论奶牛日粮结构与饲喂制度的最优化

作者以反刍动物最新营养与饲养研究成果为依据，针对当前奶牛饲养实践中存在的主要问题提出日粮配方及饲喂制度的最优化方案，以提高奶牛生产水平和经济效益。     

Mammary cell turnover in lactating ewes is modulated by changes of energy fuels

The study of cell turnover of mammary gland helps to gain understanding of the subtle modulation that largely determines milk production. To evaluate the effect of diet composition on cell turnover of mammary gland, pluriparous sheep were allotted to three experimental groups and fed from day 33 after lambing a control diet (BD), a high starch (HS) diet or a high fat (HF) diet. Biopsies of mammary gland tissue were collected at 50 days after lambing for in situ detection of cell death and RT-PCR analysis of bax, bcl-2, caspase-3 and GST expressions. Both apoptotic and proliferation indexes were significantly higher (P<0.05) in the BD group compared to HS and HF groups. The relative expressions of GST were significantly greater (P<0.05) in HF group compared to the BD and HS groups. There was a significant increase in the ratio of bcl-2 to bax mRNA in the HS and HF groups. Availability of energy substrates for mammary gland can interfere with the cell fate, modulating genes involved in the control of oxidative stress which, in turn, can indirectly regulate cell apoptosis and proliferation.     

Cooling and feeding strategies to reduce heat load of grain-fed beef cattle in intensive housing

Six Murray Grey × Hereford yearling steers were used to determine the effect of two cooling treatments (ENV) (day cooled (0600–1400) or night cooled (1400–2200), and two dietary treatments (DIET) – control (CON) no added fat or added fat (FAT) – on rectal temperature, respiration rate and dry matter intake (DMI). Cattle were exposed to 2 d of thermoneutral conditions followed by four hot days in a controlled climate facility. This was replicated 6 times. Steers were given a 10 d rest in outside pens between each replication. Sprinklers (2.84 L min^− 1; 5 min on, 20 min off) and fans (continuous; 2 m s^− 1) were used when ambient temperature (T_A) ≥ 28 °C. Rectal temperature (5 min intervals) and respiration rate (hourly) were measured for 12 × 24 h periods on hot days (2 per replication). Individual DMI over two time periods (PER) (period 1; 0600–1500, and period 2; 1500–0600) and daily metabolisable energy (ME) intakes were also recorded. Steers fed FAT had greater (P < 0.05) DMI then the CON steers during day cooling. However, there were no DIET or PER differences for DMI during night cooling. DMI of FAT and CON fed steers during night cooling was similar to the DMI of the FAT fed steers during day cooling. Overall DMI was greater during night cooling (DMI from both diets pooled). There were PER differences for DMI, with more (P < 0.05) feed consumed during period 2 irrespective of ENV or DIET. ME intake was 22.9% greater (P < 0.05) for the FAT fed steers during day cooling then for the CON fed steers. There were no DIET effects on ME intake during night cooling. DIET had no effect (P > 0.05) on respiration rate however differences were seen for rectal temperature. Mean rectal temperature for the FAT steers was lower (P < 0.05) than the mean of the CON steers, however there were no within ENV differences. Day cooled cattle had a higher (P < 0.05) respiration rates (71.8 breaths/min; bpm) than the night cooled steers (65.3 bpm). There were no differences for rectal temperature. However, day cooled steers had lower (P < 0.05) rectal temperature and respiration rate than the night cooled steers during the day — which corresponded with the day cooling period. Night cooling appears to be beneficial in lowering mean rectal temperature and respiration rate, and in maintaining DMI. There is no suggestion that feeding fat will replace the need for supplementary measures to alleviate heat exposure of confined cattle. However feeding fat may be worthwhile in maintenance DMI when combined with strategies involving day cooling.     

