Sturende factoren voor verhoging van vet- en eiwit gehalten in biologische melk : een eerste verkenning

anglais. The fat content in organic dairy goat's milk is significantly lower than milk of regular dairy goats. The difference in protein content between organic and regular goat farms is minimal. Statistical analysis shows that the fat content in the organic goat milk fluctuates more in relation to protein. To increase the level of fat and protein content in goat's milk, this report will show aspects regarding nutrition and genetics. Looking at the nutritional aspects of different fat and protein supplements and their effect on fat and protein content in goat's milk, a literature study into different supplements that are tested for their ability to increase the levels was executed. In addition, practical experiences of dairy goat farmers were collected and if possible supported by literature. The dietary ingredients that are dealt with are oils, seeds and beans and fats that bypass the rumen. One of the main conclusions is that almost all plant based dietary fats which are fed to the goats have an effect on the fat content in the milk, while the protein level remains mostly unchanged. These dietary fats seem promising. However, it is important that these fats are not used extensively. A level of fat that is too high will have a negative effect on the intake and digestibility in the rumen. Dietary fats with hay as basic feed will give better results than maize silage. An interaction between the species and the dietary fat seems obvious. It is interesting to think about possible effects of dietary fats in combination with various basic feeds. Experiments with seeds, beans and cakes have various results. Literature has shown that research is executed regarding whole seeds or oils. A recommendation is to investigate the influence of supplementation of 'intermediate forms' on fat and protein levels in goat milk, such as crushed and ground seeds. Most studies regarding rumen protected feeds lead to very positive results, because the nutrients are resistant against microbial degradation in the rumen. Because chemically protected feeds are not permitted in organic farming, one has to look for possibilities to make those feeds resistant in an organic manner. The solution seems to lie within the toasting of foods such as soybean, lupine and barley. Most experiments in this field have been done in dairy cattle and the results were promising. The effect of toasted feed in order to increase the milk composition of dairy goats needs attention. The literature shows that supplementation of crude protein has little or no effect on increasing protein levels in goat milk. Genetic progress can be achieved in organic goat when one breeds on fat and protein content. Looking at the different influences that genetics may have on the fat and protein contents of goat milk, it becomes clear that protein content in milk is determined by the casein genes. Through DNA research, the genetic potential of an animal can be proven. A high protein content has positive effects on fat content, but may have a negative impact on milk production. Also, the taste of goat cheese is influenced by a high protein content. The environmental factors of regular dairy goat farms differ from organic dairy goat farms. It is uncertain whether breeding bucks from the regular production system will have the same performance when used in organic dairy farms. Further research into genotype by environment interaction, in particular food and medication, may give more insight into the use of breeding goats from regular dairy goat farms in organic goat farming. Artificial insemination (AI) offers an opportunity for fresh and better genetic material to enter into the current herd. For AI, oestrus .......

néerlandais; flamand. In de biologische veehouderij worden geitenhouders beperkt in hun maatregelen om vet- en eiwitgehalten te verhogen, door de biologische regelgeving. Door deze maatregelen ligt het vetgehalte in de biologische geitenmelk significant lager dan in de gangbare geitenhouderij. Aangezien 80 % van de biologische geitenmelk wordt verwerkt tot kaas, is verhoging van het vet- en eiwitgehalte tevens gewenst. Biologische geitenhouders willen graag meer mogelijkheden hebben om de vet- en eiwitgehalten in de geitenmelk te verhogen. In dit onderzoek is vooral aandacht besteed aan de voeding en de genetica. In het eerste deel een probleeminventarisatie, in het tweede deel is er aandacht voor voeding, met daarin speciale aandacht voor eiwit en vet en in het laatste deel is er vooral aandacht voor de genetica van geiten en bokken