Metabolic and economic efficiency of broiler chicks as affected by dietary protein levels.

1. An experiment was designed to determine if decreasing excess amino acids in the diets of chicks would improve metabolic efficiency, as indicated by growth rate and food efficiency. 2. Semi-purified diets were fed with crude protein contents of 180 or 230 g/kg. The sources of protein were maize gluten meal, groundnut meal, sesame meal or soya-bean meal. Crystalline amino acids were supplemented to meet all amino acid requirements. 3. The dietary crude protein content had no statistically significant effect on weight gain or food consumption. The probability that the higher protein improved gain per food was 0.06. Protein source had a significant effect on all the responses measured. 4. Decreased concentrations of excess amino acids in chick diets had no favourable effects on weight gain or gain per food. Lower protein diets were more expensive per unit of gain.     

Isoleucine requirement of broiler chicks as affected by the concentrations of leucine and valine in practical diets.

1. Chicks were fed on an isoleucine-deficient diet, with 6 added concentrations of isoleucine to determine their isoleucine requirement and an additional 6 treatments were devised to determine their isoleucine requirement when dietary leucine and valine contents were increased. 2. The diet deficient in isoleucine contained 5.6 g/kg isoleucine with leucine and valine contents of 20.1 and 10.3 g/kg, respectively. Supplementation with leucine and valine increased these to 24.7 and 12.6 g/kg, respectively. 3. The isoleucine requirement was not affected by dietary leucine and valine contents in a diet with 13.4 MJ of ME per kg. Analysis of variance and Least Significant Difference of means indicated an isoleucine requirement of 7.2 g/kg. Non-linear regression of the same data indicated an isoleucine requirement of 8.44 g/kg, based on weight gain, or 8.19 g/kg based on food efficiency. 4. Reasons for the failure to find an imbalancing effect of branched chain amino acids in practical diets are discussed.     

The tryptophan requirement of broiler chicks.

The "available" tryptophan requirements of male and female broiler chicks were determined at 7-d intervals from 0 to 56 d, using a diet-dilution technique. Availability of tryptophan in the diets was estimated by growth assay with chicks. 2. The tryptophan requirements were 2.4 (males) and 2.2 g/kg of diet (female) from 0-7 d, and 1.7 g/kg (males and females) from 7-35 and 35-56 d. The absolute requirement of the chick for tryptophan increased with age and was significantly different for male and female birds. 3. A highly significantly predictive equation relating tryptophan requirement to mean body weight and gain was established.     

鲁禽优质肉鸡能量和蛋白质需要的研究

为了研究鲁禽优质肉鸡的最佳营养需要,选用1日龄健康雏鸡1080羽(公母各半),按营养水平随机分成9个处理组,每组公母鸡各3个重复共120羽。试验分为一期(0~5周龄)、二期(6~10周龄)和三期(11~13周),对不同营养水平下日增重与料肉比进行差异性分析,结果各期最佳营养水平为:一期公鸡能量12.14 MJ/kg,粗蛋白21%;母鸡能量11.72 MJ/kg,粗蛋白21%;二期公鸡能量12.55 MJ/kg,粗蛋白19%,母鸡能量11.72 MJ/kg,粗蛋白17.5%;三期公鸡能量13.40 MJ/kg,粗蛋白17%,母鸡能量12.55 MJ/kg,粗蛋白17%。     

Skeletal muscle protein turnover in broiler and layer chicks

Dietary infusion of L-[U-14C]tyrosine was used to estimate the fractional protein synthesis rates (FSR) in broiler and layer chickens. Six 2-wk-old birds of each strain were placed in individual metabolism cages and given a purified diet in agar-gel containing 2 microCi L-[U-14C]tyrosine for 6 h. The birds were sacrificed and the pectoralis major (PM) and two combined leg (LM) muscles (gastrocnemius and peroneous longus) were removed for analysis. Subgroups of chickens were sacrificed 3 d before and 3 d after infusion to observe changes in muscle composition to calculate fractional protein accretion rates (FAR). Fractional protein breakdown rates (FBR) were calculated by difference (FBR = FSR-FAR). Protein, ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) concentrations were determined to observe relationships between these cellular constituents and FSR. Fractional whole body growth rate and FSR in PM was greater (P less than .05) in broiler than layer birds. The FSR in LM of the layer was not different (P greater than .05) from that of broilers, and from the FSR of the PM in each bird-type. The calculated FBR in the layer PM was at least 17% higher than that of the other muscles. Ratios of FSR to FBR indicated that 16% of the protein synthesized in the layer PM was retained, compared with 45% in the broiler PM. The RNA activity of the layer PM was less (P less than .05) than that of the other muscles investigated. Deoxyribonucleic acid activity was lower (P less than .05) in the PM than LM of either bird-type.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nutritional evaluation of high-digestible sorghum for pigs and broiler chicks

