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Importance of Heterosis in Animals: A Review

January 2015

Authors:

Subha Ganguly

Government of West Bengal

Praveen KUMAR Praveen

Arawali Veterinary College, RAJUVAS, Bikaner, Rajasthan, India.

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Hybrid vigor or heterocyst is the phenomenon in which progeny of crosses between inbred lines or purebred populations are better than the expected average of the two populations or lines for a particular trait. Utilization of heterocyst (hybrid vigor) is the exclusive goal of crossbreeding. The amount of heterosis maintained in a herd depends on the type of crossbreeding system selected. Hybrid vigor includes greater viability, faster growth rate, greater milk, egg and wool production in animals. Heterocyst is an unexpected deviation from the average of the two parental lines. The cause of heterosis the non-additive gene action (dominance, Overdominance and epistasis).No heterosis is observed for traits governed by additive gene action. Heterosis can occur for a wide variety of performance traits. The traits showing heterosis are called as heterotic traits. However, it tends to be greatest for traits with low heritability and least for traits with high heritability. Traits of low heritability (reproductive traits) are generally most benefited from heterosis. They can be improved through the adequate use of crossbreeding systems.

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International Journal of Advanced Engineering Technology and Innovative Science (IJAETIS)

Available online at: www.ijaetis.org

Volume1, Issue 1, Page No: 01-05

November-December 2015

ISSN:2455-1651

Corresponding author: Rajesh Wakchaure www.ijaetis.org

Importance of Heterosis in Animals: A Review

Rajesh Wakchaure1, Subha Ganguly2*, Praveen Kumar Praveen3, Subhash Sharma4, Avinash Kumar5, Tanvi Mahajan6 and Kausar Qadri7

1Associate Professor, Department of Animal Genetics and Breeding, 2Associate Professor and Head, Department of Veterinary Microbiology,

3Assistant Professor, Department of Veterinary Public Health and Epidemiology, 4Assistant Professor, Department of Veterinary Parasitology,

5Assistant Professor, Department of Veterinary Pharmacology and Toxicology, 6Assistant Professor, Department of Veterinary Anatomy and

Histology, 7Assistant Professor, Department of Veterinary Medicine, Arawali Veterinary College (Affiliated with Rajasthan University of Veterinary

and Animal Sciences, Bikaner), N.H. – 52 Jaipur Road, V.P.O. Bajor, Dist. Sikar, Pin – 332001, Rajasthan, India

ganguly38@gmail.com

ABSTRACT

Hybrid vigor or heterocyst is the phenomenon in which progeny of crosses between inbred lines or purebred populations

are better than the expected average of the two populations or lines for a particular trait. Utilization of heterocyst (hybrid

vigor) is the exclusive goal of crossbreeding. The amount of heterosis maintained in a herd depends on the type of

crossbreeding system selected. Hybrid vigor includes greater viability, faster growth rate, greater milk, egg and wool

production in animals. Heterocyst is an unexpected deviation from the average of the two parental lines. The cause of

heterosis the non-additive gene action (dominance, Overdominance and epistasis).No heterosis is observed for traits

governed by additive gene action. Heterosis can occur for a wide variety of performance traits. The traits showing

heterosis are called as heterotic traits. However, it tends to be greatest for traits with low heritability and least for traits

with high heritability. Traits of low heritability (reproductive traits) are generally most benefited from heterosis. They can

be improved through the adequate use of crossbreeding systems.

Keywords: crossbreeding, heterosis, crossbred

INTRODUCTION:

In 1914 Professor Shull proposed for the first time the

word ‘heterosis’ (Shull, 1914). The term used to measure

crossbred performance compared to the parental average

is hybrid vigour also known as heterosis. Hybrid Vigour

measures the ability of crossbred offspring to outperform

the expected abilities transmitted by their parents. Since

the goal of crossbreeding is to combine two, three or four

different breeds in order to achieve some desirable trait

from each different breed, Heterosis refers to the

superiority of the crossbred animal relative to the average

of its straightbred parents. Heterosis may be positive or

negative depending upon the trait. Positive heterosis is

called as hybrid vigour. Heterosis is typically expressed in

percentage improvement in the trait of interest. Heterosis

results from the increase in the heterozygosity of a

crossbred animal’s genetic makeup. Heterosis is the result

of gene dominance, overdominance and epistasis.

Heterosis dependent on an animal having two different

copies of a gene. The level of heterozygosity an animal

has depends on the random inheritance of copies of genes

from its parents. The exploitation of heterosis most

important reason for utilising cross breeding in animals

along with the exploitation of additive effects from

improved purebred animals. Heterosis arises from the

effects of gene combinations means effects of pairs of

genes (Cassell, 2007). Heterotic effects in the crossbred

progeny depends upon the differences in the frequencies

of the different alleles at each locus that contributes to the

trait (McAllister, 2002), larger these differences greater

the heterozygosity and the heterosis effects. Crossbred

animals often show increased vitality and performance.

