ORIGINAL

Non-genetic effects on growth characteristics of Brahman cattle

Efectos no genéticos sobre caracteres de crecimiento del ganado Brahman

Nicacia Hernández-Hernández,¹ M.Sc, Juan Martínez-González,¹* Ph.D, Gaspar Parra-Bracamonte,² Ph.D, Martín Ibarra-Hinojosa,¹ Ph.D, Florencio Briones-Encinia,¹ Ph.D, Pánfilo Saldaña-Campos,³ Ph.D, Eligio Ortega-Rivas,⁴ Ph.D.

¹Universidad Autónoma de Tamaulipas-Facultad de Ingeniería y Ciencias. Centro Universitario Adolfo López Mateos. Apartado Postal 149. Ciudad Victoria, Tamaulipas, México. C.P. 87149. Tel. Fax: +52 834 318 1721.
²Instituto Politécnico Nacional-Centro de Biotecnología Genómica. Boulevard del Maestro SN. Esq. Elías Piña, Col. Narciso Mendoza. Reynosa, Tamaulipas, México. C.P. 88710.
³Instituto Tecnológico de Huejutla. Carretera Huejutla-Challahuiyapa km 5.5, Huejutla de los Reyes, Hidalgo, México. C.P. 43000.
⁴Asociación Mexicana de Criadores de Cebú. Naranjo No. 1006 Col. Águila. Tampico, Tamaulipas, México. C.P. 89230.

*Correspondence: jmartinez@uat.edu.mx

Received: June 2014; Accepted: November 2014.

ABSTRACT

Objective. To determine how some non-genetic factors influence weights at birth (BW), weaning (WW) and yearling (YW) of Brahman calves. Materials and methods. Data corresponding to 58257, 57045 and 40364 for BW, WW and YW, respectively, were analyzed. The models included the effects of year and season of birth and sex, and were considered simple interactions. Results. All effects were significant (p<0.05) for BW, WW and YW. Only the season of birth didn't have a significant effect (p>0.05) on WW. The average general BW, WW and YW were 32±3.2, 188±37.7 and 291±56.8 kg, respectively. Variables evaluated that take into account the year of birth show a trend to increase weight each year. In relation to the birth season on BW and YW, it was observed that calves born during the rainy season were heavier than those born during the dry season. Similarly, male calves were heavier than females at birth, weaning and one year of age. The effects of the analyzed interactions were significant (p<0.05) for the three variables, except for the season of birth per sex interaction, which did not have a significant effect (p>0.05) for BW and WW. Conclusions. The studied non-genetic factors were important and should be taken into account in management strategies when striving to increase the efficiency of the productive system.

Key words: Zebu, birth weight, weaning weight, year weight. (Source: AIMS).

RESUMEN

Objetivo. Determinar cómo influyen algunos factores no genéticos sobre los pesos al nacer (PN), al destete (PD) y al año (PA) de terneros Brahman. Materiales y métodos. Se analizaron 58257; 57045 y 40364 datos para PN, PD y PA, respectivamente. Los registros fueron de animales nacidos durante los años 1994 a 2012. El modelo incluyó los efectos de año y época de nacimiento y sexo, también se consideraron las interacciones simples. Resultados. Todos los efectos resultaron significativos (p<0.05) para PN, PD y PA. Sólo el efecto de época de nacimiento no tuvo efecto significativo (p>0.05) para el PD. Las medias generales de PN, PD y PA fueron de 32±3.2, 188±37.7 y 291±56.8 kg, respectivamente. Para las variables evaluadas sobre el año de nacimiento se observó una tendencia de aumento del peso conforme transcurrieron los años de estudio. Con relación a la época de nacimiento sobre el PN y PA se observó que los terneros nacidos durante la época de lluviosa fueron más pesados, que los nacidos durante la época seca. De igual modo, los terneros machos fueron más pesados que las hembras al nacimiento, destete y al año de edad. Los efectos de las interacciones analizadas fueron significativas (p<0.05) para las tres variables, a excepción, de la interacción época de nacimiento por sexo que no tuvo efecto significativo (p>0.05) para el PN y PD. Conclusiones. Los factores no genéticos estudiados fueron importantes y deben ser tenidos en cuenta en las estrategias de manejo cuando se quiere incrementar la eficiencia del sistema productivo.

Palabras clave: Cebú, peso al nacer, peso al destete, peso al año. (Fuente: AIMS).

INTRODUCTION

Bovine growth is represented by increasing of the animal's weight during different the stages of his life. Therefore, the importance of evaluating growth is based on selecting both males and females and has a great economic importance for production systems (1,2).

An important component to evaluate in order to estimate the profitability of bovine meat production is the growth of calves as well as the reproductive efficiency of the cow (3). From a productive point of view, intermediate weight at birth (WB) is the most beneficial, since high weights are associated with distocic births and very low weights are associated with an increase in the pre-weaning mortality of the calves. Thus, the WB has a positive association with the weaning weight (WW) and later growth measurements (2). On the other hand, WW influences the determination of the economic efficiency of any bovine production system and can be recommended as selection criteria (3).

