Biomedical subjects

J D Summers

Publications and source records attributed to J D Summers.

At least 37 records · Page 2Linked to original sources

PubMed1988

Significance of growing photoperiod and light stimulation at various ages for Leghorn pullets subjected to regular or ahemeral photoperiods.

Leghorn pullets were cage reared to 15 or 19 wk of age in environmentally controlled rooms that provided either 8 h or 14 h of light per day. In Experiment 1, birds were moved to laying cages at 15 wk of age and subjected to either 14 h light (L): 10 h (D) dark or ahemeral 14L:14D photoperiods. Feed intake, egg weight, shell quality, and egg production were monitored to 67 wk of age. In Experiment 2, pullets were moved at 19 wk of age and subjected to 14L:10D or 17L:7D light programs. Production parameters were measured as previously described. No significant (P greater than 0.5) interactions were observed between rearing and laying photoperiods, suggesting that increase in the length of photoperiod around time of maturity is not essential for adequate performance. In Experiment 1, ahemeral lighting resulting in reduced egg production, whereas egg shell quality and egg weight were improved (P less than .05). In both experiments, the 14-h rearing program resulted in improved egg size together with improved eggshell quality (P less than .05). Whereas increased egg size may relate to body weight, no explanation is apparent for the consistent pattern with respect to shell quality. In Experiment 2, poorer shell quality was observed with 17 vs. 14 h light per day. It is concluded that light stimulation at maturity has little effect on overall egg production. Improved shell quality observed with birds reared under 14 h light vs. those reared under 8 h per day may relate to a less rapid attainment of peak egg production.

Aging↗

PubMed1987

Effect of dietary lysine on polyamine synthesis in the chick.

Experiments were conducted to determine the effect of dietary lysine on hepatic and renal polyamine synthesis in the chick. High arginine-requiring (HA) and low arginine-requiring (LA) strains were used, with differences in arginine requirements being due, in part, to differences in renal arginase activity. Arginine requirements were 1.2 and 0.9% for the HA strain and LA strain, respectively. A total of 96 chicks (16 per diet, 48 per strain) were fed a crystalline amino acid diet containing requirement concentrations of arginine and 0.95, 1.40 or 1.85% lysine for 2 wk. Hepatic arginase activity was unaffected by dietary lysine in both strains, whereas hepatic ornithine decarboxylase (ODC) activity fell with increased dietary lysine in the LA strain only. Increasing dietary lysine significantly increased renal arginase activity but reduced renal ODC activity in the HA strain only. Increasing dietary lysine also caused decreased renal concentrations of arginine, whereas lysine and ornithine concentration increased in both strains. Concentrations of putrescine also rose. It was concluded that excess dietary lysine increased renal concentrations of ornithine due to induction of arginase. This accumulation of polyamine precursors resulted in increased concentrations of putrescine despite feedback inhibition of ODC.

Adenosylmethionine Decarboxylase↗

PubMed1987

Effects of increasing dietary levels of full-fat canola on performance, nutrient retention, and bone mineralization.

Day-old male broiler chickens were fed diets containing 0, 5, 10, 15, or 20% raw, ground, full-fat canola for a period of three weeks. Increasing the dietary proportion of full-fat canola significantly reduced feed intake (P less than .05) and weight gain (P less than .01), without altering feed:gain ratio. Diet had no significant effect on protein retention although there was a significant decrease in fat retention with an increase in dietary levels of full-fat canola (P less than .01). This was accompanied by a significant decrease in metabolizable energy (P less than .01). Increasing the proportion of dietary full-fat canola significantly reduced the concentration of soap in the digesta (P less than .05) and excreta (P less than .01). There was no significant effect of the dietary treatments on calcium or phosphorus retention. There was also no effect of the dietary full-fat canola on bone ash, bone calcium, or phosphorus content.

Animal Feed↗

PubMed1987

Rearing early maturing pullets.

