Biomedical subjects

G M Pesti

Publications and source records attributed to G M Pesti.

At least 91 records · Page 5Linked to original sources

PubMed1987

Comparison of three nonlinear regression models for describing broiler growth curves.

Three general growth models (Logistics, Gompertz and Saturation Kinetics) were compared for describing growth of broilers. Accuracy of fit, case of use and interpretation of data were used to compare the models. Data from a broiler feed restriction study was used to illustrate the parameter differences between the models. All three models accurately described the growth of the birds from the different experimental treatments based on coefficients of determination greater than or equal to .966. The Saturation Kinetics model proved to be the least accurate based on examination of residual values but still had a high association to the actual data. Linear regression applied to short intervals of the growth curve also proved to be an accurate means of interpreting growth rates.

Animals↗

PubMed1986

Expressing the variability in results of metabolizable energy assays.

In estimating the metabolizable energy of a food or feedstuff (MEf), the ME of a reference diet (MEr, containing glucose monohydrate) and the ME of a test (MEt, containing the feedstuff substituted for glucose) are determined from a feeding trial: MEf = MEglucose -1/P (MEr - MEt) where P is a proportion of substitution. Traditionally, MEr has been used in calculating the variance of MEf as if it were measured without error, leading to an underestimation of the variance in MEf. Variances of MEf estimated by a method based on the variances MEr and MEt were 4-11% greater for sample data. Underestimation of variances can lead to excess confidence in ME estimates. Too few replicates may be used for the desired confidence. Figures depicting the influence of replication and degree of substitution are included to help select the replication and proportion of substitution necessary to achieve acceptable results.

Analysis of Variance↗

PubMed1986

The response of male broiler chicks to a corn-soy diet supplemented with L-methionine, L-cystine, choline, sulfate, and vitamin B12.

Six experiments with male broiler chicks were conducted to study responses to dietary supplements of L-methionine, L-cystine, choline, sulfate, and vitamin B12. A corn-soy-poultry oil-based diet calculated to contain .38% methionine, .74% total sulfur containing amino acids, 23% protein, 3,265 kcal metabolizable energy/kg, and 1.39 mg/g of choline was fed. Analysis indicated an average of .38% Methionine (.35 to .45) .77% Methionine + Cysteine (.72 TO .92), and 1.23 mg choline/g feed (.99 to 1.56) in the basal diet. Chicks fed the basal diets gained an average of 508 g in 21 days and had average feed conversion ratios (FCR) of 1.55. Chicks fed diets supplemented with .2% L-methionine gained significantly more (P less than .05) than those fed the basal diet in each experiment (average gain = 551 g; FCR = 1.44). Chicks fed choline-supplemented diets gained as well as those fed L-methionine in five of six experiments (P greater than .05) (average gain = 541 g; FCR = 1.48). Chicks fed sodium sulfate-supplemented diets gained as well as those fed L-methionine in two of four experiments when adequate sodium was fed (average gain = 536; FCR = 1.50). Chicks fed choline and sulfate supplements together did no better than those fed choline supplements only, with adequate sodium levels in the basal diet. The same basal diet was fed in the last two experiments. In one trial, a response to vitamin B12 was observed; in the other there was no response.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗

PubMed1986

Nutritive value of poultry by-product meal. 1. Metabolizable energy values as influenced by method of determination and level of substitution.

Experiments were conducted to determine the metabolizable energy (MEn) of eight poultry by-product meal (PBPM) samples. Samples averaged 5.44% moisture, 4.84 kcal gross energy (GE)/g dry matter (DM), 61.2% crude protein, 13.38% ether extract, 16.1% ash, 5.14% calcium, and 2.36% phosphorus. Samples of PBPM were substituted in the diet at levels of 20 and 40%. Values of ME were calculated with substitution for the diet (Matterson's method) and for glucose (Hill's method) and by the fasted cockerel method. Values of PBPM MEn were 7.9% greater when substitution was for diet as compared with substitution for glucose; values were 2.95 and 2.74 kcal/g DM, respectively. Using Matterson's method with three samples, MEn values were determined to be 12.1% greater when PBPM was substituted at the rate of 20% than at 40%; values were 3.33 and 2.97 kcal/g DM, respectively. Differences in MEn between the best and poorest samples (3.79 and 2.77 kcal/g DM) could be attributed to differences in gross energy (5.00 and 4.49 kcal/g DM) and percentage of gross energy metabolized (75.7 and 61.7%). Metabolizable energy was more closely related to body weight gains than the amount of feed consumed. When a modification of Sibbald's fasted cockerel technique was used, true MEn of the eight samples averaged 3.35 kcal/g DM and 69% of GE metabolized. For the three samples assayed by both methods, Matterson's method gave values averaging .97% higher than Sibbald's (+4.3, +.8, and -2.2%). Differences in MEn were mostly highly correlated with ash (-.89), calcium (-.85), and GE (.78) contents of the diets. Projections from relationships found between ME and nutrient compositions of these samples to the average sample used by the poultry industry in the Southeast indicate an average of 3.57 kcal ME/g DM of PBPM (3.39 kcal/g as is).

