Resistance and tolerance to mixed nematode infections in relation to performance level in laying hens.

Modern chickens have been genetically developed to perform high under optimal conditions. We hypothesized that high-performance is associated with a higher sensitivity to environmental challenges in laying hens. By using nematode infections as an environmental stressor, we assessed performance-level associated host responses in a high (i.e. Lohmann Brown Plus, LB) and in a lower performing, a so-called dual-purpose chicken genotype (i.e. Lohmann Dual, LD). The hens were infected with 1000 eggs of Ascaridia galli and Heterakis gallinarum at 24 weeks of age. Hen performance parameters, humoral immune responses in plasma and egg yolks and worm burdens were assessed at several occasions over a period of 18 weeks post infection (wpi). While infections had no significant effect on feed intake (P = 0.130) and body weight in both genotypes (P = 0.392), feed conversion efficiency was negatively affected by infections (P = 0.017). Infections reduced both laying rate and egg weight and thereby per capita egg mass in both genotypes (P < 0.05). While laying rate in infected LB hens decreased significantly (P < 0.05) in the early infection period (i.e. by 3 wpi), the decrease in LD hens appeared much later (i.e. by 14 wpi). Worm burdens resulting from the experimental infection were not different between the genotypes for both worm species (P > 0.05), whereas LB hens were more susceptible (P < 0.05) to re-infections than LD hens. Changes in humoral immune responses (i.e. ascarid-specific IgY antibodies in plasma and egg yolks) of the two genotypes over time reflected closely the corresponding changes in larval counts of the hens, descending from both experimental and subsequent natural infections in both genotypes. Infections caused a shift in egg size classes, leading to smaller frequency of larger eggs in both genotypes. Infections reduced egg weight (P = 0.018) and led to a reduced fat content in the egg yolks (P = 0.045). The proportion of poly-unsaturated fatty acids (PUFA), especially n-6-PUFA, was also lower in egg yolks of the infected hens (P = 0.032). We conclude that tolerance to nematode infections in laying hens is dependent on host-performance level. The impairment in host tolerance was both genotype and time dependent, likely due to differences in genetic programming for production peak and persistency of the two genotypes. The two genotypes exhibited similar levels of resistance after a fully controlled experimental infection, but the high performing hens were more susceptible to subsequent natural infections. Infections negatively affected economically important egg-quality traits, including egg weight, fat content and fatty acid profiles in egg yolks.

In vitro cultivation of Cymatocarpus solearis (Brachycoeliidae) metacercariae to obtain the adult stage without the marine turtle definitive host.

In vitro cultivation of trematodes would assist studies on the basic biology of the parasites and their hosts. This is the first study to use the yolk of unfertilized chicken eggs as a simple and successful method of ovocultivation and the first time to obtain the adult-stage of the trematode Cymatocarpus solearis Braun, 1899 (Digenea: Brachycoeliidae). Chicken eggs were inoculated with metacercariae from the muscle of the spiny lobster, Panulirus argus (Latreille, 1804). The metacercariae were excysted and incubated for 576 hr (24 days) at 38 to obtain the adult stage. Eggs in utero were normal in shape and light brown color. The metacercariae developed into mature parasites that have been identified as the adult-stage found in marine turtles. The adult lobsters collected in Quintana Roo State, Mexico, showed the prevalence of 49.4% and the mean intensity of 26.0 per host (n = 87). A statistical study was performed to determine that no parasitic preference was detected for male versus female parasitized lobsters. Morphometric measurements of the adult-stage of C. solearis obtained in our study have been deposited in the National Helminths Collection of the Institute of Biology of the National Autonomous University of Mexico. This study is significant because it is the first time that a digenean of the family Brachycoeliidae has been demonstrated to develop in vitro from metacercariae into adults capable of producing eggs using the yolk of unfertilized chicken eggs. Secondly, this technique allows to obtain the adult stage of C. solearis without the presence of its marine turtle host, allows us to describe the mature parasites, and thus contribute to our understanding of the biology of C. solearis.

