ABSTRACT

In sow feeding fat of rapeseed or that of high-fat rapeseed press cake (RPC) may stabilize piglets counteracting possible negative glucosinolate effects. Ground rapeseed (RS), 21.4 mmol glucosinolates/kg dry matter (DM) or RPC, 188 g fat/kg DM, 31.5 mmol glucosinolates/kg DM, were evaluated in two experiments with 36 highly pregnant and lactating sows (3 groups á 12 animals, Exp.I) and 45 sows (3 groups á 15 animals, Exp. II), resp. A grain diet contained no rape feedstuffs (Group 1 = control). In Exp. I 40 g rape oil/kg feed (Group 2) or 100 g RS /kg feed (Group 3) and in Exp. II RPC, 75 g/kg feed (Group 2) or 150 g/kg feed (Group 3) were used. The RPC diminished feed intake and rearing parameters. The decrease was significant in the group with the highest cake content (4.2 mmol glucosinolates/kg feed). Ground rapeseed (100 g = 1.9 mmol glucosinolates/kg feed) or rape oil had no effect on rearing parameters. Both RS and RPC lowered the iodine concentration of sow milk and piglet serum. Rapeseed and rapeseed oil increased oleic, linoleic and linolenic acid content (as fatty acid methyl esters) of milk and decreased its myristic, palmitic and palmitoleic acid content. Sows synthesize the biggest part of saturated and monounsaturated milk fat fatty acids de novo or these fatty acids have their origin in fat depots.In relation to consumed essential fatty acids two third linoleic acid and half of linolenic acid appear in milk fat. Sow diets containing rapeseed feeds should contain no more than 2 mmol glucosinolates/kg. At least 1000 µg iodine/kg diet should be added to these diets, i.e. about the double German or British recommended levels.

Rapeseed and its products from a total or partial deoiling represent risky feed now as before, particularly for the breeding sow. In earlier experiments, sow diets with high glucosinolate rapeseed meal, solvent extracted, caused piglet losses strengthened by thyroid hormone deficiency (Schöne et al. 1986) due to a lack of dietary iodine (Devilat and Skocni 1971). The supplementation of iodine counteracts some negative effects.

However, poor performance and animal-health problems still occurred even when rapeseed meals with a reduced glucosinolate content were fed (Etienne and Dourmad 1994). Contrasting with the solvent extracted rapeseed meal, practically free of fat, rapeseed (RS) and rapeseed- press cake (RPC) with their high fat content offer the possibility to increase the fat content of sow milk and to stabilize the piglet growth as indicated by the positive results from application of fat to the sows (Drochner 1989).

In both the experiments reported here, the first one with RS, the second one with RPC, the rearing results were evaluated with respect to dietary glucosinolate content. The objective of the experiments was to obtain information on glucosinolate tolerance, the iodine status of breeding sows, and on the effect of rapeseed-fat diets on sow-milk composition.

MATERIAL AND METHODS

Experiment I was carried out with 3 groups of 12 sows each and Experiment II with 3 groups of 15 sows each (German Landrace x Large White). The experiments lasted from late pregnancy to the end of the 28th day of lactation. The control diet consisted of grain and soya-bean meal and contained no rape products (Group 1 = control). In Experiment I 40 g rape oil/kg feed (Group 2) or 100 g RS/kg feed (Group 3)were fed, in Experiment II RPC, 75 g/kg feed (Group 2) or 150 g/kg feed (Group 3) were used. During lactation, different subgroups of sows received different rates of iodine which was reported by Schöne et al. 1998b. Iodine was determined by intracoupled plasma mass spectrometry = ICP-MS (ELAN 6000, Perkin Elmer) in blood serum and milk samples taken on the 27th day post partum. Also in these milk samples (30 ml taken after oxytocin injection) protein, fat, lactose were determined and the fatty acid methyl esters were analysed by capillary chromatography (Schöne et al. 1998a). Data were analysed by ANOVA and by the Newman Keuls test with the SAS software package (SAS 6.11, SAS Institute Heidelberg, Germany. In the tables, the arithmetic mean and the standard deviation (SD) are given.

