Utilisation of different phosphorus sources in relation to their fluorine content for broilers and layers

1. The relative utilisation of different phosphorus sources in relation to their fluorine (F) content was studied in commercial broilers (5 to 40 d) and White Leghorn layers (252 to 364 d). The phosphorus (P) sources tested were bonemeal (BM), low fluorine (LFRP) and high fluorine (HFRP) rock phosphates and a commercial mineral mixture (CMM). The P sources were incorporated in broiler and layer diets by replacing dicalcium phosphate (DCP) on a P basis. 2. The F contents of diets based on BM, LFRP, CMM and HFRP were 53, 365, 622 and 1383 mg/kg in the broiler experiment and 34, 242, 437 and 967 mg/kg in the layer experiment, respectively. F was not detected in DCP based diets. 3. In broilers, body weight gain, food intake, gain: food, P retention and serum inorganic P content on P sources (BM and LFRP) containing F up to 365 mg/kg diet were similar to those on DCP. Body weight gain, food intake, serum calcium and inorganic P contents and retention of P were depressed in groups fed on CMM and HFRP, which may have been due to the toxic effects of F (622 and 1383 mg/kg) present in diets based on these P sources. 4. Bone ash and its P content were not affected by feeding diets containing F up to 1383 mg/kg from various P sources. The amount of F deposited in tibia increased significantly with increases in dietary F concentration. 5. In layers, egg production and food intake were not affected by F up to 437 mg/kg in diets containing BM, LFRP or CMM as the sole source of supplemental P. Egg production and food intake were depressed significantly in layers given the diet containing 967 mg F/kg from HFRP. 6. Egg mass: food, egg weight, shell quality (shell thickness and shell weight) and serum calcium and inorganic P levels were not affected by F up to 967 mg/kg in diets containing different P sources. 7. It may be concluded that the performance of broilers and layers was not affected by feeding various P supplements with dietary levels of F up to 365 and 437 mg/kg, respectively. The reduced performance in broilers and layers observed with some of the P sources may have been due to poor availability of P and/or toxic effects of F (622 and 967 mg/kg, respectively).     

Precaecal phosphorus digestibility of inorganic phosphate sources in male broilers

1. The aim of this study, comprising two experiments, was (1) to determine in Experiment 1 the relationship of incremental dietary P (phosphorus) content on precaecal digestible P in male broilers and (2) to determine in Experiment 2 the precaecal P digestibility of various inorganic P sources at marginal levels of P supply.

2. In Experiment 1, a total of 260 male Ross 308 broilers were divided into groups of 10 birds per pen resulting in 8 replicates for treatment 1 and 6 replicates for treatments 2–4. Experimental diets were formulated to contain 4 incremental concentrations of digestible P by means of increasing concentrations of monocalcium phosphate (MCP). In the second experiment, 480-d-old male Ross 308 broilers were divided in groups of 12 birds per pen resulting in 16 replicates for the basal diet and 6 replicates for each test diet. A total of 4 inorganic P sources, MCP, monodicalcium phosphate (MDCP), dicalcium phosphate (DCP) and defluorinated phosphate (DFP) were added to the basal diet to determine the precaecal P digestibility. Three of the 4 inorganic P sources (MCP, MDCP and DCP) represented a mix of batches from different producers. At the end of both experiments, the chyme of the posterior part of the small intestine was collected. Digestibility of P and Ca was determined using titanium dioxide as indigestible marker.

3. In Experiment 1, a reduction in precaecal digestibility of P was observed above an estimated precaecal digestible dietary P concentration of 4.8 g/kg.

4. The precaecal P digestibility of the tested inorganic P sources in Experiment 2 was 78.3% for MCP, 59.0% for DCP, 70.7% for MDCP and 31.5% for DFP.

