E L Walker

Missouri State University, Springfield, Missouri, United States

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Publications (6)7.81 Total impact

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    E.L. Walker · S.A. Nusz · D.H. Keisler · M.A. Brown
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    ABSTRACT: Bermudagrass (Cynodon dactylon) is a high quality, abundant warm-season grass grown in temperate regions of the United States. While research data exists to support protein supplementation of steers grazing bermudagrass pastures, no such data exists for management of lambs and meat goat kids. The objective was to evaluate growth response of lambs and meat goat kids grazing bermudagrass with or without access to a commercial 21% CF protein tub (PT vs. NPT). Two trials were conducted in El Reno, Oklahoma, starting in June and ending in August in 2007 and 2008. In 2007 and 2008, respectively 29 and 54 meat goat kids (90 +/- 5 days of age) and 68 and 62 lambs of wool and hair breeds (and reciprocal crosses; 100 +/- 15 days of age) were utilized. Animals were stratified by weight, breed and gender and randomly assigned to 1.2 ha of common bermudagrass pasture with (n = 2) or without (n = 2) access to a commercial 21% CP protein tub. Growth of animals was assessed by change in body weights and serum concentrations of leptin every 2 weeks during grazing periods of 71 days for 2007 and 56 days for 2008. Sheep had greater ADO than goats (p<0.05) and breeds of sheep differed in ADO (p <= 0.05). Ad libitum protein supplementation tubs had no effect on ADO or serum leptin of either lambs or kids grazing bermudagrass. These data do not support the need for protein supplementation of lambs and meat goat kids grazing bermudagrass.
    Full-text · Article · Dec 2011 · Journal of Animal and Veterinary Advances
  • C. T. MacKown · M. A. Brown · E. L. Walker
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    ABSTRACT: Gastrointestinal nematode (GIN) resistance to synthetic anthelmintics in small ruminants has led to the evaluation of feed sources containing naturally occurring bioactive secondary metabolites that lessen parasite activity. Plants rich in condensed tannins (CT) can have beneficial anthelmintic properties. Peanut (Arachis hypogea L.) skins (testa), an agricultural by-product, are a rich source of CT, have low fiber and high levels of oil and crude protein, and have been incorporated into feed products for the cattle industry. Anthelmintic activity of pellets formulated with peanut skins was compared to that of commercial alfalfa (Medicago sativa L.) pellets (control diet) fed to lambs in two separate experiments, one with initially low (220eggsg−1feces; 2008) and the other high (4260eggsg−1feces; 2009) burden of GIN. In both experiments lambs were maintained on bermudagrass (Cynodon dactyon (L.) Pers.) pastures except when pellets were fed (six lambs per treatment) at 2.3% BW every other day three times a week. Overall, average daily intake of CT as quebracho (Schinopsis sp.) equivalents of peanut skin pellets formulated with 5% molasses was 0.38% BW (low GIN lambs), and that of peanut skin pellets formulated with 48% alfalfa and 7% molasses was 0.53% BW (high GIN lambs). Regardless of the initial level of GIN burden and the formulation of the peanut skin pellets, average daily weight gain of all lambs was about 94±7.2g per day. Increases in fecal egg count and decreases in blood packed cell volumes that occurred during the trials were not significantly different (P>0.05) between lambs fed the control alfalfa pellets and lambs fed peanut skin containing pellets. In these trials, intake of peanut skin may have been insufficient to decrease GIN parasite activity, or perhaps the low prodelphinidin subunit composition of CT in peanut skin prevented a beneficial response.
    No preview · Article · Apr 2011 · Small Ruminant Research
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    ABSTRACT: Twenty-one mixed-parity (average 2.4 +/- 0.49) crossbred sows and their offspring were used to determine whether sow milk leptin at farrowing was related to neonatal serum leptin and pig growth to weaning. During farrowing, pigs were randomly allotted to suckling (n = 99) or delayed suckling (n = 89) groups, with delayed suckling pigs placed in a group pen apart from the dam before suckling. Both groups had access to heat lamps. Colostrum samples were collected no more than 2 h after farrowing the first pig. Blood samples were collected from all pigs approximately 2 h after farrowing was complete; pigs were then ear notched and returned to their dams. Pig BW was recorded at 1.2 +/- 0.04 d of age and again at weaning. Milk and blood serum were collected after centrifugation; leptin concentrations were estimated using RIA. Leptin was detected in colostral milk, as expected, and averaged 46.0 +/- 1.1 ng/mL. Pig serum leptin (P < 0.02) was greater in suckling pigs than in delayed suckling pigs, averaging 0.69 +/- 0.08 and 0.54 +/- 0.07 ng/mL, respectively. Although male pigs were heavier (P < 0.01) at birth than female pigs (1,507 +/- 52 vs. 1,381 +/- 43 g), ADG to weaning and weaning weights were similar for both sexes, averaging 229 +/- 14 g and 5,829 +/- 323 g, respectively, for all pigs; serum leptin concentrations were not affected by sex of the pig. Milk serum leptin was not associated with litter size, parity, pig birth weight, ADG to weaning, or weaning weight. Suckling status did not influence ADG to weaning or weaning weight of pigs; neonatal pig serum leptin was not related to birth weight, weaning weight, or ADG to weaning. These results indicate that leptin is not directly related to early neonatal growth in the pig; however, more in-depth studies are needed to determine possible indirect or long-term effects of early leptin exposure.
