Selection for components related to body composition in mice: correlated responses

Summary Correlated responses were estimated in each of two replicate lines of mice selected within full-sib families for high (HF) or low (LF) 12-week epididymal fat pad weight as a percentage of body weight (epididymal fat pad percentage), or high (HL) or low (LL) 12-week hind carcass weight as a percentage of body weight (hind carcass percentage). Two replicate control lines (RC) were maintained. Correlated traits were measured in each of the 10 generations of selection. Realized (r_{G R}) and offspring-sire genetic correlations generally were in agreement. In HF and LF, 3–6 week postweaning gain (r_{G R} = 0.36±0.04) and feed intake (r_{G R} = 0.50±0.13) had positive correlated responses, but feed efficiency and feed intake/metabolic body size did not change. Positive correlated responses were found for subcutaneous fat pad percentage, body weight-adjusted subcutaneous fat pad weight and fat percentage in the hind carcass (r_{G R}'s were 1.04±0.13, 0.93±0.13 and 0.90±0.08). In the hind carcass, fat-free dry (protein + ash) percentage showed a small negative correlated response, and fat-free dry weight did not change. In HL and LL, the correlated responses for the above traits were generally opposite to those observed in HF and LF. Litter size, percentage of infertile matings, and preweaning mortality showed no consistent correlated responses in any of the lines, but an index of fitness combining the three traits showed a decrease in all four selection treatments.Paper no. 11057 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 criticisms of similar ones not mentioned     

Genetic parameters for carcass weight,conformation and fat in five beef cattle breeds

Profitability of beef production can be increased by genetically improving carcass traits. To construct breeding value evaluations for carcass traits, breed-specific genetic parameters were estimated for carcass weight, carcass conformation and carcass fat in five beef cattle breeds in Finland (Hereford, Aberdeen Angus, Simmental, Charolais and Limousin). Conformation and fat were visually scored using the EUROP carcass classification. Each breed was separately analyzed using a multitrait animal model. A total of 6879–19 539 animals per breed had phenotypes. For the five breeds, heritabilities were moderate for carcass weight (h²=0.39 to 0.48, s.e.=0.02 to 0.04) and slightly lower for conformation (h²=0.30 to 0.44, s.e.=0.02 to 0.04) and carcass fat (h²=0.29 to 0.44, s.e.=0.02 to 0.04). The genetic correlation between carcass weight and conformation was favorable in all breeds (r_G=0.37 to 0.53, s.e.=0.04 to 0.05), heavy carcasses being genetically more conformed. The phenotypic correlation between carcass weight and carcass fat was moderately positive in all breeds (r_P=0.21 to 0.32), implying that increasing carcass weight was related to increasing fat levels. The respective genetic correlation was the strongest in Hereford (r_G=0.28, s.e.=0.05) and Angus (r_G=0.15, s.e.=0.05), the two small body-sized British breeds with the lowest conformation and the highest fat level. The correlation was weaker in the other breeds (r_G=0.08 to 0.14). For Hereford, Angus and Simmental, more conformed carcasses were phenotypically fatter (r_P=0.11 to 0.15), but the respective genetic correlations were close to zero (r_G=−0.05 to 0.04). In contrast, in the two large body-sized and muscular French breeds, the genetic correlation between conformation and fat was negative and the phenotypic correlation was close to zero or negative (Charolais: r_G=−0.18, s.e.=0.06, r_P=0.02; Limousin: r_G=−0.56, s.e.=0.04, r_P=−0.13). The results indicate genetic variation for the genetic improvement of the carcass traits, favorable correlations for the simultaneous improvement of carcass weight and conformation in all breeds, and breed differences in the correlations of carcass fat.     

