Effects of a blend of essential oil compounds and benzoic acid on performance of broiler chickens as revealed by a meta-analysis of 4 growth trials in various locations

A series of growth trials with broiler chicks was conducted in various geographical locations to evaluate the efficacy of a novel eubiotic feed additive (EFA) at various dietary inclusion levels on performance of growing chicks. The EFA product consisted of a blend of essential oil compounds (thymol, eugenol, piperine) with benzoic acid, all belonging to the group of flavoring substances. Although variable in responses, the overall results indicated that 300 mg/kg of this EFA represented an optimum supplementation dose for generation of beneficial performance effects in broilers. A meta-analysis with all data from the 300 mg/kg EFA-supplemented treatments in comparison with the non-supplemented controls revealed that the eubiotic product significantly improved BW on d 21 (+2.0%; P = 0.0021) and on d 42 (+1.4%; P = 0.0151). Furthermore, the birds on the EFA 300 mg/kg treatment expressed a higher average daily gain in the starter phase (d 1-21; +2.1%; P = 0.0023) and over the entire experimental period (d 1-42; +1.5%; P = 0.0154). Feed conversion ratio was more favorable with dietary EFA supplementation (-0.6%; P = 0.0414), when compared with the control birds. Mortality was considered normal and was not affected by the dietary treatment (control = 3.09%; EFA 300 mg/kg = 3.26%). In conclusion, 300 mg/kg of this new eubiotic product demonstrated to effectively improve performance of broiler chicks under various husbandry conditions.

Consequences of phosphorus interactions with calcium, phytase, and cholecalciferol on zootechnical performance and mineral retention in broiler chickens

The objective was to determine the effect of calcium (Ca), total phosphorus (Ptot), cholecalciferol, and phytase level in the diet on the performance, tibia ash percentage, and Ca and P retention in broilers until slaughter age. Broilers were randomly assigned to 12 treatments, each with 6 replicates, comprising 3 diets differing in Ca and P level: 1) normal Ca and Ptot level (NN); 2) normal Ca and low Ptot level (NL), 3) low Ca and Ptot level (LL). Broilers were also given 2 levels of cholecalciferol and 2 levels of phytase. The normal levels of Ca and Ptot for the starter, grower, and finisher phases were 0.90, 0.82, 0.74% and 0.67, 0.62, 0.57%, respectively. The low Ca and Ptot levels for the 3 phases were 0.67, 0.60, 0.52% and 0.57, 0.51, 0.46%, respectively. Broilers of the NL treatment obtained the lowest BW, whereas BW of the NN and LL groups were comparable. Cholecalciferol significantly affected the BW, with differences up to 2.6 and 1.2% for the starter and grower phases, respectively. The highest cholecalciferol effect was found in combination with the NN treatment. The percentage of retained Ca increased from 33% to 41% and 48% when the imbalanced diet was replaced by the NN and LL balanced diets, respectively. P release from phytate was 64 and 67% for the NL and LL diets, respectively. Phytase and cholecalciferol had significantly favorable effects on retention values but these effects were dependent on Ca and Ptot levels and their ratio. In conclusion, both diets with the balanced Ca/Ptot ratio resulted in the best performance, highest tibia ash percentage and P release from phytate. A reduction of the Aviagen (2009) recommended P requirements by 25 to 30% and Ca by 15 to 20% over the various phases did not negatively affect performance, bone development, and improved Ca and Ptot retention. The effects of supplementing cholecalciferol and phytase were additive but not significant and no synergism between both was present.

Egg yolk fatty acid profile in relation to dietary fatty acid concentrations

BACKGROUND

The health benefits of n-3 fatty acids have led to much research on manipulating the fatty acid composition of animal-derived foods. In this study, two experiments were conducted to investigate the interaction of dietary fatty acids on egg yolk fatty acid concentrations. In experiment I, 32 dietary treatments with three replicates of three birds each were fed for 35 days. Diets were prepared by mixing one type of fish oil with four vegetable oils in different proportions. In experiment II, three different types and two levels of fish oil in combination with two vegetable oils were tested under the same conditions as in experiment I.

