Biomedical subjects

G M Pesti

Publications and source records attributed to G M Pesti.

At least 73 records · Page 4Linked to original sources

PubMed1995

The magnitude of lead toxicity in broiler chickens.

Four experiments were conducted to study the toxic effects of supplemental dietary lead (Pb) on broiler chickens from hatching to 42 d of age. Dietary variables were 0, 0.1, 0.5 or 1.0 mg Pb/kg feed as lead sulfate in Experiment 1, and 0, 0.5 or 1 mg Pb/kg feed as lead sulfate and lead acetate in Experiment 2. Experiments 3 and 4 were 2 x 4 factorial designs with 2 levels of calcium (0.65% or 1.30%) and 4 levels of Pb (0, 1, 10 or 100 mg Pb as lead sulfate/kg feed). Lead supplementation caused linear decreases in body weight gain in all experiments. In Experiments 1, 2 and 4, even 1 mg added Pb/kg feed caused significantly depressed body gains. Significant negative effects of added Pb on feed conversion ratios were found at 10 mg Pb/kg feed. Supplemental Pb caused a linear decrease in delta-aminolevulinic acid dehydratase (ALAD) activity. The higher level of calcium (1.30%) in the feed significantly reduced the negative effects of Pb on ALAD inhibition. Lead additions to the diet resulted in a dose-related increase of Pb in blood, kidney, liver and tibia. Higher dietary calcium caused reduced Pb in blood and liver. Lead is toxic to chickens at much lower levels than previously recognized.

Animal Feed↗

PubMed1994

Comparative responses of genetically lean and fat chickens to lysine, arginine and non-essential amino acid supply. II. Plasma amino acid responses.

1. Three experiments performed to study the effects of amino acid imbalances on the growth of genetically lean (LL) and fat (FL) male chickens from 28 to 42 d of age were described by Leclercq et al. (1994). The plasma amino acid concentrations of birds on selected treatments from that paper are reported here. In experiment 1, three dietary concentrations of digestible lysine were compared (4.75, 6.75 and 7.75 g/kg). In experiment 2, two dietary concentrations of digestible arginine were compared (6.53 and 10.00 g/kg). In experiment 3, three diets were compared: a high-protein diet (189 g CP/kg), a low-protein diet containing added essential amino acids (144 g CP/kg), and this low-protein diet supplemented with 40 g/kg of non-essential amino acids (NEAA; glutamic and aspartic acids). 2. The present results are compared with two earlier reports on the same genotypes. The LL consistently had lower plasma concentrations of methionine, cystine, phenylalanine, isoleucine and valine, and higher concentrations of histidine, than the FL chickens. In 4 of 5 experiments, LL leucine concentrations were lower, and glutamic acid, tyrosine, glutamine and alanine were higher, than in the FL. The other amino acids measured; arginine, lysine, aspartic acid, glycine and serine, exhibited variable responses among the experiments. 3. When the limiting essential amino acids, lysine and arginine, were added to a deficient diet, the plasma concentration of the supplemented amino acid increased while the others remained constant or decreased. 4. When glutamic and aspartic acids were added to the low protein diet, plasma amino acid responses were similar to those of adding a limiting amino acid to a deficient diet, except that alanine exhibited a dramatic increase. 5. Although there were genotype by diet interactions for several amino acids, the interactions were caused by differences in the degree of the responses, not in their direction. 6. These results suggest that the FL and LL genotypes do not utilise various amino acids with the same efficiency and, as a consequence, the ideal profile of dietary amino acids should not be the same for both lines. The results support the hypothesis that selection for fatness and leanness changed the amino acid requirements independently of the effects of food intake.

Amino Acids↗

PubMed1993

Evaluation of the protein to energy ratio concept in broiler and turkey nutrition.

