Let's check out what is "moo" with Cornell dairy research. Two articles were recently published in the Journal of Dairy Science Communications from Cornell's veterinary school on colostrum.

Lag time from calving to first colostrum harvest in Holstein dairy cows: association with colostral IgG, volume, and dry matter - JDS Communications.

The first study (Mann et al., 2025) wanted to observe what would happen to the colostrum harvested from a cow if there was a delay between the time she gave birth and the time she was milked for colostrum. Cows were then separated into 6 different groups based off of how soon their colostrum was harvested.  640 Holstein cows were separated into the following groups: 0-3 hrs, 3-6 hrs, 6-9 hrs, 9-12 hrs, 12-15 hrs, and 15-18 hrs of delay. The results from their study stated the "first milking of colostrum can be delayed for up to 9 hours without a significant reduction in IgG concentration." While you can delay colostrum harvest from the dam up to 9 hours, it is still recommended to feed the calf colostrum immediately after birth. 

Evaluating bacterial growth in raw, frozen, and heat-treated colostrum inoculated with fecal Escherichia coli - JDS Communications.

The second study (McKane et al., 2025) looked to explore how fecal E. coli grows in raw, frozen, and heat-treated colostrum. The colostrum samples were collected and then contaminated with E. coli by the research team. Next, the samples were incubated for 24 hours, and the bacterial growth was measured. The number of E. Coli in the samples at 0 and 2 hours did not differ between the groups. Yet after 4, 6, 8, and 24 hours more E. Coli was present in the heat-treated and raw colostrum as opposed to the frozen colostrum. 

In conclusion, the best way to maintain the integrity of your high-quality colostrum is to not delay longer than 9 hours before harvesting your colostrum.  Freezing is a great way to slow the growth of bacteria in colostrum. It is important to note that freezing only slows growth and doesn't stop it entirely. Thus, make sure that the colostrum you are freezing is as clean and high quality as possible to prevent high contamination levels. The better your colostrum management program, the greater the health benefits for your calves.