Sheep & Goat Research Journal. Volume 18: 2003

Contents

Interrelationships of Traits Measured on Fine-wool Rams During a Central Performance Test
Author: C.J. Lupton, D.F. Waldron and F.A. Pfeiffer
Effects of Supplementing Polyethylene Glycol to Goat Kids Grazing Sericea Lespedeza and Early Post-weaning Nutritive Plane Upon Subsequent Growth
Author: R.C. Merkel, A.L. Goetsch and N. Silanikove
Use of DNA Markers to Determine Paternity in a Multiple-Sire Mating Flock
Author: A.M. Laughlin, D.F. Waldron, B.F. Craddock, G.R. Engdahl, R.K Dusek, J.E. Huston, C.J. Lupton, D.N. Ueckert, T.L. Shay and N.E. Cockett
Use of the Lamb Vision System to Predict Carcass Value
Author: A.S. Brady, B.C.N. Cunha, K.E. Belk, S.B. LeValley1, N.L. Dalsted, J.D. Tatum and G.C. Smith
Potential Associative Effects of Increasing Dietary Forage in Limit-fed Ewes Fed a 6% Fat Diet
Author: O. Kucuk, B.W. Hess P.A. Ludden and D.C. Rule
Quebracho Tannin Influence on Nitrogen Balance in Small Ruminants and In-Vitro Parameters when Utilizing Alfalfa Forage
Author: K.E. Turne and J.P.S. Neel
An Investigation into the Risk Factors Associated with Clinical Mastitis in Colorado Sheep
Author: K.N. Forde, B.J. McCluskey and K.S. Morgan
Weight Changes in Fall and Spring Lambing Ewes Grazing Fallow Wheat Fields During the Summer
Author: W.A. Phillips, F.T. McCollum, J. Volesky and H.S. Mayeux
Effect of Ethanol Supplementation on In Vitro Digestion and VFA Production and Growth Performance of Newly Weaned
Author: J. Gould, E.J. Scholljegerdes, P.A. Ludden, D.C. Rule, and B.W. Hess
Growth and Reproductive Performance of Ewe Lambs Implanted with Zeranol after Weaning, but before Sexual Maturation
Author: B.M. Alexander, B.W. Hess, R.V. Lewis, R.H. Stobart and G.E. Moss
Consumer Evaluation of Pre-Cooked Lamb
Author: J.A. Fox, L.S. Vander Wal, P. Udomvarapant, D.H. Kropf, E.A.E. Boyle and C.L. Kastner
Caprine Arthritis-Encephalitis: An Update
Author: A. de la Concha-Bermejillo
An Evaluation of Different Energy Supplements for Lambs Consuming Endophyte-free Tall Fescue
Author: B.W. Hess, J.E. Williams and E.J. Scholljegerdes
Effects of the FecB Gene in Half-sib Families of Rambouillet-cross Ewes
Author: K.S. Schulze, D.F. Waldron, T.D. Willingham, D.R. Shelby, G.R. Engdahl, E. Gootwine, S. Yoshefi, G.W. Montgomery, M.LTate and E.A. Lord
The Effects of Energy Source and Ionophore Supplementation on Lamb Growth, Carcass Characteristics and Tenderness
Author: M.A. Murphy, H.N. Zerby and F.L. Fluharty
Effects of Supplementing Ewes with d-a-Tocopherolon Serum and Colostrum Immunoglobulin G Titers and Preweaning Lamb Performance
Author: C.L. Schultz, T.T. Ross and M.W. Salisbury
Comparing Indicators of Sheep Grazing Leafy Spurge and Perennial Grasses
Author: B.E. Olson and R.T. Wallander
Research Note - Repeated Injections of Pregnant Mare Serum Gonadotrophin (PMSG) Failed to Induce Antibody Production in Fall Lambing Ewes
Author: M.A. Diekman, M.K. Neary and G.R. Kelly
Case Report - Monensin Poisoning in a Sheep Flock
Author: O. Mendes, F. Mohamed, T.Gull and A. de la Concha-Bermejillo

Article Summaries

Interrelationships of Traits Measured on Fine-wool Rams During a Central Performance Test

Author: C.J. Lupton, D.F. Waldron and F.A. Pfeiffer
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Summary

A pooled correlation analysis was conducted to estimate the relationships between all traits measured on fine-wool rams (n = 505) during three central performance tests (2000 - 2002). Introduction of minimum initial weight levels (for certification) was expected to have an effect on previously reported significant correlations. In addition to the reported traits, several other traits (measures of variability in fiber diameter, average fiber curvature and variability, for example) that have not previously been reported were included in the analysis. The correlation coefficients calculated are expected to assist breeders to better understand the consequences of their actions when selecting for individual traits. Observed differences between core and side sample average fiber diameters were not highly correlated with any other traits currently measured on the test. Average fiber curvature was not highly correlated with any measure of average fiber diameter but was negatively correlated with several important production traits which may have serious negative consequences for breeders who are selecting for or trying to maintain small crimp. Finally, older rams were shown to be at a disadvantage in the test because age is antagonistically correlated with most of the traits used to evaluate the rams.

