Biomedical subjects

J D Summers

Publications and source records attributed to J D Summers.

At least 19 recordsLinked to original sources

PubMed1997

Layer performance of four strains of Leghorn pullets subjected to various rearing programs.

Two experiments were conducted using four strains of Leghorn pullets, namely Babcock, DeKalb, H & N, and Shaver. Pullets were grown on conventional or low protein diets fortified with additional amino acids. At 18 wk of age, 64 pullets from each strain and diet treatment were transferred to individual laying cages, using eight replicate groups of four adjacently caged birds. In a second experiment, pullets from the four strains were selected based on body weight at 18 wk of age (approximately 1,270 vs 1,650 g). Each weight group and strain was again represented by eight replicate groups of four birds. In Experiment 1, there were no strain or rearing diet effects on egg production (P > 0.05). Rearing diet had little long-term effect on any adult characteristics. There were significant (P < 0.01) strain effects on body weight, feed intake, and egg weight, although these were independent of rearing diet. In Experiment 2, regardless of bird strain, the pullets with smaller body weight matured more slowly (P < 0.01) and produced less total egg mass to 70 wk age (P < 0.05). These smaller birds ate less feed and produced smaller eggs (P < 0.01). There were strain effects, independent of 18-wk body weight, for egg weight and eggshell quality (P < 0.01). It is concluded that minor strain differences exist with respect to response to juvenile nutrition, although such effects are only evident in early lay. All strains of bird remain small, 18-wk body weight is reduced, and these birds subsequently eat less feed and produce smaller eggs.

Aging↗

PubMed1996

Broiler response to energy or energy and protein dilution in the finisher diet.

Two experiments were carried out with male broiler chickens in which diets from 35 to 49 d of age were diluted by oat hulls and sand. In one experiment only energy was diluted; in the second experiment, both energy and protein (amino acid) levels were affected. Each diet was tested with four replicate floor pens each containing 25 1-d-old birds. All birds received a standard starter diet to 16 d and then grower diet to 35 d. In Experiment 1, dilution of only energy resulted in a significant linear (P < 0.01) reduction in body weight at 42 d, although there was growth compensation after this time such that all birds weighed the same at 49 d. Diet energy dilution resulted in increased feed intake, although energy intake was not maintained (P < 0.01). Diet energy dilution generally had little effect on carcass weight or yield of breast meat, although there was less abdominal fat (P < 0.01). In Experiment 2, dilution of both energy and protein had a comparable effect on growth rate as described in Experiment 1; however, in this study there was a linear decrease in carcass weight and breast meat yield as the diet was diluted. These results suggest that the male broiler chicken can grow quite well on very low energy diets but that a period of at least 7 d is required for adjustment to feed intake. Even with compensatory increase in feed intake, however, the bird is unable to maintain its energy intake when fed such diluted diets.

Amino Acids↗

PubMed1996

Broiler response to diet energy.

Male broiler chickens were fed corn-soybean diets providing 2,700, 2,900, 3,100 or 3,300 kcal ME/kg. In all experiments, each treatment was tested with three replicate groups of 30 birds grown to 49 d of age. In Experiment 1, birds consumed the various diets ad libitum whereas in Experiment 2, all birds received identical and restricted quantities of feed so as to ensure variable intakes of energy. In a third experiment, after 7 d of age, broilers had access to feed in two feeders that contained only the highest level of energy, or the 3,300 kcal ME/kg diet in combination with one of the other diets previously described. Providing diets of 2,700 to 3,300 kcal ME/kg for ad libitum consumption had no effect on growth rate (P > 0.05) and energy intake was constant; however, reducing the energy level of the diet did result in reduced carcass fatness (P < 0.01). When feed intake was controlled in Experiment 2, there was reduced growth (P < 0.01) rate as energy level of the diet was reduced. This reduced growth was associated with dramatic reduction in carcass fatness (P < 0.01), although breast meat yield was not affected. When broilers were offered a choice of diets, they showed remarkably precise control of intake, such that energy intake was again constant across all treatments. However, even though energy intake was constant, broilers consuming the choice diets involving the lower energy content diets tended to have less carcass fat. It is concluded that the broiler still possesses a good ability to control its feed intake based on desire to normalize energy intake. As energy intake is decreased, or there is increased protein intake, the bird deposits less carcass fat.