     

Relative bioavailability of phosphorus in inorganic phosphorus sources fed to growing pigs

The relative bioavailability of P in 5 sources of inorganic P was determined using growing pigs. The 5 sources of inorganic P were dicalcium phosphate (DCP), monocalcium phosphate (MCP) containing 50% MCP (MCP50), MCP containing 70% MCP (MCP70), MCP containing 100% MCP (MCP100), and monosodium phosphate (MSP). A total of 11 diets were formulated. The basal diet was formulated to contain 0.10% P, and 10 additional diets were formulated by adding 0.07 or 0.14% P from each of the 5 P sources to the basal diet. Growing pigs (n = 44; initial BW: 16.8 ± 4.3 kg) were individually housed and randomly allotted to the 11 experimental diets. Feed was provided on an ad libitum basis throughout the 28-d experimental period. At the conclusion of the experiment, all pigs were killed, and 4 bones (i.e., the third and fourth metacarpals on both front feet) were harvested. Bone-breaking strength, bone ash, and Ca and P concentrations were determined. The concentration of bone ash increased (P < 0.05) as MCP50, MCP70, MCP100, or MSP were added to the basal diet, and the concentration of bone P also increased (P < 0.05) as MCP70, MCP100, or MSP were added to the basal diet. The relative bioavailability of P in each of the feed phosphates was determined using slope ratio methodologies based on breaking strength, and expressed relative to MSP. The slope of the regression line for diets containing MSP or MCP100 was steeper (P < 0.05) than the slope for pigs fed the diet containing DCP, but not different (P > 0.05) from that of pigs fed diets supplemented with MCP50 or MCP70. In conclusion, P in MSP and MCP100 is more bioavailable than P in DCP, but there were no differences within MCP sources.     

Effects of different phosphorus sources in the diet on bone composition and stability (breaking strength) in broilers

In two fattening trials (in each 100 broilers kept in four groups with 25 animals) as well as in a balance trial (four groups with four broilers in a group) the effects of inorganic phosphorus sources [monocalcium phosphate (MCP), dicalcium phosphate (dihydrate; DCP) and defluorinated phosphate (DFP)] in broiler diets were examined. The four diets contained up to 9 g calcium and 6 g phosphorus per kg and comparable energy and nutrient contents. Controls were fed a commercial diet with Ca-Na-phosphate as inorganic phosphorus source supplemented by phytase. In both fattening trials body weight gain, feed consumption and feed conversion were proved as well as the calcium and phosphorus levels in serum, the breaking strength of tibia or humerus and the femur mineralization (ash content in the fat free dry matter). Furthermore, in the balance trial the retention of calcium and phosphorus was determined by calculation (intake minus excretion) as well as by analysis of body composition. On a high performance level (that was only slightly influenced by the different treatments), the addition of DFP resulted in significantly reduced phosphorus availability (estimated by analysis of the whole carcass: control/MCP/DCP/DFP: 48.6/46.0/45.7/35.5%). The significantly reduced phosphorus level in serum (1.77 +/- 0.20/1.77 +/- 0.24/1.73 +/- 0.28 1.34 +/- 0.33 mmol/l) indicates the lower phosphorus retention in broilers given DFP. Furthermore, the crude ash content (582 +/- 17.6/580 +/- 18.6/563 +/- 15.2/547 +/- 29.7 g/kg fat free DM) and the breaking strength of bones (in right tibia in trial 2: 232 +/- 82.4/227 +/- 51.5/232 +/- 41.7/196 +/- 655 N) were lowest when given DFP. For diagnostic purposes it is of special interest that the phosphorus levels in the serum reflected markedly the different concentrations of available phosphorus in the diet.     

Efficiency of effect of high ambient temperatures on food utilisation in male broilers

The effect of ambient temperatures above 28 degrees C on the efficiency of food utilisation were studied in 7 consecutive flocks of male broilers, grown in a cross-ventilated controlled environment poultry house. The best correlation between the food:gain ratio and temperature was obtained when the latter was expressed as degrees-h (Th), that is, the aggregate of the differences between the ambient temperature and 28 degrees C, measured hourly. The equation: Food:gain ratio = 2072 + 0.125 X Th, demonstrates clearly the negative effect of high temperatures on food:gain ratio in broilers. It might be helpful for the broiler industry when evaluating the need for and planning of cooling devices for poultry houses.     

