Short communicationThe use of proliferating cell nuclear antigen (PCNA) immuno-staining technique to determine number and type of follicles in the gilt ovary

The present study determined the number and type of follicles in gilts ovarian tissue using the proliferating cell nuclear antigen (PCNA) immunohistochemical labelling technique and investigated the association between the number of follicles, gilt age, body weight, average daily gain, age at first observed oestrus, ovulation rate and weight of the ovaries. Ovarian tissues were obtained from 19 gilts aged 267.8±19.2 days weighting 145.7±11.8 kg. The tissues were incubated with mouse monoclonal anti-PCNA. The follicles were categorized as primordial, primary and growing follicles. PCNA immuno-staining enhanced the visualization of small follicles and the efficacy to distinguish primordial and primary follicles. The gilt ovarian tissue contained 19.8±8.5 follicles/100 μm2 (range 6.0-42.0). The numbers (and proportions) of primordial, primary and growing follicles per 100 μm2 of the gilt ovarian tissue were 13.1±6.9 (64.2%), 6.2±3.3 (32.7%) and 0.5±0.2 (3.1%) follicles, respectively. The number of primary follicles per 100 μm2 of the gilt ovarian tissue positively correlated to body weight (r=0.50, P=0.032) but negatively correlated to age at first observed oestrus (r=−0.54, P=0.015). In conclusion, PCNA technique can be applied to quantify the precise number and distinguish the type of follicles in the ovarian tissue of porcine species. Gilts with a higher body weight and earlier age at first observed oestrus have a higher density of primary follicles in the ovarian tissue than those with a lower body weight and later age at first observed oestrus.