This is known as heterosis or hybrid effect. The Sahiwal -

Friesian cross resistant to most of the common cattle

diseases and has a good milk production. A criss-cross

breeding programme is suggested to maintain the hybrid

vigour in the offspring of crossbred animals. In general,

animals that are crosses of unrelated breeds, such as

Angus and Brahman exhibit higher levels of heterosis due

to more heterozygosity than crosses of more genetically

similar breeds such as a cross of Angus and Hereford. The

genetic basis for heterosis is the opposite of the origin of

inbreeding depression. Crossbreeding cause more gene

pairs to be heterozygous. Breeds that are genetically

diverse tend to cause more heterozygosity and more

heterosis when crossed. Heterozygosity will result in

better performance if there is non-additive gene action

(dominance, overdominance and epistasis). Crossbreeding

has been shown to be an efficient method to improve

reproductive efficiency and productivity and fitness in

beef cattle. Crossbred (F1, F2 and F3) females had calves

that weighed an average of approximately 5.5 lb. more

than purebred calves at birth(Gregory et al., 1991).Cross-

breeding within species leads to offspring that are

genetically fitter than their parents (Darwin, 1876).

Rajesh Wakchaure, et al. International Journal of Advanced Engineering Technology and Innovative Science (IJAETIS)

Volume 1, Issue 2; November-December- 2015; Page No. 01-05

Page2

Lippman and Zamir (2006) described offspring from

parents with greater genetic diversity are genetically fitter

than offspring of parents with less diversity. Cross breeds

dogs are faster learners than pure breeds (Ennik et al.,

2006). The increase in corn production (Duvick, 2001),

milk production (Ahlborn-Breier and Hokenboken,1991)

and meat production (Sellier, 1976) possible with cross-

breeding. 16% increase in the pounds of calf weaning

weight per cow exposed above the average of the parent

breeds (Ritchie et al., 1999). Crossbreeding as a mating

system optimizes the additive genetic and non-additive

(heterotic) breed effects of Bos taurus and Bos indicus

cattle in sustainable breeding systems (Gregory and

Cundiff, 1980). The reason for crossbreeding is to increase

the dairy cattle production through new combinations of

genes in different breeds (Simm, 2000). Heterosis is a

result of the non-additive gene effect, dominance and

epitasis along with differences in the frequencies of the

different alleles at each locus. The total genetic makeup of

crossbreds can include additive effects, dominance,

maternal effects, maternal heterosis and recombination

effects. Which effect that may be present is dependent of

the particular kinds of crosses involved (McAllister,

2002). The amount of heterosis expressed for a given trait

is inversely related to the heritability of the trait.

Generally, heterosis generates the largest improvement in

lowly heritable traits. Moderate improvements due to

heterosis in moderately heritable traits. Little or no

heterosis is observed in highly heritable traits. The highest

level of heterosis is most commonly seen in functional

traits affecting reproduction, survival and overall fitness.

These traits often show at least 10% heterosis and low

heritability .Production traits affecting milk yield and

growth show about 5% heterosis and a moderately high

heritability (Hansen, 2006). The expected level of

heterosis is difficult to predict and it differs depending on

the type and number of breeds in the crossbreeding system

(Sorensen et al., 2008). Crossbreeding can also cause

negative effects and one of them is recombination loss. It

is caused by separation of favorable gene combinations

that are accumulated in the parental breeds.

Recombination loss can be difficult to estimate although it

has been seen to reduce the level of heterosis (Cassell and

McAllister, 2009). The highest level of individual

heterosis is always seen in the F1 generation, but

unfortunately the level always decreases in subsequent

generations. If F1 cattle are crossed to produce the second

generation (F2), heterosis is halved compared to the level

in the F1. It continues to be halved in every following

generation of backcrossing to the parent breeds (Simm,

2000). An alternative to maintain the level of heterosis

after creating a two way cross is to produce a three way

cross because in the third generation (F3) or fourth

generation (F4) there is no further decrease in heterosis, as

long as no inbreeding exists. The level of heterosis

changes depending on the number of breeds in the cross

(Sorensen et al., 2008). Heins (2007) reported that the

Brown-Swiss-Holstein crossbreds had only a slightly

reduced milk yield along with a significantly higher yield

of milk components, fewer days open and a low number

of somatic cells compared to purebred Holstein. Due to

heterosis, crossbred Jersey-Holsteins had superior

performance compared with purebred Holsteins for milk

yield, fat and protein (Bryant et al., 2007). Jersey-Holstein

crossbred cows maintained body condition score and

hence had lower levels of live weight loss after calving

(Heins et al., 2008). Cattle and Swine species dependant

heavily on heterosis to improve productivity and

efficiency of production (Hansen, 2006). In temperate

countries, crossbreeding has been widely used in pigs and

poultry to exploit both breed differences and heterosis .

Crosses between temperate and tropical breeds have often

shown large amounts of heterosis, because of the large

genetic distance between them. Heterosis is more

important under a suboptimal (poor) than in optimal

(good) environment. Thus, heterosis is the complement of

inbreeding depression and usually appears in traits that

show depression of performance under inbreeding.

