The large animal model has gradually become an essential part of preclinical research studies, relating to exploring the disease pathological mechanism, genic function, pharmacy, and other subjects. Although the mouse model has already been widely accepted in clinical experiments, the need for finding an animal model with high similarity compared with a human model is urgent due to the different body functions and systems between mice and humans. The pig is an optimal choice for replacement. Therefore, enhancing the production of pigs used for models is an important part of the large animal model as well. Transgenic pigs show superiority in pig model creation because of the progress in genetic engineering. Successful cases of transgenic pig models occur in the clinical field of metabolic diseases, neurodegenerative diseases, and genetic diseases. In addition, the choice of pig breed influences the effort and efficiency of reproduction, and the mini pig has relative obvious advantages in pig model production. Indeed, pig models in these diseases provide great value in studies of their causes and treatments, especially at the genetic level. This review briefly outlines the method used to create transgenic pigs and species of producing transgenic pigs and provides an overview of their applications on different diseases and limitations for present pig model developments.
The objective of this study was to compare the plant extract from Picrasma quassioides (EPQ), yeast culture and monensin on in vitro rumen fermentation characteristics of wheat starch. Compared with the control (no additive), EPQ decreased the dry matter digestibility and the total VFA production (P<0.05), and increased the ratio of acetate and propionate. Both EPQ and yeast culture increased the fi nal rumen pH (P<0.05), but monensin had a negative effect on decline of rumen pH. In conclusion, the addition of EPQ can effi ciently retard rumen fermentation rate of wheat starch in vitro, and increase the fi nal pH of ruminal fl uid.
Background: Because of disadvantages of excessive dietary crude protein (CP), decreasing dietary CP of dairy cows has attracted the worldwide attention. Rumen protected methionine (RPM) supplementation can allow lower CP diets and is beneficial to milk production performance, N efficiency of cows and environment. The aim of this study was to evaluate the effects of reducing dietary CP and supplementing RPM on production, digestibility of nutrients, blood parameters, ruminal metabolites and economic effectiveness in lactating Holstein dairy cows. Results: A total of 96 lactating cows (63 ± 25 d in milk; 34.4 ± 5.74 kg/d of milk production; mean ± SD) were randomly assigned to 1 of 2 treatments: diet containing 17.3% CP without RPM (control group; CON; n = 49); diet containing 16.4% CP with supplementing 15.0 g/d of RPM (treatment group; RPM; n = 47). No effect was observed of reducing dietary CP on milk yield and milk composition. The apparent digestibility of nutrients was similar between treatments. The results related to blood showed that cows in RPM group exhibited lower concentration of blood urea nitrogen than that in CON group (P < 0.001). Moreover, there were no differences between treatments on concentrations of aspartate transaminase, alanine transaminase, alkaline phosphatase, globulin and albumin. In ruminal metabolites, microbial crude protein (MCP) of dairy cows in RPM group was higher compared with CON group (P = 0.006). Ruminal volatile fatty acid (VFA) contents were not changed by treatments except that the concentrations of butyrate and isovalerate of RPM group were higher than that of CON group at 2 h after feeding (P < 0.05). In addition, supplying the diet of 16.4% CP with RPM supplementation to cows could reduce feeding cost by 0.5 $/d per cow and boost net profits. Conclusions: Lower dietary CP with RPM supplementation did not limit milk yield, milk composition and apparent digestibility of nutrients, and could improve nitrogen utilization of dairy cows and synthesis of MCP in rumen, change VFA production at 2 h after feeding, as well as boost the economic benefits of the dairy farms.
The aim of the present study was to evaluate the effects of reducing dietary crude protein (CP) levels and supplementing rumen-protected methionine (RPM) on production, apparent digestibility of nutrients and economic effectiveness of lactating Holstein cows. A total of 96 (60 ± 7 d in milk; 34.39 ± 5.74 kg/d of milk production; mean ± SD) lactating Holstein dairy cows were randomly assigned to 1 of 2 treatments: diet containing 17.3% CP without RPM (control group; CON); diet containing 16.4% CP with supplementing 15.0 g/d of RPM (treatment group; RPM). All the data were analyzed using one-way analysis of variance (ANOVA) of SAS (SAS version 9.2, SAS Institute Inc., Cary, NC.). No effects were observed of reducing dietary CP on somatic cell counts, milk yield and milk composition including fat, protein, lactose, total solid, solids-not-fat and milk urea nitrogen. The total apparent digestibility of nutrients was similar between treatments, while RPM group had higher calcium digestion (44.24% vs. 42.75% ± 10.13%) and phosphorus digestion (48.50% vs. 45.96% ± 12.90%) numerically. In addition, supplying the diet of 16.4% CP with RPM supplementation to cows could reduce feeding cost by 0.5 $/d per cow and boost net profits. In conclusion, lower dietary CP with RPM supplementation did not limit milk yield, milk composition and apparent digestibility of nutrients, and also could improve the economic benefits of the dairy farms.
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