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RESUMO -Um experimento foi conduzido com o objetivo de avaliar os efeitos de duas fontes de vitamina D e três níveis de vitamina C sobre as características de desempenho, a qualidade interna e externa dos ovos, os níveis de cálcio total e iônico séricos e a resistência óssea de poedeiras. Foram utilizadas 288 galinhas da linhagem ISA Babcock B300 ® com 23 semanas de idade, durante um período experimental de 12 semanas. Utilizou-se o delineamento inteiramente ao acaso em arranjo Vitamins D and C for laying hens at the initial phase of egg production ABSTRACT -An experiment was conducted to evaluate the influence of two vitamin D sources and three vitamin C levels on performance, internal and external egg quality, and bone strength characteristics. In addition, the total and ionic blood calcium concentrations, bone ash and calcium were determined. Two hundred and eighty eight 23-week-old ISA Babcock B-300 ® laying hens were used during the 12-week study in a 2 × 3 factorial arrangement: vitamin D sources (cholecalciferol and 25-hydroxycholecalciferol -25(OH)D 3 ) and vitamin C levels (0, 100 and 200 ppm) resulting in six treatments with eight replicates of six hens each. The basal cholecalciferol level was 2,756 IU/kg, corresponding to 5.51 g Hy.D ® /t, as source of 25(OH)D 3 . Feed intake, egg production, egg weight and egg mass were not influenced by the treatments. An interaction was observed for feed conversion, which was improved when 25(OH)D 3 was added without vitamin C. Haugh unit and yolk index were not influenced, however, interactions were observed for albumen percent and yolk percent, which were improved when 200 ppm of vitamin C was supplemented. Egg specific gravity, serum calcium, bone ash and bone strength resistance were not influenced by the treatments. There was an interaction for shell percent and shell thickness, which were improved when vitamin C was added in association with 25(OH)D 3 . It was concluded, for laying hens at initial phase of egg production, that feed conversion is improved when 25(OH)D 3 was the vitamin D source, and that shell thickness and shell percent are improved when the vitamin D source was 25(OH)D 3 with diets supplemented with vitamin C (100 or 200 ppm, respectively).Key Words: ascorbic acid, bone strength, egg quality, performance, vitamin D IntroduçãoA obtenção de bons índices zootécnicos de desempenho e qualidade externa dos ovos geralmente resulta em sucesso para o setor produtivo de ovos comerciais. Reconhece-se que a idade é determinante do desempenho e da qualidade interna e externa dos ovos (Faria et al., 1999a). Estima-se que a incidência de ovos quebrados R. Bras.

This study was carried out to evaluate the performance and internal and external egg qualities of white commercial laying hens fed diets with different calcium levels and limestone particle sizes. Two hundred seventy ISA-Babcock B-300N hens, 40 weeks of age, were used by four-28 days period. The experimental design was randomly in a 3x3 factorial arrangement: calcium fractionation (2g Ca morning + 2g Ca afternoon, 1g Ca morning + 3g Ca afternoon, 3g Ca morning + 1g Ca afternoon) and limestone particle size (blended, coarse and fine) with a total of nine treatments with five replicates of six hens each. Performance characteristics were not influenced by the treatments, except feed intake and calcium intake. It was observed higher calcium and feed intake for hens fed 3g Ca in the morning. Also, in the afternoon was verified higher calcium and feed intake for hens fed 3g Ca. There was no effect of the treatments on total daily intake. The limestone particle size improved egg specific gravity when blended or coarse particle size was benefical to eggshell quality. The calcium fractionation did not show be adventageous. However, further researches are indicate to evaluate other nutrients fractionation as phosphorus, energy, and protein.

RESUMO. Avaliou-se o desempenho e a qualidade dos ovos de poedeiras submetidas ao fracionamento de cálcio (Ca) da dieta e diferentes granulometrias de calcário calcítico. Foram utilizadas 270 poedeiras ISA Babcock, com 40 semanas, por quatro períodos de 28 dias, em um delineamento inteiramente casualizado em arranjo fatorial 3x3: fracionamento do Ca -g manhã:g tarde (2:2; 1:3 e 3:1) e granulometria do calcário calcítico (mista, grossa e fina), com cinco repetições de seis aves cada. As aves alimentadas com 3 g de Ca, de manhã ou à tarde, consumiram mais ração e Ca no entanto, o consumo total diário de Ca não foi influenciado. O calcário fino influenciou negativamente a qualidade da casca. Conclui-se que o fracionamento de cálcio não influenciou os parâmetros estudados e que utilizar calcário fino prejudica a qualidade da casca dos ovos.Palavras-chave: alimentação, aves, minerais, nutrição, tamanho de partícula de calcário.ABSTRACT. Effects of dietary calcium fractionation and limestone particle size on performance and egg quality of commercial laying hens. The performance and egg quality of 270 ISA Babcock layers, aged 40 weeks, fed diets with different calcium (Ca) levels and limestone particle size were evaluated. The experimental design was randomized in a 3x3 factorial scheme: Ca fractionation -g morning : g afternoon (2:2, 1:3 and 3:1) and limestone particle size (coarse, fine and blended) totalizing nine treatments with five replications of six hens each. Performance was not influenced by the treatments, except feed and Ca intakes. Hens fed with 3:3g Ca, in the morning or in the afternoon, had higher Ca and feed intake. However, there was no effect on daily total Ca intake. Egg specific gravity was improved when hens were fed with coarse and blended limestones. Results showed that Ca fractionation did not influence performance and egg shell quality. Egg specific gravity is improved when hens are fed with coarse and blended limestones.Key words: feeding, poultry, minerals, nutrition, limestone particle size. IntroduçãoO contínuo melhoramento genético das linhagens comerciais tem resultado em aves cada vez mais produtivas e, por outro lado, mais exigentes quanto aos aspectos de manejo, sanidade, ambiência e nutrição. Nesse contexto, a qualidade da casca dos ovos torna-se um fator que preocupa os produtores, já que as perdas econômicas decorrentes de danos causados à casca resultam em depreciação e perdas de produto por presença de trincas, deformidades e irregularidades na deposição de casca.Cerca de 10% do peso do ovo é composto pela casca, sendo que 98% da mesma é formada por carbonato de cálcio, dos quais 60% constituídos por carbonato e 38% por cálcio (Etches, 1995). A poedeira necessita consumir diariamente cerca de 4 gramas de cálcio, considerando-se que somente cerca de 50% a 60% do cálcio dietário é utilizado no processo de formação da casca. Quando a glândula da casca (útero) está inativa, sem a presença do ovo, a absorção de cálcio pelo intestino é em torno de 40%. Todavia, quando a mesma está ativ...