RESULTS

In experiment I the results showed that the egg yolk saturated (SFA) and monounsaturated (MUFA) fatty acid concentration was determined by the dietary SFA, MUFA and 18:2n-6 content. The egg 18:2n-6 concentration was mainly explained by the dietary inclusion of 18:2n-6 and negatively by the dietary MUFA content. The egg C18:3n-3, C20:5n-3 and C22:6n-3 concentration is almost exclusively determined by their direct supply from the diet. The egg 20:4n-6 concentration was inversely proportional to the long-chain n-3 polyunsaturated fatty acid content of the diet. The results of experiment II showed that the egg yolk C20:5n-3 and C22:6n-3 concentration was determined by both the level of dietary fish oil (1 or 2%) and the C20:5n-3/C22:6n-3 ratio in the fish oil.

CONCLUSION

The results of this study demonstrated that the direct dietary supply of fatty acids is the most important factor determining the egg yolk fatty acid composition, in particular for the n-3 fatty acids. The interaction effect from other dietary fatty acids was in general small.

Distribution and depletion of flubendazole and its metabolites in edible tissues of guinea fowl

1. We measured the distribution and depletion of residues of flubendazole and its major metabolites in breast muscle, thigh muscle and liver of guinea fowls during and after oral administration of the veterinary medicine Flubenol 5% at two doses. 2. The guinea fowls were treated orally with normal feed, medicated at doses of 56 and 86 mg per kg feed for 7 successive days. Afterwards, depletion was observed for 8 d. Just before slaughter, body weights were measured. Thigh muscle, breast muscle and liver of three female and three male birds were sampled. The concentrations of the flubendazole-derived residues were determined by a liquid chromatographic-mass spectrometric method. 3. The highest residue concentrations were obtained for the reduced metabolite. With the therapeutic dose, the maximum mean residue concentrations obtained for this compound in thigh muscle, breast muscle and liver were 312, 288 and 1043 microg/kg, respectively. The values for flubendazole, the parent molecule, were 114, 108 and 108 microg/kg, respectively. The residues of the hydrolysed metabolite were negligible in the sampled muscle tissues. After 24 h of depletion, the sum of the residues of parent and metabolites in muscle tissue still exceeded 50 microg/kg. After 8 d of depletion, flubendazole-derived residues at low concentrations could still be measured in both muscle tissues and liver. Generally, the disposition of residues in breast and thigh muscle was comparable. 4. The European Union has not established a maximum residue limit (MRL) for flubendazole in edible tissues of guinea fowl. In contrast, the existing MRLs for other bird species are expressed as the sum of parent flubendazole and its hydrolysed metabolites. An estimated withdrawal period of three days will assure residue safety in the edible tissues of guinea fowl treated with flubendazole at therapeutic dose. After this withdrawal period following treatment of the guinea fowl, the residues were approximately constant, very low and far below the established safe MRL level for other bird species.

Effects of diet, age and gender on the polyunsaturated fatty acid composition of broiler anatomical compartments

1. The objective of this study was to investigate the effect of dietary fatty acid (FA) composition, age, and gender on the FA composition of different broiler anatomical compartments. Four dietary fat sources (palm fat, P; soybean oil, S; linseed oil, L; fish oil, F) were added to a wheat-soybean meal based diet at 30 g/kg in addition to 50 g/kg palm fat. Diets were fed separately to female and male birds from d 1 to either d 21 or d 42 of age. 2. The total FA content (mg/100 g tissue) and the FA composition (g/100 g FAME) was determined in 7 anatomical compartments (skinless thigh muscle, skinless breast muscle, liver, heart, brain, abdominal fat pad, and remainders plus carcase trimmings named Rest compartment). The FA profiles differed greatly among compartments and were strongly affected by diet. 3. The S diet resulted in a 2-3-fold increase of the proportion of C18:2n-6 and C20:4n-6 in all compartments compared to the other diets, except for brain. 4. The response in the proportion of C18:3n-3 following feeding the L diet was much greater, with 4-20-fold increases compared to the other diets, except again for brain. 5. In all compartments except brain, the L diet resulted in approximately a 2-fold increase in the proportion of C22:6n-3 compared to the P and S diets and smaller, but also significant, increases for C20:5n-3 and C22:5n-3. 6. The proportions of C20:5n-3, C22:5n-3 and C22:6n-3 were much higher on the F diet in all compartments, except for brain, compared to the P and S diets. The F diet resulted in higher proportions of C22:6n-3 than the proportions of C20:5n-3 and C22:5n-3 in breast and thigh meat, and liver, in contrast to the other diets. 7. Brain was less responsive than other tissues to changes in the dietary FA composition. The proportion of C22:6n-3 in brain was similar on the L and F diets. 8. The effect of gender on the FA composition of different anatomical compartments was marginal. The long-chain n-3 and n-6 PUFA in breast, liver, and brain decreased with age.

