How to Create Conditioned Taste Aversion for Grazing Ground Covers in Woody Crops with Small Ruminants

Summary

Feeding behavior preferences in livestock can be modified to implement a grazing management plan in woody crops. Here, we present a protocol to show a lithium chloride dose after eating a new plant that induces conditioned taste aversion.

Abstract

Conditioned taste aversion (CTA) is a learning behavior process where animals are trained to reject certain feed after gastrointestinal discomfort has been produced. Lithium chloride (LiCl) is the preferred agent used in livestock to induce CTA because it specifically stimulates the vomit center. In addition, LiCl is commercially available, and easy to prepare and administer using a drenching gun. Nevertheless, some factors have to be considered to obtain an effective long-lasting CTA, which allows small ruminants to graze during the cropping season. A key aspect is to use animals with no previous contact with the target plant (the plant chosen to be avoided; new feed). Due to their native neophobic feeding behavior, small ruminants can easily associate the negative feedback effects with the new feed, resulting in a strong and persistent CTA. The recommended doses are 200 and 225 mg LiCl/kg body weight (BW) for goats and sheep, respectively. To induce CTA, 100 g of the target plant should be individually offered for at least 30 min, and LiCl administered thereafter if the intake is greater than 10 g. Each time the animal eats the target plant without negative consequences, the CTA becomes weaker. Consequently, to minimize the risk of target plant consumption, it is essential to have sufficient palatable ground cover available. The presence of an alternative feed (of quality and quantity) prevents the accidental consumption of the target plant. A close monitoring of the flock is recommended to remove and re-dose any animal consuming more than 4 bites or 10 g of the target plant. At the beginning of each grazing season, check the CTA status of each animal before moving them to the crop.

Introduction

The use of ground cover between woody crop lines mitigates soil erosion and degradation and increases water, organic carbon and nitrogen retention^1-3. Additionally, ground cover maintains and increases biodiversity, supporting the balance between crop pests and their natural predators. Farmers tend to eliminate weeds by applying agrochemical products or using a reaper machine; thus reducing nutrient competition between crops and green cover. A cost effective way to control ground cover would be the use of small ruminant grazing. An additional benefit from animal grazing is the improvement in soil health and fertility. However, farmers are reluctant to imple....

Protocol

The protocol described below for inducing CTA towards woody crops follows the animal care guidelines of the "Universitat Autònoma de Barcelona" (Bellaterra, Spain) and is approved by the Ethical Committee of Animal and Human Experimentation for sheep and goats (CEEAH, references 770 and 998 respectively).

1. Preparation of LiCl Dose

1. Make a 25% w/v (weight/volume) LiCl solution in distilled water. Alternatively, use clean tap water. The LiCl is extremely hygroscopic therefore it is necessary to take care when handling the powdered chemical.
   1. Weigh 250 g of LiCl and dissolve it in distilled water (LiCl conc....

Results

The results described below were obtained by several studies in CTA toward woody crops in small ruminants conducted at the Universitat Autònoma de Barcelona and they provide evidence to establish the protocol proposed.

Doses of 175 and 200 mg LiCl/kg BW in goats and 200 and 225 mg LiCl/kg BW in sheep were successfully used to induce CTA against woody crops with a single administration, with the exception of two animals which did.......

Discussion

The CTA is easily established in small ruminants if the target feed is a plant which the animal has never eaten before and does not contain an irreplaceable nutrient. Animals have a positive post-ingestive association with a non-toxic feed unless previous contact makes it difficult to change their perception of that particular feed^7,33. The condition taste aversion is produced because LiCl stimulates the emetic system producing malaise or gastrointestinal discomfort³⁴. It has been established that a.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Lithium Chloride PRS	Panreac	141392.1209	Different amounts of same product can be supplied by the same company.
Labelvage drencher 70 mL	Labelvage	240040	Similar product can be used (different brand or volume).