| Popis: |
Milk with high concentrations of fat, total protein and casein is required for cheese production. The Swedish landrace goat produces milk with relatively low dry matter content. The explanation for this may be genetic factors in combination with unfavourable management and milking routines. Goats have a large udder cistern and can therefore be milked without oxytocin (OT) stimulated milk ejection that enables fat rich alveolar milk to be available for milking. Earlier studies have shown that vasopressin (AVP) also can increase fat content in goat milk. The overall aim in this thesis was to investigate if cheese processing properties of Swedish goat milk could be optimized by suckling. Analyses of milk from 28 Swedish goat herds showed that 65% had low concentrations of αS1-casein and only 12 % had high expression (Paper I). In Paper II it was demonstrated that AVP and OT increase simultaneously during suckling but not during hand milking. The importance of AVP was followed up in paper III, and it was demonstrated that AVP administration can cause milk ejection similarly to OT. In paper IV it was found that milking management systems, such as suckling before milking, increased milk fat concentration compared to milking before suckling. When dams and kids were together for a longer time (16h) milk fat, casein concentration and individual curd yield (%) were higher compared to when they were together for shorter time (8h). Thus overall, keeping goats and kids together is beneficial for animal welfare, increases milk fat concentration and curd yield, and can thereby improve cheese production. |