The main objective of feed formulation should be to maximize profits, the difference between returns (growth response) and costs [feed intake (FI)]. For broilers and growing turkeys it is necessary to predict the BW and feed intake responses in order to estimate which protein and energy levels maximize profits for the producer. Data from the literature were collected to evaluate whether growth and FI responses can be better predicted from the dietary protein to energy ratio than protein and energy levels. The Ordinary Least Squares method was applied to estimate the coefficients (Bn) of each model. The best model was selected through the J-test. The protein to energy ratio model was not selected in any case by the J-test. The model based on the protein and energy levels was selected by the J-test to predict the BW response in eight out of nine cases and to predict FI in six out of nine cases. A nested selection was performed to find models for each data set that only include coefficients that are significantly different from zero. The nested selection showed that BW and FI responses can be predicted successfully from protein and energy levels with coefficients of determination between .79 and .97 for broiler chickens and between .45 and .65 for turkeys. Nutritionists should consider the use of models, like the protein and energy levels model, that explain and predict BW and FI responses. Future modeling research should consider important factors in broiler production, like age, sex, and temperature.

Animals↗

PubMed1993

An investigation of the distribution of the protein content of samples of corn, meat and bone meal, and soybean meal.

This study examines the critical assumption of a normal distribution for protein content in feedstuffs. Data were collected from broiler feed mills on the nutrient content of corn, meat and bone meal, and soybean meal. Tests of normality for protein within each feedstuff were performed by each of two methods: 1) the Shapiro-Wilk test (n < 50) or Kolmogorov-Smirnov test (n > 50); and 2) the D'Agostino-Pearson K2 test. Results indicate that protein is non-normally distributed in corn and in meat and bone meal, but protein is normally distributed in soybean meal.

Animal Feed↗

PubMed1992

Effects of tryptophan supplementation to a maize-based diet on lipid metabolism in laying hens.

1. Experiments were conducted with laying hens to determine the effects of supplementing 0, 1.0, 2.0 and 3.0 or 4.0 g trp/kg diet to a maize and soyabean meal-based laying ration (basal tryptophan = 1.66 g/kg) on tissue lipid concentrations. 2. Plasma cholesterol, triglycerides and nonesterified fatty acids were increased by supplementing the diet with 1.0 g trp/kg diet and decreased with 3.0 or 4.0 g trp/kg diet. A significant quadratic effect of supplemental tryptophan was observed on plasma lipids in most cases. The observed effects diminished with time. No consistent changes were observed in plasma glucose concentrations. 3. Total liver lipids were reduced by supplemental tryptophan at all concentrations.

Animal Feed↗

PubMed1992

Model for predicting egg output and metabolisable energy intake of laying pullets.

1. The data compiled by Marsden and Morris (1987) to examine the relationships between environmental temperature and the long-term, adapted responses of laying pullets were divided at random into two subsets of 99 and 113 observations. The first subset was used to estimate regression coefficients for an econometric model, and the second subset to validate the model. 2. Equations to predict inputs (costs) and outputs (returns) were estimated with a three-stage least-squares regression model. Three stage least-squares estimation is a technique which corrects for the simultaneity of variables within the model and correlation across equations of the model. This results in more efficient estimates of the regression coefficients. 3. The final output and output equations were: MEI = 253.86-190.31EM+5.766EM2-0.546EM3 + 0.7034T-0.004388T3 + 695.08BW-120.23BW2 + 397.37ME-13.132ME2-1.06MEXT; R2 = 0.86; EO = 119 + 0.025MEI -0.0000045MEI2-1.462T-0.0791T2-135.3BW + 38.31BW2-1.483T X BW + 0.0288T2 X BW + 0.673 delta BW; R2 = 0.59 where MEI = daily metabolisable energy intake (kJ/bird d), T = environmental temperature (degree C), EO = egg output (g/bird d), BW = body weight, and ME = metabolisable energy concentration (kJ/g). The values for R2 indicate very good fits considering that the data were recorded over a 26-year period in 14 different laboratories. 4. This statistical model can serve as the basis for an econometric model of egg production to determine the environmental temperature that maximises profits from laying pullets of different body weights.

Animals↗

PubMed1992

Comparison of equations for predicting the metabolisable energy intake of laying pullets.