Reproductive traits in dairy cattle are usually very

sensitive to inbreeding depression and thus cross breeding

or out-crossing can show large heterotic effects. F1 crosses

probably take the advantage of hybrid vigor that arises by

crossing two genetically distant populations. Second-

generation crosses suffer reduction in hybrid vigor by half

than first generation crosses due to segregation and

recombination losses (Sendros, 2002). Loss of hybrid

vigor is the genetic factor for reduced performances in F2

crosses, poor selection standards to select F1 bulls for inter

se mating greatly contributed drop in the lifetime

performances. F1 crosses yielded more milk (147%), were

milked for more days and had shorter calving interval

(McDowell, 1988). Studies in France have shown that the

F1 crosses tend to be above median average of the two

breeds for milk but closer to the Normande for

components (Hansen, 2010). A three way cross will

maintain hybrid vigor in later generations at 86%, while a

2 way cross will at 67% and a 4 way cross at 93%

(Hansen, 2006). Three way crosses offer an increased

heterosis along with longevity, protein and fat

components, and calving ease (Snowdon, 2010). In a three

way cross program the F1 and F2 generations are both able

to maintain 100 % hybrid vigor compared to a two way

cross program where hybrid vigor drops to 50 % in the F2

generation (Pro Cross, 2009). Heterosis is utilized most

commonly in beef cattle through crossbreeding. Heterosis

in beef cattle can produce calves with enhanced

reproductive, survival, longevity (Dhuyvetter, 1998),

fertility, growth, meat quality (Peck, 2009) and disease

Rajesh Wakchaure, et al. International Journal of Advanced Engineering Technology and Innovative Science (IJAETIS)

Volume 1, Issue 2; November-December- 2015; Page No. 01-05

Page3

resistance traits (Dandapat, 2009). The benefits of

heterosis on beef herd quality and consequently

profitability (Anderson, 1990) and herd management

programs (Brown, 2010). Heterosis achieved through

continuous crossbreeding can be used to increase weight

of calf weaned per cow exposed to breeding by 20 %

(Gregory and Cundiff, 1980). Heterosis can also increase

longevity of cows by 1.3 yr and can increase the total calf

weight weaned per cow by 30 % over the life span of a

dam (Cundiff et al., 1992). Loss of heterozygosity in inter

se mated populations does not occur if inbreeding is

evaded (Dickerson, 1973). Cows exhibit more hybrid

vigour in first and second parities than at later parities

(Cundiff et al., 1974). Herefords (Gregory and Cundiff,

1980) among the beef breeds and Holstein (McDowell,

1982) among the dairy breeds appear to have slightly

higher than average heterosis (Sorensen et al., 2008).

Heterosis has been utilized in beef production to enhance

fertility, longevity, growth and meat quality traits in

commercial herds through various cross-breeding systems.

Application of crossing systems such as three or four-

breed crosses would be very difficult, so rotational

crossbreeding systems are required to exploit breed and

heterotic effects. These schemes allow commercial

farmers to produce crossbred female replacements from

their own herds. Holstein-Friesian x Jersey crosses show

higher net income than purebred HF and Jersey cows, so

that dairy farmers mate their cows to bulls from another

breed to generate crossbred replacements with the aim of

exploiting the effects of breed and heterosis (Lopez-

Villalobos, 1998). In rotational systems heterosis is

retained at high levels, 66% in two–breed rotation, 86% in

three–breed rotation (Handley, 2001)

Measurement of Heterosis:

Percent heterosis can be calculated as:

% Heterosis = [Mean of F1 progeny- mean of parent breed] x 100

Mean of parent breed

Heterosis in F1= Mean of F1 progeny- mean of parent breed

Heterosis in F2 =1/2 heterosis in F1

Types of heterosis

There are three main types of heterosis

1) Individual heterosis: The improvement in

performance by the individual crossbred animal above

average of its parents. Examples of individual heterosis

are increased weaning weight, yearling weight and carcass

traits.

2) Maternal heterosis: Maternal heterosis is the

advantage of the crossbred mother over the average of

purebred mothers. Examples of maternal heterosis are

younger age at puberty, increased calving rate, increased

survival of her calf to weaning, pounds of calf produced in

her lifetime higher weaning weights, greater longevity in

the dam and other reproductive traits.

3) Paternal heterosis: Paternal heterosis is the advantage

of a crossbred sire over the average of purebred sires

(Buchanan, 2011). The improvement in productive and

reproductive characteristics of the bull. Examples of

paternal heterosis are reduced age at puberty,

improvements in scrotal circumference, improved sperm

concentration, increased pregnancy rate and weaning rate

when mated to cows.

Genetic basis of heterosis

There are three theories of heterosis. 1. Dominant theory

2. Over Dominance theory

3. Epistasis theory

1. Dominant theory: Superiority of hybrids to the

suppression of undesirable recessive alleles from

one parent by dominant alleles from the other

parent. The dominance hypothesis was first

expressed by the geneticist Charles Davenport

(1908)

2. Over Dominance theory: Heterozygote advantage

to the survival of many alleles those are recessive

and harmful in homozygotes. The overdominance

hypothesis was developed independently by East

(1908) and Shull (1908).

3. Epistasis theory: It postulates that gene

interactions are responsible for heterosis. The

epistasis is a phenomenon of interacting genes

which are not alleles.

