Advection of anchovy (Engraulis encrasicolus) larvae along the Catalan continental slope (NW Mediterranean)

The Gulf of Lions is one of the main anchovy (Engraulis encrasicolus) spawning areas in the NW Mediterranean. During the spring, low‐salinity surface water from the outflow of the Rhône is advected by the shelf‐slope current along the continental slope off the Catalan coast. In June 2000, a Lagrangian experiment tracking these low‐salinity surface waters was conducted to assess the importance of this transport mechanism for anchovy larvae and to determine the suitability of the tracked surface waters for survival of anchovy larvae. The experiment consisted of sampling the tracked water parcel for 10 days with three drifters launched at the core of the shelf‐slope current where low‐salinity surface waters were detected. The survey was completed by sampling the surrounding waters. Anchovy larvae from the spawning area in the Gulf of Lions were advected towards the south in the low‐salinity waters. The size increase of anchovy larvae throughout the Lagrangian tracking closely followed the general growth rate calculated by otolith analysis (0.65 mm day⁻¹). However, advection by the current was not the only mechanism of anchovy larval transport. A series of anticyclonic eddies, originated in the Gulf of Lions and advected southwards, seemed to play a complementary role in the transport of larvae from the spawning ground towards the nursery areas. These eddies not only contributed to larval transport but also prevented their dispersion. These transport and aggregation mechanisms may be important for anchovy populations along the Catalan coast and require further study.     

Digestive enzyme responses of tambaqui (Colossoma macropomum) fed on different levels of protein and lipid

The adaptation of digestive proteases, amylase and lipase was studied in tambaqui fed with 350, 253, 301 and 205 g kg^?1 of crude protein, and 49, 81, 113 and 145 g kg^?1 of lipid, in isocaloric diets. Digestive protease increased when dietary protein increased in stomach, where the highest specific activity was observed. Unspecific protease activity in intestine was very low. Lipase was observed throughout the gastrointestinal tract, and higher activities were observed in the stomach. However, pyloric caecum and the anterior and posterior intestines were the responsive sections to the dietary lipid. Amylase was detected throughout the gastrointestinal tract, but pyloric caecum was the most relevant amylase producer. Positive correlations were observed between anterior intestine lipase versus dietary lipid and pyloric caecum amylase versus dietary protein. Tambaqui is responsive to the food composition adapting the main digestive enzymes to the best profile.     

Regrouping of pigs by body weight at weaning does not affect growth performance,carcass quality or uniformity at slaughter of heavy weight pigs

We studied the influence of pen uniformity at weaning (7.5 ± 0.6 kg vs. 7.5 ± 1.2 kg body weight (BW ± SD)) and sex on growth performance during the nursery (7.5 to 27.3 kg BW) and the fattening (27.1 to 130.5 kg BW) phases and carcass quality of barrows and castrated females (CF). During the nursery phase, pigs from the more uniform pens had lower feed efficiency (P = 0.05) than pigs from the less uniform pens. Also, barrows had higher average daily feed intake (ADFI) (P < 0.05) and average daily gain (P < 0.001) and better feed efficiency (P < 0.001) than CF. During the fattening phase, initial pen uniformity did not affect growth performance of the pigs but barrows tended (P = 0.08) to have higher ADFI and worse feed efficiency than CF. Trimmed primal cut yield tended to be higher for the more uniform pigs and better for barrows than for CF (P = 0.09). It is concluded that regrouping of the pigs at weaning according to uniformity of BW did not affect growth performance or carcass quality of the pigs at slaughter. Castrated females might be used as an alternative to barrows for the production of carcasses destined to the dry‐cured industry.     

基于离散元的不同轴截面形状下沙柳颗粒致密成型研究

为研究模具的结构形状对沙柳颗粒致密成型的影响,用离散元软件EDEM建立了沙柳颗粒模型,并将预先用Pro/E创建的3种不同结构的模具先后导入其中,在初始参数、条件设定完成后分别做了匀速压缩模拟。对比研究了3种模具下压缩力的做功,颗粒在竖直和水平方向的形变特征、受力过程,并通过后处理所得数据分析计算了各模具下成型燃料最终获得的密度和能量。结果表明:双弧度、双锥度、单锥度3种模具下压缩过程做功依次为48.86、56.93、66.02 J,燃料总能量分别是40.06、41.54、46.81 J,对应密度为1.23、1.19、1.17 g/cm3;竖直方向双弧度下燃料内部颗粒受到的接触力和发生的形变远大于其他两种模具,水平方向三者颗粒所受的接触力和发生的形变无太大差异;颗粒在3种模具下受到的粘接力均无明显不同,但各自所受的法向粘接力远大于切向粘接力。     

西藏高寒区禾-豆混播对牧草营养品质及土壤养分的影响

采用随机区组试验设计,以燕麦(Avena sativa)、箭筈豌豆(Vicia sativa)、饲用豌豆(Pisum arvense)为材料,于2019年在拉萨墨竹工卡具开展单播、禾-豆混播种植方式下牧草产量和品质的比较.通过分析种植后土壤养分的变化,在确保牧草生产性能的同时,探讨禾-豆混播的土壤改良作用.结果表明:(...