Abstract
We investigated the effect of diets containing organic zinc and a mixture of medicinal herbs on ruminal microbial fermentation and histopathology in lambs. Twenty-eight lambs were divided into four groups: unsupplemented animals (Control), animals supplemented with organic zinc (Zn, 70 mg Zn/kg diet), animals supplemented with a mixture of dry medicinal herbs (Herbs, 100 g dry matter (DM)/d) and animals supplemented with both zinc and herbs (Zn+Herbs). Each lamb was fed a basal diet composed of meadow hay (700 g DM/d) and barley (300 g DM/d). The herbs Fumaria officinalis L. (FO), Malva sylvestris L. (MS), Artemisia absinthium L. (AA) and Matricaria chamomilla L. (MC) were mixed in equal proportions. The lambs were slaughtered after 70 d. The ruminal contents were used to determine the parameters of fermentation in vitro and in vivo and to quantify the microbes by molecular and microscopic methods. Samples of fresh ruminal tissue were used for histopathological evaluation. Quantitative analyses of the bioactive compounds in FO, MS, AA, and MC identified 3.961, 0.654, 6.482, and 12.084 g/kg DM phenolic acids and 12.211, 6.479, 0.349, and 2.442 g/kg DM flavonoids, respectively. The alkaloid content in FO was 6.015 g/kg DM. The diets affected the levels of total gas, methane and n-butyrate in vitro (P < 0.046, < 0.001, and < 0.001, respectively). Relative quantification by real-time PCR indicated a lower total ruminal bacterial population in the lambs in the Zn and Zn+Herbs groups than the Control group (P < 0.05). The relative abundances of Ruminococcus albus, R. flavefaciens, Streptococcus bovis, and Butyrivibrio proteoclasticus shifted in the Zn group. Morphological observation found a focally mixed infiltration of inflammatory cells in the lamina propria of the rumen in the Zn+Herbs group. The effect of the organic zinc and the herbal mixture on the parameters of ruminal fermentation in vitro was not confirmed in vivo, perhaps because the ruminal microbiota of the lambs adapted to the zinc-supplemented diets. Long-term supplementation of a diet combining zinc and medicinal herbs, however, may negatively affect the health of the ruminal epithelium of lambs.
Highlights
The ruminal microbial fermentation of dietary substrates plays a main role in the ability of ruminants to use fibrous dietary substrates but is associated with emissions of methane and the excessive excretion of nitrogen in manure
We investigated the effects of dietary supplements containing organic zinc and a mixture of medicinal herbs (Fumaria officinalis L., Malva sylvestris L., Artemisia absinthium L., and Matricaria chamomilla L.) on ruminal fermentation, the microbial population and the histopathology of the lambs
The phytochemical substances in Fumaria officinalis L. (FO) consisted of 12.211 g/kg dry matter (DM) flavonoids, 3.961 g/kg DM phenolic acids (Table 2) and 6.015 g/kg DM alkaloids (Table 3)
Summary
The ruminal microbial fermentation of dietary substrates plays a main role in the ability of ruminants to use fibrous dietary substrates but is associated with emissions of methane and the excessive excretion of nitrogen in manure. Structural and regulatory roles for enzymes, proteins and transcription factors and is a key trace element for improving immunological functions [7, 8]. The bioavailability of zinc in the diets of ruminants depends on the chemical form, content and interaction of zinc with dietary constituents [9, 10]. The most recent requirements and recommendations for dietary zinc in ruminants vary between 40 and 130 mg/kg DM of the complete diet [11]. The organic forms of trace elements bound by organic ligands should be more resistant to interactions in the ruminant digestive tract and can be more bioavailable than inorganic sources [12]. Epithelial surfaces are complex chemical and biological barriers that prevent the invasion of microbes or other potentially harmful pathogens, but they harbor many beneficial microorganisms [14]
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