Relationships among carcass weight, acid-base-balance of the blood, meat quality parameters and body composition of cultured rainbow trout (Oncorhynchus mykiss)

The relationshis among carcass weight, acid-base-balance of the blood as an indicator for metabolic load susceptibility, meat quality parameters, and body Composition were investigated in rainbow trout. Examinations were carried out in two replicates using a total of 300 trout from a Danish population. Within replicates, the trout were of aproximately the same age. In Replicate I trout, increasing carcass weight was accompanied by a more arkaline reaction of the blood. Carcass weight was significantly correlated with blood-pH and bicarbonate concentration (.19 and 26). Regression coefficients, however, confirmed only an increase of bicarbonate concentration with increasing carcass weight (b = .013 mmol/L per g, s_b= 0.005). In meat quality parameters, muscular pH₂₄ values decreased linearly in both replicates with increasing carcass weight, as shown by significant correlation estimates (-20 and -.27) and regression coefficients (b = -.0006, s_b=.0002, and b = -.001, s_b= .0003). Relationshis of other meat quality parameters to inmeasing carcass weight were evaluated differently by correlation and regression coefficients. No relationship was found between carcass weight and body composition. In general, correlation estimates describing interrelations between acid-base and meat quality parameters were on a very low level. Independent from carcass weight, there were clearly metabolically loaded and unloaded trout as well as trout with a mixed acid-base-status. Acid-base parameters were significantly correlated with each other. Generally, estimates for correlations between meat quality parameters were on a very low level. Body composition arameters, dry weight and crude fat content were highly significantly correlated (0.47) in Replicate II; in Replicate I there was no interrelation.     

封闭群五指山小型猪主要脏器重量与体重的相关性分析

目的测定封闭群五指山小型猪主要脏器重量和脏器系数,对脏器重量与体重的相关性进行分析,并计算出相应的直线回归方程和多元回归方程。方法实验选用6-10月龄普通级封闭群五指山小型猪30头（其中♂16头、♀14头）,分别测定体重和7个主要脏器重量,计算脏器系数,通过SAS软件进行脏器系数的性别间比较和各脏器重与体重间的相关与回归分析。结果性别间比较,小型猪仅有心脏的脏器系数差异有显著性（P〈0.05）。除公猪的胃脏和母猪的肺脏外,所测脏器重量与体重间均有明显的正相关线性关系;多因素分析显示公猪的肝脏和肾脏,母猪的心脏、肝脏和肾脏对各自体重有影响。结论封闭群五指山小型猪主要脏器系数性别间差异较小,其体重与某些脏器重量存在一定的线性关系。     

Organ weights and organ:body weight ratios of the African white-tailed rat (Mystromys albicaudatus).

Fifty-three adult female and 51 adult male white-tailed rats (Mystromys albicaudatus) were killed with ether and weighed; the spleen, kidneys, liver, heart, lung, pancreas, brain and gonads were dissected free of adhering tissue and weighted. The mean absolute organ weight and organ:body weight ratios by sex and organ were calculated and compared. The male rats were significantly (p less than or equal to 0.05) heavier. The mean weight of the males was 110.0 +/- 23.8 g versus 82.9 +/- 16.1 g for the females. The absolute weights of the heart, liver and kidneys were significantly (p less than or equal to 0.05) greater for the males. The organ:body weight ratios, except for heart and brain (excluding ovary and testicle), were unaffected by sex. The heart to body weight ratio and the brain to body weight ratio were significantly (p less than or equal to 0.05) larger in female rats.     

洞庭湖区社鼠脏器重量的比较

对洞庭湖区社鼠(Niviventer confucianus)野外自然种群脏器的重量指标进行了测定,并比较了其在年龄组、性别、季节及生境间的差异。结果表明,社鼠内脏(心、肺、肝、脾、肾脏)随着年龄组的增加,重量有明显的增加,其重量与体重有极其显著的相关性。两性间的脏器重量指标没有显著性差异。脏器季节变化的共同特征是夏季脏器重量较低,四季间比较,仅有心脏重量有显著的季节变化。生境间心脏和肾脏重量的变化相对较大,达显著水平。参与繁殖与未参与繁殖的雌鼠相比,心、肺、肝、肾脏的各项指标均较高,脾脏则相反,但均未有显著性差异。总的来看,洞庭湖社鼠种群的脏器指标相对稳定,尽管重量指标随着年龄组而增加,受性别、季节、生境及繁殖行为的影响相对较小。     

