Aim of the Study

1. Influence of sex and immunocastration on feed intake behavior, skatole and indole formation in pigs • U.Weiler1, R. Wesoly1, A. Schmidt2, M. Otto3and S. Müller4 • 1: Fachgebiet Verhaltensphysiologie landwirtschaftlicher Nutztiere, Universität Hohenheim, Garbenstraße 17, 70599 Stuttgart, Germany • 2: Thüringer Lehr-, Prüf- und Versuchsgut GmbH, Am Feldschlößchen 9, 99439 Buttelstedt, Germany • 3: Mitteldeutsche Schlachtschweineerzeugergemeinschaft w.V., Remsaer Str. 17-19, 04600 Altenburg, Germany • 4: Abteilung Tierproduktion, Thüringer Landesanstalt für Landwirtschaft, August-Bebel-Straße 2, 36433 Bad Salzungen, Germany Aim of the Study Sex specific feed intake behavior was monitored during the fattening period and consequences for the formation of skatole and indole were studied in boars, barrows, immunocastrates and gilts. Results Data on growth performance and feed intake as well as androstenone, skatole and indole concentrations are given in Table 1. Feed intake/day increased with age due an increase in both, the duration of each meal and the feed intake rate (g/min). This was associated with a 50% reduction in the number of meals/day (see Fig. 1). The time, the animal spent feeding per day changed only moderately with age and revealed a diurnal pattern in all groups (Fig. 2) Methods 36 gilts, 32 immunocastrates (Improvac), 33 barrows (surgically castrated) and 33 boars were studied. Animals were kept in groups 12 pigs of the same sex and treatment with ad libitum feeding (13.4 MJ ME, 17% CP, 1.1% lysine) and continuous recording of individual feed intake behavior by an electronic feeder. Androstenone, skatole and indole were measured in adipose tissue after slaughter (1,2). Table 1: Growth parameter, feedintakeand skatole, indole and androstenone concentrationsforeachsexandtreatmentgroup (means, SEM) Different superscripts indicate significant differences p<0.05 by post hoc Tukey test Sex and treatment influenced feed intake behavior (Fig. 1): The low feed intake in boars resulted from a reduction in the number of meals/day and the time spent feeding/day. In giltstime spent feeding/day was quite similar to boars, but resulted from a higher number of meals of shorter duration. Barrows had a significantly higher feed intake due to a higher number of meals/day resulting in more time spent feeding/day. The feed intake rate was similar in boars, gilts and barrows. Immunocastration affected feed intake behavior severely, especially the meal size increased dramatically due to higher feed intake rate, which exceeded that of all other groups by 25% at the end of the study. The number of meals per day was not influenced by immunocastration. In gilts and barrows skatole concentrations were significantly related to growth rate (Tab. 2).Additionally the feed intake rate was an important factor explaining the variability in skatole/ indole formation in gilts and barrows, whereas in boars the time spent feeding/day was inversely related to indole concentrations. The physiological mechanisms, however, need further clarification. Fig. 1: Feed intake (kg/d), numberofmeals/dayandfeedintake rate (g/min) duringthefatteningperiod (mean ± SD) Table 2: Pearson correlationsbetween skatole/indole andfoodintakebehaviouranddailygainwithineachgroup 10 weeks Fig. 2: Diurnal patternsoffeedintake in 10 wkand 24 wkoldpigs References: 1: Dehnhardt, M. , Claus, R., Hillenbrandt, M., Herzog, A. (1993) High-performance liquid chromatographicmethodfordeterminationof 3-methylindole (skatole) and indole in adiposetissueofpigs J. Chromatogr. 616: 205-209 ; 2: Claus, R., Mahler, G., Münster, E. (1988) Determination oftheboartaintsteroid 5α-androst-16-en-3-one in adiposetissuewith a rapid microtitreplateenzym-immunoassay (MTE). Arch. Lebensmittelhyg. 89: 87-90