Feeding with lupines reduces the amount of skatole in organic pigs
By Laurits Lydehøj Hansen, Danish Institute of Agricultural Sciences, Dept. of Food Sciences, Research Centre Foulum and Chris Claudi-Magnussen, Danish Meat Research Institute, Roskilde
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In organic pig production, lupines could be an alternative source of proteins instead of soya bean meal, which is prohibited. Concurrently, the normal protein level (100%) is too high in digestible raw protein, as essential amino acids are prohibited in the production of organic food products.
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In the present study, we tested the effect of lupines (0 and 25%) and the level of proteins (85% and 100%) in the diet for growth-finishing pigs. One of the interesting questions was whether the lupines with the rather high content of oligosaccharides could decrease the skatole concentration in backfat of castrated male and female pigs as seen in blood plasma in an earlier experiment with entire male pigs (Jensen and Jensen, 1998). Thus, a reduced skatole content in the backfat would be beneficial for the eating quality of the meat. Another question was whether the skatole concentration was unaffected by protein level as seen in an earlier experiment (Mortensen et al., 1989; Mortensen, 1990).
Experimental treatments
The presented experiment consists of four treatments: two levels of protein (low 85% vs. normal 100%) times two levels of lupines (0% and 25%). The study was carried out one summer and one winter season, each involving two pen replicates of five pigs (one pen with 5 female pigs and one pen with 5 castrated male pigs per treatment). The feed compositions of the four treatments are seen in Table 1.
The pigs were distributed to the four treatments according to litter, sex and initial weight. Twenty pigs have completed all four treatments, 80 pigs in total (see Table 2).
After slaughter, a backfat sample of the pigs was collected and analysed for skatole equivalents using the colorimetric method described by Mortensen (1983) and Mortensen and Sørensen (1984). Other variables analysed were: live weight at slaughter, warm carcass weight, percentage of lean meat, drip loss, pH24 in musculus longissimus dorsi (M. long. dorsi), temperature 24h in M. long. dorsi and skatole in backfat.
Statistical analysis
Data were analysed using the Mixed Models Procedure of Statistical Analysis Systems Institute (SAS Inst. Inc., Cary, NC) by means of models including the fixed effects of protein level (low 85% and normal 100%) and percentage of lupine (0% and 25%), sex, season and interactions between the fixed effects. Details of the model are presented elsewhere.
No differences were found between treatments in the case of the following variables: drip loss, pH24h in M. long. dorsi and temperature 24h in M. long. dorsi (data not shown). Likewise, there was no significant difference in live weight at slaughter between treatments (Table 2). Yet, there was a tendency to lower warm carcass weight in treatment 4 (data not shown).
Lupines increase lean meat
The pigs fed 25% lupine (Treatment 2 and 4) had significantly higher percent lean meat than the control treatments (Treatment 1 and 3) as shown in Table 2 (P<0.05). Also, as shown in Table 2, there was a highly significant difference between castrates and female pigs (P<0.001).
Lupines decrease skatole in backfat
The pigs fed 25% lupines had significantly lower skatole concentrations in backfat compared with the control treatments without lupines (P<0.001), and there was no difference in skatole concentration between the two protein levels (Table 2). Both results were in agreement with earlier results (Jensen and Jensen, 1998; Mortensen, 1990; Mortensen et al., 1989). As expected no differences were observed in skatole concentration between the castrated male pigs and female pigs (Hansen et al., 1995; Mortensen, 1990; Mortensen et al., 1989).
As there was no tendency to interaction between protein levels and the levels of lupines, the 25% lupines may be expected to have a very significant effect on skatole content in backfat irrespective of the other food components. This might be an important result, as the organic pig producers will probably be the first to be forced by legislation to produce entire male pigs due to welfare concerns about castrating the male pigs. Naturally, this result has to be confirmed in an experiment with entire male pigs. However, it is expected that also in entire male pigs fed with lupine, the skatole level could be decreased by 50 percent, thereby reducing the number of entire male pigs with boar taint.
Reference List
Hansen, L. L., A. E. Larsen, and M. J. Hansen. 1995. Influence of keeping pigs heavily fouled with faeces plus urine on skatole and indole concentration (boar taint) in subcutaneous fat. Acta Agriculturae Scandinavica 45:178-185.
Jensen, B. B. and M. T. Jensen. 1998. Microbial production of skatole in the digestive tract of entire male pigs. (Chapter 3) In: W. Klinth Jensen. (Editor) Skatole and boar taint. ISBN 87-985837-1-9. Danish Meat Research Institute, Roskilde, Denmark, 41-75. In.
Mortensen, A. B. 1983. A method of detecting obnoxious taint such as boar taint in individual animal bodies, preferably carcasses or parts thereof. PCT International Patent Application , International. Ref Type: Patent.
Mortensen, A.B. and Sørensen, S.E. 1984. Relationship between boar taint and skatole determined with a new analysis method. Proceedings of the thirtieth European meeting of meat research workers, Bristol, pp. 394-396.
Mortensen, H. P. 1990. The influence of breed, energy and protein in the feed on skatole content in female pigs, castrates and entire male pigs. Proceedings EAAP-working group, Spain 1989. Livest. Prod. Sci. 26:319-326.
Mortensen, H. P., C. Bejerholm, P. Barton, and O. K. Pedersen. 1989. Indflydelsen af foderets protein- og energiindhold på kød- og spækkvaliteten hos han-, galt- og sogrise. Report no. 38.124 Slagteriernes Forskningsinstitut, Roskilde. 1989.
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