Effect of food enzymes on utilisation of lupin carbohydrates by broilers

1. The effects of 3 commercial enzyme products on the nutritive value of 2 lupin species were investigated with the emphasis on changes in composition of non-starch polysaccharides (NSPs) along the digestive tract. Enzyme A contained primarily cellulase, beta-glucanase and xylanase activities, enzyme B primarily hemicellulase, pentosanase and xylanase activities, and enzyme C primarily hemicellulase, pectinase and beta-glucanase activities. 2. The enzymes were added to semi-purified diets based on sorghum and casein containing 35% whole seed lupins (Lupinus angustifolius cv Gungurru or Lupinus albus cv Kiev mutant). Control diets contained no lupins. 3. Food conversion ratio (FCR), excreta moisture content and apparent metabolisable energy (AME) were affected by lupin species but not by enzyme supplementation. 4. In diets with L. angustifolius, enzyme C significantly increased digesta viscosity and increased the concentration of soluble NSPs in all sections of the intestine. 5. Digestibility of protein and NSPs in the ileum and microbial fermentation in the ileum and caeca were not affected by adding enzymes to diets containing L. angustifolius. 6. Enzyme addition to diets with L. albus did not affect digesta viscosity nor concentration of soluble NSPs but caused a significantly (P<0.05) reduced concentration of insoluble NSP in the ileum. 7. Enzyme addition to L. albus significantly (P<0.05) increased NSP digestibility in the ileum but had no effects on protein digestibility and fermentation in the ileum and caeca.     

植酸酶对提高肉仔鸡日粮中钙、磷利用率的研究

将试验肉仔鸡随机分成4组,每组设3个重复,每个重复20只。Ⅰ组为不添加植酸酶的基础日粮对照组;Ⅱ组为每千克日粮添加500U植酸酶替代基础日粮中0.09%的无机磷试验组;Ⅲ组为每千克日粮添加500U植酸酶替代基础日粮中0.11%的无机磷试验组;Ⅳ组为每千克日粮添加500U植酸酶替代基础日粮中0.13%的无机磷试验组。试验按0～3周龄和4～6周龄两个阶段进行。试验结果表明:在肉仔鸡玉米-豆粕型日粮中添加0.01%的植酸酶(活性为5000U/g)替代日粮中0.12%的钙和0.11%的无机磷可显著提高肉仔鸡的生长性能,并能取得最佳的经济效益,为最适替代比例。     

肉鸡和蛋鸡日粮中添加植酸酶的研究进展

近几年来,随着生物技术的发展,使大规模商业化生产植酸酶成为可能。由于反刍动物瘤胃中的微生物可以产生大量的植酸酶,因而可以很好地利用饲料中的植酸磷（Reid等,1947）,而猪和家禽等单胃动物由于肠道中植酸酶活性微弱,并且易被日粮中的某些成分（如钙）所抑制,因而不能有效利用饲料中的植酸磷。需要额外添加无机磷。因此,在猪和家禽的饲料中应用植酸酶以提高植酸磷的利用率日益引起重视,研究也不断深入。在美国乔治亚州亚特兰大国际家禽科学论坛上,植酸酶在肉鸡和蛋鸡日粮中添加的重要意义成为与会者探讨的中心话题。研究覆盖了添加的植酸酶与饲料中已经存在的植酸酶是如何发生反应的,在单一饲料和混合饲料中是如何反应的,不同商业植酸酶的作用如何等。现将主要内容编译介绍如下。     

肉仔鸡对不同锰源生物学效价的研究

试验采用1日龄AVAINS肉仔鸡200只研究不同锰源的生物学效价。试验采用3×3因子试验设计,3种锰源分别为硫酸锰、乙酸锰和酵母锰,3个锰水平分别为60、120、180mg/kg,试验共10个处理,每个处理4个重复。在本试验条件下,试验组各组锰源日粮锰源对肉仔鸡生产性能、心肌、肝脏、肾脏、胫骨锰含量以及心肌MnSOD活力影响不显著。日粮中添加酵母锰有改善肉仔鸡生产性能的趋势,但随日粮锰水平的增加,肉仔鸡生产性能没有表现出规律性变化,心肌、肝脏、肾脏及胫骨锰含量极显著增加,而血红蛋白含量显著降低。综合考虑本试验获得的回归方程的显著性和日粮锰水平对各测定指标的影响,本次试验所测指标均可以作为适合本试验条件的评价不同锰源生物学利用率指标。     

