Effects of protein source and amino acid supplementation on plasma cholesterol in guinea pigs.

The effects of three dietary protein treatments were compared on cholesterol content of plasma lipoprotein fractions and oxidative status of liver lipids in adult guinea pigs. All diets were adequate in soluble dietary fiber and well-balanced in fatty acids providing 30% of total energy. After seven weeks dietary treatments, casein compared to soy protein increased cholesterol in a sub-fraction of LDL (low density lipoprotein) with larger molecular weight and in a combination of this sub-fraction of LDL plus VLDL (very low density lipoprotein) taken together. Supplementation of casein diet with glycine, alanine, arginine and cystine tended to decrease cholesterol in the sub-fraction of LDL with larger molecular weight. There was no effect of dietary treatments on thiobarbituric acid reactive substances in lipids extracted from guinea pig liver likely due to the very high vitamin E and C content of the diets. In addition to counteracting the serum cholesterol elevating effects of dietary cholesterol soy protein also appears to attenuate the hypercholesterolemic effects of dietary saturated fatty acids.

Methane and carbon dioxide emissions from dairy cows in full lactation monitored over a six-month period.

Methane and CO2 emissions from a herd of 118 lactating cows were measured directly by continuous monitoring with an infrared gas analyzer from 24 gas sampling locations. A total of 112 d of gas output was recorded between June 1993 and November 1993. Recordings were integrated at .5-h intervals, so that there were 48 data points for each 24-h period. The mean 24-h CH4 emission per cow was 587 +/- 61.3 L; the range was 436 to 721 L. The mean 24-h CO2 emission per cow was 6137 +/- 505 L, and the range was 5032 to 7427 L. These values were not corrected for gas emissions from stored manure, which contributed 5.8 and 6.1%, respectively, to CH4 and CO2 output under conditions of this experiment.

Sexual expression in container-grown jack pine seedlings.

We assessed the effects of nitrogen, drought and gibberellin A(4/7) on sexual expression of 2- and 3-year-old jack pine (Pinus banksiana L.) seedlings grown in either a 1/3 peat/sand mix or a 3/1 peat/perlite mix. The seedlings were either watered daily (well-watered treatment) or droughted by withholding water from July 13 to August 24 (drought treatment). Half of the plants in each irrigation treatment were sprayed with 200 mg l(-1)gibberellin A(4/7) at weekly intervals from June 28 to August 24; the remaining plants were not sprayed. Each gibberellin treatment was split into three subplots, and each subplot was supplied with nitrogen in the nutrient solution at 3, 100 or 300 mg l(-1) from June 27 to September 11. The drought treatment increased pollen strobilus production, whereas seed strobilus production was higher in well-watered trees than in drought-treated trees in the first year after treatment, but not in the subsequent year. Gibberellin A(4/7) promoted seed strobilus production but not pollen strobilus production in the first year after treatment but had no effect in the second year. Among the nitrogen treatments, the largest proportion of trees bearing pollen strobili was in the 3 mg l(-1) N treatment. Nitrogen supply did not affect seed strobilus production in the first year after treatment, but in the following year, the proportion of trees with seed strobili was higher in the 3 mg l(-1) N treatment than in the 100 and 300 mg l(-1) N treatments. Growing medium had no detectable effect on pollen strobilus production, but in the year following treatment, more trees produced seed strobili in peat/sand than in peat/perlite.

Increased milk production of cows in early lactation fed chemically treated soybean meal.