Restricted index selection in mice designed to change body fat without changing body weight: direct responses

Summary Replicated within full-sib family restricted index selection was conducted for eight generations in mice for high or low epididymal fat pad weight (EF) holding body weight (BW) constant. Pooled realized heritability estimates of index units based on high, low and divergent selection were 0.42±0.20, 0.44±0.19 and 0.42± 0.05, respectively, which were not different from the base population estimate of 0.33±0.10. Realized responses per generation pooled across replicates in the high-fat restricted index lines were in the expected directions for EF (17.5±7.2 mg; P<0.05) and BW (0.03±0.58 g; P>0.05), but responses in the low-fat restricted index lines were discrepant for EF (0.3±5.1 mg; P>0.05) and BW (0.38±0.01 g; P<0.01). Consequently, the realized responses in component traits were decidedly asymmetric (P<0.05). A technique for estimating realized genetic parameters from index selection lines gave realized heritabilities for BW and EF of 0.68±0.04 and 0.45±0.05, respectively, and a realized genetic correlation between BW and EF of 0.93±0.01 compared with base population estimates of 0.43±0.08, 0.49±0.10 and 0.78±0.05, respectively. Possible explanations for the disparity between observed and expected responses in the low-fat restricted index lines include genetic drift, poor estimates of base population parameters, changes in genetic parameters with selection, linkage disequilibrium resulting from selection and asymmetric realized relative index weights.The research reported in this publication was funded by the North Carolina Agricultural Research Service (NCARS), Raleigh, NC 27695-7643, USA. The use of trade names in this publication does not imply endorsement by the NCARS, nor criticism of similar ones not mentioned     

Restricted selection index in mice designed to change body fat without changing body weight: correlated responses

Summary Correlated responses were studied in lines of mice selected for eight generations based on the criterion of a restricted selection index. Two replicate lines were selected in each treatment as follows: HE, high epididymal fat pad weight (EF) with zero change in body weight (BW) at 12 weeks of age; LE; low EF with zero change in BW; and RS, randomly. Correlated responses showed considerable variation between replicates, suggesting that genetic drift was important. Further, correlated responses for most traits were relatively small, probably because of low selection intensity. The HE line responded as expected in component traits of the restricted index. Associated compositional traits in HE responded as predicted since traits correlated with adiposity increased and hind carcass weight did not change significantly. Feed intake increased and feed efficiency (weight gain/feed intake) decreased in HE, as predicted. In contrast, the LE line did not respond in component traits as predicted since EF did not decrease and BW increased. Consequently, LE exhibited little change in traits associated with adiposity, but hind carcass weight, feed intake and feed efficiency increased. Of the correlated responses scored for fitness traits (littering rate, number of days from pairing of mate to littering, litter size and preweaning pup survival rate), significant effects were found for decreased littering rate in LE and increased prenatal survival rate in HE. In summary, correlated responses to restricted index selection generally agreed with expectation when responses in component traits of the index were considered.The research reported in this publication was funded by the North Carolina Agricultural Research Service (NCARS), Raleigh, NC 27695-7643, USA. The use of trade names in this publication does not imply endorsement by the NCARS, nor criticism of similar ones not mentioned     

Correlated responses in development and distribution of fat depots in mice selected for body composition traits

Summary Development of adipose tissue in five depots was investigated in mice selected for high or low 12-week epididymal fat pad weight as a percentage of body weight (HF and LF lines), or high or low 12-week hind carcass weight as a percentage of body weight (HL and LL lines). An unselected control line (RC) was maintained. Hind carcass (HC) and fat pads from subcutaneous hindlimb, subcutaneous forelimb, gonads, kidneys and mesentery were dissected and weighed at 4, 6, 9, 12 or 15 weeks of age. Generally, body weight (BW), daily gain (DG), feed intake (FI), feed efficiency (FE) and feed intake/metabolic body weight (FC) were higher (P0.05) in HF than in LF, and in LL than in HL. HF had more fat (as a percentage of BW) than LF in all depots (P-0.01), and asymmetry (P0.01) was detected for gonadal fat. LL consistently had a higher (P0.01) fat percentage than HL, and asymmetry (P0.01) was observed for perirenal fat. At age of selection, ranking of fat depot weights as a percentage of total fat depot weight was not changed by selection; however, gonadal fat accounted for more of the total fat in HF and LL compared with RC, while the opposite was found in LF and HL. HC percentage was higher (P0.01) in HL than LL, and higher (P0.01) in LF than HF. Growth rate of each fat depot relative to BW was not affected by selection. These results demonstrated that selection for proportion of fat in one depot or for HC percentage changed fat percentage in other depots. However, the rate of fat deposition in each depot relative to body weight gain was not altered.     

