Introduction: Many agricultural by-products are relatively high in fiber and are particularly suitable for feeding ruminants. Fibrous by-products have a smaller particle size than most forages, but can have a higher energy value than most forages, due to their high fermentable fiber content. The use of non-forage fiber sources can have a significant effect on the protein components of the diet. Tomato pulp is a by-product of the paste industry, which, depending on the processing method and characteristics of raw tomatoes, contains varying proportions of skin, seeds, and small amounts of tomato flesh. In Iran, about 81,000 tons of wet tomato pulp are produced annually, which can cause environmental pollution. The present study was conducted to investigate the effect of different levels of tomato pomace powder (TPP) on ruminal fermentation and blood parameters of Holstein calves.
Materials and Methods: This experiment was carried out using 30 Holstein calves (average weight: 39.7±0.2 kg) based on a completely-randomized design with 3 treatment groups including 10 individual pens per each dietary treatment. Dietary treatments consisted of 1) pelleted starter (control group), 2) pelleted starter + 7.5% TPP, 3) pelleted starter +15% TPP. Calves were fed 4 liters of colostrum in the first three days of life, 5 liters of milk twice daily from 4 to 50 days of age, and 2.5 liters of milk once daily from 50 to 55 days of age. Milk replacer consumption was stopped at 56 days of age in all calves. Calves had free access to water and starter feed from 3 days of age. Calves were kept in individual stalls on straw bedding, and bedding was changed and cleaned daily. The health of the calves in the present study was continuously assessed daily for the occurrence of diarrhea, pneumonia, and bloat. The possible effect of treatments on the health of calves was assessed daily for all calves in terms of fecal scores. Rumen fluid was sampled using an esophageal tube and a vacuum pump about 3 hours after morning feeding. Blood sampling was done with the help of vacuum tubes, at the ages of 35 and 70 days, from 6 calves in each treatment, 3 hours after morning feed. The obtained data were analyzed by SAS software and Mixed procedure. A significant level of P<0.05 was considered.
Results and Discussion: The highest rumen pH after weaning was in the treatment containing 15% TPP, and this treatment showed a significant difference compared to the control treatment (P = 0.009). The treatment containing 15% tomato pomace had the highest and the control treatment the lowest rumen ammonia nitrogen concentration (P=0.04). According to the results, the concentration of ammonia nitrogen at 70 days of age was affected by the treatments (P=0.05). It seems that the simultaneous consumption of tomato pulp and pellet diet increases the flow of saliva to the rumen through more initial chewing and then earlier rumination, resulting in more urea released through saliva, which caused an increase in rumen ammonia nitrogen.The treatment containing 15% tomato pomace had the highest and the control treatment had the lowest number of lymphocytes among the treatments (P < 0.05). In this study, the stool score of calves fed tomato pulp in the starter diet (higher fiber content) was lower than that of the control group (low fiber content). It is likely that treatments containing tomato pulp, due to their high fiber content, have been able to affect the activity of chewing, rumination, and subsequent salivation, leading to an increase in rumen pH. Also, the decrease in pH in the pellet treatment is due to the heat that the pellet has received during the pelleting process, which causes faster and greater decomposition of starch in the rumen and faster production of volatile fatty acids, followed by a decrease in the absorption of the produced volatile fatty acids.
Conclusion: The presence of tomato pulp in the pellet diet reduced non-nutritive behaviors and increased the time spent on feeding actions such as rumination and eating. Regarding health indicators, tomato pulp consumption led to an improvement in fecal score compared to the control treatment. Blood analyses performed in this study showed that the 15% tomato pulp treatment had the lowest serum cholesterol and LDL levels. Given the high lymphocyte count in the blood of calves consuming tomato pulp, lycopene and vitamin C in tomato pulp can have a positive effect on the immune system of Holstein calves. |