Conclusion

The main benefit of crossbreeding is heterosis, which is the

improvement in genetic level in a hybrid offspring above

the average of the parent breeds. Crossbreeding schemes is

most profitable breeding strategy can assist improve

Rajesh Wakchaure, et al. International Journal of Advanced Engineering Technology and Innovative Science (IJAETIS)

Volume 1, Issue 2; November-December- 2015; Page No. 01-05

Page4

growth, reproduction, production and maternal traits, health

and overall fitness by taking advantage of heterosis, which

results when animals from diverse backgrounds are

crossed. Inbreeding must be avoided to retain high levels of

heterozygosity and heterosis in composite breeds. The

challenge of maintaining heterosis and minimizing

inbreeding can only be met using large populations of

cattle. If no inbreeding is practiced, the heterosis is retained

in composites for several generations. F2 crosses are not

appropriate genotype of choice for dairy production

because continuous reduction in hybrid vigor. Traits of low

heritability such as fertility, milk yield and longevity are

difficult to enhance through pure breeding but are greatly

enhanced through crossbreeding leading to improvements

in survival, reproductive efficiency and growth rates. The

successful exploitation of heterosis depends upon how

superior the crosses are over the purebreds and cost of

replacement of purebred stock, therefore it is normally

practiced in poultry, swine and sheep where the fertility is

high and the cost of replacement of purebred stock is

essential.

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Article

Oct 2021

Data of 651 lambs (68 Romanov, 49 Rahmani, 151 [♀1/2 Rahmani X ♂1/2 Romanov) and 383 (♀3/4 Rahmani and 1/4♂ Romanov]) were collected from Mehalet Mousa Farm, belonging to Animal Production Research Institute from the period of 2009 to 2016 to estimate phenotypic and genetic parameters. The traits studied were birth weight (BW), body weight at four week (BW4), body weight at eight weeks (BW8) and body weight at twelve weeks (BW12) or weaning weight. Least squares analysis of variance shows significance of the effects of breed groups, gender of lambs, birth type; month of birth and year of birth on all traits studied. Rahmani lambs had heavier BW, BW4, BW8 and BW12 while Romanov lambs had the lowest ones. The first generation (♀1/2 Rhamani X ♂1/2 Romanov) had heavier body weights than Romanov and the second generation (♀3/4 Rahmani X ♂1/4 Roamnov). Gender of lambs had highly significant effect on body weights. Males were significantly (p < 0.01) heavier than females for all traits studied. Least square means of BW, BW4, BW8 and BW12 for single lambs were 2.69, 10.43, 13.53 and 16.10 kg, respectively. Least square means of BW, BW4, BW8 and BW12 for twin lambs were 2.50, 9.37, 12.5 and 15.16 kg, respectively, while least square means of BW, BW4, BW8 and BW12 for triple lambs were 2.09, 7.86, 10.83 and 13.67 kg, respectively. Estimates of direct heritability measured by single trait animal model were 0.14, 0.23, 0.25 and 0.26 for BW, BW4, BW8 and BW12, respectively, and the corresponding measured by multi trait animal model were 0.17, 0.24, 0.32 and 0.36 for the same traits, respectively. All genetic and phenotypic correlations among different traits studied are positive and significant.

Morphometric measurements of calves of beef cattle from different genetic groups up to one year of age

Article

Full-text available

Sep 2021
SCI AGR

Heterosis plays an important role on yield and profitability of beef production systems. This study evaluates the morphometrics of purebred Nellore (N) and Charolais (C) animals and of the second (G2) and third (G3) generations of their alternating crosses, regarding the effects of genetic group and heterosis from birth to 365 days of age. The experiment comprised 159 calves (C = 29, N = 22, G2-3/4C 1/4N = 21, 3/4N 1/4C = 9, G3-5/8C 3/8N = 44 and 5/8N 3/8C = 34). The foreshank girth (FG), thoracic girth (TG), body length (BL), and hip height (HH) were measured after birth, and at 63, 210, and 365 days of age, and the total increases were calculated. The Charolais animals had greater FG, TG, and BL values than Nellore, while the latter had greater HH. For the offspring generations, the predominance of Charolais genes in the genotypes resulted in greater measurements for FG and TG in G2, whereas the predominance of Nellore genes resulted in higher HH values in both generations. The crossbred animals had greater values for all measurements than the purebreds, with more significant differences in FG, TG, and BL compared to Nellore purebreds and in HH compared to Charolais. Charolais animals show higher values for muscularity; while, Nellore animals are taller. Crossbred animals show greater development compared to purebreds, indicating a significant effect of heterosis.

Technological Advances for Sustainable Livestock Production

Chapter

Aug 2021

There are exponential growth demands for animal products with the increasing population, which has proposed changes in the livestock sector. This chapter discusses the environmental problems that threaten the sustainability of animal production systems, and evaluates different technologies to solve this issue. Artificial insemination (AI) and crossbreeding are used to maintaining the sustainability of animal production systems for decades and they are still the most popular method until now. Modern technologies have been developed recently, such as transgenic animals or developing environmental-friend diets for livestock. In addition, the concept of the farm is modified as precision livestock farming (PLF) is developed. In order to have a sustainable agricultural environment, innovation must be placed in the highest priority in the livestock industry.

