Sheep & Goat Research Journal. Volume 22, 2007

Contents

Weaning Weights in a Range Purebred Merino and Crossbred Merino x Rambouillet Flock
Author: W.M. Rauw, H.A. Glimp, W. Jesko, L. Gomex-Raya
Peanut Stover and Bermudagrass Hay for Wethers on Summer Hardwood Rangeland in North Central Texas
Author: C.E. Packard, J.P. Muir, R.D. Wittie, R.M. Harp, M.A. Carr
Growth and Carcass Characteristics in Goat Kids Fed Grass- and Alfalfa-Hay-Based Diets with Limited Concentrate Supplementation
Author: S. Wildeus, J.M. Luginbuhl, K.E. Turner, Y.L. Nutall and J.R. Collins
Western Snowberry Response to Fire and Goat Browsing
Author: A.J. Smart, N.H. Troelstrup, Jr., K.W. Bruns, J.A. Daniel and J.E. Held
Superovulation in Sheep: Number and Weight of the Corpora Lutea and Serum Progesterone
Author: A.T. Grazul-Bilska, J.D. Kirsch, J.J. Bilski, K.C. Kraft, E.J. Windorski, J.S. Luther, K.A. Vonnahme, L.P. Reynolds, D.A. Redmer
Cash Versus Contract Marketing in the U.S. Lamb Industry
Author: C.L. Viator, S.C. Cates, M.K. Muth, S.A. Karns, G. Brester
Winter Grazing Systems for Gestating Ewes
Author: S.C. Loerch, D.D. Clevenger, G.D. Lowe and P.A. Tirabasso

Article Summaries

Weaning Weights in a Range Purebred Merino and Crossbred Merino x Rambouillet Flock

Author: W.M. Rauw, H.A. Glimp, W. Jesko, L. Gomex-Raya
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Summary

The Rafter 7 Merino flock was initiated in Nevada in 1990 with the purchase of 500 purebred Rambouillet ewes. A gradeup program was initiated using Australian Merino genetics with the aim of developing a purebred Merino flock. Early in the project the Rafter 7 Merino line was created, which is approximately 5/8 Merino and 3/8 Rambouillet and has been a closed line since 1999. In a genetic selection program that includes weaning weight, weights must be adjusted for environmental factors. The present study investigated factors influencing weaning weight in 9,594 lambs.

Results show a decrease in lamb weaning weights with the inclusion of Merino blood in the lines. At weaning, rams were heavier than ewes (P < 0.001) and weights decreased with increased litter size (P < 0.001). Lambs born from 2-year-old dams had lower weaning weights than lambs born from older dams (P < 0.01), and lambs born from 5-year-old dams had lower weaning weights than lambs born from 3-year-old dams (P < 0.05). Weaning weight of lambs born from 3-, 4-, 6-, and 7-year-old dams did not significantly differ.

Multiplicative-adjustment factors for adjusting lamb weaning weights to a common sex, age of dam, and birth-rearing type were compared with values from the Report of the National Sheep Improvement Program Technical Committee. Adjustment factors were slightly lower for triplet ewes and rams born from a 3- to 6-year-old dam. Other adjustment factors were very similar, suggesting that adjustment factors derived from more intensive production systems are applicable to our extensive production systems as well.

Peanut Stover and Bermudagrass Hay for Wethers on Summer Hardwood Rangeland in North Central Texas

Author: C.E. Packard, J.P. Muir, R.D. Wittie, R.M. Harp, M.A. Carr
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Summary

Goats in the south-central United States raised on rangeland often face a mid-summer forage quantity and nutritivevalue deficit that may be mitigated by feeding inexpensive hay or stover. Four wethers (Boer X Spanish goats) were assigned to wooded rangeland paddocks (eight head ha-1, two replications) and supplemented with either peanut (Arachis hypogea) stover (10 percent crude protein (CP)) or coastal bermudagrass (Cynodon dactylon) hay (12 percent CP) at 0.5 percent or 2.0 percent BW with two unsupplemented paddocks as control treatments. The hay and stover were also fed to wethers ad libitum in a traditional feedlot and compared to a complete feed ration (four head pen-1, two replications). For 10 weeks from July to September in 2002 (216 mm rainfall) and in 2003 (354 mm rainfall) average daily gains (ADG) were measured, while herbage availability, and ADF, ADL, NDF, and CP concentrations of the primary browse species were determined. Goats receiving 0.5 percent BW bermudagrass in 2002 had greater ADG than those in the control and 0.5 percent BW peanut paddocks (P < 0.1). There were no differences in ADG among goats fed 2.0 percent BW of bermudagrass and peanut stover or control animals in 2002. No differences in ADG were measured in 2003 when browse nutritive value was the same but quantity was 26 percent lower than 2002. Goats on the complete ration in the drylot had greater (P < 0.1) ADG than goats fed either hay or stover ad libitum both years. Goats on complete feed in the drylot had greater (P < 0.05) dressing percentages than animals fed either stover or hay (45 percent, 37 percent and 31 percent, respectively). Supplementing goats on hardwood range with bermudagrass hay at 0.5 percent BW improved ADG only when there were sufficient quantities of high-quality browse.

