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Biomedical subjects

I Plavnik

Publications and source records attributed to I Plavnik.

At least 37 records · Page 2Linked to original sources
PubMed1991

Increased skin tearing in broilers and reduced collagen synthesis in skin in vivo and in vitro in response to the coccidiostat halofuginone.

In vivo and in vitro experiments were conducted in an effort to elucidate the mechanism of suppression by halofuginone of skin strength in broilers. In the in vivo study, halofuginone was included at concentrations of 0, 1.5, 3, and 6 mg/kg of diet, corresponding to 0, 50, 100, and 200%, respectively, of the amount recommended for use as a coccidiostat. Each dietary treatment was given to 260 female broiler day-old chickens. Skin tearing was evaluated at the processing plant. Skin collagen and Kjeldahl-nitrogen were determined chemically. At the age of 7 wk, BW and feed efficiency were affected only in birds consuming the diet containing the highest concentration of the drug. Skin tearing increased but skin collagen concentration decreased in a dose-dependent manner. Fibroblasts were obtained by collagenase digestion from chicken skin and cultured. The cultured cells were incubated with various concentrations of halofuginone, monensin, and nicarbazin, and [3H]proline incorporation was evaluated in collagenase-digestible (representing mostly collagen) and nondigestible proteins exported by the cells into the medium. Halofuginone, at a concentration as low as 10(-11) M, inhibited incorporation of [3H]proline into collagenase-digestible proteins, but did not affect incorporation of [3H]proline into collagenase-nondigestible proteins. Even at concentrations as high as 10(-9) M, neither monensin nor nicarbazin affected collagenase-digestible proteins. The in vitro results suggest that halofuginone specifically inhibits collagen synthesis by skin fibroblasts. Results of both in vivo and in vitro trials suggest that the increase of skin tearing during processing, induced by halofuginone, is caused by direct suppression of skin collagen synthesis.

Animals↗
PubMed1991

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.

Animals↗
PubMed1991

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.

Animals↗
PubMed1989

Severe feed restriction in pullets during the early growing period: performance and relationships among age, body weight, and egg weight at the onset of production.

The performance of egg type (Leghorn x Rhode Island Red) chickens that were feed restricted during the prelaying period was studied in two trials, each conducted with 300 hens. In Trial 1, treatments included 1) an ad libitum-fed control; 2) restriction for close to zero growth between 7 and 28 days of age; 3) the same restriction as (2) but continued by restriction of 50% growth up to 70 days; 4) restriction between 7 and 70 days for 50% growth; and 5) restriction for 50% growth between 7 and 98 days. In Trial 2, birds were restricted severely (close to zero growth) from 7 to 28 days of age, followed by restriction of 50% growth up to 28, 56, 84, and 112 days of age, respectively. In all cases, feed restriction resulted in a delay in the onset of egg production, leading to some increases in egg weight. Egg production rate and cumulative production were not affected, in most cases, by early feed restriction. The BW at the onset and after 20 mo of production was reduced when feed restriction was continued beyond the age of 84 days. Overall feed conversion (grams feed per egg) and feed efficiency (grams feed per gram egg mass) were not affected significantly by feed restriction, although feed efficiency (grams gain per gram feed) was improved during the prelaying period. Within each treatment, BW was positively correlated with age at onset of egg production. Egg weight was a function of both age and BW at the onset of production. The significant correlation between egg weight and BW was maintained even after a year of production.

Age Factors↗
PubMed1989

Effect of dietary protein, energy, and feed pelleting on the response of chicks to early feed restriction.

In three trials, male broiler chicks were subjected to a 6-day feed restriction regimen designed to retard growth severely. In one trial, the amino acid requirements during refeeding were evaluated by testing the adequacy of diets based on model calculations. In two additional trials, the response of feed-restricted birds to increased dietary energy density and to feed pelleting was compared with that of birds fed ad libitum. Results of the first trial showed that weight gain and feed efficiency during the first 2 wk of refeeding were reduced when the diet contained less than the model-calculated protein level for this period. No improvement in performance could be obtained when dietary protein was increased by 1% above model-calculated requirements. An increase in dietary nutrient density resulted in an enhanced growth rate. Feed efficiency was improved by an increase in nutrient density and by early feed restriction with no significant feed restriction x diet density interactions. Pellet-feeding resulted in improved growth without affecting feed efficiency, whereas feed restriction resulted in improved feed efficiency only. Interaction between pelleting and feed restriction was not significant for any of the variables. In all three trials, abdominal fat was reduced by feed restriction without any interaction with energy, protein, or dietary form. The results suggest that the requirements for some amino acid increase after feed restriction and that feed consumption does not limit the accelerated growth response at that time.

Animal Feed↗
PubMed1988

Effect of early feed restriction in male broiler chicks on plasma metabolic hormones during feed restriction and accelerated growth.

