Meat yield in Turkeys

Study of Meat and Carcass Quality-Related Traits in Turkey Populations through Discriminant Canonical Analysis

The present research aimed to determine the main differences in meat and carcass quality traits among turkey genotypes worldwide and describe the clustering patterns through the use of a discriminant canonical analysis (DCA). To achieve this goal, a comprehensive meta-analysis of 75 documents discussing carcass and meat characteristics in the turkey species was performed. Meat and carcass attributes of nine different turkey populations were collected and grouped in terms of the following clusters: carcass dressing traits, muscle fiber properties, pH, color-related traits, water-retaining characteristics, texture-related traits, and meat chemical composition. The Bayesian ANOVA analysis reported that the majority of variables statistically differed (p < 0.05), and the multicollinearity analysis revealed the absence of redundancy problems among variables (VIF < 5). The DCA reported that cold carcass weight, slaughter weight, sex-male, carcass/piece weight, and the protein and fat composition of meat were the traits explaining variability among different turkey genotypes (Wilks' lambda: 0.488, 0.590, 0.905, 0.906, 0.937, and 0.944, respectively). The combination of traits in the first three dimensions explained 94.93% variability among groups. Mahalanobis distances cladogram-grouped populations following a cluster pattern and suggest its applicability as indicative of a turkey genotype's traceability.

The growth of turkeys 2. Body components and allometric relationships

1. The relationships between the main components of the body and body protein among males and females of BUT 6 (BUT) and Hybrid Converter (HYB) turkey strains were examined. 2. The weights of breast meat, breast skin, drumstick meat, drumstick skin, thigh meat, thigh skin and wing-plus-skin as well as the head, neck, feet, blood, heart, liver and gizzard were measured at different stages of growth after which all components of each bird were minced together in order to determine the feather-free body protein weight of each bird sampled. Using the weights of the components and the protein content of each bird the allometric relationships between the components and body protein were determined and then compared for each strain x sex combination. 3. By excluding the breast weights at day-old and at 7 d, the remaining points produced an acceptable allometric relationship (R² = 0.992). Thigh weight could be predicted for all strain x sex combinations using one allometric equation, as could drumstick skin weight. Breast and thigh skin weights differed between males and females. Females of the HYB strain exhibited heavier drumstick and wing-plus-skin weights at a given body protein weight than the other three strain x sex combinations. These differences in both the constant term and regression coefficient in the allometric equations between genotypes are probably due to differences in the amount of lipid that is deposited in these tissues. 4. Sexes differed in the allometric relationships for head, feet, heart and liver, while breeds differed in gizzard weight. A common relationship between the four genotypes could be used to predict the weight of blood in the carcass. 5. The allometric equations fitted to the data in this trial enable the accurate prediction of the weights of the different physical components given the weight of body protein.

Body composition and development measured repeatedly by computer tomography during growth in two types of turkeys

Distribution and development of fat, muscles, and bone were studied repeatedly by computer tomography from 4 to 17 wk of age in two commercial strains of turkeys (BUT-9 and Nicholas) of both sexes. Generally, the proportion of total fat and meat increased and bone decreased significantly throughout the experimental period for both strains and sexes. When compared at the same age or body weight, BUT-9 tended to have a higher percentage of meat than did Nicholas (0 to 3 percentage units). From 8 to 17 wk of age, Nicholas showed higher fat percentage and lower bone percentage than BUT-9. Based on this study, regardless of weight at slaughtering, BUT-9 should be preferred. Because males had a significantly higher body weight gain and higher percentage of meat from 8 wk of age, males should be used in production to fit the market for high slaughter weights with large pieces of meat. Because females had a higher meat percentage at young ages compared with males, but showed an earlier fattening and lower weight gain, females should preferably be slaughtered at lower live weights. Computer tomography can be considered an appropriate but expensive method to study body composition and development in turkeys.