Two experiments were conducted to evaluate the nutritional quality of 2 varieties of Purdue high-digestible sorghum (PHD1 and PHD2) and a normal sorghum, compared with corn, in diets of pigs and broiler chicks. In Exp. 1, 12 pigs (average BW, 55 kg) fitted with ileal T-cannula were fed 4 diets containing 946 g of corn or sorghum (PHD1, PHD2, and normal) per kg in a 2-period crossover design (i.e., each pig received 2 diets over a 2-wk period with 6 pigs per dietary treatment) to determine apparent ileal or total tract digestibility of nutrients and energy. There was no difference in the ileal or total tract digestibility of DM, energy, P, Ca, or N among dietary treatments. In Exp. 2, a total of 192 broiler chicks were grouped by weight into 8 blocks of 4 cages each with 6 chicks per cage, and cages were assigned randomly to 1 of the 4 dietary treatments within each block. Chicks were fed corn-soybean meal (SBM) or sorghum-SBM diets for 21 d to determine apparent total tract retention and then switched to diets containing 935 g of the corresponding corn or 1 of the 3 sorghum varieties per kg for 7 d to determine apparent ileal digestibility and total tract retention. Apparent ileal digestibilities of DM and P, as well as energy, were not different in chicks fed diets containing 935 g of corn or 1 of the 3 sorghum varieties per kg. However, apparent total tract retention of DM, energy, and N in chicks fed corn was greater (P < 0.05) than those fed 1 of the 3 sorghum varieties. Although the apparent ME content of corn was greater than PHD1 and normal sorghum (P < 0.01), it was not different from PHD2 sorghum. There was no difference in apparent total tract retention of DM between chicks fed the corn-SBM and PHD-SBM diets, but it was greater (P < 0.05) in chicks fed the corn-SBM diet than those fed the normal sorghum-SBM diet. Apparent total tract retention of N in chicks fed the PHD1-SBM diet was lower (P < 0.05) than in those fed the corn-SBM diet but greater (P < 0.05) than in chicks fed the normal sorghum-SBM meal diet. No difference in the apparent ME content between the corn-SBM and PHD2-SBM diets was observed, but it was greater (P < 0.05) for the corn-SBM diet than the PHD1- or normal sorghum-SBM diet. Weight gain, feed intake, and feed efficiency were not different in chicks fed the corn-SBM or sorghum-SBM diets. Sorghum could serve as a substitute for corn in cereal grain-SBM diets for pigs and broiler chicks.     

Determination of endogenous manganese excretion in broiler chicks by an isotope-dilution method

A tracer study with broiler chicks was conducted to determine endogenous Mn excretion in response to graded levels of dietary Mn supply by the isotope-dilution method. Starting with 46 day-old chicks, low-Mn diets were fed for 12 days before 8 chicks were slaughtered for assessing the initial Mn status and 38 chicks each were given an intramuscular injection of 555 kBq 54Mn. Four groups of six birds each were fed, one bird per cage, diets containing 2.8, 9.1, 25.8, and 59.7 ppm Mn for 16 days before slaughter and carcass analyses. Two groups of 7 birds were fed the diets with 9.1 and 25.8 ppm Mn for 8 days. Mn supply significantly affected 54Mn excretion and its distribution among various body organs, especially the liver. The specific activity of Mn in excreta and in whole-body declined exponentially with time and differed between groups. Endogenous Mn in excreta was estimated on the basis that the specific activity of excreta Mn from day 9 to 12 and day 13 to 16 was reflected, on the average, by that of liver Mn on day 10 and 14, respectively. It averaged in the order of increasing Mn supply 12.5 vs. 12.0; 7.7 vs. 8.5; 3.9 vs 4.3, and 2.0 vs 2.3% of total excreta Mn. Total Mn excretion from day 9 to 16 averaged 88.9, 95.0, 97.9, and 98.9% of Mn intake.     

Mango seed kernels as an energy source for chicks1

1. Chemical analysis of a sample of ground mango seed kernels (MSK) revealed the following percentage composition: dry matter, 91.55; ash, 1.97; protein, 6.74; ether extract, 12.53; fibre, 1.30; nitrogen‐free extract, 77.46.

2. The ME content of MSK was 1.82 kcal/g.

3. The percentage retention of the crude fat content of MSK was only 3.38%.

4. Substituting MSK for corn at 10 or 20% led to reduced growth rate and poorer food consumption and a reduced efficiency of food utilisation in the period 0 to 4 weeks.     