The impact of nutrient density in terms of energy and/or protein on live performance, metabolism and carcass composition of female and male broiler chickens of two commercial broiler strains

The objective of this study was to investigate the effects of diet composition on performance, slaughter yield and plasma metabolites, as different modern broiler strains show different responses to feed intake. Broilers of two commercial strains and of both sexes received one of three diets being different in energy and/or protein level [control diet, low energy/low protein diet (LM/LP) and low protein diet (LP)]. Low energy/low protein diet chickens were characterized by significantly lower body weights and feed intake compared with their LP and control counterparts. Broilers of the Cobb strain or broilers that were fed the control diet were most efficient in converting energy to body weight. No significant differences in plasma metabolites were detected due to diet composition or genotype. The diet with the lower energy and crude protein levels reached the lowest slaughter yield but the highest drumstick and wing percentages. The lowest mortality percentages were observed for broilers fed the LM/LP diet, and Cobb birds appeared to be more sensitive for metabolic disorders resulting in death. It is obvious from this study that different genotypes respond differently to changes in diet composition and therefore have adjusted nutritional requirements.

Deposition and depletion of five anticoccidials in eggs

Anticoccidials are compounds that are widely used as feed additives to prevent and treat coccidiosis. They are licensed for use in a prescribed concentration and during a certain time interval for broilers and pullets but not for laying hens. It was shown in the past that carry-over at the feeding mill is found to be the main reason for the presence of residues in eggs. An animal experiment was set up to investigate the effect of carry-over at the feeding mill on the presence of residues of anticoccidials in eggs. For the compounds diclazuril, robenidine, halofuginone and nicarbazin in combination with narasin, two concentration levels were tested: the maximum allowed concentration for broilers (100%) and a concentration corresponding to 5% carry-over during feed preparation. Also dimetridazole was included in the experiment but only at one concentration level. Eggs were sampled during treatment (14 days) and for a period of 30 days after withdrawal of the anticoccidial-containing feed. Residues were determined, and deposition and depletion curves were generated. Analyses were performed by ELISA and LC-MS/MS. For all compounds, substantial residues could be found in the 5% groups, which points out the risk of carry-over at the feeding mill. The distribution of the residues between egg yolk and white was determined by analyzing both fractions.

Clostridium perfringens in poultry: an emerging threat for animal and public health

The incidence of Clostridium perfringens-associated necrotic enteritis in poultry has increased in countries that stopped using antibiotic growth promoters. Necrotic enteritis and the subclinical form of C. perfringens infection in poultry are caused by C. perfringens type A, producing the alpha toxin, and to a lesser extent type C, producing both alpha toxin and beta toxin. Some strains of C. perfringens type A produce an enterotoxin at the moment of sporulation and are responsible for foodborne disease in humans. The mechanisms of colonization of the avian small intestinal tract and the factors involved in toxin production are largely unknown. It is generally accepted, however, that predisposing factors are required for these bacteria to colonize and cause disease in poultry. The best known predisposing factor is mucosal damage, caused by coccidiosis. Diets with high levels of indigestible, water-soluble non-starch polysaccharides, known to increase the viscosity of the intestinal contents, also predispose to necrotic enteritis. Standardized models are being developed for the reproduction of colonization of poultry by C. perfringens and the C. perfringens-associated necrotic enteritis. One such model is a combined infection with Eimeria species and C. perfringens. Few tools and strategies are available for prevention and control of C. perfringens in poultry. Vaccination against the pathogen and the use of probiotic and prebiotic products has been suggested, but are not available for practical use in the field at the present time. The most cost-effective control will probably be achieved by balancing the composition of the feed.

