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%。       

Effect of normal and waxy maize starch on growth, food utilization and hepatic glucose metabolism in European sea bass (Dicentrarchus labrax) juveniles

We determined the effect of dietary starch on growth performance and feed utilization in European sea bass juveniles. Data on the dietary regulation of key hepatic enzymes of the glycolytic, gluconeogenic, lipogenic and amino acid metabolic pathways (hexokinase, HK; glucokinase, GK; pyruvate kinase, PK; fructose-1,6-bisphosphatase, FBPase; glucose-6-phosphatase, G6Pase; glucose-6-phosphate dehydrogenase, G6PD; alanine aminotransferase, ALAT; aspartate aminotransferase, ASAT and glutamate dehydrogenase, GDH) were also measured. Five isonitrogenous (48% crude protein) and isolipidic (14% crude lipids) diets were formulated to contain 10% normal starch (diet NS10), 10% waxy starch (diet WS10), 20% normal starch (diet NS20), 20% waxy starch (diet WS20) or no starch (control diet). Another diet was formulated with no carbohydrate, and contained 68% crude protein and 14% crude lipids (diet HP). Each experimental diet was fed to triplicate groups of 30 fish (initial weight: 23.3 g) on an equivalent feeding scheme for 12 weeks. The best growth performance and feed efficiency were achieved with fish fed the HP diet. Neither the level nor the nature of starch had measurable effects on growth performance of sea bass juveniles. Digestibility of starch was higher with waxy starch and decreased with increasing levels of starch in the diet. Whole-body composition and plasma metabolites, mainly glycemia, were not affected by the level and nature of the dietary starch. Data on enzyme activities suggest that dietary carbohydrates significantly improve protein utilization associated with increased glycolytic enzyme activities (GK and PK), as well as decreased gluconeogenic (FBPase) and amino acid catabolic (GDH) enzyme activities. The nature of dietary carbohydrates tested had little influence on performance criteria.     

Pea protein concentrate in diets for sharpsnout sea bream (Diplodus puntazzo): effects on growth and health status

Four diets for sharpsnout sea bream juveniles (14 g body weight) with four levels of air-processed pea protein concentrate (PPC) (0, 160, 320 and 487 g/kg diet) were tested in triplicate. The experimental diets were isonitrogenous (43% crude protein) and isolipidic (19% ether extract) and the fish were fed to satiation twice a day. After 125 d, fish growth was diminished by the inclusion of PPC. Feed conversion did not show significant differences in any treatment. Neither the body analyses nor the protein and individual essential amino acid retention efficiencies were affected by the inclusion of PPC in the diet. However, histological gut examinations revealed noticeable differences. Fish fed the diet with the highest inclusion level of PPC presented the longest villous length and the most goblet cells, and the width of the lamina propria increased in the anterior intestine. Although no negative changes in nutritive parameters were detected, these alterations might affect nutrient transport, with negative consequences for fish growth. It was concluded that the PPC in the amounts tested here is an inappropriate substitute for fishmeal in diets for sharpsnout sea bream juveniles.     

Utilization of copra meal in the formulation of compound diets for rohu, Labeo rohita, fingerlings

Six isonitrogenous (35% crude protein) experimental diets were formulated with raw and soaked de-oiled copra meal substituted for fish meal in the diet at 20, 30 and 40% levels by weight. The tannin content of raw de-oiled copra meal was reduced from 2.4 to 0.9% by soaking it in water for 16 h at room temperature. The response of rohu, Labeo rohita (Hamilton), fingerlings fed these diets for 80 days was compared with fish fed a fish meal-based control diet. On the basis of growth response, food conversion ratio and protein efficiency ratio, the 30% soaked copra meal diet resulted in the best fish performance (P < 0.01). The growth response of the fish was significantly (P < 0.01) affected by both type and inclusion level of the oilseed meal. The growth of fish declined with the increasing level of inclusion of copra meal, irrespective of the type of meal used. The apparent protein digestibilities (APDs) for the raw copra meal were lower at all levels of inclusion in comparison with those for the soaked meals. The highest amount of carcass protein was recorded in the fish fed the diet containing 30% soaked copra meal. The results showed that de-oiled copra meal can be incorporated into carp diets up to 20% in the raw condition and up to 30% in the treated condition without any deleterious effects on growth performance of Labeo rohita fingerlings.     