A number of experiments were undertaken using White Leghorn pullets to determine the effect of diet and growing treatment on 16-wk body weight and carcass composition. Irrespective of the level of dietary energy, body weight gain and carcass composition appeared to be closely correlated with energy intake of the pullets. Diets as low as 15% protein with and without methionine supplementation resulted in 16-wk body weights similar to those of animals fed diets containing 21% protein, suggesting that protein is not a critical nutrient influencing weight gain of pullets. Pullets fed ad libitum every other day from 12 to 16 wk of age were significantly lighter at 16 wk than pullets full fed a regular grower diet or the regular diet diluted with 20% oat hulls. Pullets must achieve a certain body weight and carcass composition in order to trigger the onset of production. Dietary energy, not protein, appears to be the critical nutrient involved.

Animals↗

PubMed1987

Assay for estimating the potency of various methionine-active sources.

A number of experiments were conducted to verify the sensitivity of a low protein (15%) soybean diet for assaying methionine (Met) activity. Although a good response in weight gain and feed:gain ratio was obtained with the addition of supplemental Met to the basal diet, an inconsistent response was obtained when the efficacies of DL-Met and liquid methionine hydroxy analogue (MHA were tested). The addition of nonessential amino acids produced a variable response when added to diets containing MHA, with no difference in the response to aspartic acid or a glycine/glutamic acid mix as nitrogen sources. The addition of glycine to diets supplemented with DL-Met resulted in improved performance with the highest level of Met supplementation, thus suggesting that glycine may be alleviating some deficiency in the high supplemental Met diet. Based on the results of several experiments, MHA was judged to be less efficient than DL-Met on a weight basis.

Animal Feed↗

PubMed1987

Effect of dietary calcium levels near the time of sexual maturity on water intake and excreta moisture content.

Three trials were conducted to investigate the effect of dietary calcium on water balance of leghorn pullets. Trial 1 involved introduction of a 4% calcium layer diet at 112, 123, 134, or 144 days of age. Introducing the layer diet early had an early but transitory effect on water intake (P less than .05) and absolute quantity of excreta moisture, although the pattern of percentage excreta moisture was not clearly defined. In a second trial, birds were moved to laying cages at 105 days, with diet change from 1 to 4% calcium occurring at 112 or 142 days. When the layer diet was offered at 112 days, percentage excreta moisture was higher from 113 to 142 days, although no difference was seen after this time. In a final experiment, introduction of a 4% calcium layer diet at either 112 or 133 days of age resulted in higher percentage excreta moisture at four measurement periods to 245 days of age, although this effect was significant only at 147 days (P less than .05). These results suggest there is a transitory effect of dietary calcium on water intake and excreta moisture content. This affect may be of concern within controlled environment buildings and with certain manure-handling systems. In commercial situations, such dietary changes are often confounded with increased dietary protein concentration, another factor known to influence water balance in pullets.

Animals↗

PubMed1987

Effect of immature body weight on laying performance.

Two trials were conducted to note the effect of immature body size of leghorn pullets on subsequent laying performance, and in particular, egg size. In Trial 1, birds were classified as small, medium or heavy at 15 wk of age (997, 1,100, and 1,226 g, respectively). In Trial 2, segregation at 19 wk resulted in groups with mean weights of 1308, 1411, and 1564 g, respectively. In each trial, weight groups were represented by 40 replicate groups of four individually caged birds. Original weight groupings were maintained throughout the trials (P less than .05). In both trials, immature weight classification had a consistent effect on both feed intake and egg weight (P less than .05); larger birds consumed more feed while producing larger size eggs. In Trial 1, medium weight birds produced more eggs over the 52 wk. Similarly, smaller weight birds produced more eggs than did heavy birds (P less than .05). In Trial 2, weight grouping had no overall effect on egg production, although during the 19 to 23-wk period, heavy birds produced more eggs (P less than .05). It is concluded that immature body weight (15 to 19 wk age) can influence egg weight and that this relationship is linked to levels of nutrient intake. Each 100-g increase in body weight was associated with approximately 3.5 g increase in feed intake and 1.2 g increase in egg weight.