Growth and Carcass Characteristics in Goat Kids Fed Grass- and Alfalfa-Hay-Based Diets with Limited Concentrate Supplementation

Author: S. Wildeus, J.M. Luginbuhl, K.E. Turner, Y.L. Nutall and J.R. Collins
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Summary

Two experiments were conducted to evaluate the effect of feeding legume hay (alfalfa; Medicago sativa L.) or mixed-grass hay on ADG and carcass characteristics of growing goats. In Experiment 1, 24 Spanish kids, equally representing female, intact male and wether goats, were pen-fed ad libitum either chopped alfalfa (16.8 percent CP) or mixed grass hay (9.4 percent CP) (3 pens/diet) and a corn/soybean meal supplement (16 percent CP) at 1.5 percent BW for 102 d. Goats were harvested at a commercial abattoir. Average daily gain (62 vs. 37 g/d; P < 0.01), carcass weight (14.8 vs. 12.8 kg; P < 0.05) and dressing percent (52.9 percent vs. 50.4 percent; P < 0.05) were higher in alfalfa than grass-hay-fed goats, respectively. Backfat and percentage kidney/pelvic fat was lower (P < 0.05) in bucks (0.12 cm and 1.8 percent) than in does (0.17 cm and 5.7 percent) and wethers (0.22 cm and 4.0 percent). In Experiment 10-month-old Boer and Boer-cross wethers (n=16) were penfed ad libitum either chopped alfalfa (15.2 percent CP) or grass hay (10.9 percent CP) for 84 days. Forage was supplemented with concentrate (16.3 percent CP) at 1 percent of BW. Carcass characteristics were determined as described for Experiment 1. Wethers fed alfalfa hay had a higher ADG (158 vs. 119 g/d; P < 0.01) and dressing percentage (54.0 percent vs. 52.2 percent, P < 0.05), but did not differ in other carcass characteristics. Alfalfa feeding improved growth rate and dressing percentage, but had no effect on other carcass characteristics, whereas sex class influenced primarily carcass-fat content.

Western Snowberry Response to Fire and Goat Browsing

Author: A.J. Smart, N.H. Troelstrup, Jr., K.W. Bruns, J.A. Daniel and J.E. Held
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Summary

Managers of pastures in the northern tallgrass prairie region are faced with incomplete control of aggressive woody plant species, such as western snowberry (Symphoricarpus occidentalis Hook.) due to its high sprouting ability after fire or mowing and the reluctance of managers to use herbicides, which may harm desirable plant species. The objective of this study was to compare western snowberry response to fire and browsing by goats. The study was conducted from 2002 through 2006 at South Dakota State University?s Oak Lake Field Station in eastern South Dakota. Small, fenced plots of nativeprairie vegetation infested with western snowberry were established on burned (fall 2001) and unburned (>30 years) sites and grazed by goats for three to five days in late June. Western snowberry foliar cover, plant height, stem density and seed production were measured each year. Annual goat browsing in late June reduced western snowberry plant height and seed production in burned and unburned sites, but did not change foliar cover. Fire also reduced plant height and seed production. Stem density remained unchanged after four years of annual goat browsing or five years post fire and was unchanged in controls. Reducing nuisance, resprouting, woody species, such as western snowberry, in grasslands is difficult, but annual goat browsing and/or combination with frequent fire (

Superovulation in Sheep: Number and Weight of the Corpora Lutea and Serum Progesterone

Author: A.T. Grazul-Bilska, J.D. Kirsch, J.J. Bilski, K.C. Kraft, E.J. Windorski, J.S. Luther, K.A. Vonnahme, L.P. Reynolds, D.A. Redmer
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Summary