Suppression of cell-mediated immunity by purified aflatoxin B1 in broiler chicks

The effect of purified aflatoxin B1 on cell-mediated immunity (CMI) in broiler chicks was assessed using doses of 0.3 and 1 mg/kg feed from hatching to 6 weeks of age. Total lymphocyte and T lymphocyte counts and the 2,4-dinitrofluorobenzene skin sensitivity test, graft-versus-host reaction and nitroblue tetrazolium salt reduction tests were used to evaluate CMI. Both doses of aflatoxin B1, including the apparently nontoxic dose of 0.3 mg/kg feed, caused a significant (P less than 0.05) decline in CMI. The functional activity of splenic macrophages was decreased significantly (P less than 0.05) by both doses of the toxin.     

Regulation of muscular glutamate metabolism by high‐protein diet in broiler chicks

The major taste active component, glutamate (Glu), improves the taste of meat. In this study, we investigated the effect of a short‐term high‐protein (HCP) diet on the intramuscular free Glu content to improve the taste of meat. Furthermore, we elucidated how the muscle free Glu content was controlled by the HCP diet. Chicks (14 days old) were fed the control diet or HCP diet for 10 days. Plasma and muscle free amino acid concentrations, and activity and messenger RNA (mRNA) expression of muscle enzymes related to Glu metabolism were determined. Muscle free Glu content was increased (P < 0.01) by 51%. Activity and mRNA expression of glutaminase (GA), which is one of the major Glu‐related enzymes, were significantly decreased (P < 0.05) in the HCP group because of feedback inhibition. The mRNA expression of lysine α‐ketoglutarate reductase (LKR), which is the enzyme involved in lysine (Lys) degradation and Glu production, was significantly increased (P < 0.001) in the HCP group. These results suggest that short‐term dietary HCP feeding is an effective treatment for improving the taste of meat. Furthermore, our results suggest that the free Glu content in muscle is regulated by GA and LKR.     

The use of methane-utilising bacteria as a source of protein for young chicks

Two strains of continuously‐grown, methane‐utilising bacteria were found to contain 8.96 and 9.95% N and a favourable pattern of essential and non‐essential amino acids, the concentrations of which were generally higher than those previously observed in batch grown organisms (D'Mello, 1972).

One of these strains has been evaluated as a protein source for young chicks. Four diets were employed : the first was a control maize‐soybean diet supplemented with methionine; the second was similar to the control diet except that 10% bacterial protein was included largely at the expense of soybean; the third, a low‐protein diet, was identical to the second in all respects except that the bacterial protein source was substituted by an equivalent weight of ground maize ; the fourth consisted mainly of maize and dried whole egg served as an additional control diet.

There were no significant differences in growth, efficiency of food conversion or nitrogen retention between the control group and the group receiving the bacterial protein. Furthermore, chicks in these two groups performed significantly better than either those fed on the low‐protein diet or those fed on the whole egg diet.

Amino acid and uric acid concentrations in plasma were similar in the control and bacterial protein groups although levels tended to be lower in chicks consuming the low‐protein diet. Activities of glutamic‐oxalacetic and glutamic‐pyruvic transaminases in plasma were similar in all dietary groups.

These results suggest that the strain of methane‐oxidising bacteria used in the present study is potentially a useful source of protein for non‐ruminant animals.     

Effect of dietary zinc source and method of oral administration on performance and tissue trace mineral concentration of broiler chicks.

Two experiments were conducted with chicks to examine the effect of high dietary levels of soluble sources of Zn on tissue Zn, Cu, and Fe concentrations as influenced by two methods of oral Zn administration from 14 to 21 d of age. Treatments included the basal diet (62 ppm Zn), basal diet supplemented with 1,000 ppm Zn from Zn sulfate, acetate, or chloride fed continuously, or basal diet plus crop intubation with a single oral dose of water (control) or 1,000 ppm Zn dietary equivalent from the sources based on feed intake from the previous day. In Exp. 2, crop-intubated doses were administered daily from 14 to 21 d of age. In Exp. 1, chicks given Zn by gavage decreased (P < .0001) feed intake at 24 h after oral dose compared with chicks fed either the control or high-Zn diets. After the gavage dosing stopped, feed intake was similar among treatments. Bone Zn was increased (P < .0001) by Zn source and was greater at 24 than at 168 h after dosing by gavage. In chicks given a single gavage dose of Zn, liver and kidney Zn measured at 24 h after oral dosing was greater (P < .0001) than at 168 h. In birds given a single oral dose of Zn, time x Zn source interactions were observed in pancreas (P < .0001), mucosal cells (P < .01), and remaining intestinal tract segments (P < .001). In Exp. 2, greater bone, pancreas, kidney (P < .0001), and liver (P < .001) Zn accumulations were observed in chicks given daily gavage doses of Zn compared with those fed Zn in diets. Zinc from the four sources was absorbed and stored in tissues to a similar extent.     