Holstein cows in early lactation and producing about 35 kg/d of milk were fed TMR for ad libitum intake and 1 kg/d of long alfalfa hay. Soybean meal and soybean meal treated by a novel technique were compared in diets of 15 and 17% CP in a 2 x 2 factorial design. Digestibilities of DM, CP, and ADF were significantly lower for treated soybean meal diets. Mean DMI was about 21 kg/d and was unaffected by treatment. Milk production was significantly increased during wk 7 to 16 of lactation for cows fed treated soybean meal diets. The production of SCM and milk components was greater for cows fed treated soybean meal than for cows fed soybean meal, but the differences were not significant. By wk 16, compared with wk 3 of lactation, the persistency of production of milk and lactose was markedly increased by treated soybean meal. The persistency of milk protein production was 100.5% for cows fed the diet containing treated soybean meal at 17% CP and about 97% for the other diets. The hypothesis that Met supply was limiting secretion of milk protein in cows fed treated soybean meal is discussed.

Hematological and lipid changes in newborn piglets fed milk replacer diets containing vegetable oils with different levels of n-3 fatty acids.

To test if linolenic acid (18:3n-3) from vegetable oils would affect bleeding times and platelet counts in newborns, piglets were used as a model fed milk replacer diets containing 25% (by wt) vegetable oils or oil mixtures for 28 d and compared to sow-reared piglets. The oils tested included soybean, canola, olive, high oleic sunflower (HOAS), a canola/coconut mixture and a mixture of oils mimicking canola in fatty acid composition. All piglets fed the milk replacer diets showed normal growth. Bleeding times increased after birth from 4-6 min to 7-10 min by week 4 (P < 0.001), and were higher in pigs fed diets containing 18:3n-3, as well as in sow-reared piglets receiving n-3 polyunsaturated fatty acids (PUFA) in the milk, as compared to diets low in 18:3n-3. Platelet numbers increased within the first week in newborn piglets from 300 to 550 x 10(9)/L, and remained high thereafter. Milk replacer diets, containing vegetable oils, generally showed a transient delay in the rise of platelet numbers, which was partially associated with an increased platelet volume. The oils showed differences in the length of delay, but by the third week of age, all platelet counts were > 500 x 10(9)/L. The delay in rise in platelet counts appeared to be related to the fatty acid composition of the oil, as the effect was reproduced by a mixture of oils with a certain fatty acid profile, and disappeared upon the addition of saturated fatty acids to the vegetable oil. There were no alterations in the coagulation factors due to the dietary oils. Blood plasma, platelets and red blood cell membranes showed increased levels of 18:3n-3 and long-chain n-3 PUFA in response to dietary 18:3n-3. The level of saturated fatty acids in blood lipids was generally lower in canola and HOAS oil-fed piglets as compared to piglets fed soybean oil or reared with the sow. The results suggest that consumption of milk replacer diets containing vegetable oils rich in 18:3n-3 does not represent a bleeding risk, and that the transient lower platelet count can be counterbalanced by the addition of saturated fatty acids to the vegetable oils.

Effect of dose and modification of viscous properties of oat gum on plasma glucose and insulin following an oral glucose load.

An extract from oats known as oat gum (OG) is composed mainly of the polysaccharide (1-->3) (1-->4)-beta-D-glucan, which is highly viscous in aqueous solution. Viscous polysaccharides are known to attenuate postprandial plasma glucose and insulin responses. The purposes of this study were to determine the dose-response to OG and establish quantitatively the effect of viscosity on plasma glucose and insulin levels of healthy humans consuming 50 g glucose. Increasing the dose of OG successively reduced the plasma glucose and insulin responses relative to a control without gum. Reduction of the viscosity of OG by acid hydrolysis reduced or eliminated the capacity to decrease postprandial glucose and insulin levels. The ability of OG to modify glycaemic response was unchanged following agglomeration in the presence of maltodextrin. Agglomerated gum dispersed smoothly in a drink without formation of lumps, and development of maximum viscosity was delayed. These properties improve palatability. There was a highly significant linear relationship between log[viscosity] of the mixtures consumed and the glucose and insulin responses. The relationship shows that 79-96% of the changes in plasma glucose and insulin are attributable to viscosity, and that changes occur at relatively low doses and viscosities.

Oat beta-glucan reduces blood cholesterol concentration in hypercholesterolemic subjects.