Animal Feed↗

PubMed1986

Nutritive value of poultry by-product meal. 2. Comparisons of methods of determining protein quality.

Studies were conducted to compare several methods of determining the protein quality of poultry by-product meal (PBPM). A sample of PBPM was compared to a soybean meal (SBM) sample fortified with .5% of L-methionine. Each was incorporated into corn starch and poultry oil-based diets at 2.5% increments between 0 and 30% protein. Diets were fed for 7 days starting when the chicks were 8 days old. Slope-ratio and saturation kinetics models were fitted for the two protein sources. Protein efficiency ratio (PER), net protein ratio, and net protein utilization were calculated for each diet. The PER was the most discriminating method of estimating protein quality, especially at lower levels (2.5% protein: PBPM = .65, SBM + methionine (Met) = 4.23). At higher levels, no differences could be detected (30% protein: PBPM = 2.45, SBM + Met = 2.31). The 6% protein level was chosen for further studies because there were large differences in PER, and the chicks were in positive nitrogen balance. For eight samples of PBPM (from three different processing facilities), Kjeldahl N ranged from 8.64 to 10.22% gross energy (GE) from 4.49 to 5.36 kcal/g; Ca from 3.6 to 8.84%, and P from 2.04 to 2.55%. A Monday morning sample (fresh broiler waste) was compared to a Friday afternoon sample from the same processing facility (broiler and hatchery waste, and DAF sludge) in semipurified diets at 6% protein. Significant differences in gain were detected in two experiments, but PER in only one. For the five samples tested by all methods, similar rankings were found by PER, pepsin digestibility, total lysine and Carpenter's available lysine.

Animal Feed↗

PubMed1985

Water consumption of broiler chickens under commercial conditions.

The daily water consumption of twenty-four flocks of commercial broiler chickens was measured (average = 19,757 birds/flock). Broilers were raised in two houses--a conventional, open, automatic side-curtained house and a totally enclosed, power-ventilated house on the same premises. Commercially available strains were used and various feed additives were compared during the trials. Water:feed consumption ratios averaged 1.77 g/g. Water consumption was a linear function of broiler age (R2 greater than .99). It could be predicted by multiplying 5.28 g times the broiler's age (5.1 g for birds slaughtered in the cooler times of the year or 5.7 for those slaughtered in the warmest months). Housing type had no effect on water consumption. Increasing dietary sodium increased water consumption, although its effect could not be clearly discerned statistically from that of female parent genotype. It is suggested that 5.28 ml/bird/day of age is a good method of predicting the water consumption of broiler chickens.

Age Factors↗

PubMed1985

Development of a basal diet to study broiler chicken responses to the sulfur-containing amino acids and sodium sulfate.

Three experiments were conducted to develop a basal diet limiting in the sulfur-containing amino acids and with adequate sodium. Twelve hundred commercial male broiler chicks were grown to 3 weeks of age in battery brooders. Chicks were fed a diet of a corn-soybean meal-poultry oil containing .38% methionine, .74% total sulfur-containing amino acids, and .10% sodium. The first two experiments, pooled for statistical analyses, showed that supplementation with .25% L-methionine significantly increased chick growth over the basal (496 vs. 465 g; P = .034) as did sodium supplementation (518 vs. 465 g; P less than .001). The best growth rate occurred when L-methionine and sodium chloride (NaCl) were supplemented together at .25 and .33%, respectively (579 g gained). The response from NaCl was demonstrated to be due to the sodium and not the chlorine by comparison to responses from potassium chloride (KCl) and sodium carbonate (Na2CO3) supplementation. It is suggested that two "first-limiting" nutrients, methionine and sodium, exist for chicks fed this particular diet. In Experiment 3, a response surface was determined with supplemental sodium (as NaCl) and L-methionine each varying from 0 to .20% (.10 to .30% total sodium and .38 to .58% total methionine). It was concluded that .20% total sodium is adequate to maximize growth and feed efficiency (.20% better than .13%, no different from .27%). Similarly, .17% supplemental methionine (.55% total) appears to be adequate (.17% better than .10%; .20% not better than .17%) with no supplemental choline.

