Growing broilers on wire flooring provides an excellent experimental model for exposing susceptibility to lameness attributable to bacterial chondronecrosis with osteomyelitis (BCO). Two independent experiments (E1, E2) were designed to compare the susceptibilities of broilers from 4 commercial crosses (W, X, Y, and Z). The standard crosses (W and Y) grow rapidly at an early age, whereas high-yield crosses (X and Z) initially tend to grow more slowly. Chicks were obtained from a commercial hatchery for E1, or were hatched at the University of Arkansas Poultry Research Hatchery for E2. Males and females were reared together (E1; n = 360/cross) or separately (E2; n = 390/cross) in 3 × 3 m pens on litter or wire flooring (wire). Necropsies revealed lesions that were pathognomonic for BCO in ≥94% of the birds that became lame. The SigmaStat Z-test was used to compare cumulative lameness incidences at 8 wk of age. For birds reared on litter, lameness incidences were low and did not differ between crosses or sexes (range: 2.2 to 4.6%; P ≥ 0.6). When males were reared on wire, their lameness incidences (by cross) were E1 = 52% for W(b); 42% for X(c); 69% for Y(a), and 44% for Z(bc); E2 = 31% for W(b); 19% for X(c); 49% for Y(a); and 25% for Z(bc). For females reared on wire, the lameness incidences were E1 = 40% for W(b), 30% for X(c), 49% for Y(a), and 28% for Z(c); E2 = 16% for W; 15% for X; 16% for Y; and 15% for Z (ns). Accordingly, the hierarchical ranking for BCO susceptibility by broiler cross was X ≤ Z ≤ W < Y for males in E1 and E2, for females in E1, and for males and females pooled in E1 and E2. Standard broiler crosses developed higher incidences of lameness than high-yield crosses, implicating an association between rapid early growth and susceptibility to BCO. Rearing the females separately on wire in E2 led to uniformly low incidences of BCO, regardless of cross. Stress-mediated immunosuppression contributes to the pathogenesis of BCO; perhaps female broilers experience less social or competitive stress when reared separately from their male hatch mates.

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Most CLA chicken feeding trials used cis,trans (c,t) and trans,cis (t,c) CLA isomers to produce CLA-rich eggs, while reports of trans,trans (t,t) CLA enrichment in egg yolks are limited. The CLA yolk fatty acid profile changes and the 10-12 days of feeding needed for maximum CLA are well documented, but there is no information describing CLA accumulation during initial feed administration. In addition, no information on CLA accumulation rates in different hen strains is available. The aim of this study was to determine a mathematical model that described yolk CLA accumulation and depletion in three hen strains by using t,t CLA-rich soybean oil produced by photoisomerization. Diets of 30-week Leghorns, broilers, and jungle fowl were supplemented with 15% CLA-rich soy oil for 16 days, and eggs were collected for 32 days. Yolk fatty acid profiles were measured by GC-FID. CLA accumulation and depletion was modeled by both quadratic and piecewise regression analysis. A strong quadratic model was proposed, but it was not as effective as piecewise regression in describing CLA accumulation and depletion. Broiler hen eggs contained the greatest concentration of CLA at 3.2 mol/100 g egg yolk, then jungle fowl at 2.9 mol CLA, and Leghorns at 2.3 mol CLA. The t,t CLA isomer levels remained at 55% of total yolk CLA during CLA feeding. However, t-10,c-12 (t,c) CLA concentration increased slightly during CLA accumulation and was significantly greater than c-9,t-11 CLA. Jungle fowl had the smallest increase in yolk saturated fat with CLA yolk accumulation.

Rearing broilers on flat or sloping wire flooring is an effective method for consistently triggering lameness attributable to bacterial chondronecrosis with osteomyelitis (BCO). Portable obstacles known as speed bumps (SB) also consistently trigger modest incidences of BCO when they are installed between feed and water lines in litter flooring facilities. Two experiments were conducted to determine the most effective broiler age for introducing the SB into litter flooring pens, and to evaluate alternative configurations of the traditional SB with the expectation that amplified mechanical challenges to the legs of broilers should increase the incidence of BCO. Broiler chicks obtained from commercial hatcheries (lines B and D in experiment 1, lines A and B in experiment 2) were reared in floor pens with ad libitum feed and water and a 23L:1D photoperiod. In experiment 1, the 5 floor treatments included wood shavings litter only (L), flat wire only (W), or litter plus SB installed at 14, 28, or 42 d of age. Line B was more susceptible to lameness than line D (25.9 vs. 15.3% for all treatments combined; P = 0.001). Both lines developed low incidences of lameness on L (11 to 13%), intermediate incidences on SB regardless of day of installation (12 to 23%), and high incidences on W (21 to 39%). In experiment 2, broilers were reared with 7 floor treatments, including L, W, SB with a 50% slope (SB50%); SB50% with a limbo bar installed over the apex; SB with a 66% slope and limbo bar; SB50% with a nipple water line suspended over the apex; and a pagoda-top SB. All SB were inserted on d 28. Line B was more susceptible to lameness than line A (20.2 vs. 16.1% for all treatments combined; P < 0.05), and for both lines combined the lameness percentages averaged 7.7 (L), 29.2 (W), 17.3 (SB50%), 16.2 (SB50% with a limbo bar), 21.5 (SB with a 66% slope and limbo bar), 20.8 (SB50% with a nipple water line), and 11.5% (pagoda-top). These studies demonstrate the portable SB can be effectively used to experimentally trigger BCO in broilers.