A way to measure productive behavior is by evaluating growth, reproduction and survival characteristics (3). These characters are influenced by a series of environmental and genetic factors. Among environmental factors, the most common are: year of birth, season or month of birth, sex of the calf, age of the mother (measured in years or number of births), among others. It is known that these factors are different within the relative magnitude, according to agroecological area, production unit and genetic constitution of the population under study; however, it is necessary to assess the degree to which these factors affect certain characteristics in a defined population (4-6).

On the other hand, the zebu livestock has a superior capacity to regulate body temperature during heat caloric stress in comparison with European livestock (7). This superior capacity to regulate body temperature is the result of lower metabolic rates and a greater capacity to lose heat. In the same way, it has been demonstrated that in zebu breeds there exists an important variation that resists tick infestations (8).

The objective of the present study was to evaluate the influence of some environmental factors on the growth of Brahman calves.

MATERIAL AND METHODS

Data base. The study was done with data of weights of calves in the Ponderal Development Control Program authorized by the Mexican Association of Zebu Breeders (AMCC for its initials in Spanish) with headquarters in Tampico, Tamaulipas, Mexico (9). The animals were weighed at least every 90 days from birth until approximately 550 days old (10).

The information analyzed corresponded to 58257 Brahmans born between 1994 and 2012 and registered with AMCC. The ranches where the animals were were spread out through the whole country, mainly in the tropical areas of Mexico. Modifying the feeding and handling systems; but in general registered breeders handle the animals uniformly (10); the handling of these animals has been previously described by several authors (2,11).

Growth variables considered in this study were weight at birth (WB=58257), weight at weaning (WW=57045) and yearling weight (YW=40364). To analyze the data base, incomplete records were eliminated and the WW and YW were adjusted according to the recommendations of the Beef Improvement Federation of the United States (12).

Statistic model and analysis. Data was submitted to a variance analysis using the MIXED procedure from the SAS statistical packet (13) that included the random effect of the bull, and the fixed effect of the birth year (BY) and sex (SX). The birth seasons were defined as: 1=dry (January to June) and 2=rainy (July to December). By preliminary analysis the ranch effect and the age of the mother were discarded from the final analysis.

The model described was:
Y_ijklm=µ+T_i+AN_j+EN_k+SE_l+(AN*EN)_jk+(AN*SE)_jl+(EN*SE)_kl+E_ijklm
Where:
Y_ijklm=Is weight (at birth; at weaning; at one year)
µ=General average of weight (at birth or weaning)
T_i=Random effect of the i-th bull.
AN_j=Fixed effect of the j-th year of birth
EN_k=Fixed effect of the k-th birth season
SE_l=Fixed effect of the l-th sex of the animal
(AN*EN)_jk=Effect of the interaction year of birth x birth season
(AN*SE)_jl= Effect of the interaction year of birth x sex
(EN*SE)_kl= Effect of the interaction birth season x sex
E_ijklm= Experimental error.

To determine different statistical differences, the Tukey measurement comparison test with a significance level of 5% was used.

RESULTS

The average general weight for BW was 32.0±3.2 kg, with a variation coefficient of 8.2%. For this parameter all the variation sources had a significant effect (p<0.05).

The measurement found for weaning weight was 188.0±37.7 kg, with a variation coefficient of 16.4%. On the other hand, all the effects were significant (p<0.05) with the exception of birth season.

Lastly, the general measurement ± DE for the weight at one year was 290.9±56.8 kg. For this parameter, all the variation sources also had a significant effect (p<0.05).

DISCUSSION

Weight at birth. The average birth weight was 32.0±3.2 kg. This result is similar to what was reported in other investigations (4,5,11,14) where it is mentioned that the BW was around 32.0 kg. On the other hand, Cienfuegos-Rivas et al (15) reported an average of 37.7±6.1 kg.

Table 1 shows the measurements of BW for BY. It can be seen that the calves born in 1996 had a lower weight at 31.3±3.1 kg, while calves born in 2005 were the heaviest, reaching an average of 33.1±3.5 kg. Several authors (4,5,11,14) mention that the BY affects the BW significantly. These differences in weight can be attributed to changes in the availability of forage and management of different herds, as well as climatic variations from year to year given the increasingly more erratic precipitation.

In the same way, calves born during the rainy season weighed an average of 200g more than those born during the dry season (Table 2). These results are similar to those obtained by Pereda-Solís et al (16), who showed 31.0 kg in the dry season and 32.0 kg for the rainy season. As to be expected, environmental conditions during the rainy season presented a more favorable panorama for cows, providing greater availability of enviorement the quantity and quality of forage that also translates into a greater weight in calves at birth.

Similar results were observed for the sex of the calf; in this study the males were larger than the females by 1.8 kg (Table 2). These results are similar to those obtained by Stüve et al (4) and Pereda-Solís et al (16). This difference in weight is attributed to androgenic hormones, particularly testosterone.

