title: The composition of egg yolk absorbed by fasted ostrich (Struthio camelus L.) chicks from 1 to 7 days posthatching and for ostrich (Struthio camelus L.) chicks from 1 to 16 days posthatching on a prestarter broiler diet.
abstract: This study was performed to obtain information on yolk utilization in fasted and fed ostrich chicks posthatching. The fasted trial lasted for 7 d, whereas the fed trial continued for 16 d. Fasted ostrich chicks showed a decrease of 31.3 g of BW, with yolk weight decreasing by 28.9 g daily after hatching. Yolk weight comprised 28% of 1-d-old ostrich chick BW and decreased to 12% at 7 d of age. Only 44.4% of the fasted ostrich chick yolk was assimilated over the trial period. Crude protein content of the yolk decreased by 13.2 g daily. Fat content increased by 1.77% daily, whereas total yolk fat weight decreased with 8.91 g daily. Slaughter weight of fed ostrich chicks increased, with yolk weight decreasing by 16.3 g daily. Yolk content for fed ostrich chicks was 26% of BW at 2 d of age. Ostrich chicks absorb 30% of yolk over the first 4 d, 67% after 8 d, and only deplete the yolk after 14 d posthatch. Fasted ostrich chicks absorbed the yolk content at a rate of 28.9 g/d, compared with 22.3 g/d over the first 8 d and 16.3 g/d over the 16 d for fed ostrich chicks. The CP content of the yolk decreased by 6.84 g daily in fed ostrich chicks, whereas fat content of the yolk increased by 1.39% daily, although total yolk fat weight decreased by 6.61 g daily. Yolk weight and total CP decreased faster over the first 7 d in the fasted ostrich chicks compared with the fed ostrich chicks, which indicated that the decrease in yolk weight could be attributed to absorption of protein from the yolk. Fat content decreased faster over the first 8 d from the yolk of the fed ostrich chicks compared with that from the yolk of the fasted ostrich chicks, which could indicate that external feed has a positive influence on the absorption of fat from the yolk content.
authors.affiliation: Cape Institute for Agricultural Training, Elsenburg, Department of Agriculture, Western Cape, Private Bag X1, Elsenburg, 7607, South Africa. mariaanv@elsenburg.com
authors.forename: M
authors.initials: M
authors.lastname: Viljoen
authors.forename: T S
authors.initials: TS
authors.lastname: Brand
authors.forename: J T
authors.initials: JT
authors.lastname: Soley
authors.forename: E A
authors.initials: EA
authors.lastname: Boomker
mesh_terms: D000367:Age Factors; D000821:Animal Feed / Q000032:analysis; D000818:Animals; D004032:Diet; D005215:Fasting; D041981:Gastrointestinal Tract / Q000201:enzymology* / Q000254:growth & development*; D020310:Struthioniformes / Q000196:embryology / Q000254:growth & development*; D015017:Yolk Sac / Q000737:chemistry / Q000378:metabolism*