Case history
This is a 155 Cow herd which calves all the year round with heifers calving mainly between April and September. In 1999 33 heifers were brought into the herd as opposed to 20 in 1998.
The Correct Magnets were installed on 24th October 1999.
Diet
Silage Analysis
Out of parlour feed in both years was a 60-40 Grass and Maize mix, which was balanced with in-parlour cake, the quantity and formulation depending on the silage quality. High yielding cows had access to additional cake via magnetic collar controlled feeders outside the parlour.
| Grass | DM | ME | CrP | Dvalue | |
| 1998 | 40.5 | 10.2 | 15.5 | 63 | |
| 1999 | 22.5 | 10.6 | 13.9 | 66 |
| Maize | DM | ME | CrP | Dvalue | |
| 1998 | 26.4 | 22.6 | 8.4 | 72 | |
| 1999 | 35.8 | 12.0 | 7.3 | 74 |
Milk Production
The figures for 1999/2000 have been adjusted to allow for the increased number of heifers introduced in 1999, this represented 10.2% of the herd. A sample of heifers taken from 1998 and 1999 averaged 6510 litres at 305 days compared to a sample of cows which averaged 8284 litres at 305 days, this is an increase of 27.3%. Therefore in 1999/00 to minimise this variable, 10.2% of each monthly total yield was increased by 27.3% so that there was a more meaningful comparison.
Whole herd production in Litres/cow/day.
| 1998/99 | 1999/00 | Increase/decrease in 1999/00 | ||
| Nov-Sept | 22.8 | 23.9 | +1.1 | |
| Nov-Apr | 22.1 | 23.4 | +1.3 |
Summary
Despite the grass silage having a very low dry matter in 1999 the adjusted figures show that the herd averaged an extra 1.3 litres per cow per day from November 1999 to the beginning of May 2000 compared to the previous year.