RESULTS AND DISCUSSION

The RS contained 21.4, and the RPC 31.5 mmol glucosinolates/kg dry matter (DM). These concentrations analysed by standard method (EC 1990) were above the 18 mmol/kg RS (basis air dried matter = 910 g DM/kg) which is the upper limit of certification of a 00 rapeseed variety for sowing in Germany. In the EC the permissible content is higher: 25 mmol glucosinolates/kg air dried matter.

In Experiment I, no feeding effect on the number and weight of piglets could be detected (Schöne et al. 1998 a). Accordingly, the tested percentage of ground rapeseed (100 g = 1.9 mmol glucosinolates/kg diet) did not affect the rearing results.

In Experiment II, inclusion of RPC into sow diets diminished feed intake and rearing parameters (Table 1). The decrease of the sow-feed intake and of the number of weaned piglets was significant in the group with the highest content of 150 g RPC = 4.2 mmol glucosinolates/kg feed. In this group, the tendency of a lower piglets´ number per litter already at birth (Schöne et al. 1998a) strengthened through lactation by higher piglets´ losses resulting in the significantly diminished number of weaned piglets.

Table 1. Experiment II - Feed intake during lactation, body weight of sows and rearing results at weaning (15 litters/group, mean ± SD).

^a,b,cDifferent superscripts indicate significant differences at the 0.05 probability level.

The reduced feed intake and piglet performance due to the diet with 150 g/kg RPC (4.2 mmol glucosinolates/kg) agrees with findings of previous experiments with rape diets which contained from 3 to 10 mmol glucosinolates/kg (Etienne and Dourmad 1994, Schöne et al. 1997). From the results of Experiment I, for the lactating sow a threshold level of 2 mmol glucosinolates/kg diet seems to be low. This concerns a low applicable dietary rapeseed-feed inclusion level for a glucosinolate-rich 00 quality rapeseed with an upper limit of 40 mmol glucosinolates/kg defatted matter (910 g DM/kg) in recent EU seed certification (for sowing).

Both RS (Schöne et al. 1998b) and RPC (Table 2) lowered the iodine concentration of sow milk and piglet serum. Comparing the groups with 75 or 150 g RPC/kg diet a glucosinolate-dose effect could not be detected.

Tabelle 2: Iodine concentration of sow serum, milk and piglet serum, µg/kg, at the end of lactation in Experiment II (15 sows and 30 piglets/group, 2 piglets/litter, mean ± SD)

^abDifferent superscripts indicate significant differences at the 0.05 probability level.

In the sow serum, the iodine concentration was even increased. It can be assumed that the elder animals with their filled thyroid iodine store mobilize more iodine under a glucosinolate exposition. However, this iodine cannot be delivered to mammary gland what is indicated by the decreased milk iodine concentration.

Milk samples taken towards the end of the suckling period did not change after ground rapeseed or rape-oil application with regard to fat, protein and lactose content (Schöne et al. 1998a). In contrast, 150 g RPC/kg feed lowered protein concentration of milk.

Rape fat increased oleic, linoleic and linolenic acid percentage in the fatty acid pattern of fat of milk, thereby decreasing myristic, palmitic and palmitoleic acid (Table 3). In the case of lower intake of rape-cake diets or rape fat in Experiment II, changes of the fatty acid pattern were less pronounced (Schöne et al. 1998 a).

Table 3: Experiment I - Fatty acid composition¹⁾ of milk fat, % of detected fatty acid methyl esters (12 sows/group, mean ± SD)

^abc Different superscripts indicate significant differences at the 0.05 probability level.

¹⁾ Content of C4:0, C6:0, C8:0, C10:0, C14:1, C20:0, C20:1, C20:2 and C22:0 with <0,5 % is not given. Detection limit 0.1 %.

