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Ni A, Calus MPL, Bovenhuis H, Yuan J, Wang Y, Sun Y, Chen J. Genetic parameters, reciprocal cross differences, and age-related heterosis of egg-laying performance in chickens. Genet Sel Evol 2023; 55:87. [PMID: 38062365 PMCID: PMC10702067 DOI: 10.1186/s12711-023-00862-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 11/28/2023] [Indexed: 12/18/2023] Open
Abstract
BACKGROUND Egg-laying performance is economically important in poultry breeding programs. Crossbreeding between indigenous and elite commercial lines to exploit heterosis has been an upward trend in traditional layer breeding for niche markets. The objective of this study was to analyse the genetic background and to estimate the heterosis of longitudinal egg-laying traits in reciprocal crosses between an indigenous Beijing-You and an elite commercial White Leghorn layer line. Egg weights were measured for the first three eggs, monthly from 28 to 76 weeks of age, and at 86 and 100 weeks of age. Egg quality traits were measured at 32, 54, 72, 86, and 100 weeks of age. Egg production traits were measured from the start of lay until 43, 72, and 100 weeks of age. Heritabilities and phenotypic and genetic correlations were estimated. Heterosis was estimated as the percentage difference of performance of a crossbred from that of the parental average. Reciprocal cross differences were estimated as the difference between the reciprocal crossbreds as a percentage of the parental average. RESULTS Estimates of heritability of egg weights ranged from 0.29 to 0.75. Estimates of genetic correlations between egg weights at different ages ranged from 0.72 to 1.00. Estimates of heritability for cumulative egg numbers until 43, 72, and 100 weeks of age were around 0.15. Estimates of heterosis for egg weight and cumulative egg number increased with age, ranging from 1.0 to 9.0% and from 1.4 to 11.6%, respectively. From 72 to 100 weeks of age, crossbreds produced more eggs per week than the superior parent White Leghorn (3.5 eggs for White Leghorn, 3.8 and 3.9 eggs for crossbreds). Heterosis for eggshell thickness ranged from 2.7 to 6.6% when using Beijing-You as the sire breed. No significant difference between reciprocal crosses was observed for the investigated traits, except for eggshell strength at 54 weeks of age. CONCLUSIONS The heterosis was substantial for egg weight and cumulative egg number, and increased with age, suggesting that non-additive genetic effects are important in crossbreds between the indigenous and elite breeds. Generally, the crossbreds performed similar to or even outperformed the commercial White Leghorns for egg production persistency.
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Affiliation(s)
- Aixin Ni
- State Key Laboratory of Animal Biotech Breeding, Key Laboratory of Animal (Poultry) Genetics Breeding and Reproduction of Ministry of Agriculture and Rural Affairs, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
- Animal Breeding and Genomics, Wageningen University and Research, P.O. Box 338, 6700 AH, Wageningen, The Netherlands
| | - Mario P L Calus
- Animal Breeding and Genomics, Wageningen University and Research, P.O. Box 338, 6700 AH, Wageningen, The Netherlands
| | - Henk Bovenhuis
- Animal Breeding and Genomics, Wageningen University and Research, P.O. Box 338, 6700 AH, Wageningen, The Netherlands
| | - Jingwei Yuan
- State Key Laboratory of Animal Biotech Breeding, Key Laboratory of Animal (Poultry) Genetics Breeding and Reproduction of Ministry of Agriculture and Rural Affairs, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Yuanmei Wang
- State Key Laboratory of Animal Biotech Breeding, Key Laboratory of Animal (Poultry) Genetics Breeding and Reproduction of Ministry of Agriculture and Rural Affairs, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Yanyan Sun
- State Key Laboratory of Animal Biotech Breeding, Key Laboratory of Animal (Poultry) Genetics Breeding and Reproduction of Ministry of Agriculture and Rural Affairs, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, 100193, China.
| | - Jilan Chen
- State Key Laboratory of Animal Biotech Breeding, Key Laboratory of Animal (Poultry) Genetics Breeding and Reproduction of Ministry of Agriculture and Rural Affairs, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, 100193, China.