Age Factors↗

PubMed1986

Determination of crude protein and fat in carcass and breast muscle samples of poultry by near infrared reflectance spectroscopy.

Near infrared reflectance spectroscopy (NIR) equipment used consisted of an InfraAlyzer 400+ fitted with 19 discrete filters and an HP-85 microcomputer. Calibrations were developed with chicken broiler carcass samples. Samples were divided into two sets: a calibration (CAL) from which equations were developed and a prediction (PRE) set used to validate the equations. The CAL and PRE sets in the carcass calibration consisted of 45 and 54 samples, respectively. Two equations were developed for the prediction of fat in carcass samples (FAT1 and FAT2). Calibration for breast muscle samples included 30 and 27 samples for CAL and PRE sets, respectively. The accuracy of the calibrations was measured by the coefficient of determination (r2), standard error of the estimate (SEE), coefficient of variation (CV), and the mean difference between NIR and chemical values (d). Repeatabilities of chemical and NIR procedures were determined by the F-ratio of the variance of the differences between replicates. The result of the regression analysis between chemical and NIR values indicated good predictions for crude protein (CP) and fat in carcass samples. The r2 and SEE for CP, FAT1, and FAT2 were .98, .94; .91, 2.48; and .91, 2.51 in CAL set; and .91, 1.03; .68, 2.32; and .69, 2.30 in PRE set samples, respectively. No differences were found between FAT1 and FAT2 equations. The carcass calibration equations were tested with samples from laying hens. Higher SEE were found for CP (1.78), but SEE for fat were similar to broiler carcasses. The calibration for breast samples showed higher SEE for CP and fat when compared with carcass samples.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1985

Influence of the ratio of essential to non essential amino acids on performance and carcase composition of the broiler chick.

Male broilers were fed on isocaloric diets containing 140, 180 or 220 g/kg crude protein from 1 to 3 weeks of age. Four diets were formulated for each protein concentration so that essential amino acids (EAA), all balanced in proportion to requirement, supplied 350, 450, 550 or 650 g/kg crude protein. Weight gain, efficiency of food utilisation and total carcase protein reached plateaux at 550 g EAA/kg protein irrespective of the dietary protein content, whereas the proportion of carcase fat decreased and that of carcase protein increased as the proportion of EAA in the dietary protein increased. All EAA in the diet containing 550 g EAA/kg protein were supplied at 125% of requirement, suggesting that the amino acid requirements as reported are inaccurate. Weight gain and carcase protein were shown to be significantly (P less than 0.001) dependent on total intake of EAA rather than on the proportion of EAA in the diet per se. In order to supply sufficient EAA for maximum gains, the diet had to contain more than 140 g crude protein/kg and 450 g EAA/kg protein.

Amino Acids↗

PubMed1985

Effect of nutrient intake on performance of dwarf broiler breeders.

An experiment was undertaken to test the response of dwarf broiler pullets when fed on two planes of nutrition in the growing period and fed either a 17 or 19% protein diet in the breeder house. Pullets offered 20% more feed in the growing period were heavier at 21 weeks of age and reached 50% egg production 2 weeks earlier than birds fed the regular diet. Pullets fed 20% more feed in the growing period and full-fed to 26 weeks in the laying house, gained appreciably more weight, and although they came into production faster, were less persistent in lay than birds fed the regular diet. There was no difference in egg production, egg size, or body composition of dwarfs fed 17 or 19% breeder diets.

Animals↗

PubMed1984

Effect of heat stress and diet composition on performance of White Leghorn hens.

