A note on the use of Jerusalem artichokes (Helianthus tuberosus L.) in diets for growing pigs

Thirty-two Yorkshire Landrace x Duroc castrated male and female pigs with a live weight of approximately 14.6 kg were used to study the effect of maize meal substitution by Jerusalem arti­ chokes 0, 33, 66 and 100% (on dry matter basis) in the ration for pigs aged from 61 to 96 days. The pigs were individually allocated to cages and distributed in a random block design with 4 treatments and 8 replications. Fresh Jerusalem artichokes were offered to the animals. Daily feed intake (kg DM/day), weight gain (g/day) and feed conversion (kg DM/kg gain) in increased maize substitution order were: 1.26, 1.22, 1.18 and 1.05; 483, 480, 403 and 283; 2.61, 2.54, 2.93 and 3.71. There were significant differences (P<0.01) between diets containing the highest maize substitution levels (66 and 100%) and the others, probably due to the bulking characteristics and digestion pattern of the tubers.


INTRODUCTION
Jerusalem artichoke {Helianthus tuberosus L.) tubers are frequently available in the field for pigs (Ruszczyc and Glaps, 1958;Cafias, 1990;Jost, 1992).Most of the experimental work done with the feeding of fresh (raw) Jerusalem artichokes to pigs has been with diets very low in tubers (Farnworth, 1994;Farnworth et al., 1995).In this connection Farnworth (1994) has suggested that young pigs con suming fresh tubers increased body weight gains, but decreased feed efficiency.Lynch (1991) observed a reduction in the growth rate in fattening pigs consuming 16% fresh tubers in the diet.

JERUSALEM ARTICHOKES FOR PIGS
The purpose of this investigation was to determine whether large amounts of raw Jerusalem artichokes could be safely incorporated into diets of young pigs, and the effects of such diets on pig performance.

MATERIAL AND METHODS
Thirty-two Yorkshire Landrace x Duroc, 61 day-old castrated male and female pigs with a liveweight of approximately 14.6 kg were used.The animals were allocated in individual cages (0.75 x 0.50 m) provided with appropriate feeding troughs in an open house.The pigs were divided in a random block design with 4 treatments, each on 8 pigs to study the effect of the substitution of maize meal for 35 days by raw Jerusalem artichokes (0, 33, 66 and 100% on dry matter basis in the ration) on pigs performance.
After harvesting, the Jerusalem artichokes were placed in air-tight plastic bags and stored chilled (2-4°C).Raw tubers were supplied to the pigs after the other ingredients of the ration were offered at 9:00 am, and were available throughout the day.The animals had water ad libitum from automatic water nipples.161.6 supplied per kg diet: 27 mg FeS04 • 7H20, 10 mg MnS04 • 4H20, 15 mg CuS04 • 5H20, 85 mg MgS04 • 7H20, 0.3 mg CoS04 • 7H2O,~0.1 mg KI, 0.02 mg Na2Se03, 1600 I.U.vitamin A, 300 I.U.vitamin D3, 2 mg thiamine, 2 mg riboflavine, 300 mg choline, 15 mg niacin, 5 mg pantothenic acid, 15 mg pyridoxine, 0.5 mg folic acid, 25 mg cyanocobalamine PILOTO J.L. ET AL.The standard analyses of the diets were performed according to AO AC (1990) whereas the NDF content was estimated by the Van Soest and Wine (1967) method.An adiabatic bomb calorimeter was used to estimate the energy value of feeds.Table 1 shows the characteristics of the experimental diets.
Data were analyzed using analysis of variance procedures according to Dun can's new multiple range test (Steel and Torrie, 1980).

RESULTS AND DISCUSSION
Table 2 shows the performance of pigs.Feed intake significantly decreased (P<0.05) with increasing levels of inclu sion of the tubers in the diets.This was probably due to the bulking characteristics of the Jerusalem artichokes, which in turn modify the pattern of feed intake (Ly et al., 1994) by increasing the time the animals spent eating and the rate of eating.Jost (1982) suggested that voluntary feed intake of raw tubers increases with the age of pigs.In this experiment, intake of raw tubers ranged from 1.35 to 3.46 kg/day, however, total replacement of maize by Jerusalem artichokes resulted in only a 16.7% reduction of DM intake.Weight gains of pigs were significantly affected (P<0.001) by lower energy intake levels in diets where maize was substituted by higher levels of Jerusalem artichokes; the introduction of 242 g of Jerusalem artichokes in the diet did not negatively influence daily gain.This result does not support the findings of Lynch (1991), who observed a growth reduction in animals fed 190 g raw tubers per kg DM.
A significant increase (P<0.01) in the feed conversion index with high levels of the tubers in the diet could be explained by experimental evidence of low digestion of Jerusalem artichokes in pigs (Ly et al., 1995).Accordingly, Farnworth JERUSALEM ARTICHOKES FOR PIGS (1994) reported that the daily gain in young pigs given low levels of raw Jerusa lem artichokes was satisfactory, but a deterioration of feed efficiency was evident.
Overall, the substitution of greater levels of the conventional energy source by Jerusalem artichokes in diets for pigs negatively affected the performance of young pigs.Nevertheless, there were no significant differences in feed intake, daily gain and feed efficiency of animals fed 242 g Jerusalem artichokes per kg of dry diet.These observations suggest that even in young pigs performance is not impaired by partial substitution of the energy source by Jerusalem artichokes rich in fructans.This could be related to the "sui generis" gastrointestinal activity of microorga nisms, which could supply substantial amounts of lactate rather than short chain fatty acids from fructans to the host (Graham and Aman, 1986), thus decreasing energy losses from fermentation.Moreover, a moderate concentration of fructans in the diet could increase the number of Bifidobacteria, which then might result in reduced diarrhoea (Farnworth, 1993) 483,480,403 i 283; 2,61; 2,54; 2,93 i 3,71.Stwierdzono istotna^roznicQ (P< 0,01) pomiedzy dawka mi, w ktorych bulwy zastaj)iono kukurydza^ w najwiejcszej ilosci (66 i 100%) a pozostaiym, co prawdopodobnie spowodowane bylo objetoscia^ i stopniem trawienia bulwy.