Relationship between Some Myostatin Variants and Meat Pro-duction Related Calving, Weaning and Muscularity Traits in Charolais Cattle

1. Introduction

The value of the slaughter animals, that is the carcass composition, and meat quality of meat-producing farm animals, such as slaughter cattle, can be reliably evaluated with post-slaughter muscle and fat measurements and laboratory tests. In reality, however, slaughterhouse evaluation and laboratory meat quality testing are often impossible in the trade, as the animals are marketed on live basis. Despite of failing the mentioned objective evaluation possibilities both the sellers and the buyers must be able to visually or other ways appraise the meat production, the value of these animals.

Meat production, value of slaughter animals can be evaluated with a high degree of accuracy based on a number of external or internal characteristics seen, measured and estimated on them. A large number of literary sources, research results support the fact that the age, weight, sex, conformation, condition, muscle mass and shape of live animals provide reliable information about their meat production, however some environmental factors can also play an important role [1]. The mentioned traits can be easily assessed by visual scoring. At the same time some major genes or quantitative trait loci (QTL) were identified related to meet quantity and quality [2,3]. The latter situation gives us the opportunity to perform tests on live animals, as DNA can be isolated from blood or other tissue and the gene or gene variants affecting meat production can be detected. Such kind of tests can be carried out early, before slaughter at a young age of animals.

An indicator of slaughter value could be the myostatin which is an extracellular cytokine mostly expressed in skeletal muscles and known to play a crucial role in the negative regulation of muscle mass [4,5].

Sellick et al. [6] studying the different variants of myostatin genes found that F94L was the only polymorphism consistently related to increased muscling. Wiener et al. [7] found that the myostatin allele with the 11-bp deletion (MH) segregating in the South Devon breed affects several traits related to beef production. The MH allele was associated with heavier calves at birth but slower growth, leading to lighter adult animals. Allais et al. [8] found superiority of carcass traits of calves carrying one copy of the mutated allele (Q204X or nt821) over noncarrier animals was approximately +1 SD in the Charolais and Limousin breeds but was not significant in the Blonde d’Aquitaine. In the Charolais breed, for which the frequency was the greatest (7%), young bulls carrying the Q204X mutation presented a carcass with less fat, less intramuscular fat and collagen contents, and a clearer and more tender meat than those of homozygous-normal cattle. Hales et al. [9] reported that average daily gain measured in Limousin heifers across the whole study (121 day) was greater with 2 copies of the F94L (homozygous) variant. According to Ceccobelli et al. [10] the heterozygous myostatin gene in Marchigiana bulls showed slight superiority in the carcass weight (heterozygote 426 kg and normal 405 kg) and meat quality parameters, although not always with statistical significance.

Looking at the relevant literature, despite the fact that there is a lot of information, research results available on the effect of myostatin on meat production in cattle especially in double-muscled cattle [11,12], relatively less is known about the effect of certain alleles in Charolais. Based on previous data [13,14,15], it seems that there are significant differences between the phenotypic performance of individuals carrying and not carrying the myostatin alleles [16].

The objective of the present study was to evaluate some myostatin alleles such as F94L and Q204X and others on birth weight, calving ease, 205-day weaning weight and muscle score of some body part (shoulder, back, thigh, loin) and overall muscularity showing muscle development and trend of these traits in Charolais beef cattle population in Hungary.

2. Materials and Methods

2.1. The database

Data processed during the work were collected from the pedigree database of the National Association of Hungarian Charolais Cattle Breeders. The available and evaluated initial database contained pedigree, weaning, conformation traits and molecular genetic information. In the study there were of 2046 EU registered weaned Charolais calves (688 male 1358 female) born between 2015-2021.

2.2. The studied traits

During the study birth weight of calves (BIW), calving ease of dams (CAE), 205-day weaning weight of calves (CWW) moreover muscle score of shoulder (MSS), muscle score of back (MSB), muscle score of thigh (MST), roundness score of thigh (RST), loin thickness score (LTS) and overall muscle development percentage (OMP) as a phenotypic traits of weaned calves were evaluated in relation with myostatin mutations.

The conformation traits were scored at the weaning. The scoring of the mentioned body parts was carried out according to Conformation Scoring Guideline of National Association of Hungarian Charolais Cattle Breeders [17]. Each animal for each trait was scored from 1 to 10 points depending on the mass and shape of the muscles. However, the values of the OMP were calculated by the sum of the scores of each body part and the ratio of the maximum possible total score in per cent as follows:

OMP = (MSS + MSB + MST + RST + 2 x LTS) / 60

(1)

The calving ease of cows was scored as follows: normal light calving 1, calving with assistance 2 and difficult calving 3.

