Dataset Information

Short communication: A practical farm-based trial to compare ewe nematode control strategies in peri-parturient ewes.

ABSTRACT: The focus of gastro-intestinal parasite control in the sheep industry is increasingly on finding a balance between maintaining productivity of the flock whilst minimising selection for anthelmintic resistance to preserve anthelmintic efficacy for the future. Periparturient ewes represent the major source of gastro-intestinal parasites for growing lambs and are therefore a priority for parasite control. This study examines the impact on ewe faecal egg counts (FECs), lamb FECs, lamb daily live weight gains (DLWGs) and pasture larval counts of treating groups of ewes two weeks prior to lambing with either, a long-acting moxidectin treatment, short-acting doramectin or control. Six groups of twenty ewes were allocated to individual paddocks, two groups allocated to each treatment, and weekly faecal sampling was performed throughout from the ewes and from six weeks after the start of lambing in the lambs. Treatment group was found to have a significant effect on both ewe FEC (p<0.001) and lamb FEC (p = 0.001) with the group receiving the long-acting anthelmintic having the lowest ewe and lamb FECs. There was no significant effect on the DLWGs of the lambs. Pasture larval counts at the end of the study period were lowest in the long-acting wormer treatment group. The use of long-acting moxidectin may be helpful as part of a parasite control programme by reducing the worm burdens of ewes and their lambs, decreasing the number of anthelmintic treatments required in that year and by reducing pasture contamination for those sheep which will graze the pasture in the next year. However, like all anthelmintics, its use should be judicious to avoid selection for resistance.

SUBMITTER: Kerr CL

PROVIDER: S-EPMC7425951 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Short communication: A practical farm-based trial to compare ewe nematode control strategies in peri-parturient ewes.

Kerr Charlotte L CL Armstrong David R DR Anderson Alison J AJ

PloS one 20200813 8

The focus of gastro-intestinal parasite control in the sheep industry is increasingly on finding a balance between maintaining productivity of the flock whilst minimising selection for anthelmintic resistance to preserve anthelmintic efficacy for the future. Periparturient ewes represent the major source of gastro-intestinal parasites for growing lambs and are therefore a priority for parasite control. This study examines the impact on ewe faecal egg counts (FECs), lamb FECs, lamb daily live wei ...[more]

PMID: 32790679

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Project description:This study estimated genetic parameters for ewe reproductive traits [number of lambs born (NLB) and weaned (NLW) per ewe lambing] and fecal egg counts (FEC) during the peri-parturient rise (PPR) for use in genetic evaluation of Katahdin sheep. Data included NLB and NLW for 23,060 lambings by 9,295 Katahdin ewes, 1,230 PPR at lambing (PPR0) for 750 ewes, 1,070 PPR at approximately 30 d postpartum (PPR30) for 611 ewes, BW at birth, weaning, and (or) post-weaning for 12,869 lambs, and FEC at weaning and (or) post-weaning for 4,676 lambs. Direct additive, permanent environmental, and residual (co)variances were estimated in univariate and bivariate animal models. Fixed effects included effects of ewe management group and ewe age for all traits, and, for PPR, a continuous effect of days between lambing and measurement. Effects of litter size on PPR0 and number of lambs suckled on PPR30 were included in univariate models but excluded from bivariate models for PPR and NLB or NLW. Heritability estimates in univariate models for NLB, NLW, PPR0, and PPR30 were 0.09 ± 0.01, 0.06 ± 0.01, 0.35 ± 0.06, and 0.24 ± 0.07, respectively. Estimates of permanent environmental variance as a proportion of total phenotypic variance were 0.02 ± 0.01 for NLB, 0.03 ± 0.01 for NLW, 0.05 ± 0.06 for PPR0, and 0.13 ± 0.07 for PPR30. Direct additive, phenotypic, permanent environmental, and residual correlations between NLB and NLW were 0.88 ± 0.03, 0.74 ± 0.004, 0.54 ± 0.15, 0.74 ± 0.003, respectively; corresponding correlations between PPR0 and PPR30 were 0.96 ± 0.07, 0.46 ± 0.03, 0.98 ± 0.50, 0.18 ± 0.05, respectively. The additive genetic correlation (rd) between ewe reproductive traits and PPR ranged from 0.12 to 0.18. Estimates of rd between lamb BW and subsequent ewe NLB and NLW ranged from 0.07 to 0.20, and those between PPR and lamb BW ranged from -0.03 to 0.29. The rd between ewe reproductive traits and lamb FEC ranged from 0.27 to 0.40, and those between PPR and lamb FEC ranged from 0.56 to 0.77. Correlations between maternal additive effects on BW and direct additive effects on PPR were low (-0.08 to 0.10), and those between maternal additive effects on BW and direct additive effects on ewe reproductive traits were variable (-0.36 to 0.11). We conclude that FEC in growing lambs and peri-parturient ewes are controlled by similar genes and that modest, but manageable, genetic antagonisms may exist between FEC and ewe productivity.

Project description:Global livestock production is facing serious new challenges, including climate-driven changes in parasite epidemiology, and anthelmintic resistance, driving a need for non-chemotherapeutic methods of parasite control. Selecting for genetic resistance to gastrointestinal nematode infection could reduce reliance on chemical intervention and mitigate increases in parasite challenge due to climate change. Ewes of the composite Exlana breed with a range of estimated breeding values (EBVs) based on nematode faecal egg counts (FECs) were monitored during the peri-parturient period on two farms in southwestern England. Ewes with low EBVs ("resistant") had lower FECs during the peri-parturient period than those with high EBVs ("susceptible"): the mean FEC was reduced by 23% and 34% on Farms 1 and 2, respectively, while the peak FEC was reduced by 30% and 37%, respectively. Neither EBV nor FEC were correlated with key performance indicators (estimated milk yield, measured indirectly using 8?week lamb weight, and ewe weight loss during lactation). Simulations predict that the reduced FECs of resistant ewes would result in a comparable reduction in infection pressure (arising from eggs shed by ewes) for their lambs. Furthermore, although the reduced FECs observed were modest, simulations predicted that selecting for nematode resistance in ewes could largely offset predicted future climate-driven increases in pasture infectivity arising from eggs contributed by these ewes. Selective breeding of the maternal line for nematode resistance therefore has potential epidemiological benefits by reducing pasture infectivity early in the grazing season and alleviating the need for anthelmintic treatment of ewes during the peri-parturient period, thus reducing selection pressure for anthelmintic resistance. These benefits are magnified under predicted future climate change. The maternal line warrants more attention in selective breeding programmes for nematode resistance.

Dataset Information

Short communication: A practical farm-based trial to compare ewe nematode control strategies in peri-parturient ewes.

Publications

Short communication: A practical farm-based trial to compare ewe nematode control strategies in peri-parturient ewes.

Similar Datasets

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