Beneficial Impact of Hypercapnic Conditions During Early Incubation on Broiler Hatchability. Embryo Mortality and Postnatal Performance

We assessed the extent to which CO2 levels altered different hatching and chick parameters. In Experiments 1 and 2, a total of 16,184 eggs from Cobb 500 breeders were incubated in single stage incubators under three different conditions: (a) standard ventilated incubator (CON, Exp.1 and 2); (b) increasing CO2 levels during the first 10 days of incubation until 0.7% (V7000, Exp. 1) and (c) until 0.8% (V8000, Exp. 2). High levels of CO2 improved hatchability, possibly due to lower embryo mortality from ED18 to ED21. Internal and external pipping in experiment V8000 started later than in CON; nevertheless, the hatch still occurred before in V8000 as a result of the shorter durations of external pipping and hatch. In Experiment 3, a total of 12,138 eggs from Cobb 500 were incubated in single stage incubators under three different conditions: (a) standard ventilated incubator (CON); (b) increasing CO2 levels until 1.0% with ventilation (V10000); and (c) increasing CO2 levels until 1.0% without ventilation (NV10000). Hypercapnic conditions led to better hatchability and lower embryo mortality from ED18 to ED21. Internal pipping started earlier in NV10000, but only V10000 differed from CON in terms of the average time for hatch. Hypercapnic groups also showed shorter durations of external pipping and hatch when compared to CON. Post-hatch analysis revealed no differences among incubation conditions in terms of body weight gain, feed conversion ratio, mortality by sudden death syndrome, and production factor. Nevertheless, V10000 showed a lower mortality by ascites and a better viability when compared to CON, while NV10000 presented a higher mortality by other causes. Altogether, our findings indicate that in addition to not being detrimental to embryo survival, high CO2 levels reduce embryonic mortality at 18-21 days of incubation and increase hatchability.(AU)

Effect of Egg Weight and Patio Strategies on Hatching Traits and Subsequent Performance of the Broilers

Objectives of the present study were to assess the hatchery based interventions and their impact on hatching traits and subsequent performance of broilers. In total, 3000 eggs of Hubbard broiler breeders were equally divided into Small (50-55 g), Medium (56-61 g) and Large (62-70 g) eggs. The eggs from each category were distributed into 20 trays each containing 50 eggs. Each tray was considered as a replicate. At the end of the 18th day of incubation, the eggs of each weight category were divided into four different patio strategies i.e. P0, P3, P5 and P7 where feed and water were provided to the chicks for 0, 3, 5 and 7 days in the hatcher followed by conventional rearing. Data were collected for hatch window, hatching traits, growth, physical asymmetry, welfare and blood profile in broilers. Statistical analysis showed that the smaller eggs had significantly (P 0.05) shorter hatch window compared to larger and medium eggs. Hatching traits were significantly (p 0.05) better in medium eggs but the embryonic mortalities did not differ (p>0.05). The post-hatch performance was significantly (p 0.05) better in P3 birds from medium eggs. Physical asymmetry and scores of feather and gait were not affected by both treatments (p>0.05). Blood profile was also significantly (p 0.05) better in P3 birds from medium-size eggs. It was recommended that the eggs of 56-61g should be selected for better hatchability and the chicks should be provided with feed and water within the hatcher for at-least three days for optimum performance on rearing facility.(AU)

Effect of Egg Weight and Patio Strategies on Hatching Traits and Subsequent Performance of the Broilers

