饲料蛋白质和小麦淀粉水平对中大规格草鱼生长性能及肝脏组织结构的影响

草鱼(Ctenopharyngodon idella)对碳水化合物的利用能力显著优于脂肪, 因此研究碳水化合物与蛋白的相互作用关系是解决草鱼配方策略的重要途径。实验探讨了中规格(460 g)草鱼和大规格(1970 g)草鱼饲料中蛋白与碳水化合物的相互作用关系。实验采用2×4的双因子实验设计, 实验一: 中规格草鱼饲料的2个淀粉梯度为25%和35%, 4个蛋白梯度为22%、24%、26%和28%, 共8个处理; 实验二: 大规格草鱼饲料的2个淀粉梯度为30%和40%, 4个蛋白梯度为18%、20%、22%和24%, 共8个处理。在56d的等量投喂后, 实验结果显示: 中规格草鱼的生长性能随着饲料蛋白水平的升高显著上升, 在28%蛋白水平组达到最高(P<0.05), 且小麦淀粉水平35%组的生长性能显著高于25%组(P<0.05); 大规格草鱼的生长性能也随着饲料蛋白水平的升高显著上升, 在蛋白水平大于20%之后差异不显著(P>0.05), 且小麦淀粉水平40%组的生长性能显著高于30%组(P<0.05)。同时, 中规格和大规格草鱼饲料分别添加35%和40%小麦淀粉时不会对草鱼的肝脏组织造成明显的负面影响。由此可见, 在实验条件下, 中规格和大规格草鱼分别在饲料小麦淀粉水平35%和40%以内时, 可以有效地利用淀粉节约饲料蛋白而不造成肝脏组织损伤。     

许氏平鲉幼鱼的赖氨酸需求量

通过8周的生长实验确定了许氏平(Sebastes schlegeli)幼鱼的赖氨酸需求量。饲料必需氨基酸组成(除赖氨酸外)参照鱼体肌肉蛋白的氨基酸模式,配制赖氨酸含量为1.542、.04、2.54、3.04、3.54和4.04%的等氮等能的六种半精制饲料。研究结果表明,随着饲料中赖氨酸含量的增加,增重率逐渐提高,当饲料中赖氨酸含量为3.54%时,达到最大值(P0.05)。基础饲料组的蛋白质贮积率最低,且显著低于3.54%组(P0.05),和其他组之间差异不显著(P0.05)。随着饲料中赖氨酸含量的增加,饲料系数逐渐降低,当饲料中赖氨酸含量为3.54%时达最小值,随着饲料中赖氨酸含量继续增加饲料系数呈上升趋势(P0.05)。饲料中赖氨酸水平对鱼体的干物质、蛋白质、脂肪、灰分和能量含量均无显著影响(P0.05)。饲料中赖氨酸水平对血清谷丙转氨酶(ALT)、谷草转氨酶(AST)活性有显著性影响(P0.05),而对血清甘油三酯及胆固醇含量没有显著性影响(P0.05)。通过回归分析,得出许氏平幼鱼最大生长的饲料赖氨酸需求量2.99%,占饲料蛋白的6.16%。       

Growth and hepatic acetyl coenzyme-A carboxylase activity are affected by dietary protein level in European seabass (Dicentrarchus labrax)

Two trials were undertaken with European seabass (Dicentrarchus labrax) to estimate the protein requirements for maintenance and growth as well as the effect of dietary protein level on the activity of hepatic acetyl coenzyme-A carboxylase (ACoAC). Six diets were formulated to contain graded levels of protein (from 5 to 55% crude protein (CP)) at a constant (12%) lipid level. Three other diets were also formulated to contain 35, 45 and 55% CP, but with a higher lipid level (19%). Groups of 10 individually marked fish (IBW: 100 g) and groups of 8 fish (IBW: 160 g) were used in trial I and II, respectively. Fish were fed to visual satiety and intake was recorded. At the end of both studies, whole body, liver and plasma samples were withdrawn for analyses. Growth rate was improved with increasing dietary CP level. Despite not being the object of a statistical analysis, feed efficiency tended to be enhanced at higher dietary CP level and protein efficiency ratio tended to decrease with increased protein intake. The reduction of the dietary protein/energy ratio, due to the increase of dietary lipids further improved growth and feed utilisation. Data from both experiments indicate 4.5+/-0.5 g kg(-1) d(-1) as the daily protein intake for maximum N gain and 520+/-50 mg kg(-1) d(-1) as the maintenance needs for nitrogen balance. An increase of dietary CP level, up to 25%, increased ACoAC activity. A further increase in dietary CP level (35 to 55%) did not affect liver ACoAC activity. The increase in dietary lipid level depressed significantly liver ACoAC specific activity.     