Amino Acids, Sulfur↗

PubMed1984

Influence of substitution method and of food intake on bioassays to determine metabolisable energy with chickens.

Several different methods of assaying the metabolisable energy (ME) of ground maize and a maize and glucose mixture were studied. Over a 24-h period fasted cockerels lost more energy and nitrogen in their excreta than those fed 15 g maize and 15 g glucose monohydrate. Discrepancies in ME values of maize were found between 1) Hill's method (substitution for glucose) and 2) Sibbald's method (the difference between energy ingested and excreted, corrected for endogenous losses by a comparison with fasted controls). These discrepancies were attributed to differences in endogenous energy losses between fed and fasted birds and interactions between the test substance and reference diet. No significant differences could be detected when substitution for glucose was compared to substitution for the entire diet in three experiments. Significant differences in the ME of maize because of the composition of the basal diet were found (semi-purified:practical; 17.20: 14.56 kJ/g; and 50 g/kg added fat: 100 g/kg added fat; 15.94: 16.69 kJ/g). Food intakes equal to 70, 60 or 30% of ad libitum did not affect the ME of maize when the substitution for glucose method was used. It is concluded that basal diets for ME determinations should be carefully selected because of possible interactions between dietary components. When ME is determined by feeding small amounts of the test material, endogenous losses may be over-estimated because the control birds are in a different physiological state (fasted).

Animal Feed↗

PubMed1984

The response of growing broiler chickens to dietary contents of protein, energy and added fat.

The results of 47 experiments with broilers over the period 1974 to 1983 were selected for regression analysis. Included were those dealing with the relationship of growth and food utilisation to content of dietary protein (DP), metabolisable energy (DME) and added fat (DAF) in conventional feedingstuffs. Significant correlations were found between DP and DME (0.50; P less than 0.01), DP and DAF (0.61; P less than 0.01), and DME and DAF (0.65; P less than 0.01) contents. Using multiple regression models, growth and food utilisation efficiency (FUE) were found to be dependent on the linear and quadratic effects of DME (r2 values = 0.67 and 0.64 respectively). Growth and FUE were also dependent on the linear and quadratic effects of DP (r2 values = 0.70 and 0.49 respectively). By including the effects of DME, DP and DAF in the gain and FUE models it was shown that growth and FUE were dependent on DME, DP and DAF (r2 values = 0.76 and 0.79 respectively). It was concluded that hypotheses concerning the broiler's response to DME and DAF were both correct but incomplete. DME, DP and DAF contents must all be known to predict accurately growth and FUE.

Animals↗

PubMed1984

The roles of protein level and diet form in water consumption and abdominal fat pad deposition of broilers.

Two experiments were conducted to investigate the possible relationship of water intake and water/feed ratios in explaining abdominal fat changes associated with changes in dietary protein level and diet form. In Experiment 1, day-old male chicks from two commercial broiler stocks were fed diets containing 26, 22, and 17% protein from 0 to 19 days of age. Chicks fed the 26% protein diet consumed more water, had higher water/feed ratios, and had less abdominal fat than chicks fed lower protein diets. Chicks fed the 22% protein diet were intermediate to the 26 and 17% protein treatments in water consumption, water/feed ratios, and abdominal fat. In Experiment 2, day-old male chicks from two commercial broiler stocks were fed a diet in either mash or crumbled form from 0 to 20 days of age. Chicks fed crumbles had heavier body weights, consumed more feed and water, and had more abdominal fat than birds fed the mash diet. Superior body weights of birds fed the crumbled diet appeared to be due to higher relative growth rates immediately after hatch.

Abdomen↗

PubMed1983

The response of male broiler chickens to diets with various protein and energy contents during the growing phase.

