# Cross-Sectional Study Assessing Management Practices and Udder Health in California Sheep Flocks and Seroprevalence of Small Ruminant Lentivirus

## TL;DR

This study surveyed California sheep producers to assess udder health and SRLV seroprevalence, finding that larger flocks and extensive management practices may increase udder abnormalities.

## Contribution

The study provides new insights into udder health management and SRLV prevalence in California sheep flocks.

## Key findings

- Larger flock sizes and extensive management practices were linked to higher udder abnormalities and orphan lamb rates.
- SRLV seroprevalence was 14.1% at the ewe level and 75% at the flock level in sampled farms.

## Abstract

California was the second largest sheep-producing state in the US, with an inventory of 533,000 head of sheep and lambs in 2022. Mastitis is a health and welfare concern for ewes and lambs. Mastitis is one of the top reasons for the removal of ewes from the flock and antibiotic use in ewes. In this study, California sheep producers were surveyed on the management of ewes. Seventy-one surveys were completed. Most respondents had flocks of ≥100 sheep (54%; 38/71). Twenty-three percent (16/70) of the respondents reported having >5% udder abnormalities in a flock per lactation. Further analysis showed two clusters among participating farms. Larger flock sizes, the use of breeding ewes for meat or wool production or contract grazing, and more extensive management practices were associated with >5% udder abnormalities and ≥5% orphan lambs. A subset of the respondents (20) participated in serological testing for small ruminant lentivirus (SRLV) in sheep. A total of 1106 ewes or ewe lambs were sampled. The ewe-level seroprevalence was 14.1% (183/1106), and the flock-level seroprevalence was 75% (15/20) of the sampled farms. Our results describe flock demographics, management practices, and producer-reported udder health abnormalities in California ewes. Larger flock sizes and extensive management practices could be risk factors for udder abnormalities in ewes.

(1) Background: Information is lacking on small ruminant lentivirus (SRLV) status, prevalence, risk factors, and control measures for mastitis in California ewes. The goal of this survey was to outline characteristics of the sheep industry in California related to udder health and mastitis management. (2) Methods: An online survey consisting of 48 questions was completed by respondents between April 2022 and February 2023. Descriptive analysis and chi-squared tests were conducted to evaluate associations between variables. A multiple correspondence analysis (MCA) of general management practices, udder health management, and flock demographics was performed to assess clustering. A subset of respondents (20) participated in SRLV serology testing. (3) Results: Seventy-one completed surveys were submitted. The MCA showed two clusters. Larger flock sizes, the use of breeding ewes for meat or wool production or contract grazing, and extensive management practices were more closely related to >5% udder abnormalities per lactation and ≥5% orphan lambs. The flock-level seroprevalence of SRLV was 75% (15/20), and ewe-level seroprevalence was 14.1% (183/1106). (4) Conclusions: The results of this study highlight areas that need further research, such as exploring differences in mastitis and SRLV incidences among management systems, the efficacy of mastitis treatments, and education on critical timepoints for mastitis diagnosis and control.