Lack of effect of body weight of breeder pullets at various ages and the amount of food allocated on their subsequent laying performance.

1. Two factorial experiments were carried out with White Rock (Arbor Acres) female pullets, kept in layer cages, to evaluate the relationship between body weight (BW) at different ages and the amount of food allocated (FA) on laying performance. Differences in BW at the beginning of experiments 1 and 2 (12 and 18 weeks of age, respectively) were obtained by segregating pullets raised under the recommended FA into weight groups (WGs): standard (ST), light BW (LBW) and heavy BW (HBW). Each of the 3 WGs was further divided into 2 subgroups, raised either under the recommended FA or a moderately increased FA until 34 weeks of age. The experiments were terminated at approximately 65 weeks of age. 2. Body weight was significantly (P < 0.05) affected by WGs until 28 and 60 weeks, and by FA until 56 and 44 weeks of age in experiments 1 and 2, respectively. The increased FA significantly accelerated the age of onset of egg production and increased BW at that time. Neither of these variables was affected by BW at 12 weeks of age. BW at 18 weeks of age did not affect age of sexual maturity, but at that time the BW of the LBW- and the HBW-birds was significantly lower and higher, respectively, than that of the ST-birds. 3. Number of eggs per laying or per housed hen was not affected by the WG and/or FA. The exception was the significant interaction between the 2 factors in their effect on the number of eggs per laying hen observed in experiment 1, in which the increased FA prevented the decline in the HBW-birds. 4. The data suggest that the laying performance of broiler breeder hens segregated according to their weight at 12 or 18 weeks of age, and kept in layer cages is not affected by their weight at these ages, and thereafter. The effects of a moderate increase in FA, and of the interaction between this factor and WGs, on laying performance, are not straightforward.

Lack of interrelationship between the effects of dietary factors and food withdrawal on carcase quality of broiler chickens.

1. Four factorial experiments were carried out to determine whether there is any interrelationship between dietary energy-to-protein (E:P) ratio (experiments 1, 2 and 3) or pelleting the diet (experiment 4) and the duration of food withdrawal (FW), in their effect on carcase quality of broiler male chickens. The quality was evaluated by yields of carcase and breast meat, abdominal fat pad size, and the content and composition of the fat in the meat. The effect of sex on the response to FW was also determined in experiment 3 and that of age in experiment 4. 2. The diet with an E:P ratio higher than recommended decreased the weights of carcase and breast meat significantly (P < 0.05) in 2 of the 3 experiments, and consistently increased the size of the abdominal fat pad and the fat content in thigh, but not in breast meat. Abdominal fat pad and the fat in meat of birds fed on this diet contained a significantly higher amount of oleic acid and a lower amount of linoleic acid, than the fat of birds fed on the diets with the recommended and the low E:P ratios. The pellets increased significantly the weights of carcase and breast meat and the relative size of abdominal fat pad. 3. FW for 24 h decreased significantly the weight at slaughter in all 4 experiments, carcase weight in 3 experiments, and breast weight in 1 experiment. However, it did not affect the relative size of the abdominal fat pad, the fat content in thigh and breast meat, and the composition of fatty acids in these tissues and in abdominal fat. None of the variables mentioned was affected significantly by the interaction between the dietary factors evaluated, sex or age of the birds on the one hand, and FW on the other hand. 4. It is concluded that the effect of 24 h of FW on weight at slaughter, carcase and breast meat weights and on fattening, is not affected by dietary E:P ratio, pelleting the diet, or sex and age of the broilers.

Humoral immune response impairment following excess vitamin E nutrition in the chick and turkey.

The effect of high dietary intakes of vitamin E on antibody production was investigated in chicks and turkeys. Chicks were fed four diets with 0, 10, 30, and 150 mg/kg added vitamin E and turkeys were fed three diets with 0, 50, and 150 mg/kg added vitamin E. Antibodies produced in response to naturally occurring Escherichia coli and to Newcastle disease virus and turkey pox vaccines were determined. In chicks, antibody production in response to E. coli and Newcastle disease was affected by vitamin E nutrition: significantly higher responses were measured in chicks that received 0 and 10 mg/kg added vitamin E, whereas in chicks receiving 30 and 150 mg/kg, antibody production was significantly lower. In turkeys, concentrations of circulating antibodies to Newcastle disease virus and to turkey pox were also influenced by dietary vitamin E: antibody titers to Newcastle disease and turkey pox vaccines were highest in groups receiving 0 mg/kg added vitamin E, whereas titer in groups receiving 150 mg/kg were significantly lower. Responses of groups receiving 50 mg/kg added vitamin E were slightly lower than groups receiving 0 mg/kg, though not significantly so in most cases. These results indicate that humoral immune responses are directly effected by vitamin E, and that excessive vitamin E intake has a detrimental effect on antibody production in chickens and turkeys.