Maturing patterns of organ weights in mice selected for rapid postweaning gain

Summary Correlated responses to selection for increased 3–6 week postweaning gain in male mice were estimated for seven internal organs (testes, spleen, liver, kidneys, heart, small intestine (S intest) and stomach) weighed at specific degrees of maturity in body weight (37.5, 50.0, 62.5, 75.0, 87.5 and 100%). Correlated responses in organ weights were generally large, but the magnitude and direction of response depended upon whether 1) comparisons were made at the same age, degree of maturity or body weight and 2) absolute or proportional organ weights were used. The selected line (M16) weighed more and had larger organ weights than controls (ICR) when compared at either the same degree of maturity or the same age, indicating positive genetic correlations between body weight and the respective organ weights. Positive correlated responses were found in spleen weight/body weight at all degrees of maturity and in liver and S intest weights as a proportion of body weight at some degrees of maturity. Testes, kidneys, heart and stomach weights as a proportion of body weight had negative correlated responses, though this was consistent only for kidneys across all degrees of maturity. Correlated responses in organ weights adjusted for body weight by covariance analysis were positive for spleen, S intest and stomach and negative for testes and kidneys. Based on the constrained quadratic model, degree of maturity in organ weight relative to degree of maturity in body weight responded positively for testes, kidneys and S intest and negatively for spleen and liver. Selection for increased growth caused negative correlated responses in allometric growth of testes, kidneys, S intest and stomach.Paper No. 10,545 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, 27695-7601. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the products named, nor criticism of similar ones not mentioned     

不同周龄SD大鼠脏器重量及其变化趋势分析

目的分析不同周龄SD大鼠的脏器重量及其变化趋势,为评判药物毒性反应提供理论参考。方法分别选取试验第13、26、52、78和104周对照组动物脑、脾脏、心脏、肺脏、肝脏、肾脏、肾上腺、睾丸、卵巢的重量数据并分析。结果从13～104周SD雌鼠脑、脾脏、心脏、肺脏、肝脏、肾脏、肾上腺、卵巢的重量呈升高趋势。从13～104周SD雄鼠脑、脾脏、心脏、肺脏、肝脏、肾脏重量均重于雌鼠,但雌鼠肾上腺重量、脏体比和脏脑比均显著高于雄鼠。结论本研究首次在国内建立了符合我国实验动物现状的,不同周龄SD大鼠的脏器重量背景数据和参考值范围,并分析了不同周龄SD大鼠脏器重量变化趋势。     

Actions and interactions of growth hormone and insulin-like growth factor-II: body and organ growth of transgenic mice

To characterize long-term actions and interactions of growth hormone (GH) and insulin-like growth factor-II (IGF-II) on postnatal body and organ growth, hemizygous phosphoenolpyruvate carboxykinase (PEPCK)-human IGF-II transgenic mice were crossed with hemizygous PEPCK-bovine GH transgenic mice. The latter are characterized by two-fold increased serum levels of IGF-I and exhibit markedly increased body, skeletal and organ growth. Four different genetic groups were obtained: mice harbouring the IGF-II transgene (I), the bGH transgene (B), or both transgenes (IB), and non- transgenic controls (C). These groups of mice have previously been studied for circulating IGF-I levels (Wolf et al., 1995a), whereas the present study deals with body and organ growth. Growth curves (week 3 to 12) were estimated by regression with linear and quadratic components of age on body weight and exhibited significantly (p < 0.001) greater linear coefficients in B and IB than in I and C mice. The linear coefficients of male I and C mice were significantly (p < 0.001) greater than those of their female counterparts, whereas this sex-related difference was absent in the bGH transgenic groups. The weights of internal organs as well as the weights of abdominal fat, skin and carcass were recorded from 3.5- to 8- month-old mice. In addition, organ weight-to-body weight-ratios (relative organ weights) were calculated. Except for the weight of abdominal fat, absolute organ weights were as a rule significantly greater in B and IB than in I and C mice. IGF-II overproduction as a tendency increased the weights of kidneys, adrenal glands, pancreas and uterus both in the absence and presence of the bGH transgene. Analysis of relative organ weights demonstrated significant (p < 0.05) effects of elevated IGF- II on the relative growth of kidneys (males and females) and adrenal glands (females), confirming our previous report on organ growth of PEPCK-IGF-II transgenic mice. In females, IGF-II and GH overproduction were additive in stimulating the growth of spleen and uterus, providing evidence for tissue-specific postnatal growth promoting effects by IGF-II in the presence of elevated IGF-I     

Spleen and liver weight changes in NZB mice with haemolytic anaemia.