Key words: traits, rams, central performance test

Effects of Supplementing Polyethylene Glycol to Goat Kids Grazing Sericea Lespedeza and Early Post-weaning Nutritive Plane Upon Subsequent Growth

Author: R.C. Merkel, A.L. Goetsch and N. Silanikove
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Summary

Forty-eight Boer x Spanish doelings (4 mo of age, 20.9 + 2.35 kg) were used to test effects of polyethylene glycol (PEG) supplementation of grazed sericea lespedeza and early post-weaning nutritive plane and growth rate on subsequent performance with a concentrate-based diet fed in confinement. Treatments were: Barn, with goats kept in individual pens for the 24-wk trial and fed a 70% concentrate diet (17% CP, 69% TDN) free-choice, C, and PS, with two groups of eight doelings per group for each treatment. In the first 6 wk (Phase 1), C and PS groups grazed 0.4-ha lespedeza paddocks (two paddocks and groups per treatment) and were group-supplemented with 88 g/d per animal of concentrate without (C) or with (PS) an additional 25 g/d per animal of PEG. Because of limited rainfall in Phase 1 and the resultant low availability of growing forage, in Phase 2 (6 wk) treatments were changed in a manner thought to increase differences in BW and ADG between C and PS that developed in Phase 1. In Phase 2, C groups resided in two 1-ha paddocks dominated by crabgrass, whereas PS groups grazed two previously ungrazed 1-ha lespedeza paddocks and were supplemented with 1.5% BW of the Barn diet. In Phase 3, the final 12 wk, all doelings consumed ad libitum the 70% concentrate diet in confinement. Phase 1 ADG ranked (P < 0.05) Barn > PS > C (154, 95, and 47 g/d, respectively; SE 10.7). ADG in Phase 2 (70, 55, and 57 g/d; SE 9.3), Phase 3 (77, 82, and 72 g/d; SE 8.5), and the whole trial (94, 78, and 62 g/d for Barn, PS, and C, respectively; SE 8.2) were similar among treatments (P > 0.05). In conclusion, PEG may have potential to improve ADG by goat kids grazing tannin-containing sericea lespedeza, although testing over a longer period of time is needed. Differences in ADG in the early portion of the grazing period did not affect ADG later when a concentrate-based diet was fed, relative to continuous consumption of the concentrate-based diet.

Key words: sericea lespedeza, goats, daily gain, polyethylene glycol, tannins

Use of DNA Markers to Determine Paternity in a Multiple-Sire Mating Flock

Author: A.M. Laughlin, D.F. Waldron, B.F. Craddock, G.R. Engdahl, R.K Dusek, J.E. Huston, C.J. Lupton, D.N. Ueckert, T.L. Shay and N.E. Cockett
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Abstract

This study was conducted to evaluate the feasibility of determining sires of progeny using DNA markers in a group-mating Rambouillet flock. Four Rambouillet rams were used in the matings. Blood was collected on rams, ewes, and lambs and DNA marker genotypes were determined using three DNA microsatellite markers. Sire assignments were made based on the genotype results. Sires were assigned to 92% of the lambs using these three markers. Mismothering was evident in 10% of the lambs because the markers indicated that the apparent dam was not the actual dam. Without knowledge of the dam's marker genotype, sires would have been assigned to only 73% of the lambs. Using DNA analysis to determine paternity in a group mating flock is technically feasible. The number of markers required to assign paternity depends on variability among the sires for the chosen markers.

Key words: Sheep, DNA, microsatellites, paternity

Use of the Lamb Vision System to Predict Carcass Value

Author: A.S. Brady, B.C.N. Cunha, K.E. Belk, S.B. LeValley1, N.L. Dalsted, J.D. Tatum and G.C. Smith
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Summary

The need for a value-based marketing system in the U. S. lamb industry has been recognized. This study was conducted to evaluate use of the Lamb Vision System, a video imaging device, to predict lamb carcass value. Data from lamb carcasses (N = 246) that were fabricated into primal/sub-primal cuts served as the test population data set, from which value-prediction methods were developed. In addition, an additional data set of 642 carcasses, provided by Research Management Systems, Inc. (RMS), Fort Collins, CO was utilized to validate the value-prediction methods developed. Values predicted using data from the Lamb Vision System were able to account for 50-54% of the observed variability in boxed carcass value, with more accuracy compared to the traditional, hot carcass weight-based value assessment method which accounted for 25-33% of the variation in boxed carcass value. The Lamb Vision System presents the U. S. sheep industry with the opportunity to more accurately assess individual lamb carcass value.