Objectives of the present study were to assess the hatchery based interventions and their impact on hatching traits and subsequent performance of broilers. In total, 3000 eggs of Hubbard broiler breeders were equally divided into Small (50-55 g), Medium (56-61 g) and Large (62-70 g) eggs. The eggs from each category were distributed into 20 trays each containing 50 eggs. Each tray was considered as a replicate. At the end of the 18th day of incubation, the eggs of each weight category were divided into four different patio strategies i.e. P0, P3, P5 and P7 where feed and water were provided to the chicks for 0, 3, 5 and 7 days in the hatcher followed by conventional rearing. Data were collected for hatch window, hatching traits, growth, physical asymmetry, welfare and blood profile in broilers. Statistical analysis showed that the smaller eggs had significantly (P 0.05) shorter hatch window compared to larger and medium eggs. Hatching traits were significantly (p 0.05) better in medium eggs but the embryonic mortalities did not differ (p>0.05). The post-hatch performance was significantly (p 0.05) better in P3 birds from medium eggs. Physical asymmetry and scores of feather and gait were not affected by both treatments (p>0.05). Blood profile was also significantly (p 0.05) better in P3 birds from medium-size eggs. It was recommended that the eggs of 56-61g should be selected for better hatchability and the chicks should be provided with feed and water within the hatcher for at-least three days for optimum performance on rearing facility.

Embryonic mortality and broiler chick quality (Gallus gallus) from glass-shelled eggs / Mortalidade embrionária e qualidade do pinto ao nascer oriundo de ovo de casca vítrea de matriz pesada (Gallus gallus)

The glass-shelled egg has various points on the surface with light gray coloration, which becomes more visible with the passage of egg storage period. The objective of this work was to evaluate the stage of embryonic mortality, egg weight during the incubation period, hatch window, and quality of chicks at hatch from glass-shelled egg. The research was divided into two parts. In the first part, 80 eggs from 45 weeks old hens were incubated, being half normal eggs and half glass-shelled eggs, while in the second part, 80 eggs from 70 weeks old hens from the same flock as the previous one were incubated. Again, half were normal shelled and half were glass-shelled eggs. No differences were observed for embryonic mortality, egg weight, hatch quality (hatch weight, uniformity, and navel quality), and hatch window between normal and glass-shelled eggs from hens of 45 and 70 weeks of age. However, there was higher contamination in glass-shelled egg from 70-week-old breeder hens. The results show that the presence of glass-shelled egg does not seem to interfere with the quality of the chick at hatch in the breed, ages, and studied conditions, but causes higher contamination in glass-shelled egg from 70-week-old breeder hens.

Ovos de casca vítrea apresentam em suas superfícies pontos com coloração cinza claro de vários diâmetros, que ficam mais visíveis com o decorrer do período de armazenagem. Objetivou-se no trabalho, avaliar a fase de mortalidade embrionária, peso do ovo durante o período de incubação, intervalo de tempo de nascimento e a qualidade dos pintos ao nascerem oriundos de ovos de casca vítrea. A pesquisa foi dividida em duas partes. Na primeira parte, ocorreu a incubação de 80 ovos provenientes de matrizes com 45 semanas de idade sendo metade ovos normais e metade ovos vítreos e na segunda parte, foram incubados 80 ovos provenientes de matrizes com 70 semanas de idade do mesmo lote do anterior. Desses, metade eram normais e metade eram vítreos. Não houve diferença para mortalidade embrionária, peso do ovo, qualidade dos pintos ao nascerem (peso do pinto ao nascer, qualidade do umbigo e uniformidade) e intervalo de tempo de nascimento entre os ovos vítreos e normais oriundos de matrizes de 45 e 70 semanas de idade. Porém ovos de casca vítrea oriundos de matrizes de 70 semanas de idade apresentaram maior índice de contaminação.

Embryonic mortality and broiler chick quality (Gallus gallus) from glass-shelled eggs / Mortalidade embrionária e qualidade do pinto ao nascer oriundo de ovo de casca vítrea de matriz pesada (Gallus gallus)

The glass-shelled egg has various points on the surface with light gray coloration, which becomes more visible with the passage of egg storage period. The objective of this work was to evaluate the stage of embryonic mortality, egg weight during the incubation period, hatch window, and quality of chicks at hatch from glass-shelled egg. The research was divided into two parts. In the first part, 80 eggs from 45 weeks old hens were incubated, being half normal eggs and half glass-shelled eggs, while in the second part, 80 eggs from 70 weeks old hens from the same flock as the previous one were incubated. Again, half were normal shelled and half were glass-shelled eggs. No differences were observed for embryonic mortality, egg weight, hatch quality (hatch weight, uniformity, and navel quality), and hatch window between normal and glass-shelled eggs from hens of 45 and 70 weeks of age. However, there was higher contamination in glass-shelled egg from 70-week-old breeder hens. The results show that the presence of glass-shelled egg does not seem to interfere with the quality of the chick at hatch in the breed, ages, and studied conditions, but causes higher contamination in glass-shelled egg from 70-week-old breeder hens.(AU)