A total of 192 Single Comb White Leghorn pullets were divided into three groups to study the effect of heat stress and diet composition on feed intake and laying performance at 21, 25, and 33 weeks of age. For each age group all birds were fed a control diet [17.1% crude protein (CP), 2770 kcal metabolizable energy (ME)/kg] for a 7-day period. During this time they were kept at a temperature of 18 C. The temperature was then immediately increased to 35 C, and groups of 16 birds offered either the control diet, a high protein diet (43.5% CP), a high energy diet (3371 kcal ME/kg), or a diet of high nutrient density (28.3% CP, 2842 kcal ME/kg, and 6.5% Ca) for a 3-day period. After the 3-day test period, temperature was returned to 18 C, although birds were still offered the experimental diets for an additional 4 days prior to returning to the control diet. Production parameters were measured for individual birds. Feed consumption, egg production (except for the 21-week-old birds), egg weight, and egg shell thickness decreased (P less than .05) with heat stress. Increases in energy and calcium intake helped partially to maintain normal egg production, egg weight, and egg shell deformation. Egg weight and egg shell deformation returned to pretest levels within an 8-week postexperimental period. With the exception of those birds receiving the control and high nutrient density diets at 21 weeks of age, data collected over the test periods showed that heat stress caused a significant reduction (P less than .05) in liveweight birds.

Animals↗

PubMed1984

Effect of skip-a-day feed restriction on the jejunal mucosa of broiler breeder pullets.

Jejunal tissue was taken from 18-week-old broiler breeder pullets previously reared on a daily or skip-a-day feed restriction system. Light and scanning electron microscopy revealed no changes in mucosal appearance or structure related to feeding system. Comparable duodenal samples all revealed extensive desquamated epithelial damage possibly related to postmortem change.

Animals↗

PubMed1984

Effects of cage density and diet energy concentration on the performance of growing Leghorn pullets subjected to early induced maturity.

Leghorn pullets of a commercial strain were cage-reared at densities of 293 or 586 cm2/bird. Diet treatments consisted of a control step-down protein program, a reverse-protein program, and two treatments involving 18% crude protein throughout rearing with modification of texture and energy concentration according to bird age. Thus, one treatment involved a crumbled low-energy diet to 10 weeks, followed by a crumbled high-energy diet to 16 weeks, while the alternate series involved a mash low-energy diet to 10 weeks followed by the crumbled high-energy diet to 16 weeks. Birds were weighed periodically throughout rearing and, when they were subsequently moved to laying cages, light was immediately increased from 8 to 14 hr. Irrespective of diet treatment, the more liberal density of 586 cm2/bird resulted in a 5 to 8% increase in feed intake (P less than .01). However, this increased intake was not associated with increased body weight (P greater than .05), and as confirmed by carcass analysis, it is assumed that this increased nutrient intake relates to increased maintenance requirement associated with bird activity. Birds offered the crumbled vs. mash high-energy diet to 10 weeks of age, consumed more feed (P less than .01), although change of diet texture from mash to crumble at 10 weeks failed to stimulate appetite. Also, birds reared on either the step-up energy programs were similar in weight to control-reared birds at 16 weeks of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1984

Influence of vitamin deficiency and level of dietary protein on the incidence of leg problems in broiler chicks.

Diets containing either 22 or 30% protein were supplemented with a vitamin mix where one of 11 added vitamins were singly eliminated from the mix. Male, day-old broilers were fed these diets to 3 weeks of age, and weight gains, feed utilization, and leg problems were recorded. In general, the higher protein diet did not result in a greater incidence of leg problems; however, it did alter performance of several of the vitamin-deficient diets as compared to the lower protein diet. Of the 11 vitamins studied only nonsupplementation of riboflavin markedly reduced weight gain and feed utilization during the 3-week feeding period. However, deletions of vitamin D3 and niacin also resulted in reduced performance. Riboflavin deficiency resulted in paralysis in a high percentage of the birds while the niacin-deficient diet gave a high percentage of birds with deformed legs and problems of mobility. The results demonstrate that a high incidence of leg problems may be present in a flock with little or no signs of reduced gain or feed utilization. The data suggest that under practical conditions the elimination of a particular vitamin from a diet for a short period of time would probably have a negligible effect on performance.

Animals↗

PubMed1984

Influence of nutritional modification on skeletal size of Leghorn and broiler breeder pullets.