Rate,composition and efficiency of growth in mice selected for large and small body weight

Summary Mice selected for high (H₆) and low (L₆) 6-week body weight and a randombred control population (C₁) were characterized for rate, composition and efficiency of growth. Individual body weights were obtained from birth to 8 weeks of age on 682 mice representative of the three lines. Individual whole carcass determinations of water, fat, ash and protein (residual) were obtained for 180 mice sampled weekly from 3–8 weeks of age. Efficiency of feed utilization was estimated from individual body weight and feed consumption data obtained on 189 mice from 3–8 weeks of age. Growth curves for body weight and gain in body weight, constructed by line and sex, showed a temporary retardation of maximum growth rate in the L₆ line, which was attributed in part to an extended depression in growth following weaning. The composition of growth yielded no evidence that the more rapid growth rate in the H₆ line resulted from an increase in fat deposition relative to the other carcass components. A decrease in fat percent at 7 weeks of age in the H₆ and C₁ lines was not evident in the L₆ line until 8 weeks of age. Females had a higher percentage carcass fat than did males during the 4–7 weeks growth period, but this difference was essentially reduced to zero by 8 weeks of age. Percentage water was highly correlated negatively with percentage fat. Percentages protein and ash were essentially constant across lines and ages. A positive relation between rate and efficiency of growth was observed between lines. Consistent sex differences, males more efficient than females, were observed prior to 6 weeks of age, but were not evident in the later (6–8 week) data.

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Zusammenfassung Bei Mäusen, die auf hohes (H₆) und geringes (L₆) 6 Wochen-Körpergewicht selektiert waren, und einer unselektierten Kontrollpopulation (C₁) wurde die Zuwachsrate, die Veränderung des Wasser-, Fett-, Protein- und Aschegehaltes während des Wachstums sowie die Wuchsleistung untersucht. Das Körpergewicht von der Geburt bis zum Alter von 6 Wochen wurde an 682 einzelnen Mäusen, die repräsentativ für die drei Linien sind, festgestellt. Die Ermittlung des Wasser-, Fett-, Asche- und (Rest-)Proteingehaltes der Tiere erfolgte wöchentlich für 180 Mäuse im Alter von 3–8 Wochen. Die Futterverwertung (Wuchsleistung) wurde für 189 drei bis acht Wochen alte Mäuse auf Grund von Einzelgewichten und Futterverbrauch geschätzt.Die Wachstumskurven für Körpergewicht und Gewichtszunahme, nach Linien und Geschlecht zusammengestellt, zeigten bei der L₆-Linie eine zeitweilige Verzögerung der maximalen Zuwachsrate, was z. T. einer längeren Wachstumsdepression nach der Entwöhnung zugeschrieben wird. Es ergab sich kein Beweis dafür, daß die schnellere Wachstumsrate bei der H₆-Linie auf eine Erhöhung der Fetteinlagerung im Verhältnis zu den anderen Komponenten zurückzuführen ist. Ein Rückgang des Fettgehalts, der bei den H₆- und C₁-Linien im Alter von 7 Wochen festzustellen war, wurde bei der Linie L₆ erst nach 8 Wochen sichtbar. Weibliche Tiere hatten im Alter von 4–7 Wochen einen höheren Körperfettgehalt als männliche, im Alter von 8 Wochen war dieser Unterschied aber nicht mehr vorhanden. Der Wassergehalt war in hohem Maße negativ mit dem Fettgehalt korreliert. Die Protein- und Ascheanteile waren im wesentlichen für die Linien und untersuchten Wuchsperioden konstant. Zwischen den Linien wurde eine positive Relation hinsichtlich Wuchsrate und Wuchsleistung festgestellt. Deutliche Geschlechtsunterschiede wurden bis zum Alter von 6 Wochen beobachtet, und zwar wuchsen die Männchen schneller als die Weibchen, später (6.–8. Woche) waren keine Unterschiede mehr feststellbar.

