Date of Award

8-2018

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Animal Science

Committee Chair

Kara Stewart

Committee Member 1

Theresa Casey

Committee Member 2

Ron Lemenager

Abstract

Genetic selection for larger litters negatively affected the swine industry by reducing piglet birthweights and survival. Moreover, sow colostrum production did not increase with increased litter size. Colostrum is essential for postnatal piglet growth and development because it provides nutrition, energy and bioactive factors. Milk replacers are available to supplement piglets with limited colostrum intake. However, replacer formulas lack bioactive factors in milk, and have plant-based fats substantially different from maternally derived lipids. Suckled and milk replacer-fed gilts show different patterns of uterine gene expression, and colostrum deprivation results in impaired uterine adenogenesis. Many lipids function as bioactive factors, thus we hypothesized that source of fat affects early postpartum uterine gene expression.

There is a need to readily identify gilts in commercial herds with the highest reproductive potential. Early nutritional environment affects long-term fertility in swine, and adequate colostrum consumption is linked to sow longevity. The anterior vagina and uterus arise from the same embryonic tissues, and both continue development postnatal. Thus, it is likely that postnatal nutritional environment may affect vaginal development as it does uterine. In studies of humans, lipid profiles of buccal cheek swabs differed with changes in diet. We hypothesized that the vaginal lipidome differs between gilts with varying postnatal nutritional environment, and in the longer-term, postnatal vaginal swab lipid profiles can identify gilts with high reproductive potential.

The objectives of this project were to: 1) Determine if supplementing milk replacer with animal fat stimulated uterine gene expression and adenogenesis similar to colostrum; and 2) Test the hypothesis that gilts exposed to colostrum versus milk replacer have different vaginal lipid profiles on postnatal day (PND) 2. For these studies, gilts were selected at birth (N = 28) and allocated to one of four treatments: suckled for 48 h (S, n = 8); suckled plus supplemented with fat (SF, n = 5); bottle-fed for 48 h (B, n = 8); or bottle-fed plus supplemented with fat (BF, n = 7). Vaginal swabs and uterine tissue were obtained from gilts following euthanasia on PND2. Q-PCR analysis of RXFP1, ESR1, MMP-9, BCL2, and VEGFA found no treatment effect on PND2 uterine expression levels (P > 0.05). There was no treatment effect on rate of uterine epithelial or stromal cell proliferation. Adenogenesis and uterine composition were similar among all four treatments. Lipids extracted from vaginal swabs were subjected to multiple reaction monitoring (MRM) profiling. The discovery phase of pooled vaginal samples detected 1486 lipid molecules, which, in addition to 450 triacylglycerols (TAGs), were then screened for in individual vaginal samples. Screening yielded 146 molecules that discriminated between bottle-fed and suckled gilts (Method 1) and 198 molecules that discriminated between fat-supplemented and non-supplemented gilts (Method 2). A second screening of individual vaginal samples limited to Method 1 molecules followed by receiver operating characteristic (ROC) curve analysis identified 18 molecules that distinguished vaginal samples from colostrum versus milk replacer fed gilts [area under the curve (AUC) >0.9]. Differentiation of lipid samples from gilts with and without fat supplementation following Method 2 sample screening was less robust (highest AUC score =0.78).

Morphology and expression of selected genes on PND2 were not reliable markers of the effect of early nutritional environment on uterine development. In contrast, vaginal lipid profiles were distinct between gilts fed colostrum versus milk replacer. Moreover, obtaining vaginal swabs is relatively easy and non-invasive, and thus the method warrants further investigation to determine whether early postnatal vaginal lipid profiles are related to long-term fertility.

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