Dietary calcium requirement in fishes

The dietary requirement of calcium (Ca) has been well established in terrestrial animals. However, investigations for dietary Ca requirement in fish are complicated and reports limited as fish can use waterborne Ca in addition to dietary Ca. Ca absorption in fishes from environmental water is species specific and depends on concentration of Ca in rearing environment and availability of dietary Ca. Ca and phosphorus are generally combined together in fish body therefore maintaining a dietary calcium: phosphorus ratio is important. Ca exists in a complex form in fish meal, which is not available to fishes; hence, although fish meal contains an appreciable amount of calcium, dietary Ca supplementation in fish meal‐based diets for some species is necessary. This review article summarizes and discusses pertinent information on absorption of Ca from water, essentiality of dietary Ca, bioavailability of Ca from different sources, optimum calcium:phosphorus ratio and dietary Ca requirement in fishes.     

Comparison of dietary essential amino acid requirements determined from group‐housed versus individually‐housed juvenile bluegill,Lepomis macrochirus

Two 60‐day experiments were conducted sequentially to determine (i) lysine requirement of juvenile bluegill, Lepomis macrochirus based on the dose–response method, (ii) requirements for other essential amino acids (EAAs) using whole‐body amino acid profile and (iii) whether differences in growth rates of group‐housed versus individually‐housed bluegills lead to different lysine requirement levels because of the presence and absence, respectively, of social hierarchies. Seven, semi‐purified, experimental diets (isonitrogenous, isocaloric) were prepared to contain graded levels of digestible lysine (10–31 g kg⁻¹). Experiment‐1 involved group‐housed bluegills (approximately 27 g, n = 10 fish/chamber, 4 chambers/diet) whereas experiment‐2 involved individually‐housed bluegills (approximately 30 g, n = 1 fish/chamber, 14 chambers/diet). Fish were fed twice daily to apparent satiation. Bluegill growth responses in both experiments generally improved (P < 0.05, anova ) with increasing dietary lysine levels from 10 to 16 g kg⁻¹, and then levelled off with further increase in lysine level (P > 0.05). Optimal dietary lysine level (digestible basis) was estimated to be 15 g kg⁻¹ based on broken‐line regression analyses of relative growth rate and feed conversion ratio with no differences being observed between the two rearing methods. Determined dietary requirement levels for other EAAs ranged from 2.4 g kg⁻¹ (tryptophan) to 15.3 g kg⁻¹ (leucine).     

Growth, reproductive performance, muscle and egg composition in grass carp, Ctenopharyngodon idella (Valenciennes), fed hydrilla or formulated diets with varying protein levels

Growth, reproductive performance, muscle and egg composition were investigated in grass carp, Ctenopharyngodon idella (Valenciennnes), fed hydrilla or formulated diets with varying protein levels. Five experimental diets, with varying levels (20%, 25%, 30%, 35% and 40%) of crude protein (CP), were used. One of the fish groups was fed hydrilla. Fish (44.1±0.3 cm; 913±9 g) were stocked (20 tank^?1) in outdoor concrete tanks (20 × 10 × 1.5 m) in duplicate, and fed to satiation, twice daily, at 09:00 and 17:00 hours for the experimental duration of 360 days. High (P<0.05) weight gain was recorded in fish fed 30% and 35% CP diets. However, values for gonadosomatic index (GSI), egg diameter, relative fecundity (eggs kg^?1 body weight), fertilizability and hatchability (%) were comparable (P>0.05) in fish at ≥25% of dietary protein intake. Hydrilla‐fed fish exhibited lower (P<0.05) values for the measured parameters. Crude protein content in muscle increased with dietary protein level. Highest (P<0.05) muscle protein was obtained in fish fed 35% CP diet. Muscle fat was comparable (P>0.05) among fish receiving formulated diets. Ash content was not significantly (P>0.05) different among fish of different dietary groups. Moisture content in fish fed formulated diets, with the exception of 20% CP diet, did not vary significantly (P>0.05). Eggs of fish fed formulated diets contained higher CP and fat contents than those of hydrilla‐fed fish. High (P<0.05) moisture content was noted in the eggs of hydrilla‐fed fish. Ctenopharyngodon idella fed formulated diet, with a minimum of 25% CP, showed better reproductive performance than those fed hydrilla.     

