TMR Particle Size Affects Components

Balanced rations for lactating dairy cows only work if ingredients are mixed properly.
TMR Particle Size Affects Components - Articles


Penn State Dairy Cows

Compared to previous summers, this August was not terrible but we still had plenty of hot, humid days. I know from past experience that when cows come off of an extreme weather event like we had in July, it takes several weeks for the cows to recover. Several ration adjustments were made to help cows maintain performance and body condition.

The typical ration for the lactating herd is 65% forage/35% concentrate. Our challenge this summer has been the starch level in the BMR corn silage is lower than what we usually feed. Normally our starch level in the total ration dry matter would range from 26 to 29%. With the ration at 65% forage the starch level in the diet was at 20%. The one difference with the bunk BMR corn silage was the 7-hr starch digestibility (% of starch), which was 75% compared to 68% from the bagged silage. The ration was adjusted to 60% forage and this increased the ration starch to 24%. The corn grain particle size was kept fine to observe any changes on production or the components.

Post-fresh cows calving soon after the July heat wave were not performing as well as expected. They receive a diet consisting of 50/50 forage/concentrate for the first 10 to 14 days post fresh. Their diet was adjusted to include more corn silage. The challenge with this group is the low dry matter intakes and trying to get adequate energy and protein into these animals. The starch level for this group was increased to 21% starch and the protein level had to be kept at 17% on a dry matter basis in order to meet the cows' requirement for metabolizable protein. The cows improved their intakes and milk production after this change was implemented

Overall with the ration changes made the cows were milking well and components were holding steady. Checking the website on components the bulk tank loads for the 12th and 14th showed the milk fat percent at 3.46% and 3.49% respectively. Dr. Jud Heinrichs had been testing his new particle size separator on individual feed ingredients and the total mixed rations (TMR). He relayed to me that our individual forages were right in line but our TMR was too fine. His results were reflective of the time period of the low fat tests. I talked to the assistant manager about the results and he double checked the TMR particle size (one or two days later). His results showed that the particle size was in line. After further discussion we realized the fine TMR particle size was reflective of a different feeder compared to the sample the assistant manager checked. Also, the fat test bounced back and was reflective of the correct particle size. The assistant manager called a group meeting of the farm employees and reviewed the protocols about proper mixing times.

After the incident with the TMR particle size, I changed the corn grain particle size to 50/50 coarse/fine. After this change was made both milk fat and milk protein percent improved. For the month of August the herd averaged 80.0 pounds with a 3.56% fat, 3.03% protein, 247,000 SCC and 6.4 mg/dl MUN.

IOFC Results

Month and YearNo Risk Mgt Gross Milk Price/cwtW/ Risk Mgt Gross Milk Price/cwtMilk income/cowFeed cost/cowIOFCAverage milk lbsLow BenchmarkHigh benchmark

IOFC Graph