D. T. Ort

Broiler embryo bone development is influenced by incubator temperature, oxygen concentration and eggshell conductance at the plateau stage in oxygen consumption1

1. Four experiments were conducted to evaluate the effects of temperature (TEM) and oxygen (O2) concentrations during the last 4 d of incubation on bone development. Fertile eggs from two strains were obtained that either exhibited Low or High eggshell conductance (G). 1The mention of trade names in this publication does not imply endorsement of the products mentioned nor criticism of similar products not mentioned. 2. Four experimental cabinets provided either four TEM (36, 37, 38 or 39°C) or four O2 concentrations (17, 19, 21 or 23% O2). Data were analysed as a 2 × 2 factorial design. In the fourth experiment, two temperatures (36 and 39°C), two O2 concentrations (17 and 23%) and the same Low and High G strains were evaluated in a 2 × 2 × 2 factorial design. 3. Body weights (BW) and residual yolks were obtained, both legs were dissected. Femur, tibia and shank weights, length and thickness were recorded. Relative asymmetry (RA) of each leg section was calculated. 4. The results indicated that elevated TEM during incubation increased RA between the two legs, mainly in the Low G strain. Chickens at the lowest O2 concentrations had lighter and shorter tibias, lighter shanks, and increased RA of femur length compared to chickens in the 23% O2. In the fourth experiment no interactions were observed between O2 and TEM. High TEM depressed BW of Low G broilers, but no significant effect of treatments was observed on BW of High G broilers. Nevertheless, the high TEM or low O2 independently caused reduced femur and tibia weights and length, shank length and thickness, and both low O2 and high TEM together increased RA in shank weight. 5. These results suggest that late incubation conditions affect long bone development in broilers.

Effects of Incubator Temperature and Oxygen Concentration During the Plateau Stage of Oxygen Consumption on Turkey Embryo Long Bone Development

Temperature (TEM) and O(2) concentrations during the plateau stage of oxygen consumption are known to affect yolk utilization, tissue development, and thyroid metabolism in turkey embryos. Three experiments were conducted to evaluate these incubation effects on long bone development. Fertile eggs of Nicholas turkeys were used. In each trial, standard incubation conditions were used to 24 d, when the eggs containing viable embryos were randomly divided into 4 groups. Four experimental cabinets provided 4 TEM (36, 37, 38, or 39 degrees C) or 4 O(2) concentrations (17, 19, 21, or 23% O(2)). In the third experiment, 2 temperatures (36 and 39 degrees C) and 2 O(2) concentrations (17 and 23%) were evaluated in a 2 x 2 factorial design. Body and residual yolk weights were obtained. Both legs were dissected, and shanks, femur, and tibia weights, length, and thickness were recorded. Relative asymmetry of each leg section was calculated. Chondrocyte density was evaluated in slides stained with hematoxylin and eosin. Immunofluorescence was used to evaluate the presence of collagen type X and transforming growth factor beta. Hot TEM caused reduction of tibia weights and increase of shank weight when compared with cool TEM. The lengths of femur, tibia, and shanks were reduced by 39 degrees C. The relative asymmetry of leg weights were increased at 38 and 39 degrees C. Poult body and part weights were not affected by O(2) concentrations, but poults on 23% O(2) had bigger shanks and heavier tibias than the ones on 17% O(2). High TEM depressed the fluorescence of collagen type X and transforming growth factor beta. The O(2) concentrations did not consistently affect the immunofluorescence of these proteins. The chondrocyte density was affected by TEM and O(2) in resting and hypertrophic zones. In the third experiment, high TEM depressed BW, leg muscle weights, and shank length. Low O(2) reduced tibia and shanks as a proportion of the whole body. We concluded that incubation conditions affect long bone development in turkeys.

Genetic Control of Embryonic Cardiac Growth and Functional Maturation in Turkeys

Turkey experimental lines E (selected 44 yr for increased total egg production) and F (selected 38 yr for increased 16-wk BW) were mated reciprocally with the randombred control lines from which they were derived (RBC1 and RBC2, respectively), and the pureline and reciprocal cross poults were compared for their BW, heart weight, heart rates, myocardial glycogen and lactate concentrations, and plasma creatine kinase (CK) and lactate dehydrogenase (LDH) activities. The CK and LDH were used as indicators of cardiac insufficiency. Orthogonal contrasts of the data from the pureline and reciprocal cross data were used to estimate additive genetic effects, reciprocal effects (confounded maternal and sex-linked effects), and heterosis for each of the traits measured. Long-term selection for increased egg production in the E line has reduced embryo heart weight and has altered the energy metabolism of the myocardium. The differences in energy metabolism may be due to the more rapid heart rates. Conversely, long-term selection for increased 16-wk BW has significantly decreased the heart rate of F line embryos and has not changed the weight of the heart relative to the BW until the embryo has passed through the plateau stage. The F line embryos show a different energy metabolism that relies much more on gluconeogenesis. Embryo deaths occur more frequently in turkey embryos when the energy metabolism of the myocardium shows elevated glycogen to lactate ratios as it did in the pure E and F lines.