1. The accuracy of equations to predict metabolisable energy intake of laying hens was compared using a random sample of the data set of Marsden and Morris (1987). 2. The equation of Pesti et al. (1992) was found to be significantly better at predicting metabolisable energy intake than the equations of Byerly (1941), Emmans (1974), Byerly et al. (1980), and the National Research Council (1984) when equation residual mean square errors were tested. 3. The equation of Pesti et al. (1992) had the highest coefficient of determination (R2), the smallest average residual, and smallest mean square error. The NRC equation predicted the average metabolisable energy intake best, indicating that over- and under-predictions offset each other. 4. The equations of Emmans (1974) and Pesti et al. (1992) were essentially without bias across temperature zones: less than 20, greater than = 20 less than 25, greater than = 25 less than 30, and greater than = 30 degrees C. The equation of Byerly (1941) over-predicted below 25 and above 30 degrees C, but under-predicted between 25 and 30 degrees C. The equation of Byerly et al. (1980) under-predicted below 30 degrees C while the NRC (1984) equation under-predicted above 20 degrees C.

Animals↗

PubMed1991

Response surface approach to studying the protein and energy requirements of laying hens.

Two experiments were conducted with hens from 20 to 44 wk of age housed in cages. There were 384 hens in Experiment 1 and 360 hens in Experiment 2. The hens were fed various levels of protein and energy in a factorial arrangement in Experiment 1 and in a central composite rotatable design in Experiment 2. The diets contained primarily ground corn, soybean meal, wheat middlings, and poultry oil. Production responses to dietary protein and MEn were found to be nonlinear in nature and thus conformed to the law of diminishing marginal returns. Protein by MEn interactions, when significantly different from zero, were small in magnitude. Variability in hen performance (as measured by hen-day egg production, feed consumption, egg weight, and body weight gain) could be described better by using dietary protein and energy levels than the energy to protein ratio.

Animal Feed↗

PubMed1991

Research note: adding coefficients for dietary protein and energy to equations for predicting the metabolizable energy intake of laying hens.

The data from two published experiments were used to determine whether feed consumption prediction equations could be improved by the addition of coefficients for levels of protein and energy in the diet. The two experiments were conducted from 20 to 44 wk of age with hens housed in cages. Diets contained primarily corn, dehulled soybean meal, wheat middlings, and poultry oil. When the standard form of feed consumption prediction equations was fitted to the data, only the coefficient for egg mass (b3) was different from zero (P less than .10): MEI = b0 + b1 BWn + b2 delta g + b3 EM where MEI = metabolizable energy intake; BW = average body weight (kilograms), delta g = daily body weight change (grams); n = .65, .75, 1, or 2; and EM = daily egg mass output in grams. Three published equations that have been used to predict feed intake based on body weight and egg mass output were chosen for evaluation. For two equations the residual MEI (observed-predicted) was found to be predictable from protein or energy levels fed. Inserting dietary protein and dietary energy data for the feed decreased the observed error in equations to predict MEI, but the effect was small.

Animal Feed↗

PubMed1991

Effect of tryptophan supplementation on aflatoxicosis in laying hens.

Two experiments were conducted to determine the relationship of supplemental Trp on liver fat accumulation and egg production during aflatoxicosis in laying hens. In Experiment 1, two levels of Trp (0 and 2,000 ppm; basal = .16% Trp) and two levels of aflatoxin (AFLA) (0 and 10 ppm) were supplemented to a complete layer ration. In Experiment 2, a third level of AFLA (5 ppm) was added to the design. Single Comb White Leghorn hens (58 and 68 wk old) were fed the diets for 3 wk for Experiments 1 and 2, respectively. Henday production and egg weights were measured daily. Feed intake was measured weekly. Liver weights, liver moisture, and liver total lipids were determined at the end of each trial. In Experiment 1, supplemental Trp by itself caused a significant (P less than .01) reduction in total liver lipids compared to the controls (no Trp or AFLA). Adding trp and AFLA increased total liver lipids and caused a significant (P less than .05) decrease in egg production compared with adding AFLA alone. Total liver lipids were 41.1, 32.8, 54.8, and 62.4% (dry weight basis) for 0 Trp:0 AFLA, 2,000 Trp:0 AFLA, 0 Trp:10 AFLA, and 2,000 Trp:10 AFLA, respectively. Similar results were observed in Experiment 2. It was concluded that supplemental Trp by itself caused a reduction in total liver lipids, but when supplemented to a diet containing AFLA, Trp caused an increased severity of lesions associated with aflatoxicosis in layers.

