Chromosomal characteristics of Tho-Tho cattle (Bos indicus) in Nagaland, India

Tho-Tho cattle is a semi-wild indigenous cattle available in Nagaland, India. Tho-Tho cattle has been associated with tribal culture of 16 tribes of Nagaland besides its use for meat, milk and draught purposes. A cytogenetic analysis was conducted in a total of 10 numbers of Tho-Tho cattle (5 males and 5 females) from 3 districts of Nagaland hills situated at mean sea level (msl) ranging from 1000 to 10000 ft (4 nos. from one district and 3 nos. each from other 2 districts). The statistical design included 5 males and 5 females Tho-Tho cattle for gathering data on cytogenetic parameters viz. (i) karyotype, (ii) relative length, centromeric index and arm ratio of chromosome and (iii) construction of ideograms. Statistical tools used for analysis of variation of relative length of each autosome, centromeric index; arm ratio of the ‘X’ chromosome between male and female are done by using the Student’s t-test. Duncan's multiple range test (DMRT) was used to isolate means if the effect was found significant. The study revealed that(i) Tho-Tho cattle has 29 pairs of autosomes (ii) out of 29 pairs, 23 pairs of autosomes did not differ significantly (P > 0.05) between male and female Tho-Tho cattle in terms of relative length (iii) autosomes are acrocentric, (iv) relative length of 4th, 5th, 6th, 7th and 9th autosomes are significantly (P < 0.05) higher in male; however, 19th autosome of female is significantly (P < 0.05) higher than male (v) X-chromosome in both the sexes is clearly distinguishable and is submetacentric (vi) Y-chromosome (to the total haploid genome) of male Tho-Tho cattle is 1.77 ± 0.10% and it is acrocentric (vii) centromeric index of “X” chromosome in male is 33.75% and in female 32.76% and (viii) Arm ratio of “X” chromosome is found to be 0.66 in male and 0.67 in female.