Piglets are highly vulnerable to infections, but colostrum provides them with some protection. The function of colostrum components is unknown, as is if the amount and subsets of leukocytes in colostrum differ between gilts and sows. This study serially characterized leukocyte populations in colostrum for differential leukocyte counts. Differences in humoral and cellular composition of colostrum between 40 gilts and 40 sows (parities orders 3–4) from a commercial herd were examined. Flow cytometry is a useful tool to identify and quantify leukocyte subsets in sow colostrum. Overall, there were no (p ≥ 0.05) parity differences in total macrophages, granulocytes, and T and B cells. However, the sows’ colostrum presented significantly higher (p ≤ 0.05) T lymphocyte subsets than gilts, such as central memory CD4+T cells, effector memory CD4+T cells, and central memory CD8+T cells. Among B-lymphocytes, percentages of SWC7+CD5+ cells were significantly higher in sow colostrum than in that of gilts. As expected, IgG concentrations were significantly higher in sows than in gilts. Colostrum from sows had significantly greater mitogenic activity than colostrum from gilts and this fact can be associated with the potential to accelerate the maturation of a newborn’s gastrointestinal tract. Our findings suggest that parity order may be one among other factors influencing the cell population and, consequently, the immune adaptive response in piglets that induces neutralizing antibodies and cellular immune responses to antigens.

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Gilts represent a group risk for Mycoplasma hyopneumoniae vertical transmission in swine herds. Therefore, parity segregation can be an alternative to control M. hyopneumoniae infections. The study evaluated the effect of parity segregation on M. hyopneumoniae infection dynamics and occurrence and severity of lung lesions at slaughter. For that, three multiple site herds were included in the study. Herd A consisted of the farm where gilts would have their first farrowing (parity order (PO) 1). After the first farrowing PO 1 sows were transferred to herd B (PO2-6). Herd C was a conventional herd with gilt replacement (PO1-6). Piglets born in each herd were raised in separated nursery and finishing units. Sows (n = 33 (A), 37 (B), 34 (C)) in all herds were sampled prior to farrowing and piglets (n = 54 (A), 71 (B), 66 (C)) were sampled longitudinally at 21, 63, 100, 140 days of age and at slaughter for M. hyopneumoniae detection by PCR and lung lesions scoring. M. hyopneumoniae prevalence in sows did not differ among herds. Prevalence of positive piglets was higher at weaning in the PO1 herd (A) (P < 0.05). However, prevalence of positive pigs from 100 days of age to slaughter age was higher in the PO2-6 herd (B) (P < 0.05). Lung lesion occurrence and severity were higher in herd B. The authors suggested that the lack of a proper gilt acclimation might have influenced the results, leading to sows being detected positive at farrowing, regardless of the parity.

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