1. Plasma GH was greater (P less than 0.05) on day 12 in ad libitum-fed birds compared to restricted chicks. Conversely, maximum GH levels were found to occur in the nutrient restricted chicks during the period of accelerated growth (day 42). 2. A significant decline in circulating insulin concentrations with advancing age was evident in both ad libitum-fed and restricted chicks. 3. Feed restriction significantly suppressed circulating T3 in restricted chicks, with concentrations returning to control levels upon refeeding. 4. A significant increase in T4 with advancing age was evident in both treatment groups, with T4 being significantly greater in controls compared to restricted chicks at 54 days of age.

Age Factors↗
PubMed1988

Early feed restriction in chicks: effect of age, duration, and sex.

Several regimens of feed restriction, calculated to support the maintenance of body weight without any allowance for growth, were applied beginning at the ages of 3 to 11 days for periods of 3 to 7 days using male and female broilers. In males, the 7-day feed restriction treatment resulted in improved feed efficiency on an age basis, or on a body weight basis after body weight had reached .7 to 1 kg. Feed restriction also resulted in a reduction in the amount of abdominal fat at the age of 54 to 59 days without any concomitant reduction in body weight. Within the range tested, 3 to 11 days of age, the initiation of the 7-day restriction treatment did not affect response. Similar responses were obtained in females, but with little benefit in feed efficiency when compared with ad libitum-fed birds on a body-weight basis. Also in females, reduction in 56-day body weight and loss of benefits derived from improved feed efficiency and reduced carcass fat could be avoided if the period of restriction was kept at 3 to 5 days.

Age Factors↗
PubMed1988

Response of growing turkeys to dietary fat.

Growth, feed efficiency, and carcass fat were evaluated in turkeys fed diets in which added fat varied, holding energy or the calories:protein ratio constant. In the 1 to 3-wk-old turkey, growth and feed efficiency increased with dietary energy, but did not change significantly when fat was added isocalorically. The 12 to 14-wk-old turkey responded with improved growth and feed efficiency when dietary fat was added either isocalorically or with increasing energy density. However, the response to the isocaloric fat addition was smaller in magnitude than the response when fat was added without calorie adjustment. No difference could be detected in 12 to 15-wk-old turkeys in the performance response to tallow and soybean oil. Carcass fat deposition generally increased with dietary fat supplementation, regardless of the caloric change. The results suggest that in the midterm of development of the growing turkey, dietary fat per se affects growth, feed efficiency, and carcass fat. Growth and feed efficiency responses to nutrient density occur in both young and older birds.

Adipose Tissue↗
PubMed1987

Differential responses to dietary carbohydrates and fat of turkeys kept at various environmental temperatures.

Interactions between environmental temperature and dietary energy sources were evaluated in 6 to 9-wk and 9 to 12-wk-old turkeys using weight gain, feed efficiency, and carcass fat as response criteria. The dietary variables (soybean oil or glucose) were added in five or six increments at the expense of each other or of the fiber supplements, keeping the minima for protein and amino acid/energy constant. The resulting diets were fed to birds kept at 10 and 27 C. Duplicate experiments were conducted for each mode of dietary variable addition. Parallel increases in body weight gain and feed efficiency were obtained at the two temperatures when fat replaced carbohydrates or fiber, thereby raising dietary energy density. Some responses of weight gain and feed efficiency at the two temperatures were obtained also with a graded isocaloric addition of fat but the response was significant only at 27 C and not at 10 C. A greater response of gain and feed efficiency to energy supplied by dietary glucose was obtained at 10 C as compared with 27 C. Dietary fat supplementation resulted in increased deposition of carcass fat when given together with energy or isocalorically regardless of environmental temperature. Carcass fat was increased by glucose-energy at the low temperature only.

Adipose Tissue↗
PubMed1986

Carcass minerals in chickens (Gallus domesticus) during growth.

Moisture, sodium, potassium, calcium, phosphate and magnesium were determined in the carcass of male chickens (Gallus domesticus) between the ages of 1 and 70 days. Moisture decreased rapidly during the first 3 days of life, followed by a more moderate decline. Sodium and potassium concentrations decreased with age, but not in a parallel fashion. Some of the changes with age could be explained on the basis of an extra- and intracellular fluid shifts. Calcium and phosphate concentration increased with age, reflecting skeletal calcification. Carcass magnesium concentration increased during the first 3 days of life and did not change significantly thereafter.

Aging↗
PubMed1986

Effects of early feed restriction in broilers. I. Growth performance and carcass composition.

The effect of severe nutrient restriction at an early age was investigated in male and female broilers. At day 5 (females) or day 6 (males) post-hatching, chicks on limited intake were provided only enough feed (starter diet) to meet daily maintenance energy requirements only. Restriction was carried out for either 6 or 12 days, after which refeeding was on an ad libitum basis. Ad libitum fed controls were included. Minimal weight gain was noted during the period of restriction. Two weeks following refeeding, weight gains in the treated chicks exceeded that of controls. Final body weights (8 weeks) of 6-day-restricted chicks was slightly greater than controls, whereas 12-day-restricted chicks were significantly lower. Limiting nutrient intake at an early age resulted in better feed efficiency accompanied by less carcass fat and smaller abdominal fat pads. A similar, though not as dramatic effect was observed in female broilers. Results of early feed restriction on broiler growth patterns suggest that significant improvements in feed efficiency can be attained along with a reduction in total body fat.

