Effect of milk fortified with natural honey on performance, digestibility, blood metabolites, and skeletal growth indices of suckling Holstein calves

Introduction: The management of suckling calves guarantees health and performance in their productive life. The sensitivity and low immune system in newborn calves increase the odds ratio of some disorder incidence and sometimes it is associated with the death. Therefore, the use of antibiotics in suckling calves became popular. Laws prohibiting the use of antibiotics in raising domestic animals led to the use of natural alternatives with similar properties. These compounds cause positive effects on the reduction of intestinal infections, and disorders and increase the absorption of nutrients by creating intestinal microbial balance. Prebiotics have the same feature that changes the microflora population in the digestive system. It has been proven honey has prebiotic characteristics that improve the immune system in mammals. This product and its by-products are used for different goals in human feed. This prevents intestinal infection, modifies intestine microflora population, and improves health situation and lipid metabolism. Honey is a natural product that is thickened from saturated or supersaturated sugar solutions. It usually consists of 17% water, 38% fructose, 31% glucose, 10% other sugars, and a wide range of micronutrients, vitamins, minerals, and amino acids, with a pH below 4. This study was conducted to evaluate the effect of milk enrichment with natural honey on the performance, digestibility, blood parameters, and skeletal growth indices of suckling Holstein calves. Materials and methods: Eighteen Holstein suckling male calves with an average weight of 58±4.2 kg were used. Treatments were divided into three groups which contained zero, 2.5, and five g per day of natural honey to the milk consumed. The duration of the experiment was 30 days evaluated in a completely randomized design. Calves were kept in individual pens and fed based on NRC requirements. Starter provided to total mixed ration (TMR) form which is given at 8:00 am and 4:00 pm daily. Calves fed milk based on 10% of body weight in the morning and evening. The amount of milk consumed by calves is measured, and to calculate the milk solids, it is multiplied by a coefficient of 12.5%. Dry matter (DM) digestibility, blood samples, average daily gain, dry matter intake, stool score, and skeleton growth were evaluated during 30 d and compared treatment by the general mixed model in SAS software. Results and discussion: The results of this study showed that adding natural honey to milk significantly improved the feed conversion ratio and increased the final weight, average daily gain, and dry matter digestibility of the calves (P<0.05). The group of calves that consumed five g of natural honey per day had the highest final weight and average daily gain, as well as the lowest feed conversion ratio. However, the milk and starter intakes were not affected by the experimental treatments, and there was no significant difference observed between the control group and the groups that received natural honey (P<0.05). Supplementing milk with honey improved the growth rate and feed conversion ratio of the calves, likely due to the presence of enzymes and other substances in honey that aid in breaking down polysaccharides into usable energy for the animals. Blood glucose concentration decreased in the calves that received natural honey (P<0.05), but the concentrations of cholesterol, triglyceride, high-density lipoprotein, low-density lipoprotein, and very low-density lipoprotein were not significantly different among the treatments (P>0.05). The reduction in blood glucose can be attributed to the antioxidant compounds present in honey, which can reduce intestinal glucose absorption by inhibiting the digestive enzymes of alpha-amylase or delaying the emptying of stomach contents into the small intestine. The stool consistency score increased with increasing levels of natural honey in the milk, and the group that received five g of natural honey per day had the best stool score, while the control group had the lowest stool consistency score (P<0.05). However, there was no effect of treatment on the number of animals with diarrhea or the number of days involved with diarrhea (P>0.05). Natural honey is rich in antioxidants and has prebiotic properties, which promote the growth of beneficial microorganisms and decrease harmful microflora in the gut. There was no significant difference observed in skeletal growth indices between the different experimental treatments (P>0.05). Conclusions: The experiment's findings indicated that incorporating natural honey (up to five g/day) into the milk given to Holstein calves can improve their performance and health, making it a recommended practice.