Abstract
This study was conducted to estimate the genetic parameters of different feeding pattern traits, including average daily feed intake (ADFI), average occupation time per day (AOTD), average occupation time per visit (AOTV), average daily feeding rate (ADFR), average feeding rate per feeding visit (AFRV), average feed intake per feeding visit (AFIV), and average number of visits per day (ANVD), and their genetic relationship to production traits, such as on-test average daily gain (ADG), backfat thickness (BFT), loin muscle area (LMA), lean percentage (LP), and feed efficiency traits, such as feed conversion ratio (FCR) and five measures of residual feed intake (RFI1 to RFI5), in Duroc pigs (DD). The non-heritable common spatial pen effect was also estimated in all studied traits. The feeding pattern traits used in this study were derived from filtered feeding visits of 602 DD pigs. Using three animal models and the REML method, the genetic parameters revealed low to moderate heritability for ADFI (0.19 to 0.32) and AFIV (0.18 to 0.33), moderate heritability for ANVD (0.28 to 0.35) and AOTV (0.21 to 0.31), and high heritability for AOTD (0.73), ADFR (0.62 to 0.64), and AFRV (0.59 to 0.63). The addition of a common spatial pen effect in models 2 and 3 had a substantial impact, ranging from 8% to 23%, on the total variability of most feeding pattern traits, with the exception of AOTD, which only had a percentage variance of 0.30% due to the pen effect. The genetic and phenotypic correlation revealed that ADFI had consistent moderate to high genetic and phenotypic correlation with production and feed efficiency (FE) traits. However, selection against ADFI would negatively affect on-test ADG. Interestingly, the AOTD had no genetic correlation with ADG (0.04), low to moderate positive genetic correlation with FCR (0.27) and all RFI measures (0.24 to 0.33), and moderate negative correlation with LP (−0.39), indicating that selection for DD pigs with lower AOTD would not influence on-test ADG but may increase LP and improve feed efficiency by lowering FCR and all RFI measures. However, the corresponding phenotypic correlation of AOTD with production and feed efficiency traits was mostly weak, which can be attributed to the low residual or environmental correlation between these correlated traits. At the genetic level, the feeding pattern traits showed potential in improving feed efficiency and production traits. However, further studies are needed to evaluate their impact at phenotypic level.
Highlights
In early feeding behavior studies, the feed intake of pigs was only able to be measured by housing the animals individually, with the result that the pigs ate more, grew faster, and became fatter than pigs housed in groups [1]
Using the electronic feeders manufactured by the same manufacturer (ACEMA 64), Do et al (2013) [6] reported that DD boars with body weight ranging from 30 to 100 kg had comparable mean values for daily feed intake (DFI), time per day (TPD), time per visit (TPV), feed intake rate (FR), number of visits to feeder per day (NVD), and feed intake per visit (FPV) of 2.40 kg/day, 81.05 min/day, 8.58 min/visit, 30.61 g/min, 11.07 visits/day, and 250 g/visit, respectively
The addition of the common spatial pen effect had a substantial impact on the phenotypic variability of most feeding pattern traits in DD pigs
Summary
In early feeding behavior studies, the feed intake of pigs was only able to be measured by housing the animals individually, with the result that the pigs ate more, grew faster, and became fatter than pigs housed in groups [1]. According to McSweeny (2001) [2], the three most commonly used electronic feeders developed for pigs are the ACEMA 48 feeders developed in France, the IVOG feeders (individual voluntary feed intake recording in group pens) developed in Wageningen, The Netherlands, and the FIRE (feed intake recording equipment) feeders originally developed in England These electronic feeders provide farmers and researchers with the identification number and the feed intake record of each pig, and have the capability to record the feeding time, feed intake per visit, and frequency of visits. Numerous researchers consistently reported a strong genetic correlation of DFI with feed efficiency traits, including FCR, G:F ratio, and residual feed intake (RFI), and production traits, such as ADG, BFT, and LP [6,7,8] Overall, these observations suggest that feeding behaviors or pattern traits respond to selection and may be used as an auxiliary trait in improving feed efficiency (FE) and production traits (PTs) in swine. This study aimed (1) to estimate the genetic parameters of feeding pattern traits, (2) and their genetic relationships to feed efficiency and production traits, (3) and to estimate the non-heritable common spatial pen effect for all studied traits of DD pigs used in this study
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