Variation in digestive efficiency of captive North American river otters (Lontra canadensis) on various diets

Energy content, proximate nutrient values, passage rate, and digestive efficiency associated with various diet types and factors affecting these parameters have not been quantified for the North American river otter (Lontra canadensis). We measured energy digestive efficiency (DEff) and intestinal passage rate of three captive river otters on their regular diet (a combination of polar bear diet, cat food, and feline diet) and on test diets consisting of the constituent components of their regular diet. Gross energy, crude protein, crude fat, and crude fiber varied appreciably among diet components. Caloric DEff values were high (cat food and polar bear diet combination: 83.11%; regular diet: 86.62%; feline diet: 90.22%) indicating diets high in fat and protein permit greater energy absorption. Passage rates ranged from 167–188 minutes and were influenced by level of activity such that passage rate was more rapid at higher levels of activity. Coefficients of variation (CV) from DEff (CV=1.51) and digesta passage rates (CV=7.35) were dissimilar, indicating that a direct measure may yield a more precise estimate of absorption over digesta passage rates. To further understand energy handling by river otters on diets used in zoologic institutions and to better provide the nutrient dense diets this active species requires, additional studies quantifying energetic parameters for captive otters of various genders, ages, and reproductive conditions on other diet types are needed. Zoo Biol 0: 1–10, 2007. © 2006 Wiley‐Liss, Inc.     

Effect of water temperature and dietary starch on growth and metabolic utilization of diets in gilthead sea bream (Sparus aurata) juveniles

We evaluated the effect of dietary starch level on growth performance, feed utilization, whole-body composition and activity of selected key enzymes of intermediary metabolism in gilthead sea bream juveniles reared at 18 and 25 degrees C. A diet was formulated to contain 48% crude protein, 12% lipids and 30% gelatinized maize starch (diet 30GS). Two other diets were formulated to include the same level of ingredients as diet 30GS except for the gelatinized starch, which was included at 20% (diet 20GS) or 10% (diet 10GS). No adjustment to diet composition was otherwise made. Each diet was fed to triplicate groups of gilthead sea bream (30 g initial mass) for 8 weeks, on a pair-feeding scheme. The higher temperature improved growth performance but the opposite was true for feed efficiency and protein efficiency ratio. Independently of temperature, growth performance, feed efficiency and protein efficiency ratio were lower in fish fed diet 30GS. No effect of temperature or dietary starch level on whole-body composition was noticed. Hepatosomatic index and liver glycogen were higher at 18 degrees C and, within each temperature, in fish fed diet 30GS. Glycemia was not affected by temperature, but was lower in fish fed diet 10GS. Data on enzyme activities showed that increasing water temperature enhances liver glucokinase (GK) and pyruvate kinase (PK) activities, suggesting that gilthead sea bream is more apt to use dietary starch at higher temperatures. No effect of temperature was noticed on hexokinase (HK), fructose-1,6-bisphosphatase (FBPase), glucose-6-phosphate dehydrogenase (G6PD) and glutamate dehydrogenase (GDH) activities. Dietary starch enhanced PK and FBPase activities while depressed GDH activity, suggesting a lack of significant regulation of hepatic glucose utilization and production in this species. HK, GK and G6PD activities were unaffected by dietary composition. Irrespectively of water temperature, gelatinized starch may be included up to 20% in diets for gilthead sea bream juveniles; at higher dietary levels, growth and efficiency of feed utilization are depressed.     

Nutritive value of melon husk in the diet of chickens.

A study was conducted to investigate the nutritive value of melon husk (MH). Results showed that MH was low in crude protein but very high in crude fibre, ash and ether extract. The elemental analysis showed that MH was also high in calcium and phosphorus content. However, when MH was incorporated into starter diets of chicks, body weight gain decreased with increase in the level of MH in the diets. Birds fed on a 10% MH diet were superior to others in body weight gain (10.45 g/bird/day). Results of feed intake and efficiency of feed utilization were also superior on 10% MH diet with values of 43.07 g/bird/day and 4.12 recorded, respectively. The dietary treatment had significant effect (p < 0.05) on the protein efficiency ratio, which decreased with increase in level of MH in the diets. However, there appeared to be no treatment effects on haematological parameters. Up to 10% MH can replace maize in the starter diet of cockerels without adverse effect on performance.     