Animals↗

PubMed1995

Reduced dietary phosphorus levels for layers.

Two experiments were undertaken to study the response of White Leghorn hens to low dietary phosphorus levels from 18 to 64 wk of age. A corn-soybean meal diet containing .2% available phosphorus gave similar performance, up to 32 wk of age, as a similar control diet containing .4% available phosphorus. Beyond 32 wk, although shell quality and average egg weight were similar, egg production was significantly reduced with the lower phosphorus diet. Phosphorus excretion (grams per bird per day) averaged .47 g for .4% vs .28 g for .2% available phosphorus when measured at 28 wk of age. In a second experiment identical procedures and bird number as used in Experiment 1 were employed with the exception that the test diet contained .3% rather than .2% available phosphorus. No differences were noted for any of the production variables measured between the .4 and .3% available phosphorus diets. Phosphorus excretion data collected at 25, 32, 44, and 60 wk of age showed a decrease of approximately 20% for hens receiving the lower phosphorus diet. Indeed the overall average for phosphorus excretion for the lower phosphorus diet was calculated to be identical to the 20% lower total phosphorus content of this diet (.59 vs .47%).

Aging↗

PubMed1994

Laying hen performance as influenced by protein intake to sixteen weeks of age and body weight at point of lay.

White Leghorn chicks were fed corn-soybean meal diets containing 20, 17, 14, and 11% protein, with similar levels of energy, from hatch to 16 wk of age. Body weights at 16 wk were similar for pullets fed the 20 and 17% protein diets, but were reduced by 11 and 27% for birds fed the 14 and 11% protein diets, respectively, as compared with the 20% protein diet. At 16 wk of age, all birds were placed on a common 17% protein laying diet. Pullets fed the 14 and 11% protein laying diets were slightly slower coming into production, however, by 28 wk of age egg production was similar for all four growing treatment groups and remained so until the end of the experiment. Average egg weight was similar for pullets fed the two higher levels of protein during the growing period and significantly lower for those pullets fed the 11% grower diet for all except the 28- and 32-wk periods. Pullets fed the 14% grower diet produced eggs with average weights significantly lower than those for the higher protein diets from 40 to 58 wk of age. Although the results might be interpreted as indicating that higher protein growing diets result in body protein reserves that subsequently enhance egg size, it is more likely that the pullets consuming lower protein diets produce smaller eggs because they have smaller body weights.

Age Factors↗

PubMed1993

Reducing nitrogen excretion of the laying hen by feeding lower crude protein diets.

Several experiments were undertaken to investigate nitrogen excretion for laying hens fed diets varying in level of dietary protein. Reducing dietary protein levels from 19 to as low as 5% resulted in a concomitant decrease for up to 50% in nitrogen excretion. Depending on age of the hens, dietary protein levels as low as 11% gave reductions in nitrogen excretion for up to 40% when compared with a conventional 17% protein corn and soybean meal diet, with a minimum reduction in egg mass output. Because exceptionally high intakes of dietary protein are required to maximize egg size, there is merit to optimizing rather than maximizing egg mass output.

Animals↗

PubMed1993

Influence of prelay treatment and dietary protein level on the reproductive performance of White Leghorn hens.

Two experiments were undertaken to study the influence of prelay diet treatment on subsequent laying performance. Feeding either a conventional laying or growing diet or diets containing essentially only wheat bran from 18 to 21 wk resulted in little grower diet carryover effect beyond 24 wk of age, although the wheat bran diets resulted in a marked drop in body weight of the pullets during the prelay treatment. Similar performance was noted for pullets in a second experiment in which prelay treatments consisted of feeding just corn or wheat bran from 18 to 20 wk of age. In interpreting the results of the present study, it is important to consider the fact that "mature pullet weights" were obtained before the prelay diet treatments were employed. Where prelay diet treatments have had significant effects on laying house performance, in most cases, immature or underweight pullets were involved. Feeding hens low-protein diets (13 versus 17%) from 20 to 44 wk of age resulted in similar egg production; however, egg weight and thus egg mass were slightly reduced with the lower protein diet. There was no laying by growing treatment interaction. The importance of good pullet weight at the start of the production cycle and the subsequent performance of such pullets fed low-protein diets is discussed.

