| Yeast culture (YC) is a yeast fermented product obtained by specific procedure. Its main components are the yeast cells and intra-cellular metabolites. The oligosaccharides, amino acids, peptides, proteins, organic acids, vitamins, yeast sourced enzymes and other unknown growth factors in yeast culture could promote the beneficial bacteria growth, improve the host intestinal health and immune function. Researches on ruminants have shown that yeast culture is able to increase the anti-stress capability, in consequence to improve animal health. High temperature and humidity in summer could reduce the pig’s ADFI, cause reduction of immune system,productivity and result in huge economic loss. However, few information of yeast culture on increasing growth of growing-finishing pigs in summer was available. The trial was conducted to investigate effects of different level YC supplementation on growth performance, anti-oxidant capacity, serum hormone levels and carcass quality in growing-finishing pigs in summer. We aimed to provide a scientific and theoretical basis for the YC supplementation in the anti-stress capability. This thesis was conducted in the following three sections.In the first section, to investigate the effects of YC supplementation on growth performance and nutrient digestibility in growing-finishing pigs,300pigs (Duroc×Landrace xYorkshire) at the age of70days, with an average initial body weight of29.56±3.18kg, were randomly allotted to five treatments on the basis of body weight and gender. Every treatment had6replications with10pigs per replication. The trial period was95days, which was divided into two phases:growing phase(30kg-60kg)and finishing phase (60kg-slaughtered).The control fed with a basal corn-soybean meal diet, while treatment1,2,3and4fed with corn-soybean meal adding yeast culture with0.5g/kg DM, lg/kg DM,2g/kg DM and4g/kg DM respectively. The results revealed that comparing with C group, the average value and midvalue of growing phase’s body weight in T2, T3and T4group did not have a significant difference, but had a increasing tendency. So did that of finishing phase’s body weight in T2and T4group. Skewness of pig’s body weight in growing phase had a decreasing tendency, so did that of pig’s body weight in finishing phase excepting for T4group. It revealed that the regularity of pig’s body weight in the same group was improved (P>0.05). Meanwhile, YC supplementation improved ADG of T2and T4in growing phase (P>0.05) at some extent. Digestibility of crude protein and crude fat in T2, T3and T4increased, but did not had a significant difference (P>0.05). In growing phase, digestibility of crude fiber in T3and T4increased apparently16.7%and9.3%respective, which did not differ significantly comparing with C group. In conclusion, in growing phase, YC supplementation in diet could improve pig’ADG and regularity of pig’s body weight at some extent, increased digestibility of crude fiber apparently in consequence to supply more energy.In the second section, we aimed to investigate the effects of YC supplementation on relevant indicators parameters of redox state and serum hormone levels in growing-finishing pigs. The design of this experiment was the same with experiment1. One pig of each replication was slaughtered at35d and80d, to collectting blood for preparation of serum. At the end of the growing phase and finishing phase,one pig of C, T2)1g/kg DM YC) and T4(4g/kg DM YC) was randomly picked to slaughter, collectting liver of10%of tissue homogenate. We index of Cortisol, T3and T4in serum were tested by radioimmune assay, index activity of SOD, GSH-Px, content of MDA and total anti-oxidation capability in serum and liver were analyzed by commercial kits.The results showed that SOD activity in serum and liver of treatments tended to advance, in which SOD activity of treatment did not differ significantly (P>0.05). MDA in serum and liver of treatments tended to reduce, in which MDA of treatments were not significantly different (P>0.05). GSH-Px activity and T-AOC of treatments were not significantly different comparing with control group (P>0.05). Level of Cortisol and T4of treatments were not significantly different comparing with control group (P>0.05). T3was significantly higher than that of control group (P<0.01). In conclusion, YC supplementation could improve the ability of anti-oxidant enzymes and reduced the body’s production of oxides, which maintain the balance of the redox state and reduced the degree of oxidative damage to tissue. It can be effective alleviation the decline of thyroid function caused by lasting high temperature and humidity.In the third section, we aimed to investigate the effects of YC supplementation on carcass quality in growing-finishing pigs. The design of this experiment is the same as experiment1. At the end of the trail,one pig of C, T2(1g/kg DM YC)and T4(4g/kg DM YC)was randomly picked to slaughter. we detected pre-slaughter live weight, carcass weight,slaughter rate, pH45min and pH24h, back fat thickness, eye muscle area, meat color (L*, a*, b*), we also measured tenderness and drip loss of the corresponding parts of the psoas major and longissimus muscle tissue, collect longissimus muscle for their10%homogenate for detecting SOD, GSH-Px, MDA and total anti-oxidation capability of muscle. The results showed that pH45min and pH24h had no significant differences (P>0.05), but pH24h value in T2, T4is high than C group. Drip loss and backfat thickness were not significantly different (P>0.05), but T2and T4decreased comparing with C group, but tenderness increased. SOD activity in T2was significantly higher than that of T4(P<0.05), but which was not significantly different comparing with the control group (P>0.05), MDA concentrations were not significantly different, but which in T2and T4decreased comparing with C group (P>0.05), T-AOC and GSH-Px activity were lower than that of C group, but no significant difference (P>0.05). In conclusion, YC supplementation tended to improve carcass quality of growing-finishing pigs in summer.In the summer, considering the results of this experiment and feed costs, T2group(1g/kg DM YC) is the most conducive to the health, growth and economic of pigs. |
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