Meat meal in the diet of the early-weaned pig. II. Amino acid supplementation

One hundred and twenty pigs, initially 4–5 kg liveweight, were fed on wheat-based diets supplemented with meat meal and amino acids in two experiments, each of 4 weeks duration.In the first experiment, the supplementation of a normal meat meal diet with lysine and methionine increased the feed intake and weight gains of the pigs by 15 and 18%, respectively. Nitrogen retention was increased by 30%. Tryptophane gave a similar response to lysine and methionine.In the second experiment, a 21% crude protein basal diet was similar to the basal diet of the first experiment but it contained 1.02% lysine and 0.50% methionine plus cystine, compared to 0.90 and 0.51%, respectively, in the first experiment. Lysine and methionine supplementation of the diet did not significantly improve the performance of the pigs in the second experiment, but the supplementation of the diets with 0.08% tryptophane and lysine and methionine increased weight gains and feed intakes and decreased urea content of the blood plasma. The 21% crude protein diet contained 0.15% tryptophane.Increasing the crude protein content of diets from 18 to 24% by increasing their meat meal content increased the daily weight gains from 190 to 276 g.     

Development of a diet for long-term raising of F344 rats--relationship between dietary digestible crude protein content and digestible energy content.

Mice and rats are frequently subjected to long-term raising in studies of aging. These animals are usually given growing or breeding diets from a young age. This raising method causes diseases such as chronic nephropathy with proteinuria due to nutritional excess. Consequently, a long-term raising study on male F344/DuCrj rats using nine sorts of diets differing in crude protein (CP; 12, 28, 44%) and digestible energy (DE; 2.8, 3.7, 4.5 kcal/g) contents was carried out. It was found that feed consumption was regulated by DE, not digestible crude protein (DCP) intake. Body weight was controlled within low energy areas, and was not influenced by feed or DCP intake. The liver and kidney weight at 105 weeks of age increased in response to an increase in the level of CP in the diet. Chronic nephropathy was severe in rats fed high protein diets and moderate levels of protein with moderate to high energy diets. Fatty liver and bile duct hyperplasia were found in rats fed a high protein and high energy diet. Few pathological findings of kidney and liver were found in the low protein and low energy diet group. The reduction of disorders attributable to excess energy or inappropriate diet suggests that low protein and low energy diets are most suitable for long-term raising in this strain of rat.     

不同粗蛋白含量日粮对Beagle犬生产力的影响

用4种不同粗蛋白含量的日粮饲喂60条2～3岁Beagle犬种犬(♀48,♂12)和200条(♀,♂各半)1～8月龄生长犬,对种母犬2～3胎的主要繁殖性能和生长犬的生长性能(体重月平均增加)进行测定.结果 表明饲喂粗蛋白含量水平为28.6%的日粮,受试母犬表现出优良的繁殖性能:配怀率98.5%、平均产仔数6.3条/胎、仔犬成活率90.3%;1～8月龄生长Beagle犬饲喂粗蛋白含量水平为32.8%为最佳,平均月增重为1.41 kg.说明不同粗蛋白含量日粮对Beagle犬生产力有明显的影响.     

Improvement of nutritive value of grass pea (Lathyrus sativus) seed meal in the formulated diets for rohu, Labeo rohita (Hamilton) fingerlings after fermentation with a fish gut bacterium

Eight isonitrogenous (35% crude protein approximately) and isocaloric (4.0 kcalg(-1) approximately) diets were formulated incorporating raw and fermented grass pea (Lathyrus sativus) seed meal at 10%, 20%, 30% and 40% levels by weight into a fish meal based diet and fed to rohu, Labeo rohita, fingerlings for 80 days and fish performance was studied. A particular bacterial strain (Bacillus sp.) isolated from the intestine of adult common carp (Cyprinus carpio) reared in the wild having significant amylolytic, cellulolytic, lipolytic and proteolytic activities were used for fermentation of seed meal for 15 days at 37 degrees C. Fermentation of grass pea seed meal was effective in significantly reducing the crude fibre content and anti-nutritional factors, such as tannins, phytic acid and the neurotoxin, beta-ODAP and enhancing the available free amino acids and fatty acids. In terms of growth response, feed conversion ratio and protein efficiency ratio, 30% fermented grass pea seed meal incorporated diet resulted in significantly (P < 0.05) better performance of rohu fingerlings. In general, growth and feed utilization efficiencies of fish fed diets containing fermented seed meal were superior to those fed diets containing raw seed meal. The apparent protein digestibility (APD) values decreased with increasing levels of raw seed meal in the diets. The APD for raw seed meal was lower at all levels of inclusion in comparison to those for the fermented seed meals. The highest deposition of carcass protein was recorded in fish fed the diet containing 40% fermented seed meal. The results indicated that fermented grass pea seed meal can be incorporated in carp diets up to 30% level compared to 10% level of raw seed meal.     

