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Biomedical subjects

I R Sibbald

Publications and source records attributed to I R Sibbald.

At least 19 recordsLinked to original sources
PubMed1990

Response of male broiler chickens to dietary lysine:true metabolizable energy (nitrogen-corrected) ratios during three consecutive fourteen-day periods from hatching.

An experiment was conducted to estimate the changes in body composition associated with the concentration of dietary lysine, independent of energy intake. A secondary objective was to determine whether the treatment effects on body composition could be inferred by using the initial body weight of the birds as a covariate, rather than data from groups initially slaughtered. The experiment comprised three phases, based on the age of the birds: 1 to 15, 15 to 29, and 29 to 43 days. The same 56 dietary treatments, arranged as an 8-by-7 factorial, were used in each phase. The dietary treatments consisted of eight ratios for bioavailable lysine and TMEn with seven levels of cellulose dilution, the latter being used to ensure a range of TMEn intakes. The experimental units were groups of 4 chicks in Phase 1 and individual birds in Phases 2 and 3. The comparative slaughter procedure was used. The initial slaughter populations comprised 30 groups of 4 birds for Phase 1 and 40 individual birds for Phase 2 and Phase 3. The intakes of bioavailable lysine and bioavailable energy (ITMEn) were measured, and the body weights were recorded. The carcasses were assayed for dry matter, energy, protein, lipids, and ash. The gains in body weight, water content, and protein content reached maxima at ratios for lysine to TMEn of between .76 and .86 g per mJ, independent of the phase. The gains in dry matter, energy intake, and lipid content per unit of ITMEn were independent of the lysine:TMEn ratio and of the phase (P greater than .05). The phase affected the regression coefficients for gains in body weight and body water (P less than .01) but not for protein (P greater than .05). Phase effects were most apparent in the intercepts of the regression lines where the differences reflected variations in body-maintenance requirements for energy. A covariance analysis provided estimates for the rates of response very similar to those obtained by using data from the initial slaughter groups. Both experimental approaches depend for precision and accuracy on a strong relationship between body weight and composition; such does not appear to exist for total carcass energy and lipid content.

Age Factors↗
PubMed1989

Precision of bioassays for apparent and true metabolizable energy adjusted to zero nitrogen balance.

Formulae are presented for calculating the variance of estimates of AMEn and TMEn obtained from several commonly used bioassay protocols. Formulae are also developed for calculating the variance of the difference between bioavailable energy (BE) estimates of two materials tested in the same bioassay. Methods are described for determining the allocation of experimental units among dietary treatments that minimizes the variance of AMEn or TMEn estimates in bioassays based upon a completely randomized allocation of the dietary treatments to the experimental units. In many situations, the precision of the assay can be considerably improved by assigning more experimental units to the control diet than to the test diets. For completely randomized designs, the precision of AMEn estimates from the basal diet substitution assay is always greater than that from the reference material substitution assay. For randomized block designs, the relationship depends upon the level of substitution and the ratio of the among to within-block variance components. However, the precision of the difference between the estimates of AMEn for two materials is the same in the basal diet and reference material substitution assays for both completely randomized and randomized block designs.

Animal Feed↗
PubMed1989

Standard errors of nitrogen-corrected true metabolizable energy estimates: effects of pooling excreta samples and ignoring among-control bird variation.

To estimate TME(n), it appears to be advantageous to pool excreta samples prior to analysis for energy and nitrogen; accurate (nonbiased) estimates should result. With this protocol, estimates of precision are based entirely on the among-bird variance in excreta weight of the fed birds. However, because of the inconsistent relationship between excreta weight and excreta energy, the SE resulting from this pooling protocol generally are unrelated to the correct values obtained when the energy and nitrogen concentrations are measured in the excreta of each bird. Failure to account for the among-control-bird variation in excreta energy overstates the precision (i.e. underestimates the SE) of TME(n) estimates.

Analysis of Variance↗
PubMed1989

Effect of acclimatization to an excreta-collection harness on excreta energy voided during a nitrogen-corrected true metabolizable energy bioassay.

