Manipulation of feeding behaviour for ruminant production: techniques for better use of novel feeds 
for  goat production in central part of Vietnam

Dam Van Tien and Le Thi Van Ha

Hue University of Agriculture and Forestry,
24 Phung Hung, Hue, Vietnam
upland@dng.vnn.vn

  

Abstract

This study was conducted in the semi-arid area of Phanrang in dry season and comprised two experiments. The aim was: (i) to determine whether the time take by goats to eat rice straw (novel feed) might be reduced by adding juice from native grasses with an odour and flavour familiar to the goats; and (ii) to test if encouraging goats to ingest new feeds, including rice straw and rice bran, in their early lives while with their mothers or with other experienced goats, might make it easier to adapt  to these supplements after weaning.

 

In Experiment 1, each morning in a 15-min test, groups of goat (already adapted to the testing procedures) were offered rice straw in the presence or absence of odour and flavour of grasses. Another group was offered the rice straw with the odour of parasitised goat faeces. When offered the rice straw in the presence of grass juice odour or flavour, goats started to eat a small amount of the feed on day 5 increasing to 50 g and 53 g by days 15 and 18 respectively. The control animals did not eat the straw until day 10, and then increased daily intake to 48 g by day 22. In contrast, goats avoided the rice straw with the odour of parasitised animal faeces for 20 days and the daily rice straw intake of goats in this group never exceeded 15 g during the test.

 

In Experiment 2, the speed of learning to eat novel feeds (rice straw and rice bran) in their early lives. in the presence of their mothers or experienced peers, was studied. Goats were introduced to the novel feeds in a group with 4 mothers or 4 experienced adults for 15 min in each of 7 consecutive days. Three months later, all the young goats were tested as to whether they had learned from their mothers, or from their peers, in their capacity to eat rice straw and rice bran. The group of naive goats with no teachers (control) ate no supplements over the 7 days of the test. The group of “learning from mother” and “learning from experienced ones” ate 51 and 52 g of  rice straw on day 6 and day 7, and 97 and 98 g rice bran on days 6 and 7, respectively.

 

Key words: Nephobia, novel feed,  post-ingestive consequences,  odour,  flavour,  feed preference, goats

 

Introduction

It is convenient to adapt goats,  and also other animals,  to learn to ingest new feeds before they are introduced into an environment where the “novel” feed will be the staple (eg: in a feedlot, or for emergency feeding during drought). However, ruminants are often reluctant to eat novel feeds when they are first exposed to them (Provenza and Balph 1990; Nolan et al 1995; Tien et al 1999). In fact, nephobia is common in many vertebrate species (Corey, 1978) particularly when confronted with unfamiliar (but edible) feeds. Nephobia is probably the basis of a protective process that allows animals to avoid toxicosis while learning from the post-ingestive consequences of eating a new and potentially toxic feed. Feed nephobia, which means animals are fearful of anything new, often occurs during the first period of feed adaptation. Thus they are  scared of the feed and the feed trough as well. There are some ways to overcome nephobia such as the addition of extracts from grasses which have a familiar odour or flavour (Tien et al 1999) and training the animal  to ingest new feeds in their early lives while they are with their mothers or  other experienced animals (peers) (Lobato et al 1980). There have been few studies with goat to investigate these possibilities. The present study was designed to test if goats would more readily begin to eat an unfamiliar feed when it was associated with neither the odour or flavour of familiar native grasses. We also wished to test if the goats would respond (reduce their feed nephobia after weaning) to a training programme  designed to encourage to ingest a new feed in their early lives while with their mothers or with experienced “peers”.

 

Materials and methods

Grass odour and flavour to overcome feed nephobia in goats

The study was carried out in Trihai Village, Ninh Thuan province, southern Vietnam. The rate of ingestion of an unfamiliar feed (rice straw) by goats was determined when these feed were offered in conjunction with a familiar flavour or odour of native grasses. Bachthao goats  obtained from Xuan farm in this village were used in the study. Twenty-four animals (7-8 months of age and approximately 35 kg) were selected for the test. None of the goats had previously been exposed to rice straw.

