Effects Of Breeder Age Research Articles

Effect of breeder age and early hypoxic stimulation of the chorioallantoic membrane on vascularization, internal organ development, blood profile and chick organ histology

Effect of breeder age and early hypoxic stimulation of the chorioallantoic membrane on vascularization, internal organ development, blood profile and chick organ histology

Influence of breeders age on initial embryonic development (from 0 to 72 hours) of Japanese quails during incubation

The initial stages of early embryonic development were analyzed as a function of the incubation period and age of Japanese quail breeders. A total of 203 Japanese quails housed in 29 conventional laying cages with 5 females and 2 males at 31, 39, 48, and 59 weeks of age were used, and the fertile eggs from these breeders were selected and incubated. The eggs were opened, and the embryos were isolated, fixed in a glutaraldehyde solution, analyzed and classified according to the stage of development. For after laying and the incubation periods of 24, 48, and 72 hours, the embryos presented, on average, Hamburger-Hamilton stages XI, HH 6.1, HH 12.7, and HH 18.5, respectively, with no effect of breeder age. It was also observed that, between 31 and 59 weeks of age in Japanese quail breeders, the eggs become longer and wider, with greater weight, volume, and area. Therefore, it is concluded that the age of the Japanese quail mother influences the weight, length, width, volume, and area of the eggs but does not influence the embryonic development up to 72 hours.

Effects of breeder age and dietary methionine level on growth performance, carcass traits and breast meat properties of broiler chickens

Effects of breeder age and dietary methionine level on growth performance, carcass traits and breast meat properties of broiler chickens

The Effects of Breeder Age and Hatching Period on Fattening Performance and Carcass Characteristics in Geese

This study was carried out to determine the effects of breeding age and hatching period on fattening performance and slaughter characteristics in geese. For this purpose, were fattened 270 geese obtained from three different ages of geese breeder (one, two, three years old), and 54 of them were slaughtered at the age of 16 weeks to evaluate their carcass characteristics The values of 81.06, 94.15, and 93.37 g for hatching weights, 5275.27, 5590.25, and 5604.90 g for body weights at the 16th week, 24.57, 25.53, and 25.75 kg for total feed consumption and 3592.00, 3814.98, and 3850.6 g for warm carcass weight were determined in the evaluation of carcass characteristics of geese from obtained one, two and three years old breeder geese, respectively. The results of the present study suggested that breeder age had statistically significant effects on hatching weight (P<0.001), body weight (P<0.05), total feed consumption (P<0.01), warm and cold carcass weights (P<0.01). The hatching weights of 92.81 and 86.24 g, total feed consumption values of 24.91 and 25.66 kg, feed conversion ratios of 4.57 and 4.80 were calculated in the first and second periods. The difference in the hatching period was detected to have statistically significant effects on hatching weights (P<0.001), feed consumption (P<0.05), feed conversion ratio (P<0.01), and abdominal fat weights (P<0.001). In addition, it was suggested that seasonal variations could create differences in themselves depending on the stages of the growth and development process.

Effects of breeder age and short-term temperature stimulation during incubation on performance, organ weight, and carcass yield in male and female broilers

Birds develop thermoregulatory control during the last days of incubation. Different temperature conditioning programs have been proposed to prepare broiler chicks for post-hatch life. This study aimed to investigate the effects of short-term temperature (STT) stimulation and breeder age on hatching performance, embryo development, yolk absorption, and post-hatch performance of male and female broilers. A 2 × 2 factorial completely randomized design was used, with two breeder ages (30 and 60 wk), two temperature incubation programs (control and STT), and 2,520 eggs per treatment. Eggs were distributed in two large-scale commercial incubators with a capacity of 120,960 eggs. The control group was subjected to a standard single-stage incubation program (37.2-37.4 °C), whereas the STT group was subjected to a temperature increment of 1 °C for 4 h on embryonic days 16, 17, 18, and 19. Embryos were analyzed at 16 and 19 days of incubation, and chicks at hatch. At 19 days of incubation, STT conditioning resulted in lower yolk sac weight in embryos from 60-wk-old breeders and higher relative weight of the gastrointestinal tract in embryos from 30-wk-old breeders. At hatch, males had lower residual yolk weight, females had greater length, and chicks from 60-wk-old breeders subjected to STT had higher body weight and relative weight of the gastrointestinal tract. Eggs from 30-wk-old breeders showed higher fertility and hatchability and lower infertility, mortality, and second-grade chick percentages. Regarding performance, it was found that males had higher body weight from 7 to 42 days of age and higher whole leg yields. Females, on the other hand, had higher fat yields. Breeder age and sex influenced gastrointestinal tract development, carcass yield, and performance. A 1 °C increase in incubation temperature for 4 h from days 16 to 19 of incubation affected yolk absorption and digestive tract development in chicks from 60-wk-old breeders without, however, influencing performance results.