Key words: Lamb, Carcass Value, Value-Based Pricing

Potential Associative Effects of Increasing Dietary Forage in Limit-fed Ewes Fed a 6% Fat Diet

Author: O. Kucuk, B.W. Hess P.A. Ludden and D.C. Rule
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Abstract

The objective of this study was to determine how site and extent of nutrient digestion are affected by dietary forage level in ewes when the diet contains 6% crude fat by soybean oil supplementation. Five mature ewes (66.5 ? 12.8 kg of initial BW) fitted with ruminal and duodenal cannulas were used in a 5 x 5 Latin square experiment. Diets (13.9% CP, DM basis) were fed at 1.3% of BW and included bromegrass hay, cracked corn, corn gluten meal, urea, and limestone. Dietary fat was adjusted to 6% (DM basis) with soybean oil and included one of five dietary forage levels (18.4%, 32.2%, 45.8%, 59.4%, and 72.9%). Chromic oxide was used as a digesta flow marker. Ruminal pH increased (linear, P< 0.001) from 5.7 to 6.5 and VFA concentration decreased (linear, P < 0.001) with increased dietary forage. Ruminal, post-ruminal, and total tract OM digestibility decreased (linear, P < 0.06) with increased dietary forage. Ruminal starch digestibility was unaffected (P = 0.76) by treatment. Post-ruminal and total tract starch digestibility decreased (linear, P
< 0.001) with increased dietary forage. Ruminal NDF digestibility increased (linear, P < 0.05) as dietary forage increased, but post-ruminal and total tract NDF digestibilities did not differ (P > 0.23). True ruminal N digestibility was not affect ed (P = 0.29) by dietary forage level. In contrast, microbial efficiency increased from 34.3 to 47.3 g microbial N/kg of OM truly digested as dietary forage increased from 18.4 to 45.8% , then decreased to 37.1 g microbial N/kg of OM truly digest ed on the highest forage diet (quadratic, P < 0.001). Total tract N digestibility decreased (linear, P < 0.05) with increased dietary forage. We conclude that the general pattern of nutrient digestion reflects the quality of dietary ingredients when mature ewes are restricted-fed a 6% fat diet ranging from 18.4% to 72.9% forage. Total tract OM digestibility was greater than anticipated for the 59.4 and 72.9% forage diets, suggesting that positive associate effects are possible with high-forage diets containing 6% dietary fat.

Key words: Sheep, Ruminal digestion, Dietary fat

Quebracho Tannin Influence on Nitrogen Balance in Small Ruminants and In-Vitro Parameters when Utilizing Alfalfa Forage

Author: K.E. Turne and J.P.S. Neel
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Summary

Feeding studies using small ruminants and laboratory experiments were conducted to evaluate the level of quebracho tannin (QT) supplementation to alfalfa hay diets on plant protein nitrogen (N) use, organic matter (OM) and fiber disappearance, and in vitro ammonia production. In two separate feeding trials, sheep [Experiment 1; 12 crossbred wether lambs (avg wt 47.7 kg)] or goats [Experiment 2; 12 crossbred Boer wether kids (avg wt 32.7 kg)] were randomly assigned to one of four dietary treatments replicated three times. Lambs or kids were offered chopped alfalfa (Medicago sativa L.) hay supplemented with QT at 0.0, 0.75, 1.5, or 3.0% of the total dry matter (DM) intake. Sheep and goat diets containing 1.5 and 3.0% QT had higher (P < 0.05) fecal N excretion (g/d) than animals offered the 0.0 and 0.75% QT. As a result of greater fecal nitrogen loss, overall N digestibility was lower in sheep (P < 0.07) and goats (P < 0.05) offered the higher QT compared to 0.0 and 0.75% QT supplemented animals. Serum urea nitrogen was 11% lower in QT supplemented goats compared to goats offered no QT. Calculated in vivo neutral detergent fiber (NDF) digestibility was lower (P < 0.10) in lambs offered 1.5 and 3.0% QT diets when contrasted with lambs offered 0.0 and 0.75% QT. In laboratory studies using alfalfa hay incubated with QT, lag time for in vitro organic matter disappearance (IVOMD) was greatest (P < 0.05) for 3.0% QT when contrasted with 0.0, 0.75, and 1.5% QT, and at 48 h, IVOMD decreased quadratically(P < 0.05) with QT addition. At 96 h, %NDF remaining decreased qua-dratically (P < 0.07) with QT additions. In vitro ammonia concentrations at 6 and 12 h were lower (P < 0.05) in tubes containing 1.5 and 3.0% QT when contrasted with tubes containing 0.0 and 0.75% QT. Further investigation is needed to define QT concentrations that allow optimal N and fiber utilization when ruminants are offered high protein, low energy diets or when grazing high quality pastures.