OBJECTIVE: Several studies have indicated that consumption of oat bran lowers blood cholesterol and this effect has been attributed specifically to oat bran's soluble fiber (beta-glucan). This study was designed to test this hypothesis. DESIGN: The purified fibre (oat gum, 80% beta-glucan) was isolated, and agglomerated in the presence of maltodextrin to facilitate dispersion in a drink. Subjects consumed the oat gum (2.9 g beta-glucan), or maltodextrin placebo, twice daily for 4 weeks, in a randomized, cross-over design with a 3 week wash-out between phases. Consumption was equivalent to a daily dose of about 70 g of oat bran. SETTING: The study was with free-living individuals. SUBJECTS: Twenty hypercholesterolemic male and female adults entered, and 19 completed, the study. INTERVENTIONS: Blood lipids from fasting individuals were measured weekly throughout the study. Diet was monitored using 3 day food diaries. RESULTS: There were no significant changes (P > 0.05) in blood lipids during the placebo phase. Mean initial total cholesterol (6.76 +/- 0.13 mmol/l) and low density lipoprotein (LDL) cholesterol (4.59 +/- 0.14 mmol/l) levels fell throughout the oat gum phase, and at week 4 each was reduced 9% relative to initial values (P = 0.0004 and 0.005 respectively). When oat gum was discontinued, total and LDL cholesterol returned to initial levels. There were no significant changes in high density lipoprotein (HDL) cholesterol. Triglyceride levels also remained unchanged except for a singular decrease at week 4 of the oat gum phase relative to the initial value, but not compared to the placebo value. The lowered mean total and LDL cholesterol levels occurred in the absence of any dietary changes. CONCLUSIONS: The main component of the soluble fibre of oats, beta-glucan, significantly reduced the total and LDL cholesterol levels of hypercholesterolemic adults without changing HDL cholesterol.

High beta-glucan oat bran and oat gum reduce postprandial blood glucose and insulin in subjects with and without type 2 diabetes.

The aim of the current study was to characterize the effects of isolated and native sources of beta-glucan, oat gum, and oat bran, respectively, when incorporated into a complete meal. Fasting control subjects and subjects with Type 2 diabetes were fed porridge meals containing either wheat farina, wheat farina plus oat gum or oat bran. Blood samples were collected for 3 h after the test meals and plasma glucose and insulin were measured. Oat bran and wheat farina plus oat gum meals reduced the postprandial plasma glucose excursions and insulin levels when compared with the control wheat farina meal in both control and Type 2 diabetic subjects. This study shows that both the native cell wall fibre of oat bran and isolated oat gum, when incorporated into a meal, act similarly by lowering postprandial plasma glucose and insulin levels. A diet rich in beta-glucan may therefore be of benefit in the regulation of postprandial plasma glucose levels in subjects with Type 2 diabetes.

The influence of the mineral level in drinking water and the thermal environment on the performance and intestinal fluid flux of newly-weaned pigs.

The effects of drinking water containing high levels of dissolved minerals including sulphate (HMW) and a chilled environment on the performance of newly-weaned pigs were evaluated in three replicate 10-d trials. In each trial, 12, 28-d-old pigs were taken from the sow and allocated by weight and litter to treatment groups following a 2 x 2 factorial arrangement of HMW vs low-mineral drinking water (LMW) and normal (heat lamp) vs chilled (21 degrees C) pen temperature. No interactive effects of water mineral level and pen temperature on any of the measurements of health and productivity were found. Pigs given the HMW consumed more water on d 7 to 10 and 1 to 10 (P < .05) and more feed from d 4 to 6, 7 to 10, and 1 to 10 (P < .05), had greater weight gains from d 7 to 10 and 1 to 10 (P < .05), and had higher scour scores on d 4 and 7 (P < .05). Pigs maintained in a chilled environment had lower body weights on d 3, 6, and 10 (P < .05), lower feed conversion efficiency from d 7 to 10 (P < .05) and 1 to 10 (P < .05) and 7 to 10 (P < .01). Pen temperature had no effect on feed intake and scour scores. There was a correlation (P < .05) between feed intake and growth rates throughout the trial, between feed intake and water intake on d 4 to 6, 7 to 10, and 1 to 10, and between water intake and growth rate on d 7 to 10.(ABSTRACT TRUNCATED AT 250 WORDS)

Backfat and carcass composition of piglets fed milk replacers containing vegetable oil compared with sow-reared piglets.