Effects of breeder age on embryonic development, hatching results, chick quality, and growing performance of the slow-growing genotype

The present study aimed to ascertain the effects of slow-growing breeder age on embryo development, incubation results, and chick quality and of the interaction between breeder age and hatching time on initial performance. A total of 630 hatching eggs obtained from a commercial flock of slow-growing broiler breeders (Isa Label Naked Neck) were evaluated in 2 experiments. The first experiment evaluated embryo development and hatching results for broiler breeder age treatments of 38 and 51 wk, whereas the second experiment evaluated broiler chick performance. For the second experiment, chicks were distributed in a 2 x 2 factorial randomized block (sex) experimental design consisting of 2 breeder ages (31 or 58 wk) and 2 hatching times (479–485 and 491–497 h). At 18 d of embryonic development, embryos of 51-wk-old breeders were larger than those of 38-wk-old breeders (P < 0.05), whereas yolk-free chick weight was similar (P > 0.05). Embryo organ weight was similar for the 2 breeder ages (P > 0.05); however, there was greater development of intestinal villi for embryos of the 51-wk-old breeders. There were no differences between breeder ages in hatchability and chick quality score (P > 0.05). Yolk-free chick weight at pulling was greater (P < 0.05) for chicks from 51-wk-old breeders. Hatching time did not affect performance from 1 to 7 d (P > 0.05); however, chicks hatching at 491–497 h had better performance from 1 to 28 d than did chicks hatching at 479–485 h (P < 0.05). In conclusion, the age of slow-growing breeders affects embryo villi development and chick weight but does not improve incubation results or chick quality. Chicks hatching later (491–497 h) had better performance results than chicks hatching earlier (479–485 h).

Sarı tüy rengindeki (Coturnix japonica) bıldırcınlarda farklı yaş ve depolama sürelerinin yumurta kalite özellikleri üzerine etkisi

Amaç: Sarı tüy renkli japon bıldırcınlarında 8, 12, 16, 20, 24, 28 ve 32 haftalık yaşlarda 7 ve 14 gün süreyle depolanan kuluçkalık yumurtaların iç ve dış kalite özellikleri araştırılmıştır.Yöntem ve Bulgular: Yaş ve depolama sürelerinin yumurtalarda dış ve iç kalite özellikleri üzerine etkisini belirme amacıyla 8-32 haftalar arasında 7 ayrı yaş dönemleri yumurtaların 0, 7 ve 14 gün süre ile depolanması araştırmanın yöntemini oluşturmaktadır. Yumurtanın depolama süresinin bağıl ağırlık kaybına etkili olduğu görülmüştür. Yumurta ağırlığı üzerine yaşın etkisi önemli bulunmuş, deneme başlangıcında (8. hafta) 11.67 g olan yumurta ağırlığı deneme sonunda (32. hafta) 12.15 g değerini almıştır Yumurta eninin yumurta boyuna oranı şeklinde ifade edilen şekil indeksi 8 haftalık yaşta en yüksek, 32 haftalık yaşta en düşük belirlenmiştir. Ak indeksi üzerine hayvan yaşı, depolama süresi ve yaş x depolama süresi arasındaki interaksiyon önemli bulunmuştur. Haugh birimi depolama süresi ve hayvan yaşından etkilenmiş, depolama süresi ile yaş arasındaki interaksiyon da etkili olmuştur. Depolama işlemi yapılmayan kontrol grubunda sarı indeks değeri, 7 ve 14 günlük depolama sürelerine göre daha düşük olup uygulamalar arası farklılık önemli bulunmuştur. Ak yüzdesi üzerine depolama süresi, yaş ve depolama süresi ile yaş arasındaki interaksiyon önemli olmuştur. Sarı yüzdesi depolama süresinden etkilenmemiş ancak yaşa bağlı olarak değişmiştir. Artan depolama süresine bağlı olarak sarı indeks değeri azalmıştır. Birim yüzey alanı başına kabuk ağırlığı depolama süresi ve hayvan yaşına göre değişmiştir. Gözenek sayısı üzerine hayvan yaşı etkili iken depolama süresinin etkisi önemsiz olmuştur.Genel Yorum: Sarı tüy rengindeki japon bıldırcınlarında yumurta iç ve dış kalite özellikleri üzerine anaç yaşı, depolama süresi ve çevresel faktörlerin etkisi önemli düzeyde bulunmuştur.Çalışmanın Önemi ve Etkisi: Elde edilen sonuçların gelecekte planlanacak çalışmalar için bilgi sağlayacağı beklenmektedir.