南方鲇的营养学研究：Ⅲ．饲料脂肪对蛋白质的节约效应

于１９９７年１０月至１２月对南方鲇（Silurus meridionalis)(初始体重：３０－４４g)进行人工配合饲料的喂养实验。实验以白鱼粉和 玉米油作蛋白质和脂肪源,共配制６种不同蛋白质／脂肪比的饲料,其蛋白质（Ｐ）和脂肪（Ｌ）的含是分别为４３％Ｐ／１５％Ｌ,４７％Ｐ／１５％Ｌ,５１％Ｐ／１６％Ｌ,５０％Ｐ／８％Ｌ,５４％Ｐ／８％Ｌ,５８％Ｐ／８％Ｌ。实验每饲料水平设４个重复,采用室内循环水养殖系统,在２７．５℃下以饱足日粮水平喂养６周。实验结果表明：供以高脂肪低蛋白质饲料组鱼体的特殊生长率（ＳＧＲ）和饲料转化率（ＦＣＥ）与低脂肪高蛋白饲料的无显著差异,而前者喂养的实验鱼的蛋白质效率（ＰＥＲ）显著大于后者,因此,南方鲇饲料脂肪对蛋白质有明显的节约效应。     

饲料蛋白和脂肪水平对青鱼大规格鱼种生长和体组成的影响

设计5个饲料蛋白水平（30%、33%、36%、39%和42%）和2个脂肪水平（6%和9%）的52的因子试验,配制10种试验饲料,分别饲喂10组三重复平均体重为95.5 g的二龄青鱼70d,以探讨不同蛋白和脂肪水平对青鱼生长和体组成等的影响。结果表明: 鱼体增重随饲料蛋白水平从30%提高到39%不断增加（P0.05）,进一步提高饲料蛋白水平至42%时,鱼体增重则不再显著变化（P0.05）;饲料系数随饲料蛋白水平从30%提高到39%而不断降低（P0.05）,进一步提高饲料蛋白水平至42%时,也不再显著变化;蛋白质效率和蛋白保留率随饲料蛋白水平呈下降趋势;以鱼体增重为指标,经折线模型进行回归分析求得适宜的饲料蛋白水平为占干饲料的40%。饲料蛋白、脂肪水平及其交互作用对的试验鱼成活率均无显著差异（P0.05）。饲料脂肪水平、饲料蛋白与脂肪的交互作用对鱼体增重、饲料系数、摄食率和蛋白质效率也均无显著影响（P0.05）。摄食蛋白水平为30%和33%饲料的青鱼与摄食蛋白水平36%-42%饲料的青鱼相比,有较低的水分和较高全鱼脂肪（P0.05）。青鱼脏体比和肌肉粗脂肪含量均随着饲料中蛋白水平的提高呈降低的趋势。摄食脂肪水平为9%的饲料的青鱼较摄食脂肪水平为6%的饲料的青鱼,有较高脏体比、全鱼脂肪含量和肌肉粗脂肪含量（P0.05）。上述结果说明,青鱼摄食低蛋白和高脂肪的饲料造成过多的体脂积累。在试验条件下,青鱼大规格鱼种饲养阶段适宜的饲料蛋白和脂肪水平分别为占干饲料的40%和6%。       

Effect of increasing inclusion rates of tofu by-product in diets of growing pigs on nitrogen balance and ammonia emission from manure

