Phenotypic plasticity of Cuban Zebu sires evaluated in different Cuban regions

Plasticidad fenotípica de sementales Cebú Cubano evaluados en diferentes regiones de Cuba

Yusleiby Rodríguez,^I Raquel Ponce de León,^I A. Álvarez,^I M. Rodríguez,^II

ABSTRACT

The phenotypic plasticity of Cuban Zebu sires from their progenies performance test in different regions of the country was analyzed. A number of 15293 weight records at 18 months of animals born in five Cuban enterprises in 1981-2012 were considered. A single-trait animal model allowed evaluating all animals together and consequently, to each individual enterprise. In both cases, the random effects of the individual and error, fixed of the contemporary group and age at the start of the test as quadratic covariate are included. In all enterprises the heritabilities and Spearman correlations between the breeding values of sires with offspring were obtained. The hertabilities were of 0.239 ± 0.047, 0.244 ± 0.056, 0.284 ± 0.040, 0.261 ± 0.044 and 0.153 ± 0.065, for “Camilo Cienfuegos”, “San Juan”, “Rodas” and “Rescate de Sanguily” and genetic and rearing “Manuel Fajardo”, respectively. Breeding values varied between -29.31 and 36.51 kg. "Rodas" and "Rescate de Sanguily" cattle enterprises were of higher range, while the Genetic and Rearing Enterprise "Manuel Fajardo" showed low fluctuations, but higher mean (6.94). Positive and low correlations between breeding values (0.28 - 0.58) indicated the phenotypic plasticity existence, that is manifested in changes in the ranking. It is concluded that it could assess the use, not only of robust animals (which behave appropriately in all regions of the country), but animals with phenotypic plasticity and higher breeding values for a specific region. It achieves increase in live weight.

Key words: Cuban Zebu, genotype - environment interaction, region.

RESUMEN

Se analizó la plasticidad fenotípica de sementales Cebú Cubano a partir de la prueba de comportamiento de sus hijos en diferentes regiones del país. Se consideraron 15293 registros de peso a los 18 meses de animales nacidos en cinco empresas cubanas en el período 1981-2012. Un modelo animal univariado permitió evaluar todos los animales de manera conjunta y posteriormente, a cada empresa individual. En ambos casos, se incluyeron los efectos aleatorios del individuo y del error, fijo del grupo de contemporáneos y edad al inicio de la prueba como covariable cuadrática. En todas las empresas se obtuvieron las heredabilidades y las correlaciones de Spearman entre los valores genéticos de sementales con descendencia. Las heredabilidades fueron de 0.239 ± 0.047, 0.244 ± 0.056, 0.284 ± 0.040, 0.261 ± 0.044 y 0.153 ± 0.065, para las empresas pecuarias “Camilo Cienfuegos”, “San Juan”, “Rodas”, “Rescate de Sanguily” y la de Genética y de Cría “Manuel Fajardo”, respectivamente. Los valores genéticos variaron entre -29.31 y 36.51 kg. Las empresas pecuarias “Rodas” y “Rescate de Sanguily” fueron las de mayor amplitud, mientras que la Empresa Genética y de Cría “Manuel Fajardo” presentó menores fluctuaciones, pero mayor media (6.94). Las positivas y bajas correlaciones entre los valores genéticos (0.28-0.58) indicaron la existencia de plasticidad fenotípica, que se manifiesta en cambios en el orden de mérito de los sementales. Se concluye que se pudiera valorar la utilización, no solo de animales robustos (que se comportan adecuadamente en todas las regiones del país), sino de animales con plasticidad fenotípica y con mayores valores genéticos para una región específica. Se logra así incremento en el peso vivo.

Palabras clave: Cebú cubano, interacción genotipo-ambiente, región.

INTRODUCTION

During last decades, the improvement program of Cuban Zebu cattle has favored the selection of future sires for a supposedly homogeneous environment, due to the standardized characteristics of the grazing performance test on grazing, by which animals are evaluated during 12 months. The sires breeding values are estimated by a single trait animal model that analyzes all the animals, and then the bulls with higher weights or daily gains are selected at the end of the test. The use of BLUP methodology, animal model for genetic evaluations, had fundamentally improvement these animals precision (Guerra et al. 2002), but in current evaluations do not take into account the possible existence of genotype-environment interaction.

Several researches developed in America reported varied results that suggest a certain possibility of genetic variability in the characteristics related to body weight. In B. indicus breeds, Lobo et al. (1994), Mercadante et al. (1995) and Plasse et al. (2002) reported heritability (h²) estimates for weight at 18 months, which varied between 0.13 and 0.31. In Cuba, Guerra et al. (2002), by means of an animal model estimated heritability of 0.20 for the same characteristic in the Cuban Zebu.