Ovos de casca vítrea apresentam em suas superfícies pontos com coloração cinza claro de vários diâmetros, que ficam mais visíveis com o decorrer do período de armazenagem. Objetivou-se no trabalho, avaliar a fase de mortalidade embrionária, peso do ovo durante o período de incubação, intervalo de tempo de nascimento e a qualidade dos pintos ao nascerem oriundos de ovos de casca vítrea. A pesquisa foi dividida em duas partes. Na primeira parte, ocorreu a incubação de 80 ovos provenientes de matrizes com 45 semanas de idade sendo metade ovos normais e metade ovos vítreos e na segunda parte, foram incubados 80 ovos provenientes de matrizes com 70 semanas de idade do mesmo lote do anterior. Desses, metade eram normais e metade eram vítreos. Não houve diferença para mortalidade embrionária, peso do ovo, qualidade dos pintos ao nascerem (peso do pinto ao nascer, qualidade do umbigo e uniformidade) e intervalo de tempo de nascimento entre os ovos vítreos e normais oriundos de matrizes de 45 e 70 semanas de idade. Porém ovos de casca vítrea oriundos de matrizes de 70 semanas de idade apresentaram maior índice de contaminação.(AU)

Development of digestive organs of female broilers under varying post-hatch fasting times / Desenvolvimento dos órgãos digestórios de frangos de corte fêmea submetidos a diferentes períodos de jejum pós-eclosão

This study aimed to evaluate the effect of post-hatch fasting time on the weights of body and digestive organs of chicks. Fertile eggs from 62-week-old broiler breeders (Cobb Fast lineage) were incubated and, after hatching, female chicks were randomly divided into six treatments, which corresponded to fasting periods (0, 6, 12, 24, 48, and 72 hours), with 40 chicks per treatment. At 01, 03, 06, and 10 days after hatching, measurements of body weight; residual yolk weight; relative weights of proventriculus + gizzard, intestine + pancreas and liver; and intestine total length were made. At 6 days of age, the chicks submitted to post-hatch fasting, for up to 12 hours, demonstrated greater development, with body weights higher than the other birds. Yet, when fed, no compensatory gain was observed and, at 10 days of age, the birds submitted to 48- and 72-h fasting remained with a lower body development. Intestine growth was also compromised by post-hatch fasting, being reduced in both weight and length. A post-hatching fasting of up to 24 hours did not interfere with the weights of body and digestive organs of 10-day-old female broiler chickens. However, 48- and 72-h post-hatch fastings affected adversely the weight and growth of digestive organs in the birds.

O efeito dos períodos de jejum pós-eclosão foi avaliado sobre o peso inicial das aves e de seus órgãosdigestórios. Ovos férteis de matrizes de frango de corte (linhagem Cobb Fast) de 62 semanas de idadeforam incubados e após a eclosão os pintinhos (fêmeas) foram divididos em seis tratamentos de 40aves cada, correspondentes a tempos diferentes de jejum (0, 6, 12, 24, 48 e 72 horas). Com 1, 3, 6e 10 dias de idade, o peso corporal das aves e do vitelo residual, pesos relativos do proventrículo +moela, intestino + pâncreas, fígado, e o comprimento total do intestino foram analisados. Aos 6 dias deidade, os animais que foram submetidos ao jejum pós-eclosão de até 12 horas demonstraram melhordesenvolvimento com maior peso corporal em relação aos demais. Essas aves não apresentaram ganhocompensatório quando alimentadas; no entanto, aos 10 dias de idade, os animais submetidos a 48 e72 horas de jejum, permaneceram com menor desenvolvimento corporal. O crescimento do intestinotambém foi comprometido em função do jejum pós-eclosão, com redução de comprimento e peso. Ojejum pós-eclosão de até 24 horas não afetou o peso corporal e o peso de órgãos digestórios em fêmeas de frango de corte criadas até 10 dias. Já jejum de 48 e 72 horas afeta de forma negativa o peso corporal e o crescimento dos órgãos digestórios.