Effect of crossing a line selected for increased shank width with two commercial sire lines on performance and walking ability of turkeys

Published research indicated that a line (FL) of turkeys selected for increased shank width and exhibiting good walking ability (WA) and improved leg structure was useful in improving WA of a cross with an unimproved commercial sire line while remaining competitive in BW and body conformation. The purpose of the present study was to determine whether the FL line was useful in improving WA of two improved commercial primary-breeding sire lines and to study the inheritance of BW traits in the pure lines and reciprocal crosses of the pure lines. Samples of a primary breeding sire line from each of two major commercial turkey breeders were obtained as unpedigreed eggs and designated as Lines A and B. Lines A and B were reciprocally crossed with the FL line that had been selected for increased shank width for 16 generations. Pure lines and reciprocal crosses were produced by artificially mating 10 males to 15 females using pooled semen. The same semen pools were used to produce both the pure lines and the crosses. Traits measured included BW at 8, 16, and 20 wk of age, and length, width, and depth of the shank, width of the breast, and WA at 16 wk of age. The A and B lines were larger and had wider breasts and narrower and shorter shanks than the FL line. Line B was larger than Line A. Shank measurements and WA score did not differ between Lines A and B in either sex. Breasts of Line B females were wider than those of Line A females, but there was no sire line difference in breast width of males. Heterosis in BW was greater in Line A crosses (average of 4.6% with a range of 2.5 to 7.2% for BW at different ages) than in Line B crosses (average of 2.2% with a range of 0.1 to 5.3%). Heterosis in WA score was negative (crosses had better WA than pure lines) for males [14% for the Line A and FL crosses (P < or = 0.001) and 4% for the Line B and FL crosses (P < or = 0.05)], but was positive and nonsignificant for females of the above crosses (average of 2.6 %). With one exception, heterosis was not an important source of variation for shank width or shank depth and there was a low level of heterosis for shank length. No heterosis was observed for breast width. Reciprocal effects were an important source of variation in BW and shank measurements for females but not for males in both sets of crosses. The results of the present study indicated that use of the FL line to improve WA of improved primary-breeding commercial sire lines was not a feasible alternative. The slight improvement noted in WA of the male crosses was offset by the reduction in BW and breast width of the crosses relative to the pure commercial sire lines.

Response of two strains of large white male turkeys to amino acid levels when diets are changed at three- or four-week intervals

A study was conducted to evaluate the amino acid recommendations of the NRC (1994) when diets were changed at 3- or 4-wk intervals. Diets formulated to provide from 90 to 115% of recommended amino acid levels were fed to Nicholas (NIC) and British United Turkey (BUT) Large White males from day-old to 24 wk of age; samples of turkeys were processed at 18 and 24 wk. Results indicated that the amino acid levels suggested by NRC are adequate to support maximum body weight gain, feed conversion, and dressing percentage of Large White males grown to 18 or 24 wk when fed on 4-wk intervals. An approximately 5% higher level of amino acids was required to maximize breast yield. When feeds were changed at 3-wk intervals, higher levels of amino acids were required to maximize performance; however, there did not seem to be any difference in the response of the two strains of turkeys to different levels of amino acids in this study.

Influence of crossing a line selected for increased shank width and a commercial sire line on performance and walking ability of turkeys

The present study was initiated to determine whether walking ability (WA) could be markedly improved without seriously compromising growth rate and body conformation by crossing a relatively unimproved commercial sire line (UC) with a line (FL) selected for increased shank width and backcrossing F1 females to UC line males. Body weights at 8, 16, and 20 wk of age were generally similar for both lines at the time of the initial cross. The UC line had inferior WA, shorter and narrower shanks, and wider breasts compared with the FL line. The F1 birds exhibited overdominance for BW at all ages. Heterosis in BW ranged from 3.2 to 7.8%. At 16 wk of age, the WA scores decreased (indicating improved WA) in the F1 relative to the average of the parental lines. Heterosis of WA scores was -10.5% (P > or = 0.05) for males and -23.5% (P < or = 0.05) for females. Heterosis was observed in the F1 for shank length but not for other shank measurements (width and depth). No heterosis was observed for breast width. Mortality from 8 through 20 wk of age was reduced in the F1 relative to the parental lines. The backcross of the F1 females to UC males still exhibited heterosis for male BW at 16 and 20 wk of age and for WA scores, although the magnitude was reduced 50% or more. Mortality from 8 to 20 wk of age decreased in the backcross compared with the parental lines. The results suggest that a line exhibiting improved leg structure and WA, and poor conformation, such as FL, can be used to greatly improve the WA of a cross involving a sire line with poor WA but excellent conformation. A portion of the gains in BW and breast width obtained in the F1 was retained in a backcross to the sire line, making such a crossing scheme commercially feasible.