To reduce competition with human-edible feed resources, it is of interest to incorporate by-products from the food industry in animal feeds. The current research investigated the effect of including increasing amounts of tofu by-product (TF) in practical pig diets on animal performance, nitrogen balance and ammonia emissions from manure. Two experiments were conducted including a control diet without TF, containing 160 g/kg dietary non-starch polysaccharides (NSPs) and three diets including 122, 246 and 360 g TF/kg DM (TF122, TF246 and TF360, respectively) to reach 220, 280 and 360 g/kg NSP. All diets had the same level of CP and protein digestible in the small intestine which particularly was realized by replacing rice bran with TF. Animal performance was assessed in a first experiment with 40 growing barrows with initial BW of 26.6 ± 1.80 kg (M ± SD) being allocated to the 4 treatments, during 2 growth phases (i.e. until 50 kg BW and from 50 to 80 kg BW). In the growth phase until 50 kg, feed intake and average daily gain (ADG) were linearly reduced by dietary TF inclusion, while this negative impact disappeared during the second growth phase (50 to 80 kg BW). Tofu by-product inclusion even positively affected the feed conversion ratio during this second growth phase (3.4 to 2.7 kg feed/kg ADG for 0 to 360 g/kg dietary TF). Over the entire growth period, performance and feed intake were negatively affected at the highest dietary TF level. Experiment 2 was conducted to assess digestibility, nitrogen balance and ammonia emission from manure. For this purpose, 16 pigs with BW of 62.8 ± 3.6 kg (M ± SD) were assigned to either 1 of the 4 treatments. There was no difference in total tract apparent digestibility of dietary organic matter or CP, while NDF digestibility increased with increasing TF level, suggesting increasing importance of the hindgut fermentation when digesting diets with increasing TF levels. Nevertheless, this was not reflected in increasing levels of faecal volatile fatty acids or purines, nor in reduced manure pH. As a result, ammonia emission from slurry was not reduced through dietary TF inclusion, despite the linear decrease in urinary nitrogen. In conclusion, TF can be included in pigs’ diets up to an inclusion rate of 25% without risk of impaired animal performance; however, this dietary strategy fails to mitigate ammonia emission from slurry.     

单宁酸对根田鼠断乳幼体生长和存活的影响

在食物中含10％和20％蛋白质条件下,测定了单宁酸对根田鼠幼体在断乳后20d内的生长和存活的影响。结果表明,食物中含蛋白质为10％的条件下,摄食含3％和6％单宁酸食物的试验个体生长速率分别为-0．135g/d和-0．25g/d,食物利用效率均显低于对照组,断乳后20d内平均存活天数较对照组分别下降26．23％和49．36％。在食物蛋白质为20％的条件下,摄食含3％和6％单宁酸食物的试验个体生长速率分别为0．134g/d和-0．116g／d,摄食6％单宁酸食物的试验个体食物利用效率显低于摄食3％单宁酸食物的试验个体和对照组个体,断乳后20d内的平均存活天数较对照组下降39．41％,摄食3％单宁酸食物的试验个体较对照组略有下降,但不显。上述结果验证了单宁酸能显影响植食性小哺乳动物生长和存活的假设。     