Effect of some antibiotics as growth promoters on performance of broiler chicks fed different protein levels

This work was carried out to study the effect of different sources of dietary antibiotics (Zinc bacitracin, Flavomycin, Virginiamycin) in rations with optimal protein levels (starter phase: 23.5%, finisher phase: 20.0%) and low protein levels (starter phase: 19.6%, finisher phase: 17.0%) on broiler performance with 8 groups of 75 broiler each. The supplement of diets, containing the optimal and low protein level, with antibiotics increased the body weight after 7 weeks of age and improved the feed conversion as compared with control groups. Virginiamycin was superior in increasing body weights after 7 weeks of age and in improving the feed conversion with rations containing low protein level when compared with zinc bacitracin and Flavomycin. When broiler rations, low in the protein content, were supplemented with antibiotics, they could not substitute the difference in optimal protein level. Antibiotics supplementation increased the value of improvement in production efficiency and this was more pronounced with Virginiamycin.     

Effect of lincomycin as a growth promoter for broiler chicks

1. The effects of adding lincomycin to either the food (2.2 mg/kg) or drinking water (equivalent or 0.5 equivalent amount) of male broiler chicks were examined. 2. There were four treatments: control (no lincomycin), diet containing 2.2 mg lincomycin/kg, control diet plus drinking water containing lincomycin at concentrations calculated to provide an intake equivalent to treatment 2, and treatment 14 with lincomycin concentration reduced by half. 3. There was no significant effect of any treatment upon mortality, efficiency of food utilisation at 42 d of age, final body weights or monetary indices. 4. Analyses of breast, thigh and liver tissues, using a method with a sensitivity of 1.0 mg/kg, failed to reveal any evidence of lincomycin residues. 5. It is concluded that the use of lincomycin at 2.2 mg/kg may not be effective in improving either the biological or economic performance of the broiler chicken.     

肉仔鸡日粮中锌营养状况评价指标的研究

选用384只1日龄商品代从内公鸡随机分成8个处理组,分别饲喂不添加锌的玉米-豆粕型基础日粮(对照组,舍锌28.37 nag/kg)和在对照组基础日粮中以无机硫酸锌形式添加20、40、60、80、100、120 mg/ks和140 mg/kg锌的试验日粮.试验期7 d.研究日粮中添加不同水平无机锌对内仔鸡生长性能、组织锌含量、含锌酶活性以及含锌蛋白及其基因表达的影响,以考察这些指标对评价肉仔鸡锌营养状况的意义.结果表明:肉仔鸡生长性能未受到添加锌水平的显著影响(P>0.24),而胫骨锌、胰脏锌含量以及胰脏金属硫蛋白(MT)含量及其基因表达受锌水平影响极显著(P<0.01),胫骨锌和胰脏锌含量随锌水平增加呈渐近线趋势变化.胰脏MT含量及其基因表达则呈线性上升趋势.这些指标均可以作为反映肉仔鸡锌营养状况的指标.从相关系数比较来看.胫骨锌和胰脏锌与饲粮锌的相关性比胰脏MT含量及其基因表达更密切.胰脏MT含量及其基因表达随锌水平增加线性上升.可用作评价不同锌源生物学利用率的有效指标.     

植酸酶对3～6周龄的肉仔鸡磷需求的影响

进行两个相同设计方案的试验。选用3周龄的有充足磷饲料喂养的人工笼养雄仔鸡，在3－6周这一阶段分别喂给0．10％至0．45％（递增量为每次0．05％）的非植酸磷（non-phytate phophorous; 即nPP)。在日粮中添加800单位／kg的植酸酶。测定包括体增重、饲料转化率、发病率、胫骨灰分和粪磷情况。非线性回归方程被用来评价要得到最佳体增重、饲料转化率、发病率、胫骨灰分和粪磷时非植酸磷的需求量。在无植酸酶的情况下，得胫骨灰分率、增重率和饲料转化率的非植酸磷量分别是0．33％、0．186％和0．163％，这一数据非常符合现今NRC（1994）的推荐量。而添加800单位／kg的植酸酶后，得到最佳胫骨灰分率、增重率和饲料转化率的非植酸磷含量分别是0．24％、0．151％和0．109％。粪磷在低磷状态下显著减少。