Study of genetic diversity in malabari goats (capra hircus) utilizing biochemical and immunological markers

Abstract

Goat populations of Tanur, Thalassery and Badagara were studied for biochemical polymorphisms, immunological and microsatellite markers to investigate the similarities and differences between these populations.

With regard to biochemical markers tested, polymorphism was observed only for haemoglobin, transferrin and glutathione loci. Two variants were observed for haemoglobin, Hb A and Hb B with a frequency of 0.987 and 0.012, respectively, suggestive of three phenotypes, viz. Hb AA, Hb AB and Hb BB, and indicating the predominance of Hb A in the pooled population. Hb B variant was observed only in the Thalassery population (gene frequency 0.038).

Two variants for transferrin (TfA and Tf B) were detected with a predominance of TfA in the population. All the goats from Thalassery population belonged to Tf AA type. In the present study only two phenotypes as regards transferrin locus could be observed, (Tf AA and Tf BB) with the notable absence of Tf AB. No polymorphism was observed for albumin, cerruloplasmin, amylase and carbonic anhydrase loci in all the animals tested.

The animals were classified as low and high glutathione types based on the values obtained for blood glutathione concentration. In the pooled population, majority of the animals belonged to low GSH type (53.68 per cent). The least square analysis of glutathione concentrations showed significant variation between populations.

With regard to potassium loci, all the animals in the present study belonged to low potassium type, with the mean potassium concentration of the pooled population recorded at 4.18 + 0.09 meq/l. The least square analysis of variance of potassium concentrations showed that there existed significant difference between different sub-populations.

Genetic distance was calculated as described by Balakrishnan and Sanghvi (1968), using the allelic frequencies of protein polymorphic loci. Genetic distance between Tanur and Badagara was found to be 0.1249 , while that between Tanur and Thalassery was 0.6690 and between Badagara and Thalassery was 0.3351. The only possible conclusion that could be arrived at from the above studies is the existence of a relationship between these populations. Hence an attempt was made to study the different populations at molecular level, using microsatellite markers. Three markers, viz. INRA 063, HUJ 1177and ILSTS 030 were found to be polymorphic. Based on the genetic distances, it was found that Thalssery and Badagara were closely related than Tanur population.. This finding, much in agreement with biometrical traits, reiterates the close relationship between the Thalassry and Badagara populations. On an average, the goats of Thalassery and Badagara were heavier in comparison to Tanur goats, though the prolificacy remained higher in Tanur animals than the other two populations.

The different sub-populations under the present study were also screened for the antibody response to SRBC. The highest concentration of antibody was observed on day seventh after primary immunization. The titre gradually reduced by the 15th day, reaching the lowest values on 21st day of post immunization. The effect of antibody response to SRBC on the 7th, 15th and 21st days post immunization was not found to be significant for the occurrence of diseases like diarrhoea and pneumonia.

The cutaneous response to intradermal injection to Phytahaemagluttinin – M (PHA-M) was also studied to find out the differences, if any in and between the various sub- populations under study. The values for skin thickness were maximum at 24 hours post-intradermal injection of PHA-M and were recorded as 3.24±0.05, 3.23±0.06 and 3.33±0.06 mm in Tanur, Thalassery and Badagara, respectively. The skin thickness reduced considerably after 48 hours and reached 1.61±0.02, 1.62±0.02 and 1.65±0.02 mm, respectively at 72 hours. The least square analysis of variance revealed that the values for pre and post immunization skin thickness at 0, 24, 48 and 72 hours were non significant between different sub-populations.

Total protein, albumin and globulin concentrations also were estimated. The highest mean concentration for globulin was detected in Badagara population (3.28±0.22g/dl) and the lowest in Tanur (2.340 ± 0.31g/dl). The least square analysis of variance of globulin concentration revealed significant difference between populations.

Though all populations under study had all predominant physical characteristics of the Malabari breed, the Tanur population stood apart as regards the biometrical characteristics, like litter size and body weight and charecteristics perceivable at the molecular level. It could well be inferred that this population might have evolved through mixing up of the local nondescript Tanur goats with original Malabari goats. The study reiterates the need for more research activities directed at exploring the chances of conserving and developing such unique populations within a breed.