The effect of probiotics, phytobiotics and their combination as feed additives in the diet of dairy calves on performance, rumen fermentation and blood metabolites during the preweaning period

This study aimed to evaluate whether probiotics, phytobiotics or their combination as feed additives, given during the preweaning period to neonatal calves, can enhance calf health, performance, and metabolic status. 44 Polish neonatal Holstein-Friesian calves were grouped by sex (22 female and 22 male) and parity (22 born to primiparous cows and 22 born to multiparous cows) and assigned randomly to 4 treatment groups (11 calves each): control (CON, without feed additive), multi-strain Lactobacillus probiotic (PRO, 250 mg/calf/d), phytobiotic (PH, 50 mg rosmarinic acid/calf/d), and the combination of probiotics and phytobiotics (PROPH, combined PRO and PH treatments). The feed additives were provided into colostrum as well as milk replacer immediately before feeding. During the first 12 h of life, calves received 4 L colostrum; on days 2 and 3: 2 meals/d of 2 L of transition milk; from days 5 to 49: 6 L/d of milk replacer (150 g powder as feed/L) in 3 feedings; and from days 50 to 56 : 2 L/d of milk replacer in 1 feed. The PROPH calves had higher body weights on days 28 (P = 0.021) and 56 (P = 0.015) compared to the CON group. Incorporation of the combination of probiotics and phytobiotics as feed additive had significant beneficial effects on average daily gain, starter intake and total dry matter intake (P ≤ 0.05) over the experimental period. Throughout the study, the diarrheal scores 3 (mild diarrhea) and 4 (severe diarrhea) were 2.8 (P = 0.022) and 2.7 (P = 0.016) times lower, respectively, for PROPH calves compared to the scores of the CON calves. In addition, the PROPH calves had lower numbers of parasite oocysts/cysts per gram of feces on d 28 (P = 0.021) and the percentage of Cryptosporidium infected calves was lower on d 28 (P = 0.025) and 56 (P = 0.019). The PROPH calves had higher total counts for ruminal volatile fatty acids (P ≤ 0.05), bacteria and protozoa (P < 0.001). The PROPH treatment resulted in the highest concentrations of blood insulin-like growth factor-I and β-hydroxybutyrate (P ≤ 0.05) for the 29 to 56 day period and the entire experimental period. In conclusion, adding the combination of probiotics and phytobiotics as feed additive to diet of dairy calves during the preweaning period can improve health, performance, rumen fermentation and biochemical blood indices. However, the dietary inclusion of phytobiotic with rosmarinic acid as the main bioactive component or probiotic as a single feed additive does not affect growth performance and physiology indices.