High Quality Rapeseed Products as Feed for Sensitive Monogastrics

Research output: Book/ReportPh.D. thesisResearch

  • Heidi Blok Frandsen
The Danish pig production is among the world biggest and in 2010 the slaughtering reached 20.2 milion pigs, while 7.5 milion piglets and 0.9 milion finisher pigs and sows were exported, moreover 90% of the produced meat is exported. The main cost of pork production is the feed, and in the search for cheaper protein rapeseed meal has been considered as an alternative to soya-protein.
Rapeseed (Brassica napus L. spp. oleifera) has a well-balanced amino acid profile for monogastrics, but it contains several compounds which are anti-nutritional and might lower the protein quality and limit the amount of addition to feed for monogastrics. These compounds are constituted by glucosinolates, dietary fibers (DFs) and phenolics. In this project the main focus has been related to the glucosinolates and their transformation products in relation to product quality and biologic effects. Glucosinolates are present in plants of the order Brassicales (former known as Capparales), which include rapeseed, rype (Brassica campestris L.) Indian mustard (Brassica juncea L.), broccoli (Brassica oleracea L.var. italica) and many other plants. Glucosinolates have been studied widely for their biologic effects ranging from health promoting, anti-carcinogenic to being anti-nutritional or toxic. In relation to rapeseed the effects from glucosinolates are mainly associated with negative effects, and addition of rapeseed meal is considered safe for monogastrics when the glucosinolate level is below 1-2 µmol/g feed. Glucosinolates can be transformed enzymatic by the enzyme myrosinase (EC., or non-enzymatic by heat treatment or under the acidic and reducing conditions in the stomach of monogastrics. The type of transformation product depends on the parent glucosinolate and of the chemical conditions, and in some cases the transformation products seems to be more toxic than the intact glucosinolates. The presence of dietary fibers and phenols may lower the protein utilization by binding to proteins, and the effects are more pronounced upon heat treatment which is also correlated with a decrease in palatability due to oxidation reactions.
The introduction of present thesis describes the different compounds from rapeseed which are associated with anti-nutritional or biologic effects in animals (or humans), their presence, the structure and analytical determination and the different techniques for evaluation of protein digestibility are also discussed.
In the first study (manuscript I) the rapeseed quality has been investigated in relation to rapeseed varieties, applied conditions during oil-pressing and effects of pelleting. The glucosinolate profile and concentration were followed during the different processing steps, and the degradation of glucosinolates from warm-pressing was diminished from 37% to 17% by adjusting processing conditions, while cold-pressing only resulted in a glucosinolate loss of 6%. The pelleting of the final feed led to glucosinolate losses from 12% - 62% when warm-pressed rapeseed cake was included, while losses up to 88% were observed when cold-pressed rapeseed caked was used. N-balance trials with rats clearly demonstrated effects on the biologic value caused by high glucosinolate concentrations, active myrosinase and long temperature treatments.
The second study (manuscript II) is a continuation of paper I, where the different types of rapeseed products have been used in a pig study. These products were added to feed usedto piglets (7-30kg) for 50 days, and from each treatment 6 pigs were slaughtered at 30 kg weight for measurement of organ weights and collection of samples for further analyses. Enlargement of liver and kidneys were observed in all pigs served diets which contained rapeseed, and there was a tendency to increased thyroid gland in pigs served rapeseed that had been treated with extra temperature. Pigs served Lioness rapeseed had a reduced feed intake, independent of processing conditions, while pigs served Excalibur had similar performance to the control group. A high glucosinolate loss was observed in digesta from stomach and small intestine corresponding to a high conversion or uptake, but minor amounts of intact progoitrin and gluconapin were detected in urine samples. The measured level of iodide in the thyroid gland indicated possible long term effects on the thyroid metabolism from feeding overheated rapeseed products.
The third study (manuscript III) deals with the fate of intact glucosinolates in the digestive system and comprises in vitro and in vivo studies. The possible non-enzymatic transformation reactions of glucosinolates were investigated with standard compounds by use of capillary electrophoresis, and then standard glucosinolates were also incubated in pig stomachs. Finally feeding experiments were performed with standard intact glucosinolates in rats and pigs. In vitro and in vivo experiments revealed that up to 80 % of the glucosinolates in double low rapeseed can potentially be transformed into nitriles or thionamides in the stomach. In vitro studies revealed that 2-hydroxy substituted glucosinolates also is transformed into thionamides and not just into nitriles as the other aliphatic and phenyl glucosinolates. Furthermore it was found, that intact glucosinolates are absorbed over the small intestine and excreted in the urine. Analyses of blood from the hepatic vein showed that sinalbin was conjugated to glucuronid by xenobiotica enzymes in the liver.
The last study (manuscript IV) deals with the novel processing techniques, pulsed electric field (PEF) and high pressure treatment (HPT) and the processing effects on glucosinolates in broccoli. The largest effects were observed to be a result of the different handling of the plant materials prior to the process treatment. It was thus found that a great amount of the glucosinolate loss has occurred in the broccoli juice and purée prior to PEF processing. Only a minor loss was observed in broccoli flowers prior to processing, and HP treatment at 700 MPa for 10 min. was found to be optimal for inactivation of myrosinase.
Original languageEnglish
PublisherDepartment of Food Science, Faculty of Science, University of Copenhagen
Publication statusPublished - 2014

ID: 123993819