November 2020

Reproductive tract scoring methods as a tool for identify gilts with improved productivity as breeding herd females.

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 weeks 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)]. Vulva Score Method A (VSA) used a 3-score strategy designed using previous data (Graves et al., 2019) where gilts were stratified into the following categories; Small (S; VW < 27 mm), Medium (M; VW 27 to 34 mm), and Large (L; VW > 34 mm). Vulva Score Method B (VSB) used a similar tool to categorize gilts into 5 groups based on VW: 1 (VW < 27 mm), 2 (VW 27 to 29 mm), 3 (VW 29 to 31 mm), 4 (VW 31 to 33 mm), and 5 (VW > 33 mm). The design of the tool used for VSA and VSB was a laminated card with precisely sized series of sections removed to accurately assign a vulva score based on the described dimensions. Farm Score (FS) was a visual, subjective assessment of vulva size (conducted visually by trained farm staff) which stratified gilts into 3 categories (1, 2, or 3), where score 1 intended to identify gilts whose vulva size represented the bottom 15%, a score 2 was considered intermediate and represented the middle 70%, and a score 3 was intended to represent the 15% of gilts with the largest vulvas. The FS was conducted independently of all other vulva score measurements to avoid bias in the subjective score.

At 15 weeks 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; R2 = 0.05). All 3 scoring methods were effective in categorizing gilts based upon VW, as the measured VW size within methods differed by score. The proportion of gilts achieving their first parity increased with score for VSA (64.7%, 73.2%, and 84.4%), VSB (66.0%, 71.7%, 79.2%, 76.4%, and 84.2%), and FS (67.2%, 75.0%, and 88.8%), but VSA, VSB, and FS did not influence percentage of gilts achieving their second parity. 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) as well as born alive (21.13 vs. 23.05 pigs). Results were similar for VSB, where scores 2 to 5 had greater total born (23.97 vs. 26.33 pigs) and born alive (21.11 vs. 23.02 pigs) through 2 parities compared to gilts scored 1. Using the FS method, total born pigs tended to be increased 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 weeks of age may identify sows with improved productivity through 2 parities as breeding herd females.

Romoser MR, Hale BJ, Seibert JT, Gall T, Rademacher CJ, Stalder KJ, Baumgard LH, Keating AF, Ross JW.
Methods for reproductive tract scoring as a tool for improving sow productivity.
Translational Animal Science. 2020; 4(1): 275–284.