Spleen and liver weights from 998 NZB mice were subjected to computerised multivariate analysis. 3-dimensional graphs relating predicted spleen and liver weights to age and bodyweight were prepared and the relationship of the fitted surface to the histology and pathological autoantibody is discussed. On the basis of spleen weight increase, red-cell destruction throughout the greater part of life seems to be mainly intrasplenic, while intrahepatic destruction does not become important until later, when it is probably a dominant feature in the terminal period of the disease. Only limited organ weight increases occur in breeding females, and it is suggested that pregnancy lessens the effect of the haemolytic disease, the 'protective' effect extending long after the cessation of breeding.     

Cell size increased in tissues from transgenic mice overexpressing a cell surface growth-related and cancer-specific hydroquinone oxidase, tNOX, with protein disulfide-thiol interchange activity

tNOX (ENOX2), a cancer-specific and growth-related cell surface protein with protein disulfide-thiol interchange and hydroquinone (NADH) oxidase activities was overexpressed in a transgenic mouse model. Female transgenic mice grew faster than wild type as did embryonic fibroblast cells prepared from the transgenic mice. The tissue expression of tNOX mRNA was greatest in heart, lung and liver. When these tissues were analyzed for cell size, the cells from the tissues of transgenic animals were, on average, 20% larger in surface area than cells from corresponding wild-type tissues. Also analyzed were cells of intestine, spleen and kidney in which tNOX overexpression was observed but to a lesser extent. Cell size was increased as well with intestine and kidney but less so with spleen. At the end of the study, carcass weights of the transgenic animals were greater than those of wild type. This increase in carcass weight was reflected in an increase in femur weight and thickness in both male and female transgenic mice but not in femur length. Other carcass parameters such as skin weight and body fat or body fluids were unchanged or changes were insufficient to account for the increased carcass weight. The findings are consistent with the property of tNOX observed in studies with cultured cells as contributing to the enlargement phase of cell growth.     

Relationship between carcass composition and first oestrus in Romney ewe lambs

Weaned Romney ewe lambs were grazed at two levels of nutrition from 20 December to 12 April. Both groups were grazed together at a high level of nutrition thereafter. Vasectomized rams were introduced on 1 April. Oestrus occurred in 62/84 (74%) of the low nutrition group and in all 24 of the high nutrition group. The mean date of first oestrus was 3 June for the former and 28 May for the latter. The non-oestrous ewes were killed on 17 July and the others within 5 days of showing oestrus. From each carcass, certain organs (i.e. adrenals, ovaries, thyroid, heart, kidneys, liver, lungs, spleen, stomach and uterus) and various fat depots were dissected out and weighed. In addition, half of the carcass was minced and subsampled for protein and fat analysis. The weight of uterus discriminated between oestrous and non-oestrous animals, as did a linear combination of the weights of lungs, spleen and stomach. The data suggest that fatness or protein content, or the weights of the other organs, are not important indicators of sexual maturity in female sheep.     

Body composition and organ weights of rainbow trout,Salmo gairdneri*

The objectives of the study were to determine the chemical constituents of rainbow trout (Salmo gairdneri) during the first 14 months of life, to study the effects of starvation on the body composition of trout, and to measure organ weights during the first 14 months of life. Body fat and protein content as a percentage of body weight increased with age, the water content declined, and the ash content remained constant during the first 14 months of life. There were no significant differences in body composition between immature male and female rainbow trout. Total body ions as a proportion of ash content decreased until the 10th month and then began to increase. During starvation, fat was used as the primary source of energy while water and ash content increased and protein content remained constant as a percentage of body weight. The gall bladder, liver, and air bladder remained relatively constant as a percentage of body weight during the first year of life. As body weight increased, the relative weight of brain, heart, and digestive system decreased while the gonad and spleen weight increased.     