The carcass composition of piglets fed artificial milk was compared to sow-reared piglets. The artificial milk diets contained 25%, by weight, soybean oil or mixtures of canola and high erucic acid rapeseed oil. Both the total lipid and nitrogen (apparent) digestibility of the artificial milk diets was high, even when the dietary oil contained high levels of erucic acid. Sow-reared animals were matched with the piglets receiving the artificial milk by sex and live body weight. On both a relative and an absolute basis, the piglets receiving the artificial milk diets had less carcass fat than sow-reared animals. The per cent nitrogen and ash of the carcasses of sow-reared piglets were significantly reduced compared with piglets eating milk replacer. The fatty-acid patterns of the backfat of the piglets generally resembled the patterns of the dietary lipids. Piglets eating vegetable oil diets had long-chain polyunsaturated fatty acids in their backfat, even though the oils they were consuming did not.

Lipid accumulation in isolated perfused rat hearts has no apparent effect on mechanical function or energy metabolism as measured by 31P NMR.

Male Sprague-Dawley rats were fed diets that contained 20% by weight soybean oil or rapeseed oil (21% and 43% erucic acid) for 7 days. The rapeseed oil diets increased the cardiac triacylglycerol content 5-fold and 25-fold, respectively, above control values. Hearts were removed from the animals and perfused with modified Krebs-Henseleit buffer at 37 degrees C. The calculated rate-pressure product was used as a measure of contractile function. 31P NMR spectra were acquired throughout a protocol that consisted of 12 min control perfusion, followed by 12 min perfusion with 20 microM isoproterenol, 12 min washout, 12 min total global ischemia, and 28 min reperfusion. The steady state levels of creatine phosphate, ATP, intracellular pH, contractile function, and the free energy of ATP hydrolysis (delta GATP) were determined for all three groups of hearts. Isoproterenol more than doubled the rate-pressure product of the hearts on all diets and decreased the concentrations of creatine phosphate and ATP with a concomitant rise in Pi. After global ischemia, creatine phosphate levels recovered fully, ATP levels remained low, and most hearts developed ventricular fibrillation. Changes in intracellular pH were the same for all groups: pH was 7.1 throughout the equilibration and isoproterenol perfusion period, decreased to pH approximately 6.4 during ischemia, and returned to 7.0 during reperfusion. The results indicate that the fat accumulation that occurs in the hearts of rats fed diets rich in high erucic acid rapeseed oil does not interfere with the cardiac high energy phosphate metabolism or contractile function.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum total cholesterol, high-density lipoprotein-cholesterol and triglyceride concentrations in lambs following supplementation with various forms of tocopherol.