Two TMEn bioassays were made with adult cockerels to test the hypothesis that excretion inhibition, observed previously as induced by excreta-collection harnesses, can be overcome by a suitable acclimatization period. Each experiment was designed as a 2 x 2 x 3 factorial with normal birds and acclimatization birds fitted with harnesses or housed over collection trays and given one of three dietary treatments. The acclimatization period was 5.75 days. The harnesses generally reduced excreta energy output, and their removal was followed by a compensatory increase. Acclimatization failed to eliminate the harness effect.

Adaptation, Physiological↗
PubMed1988

Comparisons of bioassays for true metabolizable energy adjusted to zero nitrogen balance.

Four experiments were made with adult, Single Comb White Leghorn cockerels to investigate aspects of the bioassay for true metabolizable energy adjusted to zero nitrogen balance (TMEn). Collection of excreta in plastic bags held in place by harnesses (H) doubled the potential bird capacity of a standard cage arrangement relative to that wherein excreta are collected on trays (T). Housing H-birds in adjacent cages had no effect on fecal (F) and urinary (U) energy adjusted to zero nitrogen balance (FEn + UEn) irrespective of whether neighboring birds were fed or fasted. Extension of the preassay fast to 48 h did not prevent the reduction in FEn + UEn, seen in previous experiments, of H-birds relative to that of T-birds. Extension of the preassay fast to 48 h, provision of supplemental glucose, and the variation of test material inputs from 30 to 50 g did not substantially effect TMEn estimates or their precision: supplemental glucose reduced body weight loss, but the appearance of glucose in an excreta sample was a cause for concern. Provision of supplemental water by intubation during fasting and excreta-collection periods had little effect on the variance of FEn + UEn values of fed or fasted birds, and no effect on TMEn estimates. Although excreta collection with H has several advantages, there can be a high incidence of sample loss due to H slippage: 21, 2, 0, and 22% in Experiments 1, 2, 3, and 4, respectively. The reduced FEn + UEn of H-birds is a problem requiring explanation. In terms of data quality, none of the assay modifications was beneficial.

Animals↗
PubMed1987

Effects of dietary fat level and lysine:energy ratio on energy utilization and tissue synthesis by broiler chicks.

An experiment was designed to estimate the effect of dietary fat (20 or 80 g/kg) on the responses of broiler chicks to changes in the ratios of bioavailable lysine (LB) to true metabolizable energy corrected to zero nitrogen balance (TMEn) in their diets. A comparative slaughter experiment used an initial slaughter group of 44 10-day-old male chicks; an additional 120 chicks from the same population were used in the 14-day experiment. Dietary treatments comprised two basal diets differing in fat content and formulated to have similar nutrient:TMEn ratios. Each basal diet was supplemented with four levels of lysine to provide four LB:TMEn ratios calculated, and subsequently found, to be the same in each basal diet series. Each of the eight diets was diluted with five levels of cellulose to ensure a range of intakes under ad libitum feeding. Three individually housed chicks were assigned to each of the 40 diets. Carcasses were assayed for water, nitrogen, lipids, ash, and gross energy; changes in these variables during the experiment were the response criteria. The fat content of the diet had no effect (P greater than .05) on the chick responses to LB:TMEn ratios. At a fixed energy intake the body weight gain, retained water, retained energy as protein and retained ash increased with the LB:TMEn ratio, with no conclusive evidence of a maximum response having been reached for any variable at an LB:TMEn ratio of .83 g/MJ. Retained energy was independent (P greater than .05) of the LB:TMEn ratio but the energy retained as neutral lipids tended to decrease as the ratio increased. The data support the view that the lysine requirement of the broiler chick varies according to the response criterion used in its assessment.

Animals↗
PubMed1987

Need for comparative slaughter experiments in poultry research.

The comparative slaughter technique is a protocol used to estimate changes in the body composition of birds during an experiment. The protocol is based on the assumption that the body composition of the experimental group of birds (EG) at the beginning of an experiment can be predicted accurately and precisely from the carcass compositions of comparable birds from the same population that are slaughtered at the beginning of the experimental period. The present study examines the need for the initial slaughter group (ISG) of birds. By reexamining data from three previously published experiments that used broiler chicks and one that used adult cockerels, it is demonstrated that the same inferences can be obtained by an appropriate analysis of covariance using only the data from the EG birds. Elimination of the ISG results in a considerable reduction in the resources required for experimentation and means that the inferences are based on data obtained only from birds subjected to the various treatments.

