Accuracy and Repeatability of Sow Body Condition Scoring1, The

Professional Animal Scientist, Aug 2009 by Fitzgerald, R F, Stalder, K J, Dixon, P M, Johnson, A K, Karriker, L A, Jones, G F

ABSTRACT

The objective of this study was to estimate observer accuracy and repeatability of body condition scoring of sows when scorers had different levels of prior experience. Participants (n = 17) for this study were identified as having no (n = 7), some (n = 4), and extensive (n = 4) prior experience evaluating conformation or body condition in livestock species or having served as instructors (TR; n = 2) during the training sessions. Twenty-five of a total 150 sows were used in the participant training session, and the remaining sows (n = 125) were used during the independent scoring process. Sows used in the scoring process were objectively categorized into BCS on a 5- and 9-point scale (BCS^sub 5^ and BCS^sub 9^, respectively) using last-rib backfat estimates. Participant BCS^sub 5^ and BCS^sub 9^ deviation evaluations from last-rib backfat estimates revealed a tendency to overestimate BCS in some sows and underestimate BCS in others. Repeatability, a measure of variance attributed to individual participants between rounds of scoring, was the largest contributor (70.6%) to the total test variability. Reproducibility, a measure of variance attributed to BCS^sub 9^ assigned by multiple participants, accounted for only 29.4% of the total test variation. Much more opportunity exists to reduce repeatability variance as compared with variance associated with participant bias. Standard errors of the difference were lower on the BCS^sub 9^ scale, and participants were within scores of 0.50 between their first- and second-round values. Participants were consistently within 0.65 scores of BCS assigned by backfat measurements. Averaged across all participants, the ultrasonic trait of last-rib backfat yielded the greatest correlation (0.58) with BCS^sub 9^, followed by 10th-rib backfat (0.51), 10th-rib loin eye area (0.47), and last-rib loin eye area (0.43). Similar trends were observed for the BCS^sub 5^ scale. Therefore, practice assigning independent BCS should lower repeatability variance, but training to calibrate specific participants may influence total test variance only to a relatively small degree.

Key words: body condition score, reproducibility, standard error of prediction, sow

INTRODUCTION

Sows can enter a negative energy balance during lactation when fat and muscle body reserves are mobilized to support production of milk for piglet growth. After weaning, a limited number of days are available during gestation to replenish the depleted energy stores of the sows. In modern pork production systems, sow nonproductive days is a key indicator of inefficiency, and thus are minimized. Because nonproductive days are minimized, Dourmad et al. (1996) suggests that the gestation period is the only period in current production systems when body energy can be replenished. Additionally, they reported that modern sows require 8,500 kcal DE/d during gestation, approximately 1.3 times the maintenance requirement, to replenish body reserves.

Sows that have not attained a mature size have nutrient requirements to support growth, and these requirements must be met through rations provided during lactation and gestation. One possible way to improve reproductive performance after lactation is to reduce the amount of BW lost during lactation. Thus, it is important for swine producers to have the skills necessary for accurate and repeatable quantifying of BCS so that feed rations can be adjusted accordingly. For a more detailed review of the application of body condition scoring systems, see Burkholder (2000).

Young et al. (2001) suggested that BCS differ between producers and technicians, and based on results by Thomsen et al. (2008), who evaluated lameness scoring, BCS differ within producers' or technicians' own scores. As it relates to commercial sow production, employees may verbally express their ability to evaluate body condition to their employer, but in reality, this discrepancy may yield larger variations in sow body condition in the herd. Thus, the objective of this study was to estimate the accuracy and repeatability of body condition scoring by participants with different levels of experience.

MATERIALS AND METHODS

The protocol and use of these animals was reviewed and approved by the Iowa State University Animal Use and Care Committee and Institutional Review Board for human subjects.

Animal Description

Crossbred sows (Yorkshire � Landrace, n = 150) of parities 1 to 6 were housed in standard gestation stalls (0.75 � 2.15 m). With a cloth tape measure, heart girth and flank-to-flank measurements were obtained following the procedures described by Iwasawa et al. (2004). Sow BW were calculated using the lactation sow BW equation listed in Sulabo et al. (2007), and ranged from 163 to 299 kg. Backfat and loin eye area were estimated ultrasonically (Aloka 500, Corometrics Medical Systems, Wallingford, CT) at the 10th and last rib by a National Swine Improvement Federation-certified real-time ultrasound technician (Bates and Christian, 1994).