Effects of Breeder Age on Genetic Parameter Estimates of Slaughter and Carcass Traits in Japanese Quail

This study aimed to determine the phenotypic values of the slaughter and carcass traits in the flocks of quails obtained when a flock of parent quails were at 12, 16, and 20 weeks of age and to estimate the heritabilities and the genetic correlations for these traits. For this purpose, a total of 1,346 Japanese quails were slaughtered at 8 weeks of age, and their slaughter weights as well as carcass, breast, leg, and abdominal fat weights and ratios were determined. Differences in all traits were detected between female and male quails (P&lt;0.05). The averages of many important traits, primarily slaughter weight, carcass weight, and breast weight, increased with the increase in the breeder age. On the contrary, the carcass yield decreased (P&lt;0.05). There were no significant variations in the phenotypic and genetic variances for the slaughter and carcass traits in the flocks obtained when the breeder flock was at different ages. The heritabilities for slaughter weight, carcass weight, and abdominal fat weight were estimated to be moderate, and the genetic correlations among them were estimated to be positive and high. In conclusion, it is possible to state that positive results might be obtained by using the carcass ratio as the criterion for selection in quails. Besides, the breeder age was discovered to have had no significant effect on the genetic parameter estimations.

Effect of breeder age and storage conditions of Japanese quail eggs on hatchability, quail neonate quality, and Bursa of Fabricius characteristics

ABSTRACT Two experiments were conducted to evaluate combinations of different storage periods and temperature of hatching eggs of breeder quails in two stages of the production cycle (24 and 43 weeks) on hatchability, quail neonate quality, and Bursa of Fabricius characteristics. In each experiment, a total of 1.050 Japanese quail eggs were incubated in a randomized block design in a factorial arrangement of 2 × 5 × 2, with two breeder ages (24 and 43 weeks), five storage periods (one, [...]

Digestible Threonine Levels in the Starter Diet of Broilers Derived from Breeders of Different Ages

The aim of this study was to evaluate the effect of digestible threonine supplementation in the starter diet on the performance, intestinal parameters, and nutrient metabolism of broilers derived from breeders of different ages. In total, 480 one-day-old Cobb chicks, derived from 38-or 49-week-oldbreeders, were housed in experimental battery cages until 21 days of age and fed four different threonine levels (800, 900, 1,000, or 1,100 mg/kg) in the starter feed. A completely randomized experimental design in a 2x4 factorial arrangement (breeder age x threonine levels) was applied, totaling eight treatments with five replicates of 12 birds each. Broilers from older breeders fed 800 mg digestible threonine/kg of diet presented higher weight gain, with a positive linear effect. There was also an interaction between breeder age and threonine levels for the weight gain of 21-d-old broilers supplemented at maximum level of 1,003 mg Thr/kg diet during the starter phase. There was no effect of breeder age or threonine levels on nutrient metabolism during the period of 17-21 days. There was no influence of breeder age or threonine levels in the starter diet on intestinal morphometric measurements, absorption area, or percentage of goblet cells.