Animal Feed↗

PubMed1992

Broiler weight gain and carcass composition when fed diets varying in amino acid balance, dietary energy, and protein level.

Three experiments were conducted with broiler chicks where diet composition varied with respect to dietary protein, energy, and essential amino acid (EAA) balance. Birds fed diets varying widely in EAA balance and protein and energy levels performed differently with respect to percentage carcass fat and protein. The absolute carcass protein deposition remained relatively constant between treatments, but body fat content varied depending on level of energy intake. Although abdominal fat content varied with level of dietary protein and energy, these values did not correlate well with total carcass fat deposition. Carcass fat deposition correlated well with dietary energy intake, which in turn appeared to be influenced by birds eating to satisfy their EAA requirement. With diets of similar EAA balance, birds appeared to have similar EAA intakes rather than similar energy intakes. Birds fed diets with similar EAA levels, but varying widely in level of nonessential amino acids, energy, or both consumed similar amounts of feed and deposited similar amounts of carcass protein. The present data suggest that level and balance of EAA can have a significant effect on feed intake, thereby influencing weight gain and carcass composition.

Adipose Tissue↗

PubMed1992

Response of broilers to feed restriction or diet dilution in the finisher period.

Two experiments were conducted to study the response of 35- to 49-day-old male broilers to either feed restriction or diet dilution. In Experiment 1, after being fed conventional starter-grower diets to 35 days of age, birds consumed either a conventional finisher diet ad libitum, or 10, 20, 30, 40, or 50% less of this diet to 49 days of age. Performance and carcass characteristics were measured from 35 to 42 days and 42 to 49 days. There was a linear relationship between nutrient intake and 42- and 49-day body weight (P < .01). However, as a percentage of the control birds, weight gain was reduced less from 42 to 49 days (64%) than from 35 to 42 days (86%) for the 50% restricted group. Thus, there was apparently an adaptation in the period from 42 to 49 days. In a second comparable experiment, birds were offered a conventional finisher diet or one with either 10, 20, 30, 40, or 50% dilution with a 50:50 (wt:wt) mixture of sand:oat hulls. Growth rate was only slightly reduced, thus demonstrating the remarkable ability of the broilers at this age to increase feed intake in response to energy density of the diet. Although birds were of comparable weight, diet dilution resulted in a linear reduction in size of abdominal fat pad, whereas breast weight was not affected. The present data suggest that broiler chickens are far from eating to physical capacity, at 35 days of age, because they were able to exhibit up to a 70% increase in feed intake relative to the control birds.

Aging↗

PubMed1991

Diet dilution and compensatory growth in broilers.

Two experiments were conducted to note the response of broiler chickens to degrees of diet dilution from 4 to 11 days of age. In Experiment 1, broilers were fed conventional broiler diets from 0 to 4 and 11 to 56 days of age. From 4 to 11 days, birds were fed a conventional corn and soybean meal broiler starter, or the same diet in which major nutrients were replaced with 25, 40, or 55% ground rice hulls. Mineral and vitamin sources were not affected by dilution. Each of the three diluted diets together with an undiluted control diet was fed to three replicate floor pen groups of 30 male or 30 female broilers. In a second similar experiment, male birds were fed a regular broiler starter from 4 to 11 days or a diet diluted with 50% rice hulls. In this second experiment, rice hulls were substituted for all ingredients including those providing vitamin and mineral supplements. In Experiment 1, diet dilution resulted in a significant (P less than .05) reduction in body weight at 11 days of age, although by 42 days there was complete recovery of body weight with no change in overall efficiency of feed utilization. This same trend was seen in both sexes. Calculation of energy balance suggests these birds to have used energy very efficiently during the period of undernutrition. Diet dilution had no effect on carcass characteristics at 42 days, although for males at 56 days there was an indication of reduced abdominal fat content (P less than .05). In Experiment 2, compensatory gain was incomplete, although results were confounded due to an outbreak of infectious bronchitis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗

PubMed1991

Response of laying hens to supplemental niacin.