Visceral organ weights,digestion and carcass characteristics of beef bulls differing in residual feed intake offered a high concentrate diet

This study examined the relationship of residual feed intake (RFI) with digestion, body composition, carcass traits and visceral organ weights in beef bulls offered a high concentrate diet. Individual dry matter (DM) intake (DMI) and growth were measured in a total of 67 Simmental bulls (mean initial BW 431 kg (s.d.=63.7)) over 3 years. Bulls were offered concentrates (860 g/kg rolled barley, 60 g/kg soya bean meal, 60 g/kg molasses and 20 g/kg minerals per vitamins) ad libitum plus 0.8 kg grass silage DM daily for 105 days pre-slaughter. Ultrasonic muscle and fat depth, body condition score (BCS), muscularity score, skeletal measurements, blood metabolites, rumen fermentation and total tract digestibility (indigestible marker) were determined. After slaughter, carcasses and perinephric and retroperitoneal fat were weighed, carcasses were graded for conformation and fat score and weight of non-carcass organs, liver, heart, kidneys, lungs, gall bladder, spleen, reticulo-rumen full and empty and intestines full, were determined. The residuals of the regression of DMI on average daily gain (ADG), mid-test metabolic BW (BW^0.75) and the fixed effect of year, using all animals, were used to compute individual RFI coefficients. Animals were ranked on RFI and assigned to high (inefficient), medium or low groupings. Overall mean ADG and daily DMI were 1.6 kg (s.d.=0.36) and 9.4 kg (s.d.=1.16), respectively. High RFI bulls consumed 7 and 14% more DM than medium and low RFI bulls, respectively (P<0.001). No differences between high and low RFI bulls were detected (P>0.05) for ADG, BW, BCS, skeletal measurements, muscularity scores, ultrasonic measurements, carcass weight, perinephric and retroperitoneal fat weight, kill-out proportion and carcass conformation and fat score. However, regression analysis indicated that a 1 kg DM/day increase in RFI was associated with a decrease in kill-out proportion of 20 g/kg (P<0.05) and a decrease in carcass conformation of 0.74 units (P<0.05). Weight of non-carcass organs did not differ (P>0.05) between RFI groups except for the empty weight of reticulo-rumen, which was 8% lighter (P=0.05) in low RFI compared with high RFI bulls. Regression analysis indicated that a 1 kg DM/day increase in RFI was associated with a 1 kg increase in reticulo-rumen empty weight (P<0.05). Of the visceral organs measured, the reticulo-rumen may be a biologically significant contributory factor to variation in RFI in beef bulls finished on a high concentrate diet.     

Dry season weight losses in Red Sokoto (Maradi) goats reared in the Sahel region of Northeastern Nigeria

Weight losses in body, carcass, skin and liver were determined during the advanced periods of the West African Sahel dry seasons-December to May, when the greatest offtake of livestock for slaughter occurs. Data used were from 131 Red Sokoto goats slaughtered in the Maiduguri abbatoir from 1981 to 1982. Month of slaughter greatly influenced all traits. Weights declined as the dry season advanced with its characteristic rise in ambient temperatures. Weight losses were about 18%, 22%, 45% and 57% from December to May for body, carcass, skin and liver respectively. Percentage slaughter weights were closer to the lower uneconomical limit (45%) than to the upper (65%). As percentages of body weight, declines were from 7.07% to 4.89% and 5.55% to 2.79% for skin and liver weights respectively. Results obtained especially from the allometric regressions of liver and body weights do not quite uphold a prevailing opinion that animals slaughtered during these periods are largely immature. Correlations declined till April, being lowest (P>0.05) in March. Regression coefficients were lower and intercepts higher from January to March. Weight declines must have been largely due to starvation and dehydration. Direct and indirect effects of high ambient temperatures on growth of animals are discussed. Conditions for animal-production could be improved by settling the pastoralists and by avoiding the present necessary seasonal movement of livestock through the provision of forages and water all year round. It would also help if means of meat preservation could be devised and so enable offtake for slaughter to shift to the rainy seasons of the year.     