Characterization of carcass development from 14 to 145 days of age in turkey hens from two strains

Body weight and carcass components were measured from 14 to 145 d in Nicholas (NIC) and Hybrid (HYB) strain turkey hens. At most ages, BW of HYB hens was greater than that of NIC and there were small but significant differences in the weight of the Pectoralis minor (PMIN). The relative weight of the PMIN increased in HYB hens from 98 to 145 d. No strain differences in either the absolute or relative weights of the Pectoralis major (PMAJ) were observed. The absolute and relative weights of the tibia plus associated muscles (DRUM) and femur plus associated muscles (THIGH) were significantly heavier in HYB hens. The same was true for the Gastrocnemius muscle (GASTROC). The relative weight of the abdominal fat pad (ABFAT) was significantly increased in NIC hens compared with HYB hens from 70 to 145 d. There was a linear relationship between the relative weight of the PMAJ and BW in hens from both strains (NIC, r2 = .69; HYB, r2 = .51). The relationship between the relative weight of the PMIN and BW was best described with a quadratic model but the r2 in both strains was considerably lower than that for the PMAJ (NIC, r2 = .26; HYB, r2 = .36). The linear relationship between BW and the relative weights of the THIGH and DRUM was negative and positive for ABFAT.

Relationship of sex, strain, and body weight to carcass yield and offal production in turkeys

Three strains of male and female market turkeys (British United Turkeys, Hybrid, and Nicholas) were grown under commercial contract production conditions and slaughtered at a range of BW (4,200 to 17,640 g) and age (13 to 22 wk) that covers the range of commercial market weights in use at the time of the study. During processing, the weight of blood, feathers, head, neck, feet plus shanks, heart, liver, gizzard, lungs, gastrointestinal tract, water uptake, hot and chilled carcass with fat pad, fat pad alone, tail, wings, drumsticks, thigh meat, Pectoralis major, Pectoralis minor, scapula meat, lower back, upper back with ribs, breast skin, thigh skin, thigh bone, and hind half (legs, thighs, and saddle) were determined. The data were subjected to least squares analyses using models that included strain and sex effects relative to live BW. Significant differences in yield between the sexes but not among strains were found for feet plus shanks, gizzard, hot and chilled carcass with fat pad, and scapula meat. Similarly, significant differences in yield among strains but not between sexes alone were found for blood, feathers, heart, and hind half. The relationships of live BW with all other variables showed both strain and sex differences in yield. Whereas whole carcass yield as a function of BW was affected by sex alone, most other components varied by both sex and strain. Thus, choice of strain, sex, and age at slaughter affect the projected production of edible carcass and offal components.

Genetic association of selection for increased leg muscle and increased shank diameter with body composition and walking ability

Body compositions of a randombred control population (RBC2), a line selected for increased 16-wk BW (F), a line selected for increased shank diameter (FL), and a line selected for increased leg muscle mass (FM) were compared at 16 wk of age. The F line originated from the RBC2 population and the FL and FM lines were developed as sublines of the F line. The F and FL lines were developed through mass selection of BW and shank width, respectively. The FM line was developed through family selection for leg muscle mass. Selection for BW in the F line has resulted in an increase in the proportion of breast muscle and a decrease in the relative amount of leg bone in comparison with the RBC2 population. Selection for increased shank width in the FL line has increased not only shank weight but has produced concomitant increases in the weight of the tibiotarsal and femur bones. Although FL line has also shown a correlated increase in BW in association with increases in shank width the increase in leg bone weight was relatively greater than the increase in BW. Therefore, the relative weights of leg bones in the FL line increased such that they were more similar to the RBC2 population than to the F line. Although the amount of leg muscle increased slightly in the FM line, the relative proportion of leg muscle did not increase significantly. The selection program used was probably ineffective in increasing the proportion of leg muscle because of the high percentage (low selection intensity) of families selected and small family size for estimating family means.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of dietary protein and added fat on turkeys varying in strain, sex, and age. 2. Carcass characteristics

The effects of dietary protein and added fat on carcass characteristics were determined at various ages for female and male turkeys and from three strains: Nicholas Large White (N), Jaindl Large White (JL), and Jaindl Medium White (JM). A total of 1,350 turkeys was divided into 36 pens and fed diets containing 0, 5, or 10% added fat and standard or high protein levels from 8 wk of age to time of processing. One-fourth of the females and one-third of the males from each pen were processed at 16, 20, 24, or 28 wk and at 20, 24, or 28 wk, respectively. Breast meat weight, expressed as a percentage of carcass weight, was greater for JM and JL turkeys than for N turkeys (34.6, 33.9, and 31.7%, respectively), increased with age (31.9, 34.1, and 34.2% at 20, 24, and 28 wk of age, respectively), was greater for females than for males (34.2 and 32.6%, respectively), decreased with added fat (33.7, 33.4, and 33.1% for 0, 5, and 10% fat, respectively) and increased with a 3% addition of dietary protein (33.2 and 33.6%, respectively).

