GENETIC VARIATION OF DIFFERENT PHENOTYPES OF WEST AFRICAN DWARF GOAT BASED ON HAEMOGLOBIN POLYMORPHISM IN GULU, NIGER STATE, NIGERIA

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1 GENETIC VARIATION OF DIFFERENT PHENOTYPES OF WEST AFRICAN DWARF GOAT BASED ON HAEMOGLOBIN POLYMORPHISM IN GULU, NIGER STATE, NIGERIA ABSTRACT Musa, J., Garba, H., Egena, S. S. A. and Aremu, A. Department of Animal Production, Federal University of Technology, PMB. 65, Minna, Niger State, Nigeria The study evaluated genetic variation of different phenotypes of West African Dwarf (WAD) goats based on haemoglobin polymorphism and its effects on body weight and reproductive parameters. Blood samples collected from 147 mature WAD goats were used for the study. This was subjected to cellulose acetate electrophoresis procedure to reveal the band patterns of haemoglobin. Four genotypes were detected from three co-dominant alleles (A, B and C) in the goats. The frequencies of the A, B and C alleles were 0.42, 0.55 and 0.03, respectively. The difference between the observed and expected genotype was significant (p<0.01) thereby violating Hardy-Weinberg equilibrium. The degree of heterozygosity was while the rate of inbreeding was There was significant (p<0.05) differences in the body weight as affected by Hb type. Significant (p<0.05) differences was also observed in the scrotal length and scrotal circumference as affected by haemoglobin type. However, udder length showed no significant (p 0.05) difference. Scrotal length, scrotal circumference, udder length and body weight of WAD goats were significantly (p<0.05) affected by coat colour of the goats. In conclusion, haemoglobin polymorphism exist in the different phenotypes of WAD goats and this affected body weight, scrotal length, scrotal circumference and udder circumference of the goats. Keywords: Genetic diversity, variation, electrophoresis, zoometric traits, reproductive traits, coat colour INTRODUCTION The West African Dwarf (WAD) goat is sparsely distributed across the Northern and Central part of Nigeria where it makes significant contributions to the livelihoods of impoverished families. It is mostly found in the Southern parts of the country where it is able to thrive and survive due to its hardy nature and its tolerance to the common pest inhibiting ruminant production; the tse-tse fly. The potential of the WAD goats in poverty alleviation programmes are well-recognized, but are still largely untapped. This breed has large range of qualitative variations in coat colour: black, brown, white, pied, mottled, mixed (Odubote, 1994; Ozoje and Mgbere, 2002). Food and Agricultural Organization (FAO, 2008) estimated goat population in Nigeria to be 53.8 million, which ranked Nigeria fifth among selected countries like China ( million), India (125.7 million), Pakistan (60 million) and Bangladesh (56.4 million). Haemoglobin (Hb) is an important protein that has attracted attention because of its biochemical, biophysical and physiological properties, having relevance to the selection phenomenon of animals (Raushenbach and Kamenek, 1978). The structures of proteins enable them to act as catalysts which control the rates of all biological reactions; this makes it possible for them to serve as carriers of essential substances within the organisms, and to serve as regulators of physiological relationships. They also serve as building block units for cellular substances and organic structures (Das and Deb, 2008). Haemoglobin is very important because of its alpha and beta containing polypeptide chains. Tella et al. (2000) reported that after electrophoresis, the Hb genotype that migrated faster from the point of application at ph of was labeled Hb AA while the slow moving fraction was identified as Hb BB and the heterozygote as Hb AB. Bindu and Raghavan (2010) reported on the predominance of Hb A over Hb B in goats. Although there are reported works on haemoglobin polymorphism in selected Nigerian breeds, there is paucity of information on work relating to the relationship between haemoglobin polymorphism and reproductive parameters, as well as the relationship between haemoglobin polymorphism and coat colour of Nigerian goats. This study was therefore carried out to provide some relevant information on these aspects. MATERIALS and METHODS The goat sampling was done in Gulu and its environment. Gulu is a town within Lapai Local Government Area (LGA) of Niger State, Nigeria. One hundred and forty seven West African Dwarf goats of both sexes and of various colours were randomly sampled. The animals were reared under the extensive system of management. Sixty male and eighty seven female animals were sampled for the study. The animals were approximately two years of age. Age was estimated using their dentition. NJAFE VOL. 12 No. 3,