黄鳝饲料蛋白质需求量的研究

为确定黄鳝(Monopterus albus)对饲料蛋白质的需求量, 试验分7组, 每组4个重复。每个重复放养初始体重为(17.1±0.2) g的幼鳝25尾, 分别以鱼粉和酪蛋白为主要蛋白源, 配制蛋白质含量为32.74%(T1)、38.50%(T2)、42.26%(T3)、48.35%(T4)、52.65%(T5)、57.87%(T6)和62.31%(T7)的7种等能不等氮饲料, 养殖期为60d。以生产性能、蛋白质保留率和生理生化指标等综合评价确定蛋白质的需求量。结果: (1)随饲料蛋白质含量升高, 饲料系数呈先降低后升高; 增重率(WGR)、特定生长率(SGR)、蛋白保留率(PRR)与蛋白质效率(PER)先升高后降低; 饲料蛋白质含量57.87%组获得最好的生长性能, 52.65%组蛋白质保留率最高。(2)随饲料蛋白质含量升高, 黄鳝血清中尿素氮(BUN)含量升高, 谷丙转氨酶(ALT)和谷草转氨酶(AST)的活性先降低后保持稳定, 总胆固醇(TC)、甘油三酯(TG)、高密度脂蛋白(HDL-C)、低密度脂蛋白(LDL-C)及血糖(GLU)含量降低; 丙二醛(MDA)含量呈现先降低后升高的趋势, 在52.65%时最低。(3)随饲料蛋白质含量升高, 黄鳝肝胰脏、胃和肠蛋白酶活性先显著上升后呈缓慢上升趋势; 肝胰脏脂肪酶活性先显著下降后呈缓慢下降趋势, 胃和肠脂肪酶活性各试验组之间无显著性差异; 胃淀粉酶活性无显著差异, 肝胰脏和肠呈先显著下降后缓慢降低的趋势。综上: 当饲料蛋白质含量低时, 黄鳝会加大摄食量满足蛋白质需求, 在饲料蛋白质含量过高时, 氧化应激增加, 黄鳝通过降低摄食量减少蛋白质摄入。以WGR、PER、SGR及饲料系数(FCR)为评价指标确定幼鳝对饲料蛋白质的适宜需求量为48.51%—52.60%。     

Does dietary P affect feeding and performance in the mixed-feeding grasshopper (Acrididae) Melanoplus bivitattus?

Although consequences of limited dietary protein and carbohydrate to performance are well studied for terrestrial insect herbivores, the importance of phosphorus (P) remains poorly understood. We examined the significance of dietary P to performance in fifth-instar nymphs of the grasshopper Melanoplus bivittatus fed artificial diets. Consumption, digestion, developmental rate, and growth in response to different levels of P nested within standard-Protein and carbohydrate diets were determined. Developmental rate was slowest on high-P diets; protein:carbohydrate concentration and P in diets affected frass production and consumption. Approximate digestibility and conversion of digested food were primarily influenced by the protein:carbohydrate quality of the diet but not P. Mass gain was marginally lower in the low-Protein:high carbohydrate diet used in this study. At the individual level, other than small effects to developmental rate at high concentrations for M. bivittatus, dietary P otherwise seems to have little effect on nymphal performance. To the degree that it is important, effects of dietary P depend on the concentrations of protein and carbohydrate in the diet.     

Interactions of dietary protein and carbohydrate determine blood sugar level and regulate nutrient selection in the insect Manduca sexta L

The non-homeostatic regulation of blood sugar concentration in the insect Manduca sexta L. was affected by nutritional status. Larvae maintained on diets lacking sucrose displayed low concentrations of trehalose, the blood sugar of insects, which varied from 5 to 15 mM with increasing dietary casein level between 12.5 and 75 g/l. These insects were glucogenic, as demonstrated by the selective 13C enrichment of trehalose synthesized from [3-13C]alanine, and de novo synthesis was the sole source of blood sugar. The distribution of 13C in glutamine established that following transamination of the 13C substituted substrate, [3-13C]pyruvate carboxylation rather than decarboxylation was the principal pathway of Pyr metabolism. The mean blood trehalose level was higher in insects maintained on diets with sucrose. At the lowest dietary casein level blood trehalose was approximately 50 mM, and declined to 20 mM at the highest casein level. Gluconeogenesis was detected in insects maintained on sucrose-free diets at the higher protein levels examined, but [3-13C]pyruvate decarboxylation and TCA cycle metabolism was the principal fate of [3-13C]alanine following transamination, and dietary carbohydrate was the principal source of glucose for trehalose synthesis. Feeding studies established a relationship between nutritional status, blood sugar level and dietary self-selection. Insects preconditioned by feeding on diets without sucrose had low blood sugar levels regardless of dietary casein level, and when subsequently given a choice between a sucrose diet or a casein diet, selected the former. Larvae preconditioned on a diet containing sucrose and the lowest level of casein had high blood sugar levels and subsequently selected the casein diet. Larvae maintained on the sucrose diet with the highest casein level had low blood sugar and self-selected the sucrose diet. When preconditioned on diets with sucrose and intermediate levels of casein, insects selected more equally between the sucrose and the casein diets. It is concluded that blood sugar level may be intimately involved in dietary self-selection by M. sexta larvae, and that in the absence of dietary carbohydrate, gluconeogenesis provides sufficient blood sugar to ensure that larvae choose a diet or diets that produce an optimal intake of dietary protein and carbohydrate.     

