The effect of dietary levels of yellow lupin seeds {Lupinus luteus L.) on feed preferences and growth performance of young pigs

Feed preference (Experiment I) and growth performance tests (Experiment II) were carried out on growing pigs fed on diets differing in yellow lupin levels. In Experiment I , dietary choices were determined using the single stimulus method on 12 individually kept young pigs. In Experiment I I , basic growth parameters were studied in 36 young pigs. Three diets were used: control (1), with soyabean meal (SBM) as the only high-protein component, and experimental diets in which lupin protein substituted for 75 (diet 2) or 100% (diet 3) of SBM protein. The lupin content in diets 2 and 3 was 19 and 25%, respectively. During a 28-day feed preference test, daily intake of the three diets amounted to 760, 736 and 700 g, respectively; the differences are statistically significant. The average daily weight gains and feed intake were similar, while the best feed conversion ratio was in pigs fed on the diet with 19% yellow lupin seed meal.


INTRODUCTION
The use of leguminous plant seeds in the diets for monogastric animals is restricted due to the antinutritional factors contained in these seeds.Alkaloids are considered the most important factors in lupin seeds.This is one of the reasons why the optimum content of lupin in the diets for pigs, and especially for young piglets, has never been established in an unequivocal way.Low-alkaloid sweet lupin varieties have been produced to eliminate the negative effects of these factors on animal health and performance and to make utilization of this highprotein feed in pig nutrition possible as a partial or even total substitute for soyabean meal (Kemm et al., 1987;Flis, 1993).
Some experiments showed that even a relatively high content of lupin seeds did not affect the performance of piglets and young growing pigs (37%, Pearson and Carr, 1976; 43%, Barnett and Batterham, 1981).Bohme (1988) found that supplementing the diet with up to 30% " Topaz" yellow lupin seeds had a positive effect on the performance of weaned pigs (10-25 kg).In the experiment carried out by Gdala et al. (1996) it was concluded that seeds of yellow and narrow-leaved lupin could be used at a level of up to 41% in diets without depressing growth performance as compared with a soyabean diet.On the other hand, the results of other experiments suggested that lupin seeds could be used in pig feeding at a much lower dietary level (King, 1981;Donovan et al., 1993;McNiven and Castell, 1995).
Many studies have shown the negative effects of alkaloid- (Godfrey et al., 1985;Kemm et al., 1987), high crude fibre- (McNiven and Castell, 1995), and low lysine- (Batterham et al., 1986b) contents of lupin seeds, but primarily, of their low methionine level (Eggum et al., 1993).Godfrey et al. (1985) recommended that the diets of pigs fed ad libitum should not contain more than 0.20 g/kg of alkaloids.These authors found that an increase of alkaloid levels from 0.12 to 0.52 g/kg resulted in a progressive decrease of daily weight gains and feed intake by piglets.An increase in the alkaloid level by 0.1 g/kg was accompanied by a decrease of daily gains by 47 g on average, and of feed intake by 0.12 kg/day.However, alkaloid composition and type are also very important.In the case of white-and narrow-leaved lupin, the main alkaloids are lupanine and sparteine, considered more detrimental than the less-toxic lupinine, which is the dominant alkaloid in yellow lupin (Hill, 1977;Ballester et al., 1980).This is why yellow lupin seeds are regarded as more suitable for pigs.
So far, however, there have been no studies on the effect of high lupin levels on the palatability of diets for young growing pigs or on feed preferences and performance of young pigs.
The objective of this study was to determine the suitability of diets containing high levels of meal from raw seeds of Polish sweet yellow lupin cv."Juno" for young pigs.Two criteria were used to evaluate the diets: 1. the results of the feed preference test (Experiment I) and 2. the growth performance test (Experiment II).

Experimental design
Feed preference test (Experiment I).Twelve young pigs (crosses of 9 Polish Landrace x 6 Polish Large White), aged 8 weeks, of initial body weight 22.5 kg, were selected based on sex, litter and liveweight (analogue method).Each was placed in a 0.7 x 1.2 m flat-deck cage (with slatted floor), in an experimental pig unit.The cages had automatic feeders and nipple watering containers.
The feed preference test lasted 28 days and was carried out using the single stimulus method of Aldinger and Fitzgerald (1966), used also in other experiments (e.g.Baidoo et al., 1986;Falkowski et al., 1998).Each day the animals had free access, successively for 4 h (from 8.00 to 20.00 h), to each of the three feeds.The sequence of feeds changed every day, so that the pigs could not get accustomed to a particular feed.Feed intake was controlled each day.The animals were weighed on days 1, 14 and 28 of the experiment.

Growth performance test (Experiment II).
Growth performance was evaluated during 28 days on 36 young pigs (crosses of 5 Polish Landrace x 8 Polish Large White) aged 8 weeks, of initial body weight 18.8 kg.They were allocated to the three groups according to the analogue method.Two animals (a male and a female) each were placed in a flat-deck cage (0.7 x 1.2 m).The animals were fed ad libitum on diets of the composition as in Experiment I. Pigs were weighed on days 1, 14 and 28, feed intake and animal health were controlled daily.

