Vaccination with a genotype 1 modified live vaccine against porcine reproductive and respiratory syndrome virus significantly reduces viremia,viral shedding and transmission of the virus in a quasi-natural experimental model

The present study assessed the efficacy of vaccination against genotype 1 porcine reproductive and respiratory syndrome virus (PRRSV) in terms of reduction of the transmission. Ninety-eight 3-week-old piglets were divided in two groups: V (n = 40) and NV (n = 58) that were housed separately. V animals were vaccinated with a commercial genotype 1 PRRSV vaccine while NV were kept as controls. On day 35 post-vaccination, 14 NV pigs were separated and inoculated intranasally with 2 ml of a heterologous genotype 1 PRRSV isolate (“seeder” pigs, SP). The other V and NV animals were distributed in groups of 5 pigs each. Two days later, one SP was introduced into each pen to expose V and NV to PRRSV. Sentinel pigs were allocated in adjacent pens. Follow-up was of 21 days. All NV (30/30) became viremic after contact with SP while only 53% of V pigs were detected so (21/40, p < 0.05). Vaccination shortened viremia (12.2 ± 4 versus 3.7 ± 3.4 days in NV and V pigs, respectively, p < 0.01). The 50% survival time for becoming infected (Kaplan–Meier) for V was 21 days (CI_95% = 14.1–27.9) compared to 7 days (CI_95% = 5.2–8.7) for NV animals (p < 0.01). These differences were reflected in the R value as well: 2.78 (CI_95% = 2.13–3.43) for NV and 0.53 (CI_95% = 0.19–0.76) for V pigs (p < 0.05). All sentinel pigs (10/10) in pens adjacent to NV + SP pens got infected compared to 1/4 sentinel pigs allocated contiguous to a V + SP pen. These data show that vaccination of piglets significantly decrease parameters related to PRRSV transmission.     

影响胚胎移植成功率的主要因素

本文针对在胚胎移植过程中可能预见的各种影响胚胎移植技术的实施的因素进行了较为全面的分析,并针对不同影响因素提出了自己独特的见解,以期在生产实践中对胚胎移植技术的应用和推广有所借鉴。     

Isolation,Identification and Biological Characteristics of Staphylococcus chromogenes from Tibetan Pigs

In order to understand the infection of Staphylococcus disease in healthy Tibetan pigs in Linzhi city,Tibet.232 samples were collected from the slaughterhouse in Bahe town,Gongbujiangda county,Linzhi city,Tibet,the teaching practice ranch at the Tibet Agriculture and Animal Husbandry University in Bayi district,Linzhi city,and the slaughterhouse in Bayi district,Linzhi city.These samples were isolated,cultured and identified,and one isolated strain was systematically studied for biological characteristics.Epidemiological survey results showed that 73 of 232 samples were positive for Staphylococcus,the positive rate was 31.47%,16 positive samples were detected in the slaughterhouse of Bahe town,Gongbujiangda county,Linzhi,Tibet,with a detection rate of 23.89%(16/67),43 positive samples were detected in the pastures of the teaching practice ranch at the Tibet Agriculture and Animal Husbandry University in Bayi district,Linzhi city,with a detection rate of 34.40% (43/125),14 positive samples were detected in the slanghterhouse in Bayi district,Linzhi city,with a detection rate of 35.00% (14/40).Through PCR identification,gene sequencing and biochemical identification,5 strains of Staphylococcus chromogenes were isolated,and one of them (Sa LZ1) was studied systematically.The biological characteristics of the isolated strains showed that the Sa LZ1 strain formed round white convex colonies on the agar medium,with regular edges,smooth surfaces,and opaque white colonies.The isolates were Gram-positive cocci bacteria.PCR sequencing results showed that the isolate had the highest homology with Staphylococcus chromogenes (GenBank accession No.:MG576253.1),positive for serum inulin,manicol,glucose,saccharose,lactose,negative for arabinose,sodium hippurate,raffinose,xylose,urea,etc,consistent with the biochemical characteristics of Staphylococcus chromogenes.The logarithmic growth period of isolated bacteria was 5 to 10 h.The pathogenicity test of mice showed that the mortality rate of mice reached 100% when the concentration of Sa LZ1 strain reached 3.5×10⁹ CFU/mL.And the results of pathological section showed that Sa LZ1 strain could cause the visceral tissue of mice to develop pathological changes.The above results provided a theoretical basis for the prevention and control of Staphylococcus suis in Linzhi,Tibet.     