Two experiments were conducted to investigate the effect of supplemental niacin on laying hen performance and liver fat and egg cholesterol content. In Experiment 1, 16 replicate groups of four adjacently caged birds were fed corn and soybean meal diets calculated to contain 22, 44, 66, or 132 mg supplemental niacin/kg (23.2, 38.7, 57.0, and 143 mg/kg niacin by analysis). Egg production, egg weight, feed intake, and eggshell quality were assessed each 28 days through a 364-day trial period. After 280 days, cholesterol content on three eggs per replicate was measured. At the end of the study, one bird per replicate was killed for subjective scoring of liver fat content. In Experiment 2, 24 birds from the control treatment (22 mg/kg supplemental niacin) of Experiment 1 were retained and fed for a subsequent 28-day period. Over this time, eight birds were each fed diets containing 22, 522, or 1,022 mg/kg supplemental niacin. Egg cholesterol content was measured in eggs collected on the last 3 days of the study. In Experiment 1, birds fed 66 or 132 mg/kg supplemental niacin/kg produced more eggs (P less than .05) than birds fed 22mg/kg. Niacin supplementation affected shell quality (P less than .05). Dietary niacin level had no effect on egg cholesterol content of liver lipid evaluation. In Experiment 2, supplementary niacin levels up to 1,022 mg/kg, which more closely stimulates therapeutic levels used for humans, again failed to affect egg cholesterol content.

Animal Feed↗

PubMed1991

The effect of minimizing amino acid excesses in broiler diets.

A series of experiments were conducted to evaluate the performance of 7- to 21-day-old broilers fed diets in which excesses of essential amino acids (EAA) were minimized. A 23% protein diet in which all EAA except TSAA were in excess was reduced in protein in a stepwise manner, keeping the corn; soybean meal ratio constant, to the point where all EAA were at minimum requirement level based on the 1984 National Research Council (NRC) requirements. Crystalline EAA supplemented those EAA that became deficient as dietary protein was reduced. Other test diets included one containing an additional 10% of the particular EAA in question and one with nonessential amino acids (NEAA) added to make the low-protein diet isonitrogenous with the 23% control. Performance of birds fed the low-protein test diets was not significantly different from that of the control birds. All EAA appeared to be adequate at levels recommended by the NRC in 1984 except Trp, which required .25% for optimal performance. A growth response was observed when Gly was used as the NEAA source; however, no response was noted when mixtures of NEAA were used as the NEAA source, suggesting that Gly may have been limiting in these earlier treatments. Total carcass protein of birds fed the low-protein test diets in which all EAA were minimized was equal to that of the control birds. In a final experiment utilizing the EAA-balanced, low-protein diet, dietary energy was allowed to vary by 15%. The EAA intake was constant, indicating that birds were eating to satisfy EAA requirements rather than energy requirements. Increased carcass fat deposition paralleled dietary energy increases.

Amino Acids, Essential↗

PubMed1990

Weight gain, carcass yield, and composition of large white male turkeys reared to 28 weeks of age on growing and finishing diets with varying levels of dietary protein.

Male, Large White turkeys were reared to 28 wk of age on diets that varied in protein level after 16 wk of age. The diet composition had little effect on weight gain and feed utilization for birds evaluated at 20, 24, and 28 wk of age. The yield and composition of carcass parts were also affected very little by the dietary treatment. Body weight gain over time was fairly consistent to 28 wk of age. Feed utilization declined, especially between 24 and 28 wk of age. Age had a significant effect on the meat yield of the carcass parts. The percentage yield of breast meat was markedly increased from 20 to 28 wk of age, while the percentage yield of thigh and drumstick meat was reduced. While the absolute yield of edible protein increased with age, there was a noticeable increase in fat deposition, especially in the breast and thigh meat with birds that were 28 wk old versus 24 wk old.

Animal Feed↗

PubMed1990

Factors influencing the response of broiler chickens to calcium supplementation of canola meal.

The present study was undertaken to investigate whether broiler chicks fed canola meal, as compared with diets of soybean meal, would respond to a higher level of supplemental calcium. Supplementing canola basal diets and soybean-meal basal diets with additional sulfur from sodium sulfate resulted in little or no change in broiler performance. However, supplementing diets with organic sulfur (cystine) caused a marked decrease in weight gain and feed intake, more severe with a canola diet than with a soybean-meal diet and which could be partially alleviated by increasing the calcium supplementation. A significant cystine-by-calcium interaction showed that feed intake dropped markedly, especially at the higher levels of calcium, as the levels of cystine supplementation increased. Part of the reduced performance, sometimes noted when diets supplemented with canola meal are used, may be due to a reduction in feed intake resulting from an interaction between dietary calcium and sulfur.