Avanços no melhoramento genético de ovinos da raça Santa Inês

Article

Full-text available

Dec 2020

For decades, the principles of genetic improvement have been successfully applied in the production of different livestock species. This success is largely due to the development of statistical methods, computational tools and molecular biology. In general, the production chains which have invested the most in genetic improvement are the ones that developed the most and are providing the greatest economic return today. Sheep farming represents one of the main livestock activities responsible for the production of animal protein in the world. However, most of the sheep flocks, mainly in developing countries, still do not participate in breeding programs. As a result, the economic potential that the sheep farming may achieve is less used, once the growing demand for sheep farming products are coming from consumers of different cultures and social levels. In Brazil, the Santa Inês native sheep breed is considered to have the greatest potential to meet the demands of the consumer market for quality and quantity of sheep meat. This breed has attributes that set it apart from other native and exotic breeds raised in the country. However, due to the low structure of the Brazilian sheep industry and the lack of sheep breeding programs in Brazil, the sheep meat production in the country is insufficient even to meet the domestic demand. In an attempt to solve this situation, several initiatives have already been taken, in particular, within the scope of research. Those initiatives represent efforts to promote the production of sheep meat using native genetic resources, with emphasis on the Santa Inês breed. However, there is still a need for greater investments on the part of the competent authorities, researchers and producers in order to enable the practical application of the results of the research, especially those focused on the genetic improvement of sheep flocks.

Breed and age effects on concentration of adiponectin and reproductive performance in Anglo Nubian, Etawah grade and its crossbred bucks

Article

Full-text available

Feb 2021

Hafizuddin, Karja NWK, Praharani L, Setiadi MA. 2021. Breed and age effects on concentration of adiponectin and reproductive performance in Anglo Nubian, Etawah grade and its crossbred bucks. Biodiversitas 22: 1112-1119. The purpose of this study was to evaluate the effect of differences in breed and age on reproductive performance and adiponectin and testosterone production in Anglo Nubian, Etawah grade, and crossbred (Anpera) bucks. A total of 12 bucks with four individuals of each breed were used. This study collected five data points from each buck regarding adiponectin, testosterone, and reproductive performance (libido and semen characteristics). Data were analyzed with factorial analysis of variance and Duncan's test. The result shows that adiponectin concentration between breeds was significantly different (P <0.01). There were also significant differences (P<0.05) in adiponectin concentrations based on buck age. There were also significant interactions with adiponectin concentrations (P <0.01). Furthermore, testosterone concentrations showed significant differences based on breed (P <0.05) and age (P <0.05). There were also significant age-breed interactions affecting testosterone concentrations (P <0.01). Libido and semen characteristics had no significant differences based on breed and age group, and no significant age-breed interactions (P> 0.05). The heterosis effect on adiponectin concentration (48.05%), testosterone concentration (27.68%), libido (-0.61%), semen volume (-1.93%), sperm motility (0.49%), sperm normal morphology (0.18%), and sperm concentration (0.00%) was measured. In conclusion, there is a significant effect of breed, age, and age-breed interactions on the concentration of adiponectin and testosterone in bucks, and both of these variables have a high heterosis effect on crossbred bucks.

The Relative Superiority of Crossbred Using Friesian Holstein Hybrid Cement Bull to Local Ongole Hybrid Cattle

Article

Jun 2020

The purpose of this study was to analyze the relative superiority of crossbred to local Ongole hybrid (PO) cattle. This research was carried out for 18 months in the Konawe Selatan, and Kolaka Timur Regency, Southeast Sulawesi Province. The number of cows used was 48 cows, and the cement used was Friesian Holstein Hybrid (PFH) Cement and Ongole hybrid (PO) Cows from BBIB Lembang. Data were analyzed by the general linear model (General Liner Model) with the source of diversity was genotype and sex of calf. Based on the results of the study concluded that the crossbred calf has a relatively high relative advantage over local Ongole hybrid cattle with an average value of 7.76-11.28%. The crossing of Friesian Holstein Hybrid (PFH) cows with Ongole hybrid (PO) parents resulted in offspring with PFPO genotype with an average relative superiority value (for all parameters) of 11.28%, higher than the PFS genotype of 7.65% and PFL of 9.60%. The Result of this crossing increases meat production, and it is recommended to crossbreed PFH cows with PO mothers; however, they still consider their suitability to the local environment and the purity of local PO cows.

Relationship between heterosis, weight gain, and body measurements of Nellore and Charolais calves

Article

Full-text available

Dec 2020

The objective of this work was to assess the effect of genetic group and heterosis on the relationship between body weight and morphometric measurements, in purebred and crossbred animals from the second (G2) and third (G3) generations of Nellore and Charolais calves. Body weight (BW), average daily weight gain (ADG), foreleg circumference (FC), thoracic girth (TG), body length (BL), and croup height (CH) were measured at birth and at 63, 210, and 365 days of age in animals from G2 and G3. Charolais animals were superior to Nellore ones for gains BW, ADG, BL, and TG, as well as for the ratio between BW gain and CH gain; Nellore animals were superior for CH gains. Crossbred animals of both generations were superior to the purebred animals for gains of BW, BL, and CH. In G2, the predominance of Charolais genes resulted in greater gains of BW, ADG, FC, and TG. The G3 animals were superior to the purebred animals for ADG, FC, and TG. No differences were found for the ratio between gains of weight and morphometric measurements. Heterosis and complementarity are apparent for weight and body measurements of crossbred calves from rotational crossings.

