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ARS Home » Southeast Area » Booneville, Arkansas » Dale Bumpers Small Farms Research Center » Research » Publications at this Location » Publication #398031
Research Project: Sustainable Small Farm and Organic Grass and Forage Production Systems for Livestock and Agroforestry

Location: Dale Bumpers Small Farms Research Center

Title: The impact of sire parasite resistance on offspring gastrointestinal nematode indicators, and relative impact of lamb breeding values on sale value of ram lambs

Author
item Burke, Joan
item POPP, MICHAEL - UNIVERSITY OF ARKANSAS
item ANDERSON, JOHN - UNIVERSITY OF ARKANSAS
item MILLER, JAMES - LOUISIANA STATE UNIVERSITY
item NOTTER, DAVID - VIRGINIA TECH

Submitted to: American Society of Animal Science Southern Section Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 11/30/2022
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Genetic selection of sheep for resistance to gastrointestinal nematodes (GIN) has become a priority for pasture-based production of lambs to minimize the need for deworming. The first objective of this experiment was to determine the impact of sire weaning or post-weaning fecal egg count (FEC) estimated breeding value (EBV; WFEC and PFEC, respectively) from the National Sheep Improvement Program (NSIP) on GIN infection in Katahdin lambs born in fall (Oct – Nov; n = 459) or winter (Jan – Feb; n = 378) of 2018 through 2021 at the USDA Agricultural Research Service (ARS). FAMACHA scores were determined, and blood samples and feces were collected from the lambs to determine packed cell volume (PCV), and FEC at 60, 90, 120, and 150 d of age, and lambs were selectively dewormed if anemic. Data were analyzed using mixed models containing fixed effects of year, sex, age at sampling (fitted as a repeated measure), and their interactions, and continuous effects of sire FEC EBV. The offspring FEC was positively (P < 0.001) and the PCV negatively (P < 0.001) related to the sire WFEC and PFEC. A second objective was to examine effects on sale prices of breeding-quality ram lambs from four farms, including ARS, of lamb EBV for WFEC and a ewe productivity trait (EPT) designed to identify ewes with superior maternal ability. Sale price effects were dominated by sale type with a premium of $1,086/hd relative to direct sales from the farm for animals in NSIP or Katahdin Hair Sheep International Expo sales. Producers likewise assigned a premium of $107/hd to animals retained for use in their own breeding herds. The next most impactful variable was the EPT EBV. A 1-SD increase of 2.3 units in EPT yielded an extra $39/hd whereas a similar 1-SD decrease in EPT resulted in a $32/hd discount. Lambs born in fall were discounted by $6/hd relative to those born in winter. Lambs that were not dewormed received a $29/hd premium over lambs that were dewormed and was presumably taken as a phenotypic signal that the lamb was resistant. A ±1-SD change in WFEC had no effect on sale value, which changed by less than $0.01/hd. This result may have been confounded with whether the lamb had been dewormed. Thus, while more parasite-resistant sires produced offspring with lower FEC, the sale value of these ram lambs appeared to have been more strongly associated with other EBV such as EPT or with a desire to obtain ram lambs with balanced EBV rather than elite EBV for parasite resistance.