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Isolated $ alpha sb{ rm s1}$-casein, $ alpha sb{ rm s2}$-casein, $ beta$-casein, $ kappa$-casein of different phenotypes, whole casein of different phenotype combinations of $ alpha sb{ rm s1}$-/$ beta$-/$ kappa$-casein, and $ beta$-lactoglobulin of different phenotypes were prepared and used in the study. Surface properties at the air-water interface, voluminosity and hydration, emulsifying capacity and emulsion stability, foaming and gelling properties were investigated to understand the relationship between the structure and functionalities of milk proteins. Phenotype CC of $ alpha sb{ rm s1}$-casein, A$ sp1$A$ sp1$ and A$ sp1$A$ sp2$ of $ beta$-casein, AB of $ kappa$-casein decreased surface tension at a faster rate than the other, phenotypes within the casein system under consideration. $ beta$-Casein, when compared to $ alpha sb{ rm s1}$-casein, $ alpha sb{ rm s2}$-casein and $ kappa$-casein, was the most surface active protein. The $ alpha sb{ rm s1}$-/$ beta$-/$ kappa$-casein haplotypes of BB/A$ sp2$A$ sp2$/AA and BB/A$ sp1$A$ sp1$/BB were found to be associated with higher surface activity than the other ten combinations of whole casein. $ alpha sb{ rm s-1}$-Casein BB, $ beta$-casein A$ sp2$A$ sp2$ and $ kappa$-casein AB had higher values for voluminosity and hydration than the other phenotypes of the corresponding individual casein. Within the four caseins, $ beta$-casein had the strongest ability to entrap water and the highest value for voluminosity, followed by $ alpha sb{ rm s1}$-casein, $ alpha sb{ rm s2}$-casein and $ kappa$-casein. Whole casein with the combination of BB/A$ sp2$B/BB had the highest value for voluminosity and hydration. Analysis of model emulsions suggested that the emulsifying properties of different sources of protein were dependent on the oil content. $alpha sb{ rm s1}$-Casein BB in 10% oil emulsion, $ beta$-casein A$ sp2$A$ sp2$ in 10% and $ beta$-casein A$ sp2$B in 40% oil emulsions were the best stabilizers. $ kappa$-Casein

The properties of genetic variants of $ alpha sb{ rm s1}$-casein (BB, AB), $ beta$-casein (A$ sp1$A$ sp1$, A$ sp2$A$ sp2$, A$ sp1$A$ sp2$, A$ sp1$A$ sp3$, A$ sp2$A$ sp3$, A$ sp1$B, A$ sp2$B, BB), $ kappa$-cn (AA, AB, BB) and $ beta$-lactoglobulin (AA, AB, BB) were compared. The caseins and $ beta$-lactoglobulin were purified by mass ion exchange chomatography. Model systems of $ alpha sb{ rm s1}$- and $ kappa$-caseins were compared with respect to their stability towards calcium ions and other major milk salts precipitation. $ beta$-Casein, $ alpha sb{ rm s1}$-casein BB + $ beta$-caseins and $ kappa$-casein were also compared in their ability to resist calcium ion precipitation. $ kappa$-casein AB was a better stabilizer of $ alpha sb{ rm s1}$-casein than the BB and AA variants. $ alpha sb{ rm s1}$-Casein BB resisted calcium ion precipitation more than the AB variant in presence of $ alpha$-lactose, citrate, chloride and magnesium ions. $ kappa$-Casein BB stabilized $ alpha sb{ rm s1}$-casein AB more than the BB variant in presence of calcium and phosphate ions. Solubility of $ kappa$-casein AA, however, was greater than that of $ kappa$-cn BB and $ kappa$-cn AB variants in calcium and phosphate solutions. As in $ alpha sb{ rm s1}$-casein, significant differences were also found among $ kappa$-casein variants in stabilizing $ beta$-casein against calcium ion precipitation. $ beta$-Caseins A$ sp1$A$ sp1$, A$ sp2$A$ sp2$ and A$ sp1$B produced the most stable micelles while those of A$ sp2$B and B variants the least at 0.03-0.25 $ kappa$-cn/$ beta$-casein ratios and 20 mM Ca$ sp{2+}$. However, stability of micelles formed from $ alpha sb{ rm s1}$-cn + $ beta$-cn A$ sp2$A$ sp3$, $ alpha sb{ rm s1}$-cn + $ beta$-cn A$ sp1$A$ sp3$, and $ alpha sb{ rm s1}$-cn + $ beta$-cn A$ sp2$A$ sp2$ caseins were higher than those of $ alpha sb{ rm s1}$-cn + $ beta$-cn A$ sp1$A$ sp2$, $ alpha sb{ rm s1}$-cn + $ beta$-cn A$ sp1$B and $ alpha sb{ rm s1}$-cn + $ beta$-cn A$ sp1$A$ sp1$.

Milk, fat and protein first lactation records of 27,137 British Columbia Dairy Herd Improvement cows were analysed for gross genetic and environmental influences. The average production was 5,663 kg of milk containing 3.59% fat and 3.23% protein. Age at freshening accounted for 3.0, .3.7, 3.7, .0.28 and 0.15% of the variance in milk, fat, protein, percent fat and percent protein respectively. Cows freshening in the winter had higher average milk, fat and protein yields than those freshening in summer; however, the percentage constituents of both fat and protein were higher for the summer cows than for the winter cows. Heritability of each characteristic and the phenotypic and genetic correlations between different characteristics were derived from paternal half-sib analyses with 100 sire groups. Heritability values were: milk 0.18; fat 0.24; protein 0.21; % fat 0.38, and % protein 0.47. Within herd-year-season phenotypic correlations between milk yield and the percentages were both negative, whereas the correlation between the constituent percentages was positive. Genetic trends in the cow population averaged 51.5 kg, 2.77 kg, 1.87 kg, 0.015% and -0.049% for milk, fat and protein yields and fat and protein percentages respectively. The dollar returns from incorporating milk, fat and protein yields and/or the constituent fractions in various selection indices were estimated for different levels of protein payment. Higher dollar returns will be expected from selection based on total yields than from selection based on either fat or protein percentage. Measuring protein for a genetic program will be feasible only when unrealistically high prices are paid for protein. / Land and Food Systems, Faculty of / Graduate

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