Development of digestive organs of female broilers under varying post-hatch fasting times / Desenvolvimento dos órgãos digestórios de frangos de corte fêmea submetidos a diferentes períodos de jejum pós-eclosão

This study aimed to evaluate the effect of post-hatch fasting time on the weights of body and digestive organs of chicks. Fertile eggs from 62-week-old broiler breeders (Cobb Fast lineage) were incubated and, after hatching, female chicks were randomly divided into six treatments, which corresponded to fasting periods (0, 6, 12, 24, 48, and 72 hours), with 40 chicks per treatment. At 01, 03, 06, and 10 days after hatching, measurements of body weight; residual yolk weight; relative weights of proventriculus + gizzard, intestine + pancreas and liver; and intestine total length were made. At 6 days of age, the chicks submitted to post-hatch fasting, for up to 12 hours, demonstrated greater development, with body weights higher than the other birds. Yet, when fed, no compensatory gain was observed and, at 10 days of age, the birds submitted to 48- and 72-h fasting remained with a lower body development. Intestine growth was also compromised by post-hatch fasting, being reduced in both weight and length. A post-hatching fasting of up to 24 hours did not interfere with the weights of body and digestive organs of 10-day-old female broiler chickens. However, 48- and 72-h post-hatch fastings affected adversely the weight and growth of digestive organs in the birds.(AU)

O efeito dos períodos de jejum pós-eclosão foi avaliado sobre o peso inicial das aves e de seus órgãosdigestórios. Ovos férteis de matrizes de frango de corte (linhagem Cobb Fast) de 62 semanas de idadeforam incubados e após a eclosão os pintinhos (fêmeas) foram divididos em seis tratamentos de 40aves cada, correspondentes a tempos diferentes de jejum (0, 6, 12, 24, 48 e 72 horas). Com 1, 3, 6e 10 dias de idade, o peso corporal das aves e do vitelo residual, pesos relativos do proventrículo +moela, intestino + pâncreas, fígado, e o comprimento total do intestino foram analisados. Aos 6 dias deidade, os animais que foram submetidos ao jejum pós-eclosão de até 12 horas demonstraram melhordesenvolvimento com maior peso corporal em relação aos demais. Essas aves não apresentaram ganhocompensatório quando alimentadas; no entanto, aos 10 dias de idade, os animais submetidos a 48 e72 horas de jejum, permaneceram com menor desenvolvimento corporal. O crescimento do intestinotambém foi comprometido em função do jejum pós-eclosão, com redução de comprimento e peso. Ojejum pós-eclosão de até 24 horas não afetou o peso corporal e o peso de órgãos digestórios em fêmeas de frango de corte criadas até 10 dias. Já jejum de 48 e 72 horas afeta de forma negativa o peso corporal e o crescimento dos órgãos digestórios.(AU)

Effect of incubator type and broiler breeder age on hatchability and chick quality

Two experiments were conducted to evaluate the effect of broiler breeder age and incubator type on hatching parameters, hatch window, embryo diagnosis results, and hatchling physical quality. The treatments consisted of a combination of three broiler breeder ages (29, 35 and 59 weeks of age) and two incubator types (single stage, SS; or and multiple stage, MS). A completely randomized design in a 3x2 factorial arrangement was applied. In Experiment I, 1,896 eggs were used and 360 eggs in Experiment II. There was an interaction between breeder age and incubator type only for hatchling physical quality score. Independently of incubator type, hatchability rate, late embryo mortality, and egg contamination were higher in the eggs laid by older breeders (59-wk-old). Early mortality (0-4 days) was higher in the embryos from young breeders (29-wk-old). A shorter hatch window birth was obtained in the SS incubator, resulting in higher hatchling body weight relative to egg weight, and better hatchling physical quality score. Both types of incubators provide good conditions for embryo development; however, the physical quality of chicks derived from eggs from intermediate-aged breeders (35-wk-old) is better when eggs are incubated in SS incubators.