肉仔鸡对不同铁源生物学利用率的研究

试验采用1日龄AVAIN肉仔鸡200只研究不同铁源的生物学效价。采用3×3因子试验设计,3种铁源分别为硫酸亚铁、柠檬酸铁和酵母铁,试验日粮在玉米-豆粕型基础日粮(对照组)的基础上分别添加40、80、160mg/kg铁构成,试验共10个处理,每个处理4个重复。在本试验条件下,试验各组铁源对肉仔鸡生产性能、脾脏以及血红蛋白铁含量、红细胞计数、血细胞压积、血清总铁结合力影响不显著;对肝脏、肾脏铁浓度影响显著或极显著;随日粮铁水平的增加,肉仔鸡生产性能没有表现出规律性变化,脾脏铁、肝脏铁、胰脏铁浓度以及血红蛋白含量极显著增加,肾脏、肝脏铁浓度以及血红蛋白、红细胞计数显著增加,而血清总铁结合力极显著降低。利用斜率比法,不同判断指标得到的柠檬酸铁和酵母铁的相对生物学效价不同;综合所获得的回归方程的显著性和日粮铁水平对各测定指标的影响,本次试验所测指标均可作为适合本试验条件的评价不同铁源生物学利用率指标。     

法氏囊弱毒疫苗GUMBORO PLUX对蛋鸡肉鸡的免疫效果试验报告

传染性法氏囊病(IBD)是鸡的一种由双股RNA病毒引起的急性传染病,此病主要损害鸡体淋巴器官造成免疫抑制,从而导致多种疫苗免疫无效及对其它疾病如新城疫、球虫病等的易感性增高而引起经济损失。IBD于1957年首次发生于美国Delware州南部Gumboro地区,我国于1979年相继在广州、北京、上海发现本病,随着不同毒株疫苗的使用,该病已得到,基本控制。但是近年来,我国一些地方,特别是在法氏囊母源抗体高低不齐的蛋鸡和肉鸡饲养区,屡有传染性法氏囊病(IBDV)的发生和流行。这些自然发病时死亡率达10～30%的鸡群,即使使用中等以上毒力的疫苗或含有…     

Effects of microbial phytase on growth and mineral utilisation in broilers fed on maize soyabean-based diets.

1. A 3-week feeding trial with 96 sexed d-old broiler chickens was conducted to examine the effects of microbial phytase supplementation (Natuphos 5000) at 2 dietary energy concentrations on their performance, and the utilisation of nitrogen (N), phosphorus (P), calcium (Ca) and zinc (Zn) and on tibiae ash, Ca, P and Zn concentrations. Four replicate pens (6 birds per pen) of a completely randomised design were used in a 2x2 factorial arrangement of treatments with 2 contents of metabolisable energy (11.72 and 12.55 MJ ME/kg) and 2 additions of phytase (0 and 500 U of microbial phytase/kg). 2. Phytase supplementation significantly improved the utilisation of N, P, Ca and Zn (as a percentage of intake) and increased the concentration of Ca and Zn in the tibiae (P<0.05) because of higher intakes of dry matter, N, P, Ca and Zn. Phytase also significantly reduced the amount of P in the excreta (P<0.05). 3. The AME content of the diet influenced significantly (P<0.05) the excretion of N, P, Ca and Zn and the concentration of P and Ca in tibiae with the birds fed on the high AME diet excreting more minerals and having a smaller percentage of these minerals in their tibiae. However, there were strong interactions between phytase addition and AME in tibia ash and P, with the phytase supplementation producing a higher ash content at the higher AME a and a lower P content at the lower AME.     

Efficiency of inorganic and organic iron sources under iron depleted conditions in broilers

1. A total of 240?d-old male Ross chicks (average BW 37·15?±?0·49?g) were fed on an iron (Fe)-deficient semi-synthetic diet (45?mg Fe/kg) from d 1-7 post hatching.

2. At d 7, all 240 chicks (average BW 140·15?±?1·4?g) with depleted Fe-stores were randomly assigned to three treatments on the basis of BW to study the efficiency of dietary inorganic and organic iron (Fe) utilisation. Each treatment had 4 replicates with 20 birds in each.

3. Dietary treatments were: maize-soyabean meal-based basal diet, containing 103 to 106?mg Fe/kg (control); and basal diets supplemented with an additional 80?mg/kg Fe either from an inorganic (FeSO₄?·?H₂O, 28% Fe) or organic (ferrous methionine chelate, 10% Fe) source. The starter and finisher diets were fed from d 7 to 21 and d 21 to 35, respectively.

4. Improved body weight gain and FCR during finisher phase and overall study period; and greater DM and CP retention, and excreta Fe excretion, at d 20 to 21 and d 34 to 35; were observed in birds fed on Fe supplemented diets when compared with birds fed on control diet. At d 35, the RBC, Hb, haematocrit, and Fe concentration in plasma, tibia and liver were higher in birds fed on Fe supplemented diets than birds fed on the control diet.