Key words: lamb, goat, quebracho tannin, nitrogen-use

An Investigation into the Risk Factors Associated with Clinical Mastitis in Colorado Sheep

Author: K.N. Forde, B.J. McCluskey and K.S. Morgan

Summary

A questionnaire was designed to assess the prevalence of mastitis and associated risk factors for Colorado sheep operations during the 1999 lambing season and was mailed to 829 producers in January 2000. Responses were received from 188 producers and the data from these questionnaires was analyzed using EpiInfo Version 6.04b. Prevalence was defined as the total number of reported mastitis cases in a given flock during the 1999 lambing season divided by the total number of ewes in that flock. The mean prevalence of mastitis among sheep from Colorado owners that responded was found to be approximately 6%. Of the 188 producers that responded, 80.3% represented farm flocks, 11.2% were herded range flocks, and 8.5% were fenced range flocks. The majority of producers (84%) lambed in sheltered pens, and of those producers, 83% used small pens which housed anywhere between 5 and 20 head. Producers reported that mastitis was most likely to occur in lambing sheds (40%), in a band (23%) and in small mixing pens (22%). Sixty-eight percent of the reported mastitis cases occurred in ewes three years of age or older with the highest prevalence of mastitis (35%) occurring in ewes that were five to six years of age. Trends were observed but the only statistically significant factors (P < 0.05) found in this study were lambing in April and the Corriedale breed. Confounding factors, including pre-ventative husbandry and management procedures, may account for these results.

Key words: Sheep, Mastitis, Udder Health, Risk Factors, Prevention Strategies

Weight Changes in Fall and Spring Lambing Ewes Grazing Fallow Wheat Fields During the Summer

Author: W.A. Phillips, F.T. McCollum, J. Volesky and H.S. Mayeux
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Summary

A total of 2714 fall and spring lambing ewes ranging in ages from 1 to 6 years were used over a three-year period to determine body weight changes during the summer grazing period (June, July and August). Ewes grazed either fallow winter wheat fields at an average stocking rate of 13.3 ewes/ha or Bermudagrass (Cynodon dacty-lon) pastures at a stocking rate of 2.5 ewe/ha. Fallow winter wheat fields were grazed for an average of 56.7 d and provided an average of 654 grazing d/ha over the three-month summer fallow period. Ewes grazing Bermudagrass pastures gained more (P = .02) weight over the summer than ewes grazing fallow wheat fields, but the amount gained by either group was greater than needed for ewes in the first 15 weeks of pregnancy or for ewes that were non-pregnant and not lactating. The standing forage available for grazing in fallow winter wheat fields consisted of broadleaf weeds, warm and cool season grasses, and wheat straw. It appeared that weight gains were greater when more of the standing forage was in the form of grasses than as wheat straw. Using ewes for biological control of accumulation of above ground biomass during the summer fallow period did not consistently result in lower fall forage and spring wheat grain production as compared to using herbicides to fallow the fields. Fallow winter wheat fields can be used during the summer to provide standing forage that is high enough in nutrient density to support pregnant and open ewes, but not without decreasing subsequent production of forage or grain.

Key words: Sheep, Biological control, Summer fallow, Wheat, Weight gains.

Effect of Ethanol Supplementation on In Vitro Digestion and VFA Production and Growth Performance of Newly Weaned

Author: J. Gould, E.J. Scholljegerdes, P.A. Ludden, D.C. Rule, and B.W. Hess
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Summary