Efeitos da umidade relativa do ar na incubação e da idade da matriz leve sobre a eclodibilidade, qualidade dos pintos recém-eclodidos e desempenho da progênie

Objetivou-se avaliar os efeitos da umidade relativa do ar nas incubadoras (URI) e da idade da matriz leve sobre a eclodibilidade, qualidade dos pintos recém-eclodidos e o desempenho da progênie. Foram incubados 10.840 ovos, sendo os tratamentos definidos pela idade das matrizes Lohmann LSL(r) (26, 41 e 56 semanas) e pelos níveis de URI (48, 56 e 64%). Após a incubação, 1.620 pintos fêmeas foram alojados em galpão experimental convencional, de acordo com os tratamentos, até as 12 semanas de idade. Para a avaliação de eclodibilidade sobre ovos férteis e fêmeas refugos, o delineamento experimental foi em blocos ao acaso no arranjo em parcelas subdivididas. A parcela foi a URI (três níveis) e a subparcela foi a idade da matriz (três idades). Os blocos foram constituídos pelos andares dos carrinhos de incubação, em que cada andar continha uma repetição de cada idade da matriz. Os nove tratamentos foram constituídos por 14 repetições cada. As repetições foram bandejas de incubação, constituindo 1.204 ovos por tratamento. Para a avaliação do desempenho das frangas, o delineamento experimental foi inteiramente ao acaso, constituído por um esquema fatorial 3x3 (três níveis de URI e três idades), com seis repetições de 30 aves em cada tratamento. A eclodibilidade sobre ovos férteis foi maior (P&lt;0,05) com a utilização de 56% de umidade relativa do ar durante a incubação, independentemente da idade da matriz; e ovos de matrizes mais velhas (56 semanas) apresentaram eclodibilidade menor (P&lt;0,05), independentemente do nível de umidade relativa do ar no interior das incubadoras. Não foram constatados efeitos da idade da matriz e URI sobre o percentual de pintos refugos. A URI ou a idade da matriz leve não afetam o desempenho da progênie.

The effects of broiler breeder age on intestinal development during hatch window, chick quality and first week broiler performance

This study was carried out with the aim of determining the effects of breeder age on incubation results, intestinal development during hatch window, chick quality and first week broiler performance. A total of 4800 eggs were obtained from commercial Cobb 500 broiler breeder flocks at 33 and 62 weeks old. Of these 33 and 62 weeks old flocks, 31.4% and 7.0% were hatched 24 h before pull time and 51.2% and 56.0% were hatched 12 h before pull time, respectively. Hatchability of fertile eggs and hatchability of total eggs were found higher in 33 weeks old flock than the other. The chick hatch weight was determined as 39.5 g and 41.4 g in 33 and 62 weeks old flocks, respectively. Chick weight/initial egg weight rate was found to be higher as 67.3% in the 33 weeks old flocks. On hatching day, chick length were also higher in 62 weeks old flock. Relative yolk-free chick weight was higher in 33 weeks old (85.0%) flock than the other (82.0%). Intestine weight rate was higher as 5.27% in chicks from 33 weeks old than the other (5.08%). At 1 week of age, the body weights and weight gains were 165.1 g and 156.0 g, and 125.6 g and 114.6 g in 33 and 62 weeks old flocks, respectively. Higher mortality ratio as 3.6% was observed in 62 weeks old flock. In conclusion, intestinal development during hatch window, incubation parameters, chick quality and first week broiler performance is affected by breeder age.

Comparison of different chicken egg parameters in young and old cobb boiler breeders

The aim of this study was the comparative analysis of the chemical composition determined for 45 samples of eggs (white, yolk) from young and old hens of Cobb breeder at 31and 51 weeks of age. Research has been organized in hatchery unit with different age of hen egg production. Determination of gross chemical composition using specific methods in order to standards and regulations in force. Statistical analysis, revealed significant differences between the mean values calculated for albumin, yolk, samples derived from different age breeders. The eggshell, weights were differing significantly between Y and O group breeders. A sample of eggs was used for measurement of chemical composition in the yolk and albumen base on method of AOAC, 1990. There were significant difference (P 0.05) between Y and O group in Alb fat, Alb CP, Alb ash, yolk dry matter and yolk nitrogen free extract content, Although yolk dry matter and yolk nitrogen free extract content were decreased in O group compared to Y group numerically. In the present study, a significant effect of breeder age on AlbDM, Yolk fat was observed. This effect indicated that yolk from O group had the more fat content in compare with the Y group, 21.81g and 24.83 % respectively. There was significant differences (P<0.05) between Y and O group in Albumen, energy content, this result may be due to this fact that albumen weight is changed by aging in the egg so energy content of its increased in same manner.

