Sheep & Goat Research Journal. Volume 24, 2009

Contents

Wool Price Differences by Preparation in the United States
Author: D.P. Anderson, O. Capps, Jr., E.E. Davis and S.D. Teichelman
Evaluating Nutritional Status of Dorper and Rembouillet Ewes in Range Sheep Production
Author: T.R. Whitney, D.F. Waldron and T.D. Willingham
Effect of Expected Peripheral Concentrations of Progesterone on Ovulation Rate and Litter Size in Barbados Blackbelly Ewes
Author: E. H. Devonish, M. Knights and E. K. Inskeep
Post-weaning Management of Lambs Alters Subsequent Feedlot Performance and Tissue Deposition
Author: R. R. Redden, R. W. Kott, L.M.M. Surber, J. A. Boles, A. W. Layton and P. G. Hatfield
Substituting distillers dried grains for cottonseed meal in lamb-finishing diets: growth, wool characteristics, and serum NEFA, urea N, and IGF-1 concentrations
Author: J. K. McEachern, T. R. Whitney, C. B. Scott, C. J. Lupton, and M. W. Salisbury

Article Summaries

Wool Price Differences by Preparation in the United States

Author: D.P. Anderson, O. Capps, Jr., E.E. Davis and S.D. Teichelman
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Summary

Price differences for U.S. wools by preparation and type were examined using data collected from warehouses and pool sales across the United States over the period 1993 to 2002. The goal was to determine premium/discounts in wool prices by preparation and type, controlling for season, year, region, average-fiber diameter, and lot size. Unlike previous research efforts, a hedonic model was used in this investigation.

The hedonic price model explained about 83 percent of the variation in U.S. wool prices. Seasonality in U.S. clean wool prices was evident. Wool prices received by producers from January to March as well as from October to December were significantly lower from 5.9 percent to 17.4 percent than those prices in September. Wool prices in June were roughly 8 percent higher than those of September. In accord with prior expectations, U.S. clean wool prices were highest in 1995 and 1997. Prices in remaining years from 1993 to 2002 were significantly lower from 11.8 percent to 52.2 percent relative to the base year of 1997. Further, U.S. clean wool prices were discounted by 7.9 percent and 9.8 percent respectively, in the Eastern and Western regions of the United States relative to the Central region.

In line with prior research, prices of table-skirted and classed wool were significantly higher than original bag wool by slightly more than 8 percent. Significant differences among wool types also were evident. In particular, U.S. clean prices of TSC and BOU Main Line Wool were higher by 23.5 percent over the OB wool breed. Significant differences were noted as well among wool types from OB. Among wool types, the premiums/discounts relative to OB wool breed type were quite large in magnitude.

U.S. clean wool prices were sensitive to change in average diameter. The elasticity of clean price with respect to average fiber diameter was estimated to be roughly -1.42. Lot size, as measured by grease weight, also positively affected U.S. clean prices. The elasticity of clean price with respect to lot size was estimated as 0.16.

Key Words : U.S. Wool Prices, Hedonic Price Model

Evaluating Nutritional Status of Dorper and Rembouillet Ewes in Range Sheep Production

Author: T.R. Whitney, D.F. Waldron and T.D. Willingham

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Summary

Mature Dorper and Rambouillet ewes were maintained together for 2 years in a range environment to evaluate their nutritional status before and during gestation. During Years 1 and 2, nutritional status of mature Dorper (n = 46 and 71, respectively) and Rambouillet (n = 33 and 81, respectively) ewes were evaluated during pre- (August), mid- (late October) and late gestation (December). Ewes were selected from multiple Dorper (n = 20) and Rambouillet (n = 13) flocks. All ewes performed well while grazing and did not lose weight or BCS during gestation, except in Year 1 during late gestation when Dorper and Rambouillet ewes both lost weight. Compared to Rambouillet ewes, Dorper ewes had higher BCS (P < 0.03) during pre-gestation in Year 1 and throughout Year 2 (P < 0.01), but similar BW (P > 0.10) during both years. Dorper ewes tended to have greater IGF-1 concentrations (P < 0.08) during Year 1 in pre-gestation, and maintained greater IGF-1 concentrations (P < 0.005) than Rambouillet ewes throughout Year 2. Dorper ewes had less serum NEFA and serum urea nitrogen (P < 0.05) than Rambouillet ewes during mid- and late gestation in Year 2. Results suggest that nutritional status differed at times, between Dorper and Rambouillet ewes in a range production system during gestation. Reasons for Dorper ewes having higher BCS and serum IGF-1 concentrations throughout gestation need to be investigated further.

