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Population genetic variations of haemoglobin in yak, cattle and their hybrids

T. Shixin and H. Jianlin

Laboratory of Animal Genetics, Department of Animal Science, Gansu Agricultural University, Lanzhou 730070, Gansu, P.R. China

Summary

Polyacrylamide gel electrophoresis was used to analyse haemoglobin (Hb) polymorphism in six yak populations (Jianza County of Qinghai Province, Sunan County, Tianzhu County, Maqu County, Luqu County and Xiahe County of Gansu Province), two cattle populations (Wuwei City and Linxia County of Gansu Province) and one F1 hybrid population (Linxia County). The results show that the Hb locus in yak consists of only one genotype (HbAA). At the opposite the Yellow cattle studied show three alleles (HbA, HbB and HbC), with three genotypes detected in the population from Linxia County (HbAA, HbBB, HbBC) and five genotypes detected in the population from Wuwei City (HbAA, HbAB, HbBB, HbBC and HbAC). The F1 hybrid population has three alleles (HbA, HbB and HbC) with three genotypes (HbAA, HbAB and HbAC). In cattle and in cattle × yak hybrid the commonest allele is HbA.

Keywords: Cattle, haemoglobin, hybrid, polymorphism, yak

Introduction

As a unique domestic animal living in the high altitude zones, the yak (Bos grunniens) remain productive in the extreme environmental condition of the Qinghai-Tibetan Plateau where hardly any other livestock can survive. China is a main country on yak husbandry and it has more than 95% of the total yak population in the world.

Haemoglobin (Hb) is the major carrier of oxygen in the blood. Genetic variation at the protein might reflect adaptation to local environmental conditions. Ranchev (1981) and Nyamsamba and Zagdsuren (1994) identified three genotypes (HbAA, HbAB and HbBB) and two alleles (HbA and HbB) in Mongolian yak. However, no polymorphisms were identified in Tianzhu White yak, Nepalese yak, Jiulong yak, Tibetan yak and Maiwa yak (Men et al. 1989; Qi et al. 1991; Namikawa et al. 1992; Cheng et al. 1995; Zhong et al. 1999).

The purpose of this study is to extend these previous findings into a larger geographic area with the analysis of new yak populations. Also, we will compare genetic variation in yak's haemoglobin with the ones present in Yellow cattle and hybrids Yellow cattle yak.

Materials and methods

Samples of six yak populations were collected from Sunan County (n = 38), Tianzhu County (n = 63), Maqu County (n = 69), Xiahe County (n = 20), Luqu County of Gansu Province (n = 36), and Jianza County of Qinghai Province (n = 43). Two cattle populations, from Wuwei city (n = 46) and Linxia County of Gansu (n = 22), and one F1 hybrid population from Linxia (n = 45) were also analysed.

Gel electrophoresis conditions were in accordance to the findings of Han et al. (1996). After electrophoresis the gel was dyed using Commassie Brilliant Blue (G250) for about thirty minutes and then washed in 7% acetic acid solution. We used the standard nomenclature from Namikawa et al. (1992) for the calling of the Hb genotypes (Figure 1).

Source: Namikawa et al. (1992). 

Figure 1. Possible haemoglobin genotypes.

Results and discussion

In this study, we could not identify polymorphism at the Hb locus in 269 yak samples from six populations. Only the HbAA genotype was found in yak. At the opposite the two Yellow cattle populations were polymorphic at the Hb loci. We identified three alleles and four genotypes in the Linxia population, meanwhile the same alleles and five genotypes were present in the Wuwei population. The Hb loci of F1 hybrid population were also polymorphic with three alleles and three genotypes (Table 1). The allele and genotype frequencies in F1 (Yellow cattle × yak) is similar to the ones found by Namikawa et al. (1992) in the Nepalese hybrids of yak × cattle.

The absence of polymorphism at the haemoglobin locus in yak populations analysed in this study and previous works which failed to identify any polymorphism in all but one population of yak (Ranchev 1981; Men et al. 1989; Qi et al. 1991; Namikawa et al. 1992; Nyamsamba and Zagdsuren 1994; Cheng et al. 1995; Zhong et al. 1999) strongly support that genetically pure yak populations will be monomorphic at the haemoglobin locus for allele HbA. Also, it suggests that the HbAA genotype might have been selected in yak given its possible stronger affinity for oxygen. Therefore, Hb polymorphism present in Mongolian yak (Ranchev 1981; Nyamsamba and Zagdsuren 1994) show past hybridisation efforts in yak population.

Table 1. Allelic and genotypic frequencies observed at the haemoglobin locus.

Population

No. of animal

Allele frequencies

Genotype frequencies

A

B

C

AA

BB

AB

BC

AC

Wuwei cattle

46

0.794

0.163

0.043

0.717

0.087

0.110

0.043

0.043

Linxia cattle

22

0.909

0.068

0.023

0.910

0.045

0.045

F1 hybrids

45

0.967

0.022

0.011

0.934

0.044

0.022

Yak

269

1.000

1.000

References

Cheng Zhihua, Zhong Jincheng, Hu Ouming, Deng Xiaoyin, Lani and Liecuo. 1995. A study on polymorphism of blood protein in Tibetan yak. Chinese Journal of Southwest Nationalities College 21(4):414417.

Han Jianlin, Luo Yuzhu, Wang Xiaoli and Wang Baosheng. 1996. Study on the polymorphism of haemoglobin of Zhongwei goats. Chinese Journal of Gansu Agricultural University 31:109114.

Men Zhengming, Han Jianlin and Zhang Yuezhou. 1989. Study on the blood protein polymorphism of Tianzhu White yak. Journal of China Yak 4:35.

Namikawa T., Amano T., Yamamoto Y., Tsunoda T., Shotake T., Nishida T. and Rajbhandary H.B. 1992. Genetic differentiation in blood groups and blood protein variants of Nepalese cattle, yak and zoopa. Report of the Society for Researches on Native Livestock (Japan) 14:1737.

Nyamsamba D. and Zagdsuren Yo. 1994. Biochemical polymorphism and red cell blood group serology of yak. In: Rongchang Zh., Jianlin H. and Jianping W. (eds), Proceedings of the 1st international congress on yak held in Lanzhou, P.R. China, 49 September 1994. Supplement of Journal of Gansu Agricultural University, Lanzhou, P.R. China. pp. 8588.

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