Detection of residues of the coccidiostat diclazuril in poultry tissues by liquid chromatography-tandem mass spectrometry after withdrawal of medicated feed

A liquid chromatography-tandem mass spectrometric (LC-MS/MS) method for the quantitative determination of diclazuril in poultry tissues and feed is presented. A simple clean up with an organic solvent was carried out. A reversed-phase C(18) column was used for the high-performance liquid chromatography (HPLC) to separate the analyte with a gradient of acetonitrile and water as mobile phase. The precursor ions produced by electrospray negative ionization were selected for collisional dissociation. Validation of the methods was performed based on Commission Decision 2002/657/EC (Off. J. Eur. Communities 2002, L221, 8-36). For the detection of diclazuril in poultry meat, the decision limit was found to be 0.5 microg/kg. An animal experiment was set up in which 70 chickens were held for 6 weeks. From day 22 until day 32, they were fed feed containing 730 microg/kg diclazuril. From day 33 until day 42, every day six chickens were slaughtered, and breast, thigh, and liver were analyzed. Average steady-state concentrations of 94, 135, and 722 microg/kg in breast, thigh, and liver were obtained, respectively. Nine days after withdrawal of the medicated feed, diclazuril was still present in the different sample types.

The efficiency of nitrogen retention during compensatory growth of food-restricted broilers

1. Two experiments were conducted to investigate the influence of compensatory growth, induced by early quantitative food restrictions, on the efficiency of nitrogen-retention in two lines of Ross broilers. 2. Birds were restricted to 80% of the ad libitum intake of the previous 24 h of the control group from d 4 to d 7. After the period of restrictions all birds were fed ad libitum. 3. In both trials, the final body weight of the restricted Ross 208(308) birds was similar or even higher than that of the control group. For the Ross 508 line, compensatory growth was substantial in the first trial, but non-existent in the second trial. In all cases, the mortality of restricted birds was lower than in control birds. 4. Not only environmental factors, but mainly chick quality, seemed to have a major influence on the capacity of the chickens to establish compensatory growth. 5. As compensatory growth was established, some improvement in N retention was induced. Although differences were not significant, they may be environmentally important. 6. It is concluded that a retardation of the early growth of fast growing broiler chickens can, in certain circumstances, reduce mortality and increase performance and N retention.

The deposition of conjugated linoleic acids in eggs of laying hens fed diets varying in fat level and fatty acid profile

The objective of this study was to investigate the incorporation of conjugated linoleic acid (CLA) into eggs and its effect on the fatty acid metabolism when layers are fed diets with different fat sources and fat levels. Layers were fed either a low fat diet (LF) or one of three high fat diets based on soybean oil (SB), animal fat (AF) or flaxseed oil (FSO). CLA was added at a concentration of 1 g/100 g feed from two different CLA premixes with a different CLA profile. For the trial, 144 laying hens were allocated to 12 treatments (4 basal fat sources x 3 CLA treatments) with 3 replicates of 4 hens each. No significant differences were observed in feed intake, egg weight, feed conversion or laying rate between chickens fed control and CLA-supplemented diets. Differences in yolk fat, cholesterol or yolk color were not clearly related to the dietary CLA. However, the supplementation of CLA to the diets had clear effects on the fatty acid composition, i.e., a decrease in monounsaturated fatty acids (MUFA) and an increase in saturated fatty acids (SFA) was observed, whereas the polyunsaturated fatty acids (PUFA) content were essentially unaffected. The results suggest that CLA may influence the activity of the desaturases to a different extent in the synthesis of (n-6) and (n-3) long-chain fatty acids. These effects of CLA depend on the level of (n-6) and (n-3) fatty acids available in the feed. The apparent deposition rate (%) is clearly higher for the c9, t11 isomer than for the t10, c12 isomer. Adding CLA to layers diets rich in (n-3) fatty acids produces eggs that could promote the health of the consumer in terms of a higher intake of (n-3) fatty acids and CLA.

Determination of flubendazole and its metabolites in eggs and poultry muscle with liquid chromatography-tandem mass spectrometry

