The overall goal of this procedure is to create conditioned taste aversion in small ruminants used for grazing ground covers in woody crops. In woody crops, ground cover is used to mitigate soil erosion and degradation, however grasses compete with the crop for nutrients and water. Ground cover is usually controlled by agrochemical products and tillage.
Never the less, grazing with small ruminants could be a more sustainable and eco friendly alternative. The main issue of grazing woody crops with small ruminants is that young leaves and sprouts are very palatable and attractive for them, as a consequence, to prevent crop damage and production loss grazing is not currently used. A useful tool to prevent animals from consuming a particular feed is conditioned taste aversion, or CTA, a methodology based on self learning feed behavior.
The first time that an animal consumes a specific feed this creates a post ingestive response that the animal can associate with that feed. If the feedback is positive, that is it provides adequate nutrients, the animal would then increase their consumption. If the feedback is negative, that is it creates illness or discomfort, the animal would then avoid it's consumption.
To create aversion against woody crops we have to administrate a lithium chloride dose to induce negative feedback. Lithium chloride is the most used indicator agent for feed aversion in small ruminants mainly due to it's strong, long effect, and persistence. It's mechanism of action is on the medic system which will produce some gastrointestinal discomfort.
Those animals will show signs of decreased appetite or feed intake, some ears and head drop, and in some case inactivity. Lithium chloride, the most important is that it's secreted in 96 hours, mainly by urine. Make a 2.50%weight volume lithium chloride solution in distilled water and calculate the milimeters of the solution needed for each animal.
The recommended dose is 225mg LiCl/kg for sheep and 200mg LiCl/kg for goat. Select adult, non pregnant and dry animals that have never previously eaten the target feed. On day zero offer 200g of the target feed to each animal for 30 minutes.
If they consume more than 50g administer the lithium chloride dose. From day one to three do not offer the animals the target feed. Also, check them periodically to detect any possible sign of severe illness.
On the fourth day after lithium chloride administration offer the target feed and if the animals consume less than 10g, the CTA is considered to have been established. If any animal consumes more than 10g administer a further lithium chloride dose. If the animal persists in consuming the target plant after the second dose, eliminate it from the CTA group.
Repeat this process for two further days. Although a single lithium chloride dose induced complete CTA against a new feed, it was not enough to induce CTA against a familiar feed. Only a slight decrease in the target feed intake was observed when comparing the control to the CTA group on the following day.
The CTA induced against grape vine leaves with a 225mg LiCl/kg single dose was complete intake was less than 10g throughout the first year. Never the less, during the following two years a reinforcement dose was necessary to strengthen the CTA. After watching this video you would have a good understanding how to induce aversion toward crops in small ruminants.
The process will not take longer than a week, we can use the averted animals to control the grass cover without damaging the crop.