Moderate excess of dietary protein increases breast meat yield of broiler chicks.

Two factorial experiments were carried out to evaluate the effects of dietary protein level, expressed as energy to protein (E:P) ratio, on yields of carcass and breast and on abdominal fat pad weight of male broiler chicks at 43 and 57 d of age. Two diets similar in their energy content and differing markedly in their protein content, in which the E:P ratios were lower and identical to the NRC (1994) recommendations, were used in Experiment 1. Four diets, the combination of two energy and two protein levels, in which the E:P ratios were lower and identical to the recommendations, were used in Experiment 2. There were no differences in feed intake or weight gain until 42 d of age between broilers fed the diets with the low and those fed the recommended E:P ratio. However, feed efficiency of the former was consistently and significantly (P < 0.05) higher. The high-energy diets did not affect feed intake but significantly improved weight gain between 7 and 28 d of age and feed efficiency until 42 d of age. In both experiments, carcass yield was not affected by dietary E:P ratio at 43 d of age; however, at 57 d of age it was increased significantly by the low E:P ratio in Experiment 1 and in birds fed the high energy diet in Experiment 2. On a factorial basis, the effect of the low E:P ratio on increasing yield was significant only in Experiment 1. The high dietary energy level increased carcass yield only at 43 d of age, but on a factorial basis its effect was significant. Carcass yield was significantly (P < 0.001) higher at 57 than at 43 d of age. In both experiments, breast meat yield was negatively correlated with dietary E:P ratio, a significant factorial effect. The difference in this variable between broilers fed the diets containing the low and the recommended E:P ratio was significant, at both ages in Experiment 1, and only at 57 d of age in Experiment 2. Breast meat yield was not affected by dietary energy level, and it was significantly (P < 0.001) higher at 57 than at 43 d of age. Relative abdominal fat pad weight was increased significantly by increasing dietary E:P ratio. Dietary energy level and age did not affect this variable. The relationship between abdominal fat pad weight and breast meat yield within the treatments tended (in most of the cases not significantly) to be negative. However, this negative relationship was significant, at both ages, when the analysis was carried out with the pooled data at each age. It is concluded that the optimal E:P ratio for maximal breast meat yield for broiler chicks, particularly at 57 d of age, may be below the NRC (1994) recommendations.

Moderate excess of dietary vitamin E does not exacerbate cholecalciferol deficiency in young broiler chicks.

1. The combined effect of moderate excess dietary vitamin E and marginal amounts of dietary cholecalciferol on the performance and tibia bone ash of young male broiler chicks was evaluated. Vitamin E (alpha-tocopheryl acetate) and cholecalciferol were added to a commercial diet not already supplemented with these vitamins, at concentrations of 0 and 150 mg/kg, and 1.875, 5 and 25 micrograms/kg, respectively, and fed to chicks for 23 d. 2. Vitamin E concentration and its combinations with cholecalciferol did not significantly (P > 0.05) affect food intake, weight gain, food efficiency and bone ash. These variables were significantly (P < 0.001) lower in chicks fed on the diets supplemented with 1.875 micrograms cholecalciferol/kg compared with the values observed with the 2 other concentrations of this vitamin. There were no differences in the effects of 5 and 25 micrograms cholecalciferol/kg diet on the above variables. 3. It was concluded that vitamin E, at a concentration of 150 mg/kg diet, did not aggravate a mild cholecalciferol deficiency.

The response of broiler chickens and turkey poults to dietary energy supplied either by fat or carbohydrates.