The objectives of these studies were to determine the effects of ethanol (ETOH) supplementation on DM digestibility and VFA production in an in vitro system and on growth performance of newly weaned lambs. For Exp. 1, four ruminally cannu-lated beef heifers were used as ruminal fluid donors for an in vitro trial. Two of these heifers received a commercial rice hulls-based supplement containing ETOH (Corner Post, Free Choice Enterprises, Richland, Iowa) for 14 d before ruminal fluid collection (adapted), whereas the other two heifers received no supplement (unadapted). Substrates included 0.5 g oat hay (OH) or 0.44 g oat hay plus 0.06 g ETOH supplement (ES). Data were analyzed as a split-plot with adaptation to ETOH supplement as the main-plot and type of substrate as the sub-plot factor. At 6 h of incubation, in vitro dry matter disappearance (IVDMD) tended to be greater (P = 0.09) for adapted than unadapted ruminal fluid, and OH had greater (P > 0.02) IVDMD, total VFA concentrations, and molar proportions of acetate, butyrate, iso-valerate, and valerate than ES. Adaptation to ETOH supplement improved (P = 0.03) 48-h IVDMD of OH and ES. At 12 h, ruminal fluid adapted to ETOH supplement increased (P = 0.03) total VFA from OH substrate. By 24 h of incubation, adaptation or dietary substrate effects on total VFA and molar proportions of individual VFA were not significant (P < 0.60). For Exp. 2, 24 Rambouillet crossbred lambs (25.0 ? 0.4 kg) were blocked by body weight and allotted to one of 12 pens resulting in two lambs per pen with four replications per treatment. Lambs were fed no supplement (CON), the commercial ETOH supplement (ES), and the ETOH supplement dried (DRY) to evaluate the commercial supplement without the ETOH. Experimental treatment differences were evaluated using orthogonal contrast comparing CON vs. supplement and ES vs. DRY. Overall (d-0 to d-42) DMI and ADG were not different for CON vs supplement (P = 0.71 and 0.63, respectively) or ES vs DRY (P = 0.83 and 0.41, respectively). We conclude that adaptation of ruminal microflora to ETOH supplementation will improve diet digestibility, but the improvement in diet digestibility is not sufficient to enhance growth performance of newly weaned lambs.

Key Words : Lambs, Ethanol, Supplementation, Digestion, Growth

Growth and Reproductive Performance of Ewe Lambs Implanted with Zeranol after Weaning, but before Sexual Maturation

Author: B.M. Alexander, B.W. Hess, R.V. Lewis, R.H. Stobart and G.E. Moss
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Summary

Reproductive and growth performance was evaluated in weaned ewe lambs implanted with zeranol (12 mg, Ralgro, Shering Canada, Inc.) at weaning. In Exp. 1, white-faced ewe lambs (BW = 29.5 ? 0.1 kg) were stratified by body weight and randomly allotted to control (n = 30) or implanted (n = 30) groups. Lambs were fed to achieve gains of 0.23 kg/hd/d for an 84 d period. Five non-pregnant animals from each group were slaughtered during the ane-strous season and reproductive tract and ovarian weights were obtained. In Exp. 2, implanted (n = 10) and control (n = 10) ewe lambs (BW = 36.9 ? 0.4 kg) were individually fed a complete ration formulated to achieve gains of 0.23 kg/d for a 63 d period. Ewes were exposed to fertile rams during the breeding season in Exp. 1 and Exp. 2 and pregnancy rates were determined by ultrasound. In Exp. 1, ewes with zeranol implants had greater (P=0.01) gain efficiency and gained more (P=0.02) weight by 42 d than control ewes. Implanted ewes ended the 84 d growth study heavier (P=0.01) than control ewes. Differences were not noted in days to first estrus (P=0.58) or overall pregnancy rates (P=0.29; 43.3% and 30.0% for control and implanted ewes, respectively). However, ovarian weights (P=0.06), but not total reproductive tract weights (P=0.47), tended to be lighter in implanted than control ewes. In Exp. 2, ewes with zeranol implants were numerically heavier by the end of the 63 d growth study than control ewes, however, differences did not reach statistical significance (P=0.31). Differences in gain (P=0.46) or gain efficiency (P=0.48) were not noted in Exp. 2. As in Exp. 1, overall pregnancy rates did not differ (P=0.37) between control (60%) and zeranol (40%) treated ewes. Implanting weaned ewe lambs with zeranol may enhance growth performance and gain efficiency without affecting reproductive performance. However, numbers in the present study were limited and the numerical trends for decreased reproductive performance of implanted ewe lambs may need to be considered if a large proportion of the ewe lambs will be kept as replacement females.

Key words: Zeranol, Ewe Lambs, Growth, Reproduction

Consumer Evaluation of Pre-Cooked Lamb

Author: J.A. Fox, L.S. Vander Wal, P. Udomvarapant, D.H. Kropf, E.A.E. Boyle and C.L. Kastner
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Summary

A cook-in-bag lamb in curry sauce product was evaluated by 166 consumers in three separate experiments. When the product was identified as lamb it received favorable evaluations for taste and tenderness. In blind testing a majority of participants were unable to distinguish the lamb product from a similarly prepared beef product. The hypothesis that the lamb and beef products were equally likely to be preferred could not be rejected.

