Introduction

Mongolia produces about 25 per cent of the world's cashmere production. In the last five years, there has been a 66 per cent increase in the production of raw cashmere. Cashmere was quickly established as a major export product. The increase in cashmere is mainly conditioned by the increase in goat numbers which may effect negatively the balance of nature and ecology and herd composition of traditionally five kinds of animals. At present, goat breeders are attempting to improve the genetic potential of their goats but the lack of genetic and phenotypic parameters precludes the design of selection and breeding programmes. There have been few reports published in the world on inheritance of cashmere production (Miller, 1986). Researchers have estimated the heritability of combed cashmere weight in Indian Changtang goat and of sheared weight in Australian feral ones (Pattie et al.,1989). A research project which aims to determine the inheritance of production characteristics of Mongolian goats has been carried out since 1991 at the experimental farm "Zaamar", Mongolia. This paper presents genetic and phenotypic correlations and a selection index for estimating the breeding value of Mongolian goats.

Materials and methods

Records for production characteristics of 68 offspring in their first year, obtained from 4 sires, have been used in the study. Heritability, phenotypic and genetic correlations of production characteristics were estimated by paternal half-sib correlations. The economic value of down weight was calculated from current Mongolian market values. The economic value of down diameter was calculated assuming a linear relationship between down diameter and average cashmere price across the 3 current payment bands and assuming average yield. The full index including the three traits was calculated using the matrix technique as described by Cunningham (1972).

Results and discussion

Heritability for productivity is classed as follows: high for down weight, moderate for down diameter and weak for down length and live weight (Table 1). There was strong positive genetic and phenotypic correlation between live weight and down weight. In contrast, there were weak positive genetic correlations between down diameter and both down diameter and down length, and finally, a negative weak correlation between down diameter and live weight. There is no estimate of heritabilities for production characteristics of Mongolian goats in the literature. Heritabilities of traits, except down weight for Mongolian goats, are lower than those for Australian feral goats (Pattie et al., 1989), Australian cashmere goats and New Zealand cashmere goats. They used sheared and dehaired fibres for their estimates.

Table 1. Some phenotypic and genotypic parameters for production characteristics for one year old offspring.

Heritability (on diagonal), phenotypic (above diagonal) and genotypic (below diagonal) correlations. *standard errors

The strong phenotypic and genetic correlations between down weight and length of down indicate that the latter may be used as an indirect indicator of down weight for preliminary selection. The selection of goats with above-average down length relative to its contemporaries will also result in the selection of an animal with above-average down weight. Our findings are in a good agreement with those of Pattie et al. (1989) in this respect. It is possible to improve down production of Mongolian goats while maintaining or not decreasing live weight and fibre quality. In particular, there is a considerable scope to measure down weight by mass selection.

Table 2 shows a full selection index including three traits and the expected responses. Down weight had a high relative importance as compared to the other traits indicating that it makes the largest contribution to the genetic gain when selection is applied. Little is lost if diameter or live weight are omitted from the index.

Table 2. Selection index for Mongolian goats

• b- partial regression coefficients
• v%- percentage reduction in rate of expected response for aggregate genotype when variate is dropped.
• ER- expected response in each trait in actual units of measurement.

Use of this selection index would combine the simultaneous genetic improvement of above mentioned three traits in an optimum way.

Conclusions

Results arising from our study provide the necessary basis for the design of efficient selection programmes for experimental goat flocks. Some preliminary phenotypic and genetic parameters now available allow the estimation of breeding values for production characteristics and the construction of a selection index.

References

Cunningham, E.P., 1972. Theory and application of statistical selection methods. XIV British Poultry Breeders Round Table, Birmingham, pp. 35-37.

Miller, P., 1986. The performance of cashmere goats. Anim. Breed. Abstr., 54:181-199.

Pattie, et al. 1989. Breeding for cashmere and mohair. Proc. 4th World Congress on Genetics Applied to Livestock Production. 15: 167-176.

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