Biomedical subjects

I Plavnik

Publications and source records attributed to I Plavnik.

At least 19 recordsLinked to original sources

PubMed2003

Performance and bone development in broiler chickens given 25-hydroxycholecalciferol.

1. A series of 5 trials was conducted with Cobb chickens in order to determine the effect of 25-hydroxycholecalciferol (25OHD3) on their performance and bone development under adequate Calcium (Ca) and Phosphorus (P) supplementation, and under moderate dietary restriction of Ca and P. Formulated beadlets of 25OHD3, trade name HY-D (IsoGen, Naperville, IL, USA) were used as the 25OHD3 source. 2. Five to 10 microg of cholecalciferol (vitamin D3) or 25OHD3/kg diet were sufficient to ensure normal body weight (BW) and bone ash in chickens under continuous lighting. The two materials had similar effects on BW and bone ash. 3. In one out of the three experiments, 25OHD3 increased BW and BW gain, while in the others it had a similar effect to that of vitamin D3, or even a slight negative effect in a trial conducted on the floor, in which the diets were supplemented with the D sources at 75 microg/kg. The effects of both D sources on bone ash and on the severity or frequency of tibial dischondroplasia were similar. 4. 25OHD3 restrained the effect of moderate dietary P restriction, but not of Ca restriction, on BW gain and bone ash in 22-d-old chickens. This effect could not be explained by an higher P bioavailability in the 25OHD3-fed chickens.

Animal Feed↗

PubMed2003

The effect of dietary fibre on the small intestines and apparent digestion in the turkey.

1. In order to determine the feasibility of using high fibre diets in turkey rations, three crude fibre dietary concentrations were fed to turkey hens at three ages and performance, fibre digestibility and small intestinal morphology were determined. 2. Growth rate and feed efficiency decreased when diets contained 80 to 90 g crude fibre/kg; however, growth did not change when 60 g crude fibre/kg was fed between 1 and 4 weeks or between 6 and 8 weeks and was enhanced between 11 and 14 weeks of age. 3. Digestibilities of crude protein, fat and gross energy (GE) were depressed at fibre intakes of 80 to 90 g/kg between 1 and 4 weeks but not at later ages. Crude fibre digestibility increased with age and decreased with dietary fibre content. 4. Total small intestinal length and surface area were increased by high dietary crude fibre intake between 11 and 14 weeks. Small but inconsistent changes in the length, diameter and number of villi, villus size and area were observed in the duodenum, jejunum and ileum at the different ages as a result of feeding the different crude fibre concentrations. 5. Crude fibre can be utilised to some extent by turkeys and concentrations of 60 g fibre/kg in the diet did not result in decreased performance after 6 weeks of age.

Aging↗

PubMed2002

Interactions between dietary crude protein and essential amino acid intake on performance in broilers.

1. The effect of diets with increasing concentrations of crude protein at either fixed essential amino acid concentrations or at fixed essential amino acid:dietary crude protein ratios on performance was examined in 1- to 4-week-old male Cobb chicks. Increasing crude protein intakes at constant essential amino acid concentrations was carried out at two dietary energy contents. 2. Increasing crude protein resulted in a linear decrease in feed intake while weight gain and feed efficiency changed quadratically with a smaller positive effect at the highest crude protein intakes. Feed intake decreased and feed efficiency increased with higher dietary energy and interactions between protein and energy were significant. Abdominal fat content and the efficiency of protein retention decreased with increasing dietary protein intake. 3. Using constant essential amino acid:crude protein ratios at increasing crude protein intakes resulted in (Trial 3) feed intake, weight gain and feed efficiency all increasing before reaching a plateau. Abdominal fat decreased with protein intake and the efficiency of protein retention was quadratic, decreasing at the higher protein intakes. 4. Multiple regression analysis of the results of the three trials indicated that partition of energy intake into maintenance, fat-free tissue growth, fat and the energy required to transform protein intake in excess of retention explained more than 98% of variation. 5. It is proposed that broiler performance at the lower protein intakes was limited by either non-essential amino acid (Trials 1 and 2) or essential amino acid (Trial 3) intake whereas at high protein intakes the decreased efficiency of amino acid utilisation after growth requirements are fulfilled resulted in poorer performance.

Amino Acids, Essential↗

PubMed2000

Effect of age of turkeys on the metabolisable energy of different foodstuffs.