不同栽培技术对马铃薯水份利用率的影响

在三种不同的栽培技术中,地膜覆盖平均WUE为1.69kg/mm较平作平均WUE1.26kg/mm提高34.13%水分利用率,垄作平均WUE为1.47kg/mm较平作提高16.67%水分利用率,脱毒马铃薯的平均WUE为1.60kg/mm,未脱毒马铃薯的平均WUE为1.34kg/mm,水分利用率提高19.35%。平作种植方式马铃薯现蕾至成熟期需水量占整个生育期到90%左右;垄作种植方式76.86~83.3%;地膜覆盖种植方式73.08~77.08%,垄作与地膜覆盖后马铃薯水分的利用趋于合理。进行地膜覆盖和垄作后能使植株健壮,单窝薯重,大中薯商品薯率高,从而提高马铃薯的产量。     

An Evaluation of the Suitability of Selected Waste Products in Feeds for Three Fish Species

ABSTRACT

Five types of aquatic food industry waste products (carp offal, carp roe, fish frames, trout offal and surimi processing waste) together with fish meal were evaluated for their suitability as potential fish meal replacements, partially or wholly, in diets for three species (rainbow trout, Murray cod and shortfin eel) cultured in Australia, using a number of criteria.

The proximate composition of the ingredients on a dry matter basis including protein content, lipid and ash, varied considerably. The essential amino acid (EAA) contents of the waste products and fish meal decreased in the order: carp roe > fish meal > carp offal > ‘surimi’ processing waste > fish frames > trout offal. The results of cluster analysis of A/E ratios of waste products and fish whole body fell within three clusters. The EAAI of whole body tissue of Murray cod, rainbow trout and Australian shortfin eel however, were closest to fish meal, followed by fish frame waste and/or ‘surimi’ waste. The results on A/E ratios and EAAI did not conform to the raw data on TAA and EAA. Therefore, the study emphasizes the need to have a multi-prong approach to determine the suitability of ingredients for incorporation into fish feeds.     

Sex ratio changes in the long-term Windermere pike and perch sampling program

Abstract– Analysis of the Windermere (England), Perca fluviatilis (1965–1997) and Esox lucius (1943-1997) fishery data indicates there have been substantial changes in sex ratios through time. In the case of perch, a 1976 perch disease outbreak substantially skewed the sex ratio in favor of females. It took over a decade for the fishery to recover to its pre-1976 state. In the case of pike, both catch and year-class data are female biased, but this bias has significantly weakened through time. This trend towards proportionately more males through time may reflect an effect of increasing spring temperatures or an evolutionary or phenotypic response to female-biased fishing pressure.     

Fishmeal availability in the scenarios of climate change: Inevitability of fishmeal replacement in aquafeeds and approaches for the utilization of plant protein sources

Fishmeal is being trusted as the most reliable protein source due to its nutritional quality in terms of attractability, palatability, digestibility, excellent nutrient profiles to fulfil the dietary requirement of aquatic species. The aquaculture sector consumes >70% of global fishmeal, though aqua feeds constitute only 4% in total industrial feed production (900–1,000 Mt in 2018). The global fishmeal production has shown a downward trend of 26.50% during 2000 to 2018 due to the occurrences of El Niño–Southern Oscillationsand other climatic events, which in turn increased the fishmeal price from 452 USD/t (2000) to 1596.54 USD/t (2018). The increasing trend of aquaculture production along with reduced fish‐in/fish‐out ratios (0.63 in 2000 to 0.33, 0.22 in 2010 and 2015 respectively) indicates the resilience of the aquafeed sector for fishmeal replacement. The wide availability, reasonable price and reliable nutrient content made an interest in plant protein sources, but their utilization was limited due to poor digestibility, imbalanced profiles of essential nutrients and the presence of anti‐nutrients. Numerous methodologies are invented in recent times to enrich the nutritional qualities for maximizing the utilization of plant proteins in aquafeed formulations. The present review concludes that the aquafeed sector should use climate economics and technological innovations for substituting fishmeal to formulate the cost‐effective feeds.     

