Selective behaviour of goats offered different tropical foliages

Kongmanila Daovy, T R Preston* and Inger Ledin^**

Faculty of Agriculture, National University of Laos, Vientiane Capital, Lao PDR
daovyk@yahoo.com
^* Finca Ecológica, UTA-Colombia, AA #48, Socorro, Santander, Colombia
^** Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences
P.O. Box 7024, 750 07 Uppsala, Sweden
 

Abstract

Feed intake and selective behaviour of local goats offered different tropical foliage species were evaluated in a study using eight local male growing goats around 7 months old and weighing 15.7 (1.1) kg. The goats had free access to six foliage species: Erythrina (Erythrina variegata), Fig  (Ficus racemosa), Jackfruit (Artocarpus heterophyllus), Jujube (Ziziphus jujuba Mill), Kapok (Ceiba pentandra) and Mango (Mangifera indica). The foliages were hung in separate bunches in a large pen with a total amount of 9 % of the body weight (BW) as dry matter (DM), 1.5 % of the BW of each foliage. The goats were fed 3 times per day at 08:00 h; 11:00 h and 14:00 h. The bunches of foliage were weighed before and after feeding to estimate feed intake from leaves plus petioles and stem of the different foliage species. The time spent eating each foliage in minutes was recorded during 9 hours per day from 08:00 h to 17:00 h for one goat per day in 8 days.

The average time spent eating was 260 minutes, and the goats changed from one foliage to another foliage 132 times. Feed intake was 634 g or 4.0% of BW and eating rate 2.5 g per minute. There were large individual differences between the goats in selective behaviour, feed intake and eating rate. The mean time spent eating, number of selective changes and total feed intake were higher for Erythrina, Jackfruit and Kapok foliage than for Fig, Jujube and Mango foliage.

Keywords: Erythrina, feed intake  fig, foliage, goat, jackfruit, jujube, kapok, mango, selective behaviour

Introduction

In the traditional feeding systems in tropical countries, the native grasses, legumes and some foliages are the main feed resources for ruminants. Foliages from trees and shrubs are important feeds for grazing and browsing animals and often contain appreciable amounts of nutrients that are deficient in other feed resources (Komwihangilo et al 2001).

Goats have a habit of selecting their feed carefully when eating and are considered to be agile feeders (Dumont et al 1995; Ngwa et al 2000). According to Steele (1996) goats are continuously searching for feed and are more satisfied when they have a whole range of different plants available including trees, shrubs and grasses. The anatomical characteristics of goats, small mouths and split upper lips, enable them to select even very small parts of a plant. Goats are characterised as generalised feeders since they adapt their choice according to what is available. However, goats are also considered to be very fastidious and even when having a very large selection to choose between they will only consume the most nutritious feed available (Van Soest 1982; Fajemisin et al 1996).

Animal feeding behaviour has been the object of numerous studies and there are a number of explanatory theories regarding the principles of herbage selection by grazing animals (Dumont et al 1995). Knowledge of feeding behaviour is of fundamental importance in management of pastures, especially with regard to the determination of opportune feeding strategies and the type and quantity of supplements to distribute (Claps et al 1997).

Steele (1996) reported that shoots and leaves are preferred to stems when goats are allowed to select. Keskin et al. (2005) showed that goats can spend 26.6 % of their time eating (383 minutes in 24 hours). There are many factors which are important for animal selective behaviour, one of which is method of presentation of feed. Van et al. (2005) suggested that the method of feeding by hanging the foliages was the best way to improve feed intake and eating rate of local goats fed Jackfruit (Artocarpus heterophyllus), Flemingia (Flemingia macrophylla) and Acacia (Acacia mangium) foliage. Pok Samkol (2003) also found the method of hanging best when feeding Muntingia (Muntingia calabura) foliage.

The objective of the present study was to examine the feed intake and selective behaviour of goats offered different tropical foliage species.
 