2 Measurement of zoometric traits Body weight (kg) was measured using a simple weighing balance (25 kg capacity). Scrotal length and circumference as well as udder length and circumference were measured using Tailor s measuring tape (cm). Scrotal length and circumference were measured as described by Bratte et al. (1999). Blood sample collection procedure and analysis Blood samples (5 ml) were collected through the jugular vein of the goats and placed in tubes with EDTA (Ethylene-Diamine Tetra-Acetic acid) which acted as an anticoagulant. The tubes were kept in an ice packed container to enhance preservation during transportation. The samples were later kept refrigerated at 0 o C until when needed for analysis. The red cells were separated, washed in saline solution and lysed with distilled water. Haemoglobin was typed using cellulose acetate electrophoresis as described by Imumorin et al. (1999) with a slight modification (Yakubu and Aya, 2012). Identification of the haemoglobin types in goats was achieved in accordance with the migration speed of the light spots on the electrophoretical substratum detected from the start line towards the cathode. Haemoglobin being a coloured protein, the direct gene counting method was used to score haemoglobin bands based on the separation of the haemoglobin. Estimations and Statistical Analysis Genotype and gene frequencies of Hb alleles were estimated according to Hrinca (2008). Genotype frequency of the Hb variants was obtained using the formula: number of AA AA = AB = BB = number of AB number of BB number of BC BC = Where AA+AB+BB+BC is the total genotype sampled. Gene frequencies for the alleles in the populations were obtained using the following expressions: p = f (AA) + 1 f (Aa) = frequency of A 2 q = f (AA) + 1 f (Aa) = frequency of B 2 Where p + q = f (AA) + f (aa) + f (Aa) = 1 The rate of inbreeding per generation (F) was calculated using Lush formula as described by Orville (2008). The formula used was; F = 1 8m + 1 8f Where F = the rate of inbreeding per generation in the population, m= the number of male in the population and f = the number of female in the population. The degree of heterozygosity (H) was obtained using the formula; H = 1 xi n=1 Where x = the gene frequency of the i th allele on the i th locus, and i = the number of loci. The degree of heterozygosity is the expected proportion of heterozygotes in a population under Hardy-Weinberg equilibrium. Hardy-Weinberg s equilibrium was used to test the genotypic ratios based on the binomial (p+q) 2 = p 2 +2pq+q 2 (Hardy, 1908). Data on Hb alleles and of genotype frequencies were subjected to chi-square analysis to test for goodness of fitness for the observed and expected frequencies under Hardy-Weinberg equilibrium. The PROC GLM and PROC T-test procedures of SAS (1993) were used to analyze the effects of haemoglobin variants on zoometric traits of the WAD goats. NJAFE VOL. 12 No. 3,

3 RESULTS The distribution of Hb genotypes and gene frequencies of WAD goats are presented in Table 1. Out of the 60 male animals sampled, only 3 were observed to have Hb AA and Hb BC with a genotype frequency of 0.05, respectively. Those with Hb AB were 36 with genotype frequency of 0.60, while those with Hb BB were 18 with genotype frequency of The gene frequency for the three co-dominant alleles A, B and C was 0.38, 0.60 and 0.02, respectively. In the females, only 3 out of the 87 animals sampled were observed to have Hb AA, 63 of them had Hb AB, 12 had Hb BB while 9 of them had Hb BC with genotype frequency of 0.03, 0.72, 0.14 and 0.10, respectively. The gene frequency for the three co-dominant alleles A, B and C was 0.45, 0.50 and 0.05, respectively. When the data was pooled, out of the 147 animals sampled, only 6 were observed to have Hb AA, 99 had Hb AB, 30 had Hb BB while 12 had Hb BC with genotype frequency of 0.04, 0.66, 0.22 and 0.08, respectively. The gene frequency for the three co-dominant alleles A, B and C was 0.42, 0.55 and 0.03, respectively. The estimated degree of heterozygosity was while the rate of inbreeding was Table 1: Distribution of haemoglobin genotypes and gene frequencies in WAD goats Genotype frequency Gene frequency Sex No AA AB BB AC A B C Male 60 3 (0.05) 36 (0.60) 18 (0.30) 3 (0.05) Female 87 3 (0.03) 63 (0.72) 12 (0.14) 9 (0.10) Total (0.04) 99 (0.66) 30 (0.22) 12 (0.08) AA = haemoglobin AA; AB = haemoglobin AB; BB = haemoglobin BB; AC = haemoglobin AC; estimated heterozygosity = 0.484; estimated local inbreeding coefficient = 0.028; (ratio of the number of genotype to the total number of genotype for male, female and total). The observed and expected numbers of genotypes of Hb in the WAD goats are shown in Table 2. The gene and genotype frequencies of the goats deviated significantly (χ 2 = 27.75; p<0.01) from Hardy-Weinberg equilibrium. Table 3 shows the effect of Hb type in male and female WAD goats on body weight. There were significant (p<0.05) differences in the body weight of the bucks with the Hb BC animals having higher body weight (17.00 ±0.84 kg) and Hb AA animals having lower body weight (10.00±0.84 kg). The does also showed significant (P<0.05) difference in the body weight with does having Hb AB and Hb BB observed to have similar body weights which was higher than in does with Hb AA with body weight of 10.00±2.20 kg. However, does with Hb BC have similar body weight with those having Hb AB and Hb BB. Table 4 shows the effect of haemoglobin type on reproductive parameters of WAD goats. Haemoglobin variant significantly (p<0.05) affected scrotal length and scrotal circumference with bucks having Hb BC observed to have longer scrotum (10.90±0.62 cm) and circumference (20.00±0.50 cm) compared to bucks having the other Hb types. Table 2: Observed and expected number of Hb genotypes in WAD goats Genotype Parameter AA AB BB AC Total Observed Expected Deviation Chi-square ** AA = haemoglobin AA; AB = haemoglobin AB; BB = haemoglobin BB; AC = haemoglobin AC; ** significant (p<0.01). Table 3: Effect of haemoglobin type on body weight of WAD goats Sex AA AB BB AC Male c ± b ± b ± a ±0.84 Female b ± a ± a ± ab ±1.27 Total b ± a ± ab ± a ±0.92 abs: Means with different superscript in the same row are significantly (p<0.05) different; AA = haemoglobin AA; AB = haemoglobin AB; BB = haemoglobin BB; AC = haemoglobin AC; kg±sem. In the does however, no significant (p>0.05) difference was observed in the udder length while udder circumference was significantly (p<0.05) affected. Table 5 shows the effect of Hb type on parameters measured as affected by coat colour of the goats. There was significant (p<0.05) difference in the scrotal length and scrotal circumference of black bucks with bucks possessing Hb AB having longer scrotal length (9.56±0.38 cm) and scrotal circumference (18.76±0.13 cm) while bucks with Hb BB had lower scrotal length (8.90±0.00 cm) and circumference (17.90±0.00 cm). WAD goats with white and black colour showed significant (p<0.05) difference in scrotal length and scrotal circumference as well as body weight with Hb BC animals having longer scrotal length (10.90±0.17 cm), scrotal NJAFE VOL. 12 No. 3,

4 circumference (20.00±0.09 cm) and body weight (14.67±0.53 kg); those with Hb BB were observed to have lower scrotal length (8.00±0.17 cm) and scrotal circumference (17.70±0.06 cm). However, Hb AA animals had lower body weight of (10.00±0.92) kg. There was also significant (p<0.05) difference in the udder length of white WAD goats, does with Hb BB had longer udder (9.00±0.00 cm). The brown WAD goats also showed significant (p<0.05) differences in their udder length; those with Hb BB were observed to have longer udder (10.00±0.00 cm). Table 4: Effects of Hb type on reproductive parameters of WAD goats Genotype Parameter AA AB BB AC Male SL 8.10b ± b ± b ± a ±0.62 SC 18.00b ± b± b ± a ±0.50 Female UL 8.00± ± ± ±0.38 UC 19.80ab ± a ± a ± b ±0.85 abc: Means with different superscripts in the same row are significantly (p<0.05) different; AA = haemoglobin AA; AB = haemoglobin AB; BB = haemoglobin BB; AC = haemoglobin AC; SL = scrotal length; SC = scrotal circumference; UL = udder length; UC = udder circumference; cm±sem. Table 5: Effect of Hb type on body weight and reproductive parameters of WAD goats as affected by individual coat colour Female Male Colour Hb type UL UC SL SC Body weight White and brown AA AB ± ± ±1.43 BB 12.60± ± ±0.01 AC Black AA 8.00± ± ±2.25 AB 9.32± ± a ± a ± ±0.58 BB b ± b ± ±2.25 AC 7.40± ±1.86 White and black AA b ± ab ± b ±0.92 AB 8.20± ± b ± b ± b ±0.46 BB 8.00± ± b ± b ± b ±0.65 AC 8.05± ± a ± a ± a ±0.53 White AA AB 8.20 b ± ± ± ± ±0.46 BB 9.00 a ± ± ± ± ±047 AC Brown AA AB 9.00 b ± ± ± ± ±0.80 BB a ± ± ± ± ±0.58 AC abc: Means with different superscripts in the same column are significantly (p<0.05) different; AA = haemoglobin AA; AB = haemoglobin AB; BB = haemoglobin BB; AC = haemoglobin AC; SL = scrotal length; SC = scrotal circumference; UL = udder length; UC = udder circumference; kg±sem; cm±sem. DISCUSSION Four Hb genotypes (Hb AA, Hb AB, Hb BB and Hb BC) were observed in the WAD goats sampled. The four Hb phenotypes were produced by three co-dominant alleles A, B and C, respectively. Hb C was detected along with Hb B but at a very low frequency (0.03). This low frequency of Hb C in WAD goats may be as a result of stress or harsh weather condition. According to Nigussie et al. (2016), Hb C is synthesized at birth as juvenile Hb along with HB A and exclusively during severe anaemia in the adult sheep. This is at variance with the present study as it was found