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Paper number 2640 of the Journal Series of the North Carolina State University Agricultural Experiment Station, Raleigh, North Carolina. Supported by Public Health Service Grant GM 11546-05. Computation was supported by NIH Grant No. FR-00011. The senior author was supported by NIH Training Grant No. 2-Tl-GM-296.     

Lipid metabolism of monosodium glutamate obese rats after partial removal of adipose tissue

We analyzed the effects of partial fat pad removal on retroperitoneal and epididymal fat depots and carcass metabolism of control (C) and MSG-obese (M) rats. Three-month-old C and M male Wistar rats were submitted to either partial surgical excision of epididymal and retroperitoneal fat tissue (lipectomy, L) or sham surgery (S) and studied after 7 or 30 days. Retroperitoneal and epididymal tissue re-growth after lipectomy was not observed, as indicated by the low pads weight of the L groups. The lipolysis rate was stimulated in LC7 and LM7, probably due to surgical stress and low insulin levels. In LM7, but not in LC7, in vivo lipogenesis rate increased in retroperitoneal and epididymal fat tissue, as did the diet-derived lipid accumulation in epididymal fat tissue. Although these local increases were no longer present in LM30, this group showed a large increase in the percentage of small area adipocytes in both pads as well as increased carcass lipogenesis rate. The present data showed that the partial removal of fat depots affected the metabolism of control and MSG-obese rats differently. In the obese animals only, it stimulated both local and carcass lipogenesis rate as well as adipocyte differentiation, i.e. responses likely to favor excised tissue re-growth and/or compensatory growth of non-excised depots.     

Application of bioelectrical impedance analysis in prediction of light kid carcass and muscle chemical composition

Carcass data were collected from 24 kids (average live weight of 12.5±5.5 kg; range 4.5 to 22.4 kg) of Jarmelista Portuguese native breed, to evaluate bioelectrical impedance analysis (BIA) as a technique for prediction of light kid carcass and muscle chemical composition. Resistance (Rs, Ω) and reactance (Xc, Ω), were measured in the cold carcasses with a single frequency bioelectrical impedance analyzer and, together with impedance (Z, Ω), two electrical volume measurements (Vol_A and Vol_B, cm²/Ω), carcass cold weight (CCW), carcass compactness and several carcass linear measurements were fitted as independent variables to predict carcass composition by stepwise regression analysis. The amount of variation explained by Vol_A and Vol_B only reached a significant level (P<0.01 and P<0.05, respectively) for muscle weight, moisture, protein and fat-free soft tissue content, even so with low accuracy, with Vol_A providing the best results (0.326⩽R²⩽0.366). Quite differently, individual BIA parameters (Rs, Xc and Z) explained a very large amount of variation in dissectible carcass fat weight (0.814⩽R²⩽0.862; P<0.01). These individual BIA parameters also explained a large amount of variation in subcutaneous and intermuscular fat weights (respectively 0.749⩽R²⩽0.793 and 0.718⩽R²⩽0.760; P<0.01), and in muscle chemical fat weight (0.663⩽R²⩽0.684; P<0.01). Still significant but much lower was the variation in muscle, moisture, protein and fat-free soft tissue weights (0.344⩽R²⩽0.393; P<0.01) explained by BIA parameters. Still, the best models for estimation of muscle, moisture, protein and fat-free soft tissue weights included Rs in addition to CCW, and accounted for 97.1% to 99.8% (P<0.01) of the variation observed, with CCW by itself accounting for 97.0% to 99.6% (P<0.01) of that variation. Resistance was the only independent variable selected for the best model predicting subcutaneous fat weight. It was also selected for the best models predicting carcass fat weight (combined with carcass length, CL; R²=0.943; P<0.01) and intermuscular fat weight (combined with CCW; R²=0.945; P<0.01). The best model predicting muscle chemical fat weight combined CCW and Z, explaining 85.6% (P<0.01) of the variation observed. These results indicate BIA as a useful tool for prediction of light kids’ carcass composition.     