    Full-text · Article · Jan 2009 · Journal of Animal Science
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    ABSTRACT: One hundred forty spring-born Angus x Gelbvieh and purebred Angus steers were selected for study as early weaned (EW; average age at weaning = 90 +/- 30 d) or traditionally weaned (TW; average age at weaning = 174 +/- 37 d) steers that were non-implanted or implanted (Synovex-S, Fort Dodge Animal Health, Overland Park, KS). Initially, steers were sorted by age, sire, and farm, and then allotted randomly in a 2 x 2 factorial arrangement of treatments of EW implanted (EWI), EW nonimplanted (EWN), TW implanted (TWI), or TW nonimplanted (TWN). Ultrasound measurements (US) of LM area (LMA), 12th rib fat thickness (US-BF), and marbling (US-M) were collected every 28 d during the time that steers were on feed. At 202 d of age, EW calves had larger US-LMA, US-BF, and BW than TW calves (37.9 vs. 32.3 cm2, 0.38 vs. 0.26 cm, and 271.6 vs. 218.9 kg, respectively; P < 0.001). At slaughter, EW calves had heavier HCW (290.4 vs. 279.7 kg, respectively; P < 0.05) and greater USDA marbling scores (51.25 vs. 46.26, respectively; P < 0.05) than TW calves; more EW steers graded USDA Choice or greater (P = 0.05). However, no differences were detected in BW (P = 0.15), LMA (P = 0.39), BF (P = 0.45), or liver abscess scores (P = 0.41). Twenty-four implanted steers were selected from the original group of 140 and sorted into two slaughter groups of 12. Twelve implanted steers from each weaning group, matched in slaughter BW but differing in age, were subsampled at slaughter to assess the effect of weaning age and chronological age on muscle tenderness. Younger animals had lower Warner-Bratzler shear force values (P < 0.001) than older calves after 14 d of postmortem aging; however, no differences were found in tenderness after 21 d of aging. Furthermore, there was greater variance (P < 0.001) in Warner-Bratzler shear force values among younger, EW steers vs. older, TW steers. These data provide evidence that early weaning of beef calves may be used as a tool to more effectively manage the cow-calf production system without compromising the quality of the offspring.
    No preview · Article · Jan 2006 · Journal of Animal Science
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    N C Whitley · E L Walker · SA Harley · D H Keisler · D J Jackson
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    ABSTRACT: Boer and Boer crossbred meat-type does were used in two experiments to determine whether goat milk serum contains leptin and to investigate possible correlations of milk and serum leptin in does and subsequent growth of their offspring. Blood and milk samples were collected within 2 h of kidding (d 0) from 20 (Exp. 1; spring) or 22 does (Exp. 2; the following fall). Blood milk samples were then collected again on d 0.5, 1, 3, 5, 7, 14, 21, 28, 35, 42, 49, and 56 (Exp. 1) or d 0.5, 1, 2, 3, 4, 5, 6, 7, 14, and 21 (Exp. 2). Body weights of kids were recorded on d 0, and BW of kids and does were recorded weekly beginning on d 7 (kids) or 21 (does), with BCS also recorded for does beginning on d 28 for Exp. 1 and on d 0.5, 1, 2, 3, 4, 5, 6, 7, 14, and 21 for Exp. 2. Leptin was detected in colostral milk and was influenced by days postpartum, decreasing (P < 0.001) over time with an average of 4.4 +/- 0.3 ng/mL (Exp. 1) and 18.1 +/- 1.0 ng/mL (Exp. 2) on d 0 compared with 1.0 +/- 0.3 ng/mL on d 56 (Exp. 1) and 2.9 +/- 0.2 ng/mL on d 21 (Exp. 2). Day postpartum and milk serum leptin were negatively correlated (P < 0.001) for Exp. 1 (r = -0.27) and Exp. 2 (r = -0.46). For Exp. 1 only, blood serum leptin tended (P = 0.09) to be influenced by day, with a weak positive correlation (r = 0.15; P < 0.02). Weak positive correlations (P < 0.01) were found between blood serum leptin and doe BCS (r = 0.42 in Exp. 1, and r = 0.13 in Exp. 2) and doe BW (r = 0.44 in Exp. 1, and r = 0.26 in Exp. 2), with the absence of a stronger relationship likely due in part to the short time period measured and the lack of significant changes in BCS and BW during that time. In conclusion, leptin was present in milk and blood serum of does, and blood serum leptin was weakly correlated with doe BW and BCS, but it was not related to kid BW. Therefore, further studies are needed to clarify the relationships involving milk and serum leptin in goats.
    Full-text · Article · Aug 2005 · Journal of Animal Science
  • E.L. Walker · S.A. Nusz · D.H. Keisler · M.A. Brown

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