饲粮赖氨酸水平对产蛋高峰期临武鸭生产性能、蛋品质、血清生化指标及氮代谢的影响

本试验旨在研究饲粮赖氨酸水平对产蛋高峰期(30~38周龄)临武鸭生产性能、蛋品质、血清生化指标及氮代谢的影响,以确定产蛋高峰期临武鸭赖氨酸需要量。试验选取体重相近、健康状况良好、产蛋率无显著差异(P0.05)的临武鸭200羽,随机分为5组,每组5个重复,每个重复8只鸭。饲粮中赖氨酸水平分别为0.65%、0.75%、0.85%、0.95%、1.05%,试验期63 d。在饲养试验结束后,每组挑选出10只体重接近各组平均体重的试验鸭进行代谢试验。结果显示:1)0.95%和1.05%赖氨酸组日产蛋重显著高于0.65%和0.75%赖氨酸组(P0.05),而0.95%和1.05%赖氨酸组料蛋比显著低于0.65%和0.75%赖氨酸组(P0.05)。2)饲粮赖氨酸水平对蛋品质无显著影响(P0.05)。3)0.85%、0.95%和1.05%赖氨酸组血清总蛋白含量显著高于0.65%赖氨酸组(P0.05)。0.95%赖氨酸组血清中三碘甲腺原氨酸含量显著高于0.65%、0.75%和1.05%赖氨酸组(P0.05)。4)0.95%赖氨酸组净蛋白质利用率和氮沉积量显著或极显著高于0.65%赖氨酸组(P0.05或P0.01)。5)二次曲线分析表明,以总蛋白、净蛋白质利用率和氮沉积为评价指标,产蛋高峰期临武鸭饲粮中赖氨酸需要量分别为0.92%、0.96%和0.95%。由此可见,30~38周龄临武鸭的日产蛋重、料蛋比、总蛋白、净蛋白质利用率和氮沉积对于饲粮中赖氨酸水平的变化较为敏感,而获得较佳的生产性能、血清生化指标和氮平衡的适宜赖氨酸水平为0.92%~0.96%。     

近红外光谱技术快速测定豆粕、玉米真可消化氨基酸含量的研究

本试验应用近红外光谱技术（ＮＩＲＳ）预测了豆粕、玉米中的真可消化氨基酸含量。氨基酸消化率用去盲肠公鸡作试验动物,用修正的Ｓｉｂｂａｌｄ强饲法进行测定。定标的结果表明,豆粕中除与胱氨酸有关的几个方程外,其它氨基酸的定标经检验证明具有良好的预测性能。玉米真可消化氨基酸的定标性能不如豆粕好,目前还不能进行实际的应用,但大部分氨基酸定标方程的相关系数经Ｆ检验达到极显著水平,说明用ＮＩＲＳ预测玉米真可消化氨基酸是可行的。近红外光谱技术提供了一种可用于日常测定鸡真可消化氨基酸的即时分析方法,它能够替代查书面值以及使用耗时而昂贵的体内法测定真可消化氨基酸含量。营养学家可根据真可消化氨基酸数据进行饲料配方,起到准确、及时、低投入、高产出、低污染、高效利用饲料资源的作用。     

低蛋白饲粮不同添加物对生长育肥猪生产性能的影响

本试验通过降低生长育肥猪饲粮蛋白质水平2个百分点,其它营养水平不变,并在低蛋白饲粮中添加赖氨酸及复合促生长剂1号,共5周的饲养进行对比试验。结果表明：在低蛋白饲粮中添加复合促生长剂1号,能够显著提高生长育肥猪的日增重、饲料转化率及经济效益,并能超过高蛋白饲粮组;在低蛋白粮中添加赖氨酸,可提高生长育肥猪的日增重、饲料利用率及经济效益,但达不到高蛋白饲粮饲喂水平。     

Do plant‐based diets for Atlantic cod (Gadus morhua L.) need additions of crystalline lysine or methionine?