5. Supplementation of Fe in organic form resulted in greater Fe concentration in the tibia and liver and less Fe excretion at d 34 to 35, when compared with birds receiving inorganic Fe.

6. These results indicate the necessity to supplement Fe in the commercial diets of broilers; however, organic and inorganic sources of Fe supplementation at 80?mg/kg were equally effective in improving performance, nutrient retention and haematological indices. In addition, Fe supplementation through an organic source seems to be more efficient in depositing Fe in the haemopoietic organs (liver and tibia) of birds under Fe depleted conditions.     

不同锰源不同添加剂量对肉仔鸡生产性能的影响

试验选用1日龄AA肉仔鸡180只,随机分为3组。进行饲养试验,以玉米-豆粕型日粮为基础日粮,Ⅰ组为对照组,添加硫酸锰(MnSO4·H2O)120mg/kg;Ⅱ组为试验组,添加蛋氨酸螯合锰(Met-Mn)60mg/kg;Ⅲ组也为试验组,分别添加蛋氨酸螯合锰(Met-Mn)30mg/kg和硫酸锰(MnSO4·H2O)60mg/kg。研究不同锰源及不同添加方式对肉仔鸡生产性能的影响。结果表明,3种方式添加锰对肉仔鸡生产性能无显著影响(P>0.05),但Ⅲ组的饲料成本有所降低。因此,在肉仔鸡日粮中以第3种方式(30mg/kgMet-Mn+60mg/kgMnSO·4H2O)添加锰效果最佳。     

Energy utilisation of carbohydrate, fat and protein sources in newly hatched broiler chicks

1. TME, TMEn and metabolisability (TME/gross energy) of energy-yielding foodstuffs were determined in 1, 3 and 10 d old broiler chicks, using the assay method developed by Murakami et al. (1994), in order to characterise energy utilisation during the 10 d after hatching. 2. TME, TMEn and metabolisability of dextrin and starch were low in chicks aged 1 d, and increased with age up to 10 d. Energy values of glucose and maltose at days 1 and 3 could not be determined because of the sudden death of birds soon after the feeding. TMEn and metabolisability of cereal sources were lower in d-old chicks than in those aged 3 and 10 d. At all ages, maize was better utilised than wheat and sorghum. 3. In the fat sources (coconut oil, beef tallow and safflower oil) no age dependency was observed in TME, TMEn and metabolisability. 4. Bioavailability of soyabean meal and fish meal was lower at 1 d than at 3 d and 10 d. Energy utilisation from casein was the highest among the protein sources tested and it was not age dependent. 5. It is concluded that energy utilisation of carbohydrate and protein sources during 10 d post-hatch tended to increase with age. Among the energy yielding foodstuffs fat sources seem to be better utilised, with no age dependency.     

不同产地DDGS在黄羽肉鸡上的生物学效价比较研究

试验旨在比较不同产地DDGS在黄羽肉鸡上的生物学效价。试验选用9个不同产地的DDGS,并对其总能(GE)、粗蛋白(CP)和氨基酸(AA)进行测定。随后选用25日龄的黄羽肉鸡(优麻)200只,随机分为10个处理,每个处理10个重复,每个重复2只鸡。采用套算法和全收粪法测定9个产地DDGS的表观代谢能(AME)、CP和AA代谢率。结果表明,试验用DDGS在黄羽肉鸡上的平均AME为12.43 MJ/kg,RSD为11.14%,以协A最高,莱芜最低(P0.05);试验用DDGS在黄羽肉鸡上的平均CP代谢率为77.98%,RSD为8.22%,各产地差异不显著(P0.05);试验用DDGS在黄羽肉鸡上的AA代谢率(AAA)RSD大于10%的AA有6种,且AAA占前三位的个数排序为:海美A莱芜安A=柠檬协A美B=安B协B。由此可见,不同产地DDGS在黄羽肉鸡上的生物学效价不同,其中以协A的AME最高,海的AAA最好。     

Responses of broilers to dietary zinc concentrations and sources in relation to environmental implications