associated with Hb B in the goat. The situation in the sheep is because sheep with Hb B do not synthesize Hb C and continue to produce their adult Hb even during anaemia. This is because they lack the beta C gene as well as three other genes present in sheep with Hb A (Pieragostini et al., 2010). The result obtained in this study are however similar to the report of Salako et al. (2007) and Alphonsus et al. (2012); they also reported on the existence of four haemoglobin genotypes (Hb A, Hb AB, Hb BB and Hb BC) from three co-dominant alleles (A, B and C) in goats. It was observed that the gene frequency of Hb B was higher than the gene frequencies of Hb A and Hb C. This is in conformity with the observations of Salako et al. (2007) who reported higher frequencies of Hb B (0.72) in Red Sokoto goats. NJAFE VOL. 12 No. 3,

5 The high Hb AB (0.66) is an indication of the level of genetic diversity at the Hb locus in the investigated goat population; it is possible that the mating pattern favoured the production of more Hb AB genotype. The estimated degree of heterozygosity (0.484) falls within the 0.30 and 0.80 reported by Takezaki and Nei (1996) to be appropriate for markers to be used for measuring genetic variation. The rate of inbreeding was low and is in line with the high degree of heterozygosity value, suggesting that the goat population could be undergoing disassortative mating or may be experiencing a Wahund effect (when there is the presence of more heterozygotes than homozygotes in a population). To test for the conformity of the Hb locus of the flock to Hardy-Weinberg equilibrium, chi square (χ 2 ) analysis for the differences between the observed and expected genotype frequencies was carried out and the result showed that the deviation was significant. Thus we may consider this flock to have deviated from Hardy-Weinberg equilibrium for the Hb locus. Bucks and does with Hb BC were heavier. This is in disagreement with Yakubu et al. (2014), who reported heavier body weight in WAD goats with Hb AA. The heavier body weight of goats with Hb AC might be due to favourable natural selective advantage for the genotype which has ensured their survival and proliferation around Gulu. This result differs from the findings of Sam (2012) who reported heavier body weight in agro pastoral goats with Hb AA. The scrotal length and scrotal circumference differences observed in the bucks has implication for the reproductive ability of the bucks having different Hb genotype and coat colour. This is because male reproduction depends largely on spermatozoa production which is related to testicular size (Blottner et al., 1999). It is safe to suggest that bucks with Hb AC in the study area could have greater advantage as far as reproduction is concern. Testicular size is one of the most important factors that could be used to improve the reproductive ability of females. The significantly varied udder circumference observed in the does concurs with the earlier reports of Fernandez et al. (1995) and Amao et al. (2003), who reported differences in udder circumference of non-lactating WAD goats. Udder size has a strong and significant effect on milk yield (Mavrogenis et al., 1988) which makes it an important factor in the machine milk ability of dairy breeds (Fernandez et al., 1995). The wider udder circumference observed in does with Hb AB and Hb BB is an indication that they could be better milk producers than does with Hb AC. Generally, udder circumference is a trait of interest in lactation studies. Differences were observed in the body weight of white and black WAD goats. Goats with Hb AC had heavier body weights. Ozoje and Mgbere (2002) reported that the body weight of WAD goats decreases with increasing coat pigmentation. Adedeji (2012) reported that coat pigmentation has high effects on rectal temperature, respiratory rate measured as breaths/minute, heat stress index and pulse rate measured as beats/minute. These all will affect the growth and reproductive ability of WAD goats in heat stressed areas. CONCLUSIONS The study revealed the existence of four Hb genotypes from three co-dominant allele (A, B and C). Bucks with Hb AC and does with Hb AB had heavier body weights compared to those with Hb AA. Bucks with Hb AC had longer and wider scrotum while does with Hb AB and Hb BB had wider udder. Black bucks with Hb AB and white and black bucks with Hb AC had longer and wider scrotum. White, and brown does with Hb BB had longer udder. REFERENCES Adedeji, T. A Effect of some qualitative traits and non-genetic factors on heat tolerance attributes of extensively reared West African Dwarf (WAD) goats. International Journal of Applied Agricultural and Apicultural Research, 8 (1): Alphonsus, C., Akpa, G. 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