In Vitro Cultivation of Cymatocarpus solearis (Brachycoeliidae) Metacercariae to Obtain the Adult Stage without the Marine Turtle Definitive Host

In vitro cultivation of trematodes would assist studies on the basic biology of the parasites and their hosts. This is the first study to use the yolk of unfertilized chicken eggs as a simple and successful method of ovocultivation and the first time to obtain the adult-stage of the trematode Cymatocarpus solearis Braun, 1899 (Digenea: Brachycoeliidae). Chicken eggs were inoculated with metacercariae from the muscle of the spiny lobster, Panulirus argus (Latreille, 1804). The metacercariae were excysted and incubated for 576 hr (24 days) at 38degrees C to obtain the adult stage. Eggs in utero were normal in shape and light brown color. The metacercariae developed into mature parasites that have been identified as the adult-stage found in marine turtles. The adult lobsters collected in Quintana Roo State, Mexico, showed the prevalence of 49.4% and the mean intensity of 26.0 per host (n = 87). A statistical study was performed to determine that no parasitic preference was detected for male versus female parasitized lobsters. Morphometric measurements of the adult-stage of C. solearis obtained in our study have been deposited in the National Helminths Collection of the Institute of Biology of the National Autonomous University of Mexico. This study is significant because it is the first time that a digenean of the family Brachycoeliidae has been demonstrated to develop in vitro from metacercariae into adults capable of producing eggs using the yolk of unfertilized chicken eggs. Secondly, this technique allows to obtain the adult stage of C. solearis without the presence of its marine turtle host, allows us to describe the mature parasites, and thus contribute to our understanding of the biology of C. solearis.

Pesquisa de Salmonella Enteritidis em ovos em casca / Research of Salmonella Enteritidis in fresh intact shell eggs

O objetivo do presente trabalho foi verificar a presença da Salmonella Enteritidis na gema de ovos que apresentavam nomáximo cinco dias de comercialização e características de qualidade compatíveis com as estabelecidas pela legislaçãobrasileira. Realizou-se a pesquisa de Salmonella Enteritidis em gemas de 96 ovos divididos em grupos de 12 ovos, ou seja,subdivididos em oito lotes. Os resultados foram negativos, não sendo detectados estirpes de Salmonella Enteritidis emnenhum dos lotes estudados. Conclui-se, portanto, ser baixa a ocorrência desta bactéria na gema dos ovos em cascaanalisados, cujos resultados foram compatíveis com os padrões de identidade e qualidade estabelecidos pela legislaçãobrasileira.

The objective was verify the presence of Salmonella Enteritidis in the yolk of eggs that presented no more than five days ofpacking and compatible quality characteristics with the established ones for the Brazilian legislation. We took place the researchof Salmonella Enteritidis in yolks of 96 eggs divided in groups of 12 eggs, in other words, 8 lots. The results, in its totality, werenegative, not detecting Salmonella Enteritidis in none of the studied lots. The absence of Salmonella Enteritidis observedindicates to be low the occurrence of this bacteria in the yolk of the fresh eggs with compatible identity and quality patterns withthe established by the Brazilian legislation.

Assessment of maternal immunity to Cryptosporidium baileyi in chickens.

The degree of protection to Cryptosporidium baileyi in the progeny of infected chickens was studied. Hens at the beginning of their laying period were given orally three consecutive, large doses of C. baileyi oocysts at weekly intervals. The infection became patent after 6 days and lasted for another 6 days. Increasing serum IgG, and serum, bile, lachrymal and salivary IgA were demonstrated from their samples. These immunoglobulins were transferred to the eggs, since high levels of maternally derived IgG and lower amount of IgA were present in their yolks. Hatchlings of infected hens were divided into uninfected (UY) and infected (IY) groups, the birds in the latter receiving an oral inoculum of C. baileyi oocysts on the first day of their life. Two other groups, progeny of uninfected hens served as controls (uninfected UC, and infected IC). Maternal IgG was detected in serum samples of UY hatchlings which was eliminated by the third week. The total oocyst shedding of IY chickens was 54.3% lower than that of the controls (IC), however, the prepatent and patent periods did not show significant difference. In spite of the partial protection observed in IY birds, their humoral immune response to C. baileyi was significantly lower when compared to IC. A dot-ELISA was developed to evaluate seroconversion of infected chickens which was 100% in both infected groups. The findings of the present study suggest that infection of hens with C. baileyi results in partial protection of their progeny to this parasite, and factors other than immunoglobulins may also be transferred via the eggs.