Prof. B.W. Peeters PhD1, M.A. Romeijn BSc3, Ing. A

General introduction
Due to its popularity the number of alpacas in the Netherlands increases. Local knowledge on these animals expands by contacts with experts in other countries, use of the scientific literature and by surfing on the internet. However, next to an increase in scientific knowledge there is also an increase in myths and falsehoods on alpacas. This is especially prominent in our area of expertise, farm animal nutrition. Indeed, specific nutrient requirements for alpacas are scarce. We were asked by AlpacArt, a distributor of alpaca feed, to perform research on the feeding and metabolism of these animals. We decided to compare alpacas with sheep, the farm animal for which a lot of validated information is available.
Alpacas are ruminant animals in that they have an expanded fore stomach to facilitate microbial fermentation of ingested feedstuffs. They also chew the cud. However, they are not considered true ruminants (like sheep) as a result of some distinct anatomical and physiological digestive tract differences. There are differences in bacterial diversity and abundance in the fore stomach. Furthermore, cellulolytic activity (Pei, C.X. et al. 2010) and feed retention time (Heller et al. 1986) in the fore stomach of alpacas is higher compared to that of the rumen in sheep. Consequently, it may be suggested that alpacas versus sheep are superior in the digestion of fiber rich feedstuffs such as hay. Indeed, there is suggestive evidence that supports the idea that alpacas are more efficient in fiber digestion than sheep (San Martin, 1989; Dulphy, J.P. 1997; Sponheimer 2003; McGregor, B.A. 2002). However, the experimental set up of these studies does not exclude the possibility of feed selection thereby potentially overestimating the digestibility of nutrients in alpacas. Therefore, the objective of the current experiment was to compare the digestibility of mainly the cell wall fraction of hay between restrictively fed alpacas and sheep.

The study
Five female huacuya alpacas and five zwartbles sheep (Dutch breed) were used. The mean body weight of the alapas and sheep at the start of the experiment was 70,4 kg (SD 7,4) and 71,3 kg (SD 6,4), respectively. The animals were housed in individual pens and were fed a restricted amount of 40g hay/kg body weight per 24 hours. It was anticipated that this amount of hay was enough for the animals to maintain a constant body weight. Hay was supplied twice daily in two equal portions at 09:00 and 15:45 hours. During the morning feeding the animals were also fed 50 grams of pelleted concentrate containing alfalfa and titan dioxide as a digestibility marker. Water was supplied ad libitum. The trial took place during November and December 2010 in the Netherlands.


The trial lasted 17 days and was preceded by a seven day run in period that allowed the animals to become adapted to the experimental feed. During the last seven days of the experiment feed refusals and feces samples were collected. Feed refusals were collected quantitatively to calculate actual nutrient intake feed. Samples were dried at 70 0C, grinded on a 1 mm screen and stored at -20 0C until analysis. Feces were collected between 09:30 and 16:30 hours. After collection, feces were weighed and stored at - 20 0C until analysis. Dry matter (DM), organic matter (OM), neutral detergent fiber (NDF), acid detergent fiber (ADF), crude protein (CP) and the marker titandioxide were analysed in hay, feed refusals en feces.

Results
Both the sheep and alpacas remained on the same body weight although the alpacas did fully consume their hay; the mean amount of hay refused was 102 ± 39,8 gr DM per day. The sheep had no feed refusals. Consequently, nutrient intake in alpacas is somewhat lower than that of sheep (Table 1). Furthermore, significant differences in apparent digestibility of nutrients between alpacas and sheep could not be detected in the current experiment.

Table 1: Nutrient intake and corresponding digestibilities of hay fed to sheep and alpacas
Species
Sheep Alpaca effect of species
mean SE mean SE p
DM1 (gr/day) intake 961 58,2 858 84,1
(% of intake) DC 63 1,7 60 2,6 0,3

OM (gr/day) intake 883 54,4 792 77,9
(% of intake) DC 65 1,5 64 3,0 0,9

NDF (gr/day) intake 556 34,7 492 51,4
(% of intake) DC 63 1,2 63 3,1 1,0

ADF (gr/day) intake 315 19,7 276 30,0
(% of intake) DC 62 1,3 61 3,3 0,7

CP (gr/day) intake 56 3,2 51 4,2
(% of intake) DC 47,5 3,6 44,4 6,3 0,7

1) DM = dry matter, OM = organic matter, NDF = neutral detergent fiber, ADF = acid detergent fiber, CP = crude protein, DC = digestibility coefficient


Discussion

Our finding of a similar digestion between alpacas and sheep is supported by some authors (Cordesse, R 1992). However, other studies suggest a higher digestive efficiency of alpacas than of sheep (San Martin, 1989; Dulphy, J.P. 1997; Sponheimer 2003; McGregor, B.A. 2002). It was already mentioned that the experimental set up of these studies does not exclude the possibility of feed selection. Indeed, when animals prefer to consume the parts with a high digestibilty fecal excretion is decreased and overestimation of digestibility occurs. In the current experiment, nutrient intake was determined by subtracting the refused amount of nutrients from the amount supplied thereby preventing the risk of overestimation of the digestibility. In conclusion, although there are differences in anatomical and physiological factors between alpacas and sheep (figure 1), their forage digestion is remarkably similar. This does however not mean that alpacas should be fed like sheep. The differences in digestive processes will have consequences which will be investigated in our future studies.


Figure 1: Comparison of forestomach compartments in Ruminantia and in Camelidae Lechner et al. 1995 The forestomach of alpacas differs from that of ruminants; it is divided in three compartments (C1,C2,C3). C-3 is an elongated tubular organ with fermentation activity in the proximal region. Stomach volume of C-1, C-2 and C-3 account for respectively 83, 6%, and 11% of total stomach volume, (Vallenas et al., 1971)

Alpacas imported from South America into the Netherlands show decrease in fleece quality. It is often suggested that this decrease in fleece quality is associated with the high quality of the Dutch pastures but the underlying mechanism is not known. Of course there is also the possibility that the observed decrease in fleece quality when enjoying the Dutch pastures is not causal. Nevertheless, the outcome of the current experiment can be interpreted in that current energy requirements of sheep can be extrapolated to alpacas This provides a basis for further experimentation with alpacas with the ultimate goal to increase the fleece quality of alpacas by manipulating the composition of the feed.



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