不同饲养标准对杜寒杂交肉用绵羊生产和屠宰性能的影响

本试验通过比较不同饲养标准杜寒杂交肉用绵羊增重、器官发育、屠宰性能及肉品质的差异,确定适宜的饲养标准。采用单因素试验设计,选取体重为(28.30±0.86)kg的杜寒杂交F1代肉羊600只,随机分为4组,每组3个重复,每个重复50只。4组分别饲喂按照以下饲养标准配制的饲粮:本实验室(中国农业科学院饲料研究所农业部饲料生物技术重点实验室)提出的杜寒杂交肉用绵羊饲养标准、美国NRC(2007)、英国AFRC(1993)以及我国农业行业标准的《肉羊饲养标准》(NY/T 816—2004),分别记为CARS、NRC、AFRC和HB。试验期81 d,每3 d记录1次采食量,每20 d进行1次称重,当CARS组羊只的平均体重达到44 kg时,每组选取10只羊进行屠宰,测定其屠宰性能、组织器官重量和肉品质等指标。结果表明:不同组羊只的实际干物质采食量,NRC组AFRC组CARS组HB组,其中NRC组与CARS和HB组间差异显著(P0.05),其他组间差异均不显著(P0.05);平均日增重和胴体重,CARS、HB、AFRC组间差异均不显著(P0.05),且均显著高于NRC组(P0.05);饲料转化率各组间存在显著差异(P0.05),CARS组HB组AFRC组NRC组;屠宰率,CARS组显著高于NRC组(P0.05),与HB、AFRC组间差异均不显著(P0.05);CARS组羊只的心脏、肝脏、肾脏重量占宰前活重比例显著高于其他组(P0.05);背最长肌失水率、肌肉色亮度、红度和黄度值,各组间均无显著性差异(P0.05)。结果提示,杜寒杂交肉羊在不同饲养标准下的实际日增重200~220g,从增重和屠宰性能上来看,CARS制订的饲养标准与国外饲养标准相比具有明显优势。     

Illinois Soil Nitrogen Test Method Optimization for Analysis of Temperate Mineral Grassland Soils

ABSTRACT

A reliable and practical test that can provide timely measurements of the levels of mineralizable nitrogen (MN) in soil is critical for improving the accuracy of N fertilizer applications for grassland and crops. The Illinois soil N test (ISNT) is considered to be a good estimate of MN, once soils are grouped according to soil characteristics such as the drainage type and sampling depth. To date, development and evaluation of the ISNT method has been conducted using arable soils mainly in North America where, in general, soils have lower levels of soil organic matter (SOM) compared to temperate grassland soils. We evaluated the effects of two pre-treatment soil aggregate sizes of <1 mm and <2 mm on the yield and recovery of MN (1) across temperate grassland soil types, and (2) across a 6-h interval diffusion period. No significant difference existed in the concentrations of ISNT-N between the two soil aggregate sizes of each soil type. For both aggregate sample sizes, the recovery of spiked amino sugar-N glucosamine from a temperate grassland soil was generally linear until hour 5, after which the quantities of recovered N diminished. Although N recovery after 6 h of diffusion at 50°C (±1°C) was less than 100% in both aggregate size samples, the response models indicated that the standard ISNT protocol using a 5-h diffusion period is appropriate for temperate grassland soils. The incomplete recovery of N in these mineral soils suggested that the protocol could be further optimized for temperate soils with high organic matter content and additional evaluation of the temperature during diffusion within an enclosed environment may be required using N (spiked glucosamine-N) recovery studies.     

Structural development of Pacific red snapper Lutjanus peru from hatching to the onset of first feeding

Successful rearing of larval fish requires culture conditions and feeding strategies matching the ontogenetic status of larvae. This study describes the external morphology and development of organs and structures involved in the feeding process (i.e. sensorial organs, mouthparts and digestive system) from hatching until first feeding in Pacific red snapper. Hatching occurred 26 h after fertilization at 26°C and total length (TL) was 2.45 ± 0.08 mm. The larvae showed an undifferentiated eye and digestive tract. At 48 hah, TL was 3.31 ± 0.12 mm. Yolk and oil globule were still present. The mouth was still closed, but the Meckel's, quadrate, hyoid and hyomandibular cartilages were present. The retina was formed by 5 layers, and a thin layer of pigment epithelium was observed in the outer nuclear layer (ONL). At 70 hah, TL was 3.44 ± 0.22 mm. A remnant of oil globule was still present. The mouth and anus were open. At 93 hah, the number of cones in the ONL of the retina have increased and there was more pigment in the pigment epithelial layer. A joint between Meckel's and the quadrate cartilage and also a joint between the hyomandibular cartilage and the skull were present. The presence of live feed was detected in the digestive tract of these larvae. Based on these observations, the Pacific red snapper larvae is functional to start ingesting live feed between the 3rd and 4th day after hatching.     