Validation of the n-alkane and NIRS techniques to estimate intake, digestibility and diet composition in sheep fed mixed lucerne: ryegrass diets

An experiment was carried out with sixteen non-pregnant, non-lactating adult Rasa Aragonesa ewes fed different proportions of lucerne and ryegrass hays to validate the use of n-alkanes and NIRS methods to estimate diet composition, intake and digestibility. The effect of two different faecal sampling procedures (daily pool (S1) or rectal spot samples (S2)) was also tested. The faecal concentration of n-alkanes was affected by the sampling procedure, although differences were lower than 12%. Faecal recoveries were not affected by diet, except in the case of C₂₃ (P < 0.0001), C₂₈ (P = 0.0264) and C₃₃ (P = 0.0241), and followed a curvilinear pattern with alkane chain length. Recovery was complete in the case of C₂₉, C₃₁ and C₃₃, which countersigns the usefulness of these internal markers for digestibility and digestive flow studies (especially C₃₁, given its high concentration in most plants). The faecal recoveries of C₃₁ and C₃₂ were not similar, the assumption of identity affecting in an important way the reliability of intake estimates. The NIRS methodology appeared as a promising alternative for predicting diet composition (R² of the cross-validation = 0.98) and faecal concentration of most natural alkanes, although that was not the case for dosed alkanes. In all cases, the prediction equations obtained from the spectra of the faecal spot samples were better than those obtained from daily pool samples.     

Effect of calories restriction on ER stress in the liver of high fat diet rats

AIM: To study the effect of calories restriction on endoplasmic reticulum(ER) chaperone protein 78-kD glucose regulated protein (GRP78) mRNA expression in the liver of high fat diet rats, in order to explore the mechanism of how calories restriction improves insulin resistance. METHODS: Wistar rats (n=24) were randomly divided into 3 groups: normal chow (NC) group, was fed free normal chow (18.94% of calories as fat) for 12 weeks; high fat group (HF) was fed high fat diet (50.55% of calories as fat) for 12 weeks; calories restriction group (CR) was fed high fat diet for 8 weeks at first, then given 50% of diet consumed by the same age NC group. Changes of body weight, height, and food intake were recorded. At the end of experiment, HOMAIR, the rate of visceral fat (including perirenal fat and epididymal fat) vs weight, plasma protein, blood lipid (including total cholesterol and triglyceride), hepatic GRP78 mRNA and hepatic histological changes (including light microscopic studies and electron microscopic studies) were detected. RESULTS: (1) Animals in HF group had an obviously elevation of fasting insulin (27.51±3.51) mU/L vs (15.46±2.25) mU/L, triglyceride (1.35±0.25) mmol/L vs (0.67±0.10) mmol/L, total cholesterol (2.59±0.34) mmol/L vs (1.41±0.28) mmol/L and insulin resistance index HOMAIR (5.85±0.23 vs 2.85±0.60) compared with NC group, and also had obviously lipid accumulations in the liver. (2) After calories restriction, all the abnormal elevated biochemical indicators were decreased to normal levels, the hepatic lipid accumulations were also improved. (3) The changes of liver ultrastructure in HF group showed rough endoplasmic reticulum enlargement, fragmentation, taking off grain, and with glycogen solution. The changes in CR group were nearly the same as those in NC group. (4) High fat diet induced the expression of GRP78 mRNA, calories restriction might reverse it. CONCLUSION: Reasonable food calories restriction is a good method to improve insulin resistance, partly due to improvement of endoplasmic reticulum stress in liver.     