Sulphur amino acid requirement of juvenile Asian sea bass Lates calcarifer

The dietary requirement of juvenile Asian sea bass Lates calcarifer Bloch for total sulphur amino acids was studied. Fish (average initial weight of 2.59 ± 0.08 g) were reared in twelve 500 L fibreglass tanks provided with flow-through seawater at 26°C and salinity of 31 p.p.t. for 12 weeks. They were fed semi-purified test diets containing 6.2, 7.2, 8.1, 9.0, 10.8, or 12.6 g methionine kg⁻¹ dry diet and a basal level of 3.1 g cystine kg⁻¹ dry diet. The mean crude protein of the diets (containing defatted Peruvian fishmeal, squid meal, soybean meal, and free amino acid mixture to simulate the pattern of hydrolysed sea bass protein) was 46.02%. The crude fat content of the diets was 10.51% from a 1 : 1 mixture of cod liver oil and soybean oil. Survival was 100% in all treatments. On the basis of the growth response, the total sulphur amino acid requirement of juvenile Asian sea bass was estimated to be 13.4 g kg⁻¹ dry diet (2.9% of protein). Fish fed low levels of l -methionine had significantly lower weight gains and feed efficiency ratios as well as slightly higher hepatosomatic indices. No nutritional deficiency signs were observed other than growth depression in fish fed on diets that were low in methionine. This information is valuable in further refinement of formulations of practical diets for the Asian sea bass.     

Brugia pahangi: Growth improvement with lecithin in the diet of axenically reared hosts, Aedes aegypti

Growth and development of the filarial nematode Brugia pahangi was examined in Aedes aegypti mosquitoes axenically reared on defined synthetic dietary media containing crude animal lecithin and synthetic dipalmitoyl lecithin. The first was a crude preparation containing impurities (mostly lipids) up to 40%, while the second was a highly purified preparation of lecithin (99.95%). Substantial proportions of apparently alive but undeveloped prefirst-stage parasite juveniles (presausage forms) were found in mosquitoes reared on all synthetic dietary media but not in mosquitoes reared on liver powder (control). Of the two lecithin preparations tested, parasites grew best in mosquitoes reared on a diet augmented with crude animal lecithin. Development was synchronized and the filarial parasites were able to complete two molts to become third-stage juveniles. Synthetic dl-dipalmitoyl lecithin in mosquito diets did not improve filarial development. The improvement of worm growth in terms of rate of morphogenesis and facility in molting, with the addition of crude, and not the pure lecithin preparation, suggested that the effect observed on filariae may not be directly due to the lecithin molecule, but due to a compound (probably a lipid), associated with the lecithin molecule in the crude preparation.     

Growth performance and body composition in response to dietary protein and lipid levels in Nile tilapia (Oreochromis niloticus Linnaeus, 1758) subjected to normal and temporally restricted feeding regimes