The optimization of a quantitative and sensitive LC-MS/MS method to determine flubendazole and its hydrolyzed and reduced metabolites in eggs and poultry muscle is described. The benzimidazole components were extracted from the two matrices with ethyl acetate after the sample mixtures had been made alkaline. The HPLC separation was performed on an RP C-18 column with gradient elution, using ammonium acetate and acetonitrile as mobile phase. The analytes were detected after atmospheric pressure electrospray ionization on a tandem quadrupole mass spectrometer in MS/MS mode. The components were measured by the MS/MS transition of the molecular ion to the most abundant daughter ion. The overall extraction recovery values for flubendazole, the hydrolyzed metabolite, and the reduced metabolite in eggs (fortification levels of 200, 400, and 800 microg kg(-1)) and muscle (fortification levels of 25, 50, and 100 microg kg(-1)) were, respectively, 77, 78, and 80% and 92, 95, and 90%. The trueness (fortification levels of 400 and 50 microg kg(-1), respectively, for eggs and muscle), expressed as a percentage of the added values for these analytes, was, respectively, 89, 100, and 86 and 110, 110, and 98%. The proposed MS detection method operating in the MS/MS mode is very selective and very sensitive. The limits of detection for flubendazole and its hydrolyzed and reduced metabolites in egg and muscle were, respectively, 0.19, 0.29, and 1.14 microg kg(-1) and 0.14, 0.75, and 0.31 microg kg(-1). The limits of quantification were, respectively, 1, 1, and 2 microg kg(-1) and 1, 1, and 1 microg kg(-1). The discussed method was applied to a pharmacokinetic study with turkeys. Residue concentrations in breast and thigh muscle of turkeys orally treated with flubendazole were quantified. Medicated feed containing 19.9 and 29.6 mg kg(-1) flubendazole was provided to the turkeys for seven consecutive days. For the trial with the recommended dose of 19.9 mg kg(-1), one day after the end of the treatment, the mean sum of the flubendazole plus hydrolyzed metabolite residue values in thigh and breast muscle declined to below the maximum residue limit (50 microg kg(-1)) and were, respectively, 36.6 and 54.1 microg kg(-1). The corresponding values with the higher dose of 29.6 mg kg(-1) were, respectively, 101.7 and 119.7 microg kg(-1).

The bioefficacy of zinc bacitracin in practical diets for broilers and laying hens

Two balance trials were conducted to examine the response in metabolizable energy and metabolizability of both fat and amino acids to graded levels of zinc bacitracin (ZnB; Albac registered trade name of Alpharma, Oslo, Norway) in practical broiler and layer diets varying in their nutrient density. Broiler diets were supplemented with either 0, 20, or 50 mg ZnB/kg and layer diets were supplemented with either 0, 50, or 100 mg ZnB/kg. Each experimental diet was fed to five replicates of four broiler chicks each or nine replicates of individually housed laying hens, respectively. All balance parameters were significantly influenced by nutrient density, age, and dietary ZnB level. No significant interactions between ZnB by nutrient density were found. Addition of ZnB resulted in a lower excreta:feed ratio and an improved N retention; there was a nearly linear relationship between these effects and dietary ZnB levels. Moreover, dietary MEn content was linearly enhanced by ZnB supplementation. As a consequence, the bioefficacy of ZnB can be expressed in terms of MEn units: the average MEn equivalency of ZnB was 2,080 and 1,184 Mcal/kg, for broiler chicks and laying hens, respectively.

Effects of dietary protein content, addition of nonessential amino acids and dietary methionine to cysteine balance on responses to dietary sulphur-containing amino acids in broilers

1. Two experiments were conducted with male broiler chicks from 2 to 5 weeks of age to determine the effect of dietary protein content and amino acid balance on the response to dietary sulphur-containing amino acids (SAA) in terms of performance and carcase quality. 2. In experiment 1, 5 graded amounts of a DL-methionine and L-cysteine (1:1 by weight) mixture were added to basal diets containing 197 or 233 g crude protein/kg. The diets containing 197 g protein/kg were fed with or without the further addition of 36 g crude protein/kg from nonessential amino acids. The amino acid balance of all diets was kept constant for all essential amino acids except the SAA. In experiment 2, 5 graded amounts of SAA from either a crystalline source (DL-methionine or a mixture of DL-methionine and L-cysteine) or from intact proteins were added to a diet containing 208 g protein/kg. 3. At each protein concentration there were significant responses to the SAA addition in weight gain, food conversion efficiency, and carcase quality. Non-linear exponential regression analyses were used to describe bird responses to SAA concentration. The broiler chick's requirement for SAA increased with increasing dietary protein concentrations ranging from 197 to 259 g protein/kg. 4. The utilisation of SAA differed also with differences in origin (crystalline or peptide-bound), and methionine:cysteine balances. Compared to DL-methionine, a 1:1 mixture of DL-methionine and L-cysteine was only 81% or 86% as effective in supporting growth or food conversion, respectively. SAA from added protein was even less effectively utilised. 5. The addition of nonessential amino acids tended to decrease food intake without affecting SAA utilisation. 6. Slaughter yield and breast meat yield were clearly increased while fat deposition was clearly decreased, by SAA addition. The response in breast meat yield suggested an important economic benefit for further meat processing. Nitrogen retention was significantly enhanced by SAA supplementation from crystalline sources, and this led to reductions of up to 30% in the amount of nitrogen excreted per kg weight gain.

