Madeline Bennett | AFNS Graduate Seminar

Date(s) - 06/05/2022
9:00 am - 10:00 am

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

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Thesis Topic: Physiological Effects of Feeding High vs Low Levels of Milk Replacer and Starch to Holstein Dairy Calves During the Weaning Transition


Current calf nutrition programs revolve around two central themes: liquid feed, to provide early nutritional needs for the calf, and calf starter, to provide the stimuli for rumen development to prepare the calf for weaning. It is currently unclear how milk provision and calf starter starch content impact gastrointestinal physiology and development in the young calf. The aim of this study was to assess how milk provision and dietary starch concentration impact the morphological and physiological development of the gastrointestinal tract. Forty-eight male Holstein calves were blocked by BW, STP, and dam parity and assigned, in a 2 x 2 factorial of milk replacer and calf starter starch content, to one of four treatments: low milk replacer (600 g/d; 4L) and low starch (10% starch, DM; LL), low MR and high starch (40% starch, DM; LH), high MR (1200 g/d; 8L) and low starch (HL), and high MR and high starch (HH). Calves were weaned starting on day 42 and ending on day 49, and calves were harvested one week later. Gut permeability was measured on days 28 and 56; rumen pH was measured continuously from day 42 to harvest. Gastrointestinal tissue samples were analyzed for tissue histology, gene expression of metabolic enzymes and nutrient transporter protein abundance. High milk diets had increased intestinal permeability and jejunal sodium-glucose cotransporter 1 abundance. High starch diets had increased monocarboxylate transporter 1 and tended to have increased anion exchanger 1 abundance as well as decreased papillae sloughing in the rumen. In the lower gut, higher starch diets showed increased jejunum villous blunting, and ileal epithelial separation. Higher milk provision likely increased glucose absorption in the jejunum. Increased starch conferred a protective effect on the rumen through increased SCFA absorption capacity and decreased sloughing, but low rumen pH negatively impacted lower gut morphology.