A factorial experiment was designed to examine the effect on compensatory growth (CG) of Nile tilapia Oreochromis niloticus fed diets containing different protein and lipid levels under normal and temporally restricted feeding regimes. Four diets were formulated to contain either 30% or 36% crude protein, and 5% or 11% crude lipid. Triplicate replicates of each treatment were assigned to 24 150‐L tanks (20 fish/tank density). Fish (mean initial weight ± SD = 8.79 ± 0.34 g) were then fed either the normal feeding regime (thrice daily to apparent satiation) or the restricted regime (1 day feed deprivation followed by 3 days of feeding to apparent satiation) over a 44‐days study period. Fish receiving a diet under the restricted regime achieved weight gains (WG) comparable to fish consuming the diet containing 30% protein and 5% lipids under the normal feeding regime. Fish maintained on the restricted feeding regime exhibited reduced feed intake (FI), WG, feed efficiency ratio (FE), protein efficiency rate (PER) and hepatosomatic index versus fish on the normal feeding regime, except WG in fish fed the diet with 30% protein and 5% lipids. However, the resultant FI (85%~94%) was higher than the excepted 75% intake when fish were subjected to the restricted regime. Feeding 11% lipid diets led to improved FI, WG, FE, and PER compared to feeding the 5% lipid diets. Increased FI, WG, and FE, but reduced PER were observed in fish fed with 36% protein versus fish fed 30% protein. Fish receiving the 36% protein diets had lower whole‐body moisture and ash contents, but elevated whole‐body protein and lipid contents compared to those receiving the 30% protein diets. Whole‐body moisture contents were lower, but whole‐body protein, lipid and ash contents were higher in fish fed 11% lipid diets than in fish fed 5% lipid diets. There was an increase in whole‐body moisture content, but a decrease in protein and lipid content in response to the restricted feeding regime. Ash content was not affected by the feeding regime. The present study shows that Nile tilapia fed diets subjected to a restricted feeding regime exhibited growth comparable to those fed the diet at 30% protein and 5% lipid levels under a normal feeding regime. This positive effect was more pronounced in diets at a high protein level or in a combination of high protein and lipid levels.     

Duckweed (Lemna polyrhiza) leaf meal as a source of feedstuff in formulated diets for rohu (Labeo rohita Ham.) fingerlings after fermentation with a fish intestinal bacterium

Eight isonitrogenous (35% crude protein approximately) and isocaloric (4.2 kcal g(-1) approximately) diets were formulated including raw and fermented duckweed (Lemna polyrhiza) leaf meal at 10%, 20%, 30% and 40% levels. A particular bacterial strain (Bacillus sp.) isolated from carp (Cyprinus carpio) intestine and having extracellular amylolytic, cellulolytic, proteolytic and lipolytic activities was used for leaf meal fermentation for 15 days at 37 degrees C. The fibre content of leaf meal reduced from 11.0% to 7.5% and the antinutritional factors, tannin and phytic acid, were reduced from 1.0% to 0.02% and 1.23% to 0.09%, respectively after fermentation. However, the available reducing sugars, free amino acids and fatty acids increased in the fermented leaf meal. The response of rohu, Labeo rohita, fingerlings fed the experimental diets for 80 days was compared with fish fed a fish meal based reference diet. On the basis of growth response, food conversion ratio and protein efficiency ratio, 30% fermented Lemna leaf meal incorporated in the diet resulted in the best performance of rohu fingerlings. In general, growth and feed utilization efficiencies of fish fed fermented leaf meal containing diets were superior to those fed diets containing raw leaf meal. The apparent protein digestibility (APD) decreased with increasing levels of leaf meal irrespective of treatment. The APD for raw leaf meal was lower at all levels of inclusion in comparison to those for the fermented meals. The highest carcass protein and lipid deposition was recorded in fish fed the diet containing 30% fermented leaf meal. The results showed that fermented Lemna leaf meal can be incorporated into carp diets up to 30% level compared to 10% level of raw meal.     

Changes in the digestibility of constituents of the diet in the rabbit]

Fiber digestibility of two diets (the first based on alfalfa dried, the second based on beet-pulp dried) with the same level of crude fiber and crude protein was measured on rabbits of 6, 7, 11, 13 and 17 weeks old. The age has no significative effect on digestibility (dry matter, organic matter, crude fiber) of the two experimental diets. The quantity of cellulose and hemicellulose digested was greater in rabbits on the pulp diet. Independantly of the diet hemicellulose is more digestible than cellulose. Expediency of use other analytical test than crude fiber in the nutritional requirements of rabbits is discussed.     

The effect of dietary crude fiber levels on rhesus monkeys during quarantine.