Optimum threonine requirement of laying hens

1. One experiment was conducted with medium weight laying hens to determine their threonine requirement between 28-38 weeks. 2. Two threonine-limiting diets of identical protein quality (summit-dilution) were used and, by dilution, ten protein contents were produced supplying 2.7 to 5.4 g total threonine/kg diet. The diet with the lowest protein was also supplemented with synthetic L-threonine. Each diet was fed to 5 groups of 24 laying hens. 3. The daily threonine requirement of the individual laying hens was estimated by direct methods to be 8.7 mg/g egg output plus 43.49 mg/kg body weight for this experiment. Calculated optimum intakes of threonine for various ratios of costs of input to value of output are tabulated. For example, for a flock of medium weight laying hens producing an average of 50 g daily egg mass, the optimum threonine intake (mg/hen d) varied between 700 and 710 for cost ratios (k-values) varying between 0.002 and 0.001.

Optimum isoleucine requirement of laying hens and the effect of age

1. Medium weight laying hens were used for an assay to determine their isoleucine requirement between 26 and 36 weeks of age and again between 46 and 56 weeks of age. 2. Two isoleucine-limiting mixtures were formulated with similar amino acid profiles, one containing 198 g and the other 110 g crude protein per kg diet. These mixtures were blended to give a series of 11 diets with isoleucine contents ranging from 7.6 to 3.8 g/kg. The lowest protein diet was also fed with a supplement of L-isoleucine. Each of the 12 diets was given to 5 groups of 24 laying hens. 3. The daily isoleucine requirement of individual laying hens was estimated to be 9.48 mg/g egg output plus 44.47 mg/kg body weight per day for the 1st period and 12.11 mg/g egg output plus 6.86 mg/kg body weight per day for the 2nd period. Calculated optimum intakes of isoleucine for various ratios of cost of input to value of output are tabulated. For example, for a flock of medium weight hens producing an average of 50 g daily egg mass, the optimum isoleucine intake (mg/hen d) varied between 760 and 890 varying for ratios of costs to egg prices. 4. It is concluded that the isoleucine required per day does not decrease during the first laying year despite a decrease in rate of egg output.

The effect of clenbuterol supplementation on growth performance and on plasma hormone and metabolite levels of broilers

In the present experiment, clenbuterol was supplemented (.42 ppm) from Day 1 or from 2 or 4 wk of age until slaughter age (6 wk). The effects on growth performance and on plasma hormone and metabolite profiles were investigated at 2, 4, and 6 wk of age in male and female broilers. There were no consistent or cumulative effects of clenbuterol feeding on growth and feed efficiency. Clenbuterol feeding from Day 1, but not later, depressed subsequent feed intake. Relative abdominal fat pad weight was reduced profoundly and was even more pronounced after prolonged supplementation and for females. Fat content of thigh meat (including skin), but not of breast meat (without skin), was reduced by clenbuterol feeding. No consistent effects of clenbuterol supplementation on plasma thyroid hormones, growth hormone, insulin-like growth factor-I, and corticosterone levels were detected. Very low density lipoprotein (VLDL) concentrations were depressed in male broilers fed clenbuterol for 6 wk, but the plasma triglyceride level did not follow this pattern. There was no evidence for a consistent effect of clenbuterol on lipolysis in vivo, measured by plasma glycerol level. Between 4 and 6 wk of age, plasma VLDL and glycerol levels decreased in females but increased in males. This corresponds to the higher fat deposition in females. However, the most consistent effects were age-related changes in the plasma levels of most hormones and metabolites. From the present study, it seems that clenbuterol acts primarily on fat deposition, the extent being dependent on sex, location of fat, and duration of beta-adrenergic agonist supplementation.

