Document Type

Thesis - Open Access

Award Date

2021

Degree Name

Master of Science (MS)

Department

Animal Science

First Advisor

Crystal Levesque

Keywords

Cortisol, Gestation housing. Parturition, Sow welfare. Sows, Stress

Abstract

Cortisol is known as the stress hormone, as it influences many metabolic processes to maintain glucose homeostasis during stressful experiences, including physical and psychological stress. It can be detected in biological matrices such as blood and hair and is released rapidly during sudden stressors and continuously during longterm stress. Blood cortisol fluctuates rapidly in response to acute stressors like pain, exertion, and fear; in hair cortisol accumulates steadily over the period of hair growth and may be useful for detecting chronically elevated cortisol resulting from long-term stress. The objective of this research was to, 1) determine the influence of a simulated chronic stress scenario on hair cortisol concentrations (HCC), 2) determine HCC of sows in two different gestation housing systems as a marker of chronic stress, and 3) examine the pattern of blood cortisol during parturition in the sow. In the US and internationally, gestation stalls have received consumer criticism because of the way they limit sow movement and natural behaviors. However, the data are conflicting as to whether gestation stalls cause poorer welfare than group housing, as injuries and stress may result from mixing unfamiliar sows. In study 1, a total of 18 gilts in 2 groups were used. In group 1, 6 gilts from one pen were split into 3 pens of 2 gilts. In group 2, 12 gilts were mixed from separate group pens into 4 pens of 3 gilts. Mixing occurred on d0. All gilts were assigned to 1 of 2 treatments, ACTH or Control. Treatment gilts were repeatedly administered ACTH (thrice in group 1 and twice in group 2), and Control gilts were administered saline at the same timepoints. Hair was shaved on d0 and on d21 after mixing, hair growth was collected. HCC was not affected by ACTH administration, but mixing unfamiliar gilts in new pens caused a significant increase in HCC. Administration of ACTH may not be adequate for simulating chronic stress in pigs, but HCC is an effective matrix for evaluating in pigs. In study 2, 34 sows were housed in gestation stalls and 32 sows were housed in group pens from breeding until approximately d111 of gestation. Hair samples were collected on d37 and d111, representing early and late gestation, and were analyzed for cortisol. Sows were categorized as parity 0-1, 2-3, or ≥4, and data were analyzed using the PROC MIXED procedure in SAS. Stall-housed sows had higher hair cortisol than group-housed sows, and stall-housed gilts and parity 1 sows had higher HCC than all other females regardless of housing system. Hair cortisol concentrations tended to be higher in late gestation than in early gestation for all females; HCC was not affected by time in gilts, and stall-housed gilts had higher HCC than group-housed gilts. In study 3, the pattern of cortisol secretion during parturition was examined using a total of 9 farrowing periods from 7 primi- and multiparous females. Females had previously been surgically fitted with cephalic vein catheters, and blood samples were collected every 15 min from the birth of the first piglet until the expulsion of the last placental part. Piglet birth times and weights were recorded, and data were analyzed using the PROC CORR function of SAS. Smaller litters were associated with a higher minimum maternal cortisol, which occurs closer to or after the birth of the last piglet. In large litters, maximum cortisol may occur earlier in relation to the birth of the last piglet, and minimum cortisol is more likely to occur at the beginning of parturition. Larger, more robust piglets in smaller litters are associated with higher maternal cortisol at the onset of parturition and promote shorter farrowing duration. Maternal cortisol appears to be strongly influenced by fetal cortisol. However, sow cortisol at the onset of parturition may be reflective of the total litter size and expected total farrowing time. HCC is an effective matrix for identifying elevated cortisol over prolonged periods of stress in pigs and may be used to identify chronic stress in gestating sows. Maternal cortisol at parturition is strongly influenced by fetal cortisol and is not likely to be useful as an indicator of sow welfare during that period.

Number of Pages

132

Publisher

South Dakota State University

Share

COinS