Document Type

Dissertation - Open Access

Award Date


Degree Name

Doctor of Philosophy (PhD)

Department / School

Animal Science

First Advisor

Joe Cassady


grow-finish, heat stress, pigs, temperature humidity index


The objectives of this study were: one, use electronic monitoring to determine feeding behavior patterns of grow-finish pigs throughout the year and to identify changes that occurred during heat stress events, and second, identify genetic markers associated with changes in feeding behavior due to heat stress. Pigs were placed in a grow-finish barn at approximately eight to ten weeks of age in 6 pens of 40 animals and monitored for 4-months. Gilts and barrows were from three different sire breeds, Duroc, Landrace, and Yorkshire. Each pen had one feeder, designed to feed 5 animals at a time. Feeders were fitted with an antenna and a multiplexer. Data were collected from antennas every 20 seconds. Outside temperature and humidity were obtained from a National Weather Station and used to calculate temperature humidity index (THI). Days in the study were partitioned into groups based on their maximum temperature humidity index (THI), where a THI less than 23.33°C was classified as “Normal”, a THI between 23.33°C and 26.11°C was classified as “Alert”, a THI between 26.11°C and 28.88°C was classified as “Danger”, and a THI greater than 28.88°C was classified as “Emergency”. Feeding behavioral differences among breeds and sex were observed across all THI categories. Landrace-sired pigs had fewer feeder visits compared to Duroc- and Yorkshire-sired pigs. Gilts had fewer feeder visits than barrows in all THI categories. A genome-wide association study for an animal’s change in feeding behavior between different THI categories was also conducted. Heritabilities for the difference in a pig’s feeder visits between each of the THI categories were low to moderate (0.136 to 0.406). Greater than 71% of genetic variation was explained by regions within eight chromosomes in the comparison between Danger and Emergency THI. Biological processes related to sensory perception and detection of chemical stimuli were over-represented in the set of genes located in these regions. Differences in feeding behavior patterns between THI categories demonstrate that heat stress affects sire breeds and sexes differently. Also genetic markers identified in this study may facilitate genetic selection for improved grow-finish performance during elevated ambient temperatures.

Library of Congress Subject Headings

Swine -- Effect of temperature on.
Swine -- Feeding and feeds.
Swine -- Genetics.
Swine -- Effect of stress on.
Heat -- Physiological effect.


Includes bibliographical references (pages 93-114)



Number of Pages



South Dakota State University



Rights Statement

In Copyright