1. True metabolisable energy (TME) of various foodstuffs were determined in turkeys at 3, 9 and 17 weeks of age. 2. TME of soyabean meal did not change with age but TME of wheat and maize was 13% higher in 17-week-old turkeys than in 3- and 9-week-old birds. 3. These differences should be taken into account when formulating diets for turkeys.

Aging↗

PubMed1999

Effect of early-stage thermal conditioning and food restriction on performance and thermotolerance of male broiler chickens.

1. The effects of early-age thermal conditioning and food restriction on performance and thermotolerance were studied in male broiler chickens, in 2 trials. 2. Chickens were exposed to 36 degrees +/- 1 degree C and 70% to 80% relative humidity (RH) for 24 h at the age of 5 d (thermal conditioning, TC), or to food restriction (FR) at the age of 7 to 14 d, or to both treatments (TC+FR), while a control group was reared under standard conditions. At the age of 42 d, chickens were thermally challenged by a heat stress of 350 degrees +/- 1 degree C and 20% to 30% RH for 6 h. 3. In both experiments, weight gain of the TC chickens between the ages of 7 and 42 d was significantly higher than those of other treatments and was associated with higher food intake. 4. Early-age TC significantly increased body temperature (Tb). Thermal challenge at the age of 42 d markedly increased Tb in all groups but that of the TC groups was the lowest. 5. Mortality during thermal challenge was significantly lower in the treated chickens, except for the FR group in trial 2. 6. Plasma triiodothyronine (T3) concentration was greatly depressed in all treatment groups during the thermal challenge. However, the lowest concentration was observed in the TC group, suggesting that these chickens exhibit the lowest rate of heat production under such conditions. 7. Thermal conditioning reduced the increase of haematocrit with age, whereas food restriction resulted in an increase in haematocrit immediately after FR. Thermal challenge resulted in a haematocrit decline in all groups, with the lowest values in the TC and TC+FR chickens. 8. It can be concluded that, because the TC treatment improved thermotolerance (possibly by reducing heat production) and performance, it has advantages over the FR and TC+FR treatments.

Aging↗

PubMed1998

Response of turkeys to relative humidity at high ambient temperature.

1. The effects of relative humidity on growth rate and thermoregulation at high ambient temperature were evaluated in turkeys. Male turkeys were exposed to ambient temperature (Ta) of 35 degrees C and relative humidity (RH) of 40% to 75% and 50% to 85%, at ages of 13 to 19 weeks (trial 1) and 10 to 15 weeks (trial 2), respectively. 2. Body weight and food intake in both trials increased as RH increased up to 70% to 75%. When RH increased further to 80% to 85% (Trial 2) both body weight and food intake declined significantly. 3. Blood CO2 partial pressure (pCO2) did not change significantly at different RHs (trial 1). However, in trial 2 it dropped significantly at 80% to 85% RH. This response coincided with an increase in blood pH. 4. The effect of RH on body temperature (Tb) was not significant in either trial. 5. Triiodothyronine (T3) concentrations increased with the increase in RH up to 70% to 75% RH (trials 1 and 2). A significant decrease was observed when RH was further increased to 80% to 85% RH (Trial 2). Positive linear correlations between T3 and food intake or weight gain were observed in both trials. 6. The results indicate that turkeys can thermoregulate efficiently in the face of extreme changes in RH and that only at high RH (above 75%) did the performance of turkeys deteriorate.

Aging↗

PubMed1998

The response of laying hens to induced molt as affected by strain and age.

Molt was induced in 502-d-old Lohmann, Hy-Line W-77, Yafa, and Yarkon strains of laying hens (Experiment 1), and at different ages during the 1st yr of production in the Lohmann strain (Experiment 2). The induced molt treatment included an 8-d feed withdrawal period followed by a 22-d rest period during which the birds received 60 or 70 g/d of a low-nutrient maintenance diet, in both experiments, respectively, and a reduced duration of daylight. In both experiments, induced molt resulted in an increase in postmolt egg production rate and a diminution of the rate of decline of production with age. The first eggs during the postmolt period were smaller than those of the unmolted birds but egg size increased rapidly to control levels. Egg breakage was markedly reduced by induced molt and its rate of increase with age was diminished. Postmolt feed intake was higher than that of the unmolted birds and body weights reached values higher than those of the controls. Those responses were not different among strains but the ranking among the strains in the molted group was similar to that of the unmolted controls, for all production traits. The postmolt rate of production approached that of first cycle peak and was not affected by treatment age. Shell quality as reflected by the percentage of breakage during the postmolt period was similar to that of the unmolted controls approximately 3 to 4 mo earlier.