1. In two trials each using 2 400 male broilers, the regression of body weight on the linear effects of dietary protein, energy and age, the quadratic effect of age, and their interactions, accounted for approximately 99% of the observed variation during the growing and finishing period (3 to 8 weeks of age). Increasing either dietary protein or energy content significantly increased body weight. 2. The regression of food consumption on the linear effects of age, protein, energy and protein X energy interaction, and the quadratic effect of age accounted for 94% of the observed variation. The regression of food utilisation on the linear effects of protein, energy, and age and the quadratic effects of dietary protein and age accounted for 97% of the observed variation. Food consumption and efficiency were dependent on both dietary protein and energy, increasing with increases in either dietary protein or energy content. 3. The regression of fat in the dressed carcass on the linear effects of protein, energy and age accounted for 19% of the observed variation. Carcass fat increased with increasing age and dietary energy, and decreased with increasing dietary protein. 4. Although body weight, food consumption and utilisation were significantly different between trials, the proportion of carcass fat was not.

Aging↗

PubMed1983

Antibody response against newcastle disease in commercial broilers fed different dietary protein levels.

A factorial experiment was conducted with two levels of dietary protein (17.5 and 26%) and three vaccination regimens (inactivated oil-emulsion, live LaSota strain, and unvaccinated) against Newcastle disease at 10 days of age. There were two trials with 3 pens of 15 male broiler chicks each per cell. Birds fed the high protein diet grew significantly better (P less than .05) in the second trial (1731 g at 6 weeks vs. 1622 g) but not in the first (1304 vs. 1244 g); no growth differences were noted due to vaccine. At 3 weeks of age, the hemagglutination-inhibition antibody titers from the live vaccine were significantly (P less than .01) higher than from the inactivated vaccine. At 3 weeks of age, antibody titers from the inactivated vaccine were elevated (P less than .05) in birds fed the low protein diet in the second trial. At 6 weeks of age, antibody titers were affected by vaccine (P less than .05) but not by dietary protein. Antibody titer levels were higher from the inactivated vaccine than from the live vaccine in the first trial; these results were reversed in the second trial. Postchallenge results with the Texas GB strain of Newcastle did not reveal any significant differences due to dietary protein content, trial, or type of vaccine.

Animals↗

PubMed1983

The determination of plasma corticosterone of chickens by high pressure liquid chromatography.

A simple method for separating and measuring chicken plasma corticosterone by high pressure liquid chromatography (HPLC) is described. Plasma was extracted twice, first, with isooctane to remove nonpolar steroids and, second, the polar steroids were extracted with dichloromethane. Analytical recovery of added corticosterone was 96.5 +/- 1.9% (mean +/- SE). Interassay variability was less than 8% (coefficient of variation = 7.7%). The assay was specific for corticosterone with the exception of deoxyhydroxycorticosterone, which we do not believe to be in significant amounts in chicken plasma. Comparison of values obtained by the HPLC method to a radioimmunoassay method revealed no significant differences. Advantages of the present method include high specificity, simplicity, and cost. A disadvantage is the relatively large amount of corticosterone (plasma volume) required for detection. The method should be applicable to corticosterone determinations in the plasma of other species as well.

Animals↗

PubMed1983

Effects of population density on the growth, organ weights, and plasma corticosterone of young broiler chicks.

Two trials were conducted with broiler chicks to determine the effects of population density on the growth, feed efficiency, and several physiological parameters associated with stress in birds. Chicks were brooded in batteries at 116, 232, 348, and 697 cm2/chick. Chicks brooded at 348 cm2/chick grew and utilized feed significantly better than those brooded at 697 cm2/chick during the first week. For maximum growth and feed efficiency, 116 cm2/chick was adequate for the first week; 232 cm2/chick was adequate during the second and third weeks. Increasing cage density significantly decreased percentage heart and spleen weights (g/100 g body weight) and plasma corticosterone at 3 weeks.

Animals↗

PubMed1983

Effects of the dwarfing gene (dw) on egg weight, chick weight, and chick weight: egg weight ratio in a commercial broiler strain.