Joint analysis of beef growth and carcass quality traits through calculation of co-variance components and correlations

A joint growth-carcass model using random regression was used to estimate the (co)variance components of beef cattle body weights and carcass quality traits and correlations between them. During a four-year period (1994-1997) of the Australian "southern crossbreeding project", mature Hereford cows (N = 581) were mated to 97 sires of Jersey, Wagyu, Angus, Hereford, South Devon, Limousin, and Belgian Blue breeds, resulting in 1141 calves. Data included 13 (for steers) and 8 (for heifers) body weight measurements approximately every 50 days from birth until slaughter and four carcass quality traits: hot standard carcass weight, rump fat depth, rib eye muscle area, and intramuscular fat content. The mixed model included fixed effects of sex, sire breed, age (linear, quadratic and cubic), and their interactions between sex and sire breed with age. Random effects were sire, dam, management (birth location, year, post-weaning groups), and permanent environmental effects, and their interactions with linear, quadratic and cubic growth, when possible. Phenotypic, sire and dam correlations between body weights and hot standard carcass weight and rib eye muscle area were positive and moderate to high from birth to feedlot period. Management variation accounted for the largest proportion of total variation in both growth and carcass traits. Management correlations between carcass traits were high, except between rump fat depth and intramuscular fat (r = 0.26). Management correlations between body weight and carcass traits during the pre-weaning period were positive except for intramuscular fat. The correlations were low from birth to weaning, then increased dramatically and were high during the feedlot period.     

Immunostimulatory polysaccharides from Chlorella pyrenoidosa. A new galactofuranan. measurement of molecular weight and molecular weight dispersion by DOSY NMR

Fractionation of the hot water extract of Chlorella pyrenoidosa was performed using a combination of ethanol precipitation, size exclusion chromatography, and anion exchange chromatography. One fraction contained a new polysaccharide, and this compound was shown to be a 1-->2-linked beta-d-galactofuranan from its 1D and 2D (1)H and (13)C NMR spectra, with a molecular weight of 15 kDa from DOSY NMR measurements. A number of other fractions were shown to have the same repeating unit as the previously identified arabinogalactan. However, arabinogalactans from different fractions were shown by DOSY NMR to have different molecular weights, which ranged from 27 to 1020 kDa. Agreement with molecular weights measured for some of these fractions by SEC-MALS was very good, further confirming the relationship established by Viel et al. between molecular weights of neutral polysaccharides and self-diffusion coefficients. The smaller molecular weight polysaccharides, the galactofuranan and the 27 and 50 kDa arabinogalactans, were shown to be close to monodisperse by analysis of the distributions of the self-diffusion coefficients for the polymers. The larger arabinogalactans had considerable variation in their molecular weights (188 +/- 109 kDa and 1020 +/- 370 kDa). Only the two larger arabinogalactans showed immunostimulatory activity.     

Correlated response in male and female sterility to selection for pupa weight in Tribolium castaneum

Summary The correlated responses in male and female sterility to 50 generations of individual selection for pupa weight in Tribolium were analyzed. Two replicate lines (S-lines) were selected for heavier pupa weight and stabilizing selection for pupa weight was practiced in two replicate control lines (C-lines). There was close agreement between replicates in both sets of lines for direct and correlated responses. The rate of inbreeding has been constant for all lines (approximately 0.5% per generation).Regression of generation means for pupa weight on generation of selection indicated a significant linear regression in the direct response for both lines. The linear increases of 46 and 55 g. per generation in the S-lines accounted for 98% of the variation among generations and the linear decreases of 5 and 10 g. per generation in the C-lines accounted for 70–90% of the variation in the generation means.Maximum likelihood estimators were used to calculate the frequency of male and female sterility for each generation and line. Average sterility in the base population ranged from about 4 to 12% for both sexes. Polynomial regressions of percent sterility on generation of selection showed that quadratic and higher order regressions were occasionally significant but accounted for a relatively small fraction of the total variation. In the two S-line replicates, linear regression coefficients of percent sterility on generation number were 0.16±.09 and 0.20±.07 for males and 0.72±.08 and 0.54±.08 for females, suggesting a larger correlated response in female than in male sterility. In the C-lines, linear regression coefficients were 0.02±.08 and –.12±.05 for males in the two replicates and –.05±.05 and –.05±.05 for females. Estimates of realized genetic correlations between pupa weight and sterility in the S-lines ranged from 0.04 to 0.14 for males and from 0.14 to 0.37 for females when the heritability of sterility was allowed to take on values from 0.05 to 0.25.Supported by NSF Grants G-1238 and GB-5987, NIH Grant GM-16074 and NIH Fellowship 1 FO2 GM4 5130-01.     