Acute Disease↗

PubMed1991

Folate deficiency in chicks fed diets containing practical ingredients.

Development of folate deficiency was evaluated in young chicks fed diets containing corn and soybean meal as major constituents. Folic acid deficiency, as indicated by retarded growth and feed efficiency, could be produced in 18-day-old chicks. Chicks fed the basal diet had increased growth when given supplements of either folic acid, choline Cl, or DL-methionine, but not vitamin B12. Relative liver size (grams per 100 g of body weight) was reduced by a methionine or methionine plus choline supplement in two experiments but by folic acid in only one of two experiments. Plasma hemoglobin was reduced by folic acid or a methionine and choline supplement after 42 days on the diets. Folic acid deficiency can be produced in young chicks with a diet based on practical ingredients. Purified diets or very high levels of antibiotic feeding are not necessary to produce folic acid deficiency as long as low levels of methionine and choline are present in the basal diet.

Animal Feed↗

PubMed1991

Influence of method of model fitting and gender on estimated parameters for the relationship between starvation heat production and body size in the domestic fowl.

The relationship between starvation heat production (SHP) in kJ/d and body weight (W) in kg for domestic fowl was examined with compiled calorimetric data for 294 fowls (Johnson and Farrell, 1985). Linear regression analyses using ordinary least squares methods were performed before and after transformation of the data to a logarithmic scale (base = 10). Coefficients of determination (R2) were similar for untransformed and log-transformed data (R2's = .56 and .53, respectively). The slopes for untransformed data of males and females were different (P less than 0.033). When the model parameters for: SHP = b0 Wb1 were derived from log-transformed data, there were no significant differences in exponents for males vs. females (P greater than .95). However, when the coefficients were estimated using non-linear regression techniques, a difference was detected at the level of P = 0.072. It was determined that there is no advantage in describing the relationship of SHP as a non-linear function of W, nor is it appropriate to express physiological variables as a ratio of weight raised to some mass exponent without statistical justification. Using W or W2 as a covariable for the statistical analysis of physiological data would produce equally acceptable determinations of significance.

Animals↗

PubMed1990

Energy exchange of two breeds of hens in respiration chambers.

The heat production for two breeds of laying hens was estimated by indirect respiration calorimetry. Using multiple linear regression techniques, egg energy output was identified as a significant contributor to variability in heat production (P = .0113). Heat production of the hens decreased with increasing egg energy output. Body weight, feed intake, egg energy output, and genetic stock were all significant contributors to variability in heat production. Comparisons of traditional techniques (relating energy balance to metabolizable energy intake) and multiple regression techniques (heat production as a function of body weight, feed intake, egg energy output, and genetic stock) for evaluating calorimetry data were made.

Animals↗

PubMed1990

The influence of dietary tryptophan on broiler chick growth and lipid metabolism as mediated by dietary protein levels.

Three experiments were conducted to determine how dietary protein and tryptophan influence the lipid metabolism of growing broiler chicks. A diet-dilution method (corn-corn gluten meal-gelatin summit/corn starch basal) was used in three factorial experiments. Various levels of protein and tryptophan were fed in each experiment: protein from 16 to 28% and tryptophan from .34 to 2.74% of protein. Gain was maximized when the dietary levels of tryptophan were .83 +/- .03, 77 +/- .04, 77 +/- .05, and .78 +/- .05% of the protein for 16, 20, 24, and 28% dietary protein, respectively. The requirement estimates for feed efficiency and gain were similar. Liver lipids significantly decreased as the level of dietary tryptophan increased at each protein level (P less than .0001). Dietary tryptophan did not significantly alter the concentration of total plasma lipid in the chicks or in the carcass lipid content (P greater than .2399). Tryptophan supplementation significantly increased the concentration of plasma linoleic acid and plasma free tryptophan. The requirement of the chicks for tryptophan was estimated to be .80 +/- .01% of the dietary protein for the growing chick. Increased liver lipid and decreased plasma tryptophan are diagnostic lesions suggesting a tryptophan deficiency.

