Role of Dietary Interventions in Reducing the Negative Impact of Stressful Events in the Pig

Candace Young, Purdue University

Abstract

Two experiments were conducted using pigs at different life stages to determine the effects of dietary tryptophan and water delivered oregano essential oil on growth performance, rectal temperature, water use, intestinal integrity and gene expression of biomarkers in the face heat or transport stress. In the first experiment, 192 grow-finish pigs were used to investigate the effects of water supplementation of oregano essential oil (OEO) on growth performance, water intake, rectal temperature, intestinal integrity, and expression of genetic biomarkers during an acute heat challenge. Pigs were randomly allotted to 2 X 2 factorial arrangement of treatments with pigs being heat stressed or not and being supplemented with OEO or not with 8 replicate pens of each treatment with 6 pigs/pen (4 barrows, 2 gilts per pen). Water treatments were administered immediately, with dosing at 47 μL/L of OEO. One-half of the pigs on each water treatment remained under thermoneutral conditions (TN; 21.1C), while the other half was subjected to a 3 d diurnal, acute heat stress (HS) with 12 hours at 33.3 oC (7AM-7PM) and 12 hours at 26.7 oC (7PM7AM). Three days post-HS, temperatures were reduced back to TN for the rest of the study, and pigs remained on their water treatments. Rectal temperatures were collected in the morning and evening of the heat stress period on one barrow and one gilt in each pen. Jejunal tissue was collected for subsequent histological examination and determination of gene expression. All data were analyzed using the GLM procedure of SAS (ver. 9.4). Pigs subjected to heat stress had reduced ADG (P < 0.003) and G:F (P < 0.008) during the 3d heat stress compared to pigs reared under thermoneutral conditions. However, post-heat stress, heat stressed pigs had compensatory gain resulting in increased ADG (P < 0.001) and G:F (P < 0.001) compared to thermoneutral reared pigs. Overall, there was an interaction (P < 0.006) observed between water and heat treatment with OEO increasing ADG in thermoneutral pigs but not in heat stressed pigs. Similarly, interactions between water and heat treatment were observed for ADFI during heat stress (P < 0.004), post heat stress (P < 0.01), and overall (P < 0.004) from increasing OEO intake in thermoneutral pigs but not in heat stressed pigs. Rectal temperatures were higher (P < 0.001) for heat stressed pigs at the end of d 1 and 2 of the acute heat challenge compared to TN housed pigs. Pigs exposed to HS also used more water than pigs housed in a thermoneutral environment (P < 0.002). There were no differences between villi height, crypt depth or VH:CD between treatment groups (P >0.05). There was also no difference in TP53 and CDKNA1 gene expression among treatments (P > 0.10). In the second experiment, 36 barrows were used in an 18 d experiment to investigate the effects of pre-weaning tryptophan supplementation on performance and intestinal integrity following weaning with or without transport stress at weaning. Pigs were randomly allotted to 2 X 2 factorial arrangement of treatments of pre-weaning tryptophan supplementation or not and weaning transport or not. Pigs on the tryptophan treatment received 0.35, 0.45, and 0.55 g Trp/d in 5 day intervals, beginning 15 d prior to weaning. Tryptophan was dissolved in chocolate milk and administered by oral gavage with control pigs receiving milk only. At weaning, 4 pigs from each pre-weaning treatment were euthanized for collection of jejunal tissue. Of the remaining pigs, half the pigs on each treatment were transported for 12 h, and half were moved into individual pens with no transport. Following transport, all pigs were individually housed and provided ad libitum access to water and feed from a common diet. On d 3 post-weaning, all pigs were euthanized for collection of jejunal tissue. Jejunal tissue was used for histological examination and for determination of gene expression. All data were analyzed using the GLM procedure of SAS (9.4). No effects of Trp supplementation were observed on pre-weaning (P > 0.10) growth. Pig BW and ADFI were unaffected (P > 0.10) by Trp supplementation and transport at weaning. Postweaning, there was a tendency (P < 0.06) for an effect of transport on ADG as transported pigs lost weight in the 3 d post-weaning period while non-transported pigs gained slightly. Gain:Feed post-weaning was lower (P < 0.04) for transported pigs compared to non-transported pigs. No differences were observed for villus base and mid width, villus height, crypt depth or villus height:crypt depth. There was a tendency for an interaction of transportation and Trp supplementation (P < 0.06) on villi base width driven by an increased villus width in nontransported pigs given supplemental Trp but a decrease in villus width in transported pigs given supplemental Trp. These results conclude that these alleviating agents had minimal effects when pigs were stressed, however TN grow-finish pigs benefitted from OEO water supplementation among growth performance.

Degree

M.Sc.

Advisors

Radcliffe, Purdue University.

Subject Area

Animal sciences

COinS