| چکیده انگلیسی مقاله |
Introduction: Stresses that a calf experiences in the first months after birth may damage the calf's immune system and cause many problems for the dairy farmer in the future. Despite management measures to provide ideal conditions for rearing, calves are always exposed to some pathogens. The use of antibiotics to prevent disease in livestock diets was banned by the European :union: in 2006 due to the emergence of resistant pathogenic bacteria and possible contamination of livestock products. Therefore, other substances such as probiotics, prebiotics, and symbiotics have replaced antibiotics. One of the most common and effective probiotics is yeast, which comes in various types and is used in animal feed. Another replacement components are phytochemicals, which are secondary metabolites produced by some plants that are active through biological pathways aimed at protecting against predator attack. Studies conducted over the past years have shown the beneficial effects of these biological compounds due to their antimicrobial activities and antioxidant effects. Among such compounds that can also contribute to the favorable development of microbial population in the calf rumen are phenolic compounds. Fresh pistachio hull is separated from the pistachio fruit during processing and has been discarded as pistachio waste for years, and is a cheap source of phenolic compounds. Pistachio and its hull are rich sources of phenolic, antioxidant, and anti-inflammatory compounds such as gallotannin, myristicin, gallic acid, and quercetin, and are among the 50 richest sources of phenolic compounds. Based on the above explanations, the present study was conducted to investigate the effect of yeast feeding and a phenolic source (pistachio shell) on performance, blood parameters, and the immune system of Holstein calves. Materials and methods: This research was conducted from January 2021 to late March 2021 at Pars Agriculture, Industry and Livestock Company located in Bile Savar, Ardabil Province, Iran. This study was conducted using 36 Holstein suckling calves (one to 15 days old) with an average body weight of 34±6 kg in a completely randomized design in a 3×2 factorial experiment with six treatments and six replications for 60 days. Experimental treatments included: 1. Control (no additive), 2. The group received two grams of Saccharomyces yeast per calf per day, 3. The group received four grams of Saccharomyces yeast per calf per day, 4. The group received 1800 mg of phenolic compounds per calf per day, 5. The group received two grams of Saccharomyces yeast and 1800 mg of phenolic compounds per calf per day, and 6. The group received four grams of Saccharomyces yeast and 1800 mg of phenolic compounds per calf per day. Feed intake, weight gain, daily weight gain, feed conversion ratio, blood parameters, skeletal parameters, Health indices, antioxidant indices, and liver enzymes were the experimental parameters. Results and discussion: The effect of yeast feeding and phenol source on weight gain was significant (P<0.01). Weight gain in treatments 3 and 5 was greater than other treatments. According to the results, none of the experimental treatments had a significant effect on blood parameters. However, the effect of the period on all parameters was significant (P<0.01), so that glucose, triglyceride, albumin, and total protein on day 60 of the rearing period were higher than on day 30. Based on the results, experimental treatments could not affect the concentration of alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, malondialdehyde, or total antioxidant capacity. However, the effect of period on all parameters was significant (P<0.01). The average effect of treatments on skeletal growth parameters, such as the distance between two pins, the distance between two hooks, and the chest circumference, was significant. The chest circumference in the control group was lower than that in other treatments. Furthermore, the ear condition and eye scores in the control group were better than those in other treatments. Conflicting results have been observed regarding the effect of Saccharomyces cerevisiae on calf health and performance, and it has been suggested that for calves with unsuccessful passive transmission, the possible antidiarrheal effect of Saccharomyces cerevisiae supplementation could help improve animal performance. In general, in most studies, yeast supplementation was effective in increasing feed intake, growth rate, and rumen development in calves. It has been stated that Saccharomyces cerevisiae improves animal health by improving digestive function and leads to improved growth and production performance. In addition to antimicrobial benefits, supplementation with plant extracts or secondary metabolites may provide palatability to low-quality or indigestible calf starters, further increasing feed intake and growth performance. This could be one of the reasons for the positive effect of the phenolic source on yield in the present study. Similar to the present study, other studies also reported that the use of pistachio by-products containing phenolic compounds and feeding the Saccharomyces cerevisiae yeast did not affect liver enzymes. The most consistent results of yeast supplementation are associated with a reduction in the incidence and severity of diarrhea. Calves with failed passive immune transfer who were fed Saccharomyces cerevisiae had fewer days of diarrhea. Meanwhile, in a study, gallic acid, a bioactive phenolic compound, improved health and antioxidant status as an alternative to antibiotics, and showed anti-inflammatory and antibacterial properties. It is clear that these beneficial effects on health lead to increased profitability, even without improved growth performance due to reduced breeding costs. Conclusions: Considering the positive effects on feed intake, daily weight gain, feed conversion ratio, and some skeletal growth parameters and the absence of negative effects on blood parameters observed in the present study, the use of yeast supplement and phenolic source at two grams and 1800 mg, respectively, is recommended for use in lactating Holstein calves. |