title: Modeling ovarian follicle growth in commercial and heritage Single Comb White Leghorn hens.
abstract: Approximately 84% of the energy in chicken eggs resides in the yolk. A robust model of ovarian follicle development is therefore valuable for estimating energy requirements of laying hens. The current experiment was designed to model the growth of ovarian follicles in 32-wk-old modern commercial line (CL) and unselected heritage line (HL) Single Comb White Leghorn hens. The volume of yolk deposited daily during the rapid growth phase (RGP) was estimated using a double dye technique. For 21 d, 8 CL and 8 HL hens were fed capsules (no. 1) containing Sudan IV (red) and Sudan Black dyes on alternate days. An additional 8 control CL hens were fed empty capsules. Eggs were collected, and the daily volume of yolk deposited was estimated. Significant differences are reported where P < 0.05. Dye had no significant effect on BW, ME intake, or egg weight. Maintenance ME requirements were 192 and 177 kcal/kg(0.67) for CL and HL hens, respectively. Duration of the RGP was shorter (7.35 d) in the CL hens compared with the HL hens (7.95 d). A nonlinear Lomolino model described follicular weight, which varied between strains over d 2 to 9 of follicle development; at each day during development, follicle weights were higher where RGP were shorter. The volume of yolk deposited for the 8 d preceding oviposition in CL was 0.17, 0.28, 0.43, 0.99, 1.84, 2.47, 2.82, 2.86, and 2.51 cm(3); and in HL was 0.17, 0.33, 0.72, 1.40, 2.15, 2.46, 2.48, 2.32, and 1.93 cm(3). The HL had a higher rate of yolk deposition 7 to 5 d before oviposition, and CL had a higher rate of yolk deposition 3 to 1 d before oviposition with no significant difference between lines on d 4 before oviposition. Although growth patterns differed, there were no differences among lines in final follicle weights (14.1 g) or retained energy (42.4 kcal).
authors.affiliation: Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada T6G 2P5.
authors.forename: E S
authors.initials: ES
authors.lastname: McLeod
authors.affiliation: Department of Animal Production, Faculty of Agriculture, University of Jordan, Amman, 11942, Jordan.
authors.forename: M A
authors.initials: MA
authors.lastname: Jalal
authors.affiliation: Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada T6G 2P5 martin.zuidhof@ualberta.ca.
authors.forename: M J
authors.initials: MJ
authors.lastname: Zuidhof
mesh_terms: D000818:Animals; D002645:Chickens / Q000254:growth & development*; D005260:Female; D008954:Models, Biological; D006080:Ovarian Follicle / Q000254:growth & development*; D013045:Species Specificity
keywords: dye ring; energy requirement; laying hen; nonlinear growth model; ovarian follicle growth