How Nutritional and Genetic Factors affect New Zealand Goat Milk Composition

Abstract

Demand for goat milk produced in New Zealand (NZ) is rapidly growing, particularly in expanding Asian markets. The aim of this study was to investigate how genetic and nutritional factors influence milk composition of NZ dairy goats. Little is known about these two factors in dairy goats, especially when compared to extensive research conducted in the area on dairy cows. Therefore in an attempt to improve goat milk production and composition, one important gene and three common nutritional supplements were investigated as part of this study.

The gene CSN1S1 was chosen for genetic analysis as it is highly polymorphic and can produce a range of effects on milk composition. 126 dairy goats were genotyped and 100 of these were aligned to herd-test and fatty acid data. Key findings include (a) ‘medium’ and ‘low’ CSN1S1 variants are the most common in the NZ dairy goat population, (b) CSN1S1 genotype significantly influences milk protein content, (c) in some circumstances CSN1S1 genotype can affect milk yield and fat content (d) CSN1S1 genotype has no effect on somatic cell count or the kilograms yielded of fat and protein or milk solids and (e) CSN1S1 genotypes produce small differences in two fatty acids (C10:0 and C18:3n3). Due to their increasing popularity as alternative animal feeds, palm kernel extract (PKE), biscuit waste (BW) and yeast nutritional factors were investigated. PKE significantly increased C12:0 and C14:0 fatty acids which were reduced to control-farm levels following removal of the supplement in the next season. BW had no clear effects on milk fatty acid composition while yeast supplementation had no effect on any aspect of milk composition. Significant seasonal effects were observed for some fatty acids.

Overall this research has shown that milk produced from NZ dairy goats has the potential to be modified through genetic and dietary means. Genetic factors such as CSN1S1 and nutritional supplements, especially PKE can alter milk composition. The healthfulness of goat milk can therefore be optimised to better suit the nutritional needs of the consumer.