 

Treatments and design

Six goats were randomly allocated to each of four treatments:

 

C: Rice straw with no odour or flavour additives (control )

GO: Rice straw with grass odour nearby (odour group)

GF: Rice straw mixed with grass juice (flavour group)

PF: Rice straw with odour of parasitised -goat faeces nearby (faecal odour group)

Odour and flavour preparation

Three grasses (Cyperus rotundus L., Cynodon dactylon (L.) Pers, and Brachiaria distatachya (L.) Stapf) were identified by farmers in Trihai village as being highly acceptable to the goats . These grasses were used in this study. Early each morning during the testing period, about 500g of each grass was harvested. The grasses were mixed and then squeezed using a machine traditionally employed in the village for extracting sugar cane juice. Water (300 ml) was added to the mulched residues that were then wrapped in mosquito netting and compressed to extract a solution of grass juice.

 

Fresh faeces (3 g) from a parasitised goat were collected every morning during the test period and maintained in a moist state throughout the test.

 

Testing area

The testing area was a yard (1.5m x 3.0m) large enough to hold 6 goats and to accommodate two feed troughs, from which 3 animals could feed simultaneously. Two fenced paths were constructed between the covered pen where animals were held overnight and the two 'test' yards. These pathways enabled two groups of six goats  to be guided from the pen to each of the two yards and then tested simultaneously. The two wooden feeders in each yard were 1 m in length and provided enough space for 3 animals to eat side by side in separate compartments. Bamboo lattice was used to make the feeder floor (0.5 m above the ground), and also the sides and compartment dividers. The design of the feeding area allowed the goats to see each other throughout the test period.

 

Testing procedures

Before the testing with rice straw, all animals were exposed to the testing environment and routine for 3 days. Sham testing was done using native grasses that are familiar to the goats, but were not the source of the grass juice solution to be used later. After an overnight fast in the holding pen, all goats  were offered chopped rice straw in conjunction with odours or flavours and intake was measured over a 15 minute test period. The rice straw was placed on the bamboo lattice feeder base, the mesh size preventing the rice straw from falling through while allowing the odour to permeate the feed. Forty ml of grass juice (Treatment GO) or 2 g of faeces (Treatment PF) were placed 3 cm below the feeder base. For the grass flavour group (Treatment GF), 50 ml of the grass extract were mixed with 1 kg of the rice straw.

 

 The animals in the 'grass odour' and 'grass flavour' groups were tested at 06.00 to 06.30h each day. Six goats in the 'grass odour' group were placed in the yard containing feeder 1 and 2 while the remaining six goats  (grass flavour group) were placed in the yard containing feeders 3 and 4. The goats in the 'faecal odour' and 'control' groups were tested in a similar way at 07.00 to 07.30h.

 

After each morning's tests, the feed containers were thoroughly cleaned, rinsed and air-dried and the animals allowed to graze together for about 8 hours. The testing procedure was continued for  40 days.

 

Training  goats  to ingest new feeds in their early lives with their mothers and experienced peers

Experimental group

This experiment was also conducted at Trihai village, Ninh Thuan provice. Eighteen Bachthao goats (3 months of age) were used for training. The rate of learning about eating chopped rice straw and rice bran was determined when they had the opportunity to learn about these novel feeds while with their mothers or with other experienced “peer” animals Six goats were randomly allocated to each of three groups:

 

C: No supplementation (traditional practice) for animals before weaning but supplementing  with chopped rice straw and rice bran after weaning (during the test period)

LM: Offering chopped rice straw and rice bran to young goats with their mothers (n=4) for one week, but offering these feeds without their mothers after three months later (for testing)

LP: Offering chopped rice straw and rice bran to young goats  with other experienced goats  (n=4) for one week, then offering these feeds without the presence of the “peers” three months later (for testing)

Training area

The training area was a yard (4m ´ 3m) large enough to hold 10 goats (six young ones and four adults / trainers) and to accommodate two feeders, each capable of feeding 5 animals to eat side by side. Two fenced paths were constructed between the covered pen where animals were held overnight and the two 'training' yards.

Training young goats before weaning

At three months of age, all animals in LM (learning from mother) and LP (learning from peers) were exposed to the training environment with their mothers and / or peers, in order to see and learn how the adults ingested the supplements. The details of training were:

• After an overnight fast in the holding pen, six young goats in LM group with four mothers and six other young ones in LP group with four experienced goats (trainers) were offered supplements of chopped rice straw and rice bran.
• The supplements were exposed to the animals for 15 minutes each day. After each morning's training, the animals were allowed to graze together for about 8 hours.