Aging↗

PubMed1998

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.

Aging↗

PubMed1998

The effect of dietary protein level on the lysine and arginine requirements of growing chickens.

Comparisons were made of the growth and carcass fat responses to dietary lysine and of the lysine requirements of 1-wk-old broiler chickens receiving diets containing either 18, 20, 23 or 25% protein. Similar comparisons were made of the responses elicited by dietary arginine in diets containing 18 or 23% dietary protein. The responses to lysine supplementation and the lysine requirements of chicks receiving 23 or 25% protein diets were similar. In comparing the 18 or 20% to the 23% protein diet, the initial responses of growth and feed efficiency to dietary lysine were augmented, but the maximal weight gain diminished as dietary protein decreased, leading to a decrease in the lysine requirements. The amounts of extractable carcass fat or abdominal fat pad increased as dietary protein was lowered and, in general, were reduced either by lysine or arginine supplementation. Percentage of pectoral muscle increased slightly with dietary arginine and protein supplementation. The results suggest that when total dietary amino acid level is reduced, the requirements for the individual amino acid decrease due to growth retardation resulting from single or multiple amino acid deficiencies. Single amino acid supplementation of low protein diet is more effective in improving the amino acid balance than supplementation of high protein diets, resulting in a further decrease in the requirements.

Animal Nutritional Physiological Phenomena↗

PubMed1998

Research notes: Effect of environmental temperature on broiler chickens subjected to growth restriction at an early age.

An experiment was carried out to evaluate the effect of early growth restriction (EGR) induced by feed restriction on the ability of male broiler chickens to withstand exposure to high environmental temperatures. A 2 x 4 factorial arrangement of treatments was employed to determine whether such an exposure affects the beneficial effect of EGR on performance and carcass quality. Chicks consumed feed ad libitum or were feed-restricted from 6 to 12 d of age (to achieve 60% growth of the ad libitum birds). From 4 to 8 wk of age, the chickens were kept in temperature-controlled chambers at 25, 30, 35 C and a diurnal cyclic temperature of 25:35 C. Weight gain, feed intake, and feed efficiency from 6 to 8 wk of age (after acclimatization to the various temperatures) and BW at 8 wk of age were significantly (P < or = 0.05) depressed by the high temperatures (35 and 25:35 C) compared with values observed at 25 and 30 C. Early growth restriction did not affect these variables. Relative heart, liver, and breast meat weights at 8 wk of age were decreased significantly with increasing temperature. Relative liver weight was also decreased significantly in the EGR chicks, whereas breast yield was increased significantly in these birds. Relative abdominal fat pad size was not affected by increasing the temperature from 25 to 35 C, but it was significantly lower in chickens kept at 25:35 C than in those kept at 25 and 35 C. Early growth restriction significantly reduced the size of abdominal fat. Because no significant interactions between EGR and ambient temperature on the above mentioned variables were observed during 4 to 8 wk of age, it is concluded that EGR can not alleviate the adverse effect of high ambient temperature on performance, nor can high ambient temperature obliterate the beneficial effect of EGR in improving feed efficiency and reducing fattening.

Acclimatization↗

PubMed1997

Blood system response of chickens to changes in environmental temperature.

Hemodynamic changes were studied in broiler chickens during exposure to constant temperatures (10 to 35 C) or diurnal temperature cycles (10:30 C and 15:35 C), and during acute heat or cold. Packed cell volume (PCV) was significantly high at low constant temperatures (10 and 15 C), whereas at high temperatures (30 and 35 C) plasma volume (PV) was significantly high. A linear relationship between hematocrit and heart weight was observed and indicates an adaptation of heart mass to changes in cardiac output and hematocrit to meet the demands of increased basal metabolic rate. Only during the diurnal temperature cycle of 15:35 C did a significant increase in PV occur when ambient temperature (Ta) was raised form 15 to 35 C. Acute exposure of chickens to high temperature did not affect PV or PCV, but resulted in hyperthermia (44.7 +/- 0.4 C). Changes in PCV are probably related to modulation of the supply of oxygen to accommodate changes in heat production. The significant hypervolemia observed at high temperatures could occur to provide the fluid needed for heat dissipation by panting. The lack of response of the blood system to acute temperature changes may be at least partially responsible for the chickens' failure to control body temperature.

