Nicole Briggs | ALES Graduate Seminar

A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Nicole Briggs. This seminar is open to the general public to attend.

Thesis Topic: Effect of source and concentration of supplemental trace minerals on apparent absorption and retention, performance and physiological indicators of trace mineral status in lactating Holstein dairy cows

MSc with Dr. Michael Steele.

Seminar Abstract:

Inorganic sources of trace minerals are commonly supplemented in dairy cow diets; however, there has been an increase in the supplementation of minerals complexed with organic compounds. Organic sources of trace minerals are thought to be protected from antagonistic interactions within the gastrointestinal tract and therefore have increased bioavailability for absorption and rumen fermentation, enhancing their utility for production. The objective of this study was to investigate the effect of source and concentration of supplemental trace minerals on productivity, apparent absorption, apparent retention, rumen fermentation parameters and physiological indicators of trace mineral status (vitamin B₁₂ and GSH-Px) in lactating Holstein dairy cows. Six lactating, cannulated, Holstein cows (129 ± 12 DIM; mid to late lactation) were used in a 6 x 6 Latin square design with a 28-d experimental period (23-d of adaptation and 5-d of sample and data collection). The same basal diet was fed daily, but with different sources (organic [ORG] versus inorganic [INO]) and concentrations (50%, 100%, and 200% based on NRC recommendations) of supplemented trace minerals (Co, Cu, Mn, Se, and Zn). Over the 5-d data and sample collection period, feed intake, water intake, blood, total milk, urine, and feces were collected daily, while rumen fluid and pH were collected during the final two days of the sample collection period. Results from chapter 2 revealed organic trace mineral supplementation decreased milk yield and milk fat yield compared to inorganic supplementation; however, low levels of organic trace mineral supplementation provided the same milk yield as all levels of inorganic supplementation. Fecal excretion of all trace minerals increased with increasing concentration of trace minerals in the diet. Organic cobalt supplementation exhibited higher apparent absorption and retention, which could be an indication of increased bioavailability of organic cobalt. Selenium apparent absorption and retention was impacted by dietary concentration, where high levels of organic and inorganic supplementation showed higher absorption and retention than low levels. The results in chapter 3 determined that source and concentration of supplemental trace minerals does not impact serum trace mineral status, with the exception of cobalt at high levels (200%), and does not impact serum GSH-Px activity or the concentration of vitamin B₁₂ concentration in plasma, ruminal fluid or milk. Organic trace mineral supplementation decreased the minimum rumen pH compared to inorganic supplementation. In addition, treatments affected the rumen environment in a dose-dependent manner where high organic supplementation (200%) was not beneficial in the production of total VFA compared to low (50%) organic supplementation. Furthermore, source and concentration of trace minerals caused a shift in the proportions of certain major and minor VFA, excluding butyrate and valerate. More research focused on efficient supplementation of trace minerals to lactating dairy cows would allow producers to be more sustainable and profitable, while still maintaining performance of the herd.