Animal Nutritional Physiological Phenomena↗
PubMed1987

A comparison of the amounts of energy and nitrogen voided as excreta by cockerels housed over trays or fitted with harnesses and plastic collection bags.

Three experiments using adult Single Comb White Leghorn cockerels were made to compare the amounts of energy and nitrogen voided as excreta when collected either in plastic bags held in place by harnesses (H) or on trays placed below the wire-floored cages (T). In the first experiment, previously fasted birds were given, by intubation into the crop, 30 g of ground yellow corn or meat meal; other birds continued to be fasted. Excreta were collected for 48 h. The second experiment was similar but included five feedingstuffs and a second excreta collection was made on trays during the 48 to 72-h period postfeeding. The third experiment also involved 0 to 48 and 48 to 72-h collections but the input was a laying hen diet in amounts ranging from 0 to 50 g by 10 g increments. Birds fitted with harnesses voided less excreta energy than T-birds but the output of excreta nitrogen was independent of the collection method. The differences between H and T-birds were independent of the nature and amount of feed input. Removal of harnesses resulted in compensatory excreta energy output in the subsequent 24 h. The H minus T differences were not attributable to outliers within a group because variances were generally similar among collection methods. The reduced excreta energy outputs of H-birds tended to cause higher estimates of true metabolizable energy for the feedingstuffs but the effect was modified because both fasted and fed birds were affected by the harnesses.

Animal Feed↗
PubMed1986

Comparison of three methods of excreta collection used in estimation of energy and nitrogen excretion.

Three methods of excreta collection: plastic trays (T), human colostomy bags affixed to the bird (B), and B containing 25 ml .5 N HCl (A) were compared in three experiments with adult, Single Comb White Leghorn cockerels. There were 128, 130, and 120 birds in Experiments 1, 2, and 3, respectively, from which 97, 84, and 105 excreta samples were obtained; most of the losses occurred among the B- and A-groups. Birds were fasted for 24 hr prior to the experiments and then precision-fed, by intubation, with 0, 5, 10, 15, 20, 25, 30, or 35 g of fish meal (Exp. 1) or soybean meal (Exp. 2). In the third experiment, the inputs were 30 g of corn, fish meal, soybean meal, and a 50:50 (wt/wt) blend of fish meal and soybean meal; control birds were fasted. Excreta were collected for 48 hr after feeding, and the outputs of excreta energy (FE + UE), excreta nitrogen (FN + UN), and (FE + UE) corrected to zero nitrogen balance (FEn + UEn) were measured. True metabolizable energy (TME) values and TME corrected to zero nitrogen balance (TMEn) were calculated. In Experiments 1 and 2, the regressions of (FE + UE), (FN + UN), and (FEn + UEn) on feed input had slopes which were independent of excreta collection methods (P greater than .05), indicating that estimates of TME and TMEn based upon the linear regression assay were not different (P greater than .05). In both experiments, the levels of excreta and energy output using T were greater (P less than .01) than when using B.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1986

Measurement of lipids in chicken carcass dry matter.

Three procedures were used to measure the lipid fraction of chicken carcass dry matter. The resulting data were evaluated by calculating carcass residuals (carcass dry matter-protein-ash-lipid) and by application of multiple linear regression to estimate the energy values of carcass fat and protein. Petroleum ether extraction led to carcass residuals of about 5% and an estimated energy value of protein that was larger than previous estimates. Chloroform:methanol (2:1) extraction gave a negative residual (-6.5%) and a very low predicted energy value for protein. However, when the chloroform:methanol extract was corrected for crude protein content, the residual was approximately 1.0% of the dry matter, and the energy estimates were similar to those obtained previously. The importance of conducting analytical analyses in duplicate is illustrated.