Acclimatization↗

PubMed1997

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.

Adipose Tissue↗

PubMed1997

The response of broiler chickens and turkey poults to steam-pelleted diets supplemented with fat or carbohydrates.

The responses of growth and feed efficiency to pelleted feed was investigated in 4- to 7-wk-old broiler chickens, and in 8- to 12- and 16- to 20-wk-old turkeys. In all cases, the growth and feed efficiency responses were linear within the ranges of dietary energy tested. When energy was added by carbohydrate supplementation, weight gain and feed efficiency responses were parallel for both mash and pellets, but due to the growth response to pellets, the elevation was higher for pellets than for mash. When energy was added by fat, the growth response to pellets also resulted in an increase in function elevation but the slope of the response was lower than in mash feeding, possibly due to a decline in pellet quality as dietary fat increased. Grinding of pellets completely abolished the growth and feed efficiency responses observed when the physical form was preserved. In chickens, comparisons of ground pellets to mash suggested some decline in nutritional quality due to the process of pelleting when either carbohydrates or fat were increased in the diets. In both chickens and turkeys, the feeding of pelleted diets resulted in an increase in abdominal fat.

Animal Feed↗

PubMed1996

Effects of diurnally cycling versus constant temperatures on chicken growth and food intake.

1. Male broiler chickens were exposed in separate experiments to: (a) constant ambient temperatures (Ta) ranging between 10 and 35 degrees C; (b) 12 h:l2 h diurnal high-low temperature of 10:30 degrees C, 15:35 degrees C and 15:30 degrees C in different trials; and (c) 12 h of 30 or 35 degrees C and 12 h of variable lower temperature. 2. A progressive decline in weight gain and food intake was obtained as Ta increased from 18 to 35 degrees C. Under diurnally cycling temperature, weight gain and food intake were lower than in the average corresponding constant temperature, with the exception of chickens exposed to 15 : 30 degrees C, where weight gain and food intake were not significantly different from those of the constant average temperature. 3. As the diurnal cold period was made colder, chickens exposed during half of the diurnal cycle to high temperature (30, 35 degrees C) demonstrated a significant (P <= 0.05) increase in weight gain and food intake. 4. There was a good correlation between plasma triiodothyronine (T3) and Ta. The correlation between T3 and food intake was highly significant, but that between T3 and weight gain was poor. 5. The results indicate the difficulties in predicting the performance of broilers exposed to diurnally cycling temperatures from knowledge of the average temperature.

Adipose Tissue↗

PubMed1995

Calcium metabolism and requirements of chickens are affected by growth.

The interaction between growth and calcium homeostasis was studied by comparing the responses of (a) fast-growing broiler chickens (Cobb) and slow-growing Leghorns, and (b) fast-growing chickens (Cobb) fed either high energy (12.13 kJ/g) or low energy (9.2 kJ/g) diets, to dietary calcium concentration ranging between 4 and 20 g/kg). Plasma calcium increased as dietary calcium increased, reaching an apparent plateau between 0.8 and 1.5% dietary calcium, regardless of basal growth rate. Dietary calcium levels of 1.5% and higher induced hypercalcemia and hypophosphatemia in fast- but not in slow-growing chickens. Weight gain was unaffected by dietary calcium in the slow-growing Leghorns, but followed a bell-shaped response pattern in the fast-growing Cobb chickens. Growth inhibition by feeding of low energy diets changed the response pattern from a quadratic form to that of an increase towards a plateau. The response of bone ash to dietary calcium was characterized as quadratic in fast-growing chicks, changing to a pattern of increase towards a plateau in slow-growing chicks. Intestinal calbindin was suppressed by dietary calcium and was higher in the fast-growing than in the slow-growing chicks. An increase in dietary phosphorus resulted in a shift in the response curves of weight gain and bone ash and an increase in the calcium requirements. The results indicate that the response of chicks to dietary calcium and calcium requirements is markedly modified by growth rate.

Analysis of Variance↗

PubMed1995

Responses of laying hens to forced molt procedures of variable length with or without light restriction.