Key words: Consumer evaluation, lamb shoulder, value-added

Caprine Arthritis-Encephalitis: An Update

Author: A. de la Concha-Bermejillo
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Abstract

Caprine arthritis encephalitis (CAE) is a disease most commonly recognized in adult goats and manifested clinically as chronic degenerative polyarthritis, interstitial mastitis, and/or pneumonia. Occasionally, CAE may be characterized by acute leukoen-cephalomyelitis, particularly in 2 to 6 month-old kids. The disease is caused by caprine arthritis-encephalitis virus (CAEV), a lentivirus closely related to other human and animal lentiviruses, particularly ovine lentivirus (OvLV).

In the majority of industrialized countries, CAE is considered one of the most devastating diseases of dairy goats. In the United States of America, the prevalence of serum antibodies against CAEV in dairy goat herds ranges from 38 to 81%. The negative impact of this infection is associated to direct production loses as a result of clinical disease and related secondary infections, to animal deaths, and indirectly due to trading restrictions that some countries impose on infected herds.

The main route of transmission is through milk and colostrum from infected nannies to their offspring. Currently, there are no commercial treatments or vaccines available to control or prevent CAE. As a result, identification of CAEV-infected goats by serological means and elimination of positive reactors is a practice often used to achieve CAE-free status in herds. The separation of offspring from their mothers before ingestion of colostrum and their feeding with heat-inactivated colostrum and milk replacers is used for control purposes as well. However, this method is labor intensive and not always effective.

As a result of recent advances in genetic engineering and molecular virology, new approaches for the control of infectious diseases of livestock are being developed. These new technologies are likely to provide the means for more effective ways to control and eradicate CAE and other infectious diseases of livestock.

An Evaluation of Different Energy Supplements for Lambs Consuming Endophyte-free Tall Fescue

Author: B.W. Hess, J.E. Williams and E.J. Scholljegerdes
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Summary

Twenty-five, growing, Dorset and Dorset cross wether lambs (avg BW of 32.8 kg) were used in a completely random design to evaluate the effect of source of supplemental energy on total tract digestibility, N balance, and serum metabolites. Following an initial 10-d adaptation to fresh-chopped, boot stage tall fescue, another 14-d adaptation period was used to allow lambs to acclimate to one of five experimental treatments. A 7-d total fecal and urine collection followed, and approximately 7 mL of whole blood was collected via venipuncture of the jugular vein on d 7 of the collection period. Treatments included: 1) fresh-cut forage only (CON); 2) CON plus dried molasses (MOL); 3) CON plus dried beet pulp (BEP); 4) CON plus soybean hulls (HUL); and 5) CON plus ground corn (GRC). Supplements were formulated to provide 27.1 g of ruminally degradable nitrogen (RDN)/kg of ruminally digestible OM (RDOM). Isolated soy protein was used to increase the RDN of the BEP, MOL, and GRC diets so that all supplements were isonitrogenous (avg N intake = 13.4 g/d). Total tract DM digestibility was greater (P < 0.05) for BEP, HUL, and GRC compared to MOL and CON. Nitrogen balance did not differ (P = 0.15) among treatments; however, urinary N excretion tended (P < 0.08) to be greater for unsup-plemented lambs when compared to BEP, HUL, and GRC with MOL being intermediate. Additionally, serum urea nitrogen (SUN) concentrations were less (P < 0.05) for all supplemented wethers. Serum glucose concentrations did not differ (P = 0.40) across treatments. Greater SUN concentrations for lambs fed fresh-chopped tall fescue resulted in slightly greater urinary N excretion, suggesting that N utilization was better for supplemented lambs. Balancing RDN:RDOM with supplemental dried beet pulp, soybean hulls, or ground corn may be a management strategy to reduce N excretion by lambs consuming tall fescue pastures.

Key words: Lambs, Supplementation, Serum metabolites, Nitrogen balance

Effects of the FecB Gene in Half-sib Families of Rambouillet-cross Ewes

Author: K.S. Schulze, D.F. Waldron, T.D. Willingham, D.R. Shelby, G.R. Engdahl, E. Gootwine, S. Yoshefi, G.W. Montgomery, M.LTate and E.A. Lord
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Abstract