Animal Feed↗

PubMed1988

Critique of methods of estimating the variability of metabolizable energy from assays with fasted roosters.

Metabolizable energy values from assays with fasted roosters are often calculated: 1) without regard to variability in data from control roosters, 2) with chemical determination on pooled and not individual data, and 3) from data sets with statistically aberrant points removed. Data from determinations of the ME of a feather meal sample were used to examine the influence of these practices on the reported mean and variance values. Ignoring the variability of the fasted controls or pooling excreta samples did not have large effects on the means or variances of these samples. Eliminating data from roosters whose excreta weights are more than one standard deviation from the mean had little effect on the mean value but made the variance appear much smaller than it actually was. As a result of these practices, researchers may place too much confidence in their data and fail to use enough replicates (roosters) to justify that confidence.

Animal Nutritional Physiological Phenomena↗

PubMed1987

Effects of feed composition and feeding schedule on growth and development of broiler breeder males.

Two experiments were conducted to compare the effects of feeding broiler breeder males: 1) a 15 or 20% protein starter diet (0 to 4 weeks) and 2) varying levels of energy and protein on an every day (ED) or on an every other day (EOD) basis during the growing period (4 to 20 weeks). Weight gain and shank length at 28 days were less for males started on 15% protein in both experiments. In the first experiment, males fed diets containing 2.8 kcal metabolizable energy (ME)/g during the grower period weighed and gained more than those fed 2.0 kcal ME/g although total ME intake was the same. Males fed ED gained significantly more than those fed EOD. In the second experiment, males fed 15% protein during the grower period gained and weighed more than those fed 12 or 18% protein, and those fed 15% ED gained and weighed significantly more than those fed 20% EOD. In both experiments males fed ED were more feed efficient (as measured by gain/feed consumed) than males fed EOD but consuming the same amount of feed. Semen characteristics were not affected by feeding schedule or grower diet protein level. Fertility was higher in 3 of the 4 weeks sampled for males fed 15% ED. Results indicate that feeding schedule (ED vs. EOD) as well as nutrient intake influence body weight gains of broiler breeder males.

Animal Feed↗

PubMed1987

Research note: nutritive value of poultry by-product meal. 3. Incorporation into practical diets.

Studies were conducted to investigate the value of poultry by-product meal (PBPM) when incorporated into practical diets at low levels (5 to 10%). Samples from one plant, a Monday morning sample (fresh broiler waste) and a Friday afternoon sample (broiler and hatchery waste and dissolved air flotation sludge) were compared to a sample from another plant (fresh broiler waste). When the samples were incorporated at the 5% level into isocaloric, isonitrogenous corn-soy meal-based practical diets, no differences in 20-day gain or feed efficiency could be detected between the samples or in comparison with the effects of feeding an all-plant-based control diet in two experiments. Chick growth and feed efficiency were significantly depressed when PBPM was incorporated into the diet at the 10% level.

Animal Feed↗

PubMed1987

Influence of choline and sulfate on copper and toxicity and substitution of and antagonism between methionine and copper supplements to chick diets.

Studies were conducted to determine if the deleterious affects on chick growth of the primary antagonism between methionine and copper involves the homocysteine moiety or labile methyl group of methionine. A .1% choline supplement resulted in performance response similar to that of a .2% L-methionine supplement in the absence but not in the presence of 500 mg/kg copper from cupric sulfate. Similar results were observed when the levels of methionine and choline were doubled. Sulfate, with or without choline, had little effect in the presence of cupric sulfate. When cupric acetate was used instead of cupric sulfate, a small but nearly significant (P = .08) response to potassium sulfate was observed. Maximum performance with .29% supplemental methionine and 188 mg/kg Cu was predicted from a response surface analysis. The methionine requirement was increased by feeding copper. However, the increase in methionine requirement was accompanied by an improvement in growth rate and feed efficiency. This may explain why levels used of methionine and total sulfur-containing amino acids appear to be higher under field conditions (with pharmacological levels of copper) than in laboratory conditions (without pharmacological levels of copper). The primary antagonism between methionine and copper involves the homocysteine moiety, not the labile methyl groups.

Animals↗