Key Words : Dorper, Rambouillet, Insulin-like Growth Factor-1, Metabolites, Rangelands, Sheep

Effect of Expected Peripheral Concentrations of Progesterone on Ovulation Rate and Litter Size in Barbados Blackbelly Ewes

Author: E. H. Devonish, M. Knights and E. K. Inskeep

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Summary

To determine whether luteal phase concentrations of progesterone (P4) altered ovulation rate and litter size in ewes, mature Barbados Blackbelly ewes were assigned to groups treated so that they would be expected to have low, medium or high P4 (n = 23 or 33 per group in two seasons). Each ewe on low and high P4 received a P4-containing intravaginal insert from d 4 through d 14 after estrus. Ewes in low group were given PGF2á on d 6 to regress corpora lutea (CL). Ewes with medium P4 were untreated. Ovaries in 10 or 8 ewes per group (in seasons 1 and 2, respectively) were observed by transrectal ultrasonography from d 6 of the pre-breeding cycle until ovulation, and in all ewes on d 7 after breeding (one ram to 10 to 16 ewes). Numbers of follicles that disappeared at estrus (P < 0.02) and of CL formed (P < 0.001) increased linearly with decreasing P4. As P4 decreased, more follicles disappeared from the penultimate than the final wave of development. Disappearance of follicles was correlated with CL formed (0.53; P < 0.0001). Conception rates did not differ with expected concentration of P4. Lambs born per CL decreased linearly (P < 0.001) with decreasing concentrations of P4. Prolificacy did not differ (P > 0.32) among ewes treated to have low, medium or high concentrations of P4 (2.0, 1.9, and 1.9 ± 0.1 lambs, respectively), despite greater ovulation rates. On a practical basis, altering progesterone before breeding did not change productivity of the ewe in terms of number of lambs born.

Key Words : Barbados Blackbelly, Ovulation Rate, Progesterone, Prolificacy, Ewe, Sheep

Post-weaning Management of Lambs Alters Subsequent Feedlot Performance and Tissue Deposition

Author: R. R. Redden, R. W. Kott, L.M.M. Surber, J. A. Boles, A. W. Layton and P. G. Hatfield

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Summary

Backgrounding lambs on forage-based diets after weaning may provide producers with alternatives to traditional marketing of lambs directly to feedlots. Our objective was to evaluate feedlot performance of lambs from different backgrounding treatments. Seventy-two crossbred lambs were randomly assigned to one of four backgrounding treatments. Treatments were imposed after traditional, range-weaning practice (140 d of age). Treatments were: 1) drylot ad libitum access to 80:20 alfalfa:barley pellets (PELLET); 2) cool-season, grass-paddock grazing (GRASS); 3) unweaned, dormant-range grazing (LATE WEAN); and 4) weaned, dormant-range grazing (RANGE). After 29 d of backgrounding, lambs within backgrounding treatment were assigned to feedlot pens (3 pens/treatment). Lamb-BW and ultrasound measurements were taken at weaning (d-29), after backgrounding (d 0), after transition to 70 percent grain diet (d 19), and at the end of the feedlot period (d 68). Lambs backgrounded on PELLET had greater BW (P < 0.10) at d 0 and d 68 than lambs assigned to other treatments. Feedlot DMI of PELLET lambs was greater than all other treatments, and feedlot ADG of PELLET lambs was greater than LATE WEAN and RANGE lambs (P < 0.10). At the end of the feedlot period (d 68), ultrasound measures of LM were greater (P < 0.05) for GRASS than either LATE WEAN or RANGE when BW on d 68 was included as a covariable. No differences (P > 0.10) in 12th-rib-fat thickness were detected among treatments at d 68. Results from our 2007 study indicate that 29-d-background treatments on dormant range diminished subsequent-feedlot performance; however, GRASS backgrounding had similar feedlot performance to PELLET backgrounding.

Key Words: Backgrounding, Feedlot Performance, Tissue Deposition Lamb

Substituting distillers dried grains for cottonseed meal in lamb-finishing diets: growth, wool characteristics, and serum NEFA, urea N, and IGF-1 concentrations

Author: J. K. McEachern, T. R. Whitney, C. B. Scott, C. J. Lupton, and M. W. Salisbury

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Summary

Effects of replacing cottonseed meal (CSM) with corn distillers dried grains (DDG) on growth, wool, and serum NEFA, urea N (SUN), and IGF-1 concentrations were investigated in Rambouillet wether lambs. Lambs (n = 44) were individually fed ad libitum diets for 84 d containing DDG that replaced 0 percent (0DDG), 33 percent (33DDG), 66 percent (66DDG), or 100 percent (100DDG) of the CSM in a completely randomized design. Diet × day interactions were not observed (P > 0.12) for BW, ADG, DMI, degradable protein intake, or G:F. As DDG increased in the diet, ADG and G:F decreased quadratically (P = 0.08), but no difference (P = 0.13) in daily DMI was observed. Lambs fed 100DDG diet had similar (P > 0.23) ADG, average DMI, and G:F compared to lambs fed 0DDG diet. A diet × day interaction (P < 0.001) was observed for SUN, but not for serum NEFA or IGF-1 concentrations (P > 0.16). At times, SUN increased (P < 0.10) as DDG increasingly replaced CSM, which was attributed to an increase (quadratic, P < 0.001) in degradable protein intake. Serum NEFA decreased linearly (P < 0.08) and serum IGF-1 decreased quadratically (P < 0.05) as DDG increasingly replaced CSM in the diets. Wool characteristics were not affected (P > 0.10) by diet. Results indicated that DDG can replace all the CSM in lambfinishing diets without negatively affecting growth, efficiency of gain, or wool characteristics, and can potentially reduce cost of feed•kg-1 gain.

Key Words: Cottonseed Meal, Distillers Dried Grains, IGF-1, Lambs, Wool