In Ireland the calf mortality rate is high (4.6%) compared to other European countries (for example, 3.7% in Norway). It is unknown whether this is related to colostrum quality as few studies have investigated the colostrum quality of Irish dairy cows.
Antibodies are not transferred during pregnancy, so newborn calves rely on colostrum to gain protection against disease and infection.
Immunoglobulin G (IgG) is the main antibody found in cow colostrum and is commonly used to represent its quality; colostrum with an IgG concentration higher than 50g/l is believed to be of good quality.
In this study, researchers from the Animal and Grassland Research and Innovation Centre and University College Dublin, took colostrum samples from 704 dairy cows of varying breed and lactation number throughout 2011.
The study was carried out on four grass-based Teagasc research farms in southern Ireland, where calves were removed immediately after birth and cows were milked at the next scheduled herd milking. The weight of colostrum and the concentration of IgG were then measured.
Main findings
Generally, colostrum collected in this study was of high quality, with an average IgG concentration of 112g/l – more than doubling the ‘good quality’ benchmark.
This may be due to “good grass-based nutritional management and the use of a relatively low-yielding cow type that produces low weight of colostrum,” said lead author Muireann Conneely.
Scientists found higher concentrations of IgG in colostrum from older parity cows, cows that were milked sooner after calving, and cows that calved earlier in the calving season.
Although colostrum quality increased with parity, 90% of first-lactation heifers produced good quality samples.
For this reason, the authors advise farmers to ignore any previous recommendations to automatically dispose of colostrum from first-lactation heifers.
IgG tended to be more concentrated in smaller samples of colostrum, and less colostrum was produced by lower parity cows, cows with lighter calves, and cows milked earlier post-calving.
There was a 1.1% decrease in IgG concentration per hour post-calving, however researchers confirmed this was not caused by dilution. Investigating how and why this happens is an area for future research.
Implications
The high colostrum quality from cows in this study does not support the idea that colostrum quality is linked to the higher calf mortality rate in Ireland.
The production of a large quantity of colostrum could indicate to farmers that it is of lower quality, but this should be tested on-farm.
Many factors determine colostrum quality, but researchers conclude that “reducing the time interval between calving and collection of colostrum is the most practical means by which the farmer can maximise colostral IgG concentration”.
Written by Natasha Boyland
Source: Bsas
