As dairy producers push the envelope and feed higher volumes of milk, they attest to the perceived benefit. Marcos Marcondes, research professor at Miner Institute, saw an opportunity to study this phase of production in hopes of better understanding the black box of the preweaned ruminant.
How do higher volumes of milk replacer impact ruminal leakage and ruminal development, the flow of protein and energy to the calf, and the physiology of the rumen? To test this question, he fed a standard rate and double rate of milk replacer with cobalt to mark and track the flow of digestion through preweaned animals. The results of this project were recently discussed on the “Dairy Science Digest” podcast.
Accelerated volumes
Some progressive producers have moved to about 2 gallons per day (8 liters) of milk replacer or whole milk feeding model to program the calf for success in the first 42 days of life. This accelerated volume runs the risk of leakage or spill over from the abomasum into the rumen due to capacity. Early research verified that all functional classes of rumen microorganisms are stable in the rumen as early as 14 days of life.
“However, for the past 50 years, we assumed the protein from milk to be 100% rumen undegradable. Therefore, the spillover would be wasted,” described Marcondes. “Our research lab sought to determine if the milk protein is converted to microbial protein through digestion when leakage occurs.”
The goat kid was used as a model, and feeding rates were adjusted to reflect a percentage of total body weight. Kids were fed milk with a marker to determine how the milk flows through digestion.
The abomasum stretched for the larger meals, increasing capacity, yet still showed equal spillage into the rumen. “Regardless of meal size, we found milk in all four chambers: abomasum, rumen, small intestine, and large intestine,” Marcondes said. “Our data showed that over half leaked into the rumen, which was very unexpected.”
Tracking the milk through digestion
In this project, researchers quantified that milk’s passage rate through the intestine was 3.44 hours. For total emptying, three hours in the abomasum, rumen for an additional three hours, then six hours through the small and large intestines.
Preweaned rumen activity was observable through measurable volatile fatty acid (VFA) production. Additionally, ammonia production measured at 5.44 mg/dL, indicating an active microflora in the underdeveloped, yet productive rumen. This is substantial when compared to a fully functional lactating cow rumen at 9 mg/dL.
“We found 2.2 grams of microbial protein production,” stated Marcondes. “Calves this age require 21 grams per day, so 10% of the total requirement is not an insignificant amount and should be added to the nutritional software models going forward.”
He reminded, “These values were generated with zero grain in the ration — only milk, and would likely increase in starter-fed animals.”
Future research
There is an opportunity to better understand the mode of action for the improvements observed. At a glance, the higher plane of nutrition generated a visibly healthier rumen. Researchers enjoyed a decreased prevalence of scours, likely from improved intestinal health. It is speculated that elevated energy in the form of glucose could result in increased IgF1, which is known to improve rumen papillae development. A separate dataset, still under analysis, hopes to quantify the histological changes and determine the physiology responsible for these improvements.
The practical aspect of this foundational project is that feeding more milk does result in leakage, but not at a higher rate. The milk that is leaked into the rumen is utilized, through fermentation, to jumpstart the rumen and propel the animal into the next phase of production. These results should only be improved with the presence of starter grain.
These findings were summarized in a peer-reviewed open-access Journal of Dairy Science article found at: www.journalofdairyscience.org. To learn more, listen to the monthly podcast, “Dairy Science Digest” on your favorite podcast platform.