The efficacy of fat and carbohydrates as energy sources was compared in 1- to 4- and 4- to 7-wk-old broiler chickens and in 16- to 19-wk-old turkeys. An increase in dietary energy by carbohydrate was made by a graded replacement of wheat bran by wheat. Energy was increased by fat through a graded replacement of soybean hulls with refined soybean oil. In the experiments with broiler chickens, the feed efficiency responses to added energy were observed within the entire range of dietary energy tested, with no significant differences between the responses to carbohydrate and fat as energy supplements. The growth response to energy from either source appeared to be characterized by diminishing returns in the chicken. In the 16- to 19-wk-old turkeys, the growth and feed efficiency responses were linear within the range from 2,650 to 3,250 kcal/kg. In chickens and in turkeys, the growth and feed efficiency responses to energy supplied by fat were indistinguishable from those of carbohydrates. In chickens, the fractions of abdominal fat and pectoral muscle were not affected significantly by the energy density and source.

Effect of vitamin A on the oxidative stability of broiler meat during storage: lack of interactions with vitamin E.

1. An experiment was carried out with male broiler chicks to evaluate the combined effect of two concentrations of vitamin A (1.032 and 10.32 mg retinyl acetate/kg diet) and two concentrations of vitamin E (0 and 150 mg alpha-tocopheryl acetate/kg diet) on the oxidative stability of the drumstick meat of broiler chickens. The experimental diets were fed from 1 to 42 d of age. The oxidative stability, evaluated by thiobarbituric acid reactive substances (TBARS) values, was determined after 125 d of storage at -18 degrees C. 2. TBARS values were very low and not significantly affected by dietary vitamins A and E or their combinations. However, the TBARS values in the meat of birds fed on the vitamin E-free diets, but not on the vitamin E-supplemented diets, were markedly increased after using an accelerated test of oxidation of the meat lipids by incubation. This resulted in a significant (P<0.001) difference from vitamin E supplementation. Vitamin A, alone or in combination with vitamin E, did not affect TBARS values found after incubation. 3. It is concluded that vitamin A at the concentrations used had no effect on the oxidative stability of the meat, in contrast to the protective effect of vitamin E, and that there is no interaction between the effect of these two vitamins on meat stability.

Effect of storage duration on the nutritional value of corn kernels for broiler chicks.

A study was carried out to evaluate the effect of storage duration of corn on its chemical composition (DM, protein, fat, amino acid, and fatty acids) and nutritional value for chicks, with an emphasis on AMEn. Freshly harvested whole grains were stored for 110 mo in covered galvanized iron cans, kept inside a storehouse. The AMEn content of the grains was determined in 10 experiments in which the corn was incorporated in a diet designated for the evaluation of AMEn by the substitution method. These determinations were carried out with male broiler chicks at 15 to 17 d of age. The chemical composition of the grains did not change during storage, except for a significant (P < 0.02) increase in lysine and a decrease in valine levels. Moreover, the AMEn content was not affected significantly (P > 0.05) by storage duration. It is concluded, therefore, that storing corn grains for 110 mo, under proper conditions, does not adversely affect their nutritional value.

Effect of high levels of dietary iron, iron injection, and dietary vitamin E on the oxidative stability of turkey meat during storage.

A study was carried out to evaluate the combined effect of excess Fe, supplied either in the diets (Experiments 1, 2, and 3) or by injection (Experiment 4), and various levels of dietary vitamin E on the oxidative stability of the thigh muscle of turkeys stored at -18 C for various periods. Iron was added to a commercial diet that already contained 20 mg/kg supplemental Fe, at concentrations of 0, 100, 250, and 500 mg/kg as ferrous sulfate or injected as Fe-dextran to the left drumstick muscle (total amount of 1.2 g per turkey). Vitamin E was added to the experimental diets not already supplemented with this vitamin, at levels of 0, 28, and 150 mg/kg. Thiobarbituric acid reactive substances (TBARS) values of the meat gradually increased as its storage duration increased from about 15 to 120 d. Increasing dietary Fe supplementation from 0 to 500 mg/kg tended to decrease TBARS values in one experiment only; otherwise, this variable was not affected by dietary Fe level. Injection of Fe significantly (P < 0.05) increased TBARS values, only in meat from the injected side. The TBARS values of the meat up to about 30 d of storage were significantly lower due to the supplementation of the diet with vitamin E at a level of 28 mg/kg in one out of three experiments and at a level of 150 mg/kg in two out of two experiments. The protective effect of the higher level of vitamin E remained evident after about 108 d of storage. No interaction was observed between Fe and vitamin E treatments in their effect on TBARS values. Blood hemoglobin concentrations were significantly increased by the supplementation of the diet with the high levels of Fe, in one experiment only. This variable was consistently and significantly increased from about 10 to 23 wk of age. The results show that high levels of dietary Fe do not adversely affect the oxidative stability of thigh meat of turkey; however, stability might be reduced by injected Fe. Dietary vitamin E, at a level of 150 mg/kg, consistently increased this stability.

