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Wegner, M., Nordell, N., Shelton J., & Desaulniers, A. 2024. Effects of Maternal Milk Consumption on Reproductive Development of Neonatal Boar. Undergraduate Honors Thesis. University of Nebraska-Lincoln.


Copyright Maddie Wegner, Nicole Nordell, Jackie Shelton, and Amy Desaulniers 2024.



Effects of Maternal Milk Consumption on Reproductive Development of Neonatal Boars

Maddie N. Wegner, Nicole E. Nordell, J. Shelton, and Amy T. Desaulniers

The pork industry generated $57 billion in 2021, yet the reproductive efficiency of swine can still be improved. To improve the productivity and profitability of the swine industry, enhancing the reproductive development of the boar is critical because one boar can sire 8,398 progeny per year. Previous studies have shown that maternal colostrum and milk can enhance testicular development/function of pigs. Both colostrum and milk contain numerous bioactive factors, and nursing enhances Sertoli cell proliferation. Sertoli cell counts determine testicular size and the capacity for sperm production, thus more Sertoli cells promote greater fertility because of their critical role in driving spermatogenesis. In the present pilot study, we hypothesize that feeding neonatal boars a diet of sow milk (versus milk replacer) would enhance testicular growth and/or composition, as well as testicular hormone production (e.g., estrogens). White crossbred boars from 2 litters nursed colostrum ad libitum from their dam for 2 d after birth. On post-natal day 2, littermates were distributed to treatment based on body weight and immunocrit status (indicator of colostrum consumption). Then, boars were pan fed either 90 mL of sow milk (n = 4) or milk replacer (n = 4) three times daily for 8 days. On d 10, boars were euthanized and samples (blood and testis) were collected. The tissues were fixed, embedded, then sectioned for further histological analysis. Histological analysis was performed to determine interstitial area, seminiferous tubule area, and Leydig cell area. Immunofluorescence was performed to determine Sertoli, germ, and Leydig cell counts per image. Serum was analyzed for blood chemistry and steroid hormones. Data were analyzed via the GLIMMIX procedure of the Statistical Analysis System (SAS) with a model that included boar as the experimental unit, treatment as the fixed effect, and dam as a random effect. Milk-fed boars had heavier testes (P = 0.031) compared with replacer-fed males, despite no difference in body weight (P > 0.05). Neither cell counts (germ, Leydig, Sertoli) per field nor Leydig cell area differed between treatment groups (P > 0.05). Interstitial area and tubular area tended to be affected by treatment (P < 0.10). Glucocorticoid levels (e.g., cortisol) did not differ between treatment groups (P > 0.05). In boars fed sow milk, serum sodium concentrations were reduced (P = 0.0280) as well as blood urea nitrogen (BUN; P = 0.0046), and chloride (P = 0.0467). In contrast, milk-fed boars had greater serum concentrations of cholesterol (P = 0.0009) and thyroxine (P = 0.0339). The number of Sertoli cells per image was not different between groups but larger testes in milk-fed boars indicates more total Sertoli cells due to more testicular tissue, suggesting that these animals would have an increased sperm production capacity post-puberty. Another important finding was elevated thyroxine concentrations in serum of milk-fed boars. Interestingly, thyroxine inhibits Sertoli cell apoptosis in cattle thereby providing a possible mechanism for the larger testes observed in milk-fed animals. Ultimately, these data suggest that maternal milk consumption enhances reproductive development in the neonatal boar, which could be harnessed to promote greater reproductive efficiency and productivity in the swine industry.

Keywords: Lactocrine programming, boar, reproductive development, testis, maternal milk consumption