Genetic variation in pure lines and crosses of large-bodied turkeys. 4. Body shape and carcass traits

Physiological parameter values for physiologically based pharmacokinetic models in food-producing animals. Part II: Chicken and turkey

Physiologically based pharmacokinetic (PBPK) models are growing in popularity due to human food safety concerns and for estimating drug residue distribution and estimating withdrawal intervals for veterinary products originating from livestock species. This paper focuses on the physiological and anatomical data, including cardiac output, organ weight, and blood flow values, needed for PBPK modeling applications for avian species commonly consumed in the poultry market. Experimental and field studies from 1940 to 2019 for broiler chickens (1-70 days old, 40 g - 3.2 kg), laying hens (4-15 months old, 1.1-2.0 kg), and turkeys (1 day-14 months old, 60 g -12.7 kg) were searched systematically using PubMed, Google Scholar, ProQuest, and ScienceDirect for data collection in 2019 and 2020. Relevant data were extracted from the literature with mean and standard deviation (SD) being calculated and compiled in tables of relative organ weights (% of body weight) and relative blood flows (% of cardiac output). Trends of organ or tissue weight growth during different life stages were calculated when sufficient data were available. These compiled data sets facilitate future PBPK model development and applications, especially in estimating chemical residue concentrations in edible tissues to calculate food safety withdrawal intervals for poultry.

Comparative Quantitative Studies on the Microvasculature of the Heart of a Highly Selected Meat-Type and a Wild-Type Turkey Line

In this study the macroscopic and microscopic structure of the heart of a fast growing, meat-type turkey line (British United turkeys BUT Big 6) and a wild-type turkey line (Canadian Wild turkey) were compared. At 8 and 16 weeks of age, 10 birds of each genotype and sex were sampled. The body mass and heart mass of the meat-type turkey both increased at a faster rate than those of the wild-type turkey. However in both turkey lines, the relative heart mass decreased slightly with age, the decrease was statistically significant only in the male turkeys. Furthermore meat-type turkeys had a significantly (p < 0.01) lower relative heart mass and relative thickness of the left ventricle compared to the wild-type turkeys of the same age. The wild-type turkeys showed no significant change in the size of cardiomyocytes (cross sectional area and diameter) from 8 weeks to 16 weeks. In contrast, the size of cardiomyocytes increased significantly (p < 0.001) with age in the meat-type turkeys. The number of capillaries in the left ventricular wall increased significantly (p < 0.001) in wild-type turkeys from 2351 per mm² at the age of 8 weeks to 2843 per mm² at 16 weeks. However, in the meat-type turkeys there were no significant changes, capillary numbers being 2989 per mm² at age 8 weeks and 2915 per mm² at age 16 weeks. Correspondingly the area occupied by capillaries in the myocardium increased in wild-type turkeys from 8.59% at the age of 8 weeks to 9.15% at 16 weeks, whereas in meat-type turkeys this area decreased from 10.4% at 8 weeks to 9.95% at 16 weeks. Our results indicate a mismatch in development between body mass and heart mass and a compromised cardiac capillary density and architecture in the meat-type turkeys in comparison to the wild-type turkeys.

Growth performance and carcass characteristics of female turkeys as affected by feeding programs

A trial was conducted to evaluate the effects of different feeding programs on growth performance and carcass characteristics of Nicholas Large White female turkeys. Three different feeding programs were considered for a 12-wk period: 1) 3 diets fed for 4 wk each (starter 24% CP, grower 20% CP, and finisher diet 16% CP), 2) 2 diets fed for 6 wk each (starter-grower 22% CP and grower-finisher diet 18% CP), and 3) no change of diet for 12 wk (starter-grower-finisher diet 20% CP). From 0 to 4 wk of age, birds were fed an ad libitum common starter diet. Each dietary treatment was replicated 3 times, and feed and water were provided ad libitum. Body weight and feed consumption were measured every 2 wk, whereas carcass characteristics were evaluated at 16 wk of age. Feed intake increased as the frequency of dietary changes decreased, and feed conversion was not different between programs 1 and 3. There were no significant differences in final BW among experimental groups. For a single feeding program, the proportion of neck, bone, and feet decreased, and a greater percentage of edible meat was registered as compared with the other 2 groups. Mean carcass, breast, and thigh weights of turkeys reared under multiple diets were not different compared with other groups. Positive correlations were noted between live weight and weight of carcass, breast, thigh, drumstick, wing, and abdominal fat of turkeys. Thus, a single cycle feeding regimen in Nicholas Large White female turkeys results in similar growth performance and carcass characteristics compared with other conventional feeding programs considered in the present study.

Genetics of growth and reproduction in the turkey. 16. Effect of repeated backcrossing of an egg line to a commercial sire line

The turkey industry's view of the relative economic importance of growth and egg production has changed rapidly, and genetic changes by selection within lines may not be rapid enough to meet the changing needs. The objective of the present study was to determine the feasibility of rapidly increasing the BW of dam lines by repeated backcrossing of a dam line (E) to a commercial sire line (B). The experimental E line was selected long-term for increased egg production and was used as the model for a turkey dam line. The B line was larger (more than 3-fold) in BW at 8, 16, and 20 wk of age, had wider breasts (approximately 1.8-fold) at 16 wk of age, and had lower egg production for 180 d (about 3-fold) than the E line. Based on additive genetic variation, males in the F1 generation of the B x E cross did not differ from expected in BW at any age, but females of this cross had BW less than expected at 16 and 20 wk of age. In the F1 generation, breast width of the cross did not differ from the expected value, but egg production for 180 d was greater than expected (126.6 vs.102.3 eggs/hen). After 3 generations of backcrossing, the backcrosses exhibited a gain in 20-wk BW of 12.5 and 8.8 kg, respectively, for males and females; a gain of 5.9 and 5.3 cm in breast width at 16 wk of age for males and females, respectively; and a loss of 74.1 eggs per hen over a 180-d production period. Based on the results of the current and a previous study, limited backcrossing of a dam line to a sire line may be an economically feasible method to greatly increase the BW of dam lines without unduly sacrificing egg production. For maximum gains per generation, backcrossing probably should be used for a maximum of 2 or 3 generations.