A 61-d study involving 40 crossbred lambs evaluated the effect of various forms of tocopherol provided daily in equimolar amounts on total cholesterol, high-density lipoprotein-cholesterol and triglyceride concentrations in the serum of lambs. Thirty-five lambs were allotted to 7 treatment groups of 5 animals each, supplemented with 300 mg tocopherol either as: 1) DL-alpha-tocopheryl acetate; 2) D-alpha-tocopheryl acetate; 3) D-alpha-tocopheryl succinate; 4) D-alpha-tocopheryl polyethylene glycol 1,000 succinate (TPGS); 5) DL-alpha-tocopheryl nicotinate; 6) DL-alpha-tocopheryl nicotinate (150 mg) + 150 mg TPGS; and 7-D-alpha-tocopheryl acetate (150 mg) + 150 mg TPGS mixed with the commercial flock diet. In addition, another group of 5 lambs were used as control (no vitamin E supplementation). Dietary supplementation of various vitamin E sources resulted in no overall treatment effects for total cholesterol, triglycerides or high density lipoprotein-cholesterol. A significant variation was noticed among animals. The levels of all measured serum components varied throughout the experimental period (P < 0.0001). The day x treatment interaction was not significant (P > 0.05) for any serum measured component. The present data strongly suggest that short-term treatment (< 2 mo) with pharmacological oral doses of various forms of vitamin E did not influence serum lipid metabolism of lambs. The data also showed that the bioavailability of alpha-tocopherol is dependent on the form administered. D-alpha-tocopherol acetate is a highly available form, the bioavailability of which is further increased when combined with D-alpha-tocopheryl polyethylene glycol succinate.

Effects of dietary saturated fat on erucic acid induced myocardial lipidosis in rats.

Male Sprague-Dawley rats were fed for one week diets containing 20% by weight fat/oil mixtures with different levels of erucic acid (22:1n-9) (approximately 2.5 or 9%) and total saturated fatty acids (approximately 8 or 35%). Corn oil and high erucic acid rapeseed (HEAR) oil were fed as controls. The same hearts were evaluated histologically using oil red O staining and chemically for cardiac triacylglycerol (TAG) and 22:1n-9 content in cardiac TAG to compare the three methods for assessing lipid accumulation in rat hearts. Rats fed corn oil showed trace myocardial lipidosis by staining, and a cardiac TAG content of 3.6 mg/g wet weight in the absence of dietary 22:1n-9. An increase in dietary 22:1n-9 resulted in significantly increased myocardial lipidosis as assessed histologically and by an accumulation of 22:1n-9 in heart lipids; there was no increase in cardiac TAG except when HEAR oil was fed. An increase in saturated fatty acids showed no changes in myocardial lipid content assessed histologically, the content of cardiac TAG or the 22:1n-9 content of TAG at either 2.5 or 9% dietary 22:1n-9. The histological staining method was more significantly correlated to 22:1n-9 in cardiac TAG (r = 0.49; P less than 0.001) than to total cardiac TAG (r = 0.40; P less than 0.05). The 22:1n-9 content was highest in cardiac TAG and free fatty acids. Among the cardiac phospholipids, the highest incorporation was observed into phosphatidylserine, followed by sphingomyelin. With the addition of saturated fat, the fatty acid composition showed decreased accumulation of 22:1n-9 and increased levels of arachidonic and docosahexaenoic acids in most cardiac phospholipids, despite decreased dietary concentrations of their precursor fatty acids, linoleic and linolenic acids.

Penetration of Celery and Alfalfa Roots by Pratylenchus penetrans as Affected by Temperature.

A greater percentage of females than juveniles or males of P. penetrans penetrated celery roots grown in infested soil at 5, 18, or 30 C; the difference was greatest at 5 C. The time of initial penetration of alfalfa seedlings inoculated with single nematodes on water agar varied with temperature. Females penetrated the seedlings earlier and over a wider range of temperatures than did males or juveniles. The rate of penetration was highest for females. After initial penetration, the penetration rate decreased with time. At 13-28 C, approximately 80% of roots were penetrated by females and only 25-30% by males and juveniles by the end of the experiment.

Myocardial changes in newborn piglets fed sow milk or milk replacer diets containing different levels of erucic acid.