The formation of hybrid fish derived from hybridization of Megalobrama amblycephala (♀) × Siniperca chuatsi (♂)

Article

Oct 2021
AQUACULTURE

Crossbreeding has been conducted in many fish species. However, crosses between distant relatives that may result in higher levels of heterosis are hard to conduct due to reproductive isolation. In this study, diploid hybrids (BM) of blunt snout bream (Megalobrama amblycephala, BSB, ♀, order Cypriniformes, 2n = 48) × mandarin fish (order Siniperca chuatsi, MD, ♂, Perciformes, 2n = 48) were successfully produced. BM possessed 48 chromosomes from BSB. The body colour of BM (silver grey with many black spots) was different from that of BSB (silvery white) and MD (yellow with black stripes). The body shape of BM (small head with a slender body) was different from that of BSB (small head with a high back) and MD (body larger and flatter). We confirmed successful hybridization with microsatellite DNA markers and analysed the 5S rDNA patterns among the parental and hybrid lines. BM inherited its 5S rDNA entirely from the female parent (BSB). This study will provide a foundation for fish crossbreeding, and the successful hybrids in this study will potentially be an excellent commercial variety.

Interspecific hybridization between Patinopecten yessoensis (♀) and P. caurinus (♂) with heterosis in growth and temperature tolerance

Article

Sep 2021
AQUACULTURE

Hybridization is a powerful tool for improving productivity and profitability in aquaculture. To determine the performance characteristics of Patinopecten scallop hybrids, complete diallel hybridizations were carried out between Yesso scallops (P. yessoensis) and Weathervane scallops (P. caurinus) (Py♀ × Pc♂; Pc♀ × Py♂), together with intraspecific scallops P. yessoensis (Py♀ × Py♂) and P. caurinus (Pc♀ × Pc♂). The Pc♀ × Py♂ cohort only survived until 21 days after fertilization, while the Py♀ × Pc♂ cohort outperformed both purebred parental cohorts in larval, juvenile and adult growth periods with higher growth and survival rates. In particular, the growth rate of the Py♀ × Pc♂ cohort was significantly higher than that of the parental scallops at the adult grow-out stage. Compared with those in the Yesso scallops, the production traits in the Py♀ × Pc♂ cohort were increased by 16.43% in shell height and 26.87% in whole body weight, with heterosis of 21.6 and 34.9, respectively. Moreover, the survival rate of Py♀ × Pc♂ cohort adult hybrids (46.2 ± 3.2%) was notably higher than that of Yesso scallops (28.5 ± 4.5%) and Weathervane scallops (18.4 ± 5.2%) after thermal duress in summer and cold endurance in winter, showing significantly higher heterosis (97.0). Nuclear sequence (internal transcribed spacer) and mitochondrial DNA sequence (16S rDNA) analyses confirmed that the derived hybrid adults (Py♀ × Pc♂) were true hybrids between the two Patinopecten scallops. Our data presented evidence that artificially interspecific hybridization between P. yessoensis and P. caurinus was experimentally possible and achieved considerable heterosis of the Py♀ × Pc♂ cohort in growth performance and temperature tolerance. The hybrid adults (Py♀ × Pc♂) may provide valuable germplasm resources for increasing scallop production and support the development of strategies for long-term healthy sustainable aquaculture.

Mechanisms of Inbreeding Depression and Heterosis for Profitable Dairying

Article

Full-text available

Bennet G Cassell

Genes in diploid organisms operate singly, in pairs, and in conjunction with genes at other locations throughout the nuclear DNA. Inbreeding depression and heterosis arise from the effects of gene combinations, that is, the effects of pairs of genes. Gene pairs are unique characteristics of individuals that are broken down and reformed each generation. This basic biological fact, introduced to many of us in high school biology, is the foundation of everything there is to say about this topic. Very few topics are so well rooted in a simple process. Simplicity suffers, however, under real-world challenges of combining breeds or selecting to improve within a pure breed under a multi-trait breeding objective. This paper attempts to explain in a rudimentary way the ways in which genes interact, transmit, and recombine and the implications of those processes to breeding options available to dairy farmers. Mechanisms of inbreeding Inbreeding results from matings between related parents. Because breeding populations have finite size and long pedigree histories, mild inbreeding always exists by this definition. A more practical working definition of inbreeding is mating of parents more related than one would expect by chance alone. High levels of inbreeding are difficult to achieve in species where "selfing" is not possible. A 35-year project at the Beltsville Agriculture Research Center between 1912 and 1949 produced one dairy cow with an inbreeding coefficient of over 75%, the highest ever recorded for bovines under experimental conditions. A single generation of mating between this cow and an unrelated sire would break down all of the inbreeding in the dam. Extreme inbreeding is difficult to achieve and easy to eliminate – if you have access to an unrelated mate. Selection toward a single breeding objective can increase inbreeding, even in large populations. U.S. Holsteins have been under effective selection pressure for higher production and improved type since mid-1960. From 1982 until 2004, average inbreeding in a pedigree-recorded population of over 1,000,000 Holsteins increased from 1% to 5%. These figures may well understate actual inbreeding, as estimates are relative to a 1960 pedigree base and some pedigree information is missing in this population grade and registered animals.

