Mycotoxins are fungal metabolites that occur in human foods and animal feeds, potentially threatening human and animal health. The intestine is considered as the first barrier against these external contaminants, and it consists of interconnected physical, chemical, immunological, and microbial barriers. In this context, based on in vitro, ex vivo, and in vivo models, we summarize the literature for compromised intestinal barrier issues caused by various mycotoxins, and we reviewed events related to disrupted intestinal integrity (physical barrier), thinned mucus layer (chemical barrier), imbalanced inflammatory factors (immunological barrier), and dysfunctional bacterial homeostasis (microbial barrier). We also provide important information on deoxynivalenol, a leading mycotoxin implicated in intestinal dysfunction, and other adverse intestinal effects induced by other mycotoxins, including aflatoxins and ochratoxin A. In addition, intestinal perturbations caused by mycotoxins may also contribute to the development of mycotoxicosis, including human chronic intestinal inflammatory diseases. Therefore, we provide a clear understanding of compromised intestinal barrier induced by mycotoxins, with a view to potentially develop innovative strategies to prevent and treat mycotoxicosis. In addition, because of increased combinatorial interactions between mycotoxins, we explore the interactive effects of multiple mycotoxins in this review.

Due to the diversity and limitation of determination methods, published data on the fatty acid (FA) compositions of different milk samples have contributed to inaccurate comparisons. In this study, we developed a high-throughput gas chromatography-mass spectrometry method to determinate milk FA, and the proposed method had satisfactory linearity, sensitivity, accuracy, and precision. We also analyzed the FA compositions of 237 milk samples from Holstein cows, Jersey cows, buffalos, yaks, humans, goats, donkeys, and camels. Holstein, Jersey, goat, and buffalo milks contained high content of even-chain saturated FA, whereas goat milk had higher content of medium- and short-chain FA (MSCFA). Yak and camel milk are potential functional foods due to their high levels of odd- and branched-chain FA and low ratios of n-6 to n-3 polyunsaturated FA (PUFA). Human milk contained lower levels of saturated FA, MSCFA, and conjugated linoleic acid, and higher levels of monounsaturated FA and PUFA. As a special nonruminant milk, donkey milk contained low levels of monounsaturated FA and high levels of PUFA and MSCFA. Based on the FA profiles of 8 types of milk, nonruminant milk was distinct from ruminant milk, whereas camel and yak milk were different from other ruminant milks and considered as potential functional foods for balanced human diet.

Heat stress negatively impacts the health and milk production of dairy cows, and ruminal microbial populations play an important role in dairy cattle’s milk production. Currently there are no available studies that investigate heat stress-associated changes in the rumen microbiome of lactating dairy cattle. Improved understanding of the link between heat stress and the ruminal microbiome may be beneficial in developing strategies for relieving the influence of heat stress on ruminants by manipulating ruminal microbial composition. In this study, we investigated the ruminal bacterial composition and metabolites in heat stressed and non-heat stressed dairy cows. Eighteen lactating dairy cows were divided into two treatment groups, one with heat stress and one without heat stress. Dry matter intake was measured and rumen fluid from all cows in both groups was collected. The bacterial 16S rRNA genes in the ruminal fluid were sequenced, and the rumen pH and the lactate and acetate of the bacterial metabolites were quantified. Heat stress was associated with significantly decreased dry matter intake and milk production. Rumen pH and rumen acetate concentrations were significantly decreased in the heat stressed group, while ruminal lactate concentration increased. The influence of heat stress on the microbial bacterial community structure was minor. However, heat stress was associated with an increase in lactate producing bacteria (e.g., Streptococcus and unclassified Enterobacteriaceae), and with an increase in Ruminobacter, Treponema, and unclassified Bacteroidaceae, all of which utilize soluble carbohydrates as an energy source. The relative abundance of acetate-producing bacterium Acetobacter decreased during heat stress. We concluded that heat stress is associated with changes in ruminal bacterial composition and metabolites, with more lactate and less acetate-producing species in the population, which potentially negatively affects milk production.

Milk spoilage is caused by the presence of proteolytic enzymes produced by Pseudomonas spp. during storage at low temperatures. The aim of this study was to identify Pseudomonas spp. in raw milk and investigate their associated proteolytic properties at low temperatures. Raw milk samples (n = 87) were collected from 87 bulk tanks in Shaanxi Province in China. Pseudomonas spp. were identified using Pseudomonas specific 16S, universal 16S rRNA sequencing, and rpoB gene sequencing. The proteolytic properties of Pseudomonas spp. were examined using milk agar, quantitative trinitrobenzenesulfonic acid (TNBS) assay, and by the presence of alkaline metallopeptidase gene (aprX). A total 143 isolates from all 87 samples were confirmed as Pseudomonas, and were identified as belonging to 14 Pseudomonas species. Of these, 40 (28.0%) isolates revealed proteolysis on milk agar at 2°C, 74 (51.8%) at 4°C, 104 (72.7%) at 7°C, and 102 (71.3%) at 10°C. However, proteolytic activity of 45 (31.5%) isolates exceeded 2 μmol of glycine equivalents per mL at 7°C, followed by 43 (30.1%) at 10°C, 18 (12.6%) at 4°C, and 7 (4.9%) at 2°C. The results reveal proteolytic activity of Pseudomonas spp. present in milk and their spoilage potential at different temperatures.

Staphylococcus aureus is one of the main pathogens involved in dairy cow mastitis. Monitoring of antibiotic use would prove useful to assess the risk of Staph. aureus in raw milk. The objective of this work was to investigate the prevalence of Staph. aureus strais isolated from raw milk in northern China, and to characterize antimicrobial susceptibility of these strains and their key virulence genes. In total, 195 raw milk samples were collected from 195 dairy farms located in 4 cities of northern China from May to September 2015. Out of 195 samples, 54 (27.7%) were positive for Staph. aureus. Among these 54 samples, 54 strains of Staph. aureus were isolated, and 16 strains were identified as methicillin-resistant Staph. aureus. The strains exhibited high percentages of resistance to penicillin G (85.2%), ampicillin (79.6%), and erythromycin (46.3%). Moreover, 72% of the strains showed resistance to more than one antimicrobial agent. Overall, 63% of penicillin-resistant strains possessed the blaZ gene, and 60% of the erythromycin-resistant strains possessed erm(A), erm(B), erm(C), msr(A), or msr(B) genes with 8 different gene patterns. All isolates resistant to gentamicin, kanamycin, and oxacillin carried the aac6'-aph2", ant(4')-Ia, and mecA genes, respectively. Two tet(M)-positive isolates carried specific genes of the Tn916-Tn1545 transposon. The most predominant virulence genes were sec, sea, and pvl, which encode staphylococcal enterotoxins (sec and sea) and Panton-Valentine leukocidin, respectively. Thirty-two isolates (59.2%) harbored one or more virulence genes. The majority of Staph. aureus strains were multidrug resistant and carried multiple virulence genes, which may pose a risk to public health. Our data indicated that antimicrobial resistance of Staph. aureus was prevalent in dairy herds in northern China, and that antibiotics, especially penicillin G and ampicillin, to treat mastitis caused by Staph. aureus should be used with caution in northern China.