The relationship between organ weights and body weights, facial dimensions, and dental dimensions in a population of olive baboons (Papio cynocephalus anubis)

Questions concerned with the relationship between organ weights and body weight on an intraspecific level are best answered by using a sample of animals collected in the wild from a single locale during a single season. The organ weights and body weights for this study were obtained from the necropsy reports prepared in the field (Athi Plain, Kenya) by H. C. McGill, Jr. on 36 adult animals (18 males and 18 females). Dental and facial measurements were taken by M.I. Siegel. In order to avoid erroneous results produced by statistical treatment of combined sex samples of sexually dimorphic species, data on the sexes were analyzed separately. Means and standard deviations are reported for selected organ weights and body dimensions (heart, lung, liver, spleen, kidney, adrenal, brain, and pancreas weights, crown–rump length, crown–heel length, head circumference, chest circumference, and body weight). All of the above measures were significantly (p<0.05) different between the sexes. Logarithms of these measures were significantly correlated with the logarithm of body weight in males for heart, lung, liver, spleen, kidney, and adrenal weights, crown–heel length, and head and chest circumference, and in females for crown–heel length, heart, liver, and kidney weights. Partial correlational analysis, removing the effects of body size (weight), showed mostly negative correlational relationships between dental and visceral dimensions. Most of the correlations between facial and visceral dimensions were negative. Allometric equations were calculated for the dental, facial, and visceral dimensions versus body weight, and are compared with prior published results.     

Maslinic acid as a feed additive to stimulate growth and hepatic protein-turnover rates in rainbow trout (Onchorhynchus mykiss)

Maslinic acid is a triterpene present in a considerable proportion in solid residues from olive-oil production. In the present work the effects of maslinic acid on growth, protein-turnover rates and nucleic-acid concentration on liver were investigated in the rainbow trout. Five groups of 120 fish of a mean body mass of 20 g were fed for 225 days with diets containing 0, 1, 5, 25 and 250 mg of maslinic acid per kg diet. At the end of the experiment, whole-body and liver weight and growth rate of trout fed with maslinic acid were higher than controls. The highest weight increase was registered for the group fed 250 mg kg(-1), representing a 29% increase over controls. The total hepatic DNA or liver cell hyperplasia levels in trout fed with 25 and 250 mg of maslinic acid kg(-1) were 37% and 68% higher than controls. Also in these same groups of trout, fractional and absolute hepatic protein-synthesis rates were significantly higher than in control, and significant increments in hepatic protein-synthesis efficiency and protein-synthesis capacity were reported. In close agreement with these results, microscopy studies showed that trout fed on 25 and 250 mg kg(-1) hepatocytes appeared to be more compact, with a larger rough-endoplasmic reticulum and larger glycogen stores than controls. These results suggest that maslinic acid can act as a growth factor when added to trout diet.     

Weight of food and time required to satiate brown trout, Salmo trutta L.

Brown trout of different weights (range 8-358 g) were fed to satiation at fifteen different water temperatures (range 3.8–21.6°C. Both the weight of the trout (Wg) and the water temperature (T°C) affected the maximum weight of food (Q mg) consumed in a meal, and the relationship between the three variables was well described by a multiple regression equation which can be used to estimate the value of Q (with 95% confidence limits) for trout of different weights at different temperatures between 3.8°C and 21.6°C. The satiation time (with 95% confidence limits) can also be estimated from a multiple regression equation for trout of different weights at temperatures between 6.8°C and 18.1°C. Estimates from the multiple regression equations were applicable to a wide range of food organisms with the exception of larvae ofTenebrio molitor (mealworms). Appetite (measured by voluntary food intake) varied with temperature and was greatest between 13.3°C and 18.4°C. From comparisons with the results of other workers, it was concluded that the maximum amount of food consumed in a meal may provide sufficient calories for both the daily metabolic requirements and the daily maintenance requirements of a trout at temperatures between 3.8°C and 18.4°C, but not at temperatures above 18.4°C.     

Study of fetal organ growth in Wistar rats from day 17 to 21

A total of 1633 Wistar rat fetuses was used to determine weights of the fetus and several fetal organs on days 17 to 21 of gestation. Heart, lung, liver, kidney, stomach, intestine, brain, femur, thyroid and adrenal weights were recorded. Growth curves of the whole body and organs were calculated. A linear semi-log relationship between organ weight and day of gestation was shown. The doubling weight times were 1.5 days for whole bodies and for organs they ranged between 0.9 (spleen) and 3.4 (adrenals) days. A correlation between the rate of organ growth and the start of the organ function was observed.