反刍动物脲酶抑制剂的研究进展

尿素作为非蛋白氮饲料直接饲喂动物 ,在瘤胃中分解速度快于微生物利用速度 ,这不仅降低尿素利用效率 ,而且容易造成氨中毒。脲酶抑制剂可以降低尿素的分解速度 ,提高尿素利用效率。文章就目前国内外各种瘤胃脲酶抑制剂对动物瘤胃尿素分解速度、氨浓度、营养物质利用及对动物生产性能的影响进行了综述。     

Effects of the dietary protein levels and the protein to energy ratio in sub‐yearling Persian sturgeon,Acipenser persicus (Borodin)

A 3 × 4 factorial design was used to evaluate the dietary protein requirement and to determine the optimum dietary protein to energy (P/DE) ratio in sub‐yearling Persian sturgeon, Acipenser persicus, reared in the indoor system. Twelve experimental diets (₄₀P₁₆, ₄₀P₁₇, ₄₀P₁₈, ₄₀P₁₉, ₄₅P₁₉, ₄₅P₁₇, ₄₅P₁₈, ₄₅P₁₉, ₅₀P₁₆, ₅₀P₁₇, ₅₀P₁₈ and ₅₀P₁₉) were formulated and prepared to contain three protein levels (40%, 45% and 50%) and four digestible energy levels (16, 17, 18 and 19 kJ g^?1 diet) at each protein level. Fish averaging 103.3 ± 3.5 (mean ± SD) were fed one of the experimental diets for 14 weeks. At the end of the experimental period, there were significant energy effects (P < 0.05) on weight gain (WG) and specific growth rate (SGR). Weight gain and SGR tended to decrease, although non‐significantly, with increase in dietary protein levels. Furthermore, there were significant protein and energy interaction effects on WG, SGR, hepatosomatic index and protein efficiency ratio. However, there were no significant dietary protein, energy or their interaction effects on feed efficiency for fish fed all diets. Weight gain and SGR of fish fed ₄₀P₁₉ were significantly higher than those of fish fed ₄₀P₁₆, ₄₅P₁₆, ₄₅P₁₇, ₅₀P₁₆ and ₅₀P₁₇ diets (P < 0.05). There were no significant differences in WG and SGR among fish fed ₄₀P₁₇, ₄₀P₁₈, ₄₀P₁₉, ₄₅P₁₈, ₄₅P₁₉, ₅₀P₁₈ and ₅₀P₁₉ diets. These results may indicate that the optimum dietary protein requirement and the P/DE ratio could be 40% protein and 22.0 mg protein kJ^?1 (₄₀P₁₈), respectively, in Persian sturgeon, based on growth performance and feed utilization.     

利用SSR﹑EST-SSR、SNP标记对鲤食物转化率、体厚、体质量3种性状的分析

利用Windows Map Manager2.0的标记回归法对鲤(Cyprinus carpio L.)F2群体进行单标记定位分析.用91个SSR标记、33个EST标记、364个SNP标记对鲤进行全基因组扫描,结果得到与食物转化率、体厚、体质量3个性状显著相关(P＜0.05)的标记,分别为27、35、27个,其中与食物转化率相关的标记SNP0041、SNP0044,其相关性达到极显著水平(P＜0.001),贡献率分别达到15%、16%.这些标记可作为分子标记辅助育种的参考标记.将得到的与食物转化率显著相关的EST座位HLJEl4、HLJE253和与体质量显著相关的HLJE253座位在NCBI上进行BLAST比对,结果显示HLJE253与斑马鱼上编码ORF2结构蛋白的基因相关,相关程度达61%.将得到的与3种性状相关的SNP标记在NCBI上进行序列查找,通过Blast比对找到相关的基因,并对可能的功能作了注释.