Effect of incubator type and broiler breeder age on hatchability and chick quality

Two experiments were conducted to evaluate the effect of broiler breeder age and incubator type on hatching parameters, hatch window, embryo diagnosis results, and hatchling physical quality. The treatments consisted of a combination of three broiler breeder ages (29, 35 and 59 weeks of age) and two incubator types (single stage, SS; or and multiple stage, MS). A completely randomized design in a 3x2 factorial arrangement was applied. In Experiment I, 1,896 eggs were used and 360 eggs in Experiment II. There was an interaction between breeder age and incubator type only for hatchling physical quality score. Independently of incubator type, hatchability rate, late embryo mortality, and egg contamination were higher in the eggs laid by older breeders (59-wk-old). Early mortality (0-4 days) was higher in the embryos from young breeders (29-wk-old). A shorter hatch window birth was obtained in the SS incubator, resulting in higher hatchling body weight relative to egg weight, and better hatchling physical quality score. Both types of incubators provide good conditions for embryo development; however, the physical quality of chicks derived from eggs from intermediate-aged breeders (35-wk-old) is better when eggs are incubated in SS incubators.(AU)

INFLUÊNCIA DA FOTOESTIMULAÇÃO NA DINÂMICA DE NASCIMENTOS E CARACTERÍSTICAS INTESTINAIS DE PINTOS DE CORTE

O presente trabalho está organizado em 4 Capítulos. O Capítulo 1 apresenta a Introdução e as Considerações Gerais sobre o tema estudado. No Capítulo 2, foi analisado se fotoestimulação intermitente (1 min de luz seguido de 4 minutos de escuro, durante 12 h, das 6:30 às 18:30h, 1200 Lux fornecido por sistema em série de lâmpadas LED) no nascedouro, a partir do 18º dia de incubação, influencia a eclodibilidade, a frequência de nascimentos e a qualidade dos pintos de corte. Os resultados mostram que fotoestimulação intermitente a partir do 18º dia de incubação não alterou a duração média da incubação, eclodibilidade e a qualidade física dos pintos, mas reduziu a janela de eclosão em 8h. Além disso, pintos de ovos mantidos sob fotoestimulação intermitente apresentaram menor TIT que os pintos de ovos incubados sem fotoestimulação. Isso indicou que fotoestimulação intermitente no nascedouro aumenta o sincronismo na eclosão e torna os pintos mais ativos. No Capítulo 3, foram analisadas a dinâmica de nascimentos diurnas e noturnas e a qualidade dos pintos de ovos expostos ou não a fotoestimulação intermitente (1 min de luz seguido de 4 minutos de escuro, durante 12 h, das 6 às 18h, 1200 Lux fornecido por sistema em série de lâmpadas LED) a partir do 18º dia de incubação (no nascedouro). Não ocorreram diferenças na taxa de eclosão total, peso corporal, qualidade, peso corporal, comprimentos bico-cauda, bico-dedo médio e de perna, e envergadura de asas entre os pintos com nascimento diurno e noturno e nem entre tratamentos (com e sem fotoestimulação). Os resultados revelam, pela primeira vez na literatura, descontinuidade de eclosão, diferenças entre os padrões de eclosão diurna e noturna de pintos de corte e menor janela de eclosão com maior sincronismo de eclosão noturna do que diurna em pintos corte, evidenciando possibilidade futura de manejo pratico de retirada diurna e noturna de pintos dos nascedouros. No Capítulo 4, por sua vez, foi analisado se fotoestimulação diurna ou noturna contínua (250 Lux ao nível da superfície dos ovos, durante 12 h, das 6 às 18h e das 18 às 6h) influencia o desenvolvimento da mucosa intestinal de pintos de corte. Os resultados evidenciam que o fornecimento do fotoestimulação durante a incubação reduz temperatura de superfície dos ovos quando expostos a fotoestimulação durante a noite. Os pintos nascidos de ovos incubados sob fotoestimulação apresentaram vilosidades intestinais menores do que os pintos oriundos de ovos incubados sem fotoestimulação. Isso indica que fotoestimulação diurna ou noturna durante a incubação não favoreceu o desenvolvimento das vilosidades intestinais e que incubação sob ausência de luz parece mais adequado para que os pintos nasçam com vilosidade intestinal de maior tamanho.

