One Pen of Cows Can Significantly Impact The Bulk Tank

Cows performed very well in October and I had the expectation that November would be no different. However, as I did my daily check of the bulk tank weights I immediately saw that there was a problem during the first week of the month; knowing where the cows should be in the bST cycle, milk production was dropping instead of increasing. Further investigation ensued to find the problem.

Our bulk tank weights were down about 1400 pounds/pick-up. I started evaluating each pen of cows. The two pens of mature cows were doing very well. The 2-year old group was down a little but with the number of fresh heifers and the low days in milk, they were not that far off. The tie-stall barn (where all the research feeding trials occur) was the culprit. For the month of October the tie-stall barn averaged 86 pounds, on November 11th the barn was averaging 75 pounds. I calculated the number of cows in the barn and the difference in milk production and that accounted for 1200 pounds of lost milk in the bulk tank. Typically when cows are switched over to their research diets there may be a slight production drop but nothing like what I observed. The next step was to break out each group of research cows to find the source of the problem. Figure 1 shows the groups’ performance starting the middle of October when they were still on the herd diet and what happened when they began their research diets the end of that month. This production drop on the different research diets offered an opportunity to explore some concepts related to feeding cows.

Trial -13=the number of cows on project.

Trial-13 was interesting for several reasons. First, the ration incorporated 2013’s corn silage that had fermented only a few weeks. Their control diet was 65% forage: 35% concentrate. I had numerous calls from producers in Pennsylvania where milk production dropped up to 10 pounds when incorporating this year’s corn silage. These research cows went from 95 pounds on the herd diet (2012 corn silage) to 85 pounds when started on 2013 silage. The cows dropped another 6 pounds when they were switched to the challenge ration of 60% concentrate. This timed with the drop in the bulk tank. However, these 13 cows were not the main culprit in the production drop.

Trial-29 was feeding 62% forage however their diet was very different from the herd diet. They were using different ingredients compared to what is typically fed. These cows were averaging 99 pounds at 235 days in milk prior to the start of the research project. Figure 1 illustrates their production drop. It just so happened that their lowest milk production also occurred at the same time as Trial-13 and why production for the tie-stall barn was so low.

Another issue we investigated was the start of winter dysentery. I was informed that some of the cows appeared looser than normal but definitely not what is observed when winter dysentery goes through the herd. It was very sporadic amongst pens and the production drop often observed was not occurring. I evaluated dry matter intake and it was normal.

The situation with the tie-stall barn does show that one pen of cows can significantly impact the bulk tank. It also illustrates that having production information on individual pens is very helpful. If this had occurred in a commercial herd without this information and it was assumed the problem was with the entire herd and not just a group of cows, ration changes could have been made that were not necessary. The end result could be a larger drop in production. For the month of November the herd averaged 83 pounds with a 3.62% milk fat, 3.12% milk protein, 182,000 SCC and 8.4 mg/dl MUN.