range herded conditions does not differ among Polypay, Rambouillet, Targhee and Columbia sheep. In a farm flock production system, the average number of productive years for Polypay ewes exceeded that of most crossbred types. Wool characteristics are defined as a coarse to medium grade wool with a fiber diameter ranging from 24 to 33 μm. Fiber staple length ranges from 7.6 to 12.7 cm with a common mean of approximately 10 cm. Raw fleece weights are considered light and range from 2.7 to 4.5 kg. Yield of clean wool is approximately 57 percent. Economic evaluations favored the Polypay in all production systems considered with 15 to 36 percent increase in sales or profits compared to other US domestic breeds. When considering the Polypay breed for importation, some prudence should be exercised because it may not be suitable to all environments and production systems in the world, especially where nutritional and management resources are not sufficient to support lactating ewes rearing twins.