Protein is an important component in various milk products and has a crucial role in the final quality. Excluding non-protein nitrogen, bovine milk contains about 3.3% protein whereas about 80% of this fraction consists of Casein. There are four major members in the Casein family: ?s1-Casein, ?s2- Casein, ?-Casein and ?-Casein. Proteolytic enzymes are the cause of degradation of the economically important milk proteins.

Bovine milk is an excellent source of bioactive peptides. The bioactive peptides are in an inactive state in the protein and are released during enzymatic activity, e.g. during cheese ripening. Specific properties of bioactive peptides from ripened cheese has been reported, e.g. antihypertensive, antioxidative, antimicrobial, immunomodulatory and mineral binding.

The Swedish Red Polled breed is threatened by extinction and there are only around 1100 animals left. The breed was popular in the early twentieth century, but since then the numbers have steadily decreased. The overall objective of this study was to find out whether there may be economic incentives for preserving the breed. The milk quality properties are of major importance in the production of dairy products. Therefore we would like to establish if the Swedish Red Polled breed carries favourable alleles at loci of relevance for milk quality, to potentially make the breed more interesting for milk production.

Swedish goats are mainly held for cheese production and therefore, both milk quality and composition are of great importance for dairymen. Today, only few data exists on milk composition from Swedish dairy goats and the Casein content is still unknown. One way to reduce the work load for goat farmers and increase animal welfare can be to keep goats and kids together for longer periods. The aims of this study were to investigate how milk yield and composition were affected when kids suckled their dams during 8 weeks, and to measure the Casein content on farm level by a mid-infrared spectroscopy method, previously calibrated for goat milk. Lactating goats were kept in two different MIX- systems where the dams are both suckled and milked.

Today the milk production per cow is increasing but the milk delivered by the Swedish farmer contains less amounts of fat and protein than earlier. The contents have decreased since 1993. In average the milk contain 4,2 percent fat and 3,4 percent protein. Earlier the fat content in milk was important. Nowadays the dairy?s attention has turned to the milk?s valuable proteins, principally the Caseins, which have a considerable nutritional value and are important for several dairy products like cheese and yoghurt.

Mastitis, an inflammation of the udder mainly caused by a bacterial infection, induces an increase in the somatic cell count (SCC) in milk and is consequently one of several factors affecting SCC in milk. In this literature review it is investigated whether SCC; on udder quarter, cow composite or bulk tank milk level, can be used as a quality marker with focus on milk composition in terms of the content of fat, lactose, total protein, Casein and whey protein. According to this literature review the relation between SCC and milk composition is not reliable either on udder quarter, cow composite or bulk tank milk level. SCC was related to lactose, Casein and whey protein on udder quarter level; lactose and whey protein on cow composite level and lactose on bulk tank milk level.

Concentration of protein in bovine milk is one of the most significant milk quality parameters, to a large extent determining the price for milk to the producer. Mastitis is a common disease among dairy cows, negatively affecting not only milk yield but also milk protein composition. Milk from mastitic cows tends to have lower cheese yield, negatively affected processability properties and sensory quality, due to changed protein quality and composition. Poorer milk protein quality would have an economically negative impact on dairy industry. Only few studies have investigated the short term effects of mastitis on milk protein composition.

In Sweden regulations stipulates that dairy cows are kept on pasture, or given the opportunity to spend time outside during a coherent period of between two to four months, depending on region. The transition out to pasture is a big change from the winter period in the stable, especially for the modern high yielding dairy cows. The let out to pasture includes a change in feed, environment, and new routines. There are indications that the milk somatic cell count (SCC) rises in a peak shortly after the let out. The purpose of this study was to see if peaks in the SCC could be observed after the let out, and to study the contribution of inflammatory cells (neutrophils) and if the milk composition are affected. The study included 35 cows that were kept in stable during the winter.

In modern dairy production the milking frequency is increased in some herds due to introducing of automatic milking systems or the farmers decision to milk high producing dairy cows more than two times a day. With more frequent milkings the milk yield increases while the content of fat and protein decreases. However, how the composition of protein is influenced is not fully evaluated. The purpose of this study was therefore to see if a higher milking frequency had any impact on the milk production and especially on the protein composition. This study was conducted as a half udder experiment.

The aim of this study was to investigate if the botanical composition of haylage affects pH, dry matter content and microbial composition of the faeces in horse and pig and ileal environment in pigs. Two separate studies were conducted where pigs and horses were fed two diets containing haylages with different botanical composition. The first haylage was from a tilled land dominated by timothy and meadow fescue and the other haylage came from a meadowland with a large inclusion of dandelion, 25 % and common couch. The dry matter content (70.8 % and 73.0 % respectively) and the pH-value (5.7) were similar in both feeds. The first study was made as a three-periods switch-back study with 7 Standardbred horses. In the first and the third period, 7 and 9 days long respectively, the diet consisted of the haylage from the tilled land, oats, sugar beet pulp, soy bean oil meal, lucerne pellets and brewers yeast.

The different characteristics of many food products, such as aroma and texture, changes during storage time and become undesirable. The reason is instabilities within the product which become prominent as the product ages. These changes in characteristics are quality losses caused by changes in the product?s intrinsic and extrinsic environment. The stability in UHT-milk and beverages similar to it have been studied in the past decades and a certain focus have been on age gelation which is a common defect in these type of products.

SAMMANFATTNINGMastit är den vanligaste och mest kostsamma sjukdomen hos mjölkkor. Enligt statistik från Svensk Mjölk har cirka 65 % av alla kor i Sverige mastit någon gång under en laktation. Subklinisk (utan märkbara symtom) mastit utgör det största problemet. De är svåra att upptäcka då även mjölken ser normal ut, vilket resulterar i att den hamnar i tanken och levereras till mejeriet. Mjölk från kor med mastit har ett ökat celltal samt försämrad kvalitet och sammansättning vilket i slutändan medför sämre betalt för lantbrukaren.