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Mancinelli AC, Menchetti L, Birolo M, Bittante G, Chiattelli D, Castellini C. Crossbreeding to improve local chicken breeds: predicting growth performance of the crosses using the Gompertz model and estimated heterosis. Poult Sci 2023; 102:102783. [PMID: 37269793 PMCID: PMC10242636 DOI: 10.1016/j.psj.2023.102783] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Revised: 05/02/2023] [Accepted: 05/13/2023] [Indexed: 06/05/2023] Open
Abstract
The present study aims to validate the Gompertz model to predict the growth performance of chicken crosses according to growth curve parameters of the parental lines and the estimated heterosis for each curve parameter. A total of 252 one-day-old chicks of both sexes belonging to 6 genotypes, including Ross 308, Sassò (SA), Bionda Piemontese (BP), and Robusta Maculata (RM), and the crosses between these local breeds and SA (BP × SA and RM × SA) were randomly allocated in 18 pens (3 pens/genotype) in mixed-sex groups (14 animals/pen; 7 females and 7 males). The individual body weight (BW) of all birds was recorded once a week from hatching until slaughtering (81 d for Ross 308; 112 d for SA, 140 d for the other genotypes). We drew up our final dataset with 240 birds (40 birds/genotype; 20 females and 20 males). The growth curve of each genotype was described using the Gompertz model, and the heterosis for each growth curve parameter was calculated as the difference between F1 crosses and the average of parental breeds. The predicted growth curve parameters were evaluated by cross-validation. The Gompertz model accurately estimated the growth curves of all the genotypes (R2 > 0.90). Heterosis was significant for almost all growth curve parameters in both crosses (P < 0.05). Heterosis ranged from -13.0 to +11.5%, depending on parameters, but varied slightly between the crossbreeds (BP × SA and RM × SA). The predicted values of adult BW, weight at the inflection point, and maximum growth rate were overestimated for BP × SA and underestimated for RM × SA, with a mean error between observed and predicted values <│2.7│% for all the curve parameters. In conclusion, the growth performance of chicken crosses between local breeds and commercial strains can be accurately predicted with Gompertz parameters of the parental lines adjusting for heterosis.
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Affiliation(s)
- Alice Cartoni Mancinelli
- Department of Agricultural, Environmental and Food Science, University of Perugia, 06121 Perugia, Italy
| | - Laura Menchetti
- School of Biosciences and Veterinary Medicine, University of Camerino, 62024 Matelica, Macerata, Italy
| | - Marco Birolo
- Department of Agronomy, Food, Natural Resources, Animal and Environment (DAFNAE), University of Padova, 35020 Legnaro, Padova, Italy.
| | - Giovanni Bittante
- Department of Agronomy, Food, Natural Resources, Animal and Environment (DAFNAE), University of Padova, 35020 Legnaro, Padova, Italy
| | - Diletta Chiattelli
- Department of Agricultural, Environmental and Food Science, University of Perugia, 06121 Perugia, Italy
| | - Cesare Castellini
- Department of Agricultural, Environmental and Food Science, University of Perugia, 06121 Perugia, Italy
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Buranawit K, Laenoi W. Genetic parameters for production traits in F1 reciprocal crossbred Chee Fah and Fah Luang chickens. ANIMAL PRODUCTION SCIENCE 2022. [DOI: 10.1071/an20155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
ContextRecently, Chee Fah and Fah Luang chickens have been registered as a black-bone native chicken in Thailand. Only a few studies revealed genetic information about them. No publication has reported any data related to their cross-mating, particularly, genetic parameters.AimsThis study aimed to estimate genetic parameters for production traits of F1 generation of reciprocal crossbred Chee Fah and Fah Luang chickens.MethodsA dataset of production traits of two crossbred groups was used in the present study. Effects of breed, month-day of incubation and sex were tested at P<0.05. Genetic parameters were estimated using the restricted maximum likelihood method with multi-trait animal model.Key resultsThe crossbred Chee Fah×Fah Luang was significantly heavier and consumed more feed than Fah Luang×Chee Fah (P<0.05). Male chickens had significantly better 20-week-old bodyweight, feed conversion ratio and average daily gain compared with females for both crossbred groups (P<0.05). The effect of month-day of incubation had a significant influence on production traits (P<0.05), except for day-old bodyweight. Heritabilities for production traits of crossbred chickens were low to high. The highest estimate was observed for day-old bodyweight (0.97), followed by feed intake (0.40), 20-week-old bodyweight (0.06), average daily gain (0.05) and feed conversion ratio (0.03), respectively. Both positive and negative genetic correlations were found among their production traits. Favourable relationships were found between average daily gain versus bodyweight and versus feed conversion ratio (rgg=0.99 and −0.90, respectively). Similarly, production traits showed phenotypic correlations in both directions, which ranged from −0.95 to 0.99.ConclusionsHeritability estimations for production traits were found in low to high magnitude. The desirable genetic relationships were found between feed conversion ratio and day-old bodyweight, 20-week-old bodyweight and average daily gain, and between 20-week-old bodyweight and average daily gain.ImplicationsThese findings could be considered as a source of genetic data for enhancing production traits of crossbred black-bone native chickens.