European reference method for the in vivo determination of metabolisable energy with adult cockerels: reproducibility, effect of food intake and comparison with individual laboratory methods

1. A common reference procedure adopted by several European laboratories to determine apparent metabolisable energy corrected to zero-nitrogen balance (AMEn) is described. 2. Reproducibility has been estimated by comparing results from 4 diets measured in 7 laboratories. The standard deviations between laboratories of dry matter, gross energy, Kjeldahl nitrogen and AMEn were respectively, on average, 11.29 g/kg, 0.242 MJ/kg, 1.56 g/kg and 0.380 MJ/kg dry matter; the corresponding coefficients of variation between laboratories were 1.27, 1.29, 4.39 and 2.92%. 3. Effect of food intake was tested by comparing AMEn from birds fed either 0.90 or 0.45 of ad libitum: the amount of food intake had a negligible effect on AMEn values. Endogenous energy losses corrected (EELn) or not (EEL) to zero nitrogen balance were estimated either by regression between excreted energy and ingested energy or in fasted and glucose-fed cockerels. EELn estimated by regression was, on average, 8.7 kJ/bird/d.; it was independent of diet composition. EEL and EELn determined in fasted or glucose-fed birds were higher than those determined by regression. 4. AMEn values measured by individual laboratory procedures were very close to those obtained by the reference method, except from laboratories using a tube feeding procedure, where deviations were probably a consequence of overestimated EEL.

European reference method of in vivo determination of metabolisable energy in poultry: reproducibility, effect of age, comparison with predicted values

1. Apparent metabolisable energy corrected to zero-nitrogen retention (AMEn) was measured using the European reference procedure in 9 European laboratories. Seven pelleted diets were evaluated. AMEn was measured with adult cockerels and young birds. 2. Between-laboratory standard deviations were for dry matter (DM) 12.5 g/kg, gross energy 0.085 MJ/kg DM, Kjeldahl nitrogen 0.768 g/kg DM, AMEn (adults) 0.256 MJ/kg DM, and AMEn (young) 0.337 MJ/kg DM. Corresponding coefficients of variation between laboratories were 1.42, 0.45, 2.15, 1.88 and 2.60% respectively. 3. AMEn values of experimental diets were always significantly lower when measured with young birds. This effect was more pronounced when diets contained added fat. 4. Tallow or soyabean oil were incorporated into two basal diets at 40 g/kg inclusion rate. No significant differences were observed between AMEn values of either diet with adults or young birds, suggesting that AMEn energy values of these fats are indistinguishable at this inclusion rate. 5. Similar AMEn values were obtained in young birds by estimating nitrogen accretion, either by the difference between intake and excreta nitrogen or by measuring body weight gain. Determined AMEn values were very similar to those predicted using three different regression equations.

Current role of semen storage and artificial insemination in the turkey industry

The turkey industry is moving towards the development of stud farms, but an essential condition is the existence of efficient methods to store semen. Much research has been done recently to determine the number of viable spermatozoa in an insemination dose needed for maintaining optimum fertility. Practical methods to determine the number of intact spermatozoa in semen, both before and after storage, are under development. It is now possible to store turkey semen for 6 to 24 h without appreciable loss in fertility and hatchability. Ideal experimental conditions for 48 h storage have not yet been fully determined. Development of new storage media, allowing the insemination of very low numbers of spermatozoa, may provide interesting possibilities regarding the use of elite sires.

Effect of dietary fluoride on performances and bone characteristics of broilers and the influence of drying and defatting on bone-breaking strength

A trial with broiler males, housed in cages, was conducted to determine the effect of (added) dietary fluoride at 0, 200, and 400 mg/kg on performance and bone characteristics and the influence of preconditioning (drying, defatting) on bone-breaking strength. The F administration resulted in a significantly (P less than .05) lower weight gain. Feed conversion, however, was not affected. Tibial ash deposition and ash-percentage increased significantly (P less than .05) at both dietary levels of added F. Broiler males fed supplemented F had a significantly (P less than .05) higher incidence of tibial dyschondroplastic plugs and epiphyseal bone with looser structure, as judged macroscopically. Tibial bone strength was significantly (P less than .05) affected not only by dietary F level, but also by preconditioning, resulting in a significant interaction. Administration of F had a significantly negative or positive effect on breaking strength, depending on whether the measurements were carried out on fresh bones or dried (defatted) bones, respectively. This diverging response of F on breaking strength offers a valid explanation for the contradictory results in the literature, demonstrating at the same time that F supplementation of feed or drinking water should be discontinued as a method to improve bone-breaking strength.