The effects of the dwarfing gene (dw) on egg weight, chick weight, and chick weight: egg weight ratio were studied. Egg weights prior to setting and subsequent chick weights were determined on 1842 chicks from standard-sized broiler dams and 1694 chicks from closely related dwarf dams. Egg weight means were 67.3 and 63.0 g for standard and dwarf dams, respectively. Chick weights expressed as percentage of egg weight were 68.4 and 67.3% for standard and dwarf dam chicks, respectively. Both egg weight and chick weight: egg weight ratio differences were highly significant (P less than .01). Percent hatch weights of male and female chicks, 68.0 and 67.7%, respectively, were also significantly different (P less than .05). Regression analysis of egg weight on chick weight estimated the overall equation: chick weight = -6.13 g + .78 X egg weight. A significant positive linear relationship between chick weight: egg weight ratio and egg weight was detected; males increased more than females and dwarf dam chicks more than standard dam chicks. This suggests that chicks from large eggs utilize egg nutrients more efficiently than those from small eggs. Because the larger eggs come from larger hens, it is speculated that there may be a genetic basis to this phenomenon. It was concluded that egg weight, sex, and dam type each significantly contributed to the variability in chick weight and chick weight: egg weight ratio.

Animals↗

PubMed1982

Characterisation of the response of male broiler chickens to diets of various protein and energy contents.

1. The regression of body-weight gain in chicks up to three weeks of age on the linear and quadratic effects of dietary energy and protein contents accounted for approximately 50% of the observed variation. 2. The same model accounted for only 18% of the variation in food consumption, but 68% of the variation in food utilisation (food consumption:body-weight gain ratio). 3. Including initial body weight in the body-weight gain model increased the explained variation from 50 to 65% of the observed variation. 4. The coefficients for the linear and quadratic effects of dietary protein and energy were significantly different from zero for food utilisation, indicating that the response to dietary protein and energy conforms with the 'law of diminishing increments'. 5. Carcass lipid was inversely proportional to carcass water; both showed a linear response to dietary protein concentration.

Animals↗

PubMed1981

Factors influencing the assessment of the availability of choline in feedstuffs.

Experiments were conducted to test the hypothesis that chicks fed diets designed to be first-limiting in choline will also respond to supplements of sulfur-containing amino acids and that the growth response of chicks fed a choline-limiting diet to a supplement of a feedstuff cannot be accepted as a reliable measure of the choline content of the feedstuff. Chicks fed 25% isolated soybean protein (ISP) diets that were severely limiting in choline showed a growth response to supplements of either choline or methionine. A bioassay was used to determine the availability of choline in soybean meal (SBM). Results indicated that including 10% SBM in the 25% ISP diet (at the expense of corn starch) drastically altered the chicks' response to choline. When 100 ppm choline was added to the 10% SBM diet, growth responses, compared to the original standard curve, indicated recoveries of 400 and 352% in two experiments. Additional studies indicated that chicks fed the 25% ISP + 10% SBM-based diet responded not only to choline additions but also to methionine, cystine, sulfate, and betaine additions. Further, it was shown that chicks fed a practical-type corn-soy-grease-based diet respond equally as well to supplements of 1% concentrated Steffens Filtrate, .2% L-methionine, or 800 ppm choline. The validity of assays of choline availability based on the assumption that choline is the first-limiting nutrient is questioned.

Animal Feed↗

PubMed1981

The effects of high dietary protein and nitrogen levels on the preformed methyl group requirement and methionine-induced growth depression in chicks.

The chick's choline and methionine requirements are both increased by high dietary protein level. Studies were conducted to test the hypothesis that the chicks' need for preformed methyl groups is increased by high protein diets (not methionine or choline per se). Chicks fed 25% isolated soybean protein (ISP) diets responded to methionine supplementation (162 vs 110 g gained in 14 days) but not to choline (119 g vs. 110 g), while those fed 50% ISP responded to either methionine (174 g vs. 126 g) or choline (181 g vs. 126 g) supplementation. Further, neither cystine nor homocystine could replace methionine in improving the growth of chicks fed the high protein diet. In other experiments, L-methionine and betaine HCl were found to alleviate the growth depression caused by excessive levels of L-glutamic acid. Excessive levels of L-methionine had a protective effect against growth depression caused by L-glutamate and diammonium citrate, and conversely, supplementary L-serine and sodium formate were not protective against glutamic acid- or arginine-induced growth depression. The results are consistent with the hypothesis that the preformed methyl group requirement is increased by high levels of dietary protein and excessive nitrogen from a single amino acid.

Animal Feed↗