Modelling feeding behaviour, rate of feed passage and daily feeding cycles, as possible causes of fatigued pigs

Abstract

This study was initiated to understand whether feeding behaviour and physiology may contribute to the rate of fatigued pigs at processing plants. Specifically, this study sought to determine: (1) how often pigs eat during the day, (2) the times of the day they eat and (3) a first approximation of the time from feed consumption to excretion (rate of passage) when housed in a group in conventional finishing facilities. Finally, models were constructed to try to predict the percentage of pigs with empty/diminished gastrointestinal (GI) tracts depending on the time of day of truck loading and transport durations. Pigs were randomly selected, weighed and selected for behavioural observations. From video records and live observations, the number of meals (feeding bouts) per day and the time of the day meals took place were recorded. Feed containing chromic oxide was fed to determine when a given meal was excreted. With the feeding times of day determined, models were constructed of the percentage of pigs that would have empty stomachs depending on the time of day pigs were removed from the barn and the length of transport/lairage. Finishing pigs housed in groups ate 5.6 6 0.6 meals per day with an average feeding bout (meal) length of 11.3 6 1.1 min. Many pigs fed ad libitum ate most of their meals during the afternoon and evening. The rate of passage of feed was 20.5 h (range 5 18 to 24 h). Because fewer pigs ate in the late evening through morning, if pigs were shipped at these times they would have an increased risk of arriving at the stun at a plant with an empty GI tract. Some of the variation in rates of fatigued pigs and pork quality may be explained by times of day taken off feed and transport duration. Shipping in the afternoon or early evening may result in fewer pigs with empty/diminished GI tracts at processing which may influence the rate of fatigued pigs and pork quality.

Effects of feed withdrawal prior to slaughter and nutrition on stomach weight, and carcass and meat quality in pigs

“…Furthermore, the welfare of fasted pigs still needs to be elucidated as pigs arriving at slaughter with empty stomachs are likely to feel hungry, as suggested by the increased drinking rate. Furthermore, Lewis and McGlone (2008) have suggested an association between the incidence of fatigued or downer pigs and fasting time based on the reduced blood glucose levels in fasted pigs caused by feed restriction. However, further research is needed to validate this hypothesis.…”

“…The diurnal feeding behaviour of finishing pigs is likely to have a significant effect on responses to fasting in a number of the aspects discussed in this review, such as carcass yield, GI tract contents, and muscle glycogen levels. In a model based on pig daily feed intake and feed passage rate through the GI tract, Lewis and McGlone (2008) predicted that shipping pigs early in the morning (between 0400 and 0800 am), combined with transportation of 4 h or more, would increase the incidence of empty stomachs at slaughter because pigs consume relatively little feed during the night time. Indeed, pigs consume the majority of the daily feed intake in a 12 hour period between approximately 0600 h and 1800 h. For example, Hyun et al, (1997) and Ellis (2001, 2002) showed that both growing and finishing pigs consumed approximately 70 to 75% of the daily feed during the daytime (0600 to 1800 h).…”

Simulating pigs : Understanding their motivations, behaviour, welfare and productivity

“…In a study of Lewis and McGlone (2008) on pigs with ad libitum feed, the duration of digestion was on average 20.5 (+/-0.31) h, with a range of 18 to 24 h. Therefore, it was assumed in the model that Diet_digestion was 20.5 hours (1230 minutes).…”

“…De Lange, 1995;Wellock et al, 2004;Yoosuk et al, 2011), or use empirical (regression) equations to include feeding patterns, which means that they do not provide information about motivations underlying these patterns (e.g. Lewis & McGlone, 2008;Morgan et al, 2000). Therefore, a mechanistic and dynamic model was developed that included motivations underlying feeding behaviour and various feeding patterns (Chapter 3).…”

“…Models that do include short-term pig feeding patterns (e.g. Lewis & McGlone, 2008;Morgan et al, 2000) are empirical (regression) equation models, which do not model mechanistic effects on feeding patterns, which are essential to gain more insight into mechanisms underlying feeding patterns.…”