Effect of supplementation with algae ß-glucans on performance, health, and blood metabolites of Holstein dairy calves.

Studies have shown that ß-glucans extracted from the cell wall of cereals, algae, and yeasts have been associated with improved immune function. However, it is unknown whether algae ß-glucan supplementation affects the performance, blood metabolites, or cell counts of immune cells in dairy calves. The objective of this randomized clinical trial was to evaluate whether supplementation of ß-glucans to milk replacer in dairy calves fed 6 L/d improved growth performance and fecal status and altered the blood metabolite profile. In this trial, we enrolled Holstein calves (n = 34) at birth (body weight 36.38 ± 1.33 kg; mean ± standard deviation) to receive, from 1 d of age, either 2 g/d algae ß-glucans mixed into 6 L/d of milk replacer (22.4% crude protein and 16.2% fat) or an unsupplemented milk replacer (control). The calves were blocked in pairs according to birth weight, sex, and date of birth (up to 5 d difference). Calves were housed individually, and calf starter (24.7% crude protein and 13.9% neutral detergent fiber) was offered ad libitum based on orts of the previous day until 56 d of age (end of the trial). Body weight was measured weekly, and health checks and daily fecal consistency were evaluated daily in every calf by the same observer. Calves with 2 consecutive days of loose feces that sifted through bedding were considered diarrhea positive. We used a linear mixed effects model to evaluate the effects of ß-glucan supplementation fed during the preweaning period on performance (average daily gain), final weight, feed efficiency (FE), white blood cell count, and selected blood metabolites, repeated by time. A generalized linear mixed effects model was also run to evaluate the likelihood of a diarrhea bout in the first 28 d of life, controlling for the calf as the subject with a logistic distribution. We included age, serum total protein at 48 h, and birth weight as covariates. At 56 d, ß-glucan-supplemented calves weighed more than control calves (56.3 vs. 51.5 kg). Treatment had no effect on total starter intake, but there was a treatment by age interaction for FE, with greater FE for ß-glucan-supplemented calves in wk 3 and 5 of age. There was only a tendency for average daily gain to be greater in supplemented calves than in control calves for the duration of the study. Furthermore, control calves had 14.66 [95% confidence interval (95% CI): 9.87-21.77] times greater odds of having a diarrheal bout than ß-glucan-supplemented calves. Control calves had 12.70 (95% CI: 8.82-18.28) times greater odds of having an additional day with an abnormal fecal score compared with ß-glucan-supplemented calves, suggesting that supplementation ameliorated diarrhea severity. We found no association of treatment with concentrations of serum total protein, albumin, creatinine, or glucose during the preweaning period. Our findings suggest that dietary supplementation of 2 g/d of algae ß-glucans to milk replacer improved fecal status and may affect growth, as evidenced by a higher weaning weight, compared with control calves. Future studies should explore the effect of algae ß-glucans on lower-gut physiology and digestibility in dairy calves.

População de protozoários ruminais em novilhos zebuínos alimentados com ou sem volumoso / Population of Protozoa in zebu steers fed with or without bulk

This study aimed to quantify and identify the profile of the rumen protozoa population of beef steers fed with or without roughage. Nellore crossbred steers raised in extensive system on lignified tropical pastures with mineral supplementation and steers confined for 60 days only receiving pelletized concentrate and whole corn kernels were evaluated. After slaughter, rumen fluid was collected and one ml aliquots were diluted in nine ml formaldehyde solution at 10%. The counts of small, medium and large protozoa were held in Sedgewick Rafter chambers and identification of genus was possible after staining lugol and optical microscope with a 40X objective. The concentration of rumen protozoa positively correlated with pH ruminal. Cattle fed without roughage had significantly lower rumen protozoa population (P<0.05). Animals fed roughage had higher occurrence of Dasytrichia genus, Charonina, Entodinum, Diplodinium, Ostracodinium and Epidinium while those fed without bulk, the Buetschilia, Isotricha, Eodinium, Polyplastron, Elyplastron, Metadinium and Enoploplastron were the most frequent genus.(AU)