Effect of Dietary Interventions on Ruminal Biohydrogenation and Milk Fat Depression in Lactating Holstein Cows
Open Access
- Author:
- Baldin, Michel
- Graduate Program:
- Animal Science
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- December 07, 2016
- Committee Members:
- Kevin J. Harvatine, Dissertation Advisor/Co-Advisor
Kevin J. Harvatine, Committee Chair/Co-Chair
Alexander Nikolov Hristov, Committee Member
W. Burton Burt Staniar, Committee Member
Michael Green, Outside Member - Keywords:
- biohydrogenation
linoleic acid
milk fat depression - Abstract:
- Reduced milk fat still represents an issue on many dairy farms. Inhibition of milk fat synthesis is normally caused by bioactive trans fatty acids (FA) formed during ruminal biohydrohenation (BH), and this condition is called BH-induced milk fat depression (MFD). Contemporary lactating diets rich in corn feeds increase risk of BH-induced MFD. This may be because corn is rich in linoleic acid (LA), the parent compound for the formation of trans FA the cause MFD. This dissertation first demonstrates that considerable variation in LA concentration exists amongst commercially available corn hybrids. The variation was mainly attributed to hybrid and selection should focus on LA as a percentage of total FA, as this trait was not correlated with other nutrients important to the cow. Secondly, it was demonstrated that MFD is a multifactorial condition and that important interactions exist between dietary risk factors, individual cow effects, and feed additives. Supplementation with the methionine analog 2-hydroxy-4-(methylthio)butanoate (HMTBa) maintained higher milk fat when high producing cows received diets with increased risk of BH-induced MFD. Low producing cows did not undergo MFD, nor did their milk fat respond to HMTBa supplementation. Thirdly, it was demonstrated that an in vivo BH assay utilizing a perturbation tracee approach performed by bolusing FA through the rumen cannula was appropriate to assess the rate and extent of ruminal unsaturated FA BH as well as flux through specific BH pathways. Lastly, decreased BH-induced MFD with HMTBa supplementation was replicated and using the in vivo assay developed it was shown that the mechanism by which HMTBa prevents ruminal formation of bioactive trans FA is, at least in part, due to increased BH capacity. In conclusion, this dissertation presented opportunities to combat MFD by selection of corn hybrids low in LA and supplementation with HMTBa. Additionally, this work sets the framework for further research on milk fat by presenting an experimental design that efficiently investigates the interactions between risk factors and a novel in vivo assay appropriate to study ruminal BH.