The effects of low doses of Senna occidentalis seeds on broiler chickens

The effects of 0.5%, 0.3% and 0.1% w/w concentrations of Senna occidentalis (So) seed mixed with commercial ration were studied in 18 groups of 32 broiler chicks each, from 1 day to 49 days of age. Three groups were fed one of the rations throughout their lives (TL). Three other groups were fed one of the rations from the 1st to the 28th day of life (starter phase, SP), and the final 3 groups were fed one of the rations from the 29th to 49th day (finisher phase, FP). Each experimental group was matched by a control group fed the same diet over the same period but without the inclusion of So. All the animals were killed at 49 days of age, and blood was collected from 10 birds in each group for biochemical studies (ALT, AST, GGT, LDH, UA). A complete necropsy was performed on 3 birds from each group. No significant differences in the biochemical parameters in the serum were found between the control and experimental chicks, but animals treated with 0.5% So in groups FP and TL, gained less weight and chicks that received 0.3% So or 0.5% So in the ration throughout life (TL) had a larger feed conversion ratio. Besides this, degenerative changes were found in the striated skeletal muscle in the chest, in the myocardium and in the liver in the animals that received the higher concentrations of So seeds.     

精料补充料在家兔日粮中的应用研究

选择35日龄左右、健康无病的齐卡大型白兔120只,随机分为4组,分别饲喂全价饲料和3种不同营养水平的精料补充料,观察其采食量、日增重和成活率。结果表明:饲喂青草加精料补充料较饲喂全价饲料成本低。而精料补充料以消化能12.76MJ/kg、粗蛋白19.28%、粗纤维6.21%的营养水平饲喂效果最佳。     

二甲酸钾对肉仔鸡的抗菌促生长作用研究

将120只1日龄雏鸡随机分为3组,饲养21d,比较二甲酸钾和黄霉素对肉仔鸡生产性能、肠道菌群和pH值的影响。结果表明:1)日粮中添加4.5g/kg二甲酸钾显著降低嗉囊和肌胃内容物的pH值,且显著降低盲肠乳酸杆菌和大肠杆菌数量,两者之间的比例也显著提高(P<0.05)。2)日粮中添加4.5g/kg二甲酸钾显著提高肉鸡的日增重(ADG)和饲料报酬(P<0.05),达到与黄霉素同等的效果(P>0.05)。     

贵州黄牛杂交F1代直线育肥技术研究

本试验采用6月龄左右的西门塔尔×关岭牛F1代10头、利木赞×关岭牛F1代10头、安格斯×关岭牛F1代10头进行了360 d的强度育肥饲养试验。结果表明，3种杂交牛平均体重分别为550、590、540 kg，平均日增重依序为1413、1485和1367g；每千克增重消耗饲料干物质分别为6.91、6.42、7.10 kg；每增重1 kg饲料成本分别为5.23、4.86、5.38元；净肉率差异不显著，分别为42.5 %、41.5 %和43.0 %。从而认为，贵州杂交黄牛通过直线育肥可以达到优质肉牛18～24月龄（即屠宰前）450～500 kg以上的生产性能。     

Effects on animal performance and sward composition of mixed and sequential grazing of permanent pasture by cattle and sheep

Previous experiments have shown that mixed or conjoint grazing, when two or more animal species are grazed together, can lead to improved performance of one or more of the species and a higher total output per unit area. Sequential grazing systems, when different animal species graze an area in succession, also have the potential to improve productivity. This experiment directly compared these two approaches for integrating the grazing of cattle and sheep when pastured on improved permanent pasture. Four treatments were compared: 1) sheep only from May to October (S/S); 2) cattle only from May to July followed by sheep only from August to October (C/S); 3) cattle and sheep from May to July, sheep only for the rest of the growing season (C + S/S); and 4) cattle and sheep from May to October (C + S/C + S). Each treatment was replicated three times. From May until weaning at the end of July the plots were grazed by steers and ewes and lambs, and from weaning until October by steers and lambs. Sward heights were maintained at 6 cm using a “put and take” stocking system. Animal performance and sward composition data were collected during three growing seasons, 2001–2003. During the pre-weaning period lambs grazing plots which were grazed only by sheep had significantly poorer growth rates than those grazing plots where there was mixed grazing. Lambs grazing the sheep only plots also had lower liveweight gain during the post-weaning period, with the highest growth rates being recorded on the C + S/C + S treatment. Carrying capacity and total liveweight gain per unit area post-weaning were also consistently higher for the C + S/C + S treatment, while carrying capacity pre-weaning was highest for the C/S treatment. Measurements of clover content in the grazed horizon and botanical separation of material from quadrat cuts indicated that even under relatively controlled conditions choice of grazing system can influence sward composition. However, there was no clear link between any single sward change and the growth of the animals, indicating that the improved performance of cattle and sheep under mixed grazing is the result of a combination of factors, rather than a response to a particular sward parameter.     

