The proteins found in milk are largely important in the functionality of many dairy products and dairy processes. The casein micelle system in milk is a complex and highly studied system. The micelle is thought to be a sponge like structure containing four caseins, αs1, αs2, β, and κ casein, and bound together with colloidal calcium phosphate. When a chelating agent such as a citrate, phosphate, or polyphosphate are added to milk systems, the CCP is bound to the chelator and removed from the micelle. It has been shown through past research that the use of calcium chelating agents disrupts the calcium phosphate equilibrium and allows for the dissociation of the casein micelle and release of the individual caseins. Once the caseins are disrupted from micellar form and in solution, it may be possible to separate out different casein streams for functional usage in dairy products using common separation techniques. This thesis project seeks to evaluate the feasibility of separating milk treated with calcium chelators using various separation techniques to evaluate the individual casein fractions of this disrupted system. Four separation methods (ultracentrifugation, membrane filtration, heat coagulation, and coagulation based on pH) were employed to separate out the caseins based on selected properties, specifically density, molecular weight, and solubility. In ultracentrifugation, three speeds were tested, the heat coagulation study tested two temperatures, and pH based coagulation tested four different pHs to determine their impact on overall protein levels and individual casein yields. Skim milk powder was reconstituted and chelator was added at 1, 50, or 100 mEq/L treatment level. These samples were then separated using aforementioned techniques, and the supernatant or permeate was analyzed for total protein content, individual casein composition, turbidity, and mean particle size. Analysis of centrifugal separation studies shows the interaction between chelator type, chelator level, and centrifugation speed had a significant impact on the amount of protein released from the casein micelle (p Coagulation trials based on pH were also shown to have a significant interaction between chelator type, chelator level, and sample pH effecting the protein levels and casein composition (p Membrane filtration showed low protein yields in permeate, however trisodium citrate 100 mEq was still shown to have significantly higher permeate % protein levels (p The use of heat based coagulation as an individual casein separation technique for chelated samples is not recommended, as the casein micelle system itself is extremely heat stable, and the use of calcium chelators only increases the heat stability further. Because of the increased heat stability, no coagulum was formed in samples upon heating, and therefore, no separation and analysis could be done. Improving our knowledge of pretreatment of milk prior to separation and the effectiveness of different separation methods on chelated milk products may result in information leading to the ability to separate out milk fractions that provide unique or improved properties for product applications.

Forty high producing early to mid lactation Holstein cows were blocked according to stage of lactation and previous two-week milk yield (experiment 1) . Eight ruminally and duodenally cannulated nonlactating Holstein cows were used for experiment 2. The objective was to determine the effects of the ration's high fat content (11.53%) when rumen degradable or rumen undegradable protein is fed with or without added niacin. Cows received one of five treatments: 1) basal ration (TMR); 2) basal ration with added rumen undegradable fat (RUF) (1.6 kg); soybean meal (SBM) (1.73 kg), and niacin (12 g); 3) same as treatment 2, without niacin; 4) same as treatment 2 but replacing the soybean meal with undegradable protein (UIP) (1.9 kg ) ; and 5) same as treatment 4, without niacin. Rations and water were offered ad-libitum for 10 weeks. Intake for experiment 2 was limited to 18 kg TMR, 0 .76 kg RUF, 0 .88 kg SBM or UIP, and 6 g niacin. All cows in experiment 2 received the five treatments by the end of five collection periods separated by 21 d adaption. RUF increased dry matter intake (22.95 vs. 23 . 72 kg/d ) and mean body weight (607 vs. 637 kg ) , but decreased milk protein, lactose and SNF (proportion and yield); and 4% FCM without affecting daily milk yield. RUF, SBM, and N did not affect milk production. Milk protein percentage, protein yield, lactose percentage, SNF percentage, and yield were decreased by UIP supplementation. Niacin had a negative effect on milk fat percentage and yield, and milk protein percentage when fed with RUF and UIP . Supplements did not affect milk protein components. RUF increased plasma glucose (56.8 vs. 63.5). RUF addition increased AD and ND digestibility while decreased fatty acid digestibility. UIP improved ND digestibility in the lactation trial. For experiment 2, UIP increased rumen propionate percentage, thus reducing acetate to propionate ratio. Niacin increased total VFA production (128.6 vs. 114.3 umol/ml) . RUF, UIP, and niacin increased total bacterial population. RUF reduced cellulolytic bacteria in rumen fluid. Nutrient rate of passage and digestibility were unaffected by treatments except for dry matter and RUF digestibility that were reduced by RUF supplementation.

Roughage is the cheapest source of nutrients for herbivorous animals, and alfalfa is the best of the roughages because animals consuming alfalfa as a major part of their diet have an adequate supply of protein energy, and a considerable proportion of needed vitamins.

One hundred eighty-seven survey questionnaires asking for reproductive information for 1985 were sent to dairymen in Utah and Southeastern Idaho. Forty- two herds with current DHI information and whose owners or managers completed and returned the questionnaire were used to estimate economic losses due to reproductive problems, especially excessive days open, in Utah and Southeastern Idaho. Average days open for herds surveyed were 122.4 days with a standard deviation of 22.6 days, and a range of 89 to 177 days. Several factors were significantly correlated with days open including services per conception, previous calving interval, and missed heats. Missed heats accounted for most of the variability in days open with an r2 of .82. Surveyed dairymen were losing an average $1.22 per cow per day due to excessive days open beyond 90 days. In addition they were losing approximately $22.87 per cow per year due to reproductive levels inferior to the top expected levels and veterinary costs associated with reproductive problems other than excessive days open. Although this is the estimated average loss in Utah and Southeastern Idaho, dairymen should try to determine losses in their own herds due to reproductive problems because of the extreme variability which exists among herds. Utah and Southeastern Idaho dairymen are suffering se rious economic losses due to excessive days open and they need to improve their heat detection methods to r educe these losses .

The World Trade Organization’s (WTO) latest round of negotiations, the Doha Development Agenda (DDA), will likely change the way most agricultural products are traded around the world. These new liberalization policies will potentially affect the Canadian production and consumption of dairy products. This thesis uses a partial equilibrium model with stochastic world prices to evaluate the effects of these trade reforms on the Canadian dairy industry. Different liberalization scenarios are simulated and the outcomes are analyzed and discussed.

The World Trade Organization’s (WTO) latest round of negotiations, the Doha Development Agenda (DDA), will likely change the way most agricultural products are traded around the world. These new liberalization policies will potentially affect the Canadian production and consumption of dairy products. This thesis uses a partial equilibrium model with stochastic world prices to evaluate the effects of these trade reforms on the Canadian dairy industry. Different liberalization scenarios are simulated and the outcomes are analyzed and discussed.

Thesis (MSc(Agric (Production Physiology)(Animal and Wildlife Sciences)) -- University of Pretoria, 2000. / Includes bibliographical references.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 5 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 5 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 4 uppsatser.