This work is organized into 4 Chapters. Chapter 1 presents the Introduction and General Considerations on the topic studied. In Chapter 2, we analyzed whether intermittent photostimulation (1 min of light followed by 4 minutes of dark, for 12 h, from 6:30 to 18:30 h, 1200 Lux provided by LED lamp series system) in the hatch, from the 18th day of incubation, influences hatchability, birth frequency and quality of broiler chicks. The results show that intermittent photostimulation from the 18th day of incubation did not change the mean duration of incubation, hatchability and physical quality of the chicks, but reduced the hatch window by 8h. Furthermore, chicks from eggs kept under intermittent photostimulation showed lower TIT than chicks from eggs incubated without photostimulation. This indicated that intermittent photostimulation at the hatcher increases hatch timing and makes the chicks more active. In Chapter 3, the dynamics of diurnal and nocturnal births and the quality of chicks from eggs exposed or not to intermittent photostimulation (1 min of light followed by 4 minutes of dark, for 12 h, from 6 am to 6 pm, 1200 Lux provided by a series system of LED lamps) from the 18th day of incubation (in the hatcher). There were no differences in total hatch rate, body weight, quality, body weight, beak-tail, beak-middle finger and leg lengths, and wing span between day and night chicks, nor between treatments (with and without photostimulation). The results reveal, for the first time in the literature, hatch discontinuity, differences between the diurnal and nocturnal hatching patterns of broiler chicks and a shorter hatch window with greater synchronism of nocturnal hatching than diurnal hatching in broiler chicks, evidencing the possibility of future management. practice of day and night withdrawal of chicks from hatchers. In Chapter 4, in turn, it was analyzed whether continuous diurnal or nocturnal photostimulation (250 Lux at the egg surface level, for 12 h, from 6 am to 6 pm and from 6 pm to 6 am) influences the development of the intestinal mucosa of broiler chicks. The results show that providing photostimulation during incubation reduces the surface temperature of eggs when exposed to photostimulation overnight. Chicks hatched from eggs hatched under photostimulation had smaller intestinal villi than chicks hatched from eggs hatched without photostimulation. This indicates that diurnal or nocturnal photostimulation during incubation did not favor the development of intestinal villi and that incubation in the absence of light seems more suitable for chicks to be born with larger intestinal villi.

CARACTERÍSTICAS FÍSICAS DOS OVOS E DOS PINTOS DE CORTE SOBRE O PERÍODO DE NASCIMENTO E QUALIDADE DENTRO DA JANELA DE ECLOSÃO