Interrelationship between the effects of dietary factors and feed withdrawal on the content and composition of liver fat in broiler chicks.

Four experiments were carried out to evaluate the effects of the composition and pelleting of diets fed to broiler chicks up to marketing age on changes in their liver size and the content and composition of liver fat due to feed withdrawal (FW) during 0, 10, and 24 h. Birds not exposed to FW that were fed diets with high energy to protein ratio (E:P) and diets in pelleted from-diets that increase fattening-had significantly (P < 0.05) higher liver fat content than those fed diets with the recommended E:P and in mash form, respectively. Those fed pellets also had higher liver weight. Dietary energy level did not affect these variables. Feed withdrawal for 10 or 24 h decreased, at times significantly, liver weight and its fat content, irrespective of the diets fed previously. The values observed after FW were not affected by the dietary factors evaluated. The composition of liver fatty acid in chicks not exposed to FW was markedly affected by increases in dietary energy (soybean oil) level and E:P. The main effects of the former were increased levels of stearic, linoleic, and arachidonic acids and a decreased level of oleic acid; those of the latter were an increased level of oleic and decreased levels of stearic, linoleic, and arachidonic acids. Irrespective of the diets used, FW increased the concentrations of stearic, linoleic, and arachidonic acids, and decreased those of palmitic and oleic acids. This effect on arachidonic acid was consistently significant, whereas the effects on the other fatty acids were significant in two out of three experiments. Due to these effects of FW, part of the differences in the composition of liver fatty acids caused by dietary factors observed in fed chicks, completely disappeared after FW. The length of FW (10 vs 24 h) did not affect liver size or fat content, but the concentrations of oleic and arachidonic acids in liver fat were significantly higher in birds exposed to 24 h of FW. It was concluded that the composition and form of the diets markedly affect liver weight and the content and composition of its fat in birds not exposed to FW. The effects of the dietary factors on liver size and its fat content completely disappear after 24 h of FW.

The use of diets containing high levels of zinc for controlling early growth in female broiler chicks.

A study was carried out with White Rock female chicks to evaluate the possibility of using dietary Zn supplied as ZnO, to control feed intake and weight gain during the period of 1 to 3 wk of age. The levels of supplemental Zn tested were 0, 0.25, 0.50, and 1.0% (Experiment 1); 0, 0.65, 0.75, and 0.85% (Experiment 2); 0.7 and 0.8% (Experiment 3). The effect of Zn supplementation was compared with that of a low sodium chloride diet (L-NaCl-D) and of severe feed restriction (SFR), which was calculated to supply energy only for maintenance (Experiments 1 and 3, respectively). The compensatory growth of the chicks from 3 to 4 wk of age was also evaluated. Feed intake and weight gain were negatively proportional to the levels of dietary Zn supplementation and there were significant (P < 0.02 and P < 0.01, in Experiments 1 and 2, respectively) negative correlations between supplemental dietary Zn levels and relative weight gains (values observed in the unsupplemented diet = 100%). The effects of L-NaCl-D and SFR on decreasing weight gain were calculated, according to the equations obtained in Experiments 1 and 2 to be equivalent to these of 0.58 to 0.65% and 0.78 to 0.87% Zn supplementation, respectively. Relative weight gain and feed efficiency of the chicks from 3 to 4 wk of age, after withdrawal of the growth-depressing factors, were positively related to the degree of growth depression during 1 to 3 wk of age; however, the intensity of recovery from a similar degree of growth depression induced by L-NaCl-D, SFR, or dietary Zn was least in the last mentioned treatment. It is concluded that dietary Zn supplementation can be used as an efficient tool for controlling early growth of young broiler breeder chicks.

Differential effect of age on metabolisable energy content of high protein-low energy and low protein-high energy diets in young broiler chicks.