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Mai C, Wen C, Xu Z, Xu G, Chen S, Zheng J, Sun C, Yang N. Genetic basis of negative heterosis for growth traits in chickens revealed by genome-wide gene expression pattern analysis. J Anim Sci Biotechnol 2021; 12:52. [PMID: 33865443 PMCID: PMC8053289 DOI: 10.1186/s40104-021-00574-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Accepted: 02/21/2021] [Indexed: 11/18/2022] Open
Abstract
Background Heterosis is an important biological phenomenon that has been extensively utilized in agricultural breeding. However, negative heterosis is also pervasively observed in nature, which can cause unfavorable impacts on production performance. Compared with systematic studies of positive heterosis, the phenomenon of negative heterosis has been largely ignored in genetic studies and breeding programs, and the genetic mechanism of this phenomenon has not been thoroughly elucidated to date. Here, we used chickens, the most common agricultural animals worldwide, to determine the genetic and molecular mechanisms of negative heterosis. Results We performed reciprocal crossing experiments with two distinct chicken lines and found that the body weight presented widely negative heterosis in the early growth of chickens. Negative heterosis of carcass traits was more common than positive heterosis, especially breast muscle mass, which was over − 40% in reciprocal progenies. Genome-wide gene expression pattern analyses of breast muscle tissues revealed that nonadditivity, including dominance and overdominace, was the major gene inheritance pattern. Nonadditive genes, including a substantial number of genes encoding ATPase and NADH dehydrogenase, accounted for more than 68% of differentially expressed genes in reciprocal crosses (4257 of 5587 and 3617 of 5243, respectively). Moreover, nonadditive genes were significantly associated with the biological process of oxidative phosphorylation, which is the major metabolic pathway for energy release and animal growth and development. The detection of ATP content and ATPase activity for purebred and crossbred progenies further confirmed that chickens with lower muscle yield had lower ATP concentrations but higher hydrolysis activity, which supported the important role of oxidative phosphorylation in negative heterosis for growth traits in chickens. Conclusions These findings revealed that nonadditive genes and their related oxidative phosphorylation were the major genetic and molecular factors in the negative heterosis of growth in chickens, which would be beneficial to future breeding strategies. Supplementary Information The online version contains supplementary material available at 10.1186/s40104-021-00574-2.
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Affiliation(s)
- Chunning Mai
- National Engineering Laboratory for Animal Breeding and Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture and Rural Affairs, China Agricultural University, Beijing, 100193, China
| | - Chaoliang Wen
- National Engineering Laboratory for Animal Breeding and Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture and Rural Affairs, China Agricultural University, Beijing, 100193, China
| | - Zhiyuan Xu
- National Engineering Laboratory for Animal Breeding and Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture and Rural Affairs, China Agricultural University, Beijing, 100193, China
| | - Guiyun Xu
- National Engineering Laboratory for Animal Breeding and Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture and Rural Affairs, China Agricultural University, Beijing, 100193, China
| | - Sirui Chen
- National Engineering Laboratory for Animal Breeding and Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture and Rural Affairs, China Agricultural University, Beijing, 100193, China
| | - Jiangxia Zheng
- National Engineering Laboratory for Animal Breeding and Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture and Rural Affairs, China Agricultural University, Beijing, 100193, China
| | - Congjiao Sun
- National Engineering Laboratory for Animal Breeding and Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture and Rural Affairs, China Agricultural University, Beijing, 100193, China.
| | - Ning Yang
- National Engineering Laboratory for Animal Breeding and Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture and Rural Affairs, China Agricultural University, Beijing, 100193, China.
