DOI: 10.5061/dryad.msbcc2g8s
title: Using a real-time location system to detect behavioral changes in ewes with subclinical mastitis and their lambs

description: Subclinical mastitis, the asymptomatic inflammation of the udder, is an
 important economic and animal welfare concern in meat-producing flocks,
 causing reduced milk yield and poorer lamb growth and survival. Cases
 often remain undetected until more severe stages, highlighting the need to
 investigate early detection methods, such as automated behavioral
 monitoring. Our objective was to use a real-time location system to
 determine whether subclinical mastitis affected ewe and lamb movement
 patterns. From 2−6 weeks postpartum, we collected duplicate milk samples
 weekly from each udder half of 24 ewes (15 Polypay, 3 Hampshire, and 6
 Targhee) for bacterial speciation. Ewes were considered infected in a
 given week if milk samples from at least one udder half contained ≥ 100
 CFU/mL at both the start of that week and the following week's
 sampling. Each ewe and her lamb(s) wore neck-mounted sensors that recorded
 x, y coordinates every 0.1 s via ultrawideband technology while housed in
 a group pen. We used linear mixed models to assess the effects of the
 ewe’s weekly infection status (healthy vs. infected) and weeks since
 lambing (2−6) on four behavioral outcomes: ewe-lamb distance, ewe-feed
 bunk distance, ewe distance traveled, and lamb distance traveled. The
 number of lambs reared (single vs. multiple) was included as a covariate
 and dam ID was specified as a random effect. Lambs traveled more during
 weeks when their dam was infected, possibly reflecting increased hunger
 due to insufficient maternal milk supply. No significant effects of
 infection status were observed for the other behavioral outcomes. Ewe-lamb
 and ewe-feed bunk distances were shortest, and lamb movement was greatest,
 in week 2 compared to later weeks patterns that likely reflect the lamb’s
 greater nutritional dependence on the dam and increased play behavior
 early in life. Our findings provide preliminary evidence that real-time
 tracking of lamb behavior may help identify early cases of subclinical
 mastitis in the dam. They also highlight the potential welfare impacts of
 subclinical mastitis on lambs, underscoring the importance of early
 detection and management.
description: # Supplementary Materials — *Using a real-time location system to detect
 behavioral changes in ewes with subclinical mastitis and their lambs* This
 repository contains the data and R script used to conduct the descriptive
 and statistical analyses and create the figures referenced in the paper of
 the same name. --- ## 📄 Study Overview Our study examined whether a
 real-time location system could be used to detect behavioral changes
 associated with naturally occurring subclinical mastitis in ewes and their
 lambs. Specifically, we used a real-time location system to quantify: 1.
 the daily average distance between each ewe and her lamb(s) 2. the ewe’s
 distance from the feed bunks 3. the daily distance traveled by the ewe 4.
 the daily distance traveled by her lamb(s) **Methods:** We collected
 duplicate milk samples weekly from each udder half of 24 ewes (15 Polypay,
 3 Hampshire, and 6 Targhee) for bacterial speciation for weeks 2 through 6
 of lactation. Ewes were considered infected in a given week if milk
 samples from at least one udder half contained ≥ 100 CFU/mL at both the
 start of that week and the following week's sampling. Each ewe and
 her lamb(s) wore neck-mounted sensors that recorded x, y coordinates every
 0.1 seconds via ultrawideband technology while housed in a group pen. ---
 ## 📁 Files and Descriptions ###
 `Peckler&Adcock_AABS_Mastitis_RTLS_analysis_250623.nb.html` *
 **Description:** R script to examine whether a real-time location system
 could be used to detect behavioral changes associated with naturally
 occurring subclinical mastitis in ewes and their lambs * **Input:**
 `Peckler&Adcock_AABS_Mastitis_RTLS_data_250623.xlsx` * **Output:**
 Figures 3-7 * **Use:** Open in any web browser or in RStudio (*File → Open
 File*) --- ### `Peckler&Adcock_AABS_Mastitis_RTLS_data_250623.xlsx` *
 **Description:** Excel file containing the data collected from each udder
 half of 24 ewes weekly from weeks 2 through 6 of lactation and of
 summarized daily positional data for the metrics: mean daily distance
 traveled by ewes and lambs, mean weekly distance between ewes and their
 lambs, and mean weekly distance between ewes and feedbunks. The second
 sheet contains descriptions of each column variable. Blank cells indicate
 NA values. | Variable | Description | |
 ----------------------------------- |
 ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `AnimalID` | Unique identification number for each animal (n = 59) | | `AnimalType` | Indicates whether the animal is a ewe (the dam) or a lamb | | `DamID` | Unique identification number for each dam (n = 24). For animals classified as "Ewe" in the AnimalType column, AnimalID and DamID are identical. | | `DamDOB` | Date of birth of the ewe/dam. For animals classified as "Ewe" in the AnimalType column, this is the ewe's own date of birth; for lambs, it is the date of birth of their dam. | | `Breed` | Breed of the animal (Targhee, Polypay, or Hampshire) | | `Parity` | The ewe/dam's total number of lactations, including the current one. Ranges from 1 to 8. | | `ParityGroup` | Parity categorized into first, second, third, or greater than third | | `LambingDate` | Date the ewe gave birth | | `LambsBorn` | The number of lambs the ewe delivered | | `LambsReared` | The number of lambs the ewe reared | | `MultipleLambs` | Binary variable indicating whether the ewe reared a single lamb (0) or multiple lambs (1) | | `Pen` | Pen in which the animal was housed during the study (Pen 1 or Pen 2) | | `TrackingDate` | Date on which animal tracking data were collected | | `Weekday` | Day of the week on which data were collected | | `PenSampled` | Binary variable indicating whether the ewe or her penmates were sampled on that day (1) or none were sampled (0) | | `WeeksSinceLambing` | Number of weeks since lambing when the data were collected. Ranges from 2 to 6 weeks. | | `TotalDailyDistanceTraveled_m` | Total distance (in meters) traveled by the animal on the tracking date | | `MeanDailyDistanceToDam_m` | Mean daily distance (in meters) between each lamb and its dam on the tracking date. For ewes, this value is 0. | | `MeanDailyDistanceToFeedbunk1_m` | Mean daily distance to feedbunk 1 (in meters) on the tracking date | | `MeanDailyDistanceToFeedbunk2_m` | Mean daily distance to feedbunk 2 (in meters) on the tracking date | | `MeanDailyDistanceToFeedbunks_m` | Average of the mean daily distance to feedbunks 1 and 2 | | `PercentageDataRecordedByTagPerDay` | Percentage of the tracking date's data points that were contributed by the sensor out of the total data points for that day | | `Diagnosis_UdderHalf_L` | Diagnosis of the left udder half based on bacterial culture | | `Diagnosis_UdderHalf_R` | Diagnosis of the right udder half based on bacterial culture | | `PositiveEwe` | Binary variable: 1 = at least one udder half was infected; 0 = both halves were uninfected at the beginning of that week. | | `WeeklyDiagnosis` | Text field summarizing each ewe’s diagnostic status (PositiveEwe) at both the beginning and end of each sampling week. | --- ## 🧪 Requirements * [R](https://www.r-project.org/) * [RStudio](https://posit.co/downloads/) * Basic familiarity with R Markdown or `.nb.html` output files. ---