Preliminary Study of Microbiological and Immunological Quality of Sheep Colostrum: Influence on Early Postnatal Weight Change

Colostrum is crucial for the survival, development, and the future productivity of newborns. In this study, we evaluated the immunological and microbiological quality of colostrum in 28 Rasa Aragonesa ewes and its relationship with offspring growth during the first 48 h postpartum. Colostrum samples were collected by hand milking immediately after parturition. Immunoglobulin concentration was assessed using Brix refractometry and the samples were categorised according to their immunoglobulin content: high (>24 Brix value), medium (19–23 Brix value), and low (< 19 Brix value). Bacterial counts of aerobes and coliforms were determined with the 3M Petrifilm™ system and the weight of the lambs was recorded using a digital suspension scale. The mean aerobic count (AC) was 3.63 ± 0.69 log₁₀ CFU/mL after 24 h of incubation and the mean coliform count (CC) was 1.59 ± 0.82 log₁₀ CFU/mL after 24 h of incubation. Colostrum with a high immunoglobulin concentration had lower aerobic count after 48 h of incubation than that with poor immunological quality. In relation to coliform counts, similar values were found in all groups. No significant differences were observed in terms of lamb weight gain according to colostrum quality. In conclusion, the immunological quality of colostrum affected the AC determined, but it did not affect CC or early postnatal lamb weight. These findings offer preliminary insights into the usefulness of the Petrifilm™ system in microbiological quality determination of colostrum and its relationship with immunological quality determined in vitro.