Yolk sac fatty acid composition, yolk absorption, embryo development, and chick quality during incubation in eggs from young and old broiler breeders

The objective of the present study was to examine the changes in yolk and yolk sac fatty acid composition and also to investigate egg content, yolk absorption, embryo development during incubation, and chick quality at hatch in eggs from 36- and 52-wk-old broiler breeders. The fatty acid profiles of the yolk, the yolk sac of embryos, and the residual yolk sac of chicks were analyzed before incubation, on d 18, and at hatch, respectively. Yolk sac weight, and embryo weight and length were measured on d 18, and chick weight and length were measured at hatch. Egg weight, yolk and albumen weight, yolk percentage, and yolk:albumen ratio increased as breeder age increased, but the albumen percentage decreased. Yolk absorption in absolute value (g) was higher in embryos from the old flock on d 18 and at hatch. Relative yolk absorption was similar between age groups on d 18, whereas it was higher in the young flock at hatch. Breeder age affected the yolk sac weight and was higher in the old flock during incubation. Embryo or chick weight and length, and yolk-free BW were affected by breeder age during incubation. These parameters were higher in the old flock with a difference of 3.7 g, 0.8 cm, and 2.6 g, respectively, on d 18 and 7.4 g, 1.4 cm, and 6.3 g, respectively, at hatch compared with the young flock. The effect of breeder age on fatty acid composition differed significantly by sampling day. Palmitic, stearic, oleic, and linoleic acids were major fatty acids in the fresh yolk, ranging from 13.02 to 29.24%. These were followed by palmitoleic and arachidonic acids ranging from 1.24 to 7.04%, with the remaining fatty acids below 1%. Higher concentrations of myristic, palmitoleic, and oleic acids and lower concentrations of heptadeconoic, stearic, linoleic, and arachidonic acids were found in the residual yolk sac of the young flock than the old flock. The results showed preferentially selective absorption of some fatty acids by the embryo during incubation.

Effect of breeder age and slaughter weight on meat quality traits of broiler breast and leg meats

Effect of breeder age and slaughter weight on meat quality traits of broiler breast and leg meats

Effects of breeder age and egg weight on morphological changes in the small intestine of chicks during the hatch window

1. The objective of the study was to investigate the effects of breeder age and egg weight on hatching performance and morphological changes in segments of the small intestine of broiler chicks during a 21 h hatch window.2. Eggs from Ross broiler breeder flocks aged 29 (young) and 48 weeks (old) were classified as light (LE) or heavy (HE) and incubated at the same conditions. At 475 h of incubation, eggs were checked every 3 h to determine time of external pipping and hatching. The first 42 chicks to emerge from each group were weighed and chick length was measured and 14 chicks from each group were sampled to collect residual yolk and intestine segments. The rest of chicks were placed back in the incubator and chick weight and length were measured individually at 9, 15 and 21 h after chicks hatched. At the end of 21 h, 14 chicks from each group were sampled again and the same procedure was followed.3. The HE chicks pipped and hatched later than LE, regardless of breeder age. From hatch to the end of the hatch window, chick weight, but not yolk-free chick weight, gradually reduced. Relative residual yolk weight of chicks from both egg weights was similar at hatch, however, yolk sac utilisation was higher for LE chicks during the 21 h post-hatch period. At hatch, jejunum and ileum villus development was very similar for HE and LE chicks but greater development was observed for villus area with an increase in the jejunum villus length, width and goblet cell numbers in HE chicks.4. The longest jejunum villus and the widest duodenum and jejunum villus were obtained for HE chicks from old breeders indicating that HE chicks from old breeders would have a greater surface area for nutrient absorption.

Reproductive characteristics of a captive colony of big-eared climbing rats (Ototylomys phyllotis)

The authors analyzed the breeding characteristics of a colony of Ototylomys phyllotis (big-eared climbing rat) from Campeche, México, that was bred in captivity for 6 y. The big-eared climbing rat is a reservoir of Leishmania (Leishmania) mexicana, a causal agent of localized cutaneous leishmaniasis on the Yucatán Peninsula. The colony had been established to facilitate studies analyzing the effectiveness of O. phyllotis as an experimental model for L. (L.) mexicana. The authors describe the housing and husbandry of the colony, the procedures used for mating the animals and the behavior of the animals during mating. They report that the animals showed social behavior and could be bred successfully. Most breeding pairs successfully produced litters; some pairs produced more than one litter. The authors also report data for other parameters, such as the interval between pairing and birth or between births of consecutive litters, litter size, survival to weaning, the timing of sexual maturity and the effects of breeder age on breeding success.