Material and methods

The animals used in the experiment were 8 local male growing goats. The goats were bought in the area around the Faculty of Agriculture, Nabong campus, Vientiane, Lao PDR. The mean and SD of the initial body weight (BW) of the goats was 15.7 (1.1) kg and the age around 7 months. Before starting the experiment, the goats were treated against parasites with injections of Ivermectin solution (1 ml per 4 kg BW) and were vaccinated against Foot and Mouth disease.

Foliage from Erythrina (Erythrina variegata), Fig (Ficus racemosa), Jackfruit (Artocarpus heterophyllus), Jujube (Ziziphus jujuba Mill), Kapok (Ceiba pentandra) and Mango (Mangifera indica) was hung in separate bunches in a large pen. All foliages were offered in the same amount, 1.5% of the BW as dry matter (DM) and together offered in a total amount of 9 % of the BW. The goats were fed 3 times per day at 08:00 h, 11:00 h and 14:00 h. One goat was let in to the pen every morning and the feeding behaviour was recorded as the time spent consuming each foliage during the day from 08:00 h to 17:00 h. The foliages offered were separated and weighed to estimate the average proportion of leaves plus petioles and stems four times during the experiment and the refusals were also separated into leaves plus petioles and stem every day after feeding. The bunches of foliage were weighed before and after feeding to estimate feed intake from leaves plus petioles and stem of the different species. Fresh bunches of feed and a new goat was provided every day and the procedure was repeated for 8 days.

The data from the preference test is presented in the form of frequencies and means using the Excel program.
 

Results

Time spent selecting different foliage species

The time spent eating during the observation day varied between 178 and 390 minutes, with an average and SD of 260 (60.8) minutes (Figure 1).

On average 48 (11.3) % of the observation day of 9 hours was spent eating. There was also a large variation in time spent eating the different foliages e.g. for Mango from 3 minutes to 38 minutes and for Jujube from 17 minutes to 114 minutes. More time was in general spent on Erythrina, Jackfruit and Kapok than on Fig, Jujube and Mango.

The number of times per observation day the animals changed from one foliage to another ranged from 83 to 207 times (Figure 2) with an average of 132 (47.7) times per day.

In Figure 3 is an example of how many minutes were spent on each foliage.

The figure shows animal number 1, the animal with the lowest number of changes and quite short eating time. Animal number 1 spent close to 4 hours eating during the 9 hours of observation compared to animal 5, that spent 6.5 hours. Animal number 1 selected the Mango foliage only twice and 3 minutes were spent eating the Mango foliage while Erythrina, Fig, Jackfruit and Kapok were selected 14 to 22 times.

Intake of the different foliages species

The intake of the different foliage species for each animal is presented in Figure 4.

The highest DM intake was 809 g/day and the lowest 487 g/day with a mean of 624g per day. The total intake was on average 4.0% of BW. The DM intake of the different foliage species ranged from 53 g in the Mango foliage to 141 g in the Erythrina foliage (Figure 5).

The DM intake of the different foliages, expressed in percent of BW,  varied from 0.3% to 0.9 %, with the lowest value for Mango foliage and highest for Erythrina.

The intake of stem (Figure 6) was highest in Jackfruit and lowest in Mango.

Relation between intake and eating time, and eating time and number of changes from one species to another

The total DM intake (Figure 7) was significantly related to eating time (P=0.002, R²=0.93); the longer the eating time the higher the feed intake. The number of changes from one species to another (Figure 8) was also significantly related to the eating time (P=0.002, R²=0.80); the longer the eating time the higher the number of changes from one foliage to another.

Discussion

Time spent selecting different foliage species

The total time spent eating throughout the observation day ranged from 178 to 390 minutes. Theng Kouch et al (2003) found that the eating time was 308 min in 24 h; Keskin et al (2005) reported an eating time of 383 minutes in 24 h and Van et al (2005), 255 minutes in 24 h. The average time spent eating in the present study was 48 % of the 9 observation hours, higher than Theng Kouch et al (2003), Pok Samkol (2003) and Keskin et al. (2005), who recorded 21.4 % of 24 h, 35.2 % of 10 h and 26.6 % of 24 hours, respectively. The difference is probably due to the fact that the goats eat mostly during the daytime (Van et al 2005) while they ruminate or sleep in the night time. The period used for recording eating time will thus affect the proportion of time used for eating.

