title: Influence of chick hatch time and access to feed on broiler muscle development.
abstract: The effect of hatch time and the timing of access to feed on growth rate and breast muscle development was assessed in Ross 308 broiler chickens. Chicks were removed from the incubator upon hatching, and classified as early (EH), midterm (MH), or late (LH) hatchers, based on the duration of their incubation. Feed and water were available either immediately at hatch, or 24 h after the conclusion of the hatch period. Hatchling body weight was uniform regardless of hatch time. Subsequently, bodyweight was increased in EH compared to LH birds following immediate access to feed, until 7 d in female, and 14 d in male birds. Relative breast weight was increased until 28 d in birds with immediate access to feed, and also EH and MH birds regardless of access to feed. Pectoralis major muscle morphology and expression of the myogenic regulatory factors myogenic determination factor 1 (MYOD1) and myogenin, and the proteoglycans syndecan-4, glypican-1, and decorin were measured. Myogenin and glypican-1 stimulate satellite cell (SC) differentiation. Glypican-1 expression was unaffected by treatment. A late increase in myogenin expression was observed in MH birds with delayed access to feed, and all LH birds. Syndecan-4 and MYOD1, expressed in proliferating SC, and decorin, which stimulates satellite cell proliferation and differentiation, were variably upregulated in the first wk posthatch in the same birds. These data suggest SC were activated and proliferating, but had reduced differentiation in later hatching and feed deprived birds. Conversely, EH birds with immediate access to feed had maximal myofiber width at 7 d, while fiber width was increased in birds with immediate access to feed compared to those with delayed access to feed through 40 d of age. These results demonstrate that delaying chick access to feed for 24 h upon removal from the incubator will impair muscle growth. Additionally, hatch time influences muscle development, with accelerated muscle growth in EH and MH, compared to LH birds, irrespective of access to feed.
authors.affiliation: Faculty of Veterinary Science, The University of Sydney, Camden, NSW 2750, Australia Poultry CRC, PO Box U242, University of New England, Armidale, NSW 2351, Australia dpow1086@uni.sydney.edu.au.
authors.forename: D J
authors.initials: DJ
authors.lastname: Powell
authors.affiliation: Department of Animal Sciences, The Ohio State University/Ohio Agricultural Research and Development Center, Wooster 44691.
authors.forename: S G
authors.initials: SG
authors.lastname: Velleman
authors.affiliation: Faculty of Veterinary Science, The University of Sydney, Camden, NSW 2750, Australia.
authors.forename: A J
authors.initials: AJ
authors.lastname: Cowieson
authors.affiliation: Faculty of Veterinary Science, The University of Sydney, Camden, NSW 2750, Australia.
authors.forename: M
authors.initials: M
authors.lastname: Singh
authors.affiliation: Faculty of Veterinary Science, The University of Sydney, Camden, NSW 2750, Australia.
authors.forename: W I
authors.initials: WI
authors.lastname: Muir
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D030161:Avian Proteins / Q000235:genetics / Q000378:metabolism; D002645:Chickens / Q000254:growth & development / Q000502:physiology*; D005247:Feeding Behavior; D005260:Female; D015870:Gene Expression; D008297:Male; D024510:Muscle Development; D010369:Pectoralis Muscles / Q000254:growth & development*; D013997:Time Factors
chemical_list: D030161:Avian Proteins
keywords: Hatch time; adult myoblast; myogenic regulatory factor; posthatch feed