Eclodibilidade e qualidade dos pintos e duração da incubação são importantes no processo de incubação de ovos, e podem ser influenciados pelas características físicas dos ovos. No Capítulo 1 é apresentada uma abordagem teórica sobre o tema. No Capítulo 2 foi analisado a qualidade incubatória de ovos leves e pesados de matrizes de corte, dentro do intervalo de peso de ovo comercialmente incubável, considerando a dinâmica de nascimentos, a eclodibilidade e a qualidade geral dos pintos e ao longo da janela de eclosão, considerando incubação dos ovos até 504h (padrão dos incubatórios) e 529h (real). Para isso, ovos férteis com 56-61g (leves) e com 65-71g (pesados) de matrizes de corte Cobb foram incubados a 37,5ºC e 60% de UR, com giro a cada hora. Pintos e ovos foram analisados de acordo com o período de nascimento (precoce, intermediário e tardio: 472-485h, 485-512h e 512,5-529h de incubação, respectivamente), em ambos os pesos de ovos. Os resultados mostraram eclodibilidade similar para ovos leves e pesados até 504h e até 529h (65,8% e 86,7%; 70,7% e 87,9%; respectivamente), e aumentou de 17% e 20%, respectivamente, de 504h para 529h. Ovos pesados apresentaram janela de eclosão mais curta (2,5h para 504h de incubação e 6,6h para 529h de incubação) e maior concentração de nascimentos de pintos intermediários que os ovos leves. Pintos de ovos leves apresentaram melhor qualidade devido à menor incidência de problemas de alantoide e atividade. Pintos precoces de ovos leves apresentaram a melhor qualidade comparada aos demais pintos do mesmo peso de ovo e aos pintos dos ovos pesados. De acordo com os resultados, ovos leves apresentam maior qualidade incubatória no que se refere à qualidade dos pintos, enquanto os ovos pesados apresentam maior qualidade incubatória quando se considera janela de eclosão e sincronismo na eclosão. Tais resultados mostram que aumento da produção de pintos precoces deve ser meta a ser alcançada pelos incubatórios. No Capítulo 3, foi estudado se características físicas dos pintos e dos ovos (leves e pesados) determinam o período de nascimento de pintos dentro da janela natural de eclosão. Para isso foi adotado o mesmo protocolo de incubação e delineamento experimental utilizado no Capítulo 2. Os resultados mostraram que pintos precoces apresentam maior tamanho de bico e são provenientes de ovos com maior tamanho de câmara de ar. Tais resultados mostram, pela primeira vez na literatura, relação do período de nascimento dos pintos dentro da janela de eclosão com o tamanho da câmara de ar e do bico. Eles sugerem a possibilidade do tamanho do bico ser levado em consideração em futuros estudos de seleção genética para aumentar a produção de pintos precoces, o que parece interessante uma vez que há a possibilidade de aves com maior tamanho de bico apresentarem maior ingestão de alimentos e, consequentemente, menor período de crescimento.

Hatchability and chick quality, and incubation duration are important for the egg incubation process, and they may to be influenced by physical characteristics of the eggs. Chapter 1 presents a theorical approach on this theme. Chapter 2 compared the quality for incubation of light and heavy eggs from broiler breeders, within the egg weight interval recommended for incubation based on birth dynamics, hatchability, and general quality of the chicks and chick quality throughout hatch window until 504h and 529h. For this, fertile light (56-61g) and heavy (65-71g) eggs from broiler breeders were incubated at usual conditions (37.5ºC, 60% RH, egg turning each hour until 18º day). Physical characteristics of eggs and chicks were analyzed according to birth period (early, intermediate and later: 472-485h, 485-512h e 512.5-529h of incubation, respectively). The results showed similar hatchability for light and heavy eggs until 504h and 529h (65.8% and 86.7%; 70.7% and 87.9%; respectively), as well as a 17% and 20% increase in the hatchability, respectively, from 504h to 529h. Heavy eggs presented a shorter hatch window and a higher rate of intermediate chicks compared to light eggs. Chicks from light eggs had better quality compared to other chicks due to low occurrence of alantoic cord and low activity. Thus, light eggs presented better quality for incubation resulting of better chick quality, whereas heavy eggs had good quality for incubation because their short hatch window and simultaneous higher hatch synchronism. These results show higher production of early chicks should be preconized by hatcheries. In Chapter 3, the relation of the physical characteristics of the eggs and newly hatched chicks with the birth period within the hatch window was analyzed. The egg incubation was realized following the same procedure used in Chapter 2. Early chicks had longer beak and hatched from eggs containing larger air chamber than intermediate and later chicks. These results show, by the first time in the literature, a relation between incubation duration and beak and air chamber size. They suggest beak length should be considered in genetic selection studies to increase the production of earlier chicks, and this is very interesting once broilers presenting greater beak size may have higher feed intake and, consequently, shorter growth period before slaughter.