饲料中不同蛋白、脂肪水平对春鲤生长、饲料利用和体成分的影响

研究旨在探讨洱海土著鱼类春鲤(Cyprinus longipectoralis)(初始体重0.55 g)对蛋白质和脂肪的需求量。实验采用3×3双因子设计,蛋白水平为33%、39%和45%,脂肪水平为5%、8%和11%,共9组等能饲料。实验在水温为(28±2)℃的室内微流水系统中进行,为期56d。实验结果表明:随着蛋白水平的提高,摄食率显著降低(P<0.05),饲料效率、能量沉积率、鱼体水分和脂肪含量显著升高(P<0.05),但特定生长率、蛋白质效率、蛋白沉积率、鱼体灰分含量和能值均无显著变化(P>0.05)。随着脂肪水平的提高,特定生长率、蛋白沉积率和鱼体蛋白含量显著下降,鱼体脂肪含量显著上升(P<0.05),而摄食率、饲料效率、能量沉积率、鱼体水分和灰分含量以及能值则无明显变化(P>0.05)。通过折线回归分析得出,当饲料中蛋脂比为7.30时,春鲤有最大的特定生长率。研究结果表明,春鲤饲料中适宜的蛋白和脂肪水平分别为33%—34%和4%—5%。     

Growth performance and body composition of sub-yearling Persian sturgeon, (Acipenser persicus, Borodin, 1897), fed different dietary protein and lipid levels

In order to evaluate the protein and energy requirement of Persian sturgeon (Acipenser persicus) sub‐yearlings, eight experimental diets containing two protein levels (40% and 45%) and four lipid levels (10%, 15%, 20% and 25%) were tested. Sturgeons (W₀ = 136.8 g) were fed the experimental diets to satiation four times daily for 150 days, resulting in a final mean weight of 375.8 g. Growth was significantly affected by lipid content of the diets. At 40% protein level, weight gain and specific growth rate (% per day) were significantly improved (P < 0.05) by increasing the dietary lipid (energy) content. Protein efficiency ratio (PER) was significantly affected by different dietary treatments for each dietary protein level tested, reaching a mean value of 3.58 in fish fed high lipid diets and a PER of 2.77 in low lipid diets. Results obtained in the present study suggest that the optimum dietary protein content for Persian sturgeon is 40%, with an estimated optimum protein‐to‐energy ratio of 18–20 mg kJ⁻¹.     

The responses of rats to various combinations of energy and protein. I. Diets made from purified ingredients

Male and female weanling rats were fed ad libitum for 28 days on purified diets with metabolizable energy levels of 8.0, 9.5, 11.0 or 12.5 MJ/kg and protein:energy ratios of 1:1, 1.33:1, 1.67:1 or 2:1 %:MJ/kg at each energy level. Major nutrients were balanced in proportion to energy and protein. The following parameters were measured: food intake, bodyweight, body length, abdominal fat, liver and kidney weights. Increasing dietary energy level reduced food intake but the reduction was not sufficient to prevent an increase in energy intake. This was reflected by increases in bodyweight, body length, abdominal fat, and relative liver and kidney weights, especially in male rats. Higher energy intake increased weight gain and food conversion efficiency to a greater extent than higher protein intake. The response to protein intake at different energy levels was not consistent. There was no common protein:energy ratio for overall good performance. It is concluded that rat growth and other features can be controlled by the alteration of dietary energy and protein levels.     

Cyclic growth and activity of pancreatic enzymes in alevins of Arctic charr (Salvelinus alpinus L.)

