Scottish Blackface ewes more resistant to parasites than Greyface ewes
Take Home Message: Scottish Blackface ewes are more resistant to internal parasites and will shed less worms in their faeces around lambing compared with Greyface ewes.
Scottish Blackface ewes could be genetically more resistant to nematode parasite infection than Greyface ewes. That was just one of the conclusions of research carried out, by scientists based in Scotland and Greece, to find out if one breed was truly more resistant than another to worm infection.
“We know that the extent of periparturient relaxation of immunity (PPRI) to gastrointestinal nematode parasites is sensitive to metabolisable protein scarcity, but that it also varies between breeds of sheep,” the SAC’s Jos Houdijk told delegates at this year’s British Society of Animal Science’s annual conference.
“For example, under ad-lib feeding conditions, Scottish Blackface ewes had a lower extent of immunity depression at lambing than Greyface ewes. But such between-breed variation may not necessarily be associated with genetic resistance per se but could arise from a higher nutrient demand of the more productive Greyface ewes.”
He explained that the team’s experiment was designed to test the hypothesis that if the extent of PPRI has only a nutritional basis, then the sensitivity of this immunity to MP scarcity will not differ between the breeds when MP feeding is adjusted for between-breed differences in MP demand.
The trial involved twin-rearing Scottish Blackface ewes and Greyface ewes that were ‘trickle infected’ with 10,000 infective worm larvae three times a week from 40 days prior to lambing. From 24 days before lambing to 31 days after lambing, ewes were fed a restricted ration that was 0.9 times their metabolisable energy requirement, and fed at either 0.8 or 1.3 times their estimated MP requirements.
These requirements were 85 and 120g MP/day during late pregnancy and 230 and 295g MP/day during lactation for the Blackface and Greyface ewes respectively. Ewes and their lambs were weighed weekly and within 12 hours post lambing. Ewe faecal egg count (FEC) was assessed twice a week as an indicator for PPRI and analysed.
“And we found that feeding treatment and breed did not interact for post parturition ewe body weight But ewes fed the high protein ration were heavier than ewes fed the lower protein ration – 58.7kg compared to 57.1kg,” said Dr Houdijk.
“During pregnancy and lactation, the effects of all combinations of feeding treatment breed and time on ewe body weight were not significant. But feeding treatment and breed did ‘interact’ for litter birth weight,” he explained. “Litters of high-protein ration fed Greyface ewes were heavier at birth than low-protein ration fed Greyface ewes.”
Time and breed and time and feeding treatment had an effect on litter body weight. And this was reflected in differences in average daily weight gain. Greyface litters grew faster than Blackface litters – 615g/day compared to 444g/day. And high protein fed ewe litters grew faster than low protein litters – 616g/day compared to 453g/day.
“During late pregnancy, all first and second order interaction effects on FEC were not significant. Blackface ewes had lower FEC than Greyface ewes and low-protein ration fed ewes had higher FEC than high-protein ration fed ewes.
“But breed and feeding treatment interacted on FEC during lactation. MP scarcity increased FEC in Greyface ewes but not in Blackface ewes,” added Dr Houdijk.
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