The objective of this study was to investigate the effects of the level of metabolizable protein (MP) on milk production and nitrogen utilization in Chinese Holstein dairy cows. Forty multiparous dairy cows (body weight = 590 kg; days in milk = 135; average milk yield = 30.2 kg/d) were assigned to treatments randomly within groups based on days in milk and milk production. Animals were offered diets with different levels of MP: 8.3% (diet A), 8.9% (diet B), 9.7% (diet C), and 10.4% (diet D) of dry matter. The MP level in diet A was designed to meet the current Chinese National Station of Animal Production and Health guidelines, whereas that in diet D was based on the National Research Council (2001) model. The experiment lasted for 7 wk. Milk yield and milk composition (fat, protein, and lactose) were recorded, and urea nitrogen concentrations in serum, urine, and milk were measured during the experiment. Milk yield and milk protein percentage increased as the MP increased up to 9.7% of dry matter, and then leveled off. Concentrations of nitrogen in urine, serum, and milk increased linearly as the amount of MP was increased, indicating decreased efficiency of nitrogen utilization. Milk lactose percentage and total solids percentage showed no significant differences among the 4 diets. We concluded that the optimal dietary MP level was at 9.6% of dry matter for Chinese Holstein dairy cows producing 30 kg of milk per day.

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This trial was conducted to investigate the effects of supplementary quercetin on growth performance, serum lipids levels and whole fish body composition in tilapia (Oreochromis niloticus). Four hundred fish were randomly divided into five treatment groups with four replicates in each group and 20 fish in each replicate. The dietary quercetin levels of the five treatment groups were: 0 (control group), 200, 400, 800, and 1600 mg/kg, respectively; the trial period was 7 weeks. Compared with the control group, specific growth rate and condition factor of quercetin groups were improved significantly (P<0.05). No significant differences in feed conversion rate and survival rate were found between the control group and all quercetin groups (P>0.05). The triglyceride concentration in serum was decreased significantly with the increasing levels of quercetin supplementation (P<0.05), while the highdensity lipoprotein cholesterol concentration was increased significantly by the supplementation of quercetin (P<0.05). The significant difference of low-density lipoprotein cholesterol concentration was found only between control group and highest dietary quercetin level group (P<0.05). The levels of moisture, crude protein and crude lipid of whole fish body were significantly affected by the supplementation of quercetin (P<0.05), the ash levels of all groups were similar (P>0.05). In conclusion, we demonstrated a promotion of growth performance and the reduction of lipid levels in serum and whole fish body with the supplementation of quercetin.

Aims The aim of this study was to determine the intestinal microflora of Anguilla marmorata at different growth rates and to identify potential probiotic/pernicious bacteria. Methods and Results Bacterial communities from eight different eels' intestinal sites (including the intestinal contents and the intestinal mucosa) from three fish groups (three fast‐, two medium‐, and three stunted‐growth samples), two water samples, and one diet sample were characterized by Illumina next‐generation sequencing. The data revealed that the predominant genera (relative abundance of bacteria genera >1%) in the intestine of fast‐ and medium‐growth groups were Cetobacterium, Edwardsiella, Clostridium, Lactococcus, Bacteroides, Plesiomonas and Akkermansia. The dominant genus in the stunted‐growth group was Spiroplasma. Moreover, culture‐associated (water and feed) environmental microbes were distinct from those present in fish intestines, and included Flavobacterium (the dominant bacteria in water) and Corynebacterium (the dominant bacteria in feed). Conclusions Only minor differences in gut microbial communities were observed between the fast‐growth group and the medium‐growth group; however, significant differences were observed between the normal‐growth group (including the fast‐growth group and medium‐growth group, which showed uninhibited growth during the rearing stage) and the stunted‐growth group. Together, these data suggested that intestinal microbes were significantly associated with marbled eels’ growth rate. Significance and Impact of the Study In this study, we demonstrated for the first time, the intestinal bacterial communities of A. marmorata at different growth rates. Moreover, we found that the genus Spiroplasma was abundant in the guts of stunted‐growth eels, which had never been noticed. Such a finding indicates that the genus Spiroplasma plays a key role associated with retardation in growth and should be controlled to recover the growth of stunted eels, which is meaningful to farmers.

The economic loss of intestinal inflammation by histamine in diet has caused concern in eel culture; it is urgent to develop a natural feed additive to alleviate the negative effects of high-level dietary histamine. Oligomeric proanthocyanidins (OPCs), as the natural antioxidant to scavenge free radicals, were supplemented to alleviate the effects of dietary histamine on parameters of growth, serum biochemistry, and liver metabolites of juvenile American eels in the present study. Juvenile American eels with an initial body weight of 10.84 ± 0.16 g per fish were divided into a control group fed commercial diet, a HIS group fed commercial diet supplemented 300 mg/kg histamine, and an OPC group fed commercial diet supplemented 300 mg/kg histamine and 300 mg/kg OPC. The trial period was 11 weeks. Compared with the HIS group, the OPC group showed that dietary OPC supplementation could alleviate growth retardation; decrease activities of glutamic-pyruvic transaminase, glutamic-oxaloacetic transaminase, acid phosphatase, and alkaline phosphatase; and lower levels of immunoglobulin and complement 3 in serum. With the upregulation of L-cysteine and dihydrouracil involving cysteine and methionine metabolism, beta-alanine metabolism, sulfur metabolism, pantothenate and CoA biosynthesis, and pyrimidine metabolism in the liver, OPC supplementation could alleviate the effects of high-level dietary histamine on growth and serum biochemical parameters. There were no significant differences of growth performance and serum biochemical parameters between the HIS group and control group. These results indicated that OPC might act as a potential feed additive to effectively counteract the negative effects of dietary histamine on juvenile American eel.