**8.1 Breeding for resistance**

Identification of resistant individuals is necessary for the production of parasiticresistant breeds. Two parameters are mostly reported for the selection of resistant breeds, i.e., FEC, which is an indirect parameter for measurement of the relative level of infection [82]. Hematocrit and PCV are being used for the identification of worm burden, especially in the case of *H. contortus*. In Australia, FEC both in natural and artificial infections has been used for many years to select the animals for parasitic resistance [83].

The researchers cannot divide the magnitude of resistance into discrete genetic units; therefore, the resistance is described in the form of heritability estimates [84]. The phenotype of quantitative traits is regulated by the additive effect of specialized genes [85], which are yet to be identified. The resulting resistance may be attributed to the effect of a combination of many small genes or a group of major genes that are being regulated not only by additive effects but also by the environmental effects [84].

#### **8.2 Genetic and phenotypic parameters for worm resistance**

Packed cell volume and fecal egg count are the most useful markers/parameters to estimate the response of host challenge and natural infection with nematodes present in GI in general and specifically *H. contortus*. Both PCV and FEC are heritable traits. Heritability of FEC ranges from 0.04 to 0.37. Morris *et al*. [86] described a heritability estimate of 0.05 in Saanen goats at the age of 12 months in New Zealand, and Woolaston *et al*. [87] described a heritability estimate of 0.04 and 0.08 in Fijian goats at 12 months of age in Fiji. [88]. Similar studies have been conducted in Kenya where they found FEC heritability estimates of 0.15, 0.16, and 0.12 in small East African goats at the age of 4, 5, 8, and 10 months, respectively. Some more studies have been conducted by Vagenas *et al*., [89] in Scotland, and they found 0.37 and 0.32 estimates of heritability for FEC in Scottish Cashmere goat's breed.
