290 Vitamin A and Beta-Carotene Supplementation on Growth Performance, Immune System, and Mammary Gland Development in Finishing Pigs

Abstract

Abstract A total of 224 finishing pigs were randomly assigned to split-sex pens (n = 4 pigs per pen). Each pen was assigned to one of four diets: control (7,656 IU vitamin A/kg), control diet supplemented with vitamin A (4.36 ppm; Rovimix A 1000, DSM, NJ, US), control diet supplemented with beta-carotene (163.28 ppm; Rovimix β-Carotene 10%, DSM, NJ, US), or control supplemented with oxidized beta-carotene (40 ppm; 10% active ingredient, Avivagen, Ottawa, ON, Canada). Pigs and feeder weights were recorded at the start of the study (d 0) and end of each phase (days 21, 42, and 63). A subset of gilts was randomly selected and a blood sample for vitamin A (retinol) analysis was collected on days 0, 18, 39, 60, and 63. The same gilts were vaccinated against Lawsonia intracellularis and porcine circovirus. Antibodies against each vaccination were measured on days 18, 39, and 60. At the end of the study, the subset of gilts was euthanized to obtain a liver sample for vitamin A (retinyl palmitate is converted to retinol for measurement) analysis and a jejunum sample to measure the mRNA abundance of genes involved in vitamin A metabolism (alcohol dehydrogenase class 1, lecithin retinol acyltransferase phosphatidylcholine-retinol O-acyltransferase, retinol binding protein, and beta-carotene oxygenase 1). Mammary tissue from the second and fourth right anterior mammary glands were collected to assess gland development via immunohistochemical staining for T cells, B cells, and macrophages (CD3, CD20, and IBA1, respectively) and DNA extraction. Vaccine antibodies measures, vitamin A analysis, and mammary immunohistochemical staining was completed at Iowa State University Veterinarian Diagnostic Laboratory (Ames, IA). Data were analyzed in SAS 9.4 (Statistical Analysis System, Cary, NC) via GLIMMIX procedure. Pen was the experimental unit and fixed effects were diet and time. Gilts were nested within pen when appropriate to account for more than one gilt per pen. Oxidized beta-carotene supplementation increased (P = 0.02) average daily gain across phases; however, there were no differences (P = 0.18) in the body weight of pigs. There was no effect (P > 0.05) of diet on plasma or hepatic retinol, IgG or IgM concentrations, immune cell presence, or DNA in mammary tissue. Supplemented vitamin A tended (P = 0.05) to increase the expression of retinol binding protein in the jejunum, but other genes were not affected (P > 0.05) by dietary treatments. A diet by time interaction (P = 0.04) was noted for circovirus sample-to-positive ratios and titer levels, where vitamin A supplementation had better vaccine responses at the end of the study. Thus, pigs supplemented with oxidized beta-carotene had an improved average daily gain over vitamin A supplemented pigs, but pigs supplemented with vitamin A appeared to have a more robust immune system.