Colostrum Quality not changed with
Shorter vs. 60d Dry Period
Grusenmeyer and others reported that colostrum quality did not differ between cows managed with 40-day compared to 60-day dry periods (Journal of Dairy Science, 89:Supplement 1, Abstract W114, 2006). These data were from 334 cows on three dairy farms. The specific values for the two dry periods were: 60-day = 77.6 mg/ml and 40-day = 76.4 IgG. Given the common standard of 50 mg/ml 79 percent of all samples were acceptable.
Using 781 cows from one 3,000 cow commercial dairy Watters and others reported similar findings (Journal of Dairy Science, 91:2595-2603, 2008). The IgG levels were: 56-day dry period = 58.5 mg/ml and 34-day dry period = 56.2 mg/ml.
Now additional data from a small sample of 52 cows from 2 herds (Shoshani and others, Journal of Dairy Science, 97:2909-2922, 2014) reinforces these earlier findings. The IgG levels were 61-day dry period = 48.9 and 42-day dry period = 48.2 mg/ml.
Grusenmeyer's findings included volume of colostrum collected. She observed:
"Colostrum yield averaged 7.9 kg (17.4 pounds) and varied across farms (6.7, 7.6, 9.4 kg - 1.4.7#, 16.7#, 20.7#). Shortening the dry period from 60 to 40 days decreased colostrum yield (8.9kg vs. 6.8kg - 19.6# vs. 15.0#): this difference was consistent across farms."
She noted that when you use 4 quarts of colostrum as a minimum threshold for volume 30 percent of the 40-day dry period cows failed to produce this much. This may be compared to an only 13 percent failure rate for cows with the 60-day dry period.