Comparison of genetic improvement for litter size at birth by direct and indirect selection in swine herd

Responses to selection for number of piglets born alive (NBA) by the total number of piglets born (TNB), the NBA, and the NBA plus number of piglets born dead (NBD) were compared using the accuracy of selection and expected genetic gain calculated from the selection index with family information and the real response to selection, using data generated by Monte Carlo computer simulation. The accuracy of selection for NBA selected by TNB was higher than that by NBA only if the genetic correlation between TNB and NBA was close to 1.0, or the value of heritability for the TNB was much larger than that for the NBA. The accuracy of selection for the NBA selected by the combination of the TNB and the NBA was generally highest in the three selection methods in each family structure. Selection by the TNB resulted in the greatest expected genetic gain for the TNB among the selection methods. In the best linear unbiased prediction (BLUP) selection, the genetic gain for the NBA accumulated by the NBA tended to be similar to that accumulated by the combination of the NBA and the NBD, and both genetic gains at generation 10 were significantly larger than that by the TNB (P < 0.001). The accumulated responses selected by the two‐trait animal model BLUP estimated from genetic parameters with errors were similar to those estimated from the true parameters, and there was no significant difference between them. These results indicate that selection by the NBA or by the NBA and the NBD gives more genetic improvement in the NBA than that by the TNB.     

Tree improvement effects on tree size distributions for Picea glauca and Picea mariana in New Brunswick,Canada

Abstract

Height and diameter distributions between improved and unimproved (checklot) seedlots for white spruce [Picea glauca (Moench) Voss] and black spruce [Picea mariana (Mill.) BSP] were compared using the two-parameter Weibull function. Individual tree height at age 5–15 years and diameter at breast height at age 15 years that were collected from two series of large-plot realized gain tests were used for this purpose. For both species, improved seedlots did not significantly (α=0.05) change the shape parameter of the distributions relative to their checklots, suggesting that an overall shape value will be adequate to predict tree size distributions of various improved seedlots. The most important finding was that seedlot influenced the scale parameter (related to the range of the distribution) significantly, but from a practical viewpoint, only those scale values of the higher rated seedlots (i.e. seedlots collected from a rogued seed orchard or superior families) were significantly higher (α=0.05) than those of the respective unimproved seedlot. The changes in scale value of the alternative improved seedlots relative to the checklot (Δ_Scale) were comparable in magnitude to the respective realized genetic gains, suggesting that tree improvement effects on the scale value can be adjusted by realized genetic gains. The results also suggest that site and age significantly affected the scale value; in general, Δ_Scale became larger at earlier ages or on better sites. The findings reported here will be used in the development of yield functions for genetically improved white and black spruce in New Brunswick.     

羔羊30日龄早期断乳及代乳料研究

［目的］提高羊只的生产性能。［方法］根据母羊的泌乳曲线和羔羊的生长发育规律，配制标准营养水平（试验1组）和低于标准营养水平15%（试验2组）的代乳料对30日龄羔羊进行早期断乳试验，以正常断乳（90日龄）为对照，比较不同试验组羔羊的日增重和饲料转化率及母羊的发情情况。［结果］试验1组和试验2组羔羊日增重和料重比均高于对照，30-90日龄2组羔羊的日增重分别为164.6、159.4 g，分别与对照（日增重118.7g）达到极显著和显著差异水平；试验1组和试验2组母羊发情较早，分别为51、54 d，对照组母羊平均发情期为66 d。［结论］羔羊早期断乳可使母羊的发情提早12-15 d。     

油松优树子代测定及遗传增益的初步研究

通过对５３０株油松优树子代林内８２９个家系（次）生长疸的测定，初步选出了较为优良的油松家系，并对不同来源的优树家系和单株的树高及地径的遗传率进行了估算。     

荷斯坦育肥牛日粮中添加碳酸氢钠的增重效果

荷斯坦育肥牛日粮中添加５０ｇ碳酸氢钠，观察增重效果，试验期５０ｄ。结果表明，试验组牛头均日增重比对照组提高１８．０％，差异显著。