Preventing Bacterial Contamination and Proliferation During the Harvest, Storage, and Feeding of Fresh Bovine Colostrum

The objectives of this study were to identify control points for bacterial contamination of bovine colostrum during the harvesting and feeding processes, and to describe the effects of refrigeration and use of potassium sorbate preservative on bacteria counts in stored fresh colostrum. For objective 1, first-milking colostrum samples were collected aseptically directly from the mammary glands of 39 cows, from the milking bucket, and from the esophageal feeder tube. For objective 2, 15-mL aliquots of colostrum were collected from the milking bucket and allocated to 1 of 4 treatment groups: 1) refrigeration, 2) ambient temperature, 3) refrigeration with potassium sorbate preservative, and 4) ambient temperature with potassium sorbate preservative. Subsamples from each treatment group were collected after 24, 48, and 96 h of storage. All samples underwent bacteriological culture for total plate count and coliform count. Bacteria counts were generally low or zero in colostrum collected directly from the gland [mean (SD) log10 cfu/mL(udder) = 1.44 (1.45)]. However, significant bacterial contamination occurred during the harvest process [mean (SD) log10 cfu/mL(bucket) = 4.99 (1.95)]. No additional bacterial contamination occurred between the bucket and the esophageal feeder tube. Storing colostrum at warm ambient temperatures resulted in the most rapid increase in bacteria counts, followed by intermediate rates of growth in nonpreserved refrigerated samples or preserved samples stored at ambient temperature. The most effective treatment studied was the use of potassium sorbate preservative in refrigerated samples, for which total plate count and total coliform counts dropped significantly and then remained constant during the 96-h storage period.

Effect of fermentation and formalin preservation on the protein component of bovine colostrum

Colostrum was inoculated with Streptococcus lactis or yogurt culture or preserved with .1% (vol/vol) formalin in two separate experiments. All preparations then were stored at ambient temperature for 24 days. With increasing storage time, a larger proportion of the total colostrum nitrogen was not precipitated in 10% (wt/vol) trichloroacetic acid. By day 24, this represented 30 to 35% for the fermented samples and 10 to 15% for the formalin preserved samples. The majority of this nonprecipitable nitrogen was amino acids and small peptides. Most of the nitrogen in colostrum even after 24 days of storage should be nutritionally useful to the calf because even the nonprecipitable portion is amino acids and peptides.

Chemical changes in bovine colostrum preserved with formalin or by fermentation

Fresh bovine colstrum from second and third milkings postpartum was inoculated with either a yogurt culture or Streptococcus lactis or preserved with .1% formalin in two separate experiments. There was a rapid decrease in pH of the fermented samples which corresponded to decreased lactose concentrations and increased lactate and titratable acidity. Titratable acidity in the fermented colostrums increased further after 10 days from the production of volatile fatty acids, but pH did not decrease. The pH of the yogurt fermentations in Experiment 2 decreased to 3.8, and the continued increase in titratable acidity was from lactic acid rather than volatile fatty acids. The lowest pH of all other fermentations was 4.1. The extent of metabolism of the formalin-preserved colostrum was much less than for the colostrum fermented by either culture.

Absorption of colostral proteins by newborn calves fed unfermented, fermented, or buffered colostrum

Unfermented, frozen colostrum from the first three postpartum milkings of 10 cows was thawed, pooled, and treated to produce three diets: 1) unfermented, 2) fermented (7 days at 25 to 27 C), and 3) fermented (as in 2) with pH adjusted to match that of unfermented colostrum. Eighteen newborn, unsuckled Holstein calves were assigned randomly to one of the three diets. Colostrum diets were thawed and fed at 0, 8, 16, 24, and 36 h. Blood was sampled at 0, 4, 8, 16, 24, and 48 h. Minimal breakdown of colostral gamma-globulin and immunoglobulin G (IgG) occurred during fermentation. Protein breakdown during fermentation was associated primarily with the casein fraction. Concentrations of gamma-globulin in serum of calves receiving unfermented colostrum were higher than those of calves fed fermented colostrum at all sampling times beyond 0 h. Concentrations of gamma-globulin in serum of calves fed buffered colostrum were intermediate. Concentrations of IgG followed a similar trend. Health problems were not encountered, indicating potential for passive immunization of newborn calves via fermented, buffered colostrum in emergency situations.