Murphy Thomas W, Burke Joan M, Hess Andrew S, Miller James E, Wood Erin L, Acharya Mohan
USDA, ARS, Livestock Bio-systems Research Unit, Roman. L. Hruska U.S. Meat Animal Research Center, Clay Center, NE 68933, USA.
USDA, ARS, Dale Bumpers Small Farms Research Center, Booneville, AR 72927, USA.
Transl Anim Sci. 2024 Dec 12;8:txae174. doi: 10.1093/tas/txae174. eCollection 2024.
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, = 1766; winter-organic = W-O, = 190; fall-conventional = F-C, = 846; and fall-organic = F-O, = 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 (< 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, (< 0.01) not different at 120 d, and greater for W-C at 150 d (< 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 (≤ 0.04). This was the first study conducted in the U.S. to compare longitudinal performance between lambs born in different seasons and reared in different production systems. Under the conditions of this study, organically managed lambs had similar performance to their conventionally managed counterparts. However, large differences in GIN infection risk over time existed between birth seasons and deworming regimens which have important implications for producer management decisions and genetic improvement programs.
胃肠道线虫（GIN）感染对全球以牧草为食的绵羊的生产性能和健康状况产生不利影响。本研究的目的是估计不同出生季节和生产系统之间，羔羊断奶后生长以及GIN感染指标的纵向差异。2006年至2022年期间，在一个单一羊群中收集了关于卡他丁羊的数据。羔羊出生于冬季或秋季，并在传统或认证有机生产系统中饲养。四个亚群被定义为出生季节和生产系统的组合（冬季 - 传统 = W - C，n = 1766；冬季 - 有机 = W - O，n = 190；秋季 - 传统 = F - C，n = 846；秋季 - 有机 = F - O，n = 189）。所有羔羊均因先前放牧的牧场而自然感染GIN，约60日龄断奶，并在整个断奶后阶段留在牧场上。在大约90、120和150日龄时记录羔羊体重（BW），并对粪便虫卵计数和血液红细胞压积（PCV）进行量化。在分析之前，对粪便虫卵计数进行对数转换（LFEC）。最初在收集时间点内对性状进行分析，以比较所有4个亚群。同一季节出生的传统饲养羔羊和有机饲养羔羊在150日龄时的最终体重以及整个断奶后阶段的LFEC和PCV相似。然后使用重复测量模型分析W - C和F - C羔羊随时间的记录。收集时间点×驱虫处理×亚群交互效应对于所有性状均具有显著意义（<0.01）。在不需要驱虫的羔羊中，未观察到出生季节之间体重的差异。然而，未处理的F - C和W - C羔羊的LFEC趋势几乎完全相反，90日龄时F - C更高（<0.01），120日龄时无差异，150日龄时W - C更高（<0.01）。此外，未处理的F - C羔羊在90日龄时的PCV较低，但在120和150日龄时高于未处理的W - C羔羊（≤0.04）。这是美国首次进行的一项研究，比较不同季节出生并在不同生产系统中饲养的羔羊的纵向生产性能。在本研究条件下，有机管理的羔羊与传统管理的羔羊表现相似。然而，出生季节和驱虫方案之间随时间存在GIN感染风险的巨大差异，这对生产者管理决策和遗传改良计划具有重要意义。