Testing after weaning

After three months of the training with mother or peers, all the goats in the three groups were tested for their voluntary intake of the supplements. In the case of the control group, before the testing, animals were exposed to the testing environment and routine for 3 days. Sham testing was done using native grasses that were familiar to the goats.

• From 6.00 to 6.30, after an overnight fast in the holding pen, six young goats  in the LM group were placed in the yard containing feeders 1 and 2 while the six animals in the LP group were placed in the yard containing feeders 3 and 4.  From 7.00 to 7.15, six young goats in the control group were placed in the yard containing feeders 1 and 2 for testing. 
• Each group was offered rice straw and rice bran. These supplements were exposed to the animals for a 15 minute test each day

 

Results

Experiment 1

Animals in the odour and flavour groups started to ingest a small amount of rice straw on day 5 (Table 1). Goats in the control group did not eat any rice straw during the first 9 days. Animals in the ‘faecal odour’ group rejected the rice straw completely for 20 days. The subsequent intake of individuals in this group was low (generally less than 15 g/day). During the first 18 days of exposure, goats in the odour and flavour groups ate more rice straw than those in the control group (P<0.01) and achieved their highest intake on day 18. In contrast, control goats took 23 days to achieve their highest intake. From day 22 to day 39, there were no significant differences in intake between the odour group and the control group. Intakes averaged over weeks (Figure 1) show that intake differences were manifested in the first two weeks and remained stable in weeks 3 and 4.

 

Table 1: Intake (g) of an unfamiliar feed (rice straw) by goats in the 15-min test when offered the feed alone (control), in association with the odour of grasses (GO) or flavour from the same grasses (GF) or the odour of parasitised -goat faeces (PF)
Days#	Control	GO	GF	PF
1	0	0	0	0
2	0	0	0	0
3	0	0	0	0
4  5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 38 39	0 0 0 0 0 6.2 ± 1.1 7.3 ± 1.3 8.5 ± 1.2 8.8 ± 1.3 9.6 ± 1.7 11.5 ± 1.7 15.5 ± 3.2 20.5 ± 3.8 25.3 ± 7.3 28.0 ± 5.8 37.7 ± 4.9 41.2 ± 2.6 48.0 ± 3.3 44.5 ± 3.5 43.3 ± 4.6 44.8 ± 4.2 45.7 ± 4.6 42.2 ± 5.2 47.2 ± 4.7 42.3 ± 4.5 48.2 ± 3.0 42.8 ± 4.0 43.8 ± 5.8 43.5 ± 5.3 48.8 ± 4.5 46.3 ± 3.5 46.5 ± 3.0 47.2 ± 2.9 47.5 ± 3.8 48.0 ± 3.6	7.6 ± 1.4 8.2 ± 1.3 9.3 ± 0.7 10.2 ± 1.8 11.9 ± 1.7 14.2 ± 1.1 15.2 ± 1.6 16.8 ± 1.8 19.5 ± 2.2 23.8 ± 2.1 26.5 ± 3.0 32.0 ± 4.5 39.2 ± 2.9 50.0 ± 5.0 47.0 ± 1.6 49.2 ± 4.4 47.0 ± 2.6 48.0 ± 4.7 48.2 ± 3.1 42.3 ± 4.2 43.7 ± 4.6 47.2 ± 1.8 46.3 ± 3.3 47.0 ± 3.8 46.5 ± 6.2 43.0 ± 4.3 47.2 ± 3.5 44.0 ± 4.8 45.8 ± 4.9 49.0 ± 3.6 48.6 ± 3.9 47.5 ± 3.9 48.5 ± 3.4 48.8 ± 1.9 47.8 ± 3.7	8.5 ± 1.4 9.8 ± 1.8 10.8 ± 1.1 12.1 ± 1.8 14.0 ± 1.1 15.6 ± 2.0 17.8 ± 2.7 19.2 ± 2.1 26.2 ± 3.1 38.2 ± 4.9 53.0 ± 5.2 50.5 ± 2.8 48.3 ± 4.2 52.2 ± 3.7 52.3 ± 3.8 50.5 ± 2.6 47.0 ± 4.3 47.2 ± 3.8 49.0 ± 4.1 44.3 ± 4.9 51.0 ± 2.8 52.8 ± 3.6 43.8 ± 5.7 44.2 ± 3.9 45.3 ± 4.1 50.2 ± 5.3 50.0 ± 5.0 45.5 ± 2.9 45.8 ± 3.3 48.2 ± 4.5 44.5 ± 5.3 47.0 ± 5.2 48.5 ± 2.8 51.5 ± 2.7 48.7 ± 3.9	0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 4.8 ± 1.5 5.8 ± 2.2 7.3 ± 2.5 9.5 ± 1.7 8.0 ± 3.2 9.1 ± 3.8 5.8 ± 2.5 10.8 ± 2.2 13.0 ± 1.9 14.2 ± 2.9 15.0 ± 1.7 11.8 ± 3.3 9.8 ± 4.0 7.5 ± 1.2 6.0 ± 1.5 11.5 ± 2.4 9.0 ± 2.1 7.5 ± 2.8 8.3 ± 2.3