The importance of the length of the rest period and of photoperiod as components of the forced molt procedures was evaluated in 650- and 560-d-old Lohman hens. The procedure included an 8-d feed withdrawal phase and rest periods varying from 0 to 35 d, during which the birds were fed for maintenance only. In the first trial, forced molt was applied with or without omission of artificial illumination. The rest period varied between 2 and 20 d. In the second trial, all treatments included omission of artificial illumination, and a variable rest period between 0 and 35 d. Egg production ceased, after 4 to 5 d of feed withdrawal and resumed 8 to 15 d after the end of the rest period, without any consistent response to its length. Forced molt stimulated egg production rate and diminished its age-dependent rate of decline, reduced the proportion of broken and shell-less eggs, and improved shell quality. Following wide oscillations proportional to the length of the rest period, egg weight stabilized at levels similar to that of the unmolted controls. Feed intake was stimulated by forced molt to levels exceeding those of the control hens. Body weight increased during the postmolt period to levels slightly exceeding those of unmolted controls. Results of one trial show that omission of artificial illumination was essential for the full expression of the molt responses. In the other trial, production rate and shell quality were improved and the percentage of broken eggs was reduced when the length of the rest period was increased. Maximal improvements appears to have been reached with rests period of 14 to 21 d.

Animals↗

PubMed1992

Tibia development in turkeys and chickens as affected by early-age feed restriction.

Tibia development was studied by histomorphometry in male chickens and turkeys fed ad libitum throughout the growing period, or subjected to an early-age (1-week) severe feed restriction for 6 and 14 days, respectively. In turkeys, the rates of longitudinal bone growth and epiphyseal width growth, both dependent on the activity of chondrocytes, proceeded rapidly and reached maxima at early ages of 24 and 11 days, respectively. Moreover, longitudinal bone growth and the growth of epiphyseal width were reduced during early-age feed restriction, in both chickens and turkeys. On the other hand, the rate of growth of metaphyseal width, determined by activity of bone cells such as osteoclasts and osteoblasts, reached in turkeys a maximum at the relatively late age of 70 days, and was not influenced by feed restriction. Rhythmic variation characterized the temporal behavior of the height of the hypertrophic and non-hypertrophic zones of the growth plate, the trabecular width, and the osteoclasts number at the subchondral region. Rhythmicity appeared similar in both ad libitum-fed and early-age feed-restricted birds of both species. The height of the non-hypertrophic epiphyseal cartilage appeared not to change, whereas the hypertrophic zone decreased with age and early-age feed restriction, demonstrating the importance of cartilage cell hypertrophy as a main determinant of longitudinal bone growth. Sexual maturation was accompanied by the disappearance of both hypertrophic and non-hypertrophic zones of the epiphyseal growth plate and the end of bone elongation. Trabecular width at the end of bone elongation. Trabecular width at the subchondral region increased while osteoclast number decreased with age, reflecting the net increase in bone mass, but were not affected significantly by early age feed restriction. Compensatory growth of the early-age feed-restricted birds, resulted in the complete recovery of affected bone variables within a few weeks of resumed ad libitum feed intake.

Aging↗

PubMed1991

Response of broiler chickens and turkey poults to food restriction of varied severity during early life.

1. Cobb male (7-d-old) and female (6-d-old) chicks and BUT male and female turkeys (7-d-old), were subjected to food restriction of varying severity for 7, 5, 10 and 7d, respectively. 2. The energy allowance was calculated to support from 0% to 75% of the growth rate typical of species, strain and sex. 3. In male and female broilers kept up to 56 and 50 d, respectively, a high rate of weight gain after the restriction period (refeeding period) overcame the growth retardation attributable to restriction, except in the birds which had been subjected to the most severe regimen. In the mildest regiments, body weights reached slightly higher values than those of the ad libitum-fed controls. Overall food conversion efficiency was significantly improved in males and abdominal fat content was reduced in both sexes, regardless of the severity of restriction. 4. Body weights of male and female turkeys, aged 147 and 112 d respectively, of the groups subjected to the milder (75% growth) restriction, significantly exceeded those of the controls. Food conversion efficiency and meat yield were improved by early-age food restriction but carcase fat was not affected. 5. The results for both species of either sex suggest that a mild food restriction applied at an age of about 1 week and allowing for 60 to 75% of normal growth, may offer an economic advantage over a continuous ad libitum feeding regimen.

Animal Feed↗