日粮对双向选择血浆极低密度脂蛋白肉鸡生长性能和血脂的影响

对７０８只（公，母各半）５～９周龄选择一个世代的高、低脂蛋白（ＶＬＤＬ）系鸡进行不同代谢能水平、粗蛋白水平的两个品系３因子交叉的遗传－营养互作试验，以探讨品系与日粮互作对肉鸡生长性能和血脂的影响。品系、日粮粗蛋白质和代谢能间的互作对９周龄血浆极低密度脂蛋白（ＶＬＤＬ）、甘油三酯及总脂浓度有显著影响（Ｐ＜０．０１），而对血浆胆固醇浓度无明显影响。高ＶＬＤＬ系血浆ＶＬＤＬ浓度（Ｏ．Ｄ．）有随日粮粗蛋白水平的升高而降低之趋势，而低ＶＬＤＬ系无此规律。高ＶＬＤＬ系血浆总脂浓度随日粮蛋白水平的升高而降低（Ｐ＜０．０００１），而蛋白水平对低ＶＬＤＬ系血浆总脂浓度无明显影响。低ＶＬＤＬ系血浆ＶＬＤＬ浓度（Ｏ．Ｄ．）随日粮代谢能水平的升高而降低（Ｐ＜０．０００１），而高ＶＬＤＬ系无此规律。高ＶＬＤＬ系血浆甘油三脂浓度随日代谢能水平的升高而升高，而低ＶＬＤＬ系无此规律。高ＶＬＤＬ系血浆总脂浓度随日粮代谢能水平的升高而升高，而代谢能水平对低ＶＬＤＬ系血浆总脂浓度无明显影响。血浆甘油三酯和胆固醇浓度存在品系－性别互作效应（Ｐ＜０．０１，Ｐ＜０．０５）；性别与日粮蛋白水平互作对血浆ＶＬＤＬ、胆固醇和总脂浓度均有显著影响（Ｐ＜０．０     

六盘山肉牛秋季舍饲育肥效果试验

选择不同日粮类型肉牛养殖户10户,参试生长公牛25头,参照肉牛营养需要和饲养标准,设计不同饲粮组合类型及日粮配方.随机分为6组,试验1、2、3组按设计标准配制日粮饲养,4、5、6组(CK)按传统方法饲喂,同期进行育肥试验.结果表明,试验1、2、3组头均日增体质量效果均比4、5、6组(CK)有明显提高.其中,试验1组期内平均日增体质量分别比试验4、5、6组(CK)提高94.22%、117.18%和145.07%(P＜0.01).     

尿素及丝兰提取物对黄羽肉鸡生长性能影响的研究

[目的]为提高肉鸡生长速度提供技术参考。[方法]通过在黄羽肉鸡饲粮中添加0.10%尿素及0.01%丝兰提取物,研究尿素和丝兰提取物对黄羽肉鸡生长性能的影响。[结果]日粮单独添加0.10%尿素或单独添加0.01%丝兰提取物都可以提高黄羽肉鸡的日增重,降低料肉比,但效果不明显;日粮中同时添加0.10%尿素及0.01%丝兰提取物,黄羽肉鸡的日增重明显提高,料肉比下降,差异显著(P<0.05)。[结论]丝兰提取物配合尿素共同使用,能明显提高黄羽肉鸡的生产性能,取得良好的社会效益和经济效益。     

4种饲料投喂对鲻(Mugil cephalus)生长及鱼体组成的影响

以初始体重(25.0±1.59) g 的鲻为研究对象，通过8周的生长实验，研究不同饲料投喂对鲻的生长及鱼体生化组成的影响。处理组分别为面粉组(T1)、米糠组(T2)、虾料组(T3)和鱼料组(T4)。研究结果显示，在室内水族缸内单一地使用面粉或米糠投喂，鲻几乎不生长，但仍能维持较高的成活率(>80%)。虾料组的特定生长率(1.46%/d)和饲料效率(48.62%)均为各组最高，约为鱼料组的两倍，且两组的特定生长率和饲料效率均显著高于面粉组和米糠组(P<0.05)。面粉组和米糠组的周均日摄食量在第4周后迅速降低(<0.80 g/d)，而整个养殖期间虾料组和鱼料组普遍高于0.80 g/d，且在第8周明显升高。养殖结束时全鱼的粗蛋白以米糠组最高(18.62%±1.36%)，粗脂肪以虾料组最高(10.52%±0.36%)。面粉组有较明显的粗脂肪积累(8.01%±0.42%)。研究结果表明，碳水化合物(面粉)水平的提高会促进鲻全鱼脂肪的积累，用米糠代替配合饲料投喂时可维持鲻的粗蛋白含量水平。