Characterization of Activity Changes in Gilts During Estrus Using the NUtrack Livestock Monitoring System

Authors

• Emily P. Aquino, University of Nebraska-LincolnFollow

First Advisor

Benny Mote

Committee Members

Ty Schmidt, Brett White, Amy Desaulniers

Date of this Version

5-2026

Document Type

Thesis

Citation

A thesis presented to the Faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science

Major: Animal Science

Under the supervision of Professor Benny Mote

Lincoln, Nebraska, May 2026

Comments

Copyright 2026, Emily P. Aquino. Used by permission

Abstract

Early and accurate detection of estrus in replacement gilts is essential for reproductive success and to ensure efficient production. The objective of this study was to evaluate activity changes occurring relative to first estrus of gilts and subsequent cycles. At ~ 110 days of age, 112 gilts were randomly assigned to 14 pens and placed under continuous video monitoring until the end of the trial at ~ 200 days of age. Daily boar exposure (~ 10 minutes per day) began at ~ 122 days of age. During this period, recorded observations included vulva scores (based on swelling and redness), mounting of pen-mates, vocalization, and erect ears. A gilt was determined in estrus if the standing reflex was exhibited in response to the back pressure test (BPT). Video was processed using the NUtrack system to quantify daily activities, including distance traveled (m), angles rotated (radians), time spent standing (s), eating (s), sitting (s), lying lateral (s) and lying sternal (s). Data were analyzed through paired comparisons (PROC TTEST) and repeated measures mixed models (PROC MIXED) (SAS version 9.4). Significant increases in activity during estrus compared to a 7-day average were found for distance traveled (p < 0.0001), angles rotated (p < 0.0001), and time standing (p < 0.0004) for both Cycle 1 and 2. Similarly, decreases in activity during estrus were observed in time eating (p < 0.0001) and total lying time (p < 0.003) in Cycle 1 and 2. The anchored event analysis by phase and day indicated most active traits declined prior to estrus with a peak during estrus, whereas eating and passive traits were decreased during estrus. These changes were more pronounced during Cycle 2 than Cycle 1. Timing of change in most activities occurred between -4 to -2 days prior to estrus (p < 0.05). This analysis suggests that gilt activity is altered throughout the estrous cycle and these changes can be quantified by the NUtrack system. Using the indicator activity traits found in this study, the automation of estrous detection would be paramount for the swine industry.