E L Walker

University of Missouri, Columbia, Missouri, United States

Are you E L Walker?

Claim your profile

Publications (4)6.32 Total impact

  • E.L. Walker · S.A. Nusz · D.H. Keisler · M.A. Brown ·

  • Source
    N C Whitley · D J O'Brien · R W Quinn · D H Keisler · E L Walker · M A Brown ·
    [Show abstract] [Hide abstract]
    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.
    Journal of Animal Science 01/2009; 87(5):1659-63. DOI:10.2527/jas.2008-1568 · 2.11 Impact Factor
  • [Show abstract] [Hide abstract]
    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.
    Journal of Animal Science 01/2006; 83(12):2752-61. · 2.11 Impact Factor
  • Source
    N C Whitley · E L Walker · S A Harley · D H Keisler · D J Jackson ·
    [Show abstract] [Hide abstract]
    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.
    Journal of Animal Science 08/2005; 83(8):1854-9. · 2.11 Impact Factor
  • E.L. Walker · S.A. Nusz · D.H. Keisler · M.A. Brown ·