Sheep & Goat Research Journal. Volume 17, No. 2: 2002

Contents

Fall and Winter Grazing of Brassicas - a Value-Added Opportunity for Lamb Producers
Author: D.W. Koch, C. Kercher and R. Jones
Effects of Prenatal Shearing of Ewes on Birth Weight and Neonatal Survivability of Lambs
Author: S.J. Falck, G.E. Carstens and D.F. Waldron
Scrapie in Sheep: A Transmissible Spongiform Encephalopathy
Author: M.A. Smit , N.E. Cockett, J.E. Beever, T.L. Shay and S.L. Eng
Effect of Colostrum Intake on Serum Hormone Concentrations and Immunoglobulin G Absorption in Neonatal Lambs
Author: R.E.A. Mansur , D.W. Holcombe, L.B. Bruce and D. M. Hallford
Adipose Tissue Lipogenic Enzyme Activity, Serum IGF-I, and IGF-Binding Proteins in the Callipyge Lamb
Author: D.C. Rule, G.E. Moss, G.D. Snowder and N.E. Cockett
Technical Note - Genetic Control of Color in Dorper Sheep and Their Crosses
Author: D.R. Notter and D.P. Sponenberg
Research Note - Influence of Supplement Form on Ewe Performance and Reproduction
Author: N. Taylor, P.G. Hatfield, B F. Sowell and G.S. Lewis

Article Summaries

Fall and Winter Grazing of Brassicas - a Value-Added Opportunity for Lamb Producers

Author: D.W. Koch, C. Kercher and R. Jones
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Summary

Fast-growing cold-tolerant brassicas can be grown as a second crop, providing low-cost, high quality forage for fall-grazing lambs. In this study, cultural methods on irrigated fields included species and varieties, establishment method, second-crop planting dates (July 17 to August 12) and volunteer grain control. Brassicas were planted after several primary crops. Studies were conducted at the Powell, WY, Research and Extension Center from 1986 to 1996. Lamb performance was evaluated in seven grazing studies. Brassica forage production declined about 770 kg/ha per week when planted after July 20. Two to 3 metric tons/ha of forage was available in all years, except 1992, when soil fertility was low. Average daily gain (ADG) was similar for turnips and other species (tyfon, rape, radish). Over all studies, lambs grazing brassicas gained 0. 18 kg (0. 13 to 0. 25) per day. During the first month, lambs grazing turnips and other forages gained faster than drylot-fed lambs, but gained slower than drylot-fed lambs after the first month. Average lamb gain/ha was 308 kg. Gains of lambs grazing July-planted brassicas were 41% greater than with August-planted brassicas. The average number of lamb grazing days/ha was 1685. Brassica-grazed lambs gained subsequently as well in drylot as lambs not previously grazed. Carcass characteristics of lambs grazing brassicas were similar to those of lambs fattened in the drylot; however, grazed lambs required longer to reach target weights.

Key words : turnip, tyfon, rape, radish, sheep, weight gains.

Effects of Prenatal Shearing of Ewes on Birth Weight and Neonatal Survivability of Lambs

Author: S.J. Falck, G.E. Carstens and D.F. Waldron
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Summary