Effect of cryoprotectant and genetic selection for body fat content on embryonic cryosurvival in mice

Lines of mice selected for high (HF) or low (LF) 12-week epididymal fat pad weight as a percentage of body weight were used to investigate the effects of genotype, two cryoprotectants [glycerol (GLY) and propylene glycol (PG)] and genotype x cryoprotectant interaction on cryosurvival of four and eight-cell embryos. Embryos were collected from selection lines and reciprocal crosses of selection lines (HFLF and LFHF) and frozen by established slow-cool methods. Embryos were thawed for 40s at room temperature and then placed in a 37° C waterbath for 1 min. Cryoprotectant was diluted from embryos with either 0.5 M sucrose (GLY-treated) or 1.0 M sucrose (PG-treated). Post-thaw survival was measured as the percentage of embryos developing to 36 h (PTS36), 48 h (PTS48) and hatched blastocyst (PTSHB), respectively. Non-frozen controls were cultured concurrently with frozen embryos. No significant genotype or genotype x cryoprotectant interaction effects were found. Results of the embryo freezing study indicated that selection for high or low fat content did not affect the ability of embryos to survive cryopreservation. There was no indication of embryo heterosis for post-thaw survial. Embryos frozen with GLY survived the freeze-thaw stress significantly better than those frozen in PG (P < 0.05). In vitro development of non-frozen controls at 36 and 48 h did not vary significantly among lines, but in vitro development was significantly different among lines at the hatched blastocyst stage (P < 0.05). Linear contrasts showed that the embryonic genome was responsible for differential in vitro development at the hatched blastocyst stage between these selected lines (HF > LF; P < 0.05); asymmetric response also occurred in that both HF and LF exceeded the unselected control line (P < 0.05).The research reported in this publication was funded by the North Carolina Agricultural Research Service (NCARS), Raleigh, NC 27695-7643. Use of trade names in this publication does not imply endorsement by the NCARS of the products named, nor criticism of similar ones not mentioned Present address: Department of Animal Science, University of Tennessee, Knoxville, TN 37901, USA     

Exogenous hypercortisolism and epididymal fat cell count in young rats.

The influence of two different grades of exogenous hypercortisolism on body weight, epididymal fat pad weight and the total number of fat cells in epididymal fat pads was investigated in young, growing rats. Cortisol, 4-5 mg/kg/day orally from the 7th to the 9th week, reduced body weight gain, whereas epididymal fat pad weight and fat cell content did not differ from those of the control rats. Cortisone acetate, 2.5 mg per 100 g, given subcutaneously for 2 weeks to rats 4-11 week of age caused in the young rat (4-6 weeks) a partial inhibition of the normal increase in body weight, whereas in the young-adult rat (6 weeks and older) an actual decrease of body weight was seen. At both dose levels and - with respect to the higher dose level- in all age groups studied, the weight and fat cell content of the epididymal fat pad were not changed by the cortisone (cortisol) treatment.     

Development of obesity following inactivation of a growth hormone transgene in mice