Atlantic cod (Gadus morhua), initial weight 15 g, were fed ten experimental diets for 15 weeks. The diets were based on a mixture of plant proteins (PP) and fish meal (FM), where PP constituted 65% of dietary protein. PP mixtures were chosen to reach as low levels of lysine and methionine as possible. The diets were supplemented with increasing amounts of lysine (19.2–31.9 g kg^?1 diet) or methionine (9.4–12.3 g kg^?1 diet), in a regression design. No growth difference among diet groups was found in the plant‐based diets. Increased dietary lysine resulted in decreased liver size, plasma triacylglycerol concentration (TAG) and lipid productive value (LPV). Methionine additions did not result in changed Hepatosomatic index (HSI), LPV or plasma TAG. Feed conversion ratio (FCR) and protein utilization were neither affected by lysine nor methionine. Plasma and muscle concentrations of free lysine and methionine correlated with dietary levels 5‐h post feeding. Overall conclusion was that cod maintain growth rates in plant‐based diets if dietary protein was high, without additional supplements of crystalline lysine or methionine. Lysine intake significantly influenced lipid metabolism, showing the necessity to add lysine in plant protein‐based diets to hinder increased lipid deposition. No such effects were found because of lack of methionine additions.     

High dietary energy level stimulates growth hormone receptor and feed utilization in large Atlantic salmon (Salmo salar L.) under hypoxic conditions

This study examines how appetite and growth regulation of Atlantic salmon are affected by low dissolved oxygen (LO) and dietary digestible energy levels (DE: high [HE] vs. low [LE]). Long‐term exposure to LO resulted in a reduced feed intake, growth, digestible protein and fat retention efficiencies and increased feed conversation ratio and plasma ghrelin concentrations (p < .05) compared to high dissolved oxygen (HO). Pair‐feeding of rations based on the feed intake of the LO groups, but fed at HO, resulted in a 50% growth improvement in HE diet groups. This suggests that the poor growth under LO was not entirely caused by the reduced feed intake. Salmon adapted to LO by increased haemoglobin concentrations, while osmoregulation was affected by increased plasma chloride concentrations (p < .05). Plasma ghrelin concentration was unaffected by DE (p > .05). Growth regulation was affected by the HE diet, with increased liver and muscle growth hormone receptor ghr1 mRNA (p < .05), regardless of oxygen level. The growth depression due to low oxygen appears to be related to higher metabolic costs, while higher DE upregulates the GH‐IGF system at the ghr1 level and found to be beneficial for growth, feed intake, oxyregulation and osmoregulation under hypoxia.     

Linear models to predict the digestible lipid content of fish diets

Values for the digestible contents of nutrients in diets and feed ingredients are of utmost importance in nutritional strategies for fish. Prediction from dietary composition would eliminate lengthy, tedious and demanding digestibility experiments with fish. Apparent digestible lipid (DL) content [range 7.6–353.4 g kg⁻¹ dry matter (DM)] in compound diets can be predicted with high accuracy ( n  = 610; studies =127; fish species = 34; R ² = 0.9515; RMSE = 16.9504) from dietary crude lipid (CL) content (range 12.0–388.7 g kg⁻¹ DM) by the linear regression equation DL =−2.7303 + 0.9123 CL. Validation of this equation against 65 values from 15 independent studies presented R ² and mean prediction error (MPE) values of 0.9947 and 0.0671, respectively. The corresponding equation for 37 individual feed ingredients evaluated in 24 studies with 18 fish species ( n  = 180) was found to be DL = −1.5824 + 0.8654 CL ( R ² = 0.9717; RMSE = 8.3765). However, validation of the latter is currently hampered by a lack of independent values.     

Appetite,metabolism and growth regulation in Atlantic salmon (Salmo salar L.) exposed to hypoxia at elevated seawater temperature

High temperature combined with low dissolved oxygen (DO) is one of the most challenging environmental conditions farmed fish experience; thus, understanding their impact on growth regulation is of relevance to cultured and wild populations. This study examines appetite‐ and growth‐regulating mechanisms in Atlantic salmon postsmolt exposed to either high (HO) or low oxygen (LO) at a suboptimally high temperature (17°C). Additionally, the effects of high (HE) and low (LE) dietary energy (DE) were examined. After a month of treatment, analyses of hormones, regulating appetite (ghrelin) and growth (growth hormone receptor ghr1 and insulin‐like growth factor IGF‐1), and free amino acids (FAA) were measured pre‐ and postprandially at ?4, ?2, 0, 2, 4 and 6 h. No preprandial ghrelin peaks were detected despite a significant reduction in feed intake and growth under hypoxia compared to normoxia. LO treatment also had an overall negative effect on survival compared to HO, while nutrient retention efficiency, FCR and plasma FAA concentrations were unaffected (P > 0.05). Feeding HE diet resulted in increased growth (+17%) and improved FCR (?14%) and energy retention efficiency (+26%) independent of DO. Plasma FAA concentrations were unaffected by LO treatment and DE (P > 0.05). Growth regulatory gene expressions possibly reflect an overall lower growth at a high temperature overriding the impacts of DO and DE. This study also indicates that optimal adaptation time to environmental conditions and feeding regime is crucial for establishing a regular hormonal appetite signalling that reflects real feeding anticipation in salmon.     

