Physical characterization of milk fat from dairy cows fed supplemental palmitic or stearic acid
Open Access
- Author:
- Kiser, Mason Elizabeth
- Area of Honors:
- Veterinary and Biomedical Sciences
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Dr. Kevin John Harvatine, Thesis Supervisor
Robert John Vansaun, Thesis Honors Advisor - Keywords:
- milk fat
direct scanning calorimetry
palmitic acid
stearic acid
supplemental fatty acids - Abstract:
- Milk fat and milk fat products are an essential of the modern human diet. With the multitude of products and variety of uses for them, understanding the physical and chemical properties of milk fat has never been more crucial to producing products that adhere to the expectations of the consumer. The chemical properties, and what influences them has been highly researched to produce the healthiest varieties of milk fat products; however, influencing the physical properties through dietary change is a lesser studied area. It is known that feeding dairy cattle fatty acids such as palmitic acid and stearic acid will influence the physical properties of milk fat, but it is unknown which fatty acid will have a larger effect on the melting temperature of milk fat samples. The purpose of this experiment was to compare the effect feeding palmitic vs. stearic acid has on the melting temperature of milk fat samples. In this study, 12 high producing Holstein cows (mean pretrial milk yield = 53.4 ± 8.7 kg/d; mean ± SD) were fed four different treatments conducted in a 4x4 Latin square design with 21-day periods. The treatments were a control diet with no fatty acid supplementation, a high palmitic acid diet (HP; 91% C16:0), a diet high in stearic acid (HS; 92.5% C18:0) and an intermediate blend of palmitic and stearic acid supplementation (INT; 45% C16:0). The cattle were milked at 0700 and 1800 hours in a parlor, and milk samples were taken at both milkings on day 19 through 21 of each of the four periods. Direct scanning calorimetry was used to analyze the samples and obtain melting temperatures and enthalpies for two melting processes of each individual sample. Increasing dietary palmitic acid (C16:0) increased the melting temperature of the milk fat to the largest degree. Increasing dietary stearic acid (C18:0) decreased the melting temperatures of the milk fat compared previous studies. Feeding an intermediate supplement of palmitic and stearic acid increased the melting temperature of the milk fat, but not nearly to the degree as feeding palmitic acid alone. This supports previous research suggesting there is a higher transfer efficiency of dietary palmitic acid to milk and a lower desaturation by the ∆9-desaturase activity compare to stearic acid. The diet most conducive to increasing the melting temperature of milk fat is a diet containing a high level of palmitic acid, which may be conducive to some food products, but detrimental to others.