Records of Booroola-Rambouillet ewes (N = 94) were analyzed to estimate the difference between carriers (B+) and non-carriers of the FecB gene for ovulation rate, fertility, litter size, number of lambs weaned, fleece weight, and body weight within paternal half-sib families. The ewes were progeny of heterozygous (B+) Booroola-Rambouillet rams (n=5) mated to homozygous (++) Rambouillet ewes. Genotype at the FecB locus was predicted using DNA markers known to be linked to the FecB locus. The estimated differences between B+ and ++ ewes were +1.18 ? .12 ova/cycle (P=.0001) for ovulation rate, +.51 ? .16 lambs born/ewe lambing (P=.002), and +.18 ? .18 lambs weaned/ewe lambing (P=.34) in first-parity ewes. Estimated body weight differences between B+ and ++ ewes were -.88 ? .97 kg at 7 mo of age (P = .36) and -2.10 ? 1.15 kg at 18 mo of age (P = .07). Greasy fleece weights at 15 mo of age were not different between predicted FecB genotypes (P = .48). Assignment of genotype based on linked DNA markers effectively identified ewes that are heterozygous carriers and those that are non-carriers for FecB. Ewes predicted to be B+ had significantly greater ovulation rate and litter size compared to their ++ half-sibs. The difference between B+ and ++ ewes was generally not significant (P> .05) for other traits.

Key words: Sheep, Rambouillet, Booroola Merino, Reproduction, Marker assisted selection

The Effects of Energy Source and Ionophore Supplementation on Lamb Growth, Carcass Characteristics and Tenderness

Author: M.A. Murphy, H.N. Zerby and F.L. Fluharty
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Summary

Commercial Hampshire x Dorset crossbred lambs (n = 96) were used in a 3 x 2 factorial experiment to determine the effects of energy source (high concentrate (HC), high forage (HF), a combination of concentrate and forage (MIX)); and ionophore supplementation (monensin; Rumensin [Elanco Animal Health, Greenfield, IN] fed at a rate of 176 mg per kg of feed) on lamb growth and carcass characteristics. The wethers (n = 48) were harvested and the effects of energy source and ionophore supplementation on carcass characteristics and palatability attributes were evaluated.

Energy source affected (P < .05) dry matter intake, average daily gain (ADG), feed efficiency (FE), and days on feed. Lambs fed the HF diet had the lowest (P < .05) ADG (204 g), the least (P < .05) desirable FE (0.139 g/f), and consequently the most (P < .05) days on feed (106 d). Carcasses from lambs fed the HF diet also had less (P < .05) bodywall thickness, less kidney and pelvic fat, a smaller ribeye area, and lighter liver weights. Longissimus dorsi samples from the lambs on the HC diet had significantly (P < .05) higher Warner-Bratzler shear force values than the lambs on the HF and MIX diets. The sensory panel found longissimus dorsi samples from lambs that received the MIX diet significantly (P < .05) more tender when compare to those from lambs that received the HC and HF diets.

Monensin decreased (P < .05) backfat by 1.22 mm (20%) and dressing percentage by 3.1%. Monensin had no adverse effects (P > .05) on sensory attributes. Therefore, feeding monensin to lambs fed various diets resulted in no adverse carcass characteristics and a slight decrease in back fat depth.

Key words: Ionophore, Lamb, Growth, Carcass, Tenderness

Effects of Supplementing Ewes with d-a-Tocopherolon Serum and Colostrum Immunoglobulin G Titers and Preweaning Lamb Performance

Author: C.L. Schultz, T.T. Ross and M.W. Salisbury
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Abstract

Two experiments were conducted to examine effects of d-?-tocopherol (vitamin E) on colostrum immunoglobulin G (IgG) titers and preweaning lamb performance. Trial 1 consisted of 86 Suffolk ewes receiving either no vitamin E (control) or 1500 IU vitamin E on d-28 prepartum. From the 86 ewes, a subset of 25 ewes was randomly chosen for an intensive analysis of ewe serum and colostrum IgG and lamb serum IgG concentrations. Average daily gain was analyzed for lambs (n = 100) born to the 86 ewes as well as for lambs (n = 25) born to the subset of 25 ewes. Birth weights were also analyzed for the 25 lambs. Vitamin E supplementation had no effect on ewe serum (P = .16), lamb serum (P = .77) or ewe colostrum (P = .25) IgG concentrations. Of the intensively sampled lambs, those born to vitamin E-treated ewes had heavier (P = .08) birth weights and greater (P = .02) ADG than lambs born to control ewes. Average daily gain for lambs born to the 86 ewes was not affected by vitamin E (P = .97; n = 100). Trial 2 examined effects of vitamin E on lamb growth under range conditions. Two hundred whiteface, pregnant ewes were randomly sorted into four pastures with two pastures per treatment. Ewes received either no vitamin E (control) or 1500 IU vitamin E 40 d before the onset of lambing. Lambs from vitamin E-treated ewes showed higher weight gains at 30 d of age than lambs from control ewes (P = .03). However, weaning weights were similar (P > 0.10) for both treatment groups. Vitamin E does not appear to increase IgG concentrations in ewe and lamb serum or ewe colostrum. However, vitamin E showed positive effects on growth when lambs were under stress conditions during the first several weeks postpartum as indicated by intensively sampled lambs in Trial 1.