Growth and digestive enzymes were studied in alevins of Arctic charr raised on six commercial diets that differed in protein source and level. There were links between diet composition (protein quality), fish performance and proteolytic and amylase enzyme activities. Trypsin and amylase activities were up to 10-fold higher in charr fed high protein (65–70%) diets than in fish fed live feed. A depression of pancreaticenzyme activities was noticeable when charr were fed starter diets in which fish meal was partially replaced by soybean meal. Specific growth rates (SGR) showed a cyclic pattern during early ontogeny of charr and SGR was highly correlated with food conversion efficiency. Activities of pancreatic enzymes also demonstrated a cyclic pattern but the periodicities of the growth cycle (50.6 days) and those of the enzymes differed. We hypothesize that both photostimulation and feedback responses might be involved in pancreatic responses in fish, which result in cyclic growth patterns.     

Effects of dietary protein and lipid levels on growth and feed utilization of wild‐caught striped sea bream,Lithognathus mormyrus

A feeding trial was carried out to determine the effects of dietary protein and lipid levels on the growth performance and feed utilization of wild‐caught striped sea bream (Lithognathus mormyrus). The experimental fish were collected from a local lagoon (Çardak Lagoon, Çanakkale, Turkey), transferred to the Marine Net Cage Unit and fed by hand to apparent satiation with a commercial sea bream feed (Biomar; 42% crude protein, 16% crude lipid). Approximately 4 weeks were needed to acclimate the fish to farming conditions. No pathological signs were observed and no fish losses occurred during the adaptation period. For the test trials four test diets with different levels of protein and lipid were formulated [low protein and low lipid (LP:LL), low protein and high lipid (LP:HL), high protein and low lipid (HP:LL), and high protein and high lipid (HP:HL)] and fed to L. mormyrus (mean weight 85.0 ± 4.6 g SEM) in the net cages (Ø 2 m, depth 2.5 m) for 60 days. During the experiment water temperature varied between 21.1 and 26.4°C; dissolved oxygen 8.4–9.6 mg L^?1; pH 7.2–8.6; and salinity 23.3–25.6‰. Growth performances of fish fed high protein diets were higher compared to fish fed low protein diets, irrespective of the dietary lipid level (P < 0.05). Feed conversion ratio (FCR) and protein efficiency ratio (PER) were not influenced by dietary protein or lipid levels (P > 0.05). Preliminary results indicate that striped sea bream can be easily adapted to farming conditions in net cages, and that a diet containing 50% crude protein and 15% crude lipid (HP:LL) levels with 23.0 g protein MJ^?1 gross energy of protein/energy ratio would be suitable for striped sea bream growth.     

Effects of dietary soybean protein levels on metabolic response of the southern catfish, Silurus meridionalis

A closed respirometer was used to measure oxygen consumption of the southern catfish Silurus meridionalis fed with six isonitrogenous (48% crude protein) diets replacing 0%, 13%, 26%, 39%, 52% and 65% fish meal (FM) protein by soybean meal (SBM) protein, in order to investigate the effects of dietary soybean protein level (SPL) (replacing FM) on metabolic rates of the southern catfish. The results showed that there were no significant differences in routine metabolism among dietary treatments. Either the total metabolic rate or specific dynamic action (SDA) was positively correlated with assimilated food energy at each diet, respectively (P<0.05). The SDA coefficient (means the energy spent in metabolism per unit of assimilated dietary energy) significantly increased with increasing dietary SPL (P<0.05). Fish fed the diet with 13% SPL had a significantly lower SDA coefficient (0.1528) than fish fed the diet with 52% or 65% SPL (0.1826 or 0.1932) (P<0.05). However, there were no significant differences in SDA coefficient among fish fed the diets with 13%, 26% and 39% SPL (P>0.05). Results of the present study suggested that an imbalance of essential amino acids at higher dietary SPL resulted in more energy channeled into metabolism, and subsequently increased the SDA coefficient.     