水貂细小病毒性肠炎灭活疫苗保存期试验

对2~8℃条件下保存90,120,150,180,210,240,300,360 d的水貂细小病毒性肠炎灭活疫苗接种水貂进行免疫试验,结果表明:保存300 d的疫苗接种水貂30 d后血清中水貂肠炎细小病毒(MEV)HI抗体均在1∶32以上,免疫水貂强毒攻击均获得100%保护,确定水貂细小病毒细胞灭活疫苗保存期为300 d。该结果为水貂细小病毒细胞灭活疫苗运输和保存提供了理论依据。     

水稻籽粒灌浆特性及品质对孕穗期

以3个不同直链淀粉含量的水稻品种为材料,研究了孕穗期弱光对水稻籽粒灌浆及稻米品质的影响,并用Richards方程拟合籽粒的灌浆过程。结果表明,孕穗期弱光处理后,籽粒终极生长量(A)有所降低,起始灌浆势(R0)、最大灌浆速率(Gmax)、平均灌浆速率(G)的变化则因品种而异;糙米率、精米率显著下降,整精米率、垩白率、直链淀粉及蛋白质含量的变化因品种而异;精米率、糙米率与籽粒A值呈显著或极显著正相关,直链淀粉含量、整精米率与籽粒的R0、Gmax、G呈显著或极显著负相关,垩白率与籽粒的G、R0、Gmax呈显著或极显著正相关。在弱光区,可以采用育种、栽培技术、化学控制等手段来改变与稻米品质密切相关的籽粒灌浆参数值,以减轻弱光胁迫对稻米品质的危害程度。     

樱桃低温冷害气象灾害预警体系研究

针对樱桃危害较大的低温冻害,结合樱桃2001-2018年产量资料和1974-2019年3月1日至4月30日近46 a的气象数据,采用多元回归法,筛选耦合的气象条件,找出制约樱桃产量的气象因子,建立樱桃花芽萌动期和盛花期冻害等级预报模型。并针对灾害提出气象灾害防御对策,为今后充分利用地方气候条件,大力发展樱桃产业提供科学依据。     

中国区域畜禽粪便能源潜力及总量控制研究

为了评估中国畜禽粪便资源总量及其对环境的影响,以环保部、统计局和农业部发布的区域畜禽产排污系数为基础,利用2010年的统计数据,研究了中国及各省的畜禽粪便资源总量、能源潜力及农地的氮磷负荷,并以欧盟的农地氮磷施用标准对中国畜禽养殖的环境容量和污染风险进行了初步评估。结果表明,2010年,中国畜禽粪便总量达22.35亿t,可产沼气1072.75亿m3,山东等6省市粪便资源超过1.00亿t;全国单位面积农地氮磷平均负荷为43.73kg/hm2(TN)和9.16kg/hm2(TP),北京等6省市农地氮磷负荷超标;全国畜禽养殖环境容量为129.56亿头猪当量(以N为基准),159.74亿头猪当量(以P为基准),实际养殖总量约占环境容量的1/4,考虑化肥施用的影响,约有20个省超过本省50%环境容量。研究结果为区域畜禽养殖总量控制、合理布局和粪污的综合利用提供决策依据。     

水稻两用核不育系育性转换与温度的相关分析

在贵阳对8个籼型水稻两用核不育系进行了间期为10－15d的分期播种，以套袋自交结实性作为育性考查指标，结果所有核不育系都有稳定不育期和可育或部分可育期表现，且育性转换明显。稳定不育期的长短因不育系不同而有差异，范围在5－33d。自交结实率与日平均气温之间的相关性表明，所有不育系都在幼穗发育的一定阶段内对温度表现敏感，大多数不育系的温度敏感时期在抽前7－24d，培矮64S在抽穗前17－30d。不同不育基因供体来源的不育系对温度敏感时期和持续时间长短存在着差异，同一不育基因供体来源的不同不育系之间，其育性对温度敏感时期和持续时间长短也不相同。     

It is the ambience,not the menu. Prey availability does not drive habitat selection by the endangered Pyrenean desman

1. The Pyrenean desman (Galemys pyrenaicus) is an endangered stream-dwelling insectivore endemic to the Iberian Peninsula and the north of the Pyrenees. It favours riffles over slow habitats such as runs or pools, yet it is still unclear whether habitat preference is based on prey availability or on other factors, such as mechanical constraints on its hunting habits.
2. Desman diet and prey selection were analysed along the pristine Elama Stream and the slightly modified Leitzaran Stream in the Basque Country, Spain.
3. In each stream the prey consumed were identified by metabarcoding 94 desman faeces, and prey availability characterized from 10 Surber samples taken in each habitat type (riffles, runs and pools). Invertebrates were sorted and identified, the biomass of each taxon was calculated, and their DNA was also extracted, amplified using PCR, and sequenced to build a reference database.
4. Prey availability and diet varied between streams. Desmans positively selected shredders and invertebrates that live on the substrate, and selected against taxa that live in fine sediment, taxa with hard shells or those that are highly mobile. The diet of desmans was more selective in the Elama, the stream with better ecological status. Food availability did not differ among habitats, and therefore does not explain the preference of desmans for riffles; rather, mechanical constraints to deal with buoyancy and physical habitat heterogeneity were hypothesized to be the reason behind the habitat preference.
5. The results suggest that promoting the formation of riffles in streams can improve the situation of some desman populations living in degraded habitats.

     

A test of the individual feeding activity and food size preference in rainbow trout using demand feeders

Feeding activity and food size preferences were investigated in three groups of rainbow trout with initial weights ranging from 200 to 1000 g. Fish were given the option of releasing food from either of two demand feeding devices that contained either 6 mm or 9 mm food pellets. Individual biting activity (to activate release of food) was continuously monitored using specially designed passive integrated transponders (PIT-tags). In each of the groups, biting activity was strongly influenced by three individuals, which accounted for 70–85% of the total. Thus, high bite activity by few individuals indicates the development of social dominance hierarchies. There was no statistically significant correlation between number of bites and growth rate, indicating that the fish that operated the demand feeders did not gain any growth advantage. Trout that dominated the actuation of the feeders were found among both medium- and large-sized fish. There was no evidence of active food size selection, and the fish that most frequently operated the feeders defended one area of the tank rather than preferring the trigger that would have delivered food of the optimal size.