1. An experiment was carried out with 6-d old male broiler chicks in an attempt to understand better the effect of age on dietary AMEn of high protein-low energy (HPLE) and low protein-high energy (LPHE) diets which are used in the determination of the AMEn content of grains when substituted for the entire diet. The experiment was carried out in a split-plot design in which the effects of 2 diets (HPLE-reference and LPHE-test, containing maize) on food intake, faecal excretion, dietary AMEn and the utilisation of the nutrients were evaluated in 3 age periods (A = 11-13, B = 15-17 and C = 20-22 d of age). 2. Chicks fed on the HPLE diet consumed significantly less food than those fed on the LPHE diet during periods A and B, but not in C. They also produced a significantly larger amount of droppings during periods B and C. Food-to-droppings ratio, which was consistently and significantly lower in chicks fed on the HPLE diet, decreased markedly in period C only in these birds. 3. Absolute and relative retention (RR) of dry matter (DM) and starch, and RR of nitrogen (N) from birds fed on the HPLE diet, were consistently and significantly lower than from those fed on the LPHE diet, but fat retention (absolute and relative) was higher. RR of DM and of N in period C was significantly lower than in periods A and B, while RR of fat and of starch was not affected by age. The effect of age on RR of N was observed only with the HPLE diet. 4. AMEn of the HPLE diet, but not of the LPHE diet, in period C was significantly lower than in periods A and B, resulting in a significant interaction between age and diet and a general reduction with age. The calculated AMEn contents of the maize in periods A and B were essentially the same (14.91 and 14.85 MJ/kg, respectively), and lower than in period C (15.28 MJ/kg). It is concluded, therefore, that because of its effect on AMEn of the HPLE reference diet in chicks older than 17 d, bird age is of considerable importance in the determination of AMEn in grains when substituted for the entire diet.

The nutritional value of high-oil corn for broiler chicks.

A variety of corn (Natan) with high fat and protein contents (6.7 and 9.8%, respectively) was developed at Newe Ya'ar, Israel. The nutritive value of this corn for broiler chicks from 7 to 28 d of age was evaluated in two experiments. In the first experiment, Natan and a local conventional corn variety (LCC-2.9% fat and 7.2% protein) were incorporated in a relatively low-protein diet designated for the determination of AMEn by the substitution method. The AMEn content of Natan was found to be 3,658 kcal/kg, whereas that of LCC was 3,437 kcal/kg. There were no differences in feed intake or weight gain between chicks fed the two corn varieties, but feed efficiency of those fed the diet containing Natan was improved (P < .05). In the second experiment, the effects on the performance of chicks of diets adequate in protein and containing either imported conventional corn (ICC), or Natan, or ICC-enriched with corn oil and soybean meal (to equalize its fat and protein content to that of the diet containing Natan), were compared. There were no differences in feed intake or weight gain among chicks fed the three diets and in feed efficiency among chicks fed the diet containing Natan and those fed the other two diets, whereas, the enrichment of the ICC-containing diet significantly improved feed efficiency. It was concluded, therefore, that in spite of the high nutritional value of the high-oil corn, its effect on improving the performance of chicks, when replacing a conventional corn in a well-balanced diet, was not pronounced.

Attempts to achieve low-weight broiler breeder hens by severe growth depression during various periods up to 6 weeks of age and food allocation below the recommendations thereafter.

1. Three experiments were carried out with White Rock (Anak) female chicks to evaluate the possibility of obtaining low-weight breeder hens and to assess their reproduction potential. Such hens were obtained by early growth depression induced by either severe food restriction (SFR) from 1 or 2 to 3 or 4 weeks of age, or a low-protein diet (LPD) fed from 0 to 6 weeks of age, or the use of diets containing 0.7 or 0.8% zinc as ZnO from 1 to 3 weeks of age, followed by food allocation below recommendation up to 22 or 67 weeks of age. 2. Body weights (BW) of the birds whose growth had been depressed were consistently and at time significantly lower than those of the control birds throughout the experiments. Age at first egg was delayed in hens previously fed the LPD and the diet containing the higher concentration of ZnO, and in those exposed to SFR from 2 to 4 weeks of age. BW at that time tended to be lower in birds whose growth had been depressed, although a significant effect was observed in only one experiment. 3. Egg production and egg size were not significantly affected by the various treatments, except for the lower production in hens fed the LPD at an early age. 4. Negative regressions (on an individual basis) were consistently observed between BW at 22 weeks of age and age at first egg, and between age at first egg and number of eggs laid. Positive regressions were observed between age at first egg and BW at that time. The regressions between BW at 22 weeks of age and number of eggs laid were positive but not always significant. 5. Severe growth depression at an early age (produced by food restriction or ZnO supplemented diet, but not LPD) followed by decreased allocation of food afterwards, could provide a means for reducing BW of broiler breeder hens without adversely affecting egg production. This procedure may save 2.5 to 6.6% of the food consumed during the life span of the birds.