Adipose Tissue↗
PubMed1986

Effect of early feed restriction in broilers. II. Lipid metabolism.

Three experiments were conducted with broiler chicks to evaluate the effect of dietary energy restrictions on in vitro lipid metabolism. In Experiment 1, chicks were restricted from either 6 to 12 or 6 to 18 days of age and then fed ad libitum until day 27. In Experiment 2, both male and female chicks were restricted from 5 to 11 days of age and then were refed until 27 or 54 days of age. Glutamic:oxaloacetic aminotransferase (GOT), isocitrate dehydrogenase (ICD), malic enzyme (ME) and the fatty acid synthetase complex (FAS) were assayed at 27 days (Experiment 1) and at 27 and 54 days (Experiment 2). In Experiment 3, male chicks were restricted from days 6 to 12 and then were refed until day 27. In vitro lipogenesis and enzyme activities were determined during the 12 to 18-day period as the chicks were refed following the restriction. Both restriction regimes decreased (P less than .05) ME and FAS at the conclusion of the respective restriction intervals (Experiments 1 & 2). The 6 to 12-day restriction decreased (P less than .05) in vitro lipogenesis in the 12 day old chick when compared to controls. When restricted chicks were refed, in vitro lipogenesis exceeded that of the controls at both 14 and 16 days, but was less than that of the controls at 27 days.

Adipose Tissue↗
PubMed1984

Body weight and/or fatness as potential determinants of the onset of egg production in broiler breeder hens.

In four trials during consecutive years individually-caged birds were weighed at first egg, and in the first two trials they were then killed to determine abdominal and skin fat, in order to establish whether there is a minimal body weight and/or body fat pool required for the start of egg production in broiler breeder hens. There were negative correlations ranging from significant to negligible between body weight and age at first egg. For birds of the same strain on a conventional food restriction regimen, the average weight range at first egg in the four trials was 3.3 to 3.7 kg, which may be a strain characteristic. In spite of severe food restriction, all birds were very fat at first egg. The correlations between fat concentration and age at first egg were negative. In mature pullets a minimum concentration of stored, easily mobilised fat may be essential for yolk formation and ovulation.

Adipose Tissue↗
PubMed1983

Handling of water and dietary monovalent ions by the young turkey.

Sodium and water turnover rates were measured in young turkeys fed diets with three concentrations of NaCl and kept at 12, 18 or 30 degrees C. Sodium absorption averaged approximately 60% and was unaffected by temperature. Water and sodium pools were affected by temperature and sodium intake. Water turnover was linear to sodium turnover at the lower two temperatures. No significant relationship was apparent in birds kept at 30 degrees C. The reciprocal of the slope of the function of water turnover on sodium turnover was 125-170 mM, suggesting an increase in isotonic urine excretion with sodium intake and a corresponding increase in water intake. Dietary sodium and potassium stimulated water turnover similarly. Dietary chloride concentration did not affect water turnover. In the turkey plasma pH and pCO2 were unaffected by a wide range of the anion-cation balance. It is concluded that excess sodium or potassium intakes is handled effectively in the turkey by increased water intake and excretion.

Animals↗
PubMed1983

The amino acid requirements of growing turkeys. 2. Experimental validation of model-calculated requirements for sulfur amino acids and lysine.

The response to protein and the requirements for sulfur amino acids and lysine have been evaluated in male turkeys throughout the growth period as an experimental validation of model-calculated requirements (Hurwitz et al., 1983). The sulfur amino acid requirements were 3.4 and 3.1 mg/kcal for 1- and 5-week-old turkeys, respectively. The requirements for lysine were 4.8, 2.7, and 2.2 mg/kcal for 1-, 12-, and 16-week-old turkeys, respectively, which were in close agreement with the model predictions. Dietary protein in diets calculated on the basis of the model was sufficient to maintain maximal growth and feed efficiency. The results were the basis for accepting the general validity of the model-calculated requirements (Hurwitz et al., 1983).

Aging↗
PubMed1982

Evaluation of methanol-grown bacteria and hydrocarbon-grown yeast as sources of protein for poultry: trials with laying birds.

1. Two 90-d trials were carried out with laying hens at peak production, for the evaluation of two single-cell protein (SCP) sources in practical-type layer diets of relatively low protein content. The SCP tested were: Pruteen, produced from methanol-utilising bacteria, and a Lavera-type yeast which utilises the normal paraffins of heavy gas oil. 2. In one trial the inclusion of 50 g yeast/kg diet had little effect on performance. Pruteen at the same concentration decreased production rate and egg size due to a significant reduction in food consumption (5%), but did not affect food utilisation. 3. In another trial diets containing 60 and 100 g Pruteen/kg had similar, non-significant depressive effects on production rate (about 8%), without affecting food intake, egg size or body weight. 4. The relatively low arginine concentration in Pruteen necessitated increasing the dietary protein content in order to meet the calculated requirements. 5. A 17-carbon fatty acid was introduced at low concentration into the diet by the inclusion of 100 g Pruteen/kg; only traces of it could be detected in the yolk lipids of eggs laid by hens fed on this diet.

Animals↗