Figure: Experiment I - Input of fatty acids via feed and output via estimated 7 kg sow milk

This figure is to show the intake of fatty acids calculated from the intake of feed, fat and the analysed fatty acids of the feed and an output of fatty acids by estimated 7 kg milk. Sows synthesize the biggest part of milk-fat saturated and monounsaturated fatty acids de novo or these fatty acids have their origin in fat depots, resp. . In relation to consumed essential fatty acids, two third linoleic acid and half of linolenic acid appear in milk fat. A similar recovery in milkfat of linoleic acid and linolenic acid, three fourth each, was also estimated for essential fatty acids of rape-fat addition.

In the present investigation, 150 g/kg RPC = 4.2 mmol glucosinolates/kg feed diminished the feed intake of lactating sows and the number of reared piglets; 100 g ground rapeseed = 1.9 mmol glucosinolates/kg feed did not act negatively. The high rapeseed- fat diets (40 g/kg diet) caused a shift to oleic acid, linoleic acid and linolenic acid in the fatty acid pattern of sow milk diminishing its content of palmitic and palmitoleic acid.In relation to consumed essential fatty acids, two third linoleic acid and half of linolenic acid appear in milk fat. Sow diets containing rape-seed feeds are expected to contain no more than 2 mmol glucosinolates/kg. For the time being at least 1000 µg iodine/kg diet should be added to these diets, i.e. about the double German or British recommended levels.

ACKNOWLEDGEMENT

This investigation was supported by a grant from Association for the Promotion of Oil and Protein Plants (Union zur Förderung von Öl- und Proteinpflanzen = UFOP), Bonn, Germany.

REFERENCES

1. Devilat, J., A. Skokni (1971): Feeding high levels of rapeseed meal to pregnant gilts. Canadian Journal of Animal Science 51, 715 - 719.

2. Drochner, W. (1989): Einflüsse von Fettzulagen an Sauen auf Aufzuchtleistung und Fruchtbarkeit. Übersichten Tierernährung 17, 99 - 138.

3. European Community (1990) Oilseeds - determination of glucosinolates - high performance liquid chromatography. Official Journal of the European Community L 170: 27-34.

4. Etienne, M., J.Y. Dourmad, 1994: Effects of zearalenone or glucosinolates in the diet on reproduction in sows: A review. Livestock Production Science 40, 99 - 113.

5. Schöne, F., K. Hartung, G. Jahreis, T. Graf, F. Tischendorf (1998a): Prüfung fettreicher Rapsfuttermittel (Saat und Kuchen) an Zuchtsauen - Futteraufnahme, Aufzuchtergebnisse und Milch(fett)zusammensetzung [Evaluation of high fat rape feeds (seed and cake) on breeding sows - feed intake, rearing results and milk fat composition]. Journal of Animal Physiology and Animal Nutrition 79, 184 -197.

6. Schöne, F., G. Jahreis, H. Lüdke, B. Groppel, E. Kirchner, H.-D. Bock (1986): Hypothyreose bei Sauen und Ferkeln nach Fütterung einer Kartoffel-Rapsextraktionsschrotsilage [Hypothyroidism of sows and their piglets after feeding of silage made from potatoes and solvent extracted rapeseed meal]. Archiv für Experimentelle Veterinärmedizin, Leipzig 40, 507-519 .

7. Schöne, F., M. Leiterer, G. Jahreis (1998b): The effect of rapeseed and rapeseed press cake with different glucosinolate content on sows and their piglets. Proc. of the third international workshop on “Antinutritional factors in legume seeds and rapeseed” Wageningen, EAAP Publication No. 93, Wageningen pers. 213 - 216.

8. Schöne, F., M. Leiterer, G. Jahreis, B. Rudolph (1997) : Effect of rapeseed feedstuffs with different glucosinolate content and the iodine administration on the gestating and lactating sow. Journal of Veterinary Medicine A 44, 325 - 339.