Monensin toxicity in two breeds of laying hens.

A case of monensin toxicity in laying hens is reported. The drug was incorporated, by error, at a concentration of 800 mg/kg in the rations which were fed for 4 days to light (Leghorn X Rhode Island Red, LR) and heavy (White Rock, WR) breeds of laying hens. Egg production (initial levels of about 80% and 57%, in the LR and WR hens, respectively) decreased markedly 24 h after feeding the monensin-supplemented rations, and 8 days later it was less than 10% in the LR hens and had stopped completely in the WR birds. Egg production in both strains regained normal levels 30 days from the beginning of the episode. Mortality started 48 h after monensin administration, reaching a peak on the 9th and 6th days in the LR and WR hens, respectively. Mortality was much higher in the WR hens (38.3%) than in the LR hens (3.7% in shed A and 8.3% in shed B). It seems, therefore, that the WR hens were more susceptible to monensin toxicity than LR hens.

Effect of growth promoters on monensin toxicity in broiler chicks.

1. An experiment was carried out with male broiler chicks to evaluate the combined effect of monensin (150 mg/kg) and the growth promoters (GPs) Zn bacitracin (BAC, 50 mg/kg), virginiamycin (VIR, 25 mg/kg) and avoparcin (AVO, 20 mg/kg) fed from 7 to 28 d of age on performance, utilisation of dietary nutrients, yield of defeathered eviscerated carcases (DEC) and size of various organs. The effect of the GPs in the monensin-unsupplemented diets fed up to 49 d of age on performance and carcase was also determined. 2. Monensin significantly (P < 0.05) depressed food intake, weight gain and food efficiency from 7 to 28 d of age. None of the GPs was able to counteract these effects. However, AVO slightly ameliorated them. AVO also significantly increased food intake and improved gain and food efficiency during 7 to 28, but not 28 to 49 or 7 to 49 d of age. VIR and BAC did not affect performance in either age period. 3. Monensin did not affect the utilisation of dietary dry matter, fat or energy, but it significantly decreased nitrogen utilisation. AVO improved nitrogen and fat utilisation and increased dietary AME(n) content. AME(n) was also increased by VIR. The utilisation of these nutrients was not affected by the interactions between monensin and the GPs. 4. Monensin did not affect yield of the DEC or the relative liver size at 31 d of age. It significantly increased the relative length of the small intestine (SI) and decreased its specific weight. AVO significantly increased yield at 31, but not at 53 d of age. BAC and VIR did not affect this variable. AVO and VIR, but not BAC, at both age periods reduced, at times significantly, the size, length and specific weight of the SI. 5. Our conclusions: BAC, VIR and AVO do not counteract the toxic effect of monensin. The effect of GPs in improving performance decreases and even disappears with age, while their effect in reducing the size of the SI is still evident in 49-d-old birds.

Lack of effect of dietary energy-to-protein ratio and energy concentration on the response of broiler chickens to virginiamycin.

1. Two factorial experiments were carried out with male broiler chicks from 6 to 28 (experiment 1) and from 7 to 49 (experiment 2) d of age to evaluate the combined effect of virginiamycin (VIR), dietary energy concentration, and energy-to-protein (E:P) ratio on performance and the utilisation of dietary nutrients. 2. VIR had no significant effect in either experiment on food intake or weight gain, but significantly improved food efficiency up to 28 d of age (P less than 0.001 and P less than 0.05 in experiments 1 and 2, respectively). 3. VIR consistently and significantly (P less than 0.01) decreased fat excretion, improved fat relative retention and increased dietary AMEn. VIR also significantly (P less than 0.01) increased relative retention of dry matter, while it did not affect nitrogen balance. 4. Neither of the variables of performance and utilisation of dietary nutrients was affected by the interactions between VIR and either dietary E:P ratio or energy concentration. It is concluded, therefore, that the effect of VIR in increasing the utilisation of dietary energy does not depend on the above factors.

