Inappetence refers to a reduction in appetite and feed intake (synonymous with reduced appetite or shy feeders). Inanition is defined as the state of exhaustion resulting from lack of food and water. Inanition is used to describe deaths in the live export industry due to prolonged refusal of food or inability to eat. Starvation refers similarly to the prolonged effects of deprivation of food or food refusal. Prolonged inappetence may progress to inanition and also results in increased risk of other conditions, such as salmonellosis causing severe and sometimes fatal infections in compromised animals.
Inanition and salmonellosis are the most common causes of death in exported sheep and goats and may occur separately (one disease resulting in death without evidence of the other) or together in the same animal. The first week of a sea voyage appears to be at elevated risk of salmonellosis while inanition tends to occur more in later stages of a voyage.
Figure 1.2: Unified causal web describing factors influencing risk of inappetence, salmonellosis and inanition in sheep (LIVE.0132)
Causal factors contributing to inappetence in sheep and goats are not well described. Adult, fat sheep exported during the second half of the year and coming from a high plane of nutrition, and feral goats appear to be at higher risk. Inappetence may appear in individual sheep or in lines of sheep, and there appear to be farm-level factors contributing to risk of inappetence such that some farms may be at higher risk than others. It is presumed the stresses of transition from pasture to feedlot conditions may contribute to the risk of inappetence including transport, curfew periods without feed or water, and transition to water troughs and pelleted feed. The greater appetite of younger, growing sheep, and sheep coming from a lower plane of nutrition is thought to protect animals from inappetence.
While most sheep that are inappetent in the assembly feedlot will start feeding during the early part of a voyage, inappetence in the feedlot is considered to indicate risk of prolonged inappetence continuing during the voyage with elevated likelihood of inanition and death.
Mortality studies in the late 1980s and early 1990s (LIVE.112, 2002) suggested that persistent inappetence was the single major initiating condition that then led to elevated risk of subsequent occurrence of either inanition or salmonellosis (each associated with high mortality risk). More recent work (LIVE.123 2008, W.LIV.0132 2009) has suggested that inappetence and salmonellosis may occur separately or together and initial occurrence of either condition can then lead to increased risk of the other. The unified causal web presented in W.LIV.0132 (2009) and depicted in Figure 1.2, describes a complex pattern of causal factors that may lead to one or the other condition or both. The point of this is that control and prevention efforts need to be directed at both inappetence and salmonellosis and not just at inappetence.
Affected animals can be difficult to identify except by extended or careful observation. Animals may be noticed as not pushing forward to eat at feeding time, so called 'non competitors', and may show varying signs from hollowing of the left flanks to obvious emaciation. At postmortem the rumen is shrunken containing light grey-coloured fluid and very little food material. The lining, normally papillated, will be smooth. The intestines are empty.
Specimens for laboratory determination include serum for beta hydroxybutyrate estimation and heart, liver, kidney, pancreas, bone marrow and long bone diaphysis in buffered formalin for histology.
Treatment is symptomatic and may not always be successful. Early recognition, separation, provision of adequate trough and floor space, and feeding of high quality chaff or fresh hay may encourage eating. Where multiple animals in a mob appear to be inappetent during the assembly feedlot, adding or resuming addition of chaff or hay to a pelleted diet may encourage animals to eat and facilitate transition to eating pellets in preparation for loading onto an export vessel.
Ensure healthy livestock are sourced for export. Avoid stress or prolonged periods of feed and water curfew during transportation into the assembly feedlot, and while managing animals in the feedlot. Provide shelter so animals can avoid extreme weather during feedlotting.
Provide high quality feed and water, and observe reasonable standards of hygiene. Avoid pellet dust when feeding pellets, particularly on board ship when pellets may be deleivered through automatic feeding lines. Consider adding additional trough space and providing troughs in the middle of feedlock paddocks and on the inside of pens on board ship, in an attempt to allow shy feeders increased opportunity to access feed.
There is conflicting evidence over the benefits of feeding sheep hay in the assembly feedlot including some evidence that feeding hay may actually contribute to inappetence. Alternatives include the feeding of lucerne chaff with pellets as an initial introductory strategy, and introducing sheep to pellets that contain lower concentrations of starch in an attempt to avoid risk of acidosis which may exacerbate inappetence.
Lines of sheep that have high levels of inappetence in the assembly feedlot may be pulled from the voyage because of the increased risk of mortality from subsequent inanition and possibly other conditions such as salmonellosis.