2.3. The molecular genetic informations

The molecular genetic information of the 2046 weaned calves was determined with the Weatherbys Scientific Bovine VersaSNP 50K chip. The description of the method and the possibilities of interpreting the results were described in detail by [18].

The genetic database contained information on 117 different alleles. In the course of this study five relevant alleles of the gene encoding the myostatin protein (growth differentiation factor 8; GDF8), F94L, Q204X, nt267, nt324 and nt414 were examined [19,20]. Based on the available information [21,22,23], it seems that these alleles can have a significant impact on muscle growth, including the development of muscularity. In each case, it was indicated in the database whether the individuals carry the F94L, Q204X, nt267, nt324 and nt414 alleles in homozygous or heterozygous form, or not. The distribution of these alleles by sex of calves is shown in Table 1.

2.4. The effect of different factors

Before evaluating the database the basic statistical parameters of the examined traits (mean, standard deviation, CV%, etc.) were calculated. To check the normality of the data Kolgomorov-Smirnov test, to check the homogeneity of the variances Levene test were used (Table 2).

To evaluate the database multifactor analysis of variance (General Linear Model) was applied [24]. During this work, the birth year and sex of the calves, as well as the genotype determined on the basis of the myostatin alleles (mentioned above) were incorporated into the model as fixed effects [16]. The nine examined traits were treated separately from each other, and in all 9 cases separated models were performed. The general formula of the models used was as follows:

ŷ_hijklmn = μ + Y_h + S_i + F_j + Q_k + N_l + M_m + T_n + e_hijklmn

(2)

where ŷ_hijklmn = trait of a weaned calf of "h" year, "i" sex, "j" F94L, "k" Q204X, “l” nt267, “m” nt324 and “n” nt414 genotypes; μ = average of all observations; Y_h = effect of birth year of calves; S_i = effect of sex of calves; F_j = effect of F94L allele; Q_k = effect of Q204X allele; N_l = effect of nt324 allele; M_m = effect of nt324 allele; T_n = effect of nt414 allele; e_hijklmn = random error [10].

2.5. Estimation of phenotypic trends and phenotypic correlations

For all nine traits of the evaluated calves born in the same year were analyzed and averaged. Weighted one-way linear regression analysis was used to estimate of the phenotypic trends. The dependent variable was the evaluated trait, the birth year of calves was considered as an independent variable, and the weight was the number of individuals per year.

Among the nine evaluated traits, Pearson's phenotypic correlation values (r) were also determined.

2.6. The used softwares

The data were prepared using Microsoft Excel 2003 and Word 2003. The evaluation of the database was performed with the statistical software package SPSS 27.0 [25].

3. Results

For all traits, the influence of the sex of the calf was statistically verifiable (p<0.01) and played a decisive role (62.27-96.74%) in the development of the phenotype (Table 3). The effect of the year of birth of the calves on the tested traits was also significant (p<0.01). Among the myostatin alleles, the effect of Q204X was statistically proved (p<0.01 and p<0.05) on the traits CWW, MSB, MST, LTS and OMP. The other alleles had no effect on the evaluated weaning and muscularity traits.

The adjusted overall mean values (±SE) of the examined traits was as follows (Table 4 and Table 5): BIW 43.65±0.63 kg, CAE 1.12±0.05 points, CWW 269.07±4.73 kg, MSS 5.90±0,11 points, MSB 5.39±0.11 points, MST 5.65±0.12 points, RST 5.54±0.12 points, LTS 5.52±0.11 points and OMP 55.86±0.96%.

Regarding CWW, the calves carrying the Q204X allele in heterozygous form in the studied population gained 8.56 kg more weight than their counterparts not carrying the allele. From the point of view of the F94L allele, there was a difference of 4.08 kg in favor of the heterozygous individuals, but this difference could not be verified statistically. The weight of the individuals carrying the nt324 and nt414 alleles in homozygous form was higher (10.43 kg and 2.92 kg, respectively) than the non-carriers, but these differences were not significant either.