Animal Feed↗

PubMed1989

Weight gain and breast yield of large white male turkeys fed diets varying in protein content.

Large White male turkeys were reared in floor pens to 20 wk of age. Diet changes were made every 4 wk, with dietary energy levels kept similar for diets within a period, and changes made in protein levels. Although significant differences in weight were noted at 4 and 8 wk, these diminished with age such that at 20 wk no significant differences were noted. Feed intakes paralleled weight gains. A sample of birds was taken every 4 wk for a measurement of breast meat (excluding skin) and composition. Although changes in dietary protein levels did not affect weight gains to 20 wk of age, breast protein yields were significantly reduced by lowered dietary protein levels. Breast meat varied from 15% of live weight at 4 wk of age to 23% at 20 wk. Protein composition of breast meat varied between 90 and 95% (DM basis), and was estimated to be in excess of 50% of edible carcass protein. With such a high level of edible carcass protein coming from breast meat, it is suggested that yield of breast protein be used as a parameter in determining optimum protein and amino acid requirements of heavy weight turkeys.

Amino Acids, Essential↗

PubMed1988

Effect of dietary ornithine on renal and hepatic polyamine synthesis.

Chicks with genetically elevated renal arginase activity were fed crystalline amino acid diets varying in ornithine concentration (0, 1 or 2%) to assess the potential for precursor regulation of polyamine synthesis. Renal arginase and renal and hepatic ornithine decarboxylase activities fell when ornithine was fed. Renal and hepatic ornithine concentrations rose while putrescine concentrations varied quadratically with ornithine feeding. Spermidine and spermine concentrations were not affected by diet. It was concluded that ornithine synthesized in vivo was a more potent stimulator of polyamine synthesis than ornithine of dietary origin.

Animals↗

PubMed1988

Regulation of polyamine synthesis by dietary alpha-aminoisobutyric acid and ornithine.

An experiment was conducted to determine the effect of feeding ornithine in combination with alpha-aminoisobutyric acid (AIB), an inhibitor of arginase, on the regulation of polyamine synthesis in chicks. A total of 48 chicks with genetically elevated renal arginase activity was fed diets containing crystalline amino acids and 1% AIB with or without 2% ornithine. Feeding AIB reduced renal arginase activity, while renal and hepatic ornithine decarboxylase (ODC) activity increased. Feeding AIB plus ornithine caused no further reduction in renal arginase activity compared with that in chicks fed the AIB-supplemented diet. Renal and hepatic ODC activities, however, fell to below control levels. Renal, hepatic, and breast muscle ornithine concentrations increased substantially when ornithine was fed. AIB plus ornithine increased renal putrescine and spermidine concentrations. It was concluded that AIB could partially overcome the ornithine-induced inhibition of ODC activity. These findings support the hypothesis that dietary manipulation of precursor amino acids of polyamines in the presence of metabolites that induce ODC activity can influence tissue polyamine concentrations.

Adenosylmethionine Decarboxylase↗

PubMed1988

A simplified diet for assaying methionine activity.

Several experiments were undertaken to evaluate diets that could be used to bioassay methionine activity in various compounds. The following semipurified diets were tested: a corn-soy-gelatin basal (CSG) diet supplemented with essential amino acids (EAA) at 23% crude protein (CP); a soybean meal diet at 23% CP; and a soybean meal diet at 15% CP with all the protein coming from dehulled soybean meal and starch, glucose, and fat used as sources of energy. The CSG and 15% CP soybean meal diets proved to be sensitive in their response to methionine supplementation. Birds fed the CSG diet supplemented with methionine and tryptophan were smaller (P less than .01) than birds fed the 23% CP soybean meal diet, thus suggesting that something other than EAA was limiting the performance of birds fed this diet. Based on sensitivity to methionine supplementation, simplicity and cost of diet, the low protein soybean meal diet seems most appropriate for methionine bioassays.

Animal Feed↗