Search

BACKGROUND: Toxoplasmosis is a zoonosis caused by the parasite Toxoplasma gondii. The most affected population are pregnant women, newborns, and immunosuppressed patients. The State of Tabasco, Mexico, has both climatic and biotic conditions that favors the parasite's dissemination and perpetuation, which create its great genetic variability, and can also generate the appearance of more virulent variants. To date, 319 different genotypes have been described worldwide with a wide variation of its virulence levels in murine models. OBJECTIVE: To isolate and genotype Toxoplasma gondii from free-range chicken tissues and to predict the virulence of the obtained isolates by the identification of the associated genetic markers. METHODOLOGY: Heart and brain samples of 12 free-range chickens from seven municipalities of Tabasco were collected to attempt the parasite's isolation in mice. Obtained tachyzoites were propagated in NIH3T3 mice fibroblasts. Parasite DNA was extracted and used to genotype each isolate by Mn-PCR-RFLP of 15 T. gondii genetic markers. RESULTS: Twelve isolates were obtained in total. Two belonged to the genotype ToxoDB #8, tree ToxoDB #28, four ToxoDB #38 and three genotypes which has not yet been described or reported. The genotypes #8, #28 and #38 have already been described in States from the Center and Southwest regions of Mexico, whereas the three new genotypes have not been reported and were identified as the genotypes ToxoDB #344, #345 y #346. In virulence markers ROP18/ROP5, were identified combinations of alleles that can predict high and low virulence in murine models. CONCLUSIONS: Toxoplasma gondii is highly prevalent in Tabasco, Mexico since isolates were obtained in more than 50% of the sampled animals. From these isolates virulent and non-virulent variants in murine model are predicted, which could have a direct impact in public health. [ABSTRACT FROM AUTHOR]

Feed efficiency for males and females of two three-way experimental hybrids of free range chickens (Campero Casilda y Campero Pergamino) and in Campero INTA as reference genotype, was calculated in five consecutive weekly periods between 42 and 77 days of age as well as in the overall period. No significant difference among groups in efficiency and related variables were evident in each of the periods, in both sexes. Males were heavier, had higher average daily feed intake, higher average daily weight gain and showed higher feed efficiency and lower conversion ratio than females. The behavior of the two variables -feed intake and body weight gain- determining feed efficiency shows that at the end of the fourth of the five periods (63-70 days old), males have already reached the target slaughter weight of 2500 g but not the minimum age (70 days) required by the production protocol, a situation not evident in females. This fact determines that males must be slaughtered at least one week after with a higher body weight (3000 g). Going from 4th to 5th period (70-77 days) increases feed intake and decreases body weight gain, resulting in a decreased feed efficiency, or its equivalent, a deterioration of the feed conversion ratio. In terms of these traits the three genetic groups show equivalent behaviors with conversion values (> 3 kg of feed per kg weight gain) higher than those usually reported for the intensive production model. This situation must be taken into account when poultry meat production takes place under more or less extensive systems that emphasize the preservation of animal welfare. [ABSTRACT FROM AUTHOR]

Univariate and multivariate characterization of male and female chickens belonging to two three-way experimental hybrids developed for producing free range chickens, in comparison with Campero INTA as the reference genotype, both in terms of a set of linear measurements recorded before slaughter as well as with four zoometric indices, revealed an at least partially independent genetic basis for shape and body size. The principal component multivariate analysis of carcass yield at slaughter plus breast, legthigh and abdominal fat proportions evinced the presence of sources of variation for breast and leg-thigh independent of body fat content as well as two sources of variation for breast percentage, one independent and the other negatively associated with leg-thigh proportion. Although the multivariate analysis allowed characterizing the birds of each sex in terms of some particularities of potential selective significance not apparent when using a univariate approach, differences among genetic groups within sex were not remarkable from a productive point of view. Slow-growing type birds evaluated in this study showed a good breast muscle development -unlike the old-fashioned field chickens- maintain the typical sexual dimorphism of the species and exhibit their characteristic “pheasant type” phenotype together with a variable plumage pigmentation different from pure white which identifies and distinguishes them from those hybrids usually exploited by the commercial poultry industry. Regarding slaughter traits both experimental three-way crosses can be considered similar not only between them but also when compare with the reference genetic group. [ABSTRACT FROM AUTHOR]

Feed efficiency for males and females of two three-way experimental hybrids of free range chickens (Campero Casilda y Campero Pergamino) and in Campero INTA as reference genotype, was calculated in five consecutive weekly periods between 42 and 77 days of age as well as in the overall period. No significant difference among groups in efficiency and related variables were evident in each of the periods, in both sexes. Males were heavier, had higher average daily feed intake, higher average daily weight gain and showed higher feed efficiency and lower conversion ratio than females. The behavior of the two variables -feed intake and body weight gain- determining feed efficiency shows that at the end of the fourth of the five periods (63-70 days old), males have already reached the target slaughter weight of 2500 g but not the minimum age (70 days) required by the production protocol, a situation not evident in females. This fact determines that males must be slaughtered at least one week after with a higher body weight (3000 g). Going from 4th to 5th period (70-77 days) increases feed intake and decreases body weight gain, resulting in a decreased feed efficiency, or its equivalent, a deterioration of the feed conversion ratio. In terms of these traits the three genetic groups show equivalent behaviors with conversion values (> 3 kg of feed per kg weight gain) higher than those usually reported for the intensive production model. This situation must be taken into account when poultry meat production takes place under more or less extensive systems that emphasize the preservation of animal welfare. [ABSTRACT FROM AUTHOR]