To determine similarities and differences between nonsuperovulated and superovulated ewe models, data collected from several experiments (1989 through 2005) were analyzed. Mature non-pregnant non-superovulated (n = 91) or superovulated (n = 299) Western range-type ewes were used for evaluation of luteal function. To induce superovulation, ewes were injected twice daily with FSH on days 13 to 15 of the estrous cycle. At corpora lutea (CL) collection on day 5 or 10 of the estrous cycle, the number of CL was determined. For selected ewes, the CL were weighed and blood samples were collected for determination of progesterone (P4) concentration in serum. Each year, a similar (P > 0.1) number of ovulations/ewe was induced by FSH treatment (range from 12.4 ? 2.0 to 20 ? 2.5/year). Superovulated ewes had greater (P < 0.001) number of CL than non-superovulated ewes (16.2 ? 0.5 vs. 1.9 ? 0.1). Weight of CL on day 5 of the estrous cycle was similar for superovulated and non-superovulated ewes (252.2 ? 4.1 vs. 224.7 ? 15.6 mg/CL), but on day 10, weight of CL from superovulated ewes was less (P < 0.05) than from non-superovulated ewes (379.9 ? 4.0 vs. 598.7 ? 18.5 mg/CL). Luteal tissue mass per ewe was greater (P < 0.001) for superovulated than non-superovulated ewes on days 5 (3.7 ? 0.4 vs. 0.5 ? 0.1 g) and 10 (6.1 ? 0.5 vs. 1.2 ? 0.1 g) of the estrous cycle. Serum P4 concentration on day 5 of the estrous cycle did not differ statistically (P > 0.1) for superovulated vs. non-superovulated ewes (2.3 ? 1.1 vs. 1.3 ? 0.1 ng/ml), but on day 10 tended to be greater (P < 0.06) in superovulated than non-superovulated ewes (5.8 ? 1.3 vs. 3.8 ? 0.3 ng/ml). When P4 concentration in serum was expressed per g of luteal tissue mass, values were similar for non-superovulated and superovulated ewes on days 5 and 10 of the estrous cycle. Moreover, all P4 values were greater (P < 0.05) on day 10 than on day 5 of the estrous cycle. Thus, despite some differences in CL number and CL weight, the major function of the CL, P4 production does not seem to be altered in superovulated ewes compared with non-superovulated ewes. Therefore, these data indicate that our superovulated ewe model may be used for studies of luteal function.

Cash Versus Contract Marketing in the U.S. Lamb Industry

Author: C.L. Viator, S.C. Cates, M.K. Muth, S.A. Karns, G. Brester
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Summary

Lamb operations in the United States are experiencing unfavorable market conditions, such as declining breeding inventories, stagnant domestic lamb consumption, and increasing competition from imported lamb. To more effectively compete, some operations may turn to nontraditional marketing arrangements, such as use of contracts, to purchase and sell lambs. To determine the extent of alternative marketing arrangements (AMAs) use in the U.S. lamb industry, we conducted a nationally representative mail survey of lamb producers and feeders. We received 302 completed surveys (53 percent weighted response rate). The survey collected information on purchases, sales and pricing methods, reasons why operations use their choice of marketing arrangements, and operation characteristics. We compared small and large operations, as well as Eastern and Western U.S. operations. Primarily U.S. lamb operations use cash-marketing methods to purchase and sell lambs. However, there appears to be a slight trend away from auction markets toward other types of cash-market transactions, such as direct trade. Large operations are more likely to use AMAs than small operations. Likewise, Western U.S. operations are more likely than Eastern operations to use AMAs. Large operations use AMAs to reduce risk, while small operations use AMAs to sell their lambs at higher prices.

Winter Grazing Systems for Gestating Ewes

Author: S.C. Loerch, D.D. Clevenger, G.D. Lowe and P.A. Tirabasso
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Summary

Four winter-feeding systems for gestating ewes were investigated over a 3-year period. The systems investigated were: 1) low-density corn; 2) high-density corn; 3) fescue regrowth; and 4) round-baled hay. Effects on ewe performance and winter-feed costs were determined. An average of 118 mature (3 to 7 year old) Hampshire x Dorset ewes (avg initial BW = 91.6 kg) were used each year. Each of the wintering-grazing treatments was replicated by two fields, and the hay treatment was replicated by two drylot pens. The low- and high-density corn treatments were planted to achieve densities of approximately 54,000 and 91,000 corn plants/ha, respectively. Each replicate corn field was 0.4 ha and contained 12 ewes. The stockpiled fescue treatment consisted of replicate fields of 0.8 ha, each containing 12 ewes. For the hay treatment, first-cutting fescue hay was offered free choice in replicate drylot pens of 23 ewes each. Ewes grazing low-density corn gained the most weight (10.9 kg), those grazing stockpiled fescue lost 1.8 kg and those grazing high-density corn and eating fescue hay in drylot were intermediate (7.7 and 5.9 kg, respectively; P < 0.01). Carrying capacity of both corn density treatments was similar. Stockpiled fescue pasture supported only 20 percent of the carrying capacity of the corn fields (P < 0.01). Grazing corn (both planting densities) resulted in feed costs of 19?/d and 23?/d for the low- and highplanting densities, respectively. Estimated costs for feeding fescue hay were 21?/d. Grazing stockpiled fescue was lowest at 17?/d. In conclusion, winter-grazing standing corn or stockpiled fescue were effective and economical feeding strategies to meet the nutritional needs of gestating ewes.