A three-year study was conducted with a flock of mixed-aged Rambouillet ewes to determine the effect of late-gestation shearing on lamb birth weights (N = 480) and survival rates during the neonatal period in typical West Texas conditions. Ewes were randomly assigned, within sire family and year of birth, to one of two shearing treatments, prenatal shorn or unshorn. The ewes remained on the same treatment for all 3 years. The prenatal shorn ewes were shorn in early January, 2 to 54 d prior to lambing (mean = 20 d). The unshorn ewes were shorn after lambs were an average of 96 d old. Lamb survival rates were analyzed using a model that included fixed effects of shearing, year, sex of lamb, type of birth, age of dam, significant interactions, and linear and quadratic effects of birth weight and ambient minimum temperature on the day of birth. Lamb survival rates were not affected by age of dam, but were lower (P < .02) on day 3 for triplet compared to twin and single lambs (74.3, 88.0 and 89.2 ? 5%, respectively). A significant interaction between sex of lamb and shear treatment (P < .05) was found for lamb survival. Male lambs from shorn ewes had 12% lower (P < .01) survival rates at one day of age than male lambs born to unshorn ewes, whereas, survival rates of female lambs was not affected by prenatal shear treatment. Lamb birth weight ranged from 1.6 to 7 kg and was not affected by shear treatment (P > .5). Lamb survival rates increased quadrat-ically as both birth weight (P < .05) increased and as minimum temperature on day of birth (P < .01) increased. Predicted lamb survival rates at 3 days of age for 3, 4, 5, and 6 kg birth weight lambs were 81.7, 91.0, 95.0 and 94.0 ? 4%, respectively. Predicted lamb survival rates at 3 days of age for minimum temperatures at lambing of-7,-1 and 4? C were 72.1, 88.8 and 93.5 ? 5%, respectively. The results of the present study demonstrate that prenatal shearing of Rambouillet ewes 20 d prior to lambing in typical West Texas conditions did not increase birth weights or improve survival rates of neonatal lambs.

Key words: birth weight, lambs, shearing, survivability

Scrapie in Sheep: A Transmissible Spongiform Encephalopathy

Author: M.A. Smit , N.E. Cockett, J.E. Beever, T.L. Shay and S.L. Eng
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Introduction

Scrapie is a transmissible, fatal, degenerative disorder of the central nervous system that affects sheep and goats. It belongs to a family of neurodegenerative diseases in mammals known as transmissible spongiform encephalopathies (TSEs), which includes bovine spongiform encephalopathy (BSE) in cattle, Creutzfeldt-Jakob Disease (CJD) in humans, and chronic wasting disease in deer and elk (Johnson and Gibbs, 1998). The focus of this review is on scrapie, which affects most sheep-producing countries in the world.

Effect of Colostrum Intake on Serum Hormone Concentrations and Immunoglobulin G Absorption in Neonatal Lambs

Author: R.E.A. Mansur , D.W. Holcombe, L.B. Bruce and D. M. Hallford
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Summary

Colostrum contains nutrients, immunglob-ulins, hormones, and growth promoting substances, such as insulin-like growth factor?I (IGF-1). An experiment was conducted to study the effects of feeding three amounts of colostrum on immunoglobulin G (IgG), and hormone concentrations during the first 18 hours of life. Fifteen Rambouillet x Merino lambs were assigned to three treatments. Pooled colostrum was fed at 10 mL/kg of body weight (BW), 20 mL/kg BW, or 30 mL/kg BW every 3 hours for 15 hours. Blood samples were obtained from lambs immediately after birth and every 3 hours through hour 18. Concentrations of growth hormone (GH), prolactin (PRL), triiodothyronine (T3) and thyroxine (T4) did not differ (P > .10) among treatments. Serum IgG, IGF-1 and insulin (INS) increased linearly (P < .03) as colostrum intake increased. A quadratic effect (P = .06) was detected for concentrations of GH as colostrum amounts increased. Feeding increasing amounts of colostrum following birth influenced serum IgG, INS, IGF-1 and GH concentrations, thereby, influencing both passive immunity and endocrine status in lambs. Feeding 10 mL/kg produce no health- related mortality at either a week of age or at weaning. Ten mL/kg of BW of colostrum every 3 hours for 15 hours may provide sufficient nutrition, growth-promoting factors and IgG to lambs at high risk.

