Skip to main content
ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Livestock Bio-Systems » Research » Publications at this Location » Publication #416898

Research Project: Discovery of Novel Traits to Improve Efficiency and Sustainability of Different Sheep Production Systems

Location: Livestock Bio-Systems

Title: Impacts of birth season and production system on gastrointestinal parasitism and growth in Katahdin lambs

Author
item Murphy Jr, Thomas
item Burke, Joan
item HESS, ANDREW - University Of Nevada
item MILLER, JIM - Louisiana State University
item WOOD, ERIN - Dale Bumpers Small Farms
item ACHARYA, MOHAN - Lincoln University Of Missouri

Submitted to: Translational Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2024
Publication Date: 12/12/2024
Citation: Murphy, T.W., Burke, J.M., Hess, A.S., Miller, J.E., Wood, E.L., Acharya, M. 2024. Impacts of birth season and production system on gastrointestinal parasitism and growth in Katahdin lambs. Translational Animal Science. 8. Article txae174. https://doi.org/10.1093/tas/txae174.
DOI: https://doi.org/10.1093/tas/txae174

Interpretive Summary: Gastrointestinal nematodes (GIN) are internal parasites that plague forage-based sheep operations worldwide. High levels of blood-feeding GIN infection result in anemia, reduced growth, and increased mortality. Overuse of chemical dewormers has resulted in GIN resistance. Furthermore, the use of chemical dewormers is restricted for most organic certification programs. Future GIN management will require multiple control strategies including genetic selection for host resistance and husbandry alterations to better align susceptible stages of production with reduced environmental GIN abundance. This was the first study conducted in a U.S. sheep population to estimate the impacts of production system (conventional vs. organic) and birth season (winter vs. fall) on lamb growth and GIN infection. Historical records collected over nearly 20 yr from pasture reared Katahdin lambs were analyzed. Performance was similar between conventional and organically managed lambs. While lambs born in different seasons had similar ending body weight, major differences in GIN infection were observed. Fall born lambs had greater GIN infection shortly after weaning which gradually waned over time and the opposite was found for winter born lambs. Results can be used to aid the producer decision making process to balance expected returns and costs of alternative management strategies.

Technical Abstract: Gastrointestinal nematode (GIN) infection adversely affects the performance and well-being of forage-based sheep throughout the world. The study objectives were to estimate longitudinal differences between birth seasons and production systems for lamb postweaning growth and indicators of GIN infection. Data were collected on Katahdin lambs within a single flock from 2006 to 2022. Lambs were born in either the winter or fall and reared in conventional or certified organic production systems. Four sub-flocks were defined as the combination of birth season and production system (winter-conventional = W-C, n = 1766; winter-organic = W-O, n = 190; fall-conventional = F-C, n = 846; and fall-organic = F-O,n = 189). All lambs were naturally infected with GIN from previously grazed pastures, weaned at approximately 60 d of age, and remained on pasture throughout the postweaning phase. At approximately 90, 120, and 150 d of age lamb body weight (BW) was recorded, and fecal egg count and blood packed cell volume (PCV) were quantified. Fecal egg count was log-transformed (LFEC) prior to analyses. Traits were initially analyzed within collection timepoint to compare all 4 sub-flocks. Final BW at 150 d and LFEC and PCV throughout the postweaning phase were similar between conventional and organic lambs born in the same season. Repeated measures models were then used to analyze records from W-C and F-C lambs over time. The collection timepoint × deworming treatment × sub-flock interaction effect was significant for all traits (P < 0.01). Within lambs that did not require deworming, no difference in BW between birth seasons was observed. However, LFEC trends for untreated F-C and W-C lambs were nearly exact opposite of one another, being greater for F-C at 90 d, (P < 0.01) not different at 120 d, and greater for W-C at 150 d (P < 0.01). Additionally, PCV of untreated F-C lambs was lower at 90 d but greater at 120 and 150 d than untreated W-C lambs (P