Improving sow lifetime productivity is essential for maximizing farm profitability. Study objectives were to determine the accuracy for different vulva scoring methods in a commercial production system and to assess whether gilt reproductive tract scoring [evaluated by vulva width (VW)] prior to puberty could serve as useful gilt selection criteria. To accomplish this objective, 958 prepubertal replacement gilts in a commercial system were evaluated at approximately 15 wk of age. Gilt body weight (BW) was recorded in addition to 4 different methods to evaluate VW. Methods for VW assessment included digital caliper measurement (mm), visual evaluation and scoring by trained farm personnel [Farm Score (FS)], and 2 methods using scoring tools [Vulva Score Method A and B (VSA and VSB, respectively)] specifically calibrated from the VW distribution measured on gilts from previous studies. The VSA and FS methods assigned gilts to one of 3 categories (S, M, L, and 1, 2, 3, respectively) whereas VSB classified gilts vulvas using a 5-point scoring system (1 to 5). At 15 wk of age, a low proportion of variability in vulva size (27.8 ± 0.1 mm) could be explained by BW (62.2 ± 0.2 kg; R 2 = 0.05). All 3 scoring methods were effective in categorizing gilts based upon VW, as the measured VW size within methods differed by score (P < 0.01). The proportion of gilts achieving their first parity increased with score for VSA (64.7%, 73.2%, and 84.4%; P = 0.02), VSB (66.0%, 71.7%, 79.2%, 76.4%, and 84.2%; P = 0.02), and FS (67.2%, 75.0%, and 88.8%; P = 0.03), but VSA, VSB, and FS did not influence percentage of gilts achieving their second parity (P = 0.32, 0.29, and 0.30, respectively). Litter performance of gilts scored as M or L using VSA improved with an increased total born over 2 parities compared to those scored as S (23.96 vs. 26.38 pigs; P < 0.01) as well as born alive (21.13 vs. 23.05 pigs; P < 0.05). Results were similar for VSB, where scores 2 to 5 had greater total born (23.97 vs. 26.33 pigs; P < 0.01) and born alive (21.11 vs. 23.02 pigs; P < 0.05) through 2 parities compared to gilts scored 1. Using the FS method, total born pigs tended to be increased (P = 0.06) through 2 parities for gilts having a 2 or 3 vulva score compared to those scored as a 1. Collectively, assessing VW at approximately 15 wk of age may identify sows with improved productivity through 2 parities as breeding herd females.
Keywords: gilt; litter size; sow lifetime productivity; vulva width.
© The Author(s) 2019. Published by Oxford University Press on behalf of the American Society of Animal Science.