Abstract
Although many studies have confirmed that antimicrobial peptides (AMPs: PBD-mI and LUC-n) can be used as feed additives, there are few reports of their use in ruminants. The present study aimed to investigate the impact of AMPs on ameliorating rumen fermentation function and rumen microorganisms in goats. Eighteen 4-month-old Chuanzhong black goats were used in a 60-day experiment (6 goats per group). Group I was used as the control and was fed a basal diet, the group II were fed the basal diet supplemented with 2 g of AMPs [per goat/day] and group III were fed the basal diet supplemented 3 g of AMPs [per goat/day], respectively. Rumen fluid samples were collected at 0, 20 and 60 days. Bacterial 16S rRNA genes and ciliate protozoal 18S rRNA genes were amplified by PCR from DNA extracted from rumen samples. The amplicons were sequenced by Illumina MiSeq. Rumen fermentation parameters and digestive enzyme activities were also examined. Our results showed that dietary supplementation with AMPs increased the levels of the bacterial genera Fibrobacter, Anaerovibrio and Succiniclasticum and also increased the ciliates genus Ophryoscolex, but reduced the levels of the bacterial genera Selenomonas, Succinivibrio and Treponema, and the ciliate genera Polyplastron, Entodinium, Enoploplastron and Isotricha. Supplementation with AMPs increased the activities of xylanase, pectinase and lipase in the rumen, and also increased the concentrations of acetic acid, propionic acid and total volatile fatty acids. These changes were associated with improved growth performance in the goats. The results revealed that the goats fed AMPs showed improved rumen microbiota structures, altered ruminal fermentation, and improved efficiency regarding the utilization of feed; thereby indicating that AMPs can improve growth performance. AMPs are therefore suitable as feed additives in juvenile goats.
Highlights
The microbiota colonizing the rumen is an essential component of ruminant gastrointestinal tract(GIT)[1]
The antimicrobial peptides (AMPs) were composed of recombinant swine defensin PBD-mI (DHYICAKKGGTCNFSPCPLFNRIEGTCYSGKAKCCIR), the net charge was caculated using protein calculator v3.4, and a molecular mass of about 5.4 kDa was obtained through a codon-optimized protein corresponding to mature defensin cDNA that was expressed and purified in Pichia pastoris yeast[25], and a fly antibacterial peptide LUC-n (ATCDLLSGTGVKHSACAAHCLLRGNRGGYCNGRAICVCRN), the net charge was caculated using protein caculator v3.4(estimated charge at pH 7.00 = 4.2) and a molecular mass of approximately 21.18 kDa was obtained through complementary DNA libraries constructed from micro-dissected salivary glands in whole maggots, that underwent transposon-assisted signal trapping, a technique selected for the identifi-cation of secreted proteins[26], at a blending ratio of 1:1[14]
The development of AMPs into feed addictives has been hampered by their potential for toxic side effects, suboptimal efficacy, and, most notably, the lack of cost-effective production systems.The present study demonstrates the effect of AMPs on different rumen bacteria and ciliates in juvenile goats, which can provide a theoretical basis for the future as alternatives to antibiotic
Summary
The microbiota colonizing the rumen is an essential component of ruminant gastrointestinal tract(GIT)[1]. The microbial community in the rumen consists of bacteria (1010–1011 cells/ mL), methanogenic archaea (107–109 cells/mL), ciliate protozoa (104–106 cells/mL), anaerobic fungi (103–106 cells/mL) and bacteriophages (109–1010 particles/mL)[2]. A major function of the rumen microbiome is the fermentation of plant materials ingested by ruminant animals [3,4,5]. Rumen modulation is one of the most important methods for improving feed efficiency, ruminant health and performance in ruminant livestock production. Several antibiotic compounds, such as monensin, hainanmycin and virginiamycin, have been used to improve ruminal fermentation and the efficiency of nutrient utilization[6,7,8]. The overuse of antibiotics has raised concerns about product safety and environmental health, and the use of antibiotics as additives in animal feed is banned in the European Union (European Union, 2003)
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