Dietary choices of goats at the trough (original) (raw)

Review

Dietary choices of goats at the trough

Abstract

This paper reviews a set of experiments underway since 1980 studying the feed and animal factors influencing the feeding preferences of goats at the trough. The methodology used consisted of a series of short-term (4×30

s) cafeteria tests on 12–16 dairy goats. The goats referred to in the present article preferred dry feeds in pellet form to flour and accepted very fine particle flour with difficulty. Goats proved very sensitive to feed prehensibility. Several feeds such as rapeseed oilmeals, fats or meat meals reduced the palatability of mixed concentrate which feeds included them. When the quantity of these feeds of bad palatability was increased in mixed feeds, goat preferences fell abruptly or progressively. Adding commercial aroma containing various flavours to feeds can improve the preferences of goats. There was a wide range of individual variability of responses in the tests. The physiological stage (gestation, early- and mid-lactation) did not influence the preferences. Previous or daily diets modified goat preferences. Generally goats seeked diversity in their ingesta, probably to maintain the rumen environment within a certain physiological and microbial range.

Introduction

The feeding behaviour of goats at the trough (Morand-Fehr, 1981, Dulphy et al., 1990, Morand-Fehr et al., 1991a) and under grazing conditions (Provenza and Balph, 1988, Narjisse, 1991, Rutter, 2002) has already been described. In comparison with other ruminant species, goats markedly select feeds at the trough or vegetation fractions during pasturing, and tend to make more refusals than other ruminants if feed availability is unlimited. Several studies describe goat choices and their seasonal variation under grazing conditions. It is, however, difficult to understand ruminant choices in the complex situations of grazing (Dumont, 1997, Baumont et al., 2000) and of diets composed of feeds ingested throughout the day. As it seems essential to analyse the animal and feed factors influencing the dietary choices of goats without interference by post-ingestive factors, it is interesting to analyse the short-term animal responses under controlled conditions, i.e. at the trough without the effects of environmental and social factors. The aim of this paper is to review the set of experiments carried out by our laboratory since 1980 studying the animal and feed factors influencing the preference of goats at the trough and, consequently, to contribute to explaining the preferences and feeding behaviour of goats.

Section snippets

Methodology used

The aim was to emphasise differences in animal preferences between feeds with very similar characteristics. We quickly observed that in goats the cafeteria-based tests were more discriminating than long trials without choice, where feeds to compare are distributed to different groups or successively to the same goat group. Moreover, cafeteria tests are more rapid and less expensive, making it possible to test many more feeds in a limited period and to study the palatability of feeds or animal

Physical characteristics

Generally, goats preferred dry feeds presented in pellet form to flour form (Morand-Fehr et al., 1991a).

Ouédrago et al. (1996) studied the effects of the moisture and texture of beet pulp and barley grain on goat preferences and the interaction between these two factors in short-term tests. Goats preferred coarse granulometry and totally or partially refused feeds presented in flour form with very fine sized feed particles, because they are very sensitive to the irritation of the respiratory

Individual variability of preferences

In tests where goat preferences for one of two feeds was observed, the coefficient of variation of the ingested quantity of one feed was very variable, from 15 to 120%, and depended on the nature of the feeds. Even if our method of selecting goats tended to limit the variability of individual responses, it was around 40–50% on average. It was very unusual in a short-term test for all the goats to consume more feed A than feed B. Generally, most of them ate more feed A but some of them presented

General discussion and conclusions

The results from short-term tests allow goat preferences, influenced only by feed taste and prehensibility, to be brought to the forefront while avoiding post-ingestive factors. Nevertheless, when feeds have been previously experienced by goats, it is possible that the post-ingestive memory factors influence goat choices. Actually, in our 3

min preference tests, the influence of post-ingestive factors was probably much less important than in 4

h tests (De Rosa et al., 2002) or during a full meal (

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However, when post-ingestive effects are of no relevance, or shall be deliberately excluded, short-term durations may be preferred (De Rosa et al., 2002; Villalba and Provenza, 2000). Especially when a large number of experimental feeds is to be tested, this is a cost-and time effective option for testing of palatability or preferences for experimental feeds (Morand-Fehr, 2003). Choice feeding experiments with ruminants offer an exciting opportunity to obtain information about feeds going beyond the results of classical feed quality assessments as listed in the feed tables. View all citing articles on Scopus

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