Changes in Forages, Locations and Cows

6/15/2013 7:00 AM

A pril was a very cool month and from the cow’s perspective, it was probably very refreshing. We finally transitioned from the bag corn silage to the bunk at the Penn State dairy farm. Both the bunk and total mixed ration were sent out for analyses. We had an in-service training scheduled for our Extension Dairy Team and Travis Edwards, assistant manager, and I were conducting a workshop on how to visually appraise forages and interpret analyses reports. So the timing was perfect to send samples out to check the corn silage and TMR, both for the herd and for the educational opportunity.

For the first two weeks of April, the herd was getting 50/50 of the bag and bunk corn silage. Cows stayed at 82 pounds. The herd was switched to all bunk corn silage in the middle of the month. The analyses came back on a dry matter basis, 7 percent protein, 34 percent neutral detergent fiber, 57 percent NDF digestibility, 42.5 percent starch and 76.7 percent 7-hour starch digestibility. I have been including the 7-hour starch digestibility to monitor over time how this number is changing.

Our components tend to slump in April and May. Now that I am monitoring the 7-hour starch digestibility, the goal is to evaluate which grain particle size best matches the corn silage as digestibility increases. This may change as the amount of corn silage fed is adjusted, especially after first cut haylage is harvested.

I revised the herd ration to compensate for the lower protein in the silage as well as the higher starch digestibility. With the haylage inventory very limited, I don’t have many options to adjust forages if I am to keep the ration at 65 percent forage. I increased the canola and decreased the corn grain to 3 pounds. I kept the grain particle size very fine and monitored components for any changes. Milk production increased to 85 pounds and there was a slight boost in the milk protein. Milk urea nitrogen increased to 13 milligrams per deciliter for two pick-ups since the new ration was implemented. However, they have come back down to 10 milligrams per deciliter.

When research studies are conducted that include a relatively large number of cows, I like to evaluate them before and after the study.

At Penn State, this is a unique opportunity to see how cows adjust to a different environment and to different diets. Thirty cows were moved into the tie-stall barn from the free-stall the middle of January. They received the herd diet, which was the 65 percent forage ration, for two weeks. They averaged 99 pounds at 83 days in milk. In February and March, when they were on a 55 percent forage-based diet they averaged 98.7 and 91.0 pounds at 111 and 140 days in milk, respectively. At the end of April, when they went back on the 65 percent forage-based diet and moved to the free stall barn, they averaged 95.4 pounds at 170 days in milk. This illustrates that cows can positively respond in milk production going to higher forage based diets, even as their days in milk are increasing. The argument could be made that production increased because of moving back to the free stall barn, which is entirely possible. However, if true, it does not appear the high forage diet hindered them from responding positively.

Another interesting dynamic is the variability of how cows adjust to a different environment. Out of the 30 cows on this research project, about a third were very consistent in production regardless of the ration fed and which environment they were in. Another third took a significant drop in production when they moved into the tie-stall barn and increased substantially when moved back to the free stall, and the other third increased in milk production in the tie-stall and have trailed off since moving back to the free-stall. It comes back to the point of dealing with individuals and as much as we examine groups and herds based on averages, there can be quite a range in the dynamics of individual cow performance. For the month of April the herd averaged 84 pounds with a 3.77 percent fat, 3.17 percent protein, 176,000 SCC and 10.8 milligrams per deciliter MUN.

Editor’s Note: Virginia Ishler is the Penn State Extension nutrient management specialist.

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