Mice with a temporally regulatable ovine metallothionein 1a—ovine growth hormone transgene (oMT1a-oGH) were utilized to study the effects of withdrawal of elevated circulating levels of growth hormone (GH) on growth and body composition. The transgene was activated from 21–42 days of age by provision of zinc sulfate in the drinking water. At 42 days, mice were allocated to either activated transgenic (remain on zinc sulfate) or inactivated transgenic (removal of zinc sulfate) groups, and to receive eitherad libitum or restricted (80–90% ofad libitum) access to feed. Non-transgenic control mice were treated similarly. Body weights and intakes were recorded weekly. Mice were killed at 70 d and epididymal and subcutaneous fat pads, trimmed hind carcass and various organs were weighed. The main findings of this study are: (1) food-restricted mice possessing an activated oMT1a-oGH transgene fail to demonstrate increased growth, but exhibit significantly reduced levels of fat (P<0.05) relative to all other genotype x feed level combinations; and (2) inactivation of the oMT1a-oGH transgene, following a period of elevated GH levels, leads to development of obesity as evidenced by two to three fold increases in epididymal and subcutaneous fat pad weights (P<0.01) relative to both activated transgenic and non-transgenic control mice. These large increases in fat deposition also occurred when intake was restricted to 80–90% ofad libitum levels, indicating that metabolic changes independent of intake occur in these inactivated transgenic mice. It is possible that highly elevated production of GH in activated oMT1a-oGH transgenic mice leads to (1) enhanced promotion of preadipocyte differentiation, leading to increased numbers of adipocytes that, upon cessation of oGH production, are available for lipid deposition resulting in obesity, or (2) alterations in production of or responsiveness to insulin, leading to increased fat deposition upon removal of the chronic anti-lipogenic actions of GH. The oMT1a-oGH transgenic mouse line should provide a new genetic model with which to investigate the mechanisms by which growth hormone affects obesity.     

Selectively hydrogenated soybean oil with conjugated linoleic acid modifies body composition and plasma lipids in rats

The present study examined effects of a selectively hydrogenated soybean oil (SHSO) containing about 21% CLA on body composition, adipose depots and organ weights, and plasma lipid profiles in rats. Male Sprague Dawley rats were fed for 6 weeks a purified diet containing 0%, 1%, 3%, and 5% of SHSO. Different levels of SHSO supplementation did not significantly affect growth performance, although there was a trend toward decreased body weight gain with increasing dietary SHSO levels. The weights of inguinal, epididymal, and retroperitoneal adipose depot, but not mesenteric, were significantly influenced by dietary SHSO supplementation (P < 0.05, P < 0.01 and P < 0.001, respectively). Although the absolute weight of body protein in the control rats was higher in SHSO-fed rats, the effect on absolute weight of body protein is diluted and eliminated when the data are adjusted for eviscerated carcass weight as a percentage base. Therefore, as dietary SHSO level increased, body protein as a percentage of carcass weight increased (P < 0.05), although as dietary SHSO level increased, body fat proportion in carcass decreased (P < 0.01). Plasma triglycerides (TG) and total cholesterol (TC) concentrations were beneficially decreased, and HDL-cholesterol (HDL-C) to TC ratio was also beneficially increased by SHSO supplementation (P < 0.05, P < 0.001, and P < 0.01, respectively). However, plasma HDL-C concentration undesirably decreased with dietary SHSO supplementation (P < 0.05). The present study observed that body composition and plasma lipids were beneficially modulated by SHSO supplementation at least 3% levels (0.6% of CLA), and suggested that SHSO is a useful fat source because of the high level of CLA.     

Linking cellular zinc status to body weight and fat mass: mapping quantitative trait loci in Znt7 knockout mice

Zinc transporter 7 (Znt7, Slc30a7) knockout (KO) mice display abnormalities in body weight gain and body adiposity. Regulation of body weight and body fat accumulation is complex, involving multiple genetic and environmental factors. To understand how zinc homeostasis influences body weight and fat deposit and to identify quantitative trait loci (QTLs) that link zinc metabolism to growth and adiposity, we conducted a genome-wide mapping study using male F₂ Znt7 KO mice and wild-type (WT) littermates with a mixed 129P1/ReJ and C57BL/6J genetic background. The mice were fed a semi-purified diet containing 30-mg Zn/kg diet at weaning. Body weights and fat pad weights including epididymal, retroperitoneal, and femoral subcutaneous fat pads were measured at 16 weeks of age. We detected two significant QTLs (p < 0.05) for body weight and fat deposit. One was in the F₂ Znt7 KO population and the other in the F₂ WT population. In Znt7 KO mice, the body weight and fat deposit was significantly linked to a locus on chromosome 7 ranging from 64.3 to 78.3 Mb. In WT mice, a significant linkage of retroperitoneal fat mass was found on chromosome 8 between 14.5 and 63.5 Mb. In addition, several other suggestive QTLs (p < 0.63) for body weight and fat accumulation were detected in Znt7 KO and WT mice. In conclusion, the QTLs identified in this study may provide new hints to uncover the genes linking cellular zinc status to growth and body fat accumulation.     

