|NOTTER, DAVID - Virginia Tech|
|MILLER, JAMES - Louisiana State University|
|MORGAN, JIM - Katahdin Hair Sheep International|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2016
Publication Date: 2/2/2017
Citation: Notter, D.R., Burke, J.M., Miller, J.E., Morgan, J.L. 2017. Factors affecting fecal egg counts in peri-parturient Katahdin ewes and their lambs. Journal of Animal Science. 95(1):103-112.
Interpretive Summary: Selection for low fecal egg counts (FEC) can be used to genetically enhance resistance to internal parasites in lambs, thereby reducing the need for dewormer and dewormer resistance by the parasite, and increasing the marketability of organic lamb. Ewes are also susceptible to parasitism around the time of lambing, but little is known about factors that contribute to this susceptibility and effects on offspring. Scientists from Virginia Tech, Agricultural Research Service - Booneville, AR, Louisiana State University, and Katahdin Hair Sheep International determined that fecal egg counts in ewes peak at 28 days post-lambing, younger and older ewes, and those that raise multiple compared with single lambs are more susceptible to parasitism. This information is important to sheep producers, scientists, veterinarians, and extension specialists aiming to minimize parasite problems in sheep.
Technical Abstract: Selection for low fecal egg counts (FEC) can be used to genetically enhance resistance to gastrointestinal nematode parasites in growing lambs, thereby reducing the frequency of use of anthelmintics, facilitating marketing of organic lamb, and reducing the risk of development of anthelmintic resistance by the parasite. Recording of FEC in lambs has thus been incorporated into several national sheep genetic evaluation programs. Ewes in late gestation and early lactation are also vulnerable to parasite infection and commonly experience a peri-parturient rise in FEC. This study was designed to assess factors associated with the peri-parturient rise in FEC in Katahdin ewes and associated changes in FEC in their lambs. Data came from 1,487 lambings by 931 Katahdin ewes from 11 farms in the Eastern USA. Fecal egg counts were measured in ewes at approximately 0, 30, and 60 d postpartum and in their lambs at approximately 60, 90, and 120 d of age. Approximately 1,400 lambs were evaluated at each measurement age. Data were analyzed separately for ewes and lambs and also initially analyzed separately for each measurement time. Repeated-measures analyses were then used to evaluate responses across measurement times. In ewes, FEC peaked at approximately 28 d postpartum, and we concluded that informative peri-parturient FEC could be obtained from 1 wk before until approximately 5 wk after lambing. Yearling ewes had higher FEC than adult ewes (P < 0.01), and ewes that nursed twin or triplet lambs had higher FEC than ewes that nursed single lambs (P < 0.01). In lambs, FEC increased through approximately 120 d of age. Lambs from yearling ewes and lambs nursed in larger litters were, like their dams, at greater risk of parasitism (P < 0.05). Ewes and lambs in these groups would benefit from enhanced monitoring of parasite loads at lambing and in early lactation. Significant correlations between FEC in lambs at 90 d of age and FEC in ewes at 0, 30, and 60 d postpartum support the presence of a genetic relationship between these two indicators of parasite resistance.