The effect of maternal supply of rumen-protected protein to Holstein Friesian cows during the dry period on the transfer of passive immunity and colostral microbial composition.

The objective of this study was to analyze if maternal supply of rumen-protected protein during the dry period can affect the IgG concentration and microbial composition of colostrum and the IgG absorption and fecal microbial composition in the calf. Seventy-four multiparous Holstein Friesian (HF) dairy cows were stratified per parity and randomly assigned to one of 2 different dry period diets, a diet with a low crude protein (CP) level (LP) and a diet with a high CP level (HP) by addition of rumen-undegraded protein (RUP; formaldehyde-treated soybean meal, Mervobest, Nuscience, Drongen, Belgium). Colostrum was collected within 1 h after calving and IgG concentration was quantified by radial immunodiffusion analysis. Forty-nine calves (23 female and 26 male) were enrolled in the trial with a 2 × 2 factorial design, with prenatal and postnatal treatment as the 2 independent variables. This led to 4 experimental groups: LPLP, LPHP, HPLP, and HPHP, in which the first 2 letters refer to the prenatal treatment (diet of the dam) and the last 2 refer to the postnatal treatment (diet of the colostrum-producing cow). Calves received 3× 2 L of colostrum within 2, 6, and 24 h after birth. Meconium and feces were collected solely from female calves (n = 18) by digital palpation of the rectum, immediately after birth and before colostrum administration and at d 3 of age. Microbial DNA was extracted from meconium (n = 9), feces (n = 15), and colostrum (n = 49). Amplicon sequencing of the bacterial V3-V4 region of the 16S rRNA gene was performed for characterization of the bacterial communities. Colostrum IgG concentration was higher in cows that were supplemented with RUP, especially in cows entering their second lactation (LSM ± SEM 61.3 ± 2.3 vs. 55.2 ± 2.8 g of IgG/L). Calves born out of LP cows that received colostrum from HP cows (LPHP) had a lower serum IgG level compared with HPHP and LPLP calves (LSM ± SEM 14.2 ± 1.3 vs. 18.8 ± 1.2 and 20.9 ± 1.3 g of IgG/L in HPHP and LPLP, respectively). The most abundant phyla in colostrum were Proteobacteria (48.2%), Firmicutes (24.8%), Bacteroidetes (9.5%), and Actinobacteria (5.0%). The most abundant phyla in calf meconium and feces were Firmicutes (42.5 and 47.5%), Proteobacteria (21.7% and 33.7%), Bacteroidetes (16.8% and 15.7%), and Actinobacteria (2.9% and 3.1%). There was no difference in the overall microbial communities between colostrum from HP and LP cows. However, 2 genera (both members of the family Lachnospiraceae) were more abundant in colostrum from HP cows compared with LP cows. The microbial composition of meconium, feces and colostrum differed from each other. Fecal samples were more similar to each other and are characterized by a lower intersample diversity compared with colostrum and meconium samples. To conclude, increasing the CP level by addition of RUP in the dry period diet affected the colostrum IgG concentration and the transfer of passive immunity, but did not change the overall microbial composition of colostrum nor of meconium and feces in the calf.

Exploring the microbial composition of Holstein Friesian and Belgian Blue colostrum in relation to the transfer of passive immunity.

For centuries, multicellular organisms have lived in symbiosis with microorganisms. The interaction with microorganisms has been shown to be very beneficial for humans and animals. During a natural birth, the initial inoculation with bacteria occurs when the neonate passes through the birth canal. Colostrum and milk intake are associated with the acquisition of a healthy gut flora. However, little is known about the microbial composition of bovine colostrum and the possible beneficial effects for the neonatal calf. In this prospective cohort study, the microbial composition of first-milking colostrum was analyzed in 62 Holstein Friesian (HF) and 46 Belgian Blue (BB) cows by performing amplicon sequencing of the bacterial V3-V4 region of the 16S rRNA gene. Calves received, 3 times, 2 L of their dam's colostrum within 24 h after birth. Associations between colostral microbial composition and its IgG concentration, as well as each calf's serum IgG levels, were analyzed. Colostrum samples were dominated by the phyla Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria. The 10 most abundant genera in the complete data set were Acinetobacter (16.2%), Pseudomonas (15.1%), a genus belonging to the Enterobacteriaceae family (4.9%), Lactococcus (4.0%), Chryseobacterium (3.9%), Staphylococcus (3.6%), Proteus (1.9%), Streptococcus (1.8%), Enterococcus (1.7%), and Enhydrobacter (1.5%). The remaining genera (other than these top 10) accounted for 36.5% of the counts, and another 8.7% were unidentified. Bacterial diversity differed significantly between HF and BB samples. Within each breed, several genera were found to be differentially abundant between colostrum of different quality. Moreover, in HF, the bacterial composition of colostrum leading to low serum IgG levels in the calf differed from that of colostrum leading to high serum IgG levels. Results of the present study indicate that the microbes present in colostrum are associated with transfer of passive immunity in neonatal calves.

Invited review: MicroRNAs in bovine colostrum-Focus on their origin and potential health benefits for the calf.

Colostrum is the first milk produced by a cow after she gives birth. Compared with mature milk, it has a high concentration of immunoglobulin G. Calves are born without circulating antibodies, thus ingestion of colostrum is necessary to protect the calf against pathogens in the first challenging weeks of life. In addition to the life-saving supply of antibodies, colostrum contains minerals, vitamins, growth factors, and immune cells. Recently, microRNAs (miRNAs) were added to that list. MicroRNAs are short, non-coding RNA molecules that can regulate gene expression at the post-transcriptional level. They are thought to act as key regulators of diverse biological and developmental processes. Colostrum contains higher amounts of miRNAs than mature milk; immune- and development-related miRNAs are prominent. Their expression pattern in milk is likely to be influenced by maternal nutrition and environment. The fat content of the maternal diet appears to have a major effect on expression of miRNAs in milk and in the neonate. The immunological state of the mammary gland seems to affect miRNA expression as well. In cows diagnosed with subclinical mastitis, alterations in the expression of miRNAs in milk have been observed. It is believed that miRNAs in colostrum and milk are signaling molecules passed from mother to newborn. They are packaged in extracellular vesicles, which makes them resistant to the harsh conditions in the gastrointestinal tract. Therefore, they can reach the small intestine, where they are absorbed and transferred into the bloodstream. MicroRNAs are important for the development of the intestines. For example, miRNAs stimulate cell viability, proliferation, and stem cell activity of the intestinal epithelium. Furthermore, miRNAs seem to act as key players in the development of the complete immune system. They can, among other things, regulate B- and T-cell differentiation and affect interleukin production of macrophages. The abundance of miRNAs in colostrum and milk and the possibility for their absorption in the intestines of the neonate supports the hypothesis that these tiny molecules are important for the development of the newborn. The probable relation of diet to the expression of miRNAs by the mother creates a possible avenue to optimize expression of miRNAs and improve neonatal maturation.