Benninghoff, Jens: Dietary strategies to optimize energy and glucose supply to lactating dairy cows. - Bonn, 2015. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
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author = {{Jens Benninghoff}},
title = {Dietary strategies to optimize energy and glucose supply to lactating dairy cows},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2015,
month = nov,

note = {Ruminants usually absorb only small quantities of glucose directly from the small intestine, because the majority of the glucose, regardless of dietary source, is fermented in the rumen to short chain fatty acids. Thus, the largest part of the glucose for covering the cow’s requirement has to be synthesized de novo, i.e. through gluconeogenesis, from precursor molecules. As lactation performance of dairy cows is steadily increasing and similarly, more glucose is required to sustain high milk yields, the question is which feeding strategies might help to adequately supply high-yielding dairy cows with energy and nutrients. In addition to fully utilizing the digestive capacity of the rumen, ruminally undegraded nutrients that can be digested in the small intestine may contribute to an optimized feeding. Starch, which flows into the small intestine and is digested and absorbed as glucose, can contribute to cover the glucose requirements. Often starch sources of low ruminal degradability are also less well digested in the small intestine. Therefore, the challenge is to process grain (starch) such that it is protected from ruminal degradation but digestible postruminally.
The objective of the first experiment was to estimate the ruminal degradation of crude protein (CP) and starch of ground wheat, barley, rye and maize grains as compared to xylose-treated wheat, barley and rye grains. Ruminal degradation was estimated using a standardised in situ procedure on ruminally cannulated steers. Data would indicate that the xylose-treatment was effective in reducing the extent of ruminal degradation of CP for the three grains, thereby augmenting the proportion of ruminally undegraded CP (RUP). However, only wheat and barley starches but not rye starch responded to the xylose treatment such that ruminally undegraded starch (RUS) was increased for barley and wheat. All treated grains had lower RUP and RUS values than maize grain. In the second experiment, thirty-six German Holstein dairy cows were assigned to one of two groups who were fed isocaloric and isonitrogenous diets, on dry matter basis, either 16% maize grain and 6.4% soybean meal or 17.8% of a xylose-treated wheat and 4.6% soybean meal. The xylose-treated wheat grain could replace maize grain and part of the soybean meal in a total mixed ration for lactating dairy cows and overall performance was slightly improved. Thus, xylose-treated wheat grain may be an alternative depending on overall ration composition and availability and costs of grain sources.
Finally, a study was conducted to evaluate if intermediary energy metabolism of cows fed with trans-10, cis-12 conjugated linoleic acid (CLA) was modified such that milk-energy compounds were produced with less intermediary energy expenditure as compared to control cows. Published data on supplemented CLA were assembled. The extent was calculated to which the trans-10, cis-12 CLA isomer has an impact on glucose and energy conversion in the mammary gland by modifying glucose equivalent supply and energy required for fatty acid and fat synthesis, and if this will eventually lead to an improved glucose and energy status of CLA-supplemented high-yielding dairy cows. A weak to moderate dose-dependent relationship between the amount of CLA administered and the amount of energy in glucose equivalents and energy for the synthesis of milk fat conserved from milk ingredient synthesis became obvious. Abomasal infusion of the trans-10, cis-12 CLA more consistently conserved energy in glucose equivalents. Milk fat synthesis showed an energy saving with a moderate dose-dependent relationship when CLA was supplemented orally. In conclusion, feeding a rumen-protected starch source that can be digested in the small intestine appeared more promising in terms of supplying a dairy cow with extra glucose than addressing intermediary glucose metabolism.},

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