Heterosis for Lifetime Production in Hereford, Angus, Shorthorn, and Crossbred Cows

Article

Full-text available

Sep 1992

The effects of maternal heterosis and maternal and grandmaternal breed effects on cumulative lifetime number and weight of calves weaned per cow entering the breeding herd were evaluated for 172 reciprocal crossbred and 156 straightbred cows of the Hereford, Angus, and Shorthorn breeds. Cows born in 1960 and 1961 were developed and mated to calve first at 3 yr of age and those born in 1962 and 1963 at 2 yr of age. Performance under actual culling of cows nonpregnant in two consecutive years and imposed culling of any nonpregnant cows were analyzed. Reproductive rates and weaning weight per calf and per cow exposed increased (P less than .05) as cows advanced from 2 through 5 yr of age, peaked at ages 5 through 9 yr, and decreased from 9 through 12 yr. Effects of heterosis did not interact (P greater than .05) with age at first calving management. During the 12-yr span in the 2-yr-old first-calving management system, crossbred cows produced nearly one more calf than straightbred cows under the actual culling policy (.97 calves, P less than .10) and .82 more calves (P less than .10) if all nonpregnant cows were culled. Corresponding cumulative calf weight weaned was 272 kg (P less than .01), or 25% more, and 232 kg (P less than .01), or 30% more, for crossbred cows than for straightbred cows. The 12-yr cumulative calf weight weaned by straightbred Angus cows exceeded that of Shorthorn cows (P less than .05) and tended to be greater than that of Hereford cows.

Inbreeding in Corn

Article

Jan 1908

E.M. East

The basis of crossbreeding in pigs; A review

Article

Sep 1976
Livest Prod Sci

Pierre Sellier

A survey of the different parameters involved in crossbreeding is given following the analysis of Dickerson (1969). The genetic gain resulting from crossbreeding has a double origin: complementarity and heterosis. The practical importance of these two advantages is evaluated in swine. Average individual (H1) and maternal (HM) heterosis effects on main performance traits are derived from experimental estimates summarized in graphs; the expected fraction of HI and HM utilized in some crossing plans is given. It appears that heterosis accounts for the major part of the gain from crossing in swine. The observed variation between estimates of heterosis for a given trait is analyzed: the effects of sampling variance, specific combining ability of some crosses, heterosis by environment interactions and association between heterosis and parental mean are considered and some illustrations are given. Finally the different criteria used in optimization of crossing between available pig breeds are reviewed. The present trend is to pay attention not only to the final cross but to the whole crossbreeding system, either as static (at demographic equilibrium) or dynamic (transition phase from another system). The first results of such a study with two French breeds are given briefly.

Impact of an Old Technology on Profitable Dairying in the 21st Century

Article

Jan 2007

Bradley Heins

There have been many research studies documenting the role of crossbreeding in the dairy industry, but many are quite old and dated. Old research indicated heterosis is greatest for traits related to mortality, fertility, health, and survival. The first scientific trials using crossbred dairy cattle date back as early as 1906 in Denmark and used the Jersey and Danish Red breeds. In the 1930s and 40s, experiments with dairy cattle were conducted to determine heterosis for milk and fat production resulting from crossbreeding (Touchberry, 1992). Crossbreeding has not been studied in research herds in the U.S. for many years. Earlier studies with experimental herds indicated that crossbreds were at least as profitable as pure Holsteins at the University of Illinois (Touchberry, 1992) and Agriculture Canada (McAllister et al., 1994). A crossbreeding project involving the Holstein and Guernsey breeds was conducted at the Illinois Agricultural Experiment Station from 1949 to 1969 (Touchberry, 1992). Heterosis for first-lactation milk and fat production was 4.3% and 4.1%, respectively; however, heterosis was considerably higher (12.0% for milk, 12.8% for fat) in second lactation. Heterosis for days open was 9.4%. When evaluating total performance of purebreds and crossbreds, Touchberry (1992) combined measures of survival, growth, production, and reproduction into an index to calculate the total income produced per cow per lactation and reported heterosis of 14.9% for total income produced per lactation. A Canadian study was conducted in five research herds during the 1970s and 1980s and heterosis of 16.5% was observed for lifetime milk production and 20% and 17.2% for lifetime fat and protein production, respectively. In the same crossbreeding study at Agriculture Canada, McAllister et al., (1994) reported greater than 20% heterosis for lifetime performance in crossbreds of Holstein and Ayrshire. This paper will report current results from studies of crossbreeding Holsteins with US Jersey and Brown Swiss sires, as well as sires from European dairy breeds. A recent crossbreeding study from New Zealand will also be discussed.

Duplicate genes for capsule form in Bursa bursa Bastoris

Article

Jan 1914

George Harrison Shull

Suitability for field service in 4 breeds of guide dogs

Article

Sep 2006
J VET BEHAV

This study examines the relative importance of a longer than normal 4-month training period, or being ¿passed back¿ from the original training class to join a class in which dogs are at an earlier stage of their training, on the overall probability that a dog entering guide dog training will ultimately graduate as a guide dog. The study group consisted of dogs that were trained at The Seeing Eye guide dog school in the years 2000 through 2005. In total, 2033 Labrador retrievers (LR), golden retrievers (GR), German shepherds (GS) and Labrador retriever/golden retriever crosses (LGX) were included in the study. Of all dogs, 39% had been passed back during their training, and 56% had graduated as guide dogs. In general, females had a lower chance to be passed back than males, except for GS and LGX. Overall, GS had the highest chance to be passed back during their training. LGX had the highest, and GS the lowest, probability for graduating as guide dogs. Dogs that were passed back for behavioral reasons were only half as likely as dogs completing training normally to work as guide dogs, whereas medical reasons and ¿no match¿ reasons for being passed back hardly influenced the chances to become guide dogs. Overall, the current 4-month standard training program at The Seeing Eye seemed mostly successful for LGX and LR, whereas GS and GR had a higher success rate when being passed back, i.e., they were more likely to graduate as guide dogs when they were trained for a longer period than the standard training program.