Two trials were undertaken to study the effect of nutrient intake on skeletal size in growing pullets. Leghorn chicks at 28 days were smaller in weight and shank and keel length when fed 16% as compared to 22% crude protein. Increasing the energy or mineral-vitamin concentration of the diet had no effect on skeletal parameters. Increased skeletal size of pullets in response to increased diet protein was associated with reduced (P less than .01) tibial ash content. In a subsequent trial, broiler breeder pullets were fed, ad libitum, starter diets (0 to 21 days) containing graded levels of protein from 20 to 13%. Reducing protein level had a consistent negative effect on body weight, shank length, and keel length at 21 days. When birds were subsequently fed restricted quantities of a common grower diet, no differences in body weight and skeletal parameters were evident at maturity. It is concluded that although early body weight and skeletal size can be markedly influenced by diet protein level, such effects are subsequently nullified by conventional restricted feeding programs.

Aging↗

PubMed1984

Effect of previous diet on feed intake and body weight gain of broiler and Leghorn chicks.

An experiment was conducted to examine the effect of previous diet on feed intake and weight gain, in the subsequent period, for broiler and Leghorn cockerels. Three dietary treatments, consisting of 20% protein and either 2400, 2800, or 3200 kcal Me/kg, were fed in combinations consisting of three, 2-week periods, with nine combinations in all. The experimental design was balanced for residual effects, and period weight gains and feed intake were determined. Analysis of the data by period indicated that treatments by residual interactions were confined to the final period. Therefore, it was concluded that diets fed in the previous two periods may be acting in combination to effect weight gain and feed intake in the final period. Examination of the pooled period data indicated that for optimum performance, broilers required a dietary regimen consisting of increased calorie-to-protein ratios with time while Leghorns required lower calorie-to-protein ratios. Type differences were also observed in the ability to adapt to high protein, low intakes: Leghorns grew optimally but body weight gain for broilers was reduced with such a feeding program.

Animal Feed↗

PubMed1983

Consequence of increased feed allowance for growing broiler breeder pullets as a means of stimulating early maturity.

Two hundred and forty Hubbard X Hubbard breeder pullets, 3 weeks of age, received conventional quantities of feed according to the breeder's recommendation or 5, 10, or 20% extra feed allowance. On reaching an average weight of 2.1 kg, birds were moved to laying cages, subjected to 14 hr of light per day, and offered a breeder diet at the breeder's recommended allowance. Increased feed intake resulted in increased growth rate such that control, +5, +10, and +20% groups reached 2.1 kg liveweight at 20, 18, 18, and 16 weeks, respectively. Total feed intake was significantly less to 2.1 kg liveweight for the younger birds. The early move to the laying house subsequently resulted in early maturity. However, these birds failed to show persistency of production after peak, there being a 10% decline within a 4-week period. Control reared birds, starting production at 23 weeks, exhibited a more conventional and persistent peak egg production. There was an indication that early maturity adversely affected egg size. The significant saving in pullet feed cost warrants further trials aimed at elucidating the mechanisms affecting persistency of production in early maturing broiler breeders.

Animals↗

PubMed1982

Performance of laying hens subjected to intermittent lighting initiated at 24 weeks of age.

Leghorn pullets of a commercial strain were subjected to a conventional light program of constant photoperiod or an intermittent programming involving, during the house of conventional "lights-on", 45 min light (L): 15 min dark (D) from 24 to 27 weeks of age; 30 min L:30 min D from 28 to 35 weeks; and 14 min L:45 min D from 36 weeks to the duration of the trial. Each light treatment was tested with 12 replicate groups of 14 individually caged birds housed in adjacent rooms, with all birds fed a standard 15% crude protein, 2750 kcal ME/kg diet. Intermittent lighting resulted in a significant (P less than .05) reduction in feed intake and a consistent but nonsignificant (P less than .05) reduction in egg production. Egg size, egg shell quality, and albumen quality, as assessed by Haugh units, were not affected by light treatment. Due to the effect on egg production, it is concluded that intermittent lighting programs should not be initiated close to time of peak egg production.

Animals↗