 

 

 

 

 

In Experiment 2, the group of ‘naïve’ goats with no teachers (control) ate no supplements over the 7 days of the test (Table 2). The LM group (“learning from mother”) and the LP group (“learning from peers”) ate more feeds (P<0.001) than the control group reaching intakes of 53 g rice straw and 98 g rice bran by day 7, respectively (Figures 2 and 3).

 

 

 

 

 

 

Discussion

Feed preference for a particular feed depends not only on odour and/or flavour, but also on the interaction between taste and post-ingestive effect (Provenza 1996). A hedonic sensation may accompany both of these processes. As can be seen in the Table1, except for the rice straw with odour of the parasitised-goat faeces, the intake of rice straw was little changed during the final period of training, and the goats appeared to have adopted an acceptance for rice straw in about three weeks. It is also reasonable to say that odour or flavour effects of native grasses are not effects on long-term intake of rice straw but on short-term intake.

 

Evidence from experiment 2 suggests that animals have long memories of the learning  associations they make during the time of training to eat rice straw and rice bran with their mother or adult ‘peers’ in their early lives. Studies in sheep shown that lambs with experience of molasses-urea blocks 6 months previously had higher intakes than similar lambs with no such experience (Lobato et al 1980). Similarly, McDonald et al (1988) found that Merino wethers with experience of supplementation 16-18 months previously as suckling lambs in groups with their mothers, consumed more pellets than those that had never experienced supplements. Moreover, in the post-weaning period as young ruminants begin to forage, those that were reared with their mothers learn to select appropriate feeds and avoid feeds containing toxins, more quickly than lambs reared without their mothers (Mirza and Provenza 1990). Social learning about a feed is important in feed selection by animals especially the young ones. This learning refers to the transmission of  feed information from an experienced animal to an inexperienced one, for example, from mother to offspring or from adult to young (Lobato et al 1980; Lynch et al 1983). Information about feeds can be passed quickly from mother to offspring because they are genetically related. 

 

Conclusion

• When goats are given a novel feed like rice straw feed nephobia delays acceptance of this feed. In such circumstances, the association of familiar odours or flavours of native grasses with the unfamiliar feed and exposing a new feed to goats  in early life including learning from mothers and from experienced ones can aid in overcoming nephobia and initiating their early and consistent acceptance of novel feeds.
• These tactical uses may change the entrenched agricultural practices of villagers paving the way for the use of non-conventional feeds in the ruminant production in the region.

 

References

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Lynch  J  J, Keogh  R  G, Elwin  R  L, Green  G  C  and Mottershead  B  E  1983  Effects of early experience on the post-weaning acceptance of whole grain wheat by fine-wool Merino lambs. Animal  Production  36:175-183.

Mirza  S  N  and Provenza  F  D  1990 Preference of the mother affects selection and avoidance of foods by lambs differing in age  Applied Animal Behaviour Science 28: 255-263.

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Provenza  F  D  1996  Role of learning in food preferences of ruminants : Greenhalgh and Reid revisited. In Digestion and Metabolism in Ruminants. pp:1-31.

Tien  D  V, Nolan  J  V, Lynch J J and Hinch  J  N 1999  Grass odour and flavour overcome feed nephobia in sheep. Small Ruminant Research 32 1999) 223-229. Elsevier Science Ltd.