The Effect of Different Grinding Sizes on Production Parameters of the Israeli Dairy Cow

Steven Rosen1, Catriel Tabori2, Asher Braun2, Tomer3
1-Israel Extension Service, 2Zemach Feeding Center, 3- Kibbutz Maoz Haim Dairy

Corn Grain represents the main ingredient today in Israeli dairy cows concentrate diet. Much past research has been carried out (particularly in the U.S.A.) to examine the best form of processing corn grain to optimize digestion and productivity of dairy cows. There is literature on steam flaked corn, cracked corn, roughly ground corn (size of average particles-3.14- 3.67 m"m) and finely ground corn (0.7-1.13 m"m). There has not been found in previous experiments the size of grounding that is performed in Israel. Both are considered "finely ground". Some researchers in the U.S.A. recommend an average of about 1.1 m"m and believe a finer ground will cause excessive ruminal fermentation and cases of S.A.R.A.
In Israel the corn marketed is usually about 1.0 m"m but frequently even more fine. This work was carried out to test these two different sizes (fine=0.7 m"m and regular ground corn=1.1 m"m.
In the dairy of Kibbutz Maoz Haim there exists two groups of 70 multiparous cows divided by even or odd number, that are similar in production parameters (number lactation, days in milk, milk production potential, etc.). They arrive at these barns after being three weeks in a fresh cow group. These groups were used in this study.
The ration contained 22% ground corn, 16.9% C.P., 1.78 M"Cal NEL/K"G D"M and17.5% NDF from forage (33% roughage).
The experiment was carried out in a crossover design.
The average size of the particles in the experiment was 700 micron for the finely ground corn and 1,081 microns for the regularly ground corn.
The average DMI for both groups were similar (26.07 kg. vs. 26.30 kg for the fine and regular corn respectively in the first period (before the crossover), and 24.03 vs. 23.96 after the crossover.
There were no differences between the groups in amount of milk, fat %, protein %, ECM or FCM in the first period (43.5 vs. 43.6, 3.43 vs. 3.33, 3.07 vs. 3.07, 42.92 vs. 42.08, and 41.2 vs. 40.9 for milk, fat%, protein %, FCM, and ECM for the regular and finely ground respectively. After the crossover both groups had similar drops in milk, protein % and ECM but the group that went from fine to regular ground corn had a higher increase in fat % (+1.88% vs. +0.041%), and a lower decrease in 3.5% FCM (-2.224 vs. -3.191 kg.).
This trend was even greater in very high producing cows, something that can point to S.A.R.A in cows fed finely ground corn. The very high producing cows that went from a regular ground corn to a finely ground corn also had an improvement in milk/cow /day.
In the analysis of manure, there was found a tendency of higher Non Fiber Carbohydrates (NFC) in the regular ground corn.
In summary, this study found a drop in milk fat percentage when cows went from a regular ground corn to finely ground corn. We also found a tendency for more milk in the finely ground corn in very high producing cows.