Genetic Diversity of the Melanocortin 4 Receptor (MC4R) Gene and its Association with Slaughter Traits in the Landes Goose

Melanocortin 4 receptor (MC4R) plays a crucial part in regulating feeding behavior in humans and rodents. We detected two single nucleotide polymorphisms (SNPs; c.108G → A and c.627C → T) in the goose MC4R gene and genotyped 94 Landes geese for association analysis with several carcass traits. Significant associations (P < 0.05) were obtained for c.108G → A with carcass weight, breast muscle percentage, and leg muscle percentage, and for c.627C → T with body weight, carcass weight, semi-eviscerated weight, and eviscerated weight. We re-constructed haplotypes based on the two SNPs and analyzed diplotypes in association with carcass traits, obtaining significant associations with several of the traits. These results suggest that polymorphisms in the MC4R gene could have effects on carcass traits in Landes geese. More study is required to confirm these results.     

A comparison of extrahepatic lipogenesis from a small glucose meal in obob and gold thioglucose obese mice fed low- or high-fat diets with or without the addition of Delta22-5beta-taurocholenic acid

Extrahepatic fatty acid synthesis from a 250 mg meal of [U-(14)C]-glucose was measured in epidymal fat pads and the remaining carcass of hyperglycemic obese (obob), gold thioglucose obese, and nonobese controls under conditions of maximum and minimum lipogenesis. Also assessed was the effect of Delta(22)-5beta-taurocholenic acid, previously shown to inhibit hepatic fatty acid synthesis. Both types of obese and nonobese mice were fed for 6 weeks glucose-based diets containing either 1% corn oil or 40% lard with or without the addition of 0.05% taurocholenic acid. In mice fed 1% corn oil, incorporation of labeled glucose into carcass fatty acids was 25% greater in nonobese than obese mice of either type of obesity. On this diet incorporation of labeled glucose into epididymal fatty acids was reduced 83% in hyperglycemic obese mice compared with nonobese littermates. The corresponding reduction in lipogenesis in gold thioglucose obese mice was only 23% compared with nonobese controls. Feeding 40% lard reduced incorporation of labeled glucose into epididymal and carcass fatty acid 67 to 95% compared with mice fed 1% corn oil in both types of obese and nonobese mice whether or not taurocholenic acid had been fed. Both types of obesity or feeding 40% lard reduced lipogenesis in fat pads to a greater extent than glucose uptake by the pads with the reductions additive. Feeding taurocholenic acid reduced pad weight 30% across strain and obesity status, increased uptake of labeled glucose into epididymal fat pads and increased the percentage of the labeled glucose in the pad recovered as fatty acid in both types of obese and nonobese mice when the diet was 1% corn oil. Similarities and differences between the two obesity models are discussed.     