Animals↗
PubMed1985

The bioavailability of supplementary lysine and its effect on the energy and nitrogen excretion of adult cockerels fed diets diluted with cellulose.

A basal diet formulated to be deficient in lysine was supplemented with five levels of L-lysine monohydrochloride and each of the resulting diets was diluted with six levels of cellulose. Each of the 30 diets was precision fed (30 g/bird) to adult cockerels which had been fasted for 24 hr, and excreta voided during the 48 hr following feeding were collected. Twelve fasted birds served as controls. Feed and excreta samples were assayed for lysine, energy, and nitrogen. The bioavailability of the natural lysine was 88.2 +/- 2.5% whereas that of the L-lysine HCl was approximately 92%, significantly (P less than .05) less than the 100% often assumed in lysine requirement studies. The supplemental lysine did not significantly affect (P greater than .05) estimates of bioavailable energy [true metabolizable energy (TME), TME corrected to zero nitrogen balance (TMEn)]. Cellulose dilution had no significant (P greater than .05) effect on either lysine or energy availability.

Animals↗
PubMed1985

The excreta energy and nitrogen losses of adult cockerels during a fast.

Sixteen adult Single Comb White Leghorn (SCWL) cockerels were fasted for 48 hr and then placed on an experiment during which they were fasted for an additional 11 days; water was freely available. Excreta energy (FE + UE), excreta nitrogen (FN + UN), and excreta energy corrected to zero nitrogen balance (FEn + UEn) losses were measured at 24-hr intervals as were body weights (BW) and weight losses (delta BW). One bird died on the second day of the experiment. There were significant differences (P less than .01) in excreta losses among birds and days. The day effect was curvilinear and decreasing, with the largest day-to-day changes tending to occur early in the experiment. The BW, delta BW, and ambient temperature had little effect on the losses with the exception of (FN + UN) which varied in part with BW. The regression of FE + UE on FN + UN, after adjusting for birds and days, yielded a slope estimate of 33.54 +/- 5.12 kJ/g (8.02 +/- 1.22 kcal/g) of nitrogen which is not different (P greater than .05) from values commonly used to corrected bio-available energy values to zero nitrogen balance.

Animals↗
PubMed1985

Changes in the body weights and the final carcass compositions of adult cockerels fed less than their maintenance requirements.

Seventy-two adult Single Comb White Leghorn (SCWL) cockerels of each of two strains were fasted for 48 hr. Twenty-four birds of each strain were killed and frozen. Eight birds of each strain were fasted for an additional 11 days and 4 birds of each strain received, by intubation, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 g of a high energy feed daily for 10 days, after which they were fasted for 48 hr. Birds were weighed and their excreta were collected at 24-hr intervals. At the conclusion of the experiment, all birds were killed and their carcasses, together with those of the initial slaughter group (IS), were assayed for water, protein, fat, and ash. All experimental birds lost weight. The change in body weight (delta BW) decreased linearly as feed input increased. Solution of the derived regression equation provided a mean estimate of .355 MJ/BW.75 kg/day (.0848 Mcal/BW.75 kg) for the energy requirement to maintain body weight. The estimate fails to take account of changes in body composition, but correction for this was impractical because of the large among bird variation. For the fasted birds, the delta BW displayed a logarithmic-decay pattern over time. Carcass protein and water increased with feed input but carcass fat was independent of feed input. However, the proportions of the carcass constituents did not vary with feed input. The proportion of carcass protein was greater and of carcass fat less at the end of the experiment than in the IS birds.

Animals↗
PubMed1984

A longitudinal study of energy and nitrogen excretion by fasted cockerels.