In terms of muscularity scores, it could be established that calves carrying the Q204X allele in heterozygous form achieved approximately 0.14 points higher MSB, MST and LTS and 1.2% higher OMP than those their non-carrying partners. Despite the fact that the F94L allele had no statistically verifiable effect on muscularity parameters, it was striking that non-carrier calves showed higher values in almost all muscularity scores than heterozygous carriers. In the case of the nt267, nt324 and nt414 alleles, the muscularity score of the heterozygous, but even more so the homozygous carrier calves was - although not significantly - higher than that of the non-carrier individuals.

In the case of all traits, we observed considerable differences between the individual born in different years. This was also supported by the results of the phenotypic trend calculation (Table 6), according to which 6 of the 9 examined traits were statistically reliable (p<0.05 and p<0.01) and fairly well matched (R² = 0.57- 0.93) regression functions were obtained. In the case of BIW and CWW, the slope of the straight lines (b) was in a positive direction, while in the case of the other traits it was in a negative direction. Here must be note that in the case of muscularity parameters, the annual decrease is very small, typically -0.05, or -0.07 points/year.

Based on the obtained phenotypic correlation values (Table 7), it could be established that the calving and weaning traits did not show a close relationship with each other or with the muscularity traits (r = 0.00-0.24). On the other hand, there was a close (r = 0.61-0.92) and statistically reliable (p<0.01) correlation between the muscularity scores.

4. Discussion

Similar to the results of our work, several previous sources [8,21,26] contain information on the statistically verifiable effect of the Q204X allele on the meat production related traits. Contrary to our results, several previous studies [6,16] found the effect of the F94L allele to be significant on some muscularity-related parameters. Among the alleles belonging to the "small" myostatin group, we only found information on the effect of the double-muscled related allele nt821 in existing sources [27,28,29], however, this allele did not occur in the is the tested Charolais stock. The genetic structure of the nt267, nt324 and nt414 alleles was previously described by Dunner et al. [21], but no literature data were found on their effect on the phenotypic results.

The results of our work are similar to the findings of Casas et al. [12], according to which myostatin alleles in heterozygous form can have a favorable effect on weaning traits. Contrary to the results of Allais et al. [8], we could not detect the effect of the Q204X allele on birth weight in the examined Charolais herd. Similar to the results of Esmailizadeh et al. [22], the effect of the F94L allele on birth and weaning traits was not found to be significant.

Our results for the weaning weight of Charolais calves were similar to the data found in most of the relevant literary sources [30,31,32]. On the basis of the calving ease score observed during our work, it seems that there were fewer difficult calvings in the studied herd than what was found in the literature [33,34] in the case of the Charolais breed.

We found very little information available in the literature about the conformation of Charolais calves related to their muscularity. Arango et al. [35] and Vallée et al. [36] published data on purebred and crossbred Charolais herds, but due to the different methodology, we did not have the opportunity to compare them with our results.

The differences by birth year and sex of calves in weaning weight obtained during our work are very well known in the literature [37,38]. However, we did not find any data for this kind of evaluation of the muscularity parameters of Charolais calves.

Similar to our results, Gutiérrez et al. [39] and Chud et al. [40] did not find a close correlation between BIW, CAE and CWW traits in the case of the Asturiana de los Valles breed of cattle, and in the case of the Nellore breed.

5. Conclusions

Of the five myostatin alleles examined during this research, Q204X clearly proved to have the greatest effect on calving, weaning and muscularity-related traits. The allele was only present in heterozygous form in the evaluated Charolais population, so according to the available literature information, it did not affect CAE and BIW, but it clearly had a favorable effect on CWW. The effect of the allele on muscularity-related traits was also positive, although to a much lesser extent. Therefore, we think it would be advisable to pay attention to this allele in the breeding strategy, to increase the proportion of carriers from generation to generation. It would be advisable to repeat this test periodically, because based on literature data, it seems that the allele in its homozygous form could cause calving difficulty.

Based on our results, the favorable effect of the F94L allele shown in previous research was not detectable in our study. One of the reasons for this may be that the proportion of animals carrying the allele (about 5.5%) was very small in the studied population. On the other hand, based on previous studies, the better phenotypic performance of individuals carrying the allele was more evident in the fattening and slaughter traits.

The proportion of calves carrying the nt324 and nt414 alleles was quite high (21.5% and 48.1%, respectively) in the examined Charolais population. In the literature, there was very little information about their effect on phenotypic performance. Based on our results, it seems that homozygous carrier individuals may have better growth performance-related traits than non-carrier individuals.