This study was undertaken to determine whether the neonate was more susceptible to the effects of dietary erucic acid (22:1n-9) than the adult. Newborn piglets were used to assess the safety of different levels of 22:1n-9 on lipid and histological changes in the heart. Newborn piglets showed no myocardial lipidosis as assessed by oil red 0 staining, but lipidosis appeared with consumption of sow milk and disappeared by seven days of age. Milk replacer diets containing soybean oil, or rapeseed oil mixtures with up to 5% 22:1n-9 in the oil, or 1.25% in the diet, gave trace myocardial lipidosis. Rapeseed oil mixtures with 7 to 42.9% 22:1n-9 showed definite myocardial lipidosis in newborn piglets, which correlated to dietary 22:1n-9, showing a maximum after one week on diet. The severity of the lipidosis was greater than observed previously with weaned pigs. There were no significant differences among diets in cardiac lipid classes except for triacylglycerol (TAG), which increased in piglets fed a rapeseed oil with 42.9% 22:1n-9. TAG showed the highest incorporation of 22:1n-9, the concentration of 22:1n-9 in TAG was similar to that present in the dietary oil. Among the cardiac phospholipids, sphingomyelin and phosphatidylserine had the highest, and diphosphatidylglycerol (DPG) the lowest level of 22:1n-9. The low content of 22:1n-9 in DPG of newborn piglets is not observed in weaned pigs and rats fed high erucic acid rapeseed oil. The relative concentration of saturated fatty acids was lowered in all cardiac phospholipids of piglets fed rapeseed oils, possibly due to the low content of saturated fatty acids in rapeseed oils. The results suggest that piglets fed up to 750 mg 22:1n-9/kg body weight/day showed no adverse nutritional or cardiac effects.

Erythrocyte membrane lipid alterations in undernourished cerebral palsied children during high intakes of a soy oil-based enteral formula.

Five undernourished children with severe cerebral palsy (CP) were tube-fed sufficient volumes of Isocal to allow rapid weight gain. Isocal provided, on average, 88% of their daily energy intake for at least 25 days. The purpose of our study was to correct the undernutrition and to analyze the major erythrocyte phospholipids before and after feeding periods for possible feeding and disease-related differences. The fatty acid profiles of erythrocyte membranes from CP children were compared with those from 12 healthy children and with the fatty acid composition of the formula. There were no clinical or biochemical indications of essential fatty acid deficiency. The feeding of a soy oil-based formula increased the proportions of 18:2n-6 in the phospholipids. The increases occurred predominantly in phosphatidylcholine followed by phosphatidylethanolamine. Despite such large dietary intakes of soy oil, no changes were observed in the phospholipid concentrations of 20:4n-6, 18:3n-3, 20:5n-3, or in the C22n-6 and C22n-3 fatty acids. These findings are consistent with an inhibition of the delta 6 desaturase by high dietary linoleate.

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.

Influence of dietary undetermined anion on acid-base status and performance in pigs.

Dietary undetermined anion (dUA), calculated as (sodium + potassium + calcium + magnesium) - (chloride + phosphate + sulfate) and expressed in milliequivalents per kilogram, is a major determinant of the acid or alkaline contribution of a diet. Three experiments involving 218 7-wk-old pigs were conducted to investigate the effect of chloride-mediated alterations of dUA. The first two experiments evaluated the effect on pigs of decreasing dUA in either a corn-soybean meal type of diet (expt. 1) or one with a lower potassium content (expt. 2). As dietary chloride increased, and thus as dUA decreased, the rate of growth declined, mediated by changes in feed intake; the effect became more noticeable at extreme dUA levels. The increasing acidogenicity of the diets resulted in a lowering of blood pH, bicarbonate and base excess. The third experiment compared a corn-soybean meal control diet with diets containing two levels of added chloride (7.7 and 9.8 g/kg) at lowered dUA (388 vs. 172 vs. 98 mEq/kg) or at constant dUA (388 vs. 412 vs. 431 mEq/kg). Elevated chloride at constant dUA had no effect on pig performance or acid-base status (p greater than 0.05); however, chloride-mediated decreases in dUA depressed all growth parameters and induced an apparent acidemia. It was concluded that dUA is an important dietary component with the potential to alter pig performance and health. It was also clear that dUA is independent of specific mineral (chloride) effects.

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.

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.