Breeder age and bone development in broiler chicken embryos

The effect of breeder age on long bone development was studied in chicken embryos from 12 days of incubation until hatching. Fertile eggs were incubated and randomly assigned in a 2 x 6 factorial arrangement (two breeder ages - 38 and 60 weeks and six incubation days - 12, 14, 16, 18, 20, and 21). Enzymatic activity of acid and alkaline phosphatases in tibial epiphyses and weights as well as length and width in tibias and femurs of the embryos were determined. Tartrate-resistant acid and alkaline phosphatases activity in epiphyses was not affected by breeder age. Absolute weight and width of femur and tibia were larger in 60-week-old embryos compared to 38-week-old. Enzymatic activity and morphometric measurements increased with incubation day, independently of breeder age. The results showed that the process of endochondral ossification during the last two thirds of embryo development was not influenced by the age of the breeders. Although, in terms of absolute weight, the long bones of embryos from older breeders were heavier, which was associated with the larger width of the bones, but and not with their length.

INTERAÇÃO ENTRE IDADE DA MATRIZ E PESO DO OVO NO DESEMPENHO DE FRANGOS DE CORTE

Existem vários fatores que podem afetar o desempenho e rendimento dos frangos de corte, independentemente dos níveis nutricionais utilizados nas dietas, como a idade da matriz e o peso do ovo. Neste trabalho, foram avaliados os possíveis efeitos que a idade da matriz e o peso do ovo à incubação exercem sobre o desempenho zootécnico e rendimento de carcaça de frangos de corte. As aves foram distribuídas em um delineamento experimental inteiramente casualizado em esquema fatorial 3 x 3 (ovos provenientes de matrizes de 3 diferentes idades: 30, 48 e 60 semanas, e de 3 categorias de pesos: leves, médios e pesados). As variáveis analisadas foram consumo de ração, ganho de peso e conversão alimentar aos 7, 21, 35 e 42 dias e rendimento de carcaça (rendimento de peito, pernas e gordura abdominal) aos 42 dias de idade. Não houve interação significativa entre os fatores idade da matriz e peso do ovo. Frangos provenientes de matrizes jovens (30 semanas de idade) apresentaram piores resultados de consumo de ração, ganho de peso e conversão alimentar à primeira semana de idade, sendo que este efeito não se mantém até a idade de abate. Houve maior consumo de ração de frangos provenientes de ovos pesados aos 7 dias de idade. Conclui-se que não existe interação entre idade da matriz e peso dos ovos sobre desempenho zootécnico e rendimento de carcaça em frangos de corte.

The Effect of Breeder Age and Egg Storage Time on Phosphorus Utilization by Broiler Progeny Fed a Phosphorus Deficiency Diet with 1α-OH Vitamin D3

Two experiments were conducted to determine that variation in broiler P utilization is due to breeder age and egg storage time. Experiment 1 was conducted with chicks hatched from eggs laid by Ross × Ross 308 breeders (27 vs. 61 wk old) and stored for 0 or 10 d. The age of breeders had significant effects (P < 0.05) on 0 to 16 d chick growth (379 ± 18 vs. 308 ± 19 for 27- and 61-wk-old breeders, respectively). The longer egg storage time of chicks from older breeders resulted in higher P rickets scores and incidence, but longer egg storage time of chicks from younger breeders resulted in lower P rickets score and incidence (significant interaction, P = 0.0455). The longer egg storage time of chicks from older breeders resulted in lower bone ash (%), and the longer egg storage time of chicks from younger breeders resulted in higher bone ash (%). Experiment 2 was conducted with chicks hatched from eggs laid by Ross × Ross 308 breeders (26 vs. 60 wk old) and stored for 0 or 10 d. The diets were P deficient and with or without 5 μg/g of 1α–OH cholecalciferol (1α-OH vitamin D3). Breeder age had significant effects (P = 0.0003) on 0 to 16 d chick growth (272 ± 7 vs. 339 ± 8 for 26- and 60-wk-old breeders, respectively) and chick mortality (P = 0.0134). The P rickets score increased with breeder age (P = 0.0186) and egg storage time (P = 0.1057). The factors influencing the incidence of P rickets in broilers should include breeder age and egg storage time as well as genetics and dietary levels of Ca, P, and vitamin D activity of the P-deficient diets.