Estimates of genetic parameters for faecal egg count of Haemonchus contortus infection and relationship with growth traits in Avikalin sheep

Abstract

Genetic parameters for faecal egg count were estimated in naturally challenged Avikalin sheep developed and maintained at Central Sheep & Wool Research Institute, Avikanagar, India, over a period of 4 years (2004-2007). The data on faecal egg count for 433 animals descended from 41 sires, and 151 dams were used for the study. Genetic analyses were carried out using restricted maximum likelihood, fitting an animal model and ignoring or including maternal genetic or permanent environmental effects. Direct heritability for the trait was 0.149 +/- 0.096 when maternal effects were ignored. In the model which takes in to account direct genetic, maternal genetic and maternal permanent environment effect together, it was observed that maternal heritability (m(2)) accounts for 0.6% of total variation whereas maternal permanent environmental effect (c(2)) accounts for 6.14% of total phenotypic variation. Effect of faecal egg count on the growth characteristics was observed to be significant. It was seen that wherever FEC was high, body weight or average daily gain declined in active infective stage. After termination of the infection, these effects were found to be non-significant. Result suggests that direct genetic and maternal permanent environmental effects were important for this trait; thus, they need to be considered for improvement in the trait.

Genetic and environmental influences on faecal nematode egg counts of Jamunapari goats in India

“…The estimates of direct heritabilities (0.11 to 0.16) of FEC in the present study were similar to the findings of Woolaston and others (1992) in adult meat‐type goats (0.08) and Baker and others (2001) in Galla and small East African goats (0.12). Similarly, the present estimates are in the same range as those obtained by Greeff and Karlsson (1998), Gauly and Erhardt (2001) and Prince and others (2010) in sheep. However, higher estimates (Rohrer and others 1991, Mandonnet and others 2001) and lower estimates (Morris and others 1997) than the present findings have been observed in other goat breeds.…”

“…Similarly, the present estimates are in the same range as those obtained by Greeff and Karlsson (1998), Gauly and Erhardt (2001) and Prince and others (2010) in sheep. However, higher estimates (Rohrer and others 1991, Mandonnet and others 2001) and lower estimates (Morris and others 1997) than the present findings have been observed in other goat breeds.…”

“…The estimate of permanent environmental maternal effects (c 2 =0.09) for FEC in Jamunapari goats (Table 3) was comparable with the findings of Mandonnet and others (2001) in Creole goats (0.13) and Mandal and Sharma (2008) in Barbari goats (0.10). The lower estimates of c 2 effects for FEC was also reported in Scottish Blackface sheep (0.06) by Bishop and others (1996) and in Avikalin sheep (0.07) by Prince and others (2010). The low maternal heritability (m 2 =0.00 to 0.06) estimates for FEC in this study was similar to the earlier findings of Mandal and Sharma (2008) in Barbari goats (0.04).…”

Candidate Gene Approach for Parasite Resistance in Sheep – Variation in Immune Pathway Genes and Association with Fecal Egg Count

“…Similarly, within-breed genetic variation has also been demonstrated in diverse sheep populations including Merino [11], Romney [12], Scottish Blackface [13], feral Soay sheep [14], etc. Estimation of genetic parameters revealed low to moderate heritability in different sheep populations (h 2  = 0.149, Avikalin sheep [15] to h 2  = 0.41, Armidale sheep [16]). …”

Impact of treatment of gastrointestinal nemathelminths on body weight of sheep and goats

“…but not upto such extend when these drugs are 100 % effective. Prince et al (2010) reported that there is a direct effect of faecal egg count on growth characteristics i.e. whenever faecal egg count is high, average daily weight gain declines.…”