Abstract
The effect of cholecalciferol (D3) and 25-hydroxycholecalciferol (25-OHD3) as isolated or associated sources of vitamin D (100%-0%, 75%-25%, 50%-50%, 25%-75%, 0%-100%) on the productive performance, egg quality, and bone characteristics was evaluated in white egg-laying hens fed two levels of calcium (Ca) and phosphorus (P) in the basal diet (BD) (BD1 = 0.38% Ca - 0.36% available P and BD2 = 3.2% Ca - 0.30% available P). Nine hundred and sixty Dekalb White hens (24 weeks old) were distributed into 80 cages, under a completely randomized factorial design for 16 weeks. The use of associated sources of vitamin D reduced the feed intake and feed conversion ratio, as well as BD1, which also increased the egg production and egg mass. The association of vitamin D sources with up to 50% 25-OHD3 increased the eggshell percentage. There was interaction (p<0.05) between the sources of vitamin D and the concentrations of Ca and available P, sources with at least 50% 25-OHD3 increased ash percentage and bone radiographic densitometry (BRD) with BD1; in BD2 the use of 25-OHD3 as isolated vitamin D source increased BRD. The association of D3 and 25-OHD3 improved the productive performance, increased the percentage of eggshell and had different positive effects on the bone characteristics that depend on the concentrations of Ca and available P in the balanced feed of white egg-laying hens.
Highlights
The high incidence of bone problems associated with osteoporosis in egg-laying hens housed in the battery position has generated concern in the scientific community about animal welfare associated with this production system (Rath et al, 2000)
Brito et al (2010), who determined that the combined use of these same sources of vitamin D improves the productive performance of broiler chickens in all phases of production
Hernández et al (2001), used 2750 IU/kg D3 to meet the vitamin D requirements of egg-laying hens and supplemented with 2760 IU/kg 25-OHD3 without observing effects on the productive performance of the assessed birds.The studies mentioned above used higher levels of vitamin D, which is necessary for further testing of the association between sources at various levels of dietary supplementation
Summary
The high incidence of bone problems associated with osteoporosis in egg-laying hens housed in the battery position has generated concern in the scientific community about animal welfare associated with this production system (Rath et al, 2000). Problems with egg shell quality generate millions in losses to the poultry industry; it is important to understand the factors that affect the internal and external quality of the egg (Roberts, 2004). Bone structure and egg shell quality are influenced by environmental, handling, and nutritional factors (Nys, 1999). In addition to other functions, may be the most significant factor in eggshell formation and proper maintenance of the bone structure, considering this mineral constitutes 40% of the eggshell (Keshavarz, 2003) and that hydroxyapatite in bones constitutes 99% of the total Ca in the body of a bird (Johnston; Ivey 2002). Agrotec., Lavras, v.38, n.6, p.573-580, nov./dez., 2014
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