Comparing Indicators of Sheep Grazing Leafy Spurge and Perennial Grasses

Author: B.E. Olson and R.T. Wallander
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Abstract

Sheep and goats are increasingly being used to control the invasive leafy spurge (Euphorbia esula L.). Our objective was to compare three indicators of sheep use of leafy spurge and two native bunchgrasses, Idaho fescue (Festuca idahoensis Elmer) and bluebunch wheatgrass (Pseudoroegneria spi-cata [Scribn. and Smith] A. Love) on an upland site in southwestern Montana. We used yearling Targhee ewes in a 3 year study (1992-1994). One group of ewes (naive) had no previous exposure to leafy spurge whereas the second group (experienced) had been pastured on a leafy spurge-infested (25-50% cover) foothill rangeland as lambs. Sheep were rotated through 3 paddocks for 9 grazing periods in 1992 and 7 grazing periods in 1993 and 1994. Grazed plant frequency (%) and canopy removed (%) were estimated after sheep were removed from each paddock. Time spent grazing (%) on the different species was estimated for one week periods in early, mid-, and late summer 1992 and 1993, and at five day intervals for the first 35 days in the 1994 grazing season. Overall, the 3 measures of use indicated leafy spurge was less likely to be grazed than the two native grasses in early summer, but more likely to be grazed in mid-and late summer. In general, the sheep removed more of the canopy of leafy spurge than of grasses. During the early summer grazing period, all 3 measures of use indicated experienced sheep were more likely to graze leafy spurge than naive sheep. As expected, grazed plant frequencies were often high because any evidence of grazing was noted, whereas canopy removed more closely reflects ecological impacts of grazing. The behavioral time spent grazing results usually concurred with grazed plant frequency and canopy removed measured after sheep were removed from a given paddock.

Key words: weed, Euphorbia esula, grazing, nutritive value

Research Note - Repeated Injections of Pregnant Mare Serum Gonadotrophin (PMSG) Failed to Induce Antibody Production in Fall Lambing Ewes

Author: M.A. Diekman, M.K. Neary and G.R. Kelly
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Pregnant Mare Serum Gonadotrophin (PMSG) is commonly used to induce estrus/puberty or superovulate beef cows (Gonzalez et al., 1994), dairy cows (Kummer et al., 1980; Saumande et al., 1984), gilts or sows (Holtz and Schlieper, 1991) or ewes (Evans and Robinson, 1980; Jabbour and Evans, 1990). Across species, variation in the success of recovering viable ova or embryos following PMSG can be attributed to hormonal profiles postinjec-tion (Bevers and Dieleman, 1987), age of treated animal (Lerner et al., 1986) or day of the cycle on which treatment is administered (Moor et al., 1984). Reduction in time of activity of PMSG has been attempted by administering PMSG antibodies, but success has been variable (Kummer et al., 1980; Jabbor and Evans, 1990; Kirkwood etal., 1994). Another factor that diminishes the effectiveness of inducing ovulation is the number of superovulatory treatments to which an animal has been subjected (Christie et al., 1979; Moor et al., 1984). The objective of this study was to examine whether conception rate of ewes induced to ovulate out of season in successive years could be attributed to presence of circulating antibodies to PMSG.

Case Report - Monensin Poisoning in a Sheep Flock

Author: O. Mendes, F. Mohamed, T.Gull and A. de la Concha-Bermejillo
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An outbreak of monensin poisoning caused severe muscular dysfunction in sheep. Fifty-eight sheep from a flock of approximately 180 died. Affected animals had dark urine, stiff gait and/or intermittent recumbency. At necropsy, animals which died acutely had pale tan striations spread throughout the cardiac muscle. Similar, but less severe changes were seen in skeletal muscles including the diaphragm. In a lamb that survived longer, the myocardium and skeletal muscles presented larger, coales-cent, pale irregular areas. Histologically, muscle fibers were swollen and fragmented or had hyalinosis and loss of striation. Prominent satellite cell proliferation and mononuclear cell infiltration were evident in the muscles of chronically affected lambs. Toxicologic analysis revealed that the ration contained 334 ppm of monensin. In sheep, monensin toxicity occurs sporadically due to accidental or extra-label use. Differential diagnoses for cases of monensin toxicosis in sheep should include vitamin E and selenium deficiency, poisoning by myotoxic plants, and gossypol toxicity.