Response to Selection for Hatchability in Turkeys at Three Altitudes

Abstract

Eggs from a commerical flock of Small White turkeys established at 76 meters above sea level were used to develop five lines of turkeys. Hatchability of fertile eggs was the only criterion used to establish selected lines at 76, 1524, and 2182 meters. Control lines were maintained at the 76 and 1524-meter locations. The objective of this study was to evaluate effects of the selection program on organ weights, body weight, and packed cell volumes (PCV). For two generations, eggs from one hatch at each of the three elevations were divided into three groups, two of which were exchanged for hatching and rearing. Twenty poults from the five lines at all three locations were sacrificed at 1-day, 2-weeks, and 4-weeks of age. Heart. liver spleen, adrenals, pancreas, lungs, kidneys, and gonads were removed, weighed, and the weight expressed as a percent of body weight. Blood samples were collected and PCV values determined at ages 1-day, 2-weeks, and 4-weeks at the 1524-meter elevation. Selection for hatchability had no adverse effect upon 1-day, 2, and 4-week body weights. Variations in body weight between locations were not due to natural environmental conditions, but rather to variations in management. Selection for hatchability coupled with natural selection resulted in the development of lines of turkeys with higher PCV values than the original control population. Exposure of turkey poults from the five genetic lines developed at an altitude of 2182 meters lead to an increase in relative weights of the heart and adrenal glands compared to birds at the 76 and 1524-meter locations. Exposure at the 2182-meter location also resulted in lighter spleens, pancreata, kidneys, and ovaries compared to birds at the 76 and 1524-meter locations. Selection for hatchability favors larger adrenals, livers, pancreata, kidneys, and lungs, but smaller hearts. Natural selection at higher elevations compounds the situation by favoring smaller adrenals and livers, but larger spleens, pancreata, and kidneys.

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

“…Adrenal glands have not been considered in any of the currently available PBPK models for chickens. In turkeys, adrenal glands constitute 0.019% of body weight based on two studies (Davis & Siopes, 1985 ; Hobbs & Moreng, 1976 ) as shown in Table 4 . Davis and Siopes ( 1985 ) conducted a study to determine the effect of light duration on turkey poult performance and adrenal function, in which the adrenal weight values were measured in 97 turkeys.…”

“…The pulmonary parenchyma compartment is commonly referred as the lung compartment in existing poultry PBPK models (Lautz et al., 2020 ; Yang et al., 2014 , 2015 ). Based on the data from eleven studies involving over 1,200 animal subjects (Adeyemi et al., 2008 ; Bowes & Julian, 1988 ; Buys, 1999 ; Cortright et al., 2009 ; Hobbs & Moreng, 1976 ; Marsden, 1940 ; Nestor et al., 2005 ; Tickle et al., 2014 ; Wideman, 1999 ; Wideman et al., 1996 ; Wolfenson et al., 1978 ), the mean relative weight of pulmonary parenchyma for broiler chickens of all ages, broiler chickens of market age, layers, and turkeys of all ages are approximately 0.71%, 0.61%, 0.66%, and 0.83% of the body weight, respectively (Tables 1 , 2 , 3 , 4 ). These values are comparatively higher than the weight used in the PBPK studies for chickens (Yang et al., 2014 , 2015 ), which was 0.54% of body weight experimentally derived from 10 chickens in Cortright et al.…”

“…PBPK models may include reproductive organs as individual compartments when egg production is accounted for; therefore, values of related organs from broiler chickens, layers, and turkeys were adopted from the literature and included in this study. For female broiler chickens, even though it is not significant due to sexual immaturity, the weight of the ovary was identified as 0.043% body weight (Bayyari, Huff, Balog, et al., 1997 ; Hobbs & Moreng, 1976 ; Melnychuk et al., 1997 ; Renema et al., 1995 ) (Table 1 ). For the layers, weight values of the ovary were acquired after removal of ovulated follicles (Renema et al., 1995 ).…”

“…( 1975 ). For turkeys, the average value of 0.27% of body weight for ovary was calculated from four studies with 596 animal subjects (Hobbs & Moreng, 1976 ; Melnychuk et al., 1997 ; Rauber et al., 2007 ; Renema et al., 1995 ) (Table 4 ). Although the values for the other segments of the oviduct were not identified in the literature, the total oviduct weight was calculated to account for 1.03% of the total body weight.…”

“…Sources for data variability included different factors such as altitude, light cycle, and light duration (Hobbs & Moreng, 1976 ; USDA, 2013 ). Recommended light intensity during different growth stages is available in the Poultry Industry Manual (USDA, 2013 ).…”