An experiment was conducted in which the energy and nitrogen voided by cockerels during the final 48 hr of each of 14 72-hr fasts, 28 days apart, were measured. There were 12 Single Comb White Leghorn cockerels of each of two strains aged 150 days at the time of the first excreta collection and 12 birds from each of two meat-type strains aged 268 days at the first collection. Birds that died during the experiment were replaced by similar birds maintained under comparable conditions. Both excreta energy (FE + UE) and excreta nitrogen (FN + UN) varied among time periods and among birds and appeared to be related to metabolic body size. Similar patterns were observed when the FE + UE data were corrected to zero nitrogen balance (FEn + UEn ). There was a significant (P less than .01) quadratic relationship between ambient temperature and FE + UE, FN + UN, and FEn + UEn with higher excreta outputs being associated with either low or high temperatures. Frequently, but not inevitably, higher FE + UE and FN + UN were observed prior to death. The FE + UE was significantly (P less than .01) correlated with FN + UN. In general, the estimated regression coefficient relating energy to nitrogen output was similar to the value, based upon the energy content of chicken urine, used to correct FE + UE to FEn + UEn . However, the analyses indicated that the correction factor may vary among birds or over time and may be related to metabolic body weight. To what extent this variability can be defined and incorporated into metabolic energy assays requires further investigation.

Animals↗
PubMed1984

A preliminary investigation of the utilization of true metabolizable energy by chicks.

The change in carcass composition associated with intake of true metabolizable energy (TME) by young broiler chicks was investigated. The experiment comprised 17 treatments, 16 of which formed a 2 X 4 X 2 factorial design with six replications; the experimental unit was a pen of four male chicks. The factorial treatments consisted of two basal diets (lipogenic and proteogenic ), four levels of cellulose dilution (to cause a range of basal diet intakes), and two feeding periods (10 to 17 and 10 to 24 days of age). The birds were fed ad libitum, feed intake was recorded, and final carcass composition was measured. The 17th treatment comprised 24 pens of chicks killed at the start of the experiment to estimate initial carcass composition. The gross energy of carcass fat and protein was estimated by chemical and physical analysis and by regression analysis, the latter yielded estimates of 24.5 and 39.5 MJ/kg for protein and fat, respectively. Basal diet intake was reduced by more than 50% at the highest level of cellulose dilution and increased by about 60% when the feeding period was extended from 17 to 24 days. Pen weight gain and carcass composition were affected by basal diet intake. The energy retained in the carcass (MJ/W X 75 kg/day) (RE') increased in a linear manner with the intake of TME (MJ/W X 75 kg/day) ( ITME ), the slope of the line being greater for the lipogenic than for the proteogenic diet. Projected back to zero ITME ', the regression lines for pens in positive energy balance gave an estimate of .420 MJ loss, After 7 days on experiment, the energy retained as fat (RE'f) and as protein (RE'p) increased approximately linearly with ITME ', but after 14 days some curvature was apparent, the deposition of protein increasing more rapidly at the lower levels of energy input, and the deposition of fat increasing more rapidly at the higher levels of energy input. The RE'p was only slightly higher on the proteogenic diet than on the lipogenic diet, at the same level of ITME ', but the effect of basal diet on RE'f was considerable. For both diets at RE' = 0 there was gain in body protein accompanied by loss of body fat.

Animal Feed↗
PubMed1983

The effects of precision feeding on the behavior of adult cockerels.

The behavior of 15 precision-fed (PF) cockerels was compared with that of 15 normal (N) and 15 fasted (F) birds. In the 10 min after feeding, the PF birds had a higher incidence of beak movements (P less than .01) than N and F birds. Five PF birds retracted their heads and necks, and 3 made regurgitation-like movements, but the effects were generally slight and fleeting. When a flock of 48 PF birds was observed more casually, only 2 birds showed abnormal behavior. The low incidence of conspicuous abnormal behavior, after precision feeding, in contrast to that reported by Wehner and Harrold (1982), is probably due to the shorter time required to administer the feed.

Animals↗
PubMed1982

The contribution of anorexia to reduced growth in zinc-deficient chickens.

1. It was shown, using a paired-feeding technique, that the growth depression in zinc-deficient chicks was largely caused by the greatly reduced consumption of the deficient diet. 2. Chicks receiving a zinc sulphate solution directly into the crop ate an amount of zinc-deficient diet similar to that of the zinc-deficient diet eaten ty the control chicks; palatability was thus ruled out as the cause of the anorexia. 3. Only chicks receiving the zinc-deficient diet displayed signs of zinc deficiency.

Administration, Oral↗