The effect of Yarrowia lipolytica culture on growth performance, ruminal fermentation and blood parameters of dairy calves

Yeast cultures have been widely investigated as feed additives to improve growth and health of animals. However, most of the research has focused on Saccharomyces cerevisiae products, whereas effects of non-conventional species such as Yarrowia lipolytica are not yet known. Y. lipolytica is a non-pathogenic yeast which can metabolize glycerol among other important industrial byproducts and is rich in fat and many other nutritional and bioactive compounds. The aim of the study was to investigate the effects of Y. lipolytica culture added to colostrum and milk replacer on reticuloruminal fermentation, biochemical blood indices, and growth rate of calves. During the first 56 d of life, 24 Polish Holstein-Friesian calves were grouped by sex (equal numbers of bulls and heifers) and parity (equal numbers of calves born to primiparous and multiparous cows) and assigned randomly to 2 treatments: yeast culture (YL, Y. lipolytica yeast, n = 12) or control (CON, without yeast additive, n = 12). Y. lipolytica yeast culture was incorporated into colostrum or milk replacer at a dosage of 30 g/d (15 g/feeding; 108 CFU/g). Calves fed YL had higher body weight on d 28 (P =  0.012) and on d 56 (P =  0.011). In the same group, higher average daily gain from d 3 to 28 (P =  0.012), from d 29 to 56 (P =  0.033), and for the entire experimental period (P =  0.011) were noted. From d 3 to 56, the YL increased changes in body length (P =  0.024), hip width (P =  0.029) and heart girth (P <  0.001). Calves fed YL had higher counts of Entodiniomorphida, Holotricha and total bacteria in reticulorumen (P < 0.001). Both age of calves and treatment affected all biochemical blood indices considered in this study with the exception of β-hydroxybutyrate (BHBA), which level did not change over time. In the YL group, lower level of blood Mg (P < 0.001) and higher blood concentrations of BHBA (P =  0.001), non-esterified fatty acids (P <  0.001), blood urea nitrogen on d 14 and 42 (P = 0.009), and Ca (P < 0.001) were noted. No effect of YL was observed on reticuloruminal fluid pH, and concentrations of ammonia nitrogen, total volatile fatty acids, acetate, propionate, butyrate and valerate, as well as acetate to propionate ratio (P >  0.05).