The Influence of the Timing of Feed Intake on Ruminal Fermentation and Milk Synthesis
Open Access
- Author:
- Rottman, Lauren Whitney
- Graduate Program:
- Animal Science
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- February 28, 2012
- Committee Members:
- Kevin John Harvatine, Thesis Advisor/Co-Advisor
- Keywords:
- dairy cow
pattern of feed intake
circadian
milk synthesis - Abstract:
- The rate of feed intake has been shown to vary over the day and is expected to create a daily rhythm of nutrient absorption. With daily fluctuations in available nutrients, milk synthesis may also vary over the day. Additionally, milk synthesis has been shown to fluctuate independently of nutrient availability, which would create times over the day that the nutrient profile does not match the nutritional needs of the mammary gland. Two studies were conducted to examine the circadian patterns of the dairy cow and to understand the relationship between timing of feed intake and milk synthesis. The object of the first experiment was to characterize the effect of timing of feed intake on the pattern of milk synthesis. The treatments for this experiment were cows fed once a day (1x fed) or every six hours in four equal meals (4x fed). The cows were milked twice a day for the first 14 d and then four times a day for the last 7 d of each period. There was a circadian pattern to milk and milk component synthesis over the day. Milk yield was high during the first milking interval (MI), decreased over the next two milking intervals, and for the 1x fed increased during the last milking interval but remained lower for 4x fed. Milk protein fluctuated over the day as well. Milk protein percent for both treatments peaked during the third milking interval with 4x fed peaking higher than 1x fed. The largest range was observed for milk fat over the day. The second and third milking interval exhibited the highest milk fat concentration and yield. The 4x fed was consistently higher in fat percent at each timepoint, but milk fat yield was only higher during the first two milking intervals. Non-esterified fatty acids were the only plasma metabolite with an effect of time, but no effect of treatment. The experiment demonstrated a clear pattern to milk yield and milk component synthesis that is affected by the timing of feed intake. The object of the second experiment was to identify a feeding regimen that complements the natural pattern of feed intake and milk synthesis. Cows were fed either a control diet (30.1% NDF) or two regimens that consisted of a combination of a high fiber diet (31.8% NDF) and a low fiber diet (26.9% NDF). The treatments for the experiments were the control diet fed at 0800 h (Con), the high fiber diet fed at 0800 h and the low fiber diet at 2200 h (HL), and the low fiber diet fed at 0800 h and high fiber diet at 1300 h (LH). The high and low fiber diets were fed at a ratio to provide the same nutrients as the control diet. Feeding times were selected to provide the rumen with a low fiber diet either during the high or low intake period of the day. There was a tendency for lower daily milk fat yield (P < 0.07) and fat corrected milk (FCM; P < 0.07) for HL compared to LH. There was a treatment effect for DMI (P = 0.01) with Con consuming 1.9 kg more than HL, but there was no difference between HL and LH. There was no effect of treatment on empty body weight. There was also no treatment effect to plasma metabolites, but as reported in the first experiment, there was an effect of time (P < 0.001 for all treatments). There was no treatment effect on VFA concentrations, but there was a tendency for a treatment by time interaction for valerate (P = 0.07). All VFA concentrations peaked at approximately1800 h and the acetate to propionate ratio peaked at 1200 h. Splitting the TMR ration into two separate rations that differ in their fiber level and feeding these at specific times over the day, decreases DMI with minimal effects on milk production. Lastly, there was a tendency for feed efficiency to be higher for LH compared to HL (P = 0.096).