Strategies to reduce inanition in sheep

Summary

Inappetence, the reduction in or lack of appetite with consequent reduced food intake (Blood and Studdert 1999), has been identified as a problem for sheep in the live export process, as a cause of death from inanition, and because of the association with the development of salmonella outbreaks and subsequent death of animals.

To characterise the problem with the typical consignments of sheep currently exported, sheep were monitored at a pre-embarkation feedlot in Western Australia using RFID tags and specially-designed tracking antenna to determine time spent at feed and water troughs. Between September 2011 and June 2012, a total of 8,206 sheep from four different consignments destined for live export were monitored electronically at feed and water troughs, for a range of 6 to 31 d. Inappetence was defined as sheep spending less time at the feed troughs than 2 standard deviations below the mean daily time for the whole group (28m 5s). Based on this definition, it took until day 5 in the feedlot for less than 5% of animals to be spending inadequate time at the feed trough.

Mortality of the monitored sheep was 0.85%. For the first six days, sheep that were alive at the end of their stay at the feedlot spent an average of 1h 12m 09s more per day at the feed troughs than sheep that died. There was no difference in time spent at water troughs (17m 45s ± 14m 0s) between sheep that were alive at the end of the feedlot stay and sheep that died. Salmonella/Inanition was the leading cause of death (61.4 %) and occurred across all months. Transit tetany affected one group of Dorper ewes (0.36 %) in spring and pleuropneumonia was confirmed in (0.3 %) sheep in summer.

The time spent at the troughs per day by each individual, and their outcome as live or dead, was used in linear discriminant analysis to classify sheep as ‘at-risk’ or ‘not-at-risk’ based on a linear function incorporating previous days’ feeding times. In the cases where 1, 2, 6, and 7 d have elapsed, only the previous day’s feeding time was useful in predicting whether or not a sheep was at-risk. However, the number of misclassifications of sheep was large, with a high percentage of ‘not-at-risk’ sheep classified as ‘at-risk’. Therefore, using this model to remove ‘at-risk’ sheep for different management would result in many additional sheep moved unnecessarily.

This system for recording time at feed and water troughs has merit in identifying individual animals which are not eating, and could be used with automatic drafting systems or other non-intrusive management that remove such animals for different feed or attention.

There was some correlation between time spent at the feed troughs and entry, exit and change in BCS, but not sufficiently strong that recommendations could be made regarding an optimum BCS for the process.

There was no indication of the previously reported issues whereby very fat sheep did not eat and developed a fatty liver/ketosis syndrome. Thus, it was not considered feasible or useful to remove the small number of sheep that were not eating from the large group for further study.

A number of feeding strategies considered relatively easy for industry to implement were tested for the potential to increase the acceptance and consumption of a pelletised diet. Between August 2013 and August 2014, 5,382 sheep from five different consignments destined for live export were monitored for a range of 4 to 22 days, with different feed or feeding strategies tested at the feedlot. In February 2015, 666 sheep destined for export from a farm in Southwest WA were selected for an on-farm preparation study.

Feeding strategies tested at the feedlot did not apparently increase acceptance and consumption of the pellets. Housing sheep outside the raised sheds, with access to hay and/or pellets, for a day before entering the sheds did not hasten feed acceptance or increase the number spending an acceptable period at the feed troughs, compared to those housed only in the shed. In one test of these protocols, sheep fed hay and pellets outside for one day before entering the shed had a much higher mortality, diagnosed as primarily due to salmonellosis, than the other groups. In a subsequent examination of the environments, more Salmonella organisms were detected in the outside environment, and in sheep exposed to that environment, than in the sheds and in sheep housed only in the shed, indicating the potential for environmental contamination. Provision of oats on top of the pellets did not increase the visits of time at the troughs compared to those supplied with pellets only. The addition of chaff did result in more visits to feed trough than when pellets alone were available.

The provision of trail fed pellets on farm did not increase the time or number of visits at the feedlot feed troughs. The tested group of sheep all rapidly accepted the pellets and spent more than the minimum time at the feed troughs. Other on-farm factors, along with differences in transport conditions, handling, and prior medical and management practices may be influencing the adaptation to a pelleted diet at the feedlot.
Further research is warranted to explore management practices that improve the resilience of sheep to novel conditions and feeds, resulting in consumption of a pellet diet at pre-embarkation feedlots in preparation for shipping.