1. Since high concentrations of zinc are associated with reduced crop yields, environmental concerns are emerging regarding zinc accumulation in areas where poultry production is prevalent. This study investigates growth performance and zinc utilisation during the life cycle of broilers when diets were supplemented with various concentrations of zinc from two different sources. 2. A total of 740 Cobb 500 1-d-old male broiler chicks was randomly distributed into 88 battery cages. Excreta were collected over a 48-h period on d 10, 17, 24, 31, 38, and 45 to measure zinc excretion on a dry matter basis. 3. During the 45-d experimental period, broilers were given a maize-soybean meal basal diet (30 mg/kg zinc) supplemented with 0, 20, 40, and 80 mg/kg of zinc from zinc sulphate, Availa Zn amino acid complex, or an equal combination of zinc sulphate and Availa Zn amino acid complex. 4. Progressive additions of zinc to the basal diet significantly increased body weight gain of broilers, but did not affect feed conversion or mortality. Optimum body weight gain was achieved at 80 mg/kg supplemental zinc, which exceeds the NRC recommendations of 40 mg/kg. 5. During each excreta collection period, increased supplemental zinc concentrations significantly increased zinc excretion. However, the zinc source did not influence zinc utilisation. 6. As compared with zinc sulphate supplementation, the cumulative zinc excretion data indicate that adding zinc to the basal diet in the form of Availa Zn amino acid complex decreased zinc excretion.     

团标“蛋鸡、肉鸡配合饲料”编制依据

为了进一步推动"环境友好,资源节约型"畜牧业的实施,我国于2018年10月～11月初发布并实施了"仔猪、生长育肥猪配合饲料"与"蛋鸡、肉鸡配合饲料"团体标准。为了更好的宣贯"蛋鸡、肉鸡配合饲料"团体标准的实施,本文就其编制内容进行说明。本标准是在GB/T 5916—2008产蛋后备鸡、产蛋鸡、肉用仔鸡配合饲料基础上,参考当前国际上主要蛋鸡、肉鸡品种营养推荐标准,及国内黄羽肉鸡标准,并结合当前饲料营养向精准营养方向发展的趋势,对国家标准GB/T 5916—2008中饲料划分阶段和营养参数进行限定。本标准旨在推动即实现家禽遗传潜力得到充分发挥,又尽量达到节能减排,符合国家的大政方针。     

Postvaccination viremia in breeding flocks of layers and broilers after vaccination against Marek's disease of fowl

The immunity state after vaccination against Marek's disease (MD) was studied in three multiplier flocks of laying fowl (MFL), five multiplier flocks of broiler fowl (MFB), and one commercial layer flock (CLF). The occurrence and average titres of post-vaccination viraemia in the selected sets of chickens from these flocks, examined at the age of three or twenty weeks, were used as the immunity criterion. The development of post-vaccination viraemia, following the administration of the MARVAK vaccine at the doses of 100 and 1000 PFU per bird in the HX-SL and Shaver layer hybrids, was examined under laboratory conditions at the same time. In the group of birds examined in the third week of age and coming from the MFL vaccinated with the recommended MARVAK vaccine (dose (100 PFU per bird), 64.3% of the chicks were viraemic, the average viraemia titre being 12 PFU/10(7) leucocytes. After the administration of a four-fold vaccine dose, 57.1% of the chicks were viraemic, the average titre being 3.2 PFU/10(7) leucocytes. After the administration of a ten-fold dose of MARVAK vaccine, 80% of the chicks were viraemic and the average titre of viraemia was 8 PFU/10(7) leucocytes. In the MFB vaccinated with the recommended dose of the MARVAK vaccine, the percentage of viraemic chickens was 48.3% and the average titre of viraemia was 6.5 PFU/10(7) leucocytes. In the pullets examined at the age of 20 weeks the number of viraemic birds ranged from 20 to 50% and the average viraemia titres were from 3.8 to 13.1 PFU/10(7) leucocytes. In the flock affected by acute MD, no post-vaccination viraemia was found in the clinically diseases pullets. In the chickens of the HX-SL line vaccinated with the recommended MARVAK vaccine dose, viraemia culminated in the third week after vaccination (31.5 PFU/10(7) leucocytes), and after the use of the dose ten times as high as the recommended one the culmination came a week later (47 PFU/10(7) leucocytes). In the Shaver chicks vaccinated with the recommended dose or with the ten-fold dose of the MARVAK vaccine, the post-vaccination viraemia culminated in the fourth week after vaccination (94.9 and 116.8 PFU/10(7) leucocytes). The post-vaccination precipitation antibodies were first detected in the eighth week after vaccination.