The goats spent most of their eating time on Erythrina, Jackfruit and Kapok, foliages, obviously having the best intake characteristics of the six foliages compared. These three foliages also had the highest crude protein content and digestibility (Daovy Kongmanila  et al 2007) which confirms the opinion of several authors that goats choose and consume the most nutritious feed available (Van Soest 1982; Fajemisin et al 1996). However, the goats also spent quite a long time (114 minutes, more than 40% of the total eating time) on the lower quality foliages. Even though intake of e.g. Jujube was not very high it has been shown that the foliages from the Ziziphus family are preferred by goats (Ngwa et al 2000).

The number of times the goats changed from one foliage to another, and total time spent eating, ranged from 83 to 207 times and 4.0 to 6.5 h, respectively. It seems that eating time and way of selection are highly individual characteristics and can vary within quite a wide range. This has also been noted by among others Morand-Fehr et al (1991) and Abijaoude et al. (2000), who found that the eating time of goats varied between 4 h and 9 h per day.

In general the behaviour study confirmed earlier studies that goats prefer to select and consume many different types of foliage every day (Sanon et al 2007) and will do so even if the nutrient quality of some of the foliages is not high.

Intake of the different foliage species

The mean DM intake per observation day was lower, 624 g and 4.0% of BW, compared to the 4.2% to 4.8% of BW obtained by Theng Kouch et al  (2003) and Van et al (2005), respectively, when using the hanging method of feeding Jackfruit, Mulberry and Cassava foliage. Hanging seems to be the best way to improve feed intake and eating rate of goats, especially when the foliages have low intake characteristics (Theng Kouch et al 2003; Pok Samkol 2003; Van et al 2005; Ammaly Phengvilaysouk and Lampheuy Kaensombath 2006), although intake will also depend on foliage species available. When the goats have many species to choose between they will obviously not only select the foliages with the best quality but also eat small amounts of other foliages, as discussed above, and this will result in lower intake. In the case of Van et al. (2005) Jackfruit was the only foliage available. The low DM intake of Mango foliage, 53 g or 0.3% of BW, compared to the other foliages, is probably due to the structure of the leaves. The leaves of Mango are hard and have a high DM content and the goats preferred the petioles to the leaves and stems of Mango. The Erythrina foliage had a soft and smooth structure in all parts (leaves, petioles and stem) and this could have contributed to the higher intake of Erythrina, as also suggested by Aregheore and Perera (2004).

The proportion of leaves plus petioles and stem of foliage can also have affected the intake. Fig, Jujube and Mango foliages had a higher percentage of stem with a hard structure compared to Erythrina, Jackfruit and Kapok foliages. The highest feed intake was from the three foliages which had a high proportion of leaves plus petioles. Goats generally prefer to select shoots, leaves and stem in that order (Steele 1996).

Relation between intake and eating time and eating time and number of changes from one species to another

There was a close relation between total DM intake and eating time, and also eating time and number times the goats changed foliage species, respectively. This resulted in a mean eating rate, of 2.5 g per minute compared to 1.1 g per minute obtained by Pok Samkol (2003) and 3.5 g per minute recorded by Theng Kouch et al (2003). Differences in eating rate can be due to individual characteristics as well as type of feed and methods of presenting the feed.
 

Conclusions

• The mean time spent eating and selecting, the number of selective changes and the total DM intake of goats were higher when fed Erythrina, Jackfruit and Kapok foliage compared to Fig, Jujube and Mango foliage.

• However, there were large individual differences concerning preferred foliage species, eating rate and selective behaviour.

• Of the foliage species studied, Erythrina especially, but also Kapok, seem to be interesting species, on which little research, at least when used as a feed for goats, has been done.
   

Acknowledgements

The authors would like to acknowledge the Swedish International Development Agency/Department for Research Cooperation with Developing Countries (Sida/SAREC) for funding this study. Thanks are also due to the Faculty of Agriculture, National University of Laos for making the facilities available and the four students of HD₃ (12^th Generations) in this institution for the help in the data collection.
 

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