低蛋白质饲粮补充过瘤胃赖氨酸和过瘤胃蛋氨酸对荷斯坦公牛生长性能、屠宰性能、肉品质及氮代谢的影响

本试验旨在研究低蛋白质饲粮补充过瘤胃赖氨酸(RPLys)和过瘤胃蛋氨酸(RPMet)对荷斯坦公牛生长性能、屠宰性能、肉品质及氮代谢的影响.选取36头健康无疾病的荷斯坦公牛,随机分为3组,每组12头牛.对照组(Ⅰ组)饲喂蛋白质水平为13％的正常饲粮,2个试验组(Ⅱ、Ⅲ组)均饲喂蛋白质水平为11％的低蛋白质饲粮,同时Ⅱ组补...     

中华绒螯蟹对赖氨酸、蛋氨酸和精氨酸的需要量

试验以酪蛋白、白鱼粉、豆粕和晶体氨基酸为蛋白源,配制了15组试验饲料,分别测定了中华绒螯蟹幼蟹对赖氨酸(Lys)、蛋氨酸(Met)和精氨酸(Arg)的需要量。养殖试验在室内玻璃纤维水族缸中进行,试验水温为(28±3.0)℃,pH为7.4左右,试验周期为56 d。试验组1～试验组5为Lys试验,试验组6～试验组10为Met试验,试验组11～试验组15为Arg试验,试验用蟹平均初重分别为:Lys试验(2.050±0.027)g,Met试验(2.027±0.033)g,Arg试验(2.05±0.032)g。每个试验设5个氨基酸梯度,其中Lys梯度为:1.58%、1.98%、2.38%、2.78%和3.18%;Met梯度为:0.50%、0.75%、1.00%、1.25%和1.50%;Arg梯度为:1.39、2.09、2.79、3.49和4.19%。每个梯度设3重复。试验结果表明,Lys试验中,试验组3(含2.38% Lys)获得最大的增重率和特定生长率,但与试验组2(1.98%Lys)和试验组4(2.78%Lys)之间没有显著性差异;且试验组3的全蟹水分含量显著较低,而蛋白质含量显著较高(P<0.05)。Met试验中,试验组8(含1.00% Met)的增重率和特定生长率显著较高(P<0.05),而其它试验组的增重率和特定生长率差异不显著(P>0.05);试验组10 全蟹水分含量显著较高,而粗蛋白含量显著较低(P<0.05)。Arg试验中,试验组14(日粮含3.49% Arg)的增重率和特定生长率显著高于其它试验组(P<0.05);而各试验组间全蟹营养组成均没有显著性差异。根据试验的生长反应和二次曲线回归分析,确定了中华绒螯蟹幼蟹饲料中最适赖氨酸、蛋氨酸和精氨酸的需要量分别为2.34%,1.12% 和 3.62%。     

Lysine limitation alters the storage pattern of protein,lipid and glycogen in on‐growing Atlantic salmon

This experiment aimed to test the interaction of lysine limitation with nutrient accretion and muscle carnitine depot in Atlantic salmon. Fish were fed adequate or low‐lysine diets for 3 months. Lysine intake was significantly less (48%) in fish fed the low‐lysine diet as compared with that fed the adequate one. There was no difference in dietary amino acids between treatments, with the exception of lysine. The lower lysine intake was reflected in plasma free lysine being 52% less while the free lysine concentration in the liver and muscle were unaffected. Although there was no significant difference between voluntary feed intakes among treatments, fish fed the low‐lysine diet had reduced growth, protein and energy deposition as compared with fish fed the adequate lysine diet. White trunk muscle contained more glycogen and less protein in fish fed the low‐lysine diet while no difference in lipid was observed. The livers from fish fed the low‐lysine diet contained less glycogen and slightly more fat and protein than the livers from fish fed the adequate lysine diet. Lysine limitation reduced carnitine in the liver without affecting muscle carnitine depot. Thus, low‐lysine diets did not likely affect the fatty acid oxidation capacity. This fact was supported by unaffected fatty acid profiles and lipid classes between treatments during the 3‐month study. In conclusion, lysine limitation does not deplete the muscle carnitine depot during the on‐growing seawater phase of Atlantic salmon, but affects the deposition pattern of nutrients.