Effect of high concentrations of dietary vitamin E during various age periods on performance, plasma vitamin E and meat stability of broiler chicks at 7 weeks of age.

1. The effect of high concentrations of vitamin E (alpha-tocopheryl acetate) fed during various age periods on the performance and the oxidative stability (thiobarbituric acid [TBA] values) of the drumstick meat of 7-week-old broiler chicks was determined. The basal diets (for the age periods 0 to 3, 3 to 6 and 6 to 7 weeks) contained 60 g soyabean oil and 24 mg vitamin E/kg. The following five treatments were evaluated: (1) the basal diets from 0 to 7 weeks of age (control); (2) vitamin E, 100 mg/kg diet from 0 to 7 weeks of age; (3) vitamin E, 150 mg/kg diet from 0 to 3 weeks of age; (4) vitamin E, 150 mg/kg diet from 0 to 3 weeks of age and 100 mg/kg diet from 6 to 7 weeks of age; (5) vitamin E, 100 mg/kg diet from 5 to 7 weeks of age. 2. Food intake, weight gain and food efficiency were not significantly (P greater than 0.05) affected by the vitamin E treatments. 3. Plasma alpha-tocopherol (AT) concentrations in treatments 2, 4 and 5 were similar, and markedly higher than those in treatments 1 and 3, while those of treatment 3 were significantly (P less than 0.001) higher than those of treatment 1. Plasma retinol concentrations were not significantly (P greater than 0.05) affected by the vitamin E treatments. 4. TBA values of the meat were very low and not significantly affected by the vitamin E treatments. However, after incubation the TBA values were highly significantly (P less than 0.01) negatively correlated with the amount of vitamin E consumed during the experiment. The stability of meat of birds fed the various combinations of vitamin E (treatments 3, 4 and 5) was significantly (P less than 0.05) higher than that of birds which did not receive additional vitamin E (treatment 1), but it was significantly (P less than 0.001) lower than that of birds which received vitamin E continuously (treatment 2). 5. It is concluded that a high concentration of vitamin E fed during 0 to 3 weeks of age may significantly improve AT status of the broiler chick up to 7 weeks of age.

Characterization of growth and development of male British United turkeys.

Body weight and the size of various organs (tibia, pectoral muscle, leg muscle, liver, spleen, and testes) were monitored in growing male turkeys (British United Turkeys) in an effort to characterize their growth pattern. The results were fitted with either a single- or a double-component Gompertz equation, describing single and diphasic growth patterns, respectively, using an iterative nonlinear estimation algorithm. The diphasic model with an early and a late growth component provided a better description of the body weight function than the single-phase model. The start of sexual maturation, evidenced by testicular development, marked the transition age between the early and the late phases of growth. A single-component Gompertz equation was sufficient to describe growth of various individual organs. Growth of bone and liver appeared to follow the early growth component, whereas the path of muscle development appeared to be closer to the later growth component. The results suggest that the diphasic growth behavior of male turkeys is caused by a differential growth rate of various organs, rather than by a periodicity in the overall growth rate.

Skin tearing in broilers in relation to skin collagen: effect of sex, strain, and diet.

The relationship between skin tearing and collagen in broilers was investigated in two trials in which strain and sex, and strain and diet served as factorial-arranged variables, respectively. In the first trial, males and females of three strains were examined. Both skin tearing and skin collagen were significantly influenced by strain and sex without any significant strain by sex interaction. Skin collagen, expressed as a fraction of fresh skin protein (N x 6.25) was lower and skin tearing was higher in females than in males, particularly in the most susceptible strain. In the second trial, the effects of supplementary protein or methionine and of a low-density diet were tested in females of two strains that differed in their susceptibility to skin tearing. High dietary protein reduced skin tearing and increased skin collagen. The significant diet by strain interaction resulted from the more pronounced response of the susceptible strain. Neither supplementary methionine nor feeding of low-dietary-density diet significantly affected skin tearing or skin collagen.