Comparison of bone and muscle growth in turkey lines selected for increased body weight and increased shank width

A subline (FL) of a long-term growth-selected line (F) of turkeys was established by mass selecting solely for increased shank width at the narrowest point (dew claw). A comparison was made of bone and muscle growth in Line FL (fourth generation of selection), Line F (17th generation of selection), and a randombred control (RBC2, the base population of F) at 8, 16, and 20 wk of age. Also, a sample of the tibiotarsal and femur bones was studied histologically for evidence of pathological conditions. No significant pathological changes were observed in bones from turkeys of the different lines at the ages examined. Samples for histological study were taken at Day 1, 27, 56, 84, 112, and 140 posthatching. Genetic increases in body weight (F and FL lines) resulted in a significant decline in the relative amount of leg muscles from 16 to 20 wk of age while in Line RBC2 the relative amount of leg muscles increased slightly from 16 to 20 wk of age. This resulted in a significant line x age interaction. No significant differences in the amount of leg muscles were detected between turkeys of Lines F and FL. Amount of breast muscles increased consistently with age in all lines. Amount of breast muscles (absolute and as a percentage of body weight) was larger in Line F than in the FL and RBC2 lines. The actual weight of the breast muscles was larger in Line FL than in the RBC2 line but as a percentage of body weight there was no significant difference.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth, feed conversions, and yields of turkey parts of three strains of hen turkeys as influenced by age

Effects of age on the growth, feed to gain ratios, individual part weights, and yields of hen turkeys were determined weekly from ages 12 to 21 weeks. Two hundred birds from each of three strains (A, B, and C) were processed. All three strains of hen turkeys continued to gain weight throughout the study. During the 12 to 21-week-old period birds grew from an average of 4.76 kg to 9.17 kg, while the cumulative feed to gain ratios went from 1.97 to 2.94. Strain B consistently weighed more than Strains A and C for the duration of the study. Weights of all parts increased as hens grew larger. However, the parts' proportion of total weight changed. Percentages of breast, breast muscle, and fat increase, while percentages of wing, drumstick, and skin decreased. Breast, breast muscle, and fat yields increased from 32.8 to 35.9%, 23.8 to 28.0%, and 1.7 to 5.1%, respectively. Both wing and drumstick percentages declined from approximately 14.0 to 12.0%. Thigh, thigh muscle, and shell percentages varied, but ended near their starting levels, of 14.8, 10.5, and 21.8%, respectively. At 21 weeks of age the hen turkeys were still gaining body weight. Breast weight--both actual and percentages--were still increasing.

The influence of genetic increases in shank width on body weight, walking ability, and reproduction of turkeys

Body weight and breast width have been greatly increased in the modern turkey. However, the relative amounts of leg muscles and leg bones have declined. A similar decline also occurs with age. It was theorized that this is an inherent weakness that magnifies other causes of leg problems. In an attempt to increase the relative amount of leg bone, a subline (FL) was developed by mass selection for increased shank width at 16 weeks of age from a long-term growth-selected line of turkeys (F). Shank width of FL was increased greatly by selection. The realized heritability of shank width, based on the regression of accumulated selection response on accumulated selection differential, was .33 +/- .05 over five generations of selection. Body weight of males from FL increased at a rate comparable to that of F at 16 weeks of age. However, there was no comparable improvement in body weight of FL females, resulting in a significant line X sex interaction. A similar interaction was observed for body weight at 8 and 20 weeks of age in these lines. The genetic increases in shank width in FL resulted in significantly improved walking ability of males at 16 weeks of age in comparison to F, even though body weight of males from the two lines was similar. The walking ability of FL did not change relative to the control line from which F originated. Thus, large genetic increases in body weight of males can be achieved without loss in walking ability by genetic increases in shank width.(ABSTRACT TRUNCATED AT 250 WORDS)