Invited Review: Crossbreeding in Dairy Cattle: A Danish Perspective

Article

Dec 2008
J DAIRY SCI

The value of crossbreeding in livestock species has been known for a long time; it has been used heavily within beef cattle, pig, and poultry production systems for several decades. This has not been the case for dairy production but lately there has been increased interest in crossbreeding dairy breeds. This review focuses on the practical and theoretical background of crossbreeding and describes the gain to be expected using systematic crossbreeding in dairy production. In Denmark, 24% of dairy farmers would consider starting crossbreeding programs within their herd. Evidence for the value of crossbreeding is documented with special emphasis on results from a Danish crossbreeding experiment. This experiment included 1,680 cows from 3 breeds and their crosses. In general, at least 10% heterosis can be expected for total merit, mainly due to increased longevity and improvement of functional traits. A minor part of heterosis for total merit is due to heterosis for production traits. For production, there is evidence of recombination loss using continued crossbreeding programs, which does not seem to be the case for longevity and total merit. However, recombination loss should be investigated more carefully as crossbreeding is becoming more popular. A prerequisite for crossbreeding to be beneficial on a long-term basis is that genetic gain within the parental breeds not be reduced. As long as the crossbred cow population constitutes less than 50% of the whole population, and young bulls can be tested through crossbred offspring, this prerequisite can be fulfilled. Crossbreeding can increase dairy income substantially, especially in management systems requiring a high level of functional traits.

Breed effects and heterosis in advanced generations of composite populations for birth weight, birth date, dystocia, and survival as traits of dam in beef cattle

Article

Oct 1991

Heterosis effects were evaluated as traits of the dam in F2 progeny of F1 dams and F3 and 4 progeny of F2 and 3 dams in three composite populations of beef cattle. Traits included birth weight, birth date, calving difficulty percentage, and survival percentage at birth, 72 h, and weaning for calves with dams of different age classes. Breed effects were evaluated for the nine parental breeds (Red Poll [R], Hereford [H], Angus [A], Limousin [L], Braunvieh [B], Pinzgauer [P], Gelbvieh [G], Simmental [S], and Charolais [C]) that contributed to the three composite populations (MARC I = 1/4 C, 1/4 B, 1/4 L, 1/4 H, 1/8 A; MARC II = 1/4 G, 1/4 S, 1/4 H, 1/4 A; and MARC III = 1/4 R, 1/4 P, 1/4 H, 1/4 A). Among calves with 2-yr-old dams, breed effects were significant for birth weight, birth date, calving difficulty percentage, and survival percentage at birth but not at 72 h and weaning. Calf survival at weaning was lowest for smallest (less than mu - 1.5 sigma) and largest (greater than mu + 1.5 sigma) birth weight classes and did not differ among intermediate birth weight classes. Calves with difficult births with 2-yr-old dams were significantly heavier at birth (39.6 vs 35.4 kg) and had significantly lower survival at 72 h (87.1 vs 92.2%) and at weaning (77.4 vs 85.1%) than calves with 2-yr-old dams that did not experience difficult births. Among calves with dams greater than or equal to 3 yr old and from dams of all ages, breed group effects generally were significant for the traits analyzed. Important breed group effects on dystocia and survival traits were observed independent of breed group effects on birth weight. Effects of heterosis were significant for birth weight for each generation of each composite population and for the mean of the three composite populations. Generally, heterosis effects for calving difficulty percentage were not significant. Effects of heterosis generally were significant for date of birth (earlier) for each composite population and for the mean of the three composite populations. Heterosis effects on survival to weaning percentage generally were positive but generally were not significant. Heterosis retained for birth weight, birth date, and survival percentage in combined F3 and 4 generation progeny of combined F2 and 3 generation dams did not differ (P greater than .05) from expectation based on retained heterozygosity. These results support the hypothesis that heterosis in cattle for these traits is the result of dominance effects of genes.

Additive and Nonadditive Genetic Effects on Milk Production in Dairy Cattle: Evidence for Major Individual Heterosis

Article

Mar 1991

Coefficients for individual and maternal breed composition and the expected contributions of individual and maternal heterosis and breed source of cytoplasm were assigned to 42,554 primiparous Holstein-Friesian, Jersey, and crossbred cows. The individual additive genetic breed effect influenced all milk production traits. Highly significant maternal additive genetic breed effects equivalent to 3% of the mean were identified for milk yield and milk fat percentage. Individual heterosis was highly significant for milk yield and milk fat yield. A primiparous first cross cow produced 6.1% more milk and 7.2% more milk fat than the average of straightbred cows of both breeds. For milk fat yield, the individual heterosis effect was higher than the individual additive genetic breed difference between Jersey and Holstein-Friesian. A small negative maternal heterosis and a small effect of breed source of cytoplasm were estimated for milk fat percentage. Results suggest that individual heterosis is a major genetic effect for milk yield and milk fat yield. This heterosis could be utilized through a stratified breeding scheme in which high genetic merit nucleus herds maintain genetic progress in the two straightbred populations, and commercial dairy herds employ a rotational cross-breeding scheme to take advantage of both the additive genetic progress and nonadditive genetic effects.

Importance of Heterosis in Animals: A Review

Abstract

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