THE EFFECT OF PRICKLY PEAR MEAL AND PROBIOTICS ON DAIRY CALF PERFORMANCE AND CONTROL OF DIGESTIVE PATHOGENS.

Newborn calves are generally more susceptible to intestinal diseases, because of their immature and developing immune systems. In addition, the balance of intestinal microbes in calves is primitive, leading to diarrhoea and a series of diseases, if no proper management practices are incorporated into the production system. A number of enterobacteria can cause diarrhoea. To combat, large quantities of antibiotics, in conjunction with electrolyte therapy, are normally used to reduce calf mortality rates. However, due to the global concern against the extensive use and misuse of antibiotics, the use of probiotics and growth-promoting substances (GPS) as alternatives to antibiotics is been promoted and investigated. Probiotics stimulate intestinal goblet cell mucus production, which lubricates the intestinal epithelium and protects the host animal from invasion and colonisation by pathogens. Instead of antibiotics, natural antimicrobial feed additives, particularly plant extracts, can be considered as GPS; an example in South Africa being Opuntia ficus-indica, commonly known as prickly pear. Prickly pear is rich in amino acids, polyphenols, and polyunsaturated fatty acids, as well as in vitamins, compounds, and derivatives with biologically relevant activities. These activities include anti-inflammatory, antimicrobial, antioxidant, hypoglycaemic, and neuroprotective properties. To study the effect of a probiotic and prickly pear, the objective of the study cited was to evaluate the effects of dietary Lactobacillus and spineless cactus (prickly pear) powder (CACP) supplementation on calf growth performance, as well as on the prevalence of selected faecal pathogens (Escherichia coli and Enterobacteriaceae), in female Holstein dairy calves.

Prickly pear leaves were harvested, sun-dried for 14 days, and oven-dried at 105 °C, before being grinded into a powder. Twenty-four female Holstein dairy calves (39.03 ± 0.75 kg live weight) were randomly assigned to each of four treatment groups. The four treatments were: T1: the control group, calves fed a basal diet (milk plus calf starter meal), without supplementation; T2: calves fed the basal diet plus Lactobacillus at 5 g/day; T3: calves fed the basal diet plus prickly pear powder at 2.5 g/day; and T4: calves fed the basal diet plus prickly pear powder at 5 g/day. These treatments were applied from four days of age until weaning. Calf starter feed and clean water were provided ad libitum for the entire study period. Calf performance was measured in terms of feed dry matter intake (DMI), weaning weight, average daily gain (ADG) and feed conversion ratio (FCR), whereas faecal samples were analysed regularly for counts of total coliforms, E. coli and Enterobacteriaceae.

The dietary treatments apart from DMI, compared to Control, significantly affected all parameters: Weaning weight (kg) (T1 = 58.0^a, T2 = 62.0^b, T3 = 60.3^b and T4 = 61.3^b); ADG (kg/day) (T1 = 0.44^a , T2 = 0.54^b, T3 = 0.52^b and T4 = 0.51^b); FCR (kg/kg) (T1 = 0.87^a, T2 = 0.67^b, T3 = 0.65^b and T4 = 0.68^b); faecal pathogen counts (x10⁸) at day 10: total coliforms (T1 = 3.75^a, T2 = 1.8^b, T3 = 1.9^b  and T 4 = 1.65^b); E. coli (T1 = 2.35^a, T2 = 1.25^b, T3 = 0.95^bc and T4 = 0.60^c); Enterobacteriaceae (T1 = 2.1^a, T2 = 0.9^bc, T3 = 1.4^ab and T4 = 0.4^c).

Conclusions: Dietary supplementation with Lactobacillus and prickly pear powder improved the weaning weight, ADG and FCR of the newborn dairy calves, and reduced the prevalence of all faecal pathogens at 10 days of age. Feeding 5.0 g prickly pear powder/day already reduced the faecal coliform, E. coli, and Enterobacteriaceae counts at five days of age. Thus, supplementation with a probiotic such as Lactobacillus and prickly pear powder should be useful in limiting diarrhoea and associated diseases before weaning.