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Isa AM, Sun Y, Shi L, Jiang L, Li Y, Fan J, Wang P, Ni A, Huang Z, Ma H, Li D, Chen J. Hybrids generated by crossing elite laying chickens exhibited heterosis for clutch and egg quality traits. Poult Sci 2020; 99:6332-6340. [PMID: 33248549 PMCID: PMC7704758 DOI: 10.1016/j.psj.2020.08.056] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 08/03/2020] [Accepted: 08/15/2020] [Indexed: 02/08/2023] Open
Abstract
Crossbreeding advantage in hybrids compared with their parents, termed heterosis, has been exhaustively exploited in chicken breeding over the last century. Reports for crossbreeding of elite laying chickens covering rearing and laying period remain infrequent. In this study, resource populations of Rhode Island Red (RIR) and White Leghorn (WL) pure-bred chickens were reciprocally crossed to generate 4 distinct groups that were evaluated for prelaying growth, egg production, and egg quality. Birds monitored for prelaying growth consists of 105 (RIR), 131 (WL), 207 (RIR × WL) and 229 (WL × RIR), and 30 pullets from each group were evaluated. Egg laying records were collected from 102, 89, 147, and 191 hens in the 4 populations, respectively. In addition, expression of 5 candidate genes for egg production in the ovarian follicles was measured by RT-qPCR. Results showed that BW of hatched chicks in the WL line was higher than the other populations. However, the 2 crossbreds grew faster than WL purebred throughout the prelaying period. Low to medium heterosis was observed for BW and body length before the onset of lay. White Leghorn and the hybrids commenced laying earlier than RIR pullets and egg production traits were favorable in the crossbreds compared with purebreds. Heterosis for egg number and clutch size was moderate in WL × RIR but low in RIR × WL hens. Expression of antimullerian hormone gene was high in WL and RIR × WL hybrids, suggesting WL parent-specific enhancing dominant expression. Shell weight was higher in the crossbreds than purebreds at 52 wk of age, but RIR hens laid eggs with higher shell ratio than the other populations (P < 0.05). Conversely, WL and the hybrids had higher eggshell strength than RIR birds (P < 0.05). Eggshell strength was the only egg quality trait that showed heterosis above 10% in WL × RIR hybrids at 32 and 52 wk of age. White Leghorn × RIR hens demonstrated higher percent heterosis for economic traits than birds of the reciprocal hybrid. This means that RIR breed is a better dam than a sire line for growth, egg laying, and egg quality traits.
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Affiliation(s)
- Adamu M Isa
- Key Laboratory of Animal (Poultry) Genetics, Breeding and Reproduction, Ministry of Agriculture, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China; Department of Animal Science, Usmanu Danfodiyo University, Sokoto, Nigeria
| | - Yanyan Sun
- Key Laboratory of Animal (Poultry) Genetics, Breeding and Reproduction, Ministry of Agriculture, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Lei Shi
- Key Laboratory of Animal (Poultry) Genetics, Breeding and Reproduction, Ministry of Agriculture, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Linlin Jiang
- Key Laboratory of Animal (Poultry) Genetics, Breeding and Reproduction, Ministry of Agriculture, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Yunlei Li
- Key Laboratory of Animal (Poultry) Genetics, Breeding and Reproduction, Ministry of Agriculture, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Jing Fan
- Key Laboratory of Animal (Poultry) Genetics, Breeding and Reproduction, Ministry of Agriculture, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Panlin Wang
- Key Laboratory of Animal (Poultry) Genetics, Breeding and Reproduction, Ministry of Agriculture, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Aixin Ni
- Key Laboratory of Animal (Poultry) Genetics, Breeding and Reproduction, Ministry of Agriculture, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Ziyan Huang
- Key Laboratory of Animal (Poultry) Genetics, Breeding and Reproduction, Ministry of Agriculture, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Hui Ma
- Key Laboratory of Animal (Poultry) Genetics, Breeding and Reproduction, Ministry of Agriculture, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Dongli Li
- Beijing Bainianliyuan Ecological Agriculture Co., Ltd., Beijing 101500, China
| | - Jilan Chen
- Key Laboratory of Animal (Poultry) Genetics, Breeding and Reproduction, Ministry of Agriculture, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
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Glucose Tolerance and Plasma Non-Esterified Fatty Acid Levels in Chickens Selected for Low Body Weight, Red Junglefowl, and their Reciprocal Cross. J Poult Sci 2019; 56:245-252. [PMID: 32055221 PMCID: PMC7005393 DOI: 10.2141/jpsa.0180098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Responses of an individual to food deprivation, such as a 16-h fast, are complex, and are influenced by environmental and genetic factors. Domestication is an ongoing process during which adaptations to changing environments occur over generations. Food deprivation by their caretakers is less for domestic chickens than for their junglefowl ancestors. Unlike domestic chicken, the junglefowl adapted over generations to periods of food deprivation, which may be reflected in differences in metabolic responses to brief periods without food. Here, we compared the blood glucose and plasma levels of non-esterified fatty acids (NEFA) among four populations when deprived of feed for 16 h. The four populations included a domestic White Rock experimental line (LWS) maintained for generations under ad libitum feeding, adult red junglefowl (RJF), and a reciprocal cross of the lines. Although there were significant differences in adult (31-week) body weight between the RJF (683 g) and LWS (1282 g), with the weight of F1 crosses being intermediate, the amount of abdominal fat relative to body weight was similar for all populations. Patterns for blood glucose responses to a glucose bolus after a 16-h fast were similar for the initial and final points in the parental and cross populations. However, RJF reached their peak faster than LWS, with the reciprocal cross intermediate to the parental populations. Plasma NEFA concentrations were higher after the 16-h fast than in fed states, with no population differences for the fasting state. However, in the fed state, NEFA levels were lesser for LWS than for others, which was reflected further in percentage change from fed to fasted. This larger change in LWS suggests differences in mobilization of energy substrates and implies that during domestication or development of the LWS line, thresholds for responses to acute stressors may have increased.