On the other hand, the effects of BY x BS and BY x SX were significant (p<0.05). With relation to the interaction of BY and BS it was observed that calves born in 2010 in the rainy season were heaviest with 33.6 kg, while those born in 1997 in the rainy season were only 31.8 kg. These results do not agree with those reported by Stüve et al (4).

Similarly, with the interaction of BY and SX it is observed that males born in 2005 were the heaviest with 33.1 kg and the females born in 1995 only reached 30.0 kg. This effect is probably due to the weight differences between sexes over the years (16).

Weight at weaning. The general average ±DE for weight at weaning (WW) corrected at 205 days was 188.0±37.7 kg. These results agree with those reported in literature (6,11,14). However, Plasse et al (17) found a WW of 147.1±1.0. On the other hand, Montes et al (18) reported a WW of 237.08 kg in Brahman cattle.

Table 1 shows averages of WW and BY and it can be appreciated that calves born in 1994 only had an average of 163.5±28.0 kg, while those born during 2011 reached 196.7±38.4 kg, the tendency was to increase the WW as the years of the study passed (2). These results could be due to the fact that the genetic improvement of the Brahman herds is added to the agroecological conditions of production units, which translates into greater weight of the animals (2,16).

For the effect of season of birth no significant differences (p>0.05) were found between the dry and rainy season (Table 2). These results differ from those obtained by Stüve et al (4), who observed differences in weaning weight according to the birth month.

Regarding sex, it was observed that the male calves were larger with an average of 193.3±34.0 kg in comparison to the females whose average was 173.9±92.0 kg with a difference of 19.4 kg (Table 2). These results are similar to those indicated by Rodríguez et al (6) with 203.8 kg for males, with females at 189.6 kg. On the other hand, Plasse et al (17) highlighted lower weight for a Brahman farm (147.0 kg).

In the year of birth and seasons of birth interaction, it was observed that calves born in 2011 and the rainy season were the heaviest at 197.1±39.9 kg, while those born in 1994 in rainy season only reached 160.3±27.8 kg. The results agree with those of Rodríguez et al (6) and Plasse et al (17), who explained that the variation in weights is due to the changes in environmental conditions.

The interaction of year of birth and sex of the animal showed that males born in 2002 in the dry season were heavier at 200.0±35.6 kg, and females born in 2002 in the rainy season only reached 156.6±28.4 kg. Other investigators (6) did find differences in the interaction.

Weight by year. Lastly, the general average ±DE for weight at one year was 290.9±56.8 kg. These results agree with those cited in literature (2, 11), for example in bovines of the Sardo Negro the YW was 281.4±50.1 kg (19). In the same way, Parra-Bracamonte et al (2) obtained a general average of 261.6±57.4 kg. On the other hand, Velásquez and Álvarez (20) obtained lower results at 237.5 kg.

With relation to the YB it can be observed that calves born during 1994 were lighter (213.9±42.7 kg), while calves born in 2012 were heaviest (307.7±32.6 kg). At any rate, in all the evaluated variables a tendency to increase in YW in each successive study year was observed (Table 1).

As for the seasons, calves born during the rainy season were the heaviest (288.3±58.8 kg), compared to those born during the dry season (278.6±60.7 kg)(Table 2). These results agree with those obtained by Pereda-Solís et al (16), who found in the rainy season an average of (232.0±3.9 kg) and in the dry season an average of (225.0±12.8) kg. This could be due to adverse climatic conditions and the lack of availability to the quality and quantity of forage during the latter period.

As in BW and WW, male calves were heavier with an average of 296.8±56.3 kg when compared to females with an average of 243.5±52.3 kg with a difference of 53.3 kg (Table 2). These results are different from those obtained by Pereda-Solís et al (16) for males (232.0±3.9 kg) and females (208.0±3.1 kg).

Similar to BW and WW, in this study the effects of simple interactions were evaluated, observing that these were significant (p<0.05). In the interaction between year of birth and season of birth, it was observed that calves born in 2012 in the dry season were the heaviest with 307.7 kg, while those born in 2004 in the dry season only reached 279.7 kg.

Accordingly, the interaction year of birth and animal sex, it was observed that males born in 2012 were the heaviest at 325.7 kg and females born in 2002 only reached 233.3 kg.

Similarly, the interaction between season of birth and sex of the animal significantly affect (p<0.05) calves born in the rainy season were the heaviest at 305.5 kg, while females born in dry season were only 249.5 kg. These results agree with Pereda-Solís et al (16), who observed that males born in the rainy season reached a greater weight (232.0 kg) compared to females born in the dry season (206.0 kg).

On the other hand, in a study to determine the effects of young Brahman yearling bulls (grey or red) on age, it was observed that the Red Brahman bulls were heavier with significant differences (20).

In conclusion, the factors of year of birth and sex significantly affect BW, WW, and YW and therefore are important to be kept in mind for handling strategies when increasing the efficiency of the productive system.

Acknowledgements

The authors wish to express their appreciation to the Mexican Association of Zebu Breeders for the facilities used during the study and the National Council for Science and Technology for the scholarship given to the first author to carry out master's studies in sciences.

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