Statistical analysis
The data were analysed statistically with a one-way analysis of variance and the Duncan's test.The statistical programme SPSS (1995) was used.

RESULTS AND DISCUSSION
The chemical composition of the diets is presented in Table 1.The increase of raw fibre content in diets 2 and 3 was due to the relatively high content of CF in lupin seeds (16.52%).
The alkaloid content in lupin was 0.039% of DM (Table 2), which is lower than the acceptable level for sweet (low-alkaloid) lupin 0.05% DM, but higher than the level accepted in commercial seeds in the European Union (0.02% DM) and Australia (0.01% DM).
In the first period of Experiment I (days 1-14), the average feed intake did not differ significantly between the groups (Table 3), while in the second period it decreased as the lupin level increased.This tendency was maintained in the whole experiment, but only the diet with the highest lupin level was consumed at a significantly lower rate than the control one (760 g for the control diet, and 736 and 700 g for diets 2 and 3, respectively), which may be explained by the negative effect of lupin alkaloids on diet palatability.A similar experiment, performed on weaned piglets given diets in which narrow-leaved lupin "Emir" was used at a ABC -P< 0.01; ab -P< 0.05 level of 14% and replaced 50% of the soyabean protein, showed that there was no effect of lupin on palatability as compared with the control cereal-soyabean diet (Falkowski and Jablonowski, 1993).The pigs showed very good growth performance throughout the experiment, as reflected by high body weight gains averaging 902 g (918 and 886 g in the first and the second period of the experiment, respectively).In the previous feed preference tests it was also found that the pigs that were allowed to consume more than one feed tended to eat more and to grow faster than normally fed pigs (Baidoo et al., 1986;Falkowski et al., 1998).
In Experiment II, no statistically significant effect of the experimental diets on pig body weight and growth rate was found, but the highest body weight on days 14 and 28 was observed in group 2 fed diets containing 19% of lupin seeds (Table 4).
Average daily feed intake per animal (Table 4) in the first period of the experiment did not differ between groups, ranging from 1.19 kg in group 1 to 1.23 kg in group 3. Similar tendencies were observed in the second period.In the experiment of Bohme (1988), yellow lupin "Topaz" at the level of 30%> increased feed intake of weaned piglets up to 7%.The addition of 25.4%> of white lupin "Ultra" to the diet for growing pigs significantly increased feed intake in the experiment carried out by Batterham (1979), while Kemm et al. (1987) found that when the diets for early weaned pigs were supplemented with 12% of white lupin "Buttercup" seeds containing 0.05% of alkaloids, feed intake decreased by 21%.
In the whole period of the experiment, daily weight gains were 676, 706 and 693 g in the three groups respectively, being a little higher in the experimental groups than in the control (Table 4).Daily weight gains obtained in our experiment were similar to those observed by King (1981) (622-693 g) and Donovan et al. (1993) (610-750 g), but slightly lower than those presented by Godfrey et al. (1985) (776-817 g).Lower daily gains (510-528 g) were obtained by Bohme (1988)  in an experiment with diets containing yellow lupin and by Gdala et al. (1996) (391-416 g), when the inclusion level of lupin seed meal (white, yellow or narrowleaf) in barley-based diets for young pigs ranged from 31 to 41%.The feed conversion ratio differed significantly between the experimental groups, both in the first and the second period (Table 4).The animals in group 2 on the diet containing 19% of yellow "Juno" lupin seeds utilized the feed better than the other animals (2.17 kg/kg of body weight gain for the whole period of the experiment).Similar results were presented by Batterham et al. (1986a) (1.98-2.53kg/kg BW), while a better feed conversion ratio was obtained by Gdala et al. (1996) (1.65-1.78kg/kg) and Bohme (1988) (1.50-1.57kg/kg).King's suggestion (1981) that increasing levels of lupin in the diet significantly reduced growth performance and increased feed conversion ratio has not been confirmed.
The relatively high content of alkaloids in the diet did not have a negative effect on growth performance of the pigs, but was probably the reason for worse feed utilization in pigs on the diet with the high lupin seed content (25%), which replaced 100% of soyabean meal proteins (Table 4).

CONCLUSIONS
Increasing the content of yellow lupin seeds from 0 to 19 and 25% in the diets negatively affected the feed preferences of young growing pigs.However, the average growth rate and daily feed intake during the growth performance test were similar and the feed conversion ratio was the best on the diet containing 19% of yellow lupin seed meal.
Yellow lupin seeds may be used as a partial substitute of soyabean meal for young pigs fed on diets supplemented with lysine and methionine.

TABLE 1
Composition and nutritive value of diets for young pigs(Experiments I and II)

TABLE 2
Chemical composition of yellow lupin seed cv.Juno

TABLE 3
Average daily intake of diets per pig, g (Experiment 1)