Table 10.

ABMs selected for the assessment of prolonged hunger in pigs during preparation, while in transit and during journey breaks

ABM	Definition and interpretation of the ABM
Aggressive behaviour	Definition: Negative social interactions such as fighting, head‐knocking, threatening, and biting (Welfare Quality®, 2009). Interpretation: Negative social interactions occur during most transport stages due to mixing of unfamiliar pigs, and are generally increased in pigs that have been food deprived.
Latency to feed after unloading	Definition: A quantification of the time interval from unloading and until the animal is observed eating for the first time Interpretation: A short latency to eat is a reflection of a high motivation to eat. Can be affected by other factors such as fear.
Competition for feed	Definition: Occurs when more than one pig tries to access a food source or one pig monopolise the feed. Usually, aggression is seen. Interpretation: When pigs start to compete for access to feed, it is a sign of increased motivation to eat.
Plasma glucose	Definition: Glucose is a monosaccharide, which can be stored as a multi‐branched polysaccharide, called glycogen, in skeletal muscle and the liver (Terlouw and Bourguet, 2022). In monogastric animals, like pigs, blood glucose levels reflect the nutritional status of the animal (Shaw and Tume, 1992). Interpretation: Food deprivation diminishes plasma glucose levels and glycogen content in the liver and muscle (Knowles, 1999). The effects on muscle energy depletion at slaughter and meat quality are only visible if glycogen levels reach a certain, low threshold (55 μmol glucose equivalents/g fresh muscle tissue; Terlouw et al., 2021).
Plasma free fatty acids (FFA)	Definition: Free fatty acids (FFA) are elongated hydrocarbon chains with a terminal carboxylate group and are stored in body fat. Jointly with glucose, FFA are degraded via specific pathways to yield energy (Terlouw and Bourguet, 2022). Interpretation: Increased concentrations of FFA may indicate increased breakdown of fat in response to undernutrition (Shaw and Tume, 1992). When glucose levels are relatively low, plasma FFA levels, and their uptake and oxidation by the muscles increase (Romijn et al., 1995). Food deprivation increases FFA in blood (Brown et al., 1999).
Muscle glycolytic potential	Definition: Muscle glycogen can be measured alone or within the glycolytic potential (GP), which is a measure of all compounds present in the muscle that can be converted into lactic acid. The GP is an indicator of the muscle’s capacity for post‐mortem glycolysis, and, therefore, of the potential extent of muscle pH decline after slaughter (Monin and Sellier, 1985). Interpretation: Lower muscle GP values are indicative of muscle energy use and depletion after long‐term stress due to, among others, longer period without feed, e.g. longer post‐transport lairage (Rocha et al., 2015).

ABM: animal‐based measure.