A study was conducted to determine the effect of dietary crude fiber level on intestinal disorders in the feral rheusus monkey (Macaca mulatta) during the first 60 days of the quarantine period. Three experimental baked diets containing 2.4%, 7.0%, and 9.8% crude fiber and a commercially extruded diet containing 2.2% crude fiber were fed during the study. The morbidity rate of intestinal disorders at the 7% crude fiber level was 1.4%, which was significantly less (p less than 0.05) than the 11.1%, 12.5%, and 20.8% morbidity for the monkeys fed the diets containing 2.4%, 9.8%, and 2.2% crude fiber, respectively. Monkeys fed the 7% crude fiber diet had a mean number of treatment days for intestinal disorders per monkey of 0.014, which was significantly lower (p less than 0.05) than the 0.9, 0.5, and 1.4 days for those fed the 2.4%, 9.8%, and 2.2% fiber diets, respectively.     

中华绒螯蟹幼蟹对亮氨酸和异亮氨酸的需要量

以初始体重为(0.900.02) g的中华绒螯蟹幼蟹为试验对象, 采用酪蛋白、明胶、进口鱼粉和晶体氨基酸为蛋白源, 配制成12组试验饲料, 研究中华绒螯蟹幼蟹对亮氨酸(Leu)和异亮氨酸(Ile)的需要量。饲料中Leu水平为0.87%、1.26%、1.64%、2.03%、2.39%和2.81% (分别记为Leu-1Leu-6组), Ile水平为0.69%、1.21%、1.70%、2.19%、2.70%和3.21% (分别记为Ile-1Ile-6组)。试验周期为60d。结果表明: (1)饲料中Leu含量为2.39%时, 幼蟹特定生长率和全蟹粗蛋白含量达到最大值, 而各组之间的成活率和全蟹水分、粗脂肪以及灰分无显著差异(P 0.05)。当饲料Leu含量大于2.39%时, 河蟹肌肉Leu含量、肌肉必需氨基酸总量和肌肉氨基酸总量均显著高于其他各试验组(P 0.05)。(2)饲料中Ile含量为2.19%时, 幼蟹特定生长率和全蟹粗蛋白含量达到最大值, 而各试验组之间的成活率和全蟹水分、粗脂肪以及灰分差异不显著(P 0.05)。河蟹肌肉Ile含量、必需氨基酸总量和氨基酸总量随饲料中Ile含量增加呈先升高后降低的趋势, 最大值均出现在Ile-5组(2.70% Ile), 但Ile-4组(2.19% Ile)与Ile-5组差异不显著(P 0.05)。根据特定生长率与饲料Leu或Ile水平的折线模型, 确定中华绒螯蟹幼蟹饲料亮氨酸和异亮氨酸的适宜需要量分别为饲料干物质的2.36%和2.25%, 即饲料蛋白的5.88%和5.72%。       

Periodic usage of low-protein methionine-fortified diets in broiler chickens under high ambient temperature conditions: effects on performance,slaughter traits,leukocyte profiles and antibody response

This study was performed to evaluate the effects of adding methionine supplements to low-protein diets and subsequent re-feeding with a normal diet on the productive performance, slaughter parameters, leukocyte profiles and antibody response in broiler chickens reared under heat stress conditions. During the whole experimental period (6–49 days), the birds were raised in battery cages located in high ambient temperature in an open-sided housing system. A total of 360 6-day-old male chickens were divided into six treatments in six replicates with ten chicks each. Six isoenergetic diets, with similar total sulfur amino acids levels, were formulated to provide 100 and 100 (control), 85 and 100 (85S), 70 and 100 (70S), 85 and 85 (85SG), 70 and 85 (70S85G), and 70 and 70 % (70SG) of National Research Council recommended levels for crude protein during the starter (6–21 day) and grower (22–42 day) periods, respectively. Subsequently, all groups received a diet containing the same nutrients during the finisher period (43–49 day). The results showed that, under heat stress conditions, average daily gain and feed conversion ratio and performance index from day 6 to 49, breast and thigh yields and antibody titer against Newcastle disease in the birds fed diets 85S, 70S and 85SG were similar to those of birds fed control diet, whereas feeding diets 70S85G and 70SG significantly decreased the values of above-mentioned parameters. Additionally, diets 85S, 70S and 85SG significantly decreased mortality rate and heterophil:lymphocyte ratio compared with the control diet. In conclusion, the results indicate that supplementation of methionine to diets 85S, 70S and 85SG, and then re-feeding with a conventional diet is an effective tool to maintain productive performance and to improve health indices and heat resistance in broilers under high ambient temperature conditions.