The heritability estimates are important to promote by selection an improvement program. However, the productive performance not always reaches the expected levels, due to the influence of several environmental factors that determine its expression. The climatic, nutritional and management changes favor the appearance of phenotypic plasticity.

In Cuba there has been developed this type of studies in dairy cattle, mainly in Holstein (Menéndez 2007), Siboney de Cuba (Suárez et al. 2009) and Mambí de Cuba (Hernández et al. 2012).In Cuban Zebu breed, Rodríguez and Guerra (2013) and Rodríguez et al. (2014) analyzed the response of the male offspring from sires in different management environments, defined by the mean value of the weight gain of the contemporary group.

 Considering that the plan of current use of Cuban Zebu sires do not consider the possible existence of genotype-environment interaction, the objective of this study was to determine whether phenotypic plasticity is manifested in Cuban Zebu sires, depending on the region of the country in that the performance test is carried out.

MATERIALS AND METHODS

The information (15293 observations) corresponds to the data of the final weight of performance test of the Cuban Zebu future sires, fitted at 18 months of age. For entry to the test, the individuals weaned at six months of age must fulfill the requirements to being offspring of sires dams and should have a weaning weight higher than the month mean; they should also fulfill with the phenotypic characteristics of genetic pattern. It was also kept in mind their progenitors breeding value, for the weight at 18 months. The alimentary base during this period was constituted by Cynodon nlemfuensis and Panicum maximum, as well as minerals salts. A total of 1.5 kg/animal/d of the available concentrate were supplemented. During the dry season, it was complemented with king grass or sugar cane, at a rate of 20 kg/d/LAU. In these areas a stocking rate no higher of 1.5 LAU/ha and a minimum of 12 paddocks was considered. 

 From an initial total of 16085 records captured by the Livestock Control System in the six enterprises where the tests were performed, 15293 were considered, corresponding to males born between 1981 and 2012. A 4% of the observations corresponding to an enterprise with few amounts of data, when not possessing adequate progenitors representation, even period of time set in the analysis (only from the 2000 year onwards).

 Out of the five studied enterprises, two corresponded to the west of Cuba, two at the center of the country and one to the east (figure 1). The western region was represented by the Genetic Enterprise "Camilo Cienfuegos", located in Corralito farm, in Consolacion del Sur municipality, belonging to Pinar del Rio province (the most western in Cuba).It was also joined to the study the Enterprise "San Juan", in Martí municipality, located to the northeast of Matanzas province.

In the central region there were taken into account the data of the Enterprises “Rodas”, in the municipality of the same name (northwestern of Cienfuegos province),and “Rescate de Sanguily” in Vertientes, Camagüey province. The eastern representation corresponded to Genetic and Rearing Enterprise “Manuel Fajardo”, located in Jiguani municipality, belonging to the north part of Sierra Maestra, Granma province.

Contemporaries groups were defined from the enterprise information, year and four- month period of birth for the general model and year- four- month period of birth for the analysis of the enterprises individually. Those groups with less than five observations were eliminated, as well as progenitors that were not represented, at least in three enterprises. Subsequently, the information was divided into five data sets corresponding to each of the enterprises. The summary with the number of observations, weight mean values  at 18 months and total of female contemporaries groups in each data set is shown in table 1. The pedigree file considered 799 progenitors and 12125 dams in total.

To obtain the variances, heritabilities, and breeding values, Wombat (Meyer 2006) program was used. An animal single trait model was analyzed by means of its application, which considered as random the individual and the error effects; as fixed the contemporaries group (enterprise-year of birth – four-month period of birth or year of birth- four- month period of birth, depending on the dataset) and age at the start of the test, as quadratic covariable. 

The model, as matrix rotation, is represented in the following way:

y = Xβ+ Zα + e

Where:

y = vector of the observations corresponding to final weights.

β = vector of the fixed effects, that include the sires contemporaries group and the quadratic regression of the age at the end of the test.

α = vector of  random genetic additive effects.

X y Z = incidence matrices relating the observations with fixed and random effects respectively, taken with normal distribution, mean equal zero and variance equal Iσa².

I = identity marix.

e = vector of random residual effects. This one is taken with normal distribution, zero mean and variance Iσe².

The criteria of fit goodness considered for models were the maximum likelihood logarithm (Llog), Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC).

Later on, in the five enterprises the breeding values of the 57 sires with offspring were selected. By INFOSTAT (Di Rienzo et al. 2012) Spearman correlations between the general breeding value (equivalent to that used in the national evaluation) and specific for each enterprise as well as between each pair of enterprises were
calculated.

RESULTS AND DISCUSSION

Heritabilities for final live weight (table 2) resulted moderate. Menéndez et al. (2006) obtained similar values to those of this study by means of character state model models and of random regressions (0.23) for this same trait in the Cuban Zebu. These results were also higher in four of the enterprises, regarding the value informed by Espinoza et al. (2008) in this same breed, for this same trait and through a single-trait model (0.19).Equally, these values were similar to that obtained by Guillén et al. (2011) (0.16 ± 0.03 and 0.26 ± 0.05) for a uni- trait and bi- trait model in this breed respectively.