Key Words: lamb,hormone,immunoglobu-lins, colostrum

Adipose Tissue Lipogenic Enzyme Activity, Serum IGF-I, and IGF-Binding Proteins in the Callipyge Lamb

Author: D.C. Rule, G.E. Moss, G.D. Snowder and N.E. Cockett
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Abstract

The purpose of this study was to determine if reduced adipose tissue accretion in callipyge lambs during growth was related to activities of lipogenic enzymes and serum concentrations of insulin, insulin-like growth factor-I (IGF-I), and IGF-binding proteins. Normal lambs were homozygous normal (clpg/clpg), and callipyge lambs were heterozygotes (CLPG/clpg). Lambs were slaughtered at 25, 41, 57, or 73 kg (target live weight groups), with five normal and five callipyge lambs in each weight group. Subcutaneous, intermuscular, and perirenal adipose tissue samples were dissected as soon as possible after slaughter from the 41, 57, and 73 kg groups. Tissue homogenates were prepared for assay of fatty acid synthase, acyl-CoA synthetase, glycerophosphate acyltransferase, and lipoprotein lipase activities. Most numeric values for enzyme activities were higher for the normal lambs in each adipose tissue depot. Callipyge lambs had lower (P = 0.05) glycerophosphate acyltransferase activity in subcutaneous adipose tissue at 41 kg. In intermuscular adipose tissue, each enzyme activity was lower (P < 0.05) at 41 kg for callipyge lambs. In perirenal adipose tissue, fatty acid synthase and glycerophosphate acyltransferase activities were lower (P = 0.02) for callipyge lambs at 41 kg, and acyl-CoA synthetase was lower (P = 0.02) for callipyge lambs at 73 kg.. Serum concentrations of insulin were not affected by genotype (P > 0.20). Serum insulin in non-fasted callipyge lambs was not affected by body weight, but increased with weight in non-fasted normal lambs (P = 0.03). Two-day fasted lambs had decreased serum insulin in both genotypes, which increased (P = 0.03) similarly with body weight for both genotypes. Serum IGF-I was greater (P = 0.09) in normal lambs at 73 kg, whereas IGF-I in 2-d fasted callipyge lambs was greater (P = 0.03) than normal lambs. No genotype effects were observed for the relative proportions of the IGF-binding proteins. We conclude that callipyge lambs had lower lipogenic enzyme activities in adipose tissue than normal lambs, but these changes were not related to serum concentrations of insulin or IGF-I.

Key words: lambs; callipyge; lipogenesis; insulin

Technical Note - Genetic Control of Color in Dorper Sheep and Their Crosses

Author: D.R. Notter and D.P. Sponenberg
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South African Dorper sheep were imported into the U.S. during the 1990?s, and have generated considerable interest within the American sheep industry. The typical South African Dorper is a white animal with a black head, although both entirely white animals and white animals with red heads also occur. The Dorper breed was derived from crosses between the Dorset and the Blackhead Persian, beginning in the 1940?s (Milne, 2000), and the Dorper color pattern is essentially the same as that of its Blackhead Persian parent. The typical Dorper coat is composed predominantly of hair fibers, although many animals possess a detectable proportion of wool fibers and some have a distinctively wooly coat (Cloete et al., 2000). Shedding of wool fibers, when they are present, is common, and shearing is not practiced in commercial flocks.

Research Note - Influence of Supplement Form on Ewe Performance and Reproduction

Author: N. Taylor, P.G. Hatfield, B F. Sowell and G.S. Lewis
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Supplementing ewes grazing dormant rangeland pastures with protein is a common practice in the Northern Great Plains. Supplement form can impact individual animal intake and performance. Ducker et al. (1981) reported that 19 % of 2,931 grazing ewes failed to consume any supplements when offered supplement in block form. Taylor et al. (2000) reported that only 2 % of ewes given pellets were non-consumers, while 35 % of those offered blocks were non-consumers. Bowman and Sowell (1997) summarized a number of ewe studies and reported that the mean coefficient of variations in supplement intake by ewes that were hand-fed pelleted supplements were significantly less than those reported for block-fed ewes. However, few studies have examined how these two-supplement forms affect ewe performance when fed under commercial conditions. The objective of this study was to compare how supplement form (pellets or cooked molasses block) influenced ewe body weight, body condition, wool characteristics, and lambing percentage.