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Implications of Gene Inheritance Patterns on the Heterosis of Abdominal Fat Deposition in Chickens. Genes (Basel) 2019; 10:genes10100824. [PMID: 31635393 PMCID: PMC6826362 DOI: 10.3390/genes10100824] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 10/05/2019] [Accepted: 10/17/2019] [Indexed: 12/23/2022] Open
Abstract
Heterosis, a phenomenon characterized by the superior performance of hybrid individuals relative to their parents, has been widely utilized in livestock and crop breeding, while the underlying genetic basis remains elusive in chickens. Here, we performed a reciprocal crossing experiment with broiler and layer chickens and conducted RNA sequencing on liver tissues for reciprocal crosses and their parental lines to identify inheritance patterns of gene expression. Our results showed that heterosis of the abdominal fat percentage was 69.28%–154.71% in reciprocal crosses. Over-dominant genes of reciprocal crosses were significantly enriched in three biological pathways, namely, butanoate metabolism, the synthesis and degradation of ketone bodies, and valine, leucine, and isoleucine degradation. Among these shared over-dominant genes, we found that a lipid-related gene, HMGCL, was enriched in these pathways. Furthermore, we validated this gene as over-dominant using qRT-PCR. Although no shared significant pathway was detected in the high-parent dominant genes of reciprocal crosses, high-parent dominant gene expression was the major gene inheritance pattern in reciprocal crosses and we could not exclude the effect of high-parent dominant genes. These findings suggest that non-additive genes play important roles in the heterosis of important traits in chickens and have important implications regarding our understanding of heterosis.
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Sutherland DAAT, Honaker CF, Dorshorst B, Andersson L, Brisbin IL, Siegel PB. Growth patterns for three generations of an intercross between red junglefowl and chickens selected for low body weight. J Anim Breed Genet 2018; 135:300-310. [PMID: 29926987 DOI: 10.1111/jbg.12336] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 05/23/2018] [Accepted: 05/25/2018] [Indexed: 11/30/2022]
Abstract
Growth is a complex and dynamic process that may be measured at a specific point or over a period of time. Compared was the growth of male and female chickens over a three-generation period. Involved were red junglefowl (RJF; Gallus gallus), a line of White Plymouth Rock chickens (LWS; Gallus gallus domesticus) selected for low body weight, and their reciprocal F1 and F2 crosses. In both sexes, Gompertz's description of growth showed that RJF had significantly lower asymptotes, earlier inflection points, and faster growth rates than LWS. Heterosis for these measures was positive for asymptote and negative for growth rate and inflection point. The RJF commenced egg production at a significantly younger age and lower body weight than LWS. Although F1 and F2 reciprocal crosses were similar for body weight and for age at first egg, the F1 reciprocal crosses began lay at significantly younger ages than the F2 crosses and parental lines. When viewed on a physiological basis where age and body weight were simultaneously standardized, both parental lines and reciprocal F1 and F2 crosses had differing rapid and lag growth phases. Overall, sexual dimorphism increased in all populations from hatch to sexual maturity. The LWS males had a longer growth period consistent with their female counterparts who became sexually mature at older ages. Comprehensively, these results indicate additive and nonadditive genetic variation for distinct growth patterns and changes in resource allocation strategies over time.
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Affiliation(s)
| | | | - Ben Dorshorst
- Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA, USA
| | - Leif Andersson
- Department of Medical Biochemistry and Microbiology, Uppsala Biomedical Center, Uppsala University, Uppsala, Sweden
| | - I Lehr Brisbin
- Savannah River Ecology Laboratory, Odum School of Ecology, University of Georgia, Aiken, SC, USA
| | - Paul B Siegel
- Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA, USA
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