The effect of magnesium and manganese uptake and accumulation on oxygen consumption and ammonia excretion in Porcellio spinicornis Say (Porcellionidae, Isopoda)

Mean concentrations of Mg and Mn in whole intermoult 7th growth-stage Porcellio spinicornis are positively correlated with dietary levels up to and including 1,000 ppm of these two trace metals. Lower tissue concentrations in isopods on 1,500 ppm diets are related to either a low food intake or a higher rate of metal excretion. Mean Mg concentration in whole isopods at the end of 7 days ranged from 27 388.26 +/- 598.56 micrograms/g dry tissue in the control to 69 122.08 +/- 31 682.98 micrograms/g dry tissue in the 1,000 ppm dietary group; in the 1,500 ppm dietary group, it amounted to 25 630.26 +/- 13 102.12 micrograms/g dry tissue. Mean Mn concentration varied from 85.53 +/- 11.23 micrograms/g dry tissue in the control to 229.05 +/- 32.33 micrograms/g dry tissue in 1,000 ppm dietary group; in the 1,500 ppm dietary group, it amounted to 199.57 +/- 18.99 micrograms/g dry tissue. Differences between the two sexes were significant at 5% level. Oxygen consumption was negatively and ammonia excretion was positively related to the dietary metal concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)     

饲料蛋氨酸水平对异育银鲫幼鱼生长性能影响的研究

研究通过8周的生长实验, 研究饲料中不同蛋氨酸水平对异育银鲫(Carassius auratus gibelio)幼鱼生长性能、体成分、氨基酸沉积率的影响。实验以鱼粉、豌豆浓缩蛋白、喷雾干燥血球粉为蛋白源, 设计低蛋氨酸(0.57%)实用基础饲料, 并在此基础上分别添加0、0.08%、0.16%、0.24%、0.32%、0.40%的DL-蛋氨酸配成蛋氨酸含量分别为0.57%、0.64%、0.74%、0.81%、0.88%、0.95%(干物质基础, 实测值)的6种等氮等能(粗蛋白质: 37.22%, 总能: 17.61 MJ/kg)的配合饲料。选取初始体重为2.60 g的异育银鲫幼鱼为实验对象, 每个处理3个重复, 每个重复50尾鱼, 养殖系统为室内循环水养殖系统, 每天表观饱食投喂4次。结果显示在饲料中补充DL-蛋氨酸会显著提高异育银鲫幼鱼的特定生长率和蛋白质沉积率(P0.05), 表明异育银鲫可有效利用外源DL-蛋氨酸。各处理组实验鱼肥满度、肝体比、脏体比差异不显著(P0.05), 不同蛋氨酸水平对全鱼水分、粗脂肪、能量没有产生显著影响(P0.05), 补充DL-蛋氨酸显著提高鱼体的粗蛋白质含量, 灰分含量显著降低(P0.05)。随着饲料中蛋氨酸水平的提高, 全鱼蛋氨酸沉积率显著降低, 之后再升高(P 0.05)。补充DL-蛋氨酸可以有效促进其他必需氨基酸在鱼体内的沉积。在饲料中胱氨酸水平为0.42%时, 通过折线模型回归分析, 以蛋氨酸沉积率得到的异育银鲫幼鱼蛋氨酸需求量为占饲料干物质的0.89%, 即占饲料蛋白的2.17%。       

Diet selection by red-backed voles<Emphasis Type="Italic">Clethrionomys gapperi</Emphasis>

Food supplementation studies often assume that animals will select artificial diets in their natural environment, and that high-protein, high-energy foods are the most appropriate supplement. These assumptions were tested in red-backed volesClethrionomys gapperi Vigors, 1830 using food-choice experiments with sunflower seeds, oats, and commercial diets in the laboratory and field. Preferred level of dietary protein was also examined using isocaloric diets that varied only in protein content (14%, 20% and 30%). Preferences exhibited in the above trials were subsequently examined relative to natural forage. Voles demonstrated a strong preference for sunflower seeds over oats, dried alfalfa, and rabbit, guinea pig, rat and cat food. Voles preferred the 14% protein diet over the 20% and 30% protein diets. Although sunflower seeds contain more than 20% protein, voles consistently preferred this food over natural forage, perhaps because of their high fat and energy content. This indicates that tradeoffs in protein content may be made to maximize energy. We suggest that red-backed voles will select sunflower seeds in their natural environment, and that their preference for low protein likely reflects their herbivorous diet. This study highlights the importance of ana priori understanding of species-specific preferences and requirements when designing food supplementation studies.