Effect of Acetate Supplementation on Milk Fat Production and Mammary Lipogenesis
Restricted (Penn State Only)
- Author:
- Matamoros, Cesar Ivan
- Graduate Program:
- Integrative and Biomedical Physiology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- February 03, 2022
- Committee Members:
- Andrew Patterson, Outside Unit Member
Gregory Shearer, Major Field Member
Arlyn Heinrichs, Outside Field Member
Kevin Harvatine, Chair & Dissertation Advisor
Donna Korzick, Program Head/Chair - Keywords:
- de novo
fatty acids
sodium acetate
de novo
fatty acids
sodium acetate - Abstract:
- Milk fat is the most variable component of milk, and it is also a major driver of the economic value of milk. Milk fat synthesis is highly responsive to environmental, management, and nutritional factors and understanding the regulation of milk fat synthesis is important to the development of tools to increase its yield. Milk fat originates from two distinct biological pathways where fatty acids are either made through de novo lipogenesis in the mammary or taken up from circulating preformed fatty acids. There have been some indications that acetate supplementation increases milk fat synthesis by an apparent stimulation of mammary de novo lipogenesis. The objective of this dissertation was to understand how acetate supplementation increases milk fat synthesis and identification of factors that interact with acetate supplementation. To accomplish these objectives, 4 experiments were designed and conducted. Acetate is supplemented as sodium acetate to avoid negative effects in dry matter intake. The first experiment focused on understanding if the increase in milk fat synthesis with sodium acetate supplementation was due to increased supply of acetate or an increase in dietary cation-anion difference due to the sodium, which has also been associated with increased rumen fiber digestion and an increase in milk fat synthesis (Chapter 3). Both sodium acetate and sodium bicarbonate that provided an equal amount of sodium increased milk fat, but sodium acetate was mostly due to 16 carbon fatty acids while sodium bicarbonate was an increase in all categories. The experiment also demonstrated that dietary supplementation of acetate increases increased plasma concentration of carbon substrates in plasma, such as acetate and β-hydroxybutyrate. There is a clear daily rhythm to milk synthesis in cows, which appears to be driven by the timing of nutrient intake, among other things. During food entrainment it is unknown if a specific nutrient drives the changes in the daily rhythm. The second experiment tested if the timing of acetate supplementation influenced the daily rhythms of milk synthesis, dry matter intake, plasma metabolites, and core body temperature (Chapter 4). In this experiment, restricting acetate supplementation to the day or night had no effect on the rhythm of overall milk yield, but it affected the rhythms of milk protein synthesis. The daily rhythm of plasma acetate was also modified as the time of peak of plasma acetate concentration was influenced by timing of acetate supplementation. Efficient use of acetate supplementation to increase milk fat production is dependent on understanding how acetate interacts with other dietary factors. The third experiment investigated if dietary acetate supplementation interacts with dietary fiber level, considering that the source and type of dietary carbohydrates is a major determinant of ruminal short chain fatty acid production (Chapter 5). Acetate supplementation increased milk fat synthesis regardless of dietary fiber level. It is also important to understand how acetate supplementation interacts with animal-related factors. Genetic potential of milk fat synthesis varies between animals, and much of the variation is explained by a polymorphism in the diacylglycerol O-acyltransferase 1 gene. Furthermore, cows are expected to continue growing throughout their first lactation, thus multiparous and primiparous differ in their energy requirements. The fourth experiment investigated if parity and genetic potential interacts with acetate supplementation’s impact on milk fat synthesis (Chapter 6). The effect of acetate supplementation was largely insensitive to parity or genetic potential for milk fat synthesis. In conclusion, the overall results support the idea that acetate supplementation increases acetate supply to the mammary gland, and subsequently mammary de novo lipogenesis is stimulated resulting in an increase in milk fat yield. This increase in milk fat synthesis is mostly because of an increase in the yield of 16 carbon fatty acids, suggesting that the additional acetate supply drives mammary de novo lipogenesis towards completion. Furthermore, acetate supplementation was consistent across diets that vary in dietary fiber level and in cows that differ in parity and genetic potential for milk fat production.