The higher heritabilities obtained in “Rodas” and “Rescate de Sanguily” enterprises (central region) are justified because they were the ones that showed higher additive genetic variances.

“Rodas” has appropriate conditions for livestock, when   having organic clay soils with ferrallitic elements. These ones have low erosion potential and are not salinized, making them very productive. Precipitations are abundant, with annual mean between 1400 and 1600 mm. This confirms that informed by Pégolo (2009), who refers that environmental conditions and of favorable management make possible better expression of the additive genetic variability, so that the heritability estimates will be higher than in unfavorable environments.

On the other hand, the lowest heritability value was obtained for the eastern region, which coincides with the lower number of observations and higher standard errors. Also, Jiguaní, where Genetic and Rearing Enterprise “Manuel Fajardo” is located, during the dry season, recorded precipitations between 200 and 300 mm, which is insufficient for grasses in  this period. This area, of very low precipitations, is known for being one of the driest plains of Cuba, because of deforestation (Instituto de Meteorología 2014).

In figure 2 is showed the distribution of the air mean temperature and of agricutural drought in Cuba.In both cases, the eastern region is the most unfavorable in terms of these indicators. It has been shown that the combined effect of air temperature, solar radiation, wind and humidity, as well as thermal amplitude have important effect on cattle. The stress caused by hot is determined by their intensity as their duration, which directly acts on the animal thermoregulatory mechanisms.

The statistics of the breeding values of 57 sires common to the five enterprises are showed in table 3. As the table shows, “Camilo Cienfuegos” and “Rodas” enterprises were those that showed the most favorable ranges for the selection. The first of them showed the higher breeding values mean.

Spearman correlation between the breeding values estimated by the general model and each enterprise was lower to the unit (table 4). Robertson (1959) presented the theoretical bases that suggest that the genotype- environment interaction only have important for the biology and agriculture, if the genetic correlation between the same characteristic in different environments is lower to 0.8. The possible explanation is that the same trait can partially controlled by a group of genes in each environment and therefore, the genetic merit is specific for each environmental subclass (Falconer and Mackay 1996).

To illustrate the changes the ranking of sires (figures 3 and 4) ten Cuban Zebu sires with higher and lower breeding values in “Rodas” enterprise were selected and it was contrasted with their performance in the four remaining enterprises. An example of the change in the ranking is show in the 5065B sire, that is first in Matanzas and Cienfuegos classification.However, it is in last  places in the remaining enterprises.The opposite happens with the 5338B sire,with unfavorable performance in all regions, even in Camagüey.From the 57 selected sires, approximatelly a 23 % could be classified as robust,since it is able to maintain a similar performance in all regions of the country, but only four of them have improvements breeding values in all environments.The rest shows phenotypic plasticity.In  genaral,68% of the breeding values estimates for the five enterprises were positive or improvements.

Rodríguez and Guerra (2013) obtained similar results in Cuba, in Cuban Zebu specifically, when considering the mean values of the contemporaries groups as different environments, or management environments.Likewise, De Souza et al. (1997) and  Silva et al. (2008) obtained  results on changes in the ranking in eight different tropical regions of Brazil. Both researchers  evaluated the genotype- enviroment interaction of the live weight in Nellore breed, considering as enviroment the differentt geographical regions of Brazil.

In the Cuban Zebu improvement program, the applied selection intensity is only one in the whole country, and only one heritability value for the whole population is used. From the breeding values, the sires classification is carried out, without considering the country region where the semen will be used. It could be justified the existence of a differential response in the breeding values of sires between the enterprises where the performance test is carried out because these are located in very distant regions among each other, that show differences in altitude, air mean temperature, amount of precipitations and soil type. They also differ in regard to the management of each enterprise.     

It is conclude that is possible to carry out a selection process per final weihgt in the Cuban Zebu current population, from the  recorded heritabilty values in the five enterprises.However, it should be considered the existance of changes in the sires ranking according with the place in which their offspring carry out the performance test.From this results, it could assess the sires current use plan and the use of robust animals(that be able appropiately behave in all Cuba regions).If on the opposite, the nutritional and management resources are locally guaranteed (high environment), it may be more appropiate the use of animals with phenotypic plasticity.In other words,animals that show the highest breeding values for this specific region, which would allow to increase te genetic progress for the live weight in this breed.

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Received: January 6, 2015
Accepted: May 19, 2015

Yusleiby Rodríguez, Instituto de Ciencia Animal, Apartado Postal 24, San José de las Lajas, Mayabeque, Cuba. Email: yusleiby@ica.co.cu