A Five-Day Progesterone Plus eCG-Based Fixed-Time AI Protocol Improves Fertility Over Spontaneous Estrus in High-Producing Dairy Cows Under Heat Stress

This study compared the efficiency of a five-day or standard (nine-day) progesterone-based regimen combined with equine chorionic gonadotrophin (eCG) in a fixed-time AI (FTAI) protocol for dairy cows. The data examined were derived from 3577 inseminations conducted in three dairy herds. Animals with no estrus signs detected over 21 days were randomly assigned to a PRID-9 or PRID-5 group. Cows in each group received a progesterone intravaginal device (PRID) for 9 or 5 days, respectively, PGF_2α and eCG on PRID removal, and GnRH 48 h later. Fixed-time AI was performed 12 h after the GnRH dose. Cows artificially inseminated following spontaneous estrus during the study period were considered as controls. Based on the odds ratio, the likelihoods of animals in PRID-9 in the warm (conception rate [CR] of 22.3%) and cool (32% CR) periods, and control animals in the warm period (26.6% CR) becoming pregnant were reduced (by factors of 0.6, 0.3 and 0.4, respectively) compared with the control animals in the cool period (CR of 43.7%). The risk of a twin pregnancy was higher (51.4%) for cystic PRID-9 cows (by a factor of 3.6) and lower (9.9%) for cyclic PRID-5 animals (by a factor of 0.4) compared with the PRID-9 cyclic cows. These findings indicate that the proposed protocol achieves similar results during the cool or warm season to those obtained when AI is conducted at spontaneous estrus during the cool season. In addition, PRID-5 reduced twin pregnancy compared with PRID-9.     

迪卡猪配套系繁殖性能统计分析

从某迪卡猪场１９９８年５月到２０００年年初的１２３４窝产仔记录中,分别对Ａ、Ｂ、Ｃ、Ｅ、Ｆ每个纯系和ＡＢ、ＣＤ、ＥＦ、ＡＢＣＤ杂交组合中母猪的繁殖性能进行了统计,计算了不同杂交组合的杂种优势率,从育种的角度分析了迪卡猪商品代具有很高生产性能的原因。     

瘦素调控动物生殖活动的研究进展

瘦素是白色脂肪细胞分泌的一种分子量为１６ｋＤａ的分泌型蛋白激素,具有调控动物机体能量代谢平衡和体重的生物学作用。此外,作为机体的能量代谢信号,瘦素对动物初情期的启动和正常发情周期的维持 、生殖器官和生殖腺的发育等生殖活动和生殖机能均起着非常重要的调节作用。由于它的受体存在于多种生殖器官上,瘦素可在生殖轴的不同水平对生殖活动予以调节。瘦素在正丘脑水平对于生殖活动的调节可能是其直接作用于ＧｎＲＨ神经元     

纤维素复合酶对小麦日粮酶解效果的研究

通过使用不同添加量饲用纤维素复合酶在不同时间预消化处理小麦日粮,研究饲用纤维素复合酶添加量对小麦日粮酶解效果的影响。试验结果表明：添加饲用纤维素复合酶对小麦日粮的酶解率、中性洗涤纤维和酸性洗涤纤维有影响,但并不是饲用纤维素复合酶的添加量越高作用效果越明显。在36h处理组中,饲用纤维素复合酶添加量在0．2‰水平下,酶解效果最好,与添加量为0．12％。与0．16％。相比,差异极显著（P〈0．01）;在12h、48h处理组中,饲用纤维素复合酶添加量为0．12％。与0．16％。0．2‰水平的相比,差异不显著（P〉0．05）。     

L-苹果酸对断奶仔猪生长性能的影响研究

为评价L-苹果酸对断奶仔猪生长性能的影响,本试验选取均重6 kg左右的断奶仔猪100头(公母各半),随机均分成试验组和对照组,对照组饲喂基础日粮,试验组在每千克基础日粮中加入2.0 g L-苹果酸,两组均按常规免疫程序免疫,32d后统计仔猪存活率和增重率。结果显示:在基础日粮中添加L-苹果酸,可以提高保育阶段仔猪的存活率和增重率,增加养猪效益。     

复合植物提取物对妊娠母猪繁殖性能的影响

为研究复合植物提取物对妊娠母猪繁殖性能的影响,试验选取40头妊娠85 d大长二元母猪,随机分为对照组、植物提取物组(1000 mg/kg),每头猪为一个重复,试验期为妊娠85 d至分娩。结果表明:植物提取物组仔猪初生重较对照组提高7.6%(P<0.05),并且植物提取物组高初生重仔猪的比例增加(P<0.01),低初生重仔猪的比例减少(P<0.05)。综上,复合植物提取物可提高仔猪初生重,改善仔猪均匀度,提高母猪的繁殖性能。