Effects of high fat diets on hibernation and adipose tissue in Turkish hamsters

Summary The effects of dietary fat saturation and fat content on hibernation and several properties of white and brown adipose tissue (WAT and BAT, respectively) were investigated in Turkish hamsters (Mesocricetus brandti). Male hamsters were housed in a long photoperiod (LD 16:8) at 23°C and fed one of three diets: (1) chow (6.5% fat per weight), (2) chow+13.5% vegetable oil (OIL, 20% fat per weight [largely unsaturated fat]) and (3) chow+13.5% vegetable shortening [SHORTENING, 20% fat per weight (largely saturated fat)]. Five weeks later body weights had stabilized and the animals were transferred to a short photoperiod (LD 8:16) at 3°C. At the peak of the hibernation season (17 weeks) the animals were sacrificed within 24 h of arousal. Chow-fed hamsters had the greatest percentage of animals hibernating and days found torpid compared with the two fat-fed groups, with no differences found between the latter two groups for these measures. There were no differences between hibernating (HIB) and nonhibernating (NON-HIB) hamsters across or within the diet groups for any of the BAT measures [uncoupling protein content, mitochondrial mass, lipoprotein lipase (LPL) activity, and in vivo lipogenesis], nor were there significant effects of the diet on these measures. CHOW-and OIL-fed HIB hamsters showed decreases in body weight. All HIB groups had decreases in each carcass component, several fat pad weights, testes weight, and food intake. No consistent differences in WAT LPL activity or in vivo lipogenesis were found between HIB and NON-HIB hamsters. Feeding saturated high fat diets inhibits hibernation in some species; however, in the present experiment, feeding of both saturated and unsaturated fat-laden diets inhibited hibernation to a similar degree.Abbreviations BAT brown adipose tissue - COA cytochrome-c oxidase - DS dorsal subcutaneus - DSWAT dorsal subcutaneous white adipose tissue - E epididymal - EWAT epididymal white adipose tissue - FFDM fat-free dry mass - HIB hibernating - I interscapular - IBAT intercapsular brown adipose tissue - IS inguinal subeutaneus - ISWAT inguinal subcutaneous white adipose tissue - LPL lipoprotein lipase - NON-HIB non-hibernating - R retroperitoneal - RWAT retroperitoneal white adipose tissue - SDS sodium dodecyl sul - UCP uncoupling protein - WAT white adipose tissue     

The effect of parental divergence on F2 heterosis in winter wheat crosses

Summary In winter wheat (Triticum aestivum L.), the development of a methodology to estimate genetic divergence between parental lines, when combined with knowledge of parental performance, could be beneficial in the prediction of bulk progeny performance. The objective of this study was to relate F₂ heterosis for grain yield and its components in 116 crosses to two independent estimates of genetic divergence among 28 parental genotypes of diverse origins. Genetic divergence between parents was estimated from (a) pedigree relationships (coefficients of kinship) determined without experimentation, and (b) quantitative traits measured in two years of field experimentation in Kansas and North Carolina, USA. These distances, designated (1 -r) and G, respectively, provided ample differentiation among the parents. The 116 F₂ bulks were evaluated at four locations in Kansas and North Carolina in one year. Significant rank correlations of 0.46 (P = 0.01) and 0.44 (P = 0.01) were observed between G and grain yield and kernel number heterosis, respectively. Although (1 -r) was poorly associated with grain yield heterosis, G and midparent performance combined to account for 50% of the variation in F₂ yields among crosses when (1 -r) was above the median value, whereas they accounted for only 9% of the variation among crosses when (1-r) was below the median. Midparent and (1 -r) had equal effects on F₂ grain yield (R ²= 0.40) when G was greater than the median value. A breeding strategy is proposed whereby parents are first selected on the basis of performance per se and, subsequently, crosses are made between genetically divergent parents that have both large quantitative (G) and pedigree divergence (1 -r).Paper No. 12162 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27695-7643, and Contribution No. 89-396-J of the Kansas Agricultural Experiment Station, Manhattan, KS 66506     

Correlated responses in growth and body composition of replicated single-trait and index selected lines of mice

Summary Correlated responses in growth, body composition and efficiency were evaluated in lines of mice selected in the following ways: W⁺T _i ^o , increased six-week body weight (WT6); W ° T _i ⁺ , increased six-week tail length (TL6); W⁺T _i ^– , increased WT6 and decreased TL6; W^–T _i ⁺ , decreased WT6 and increased TL6; M16, increased three-to six-week postweaning gain (PWG). Each of the first four selection treatments had two replicate lines (i = 1, 2) selected for 13 generations and the fifth treatment had one line selected for 30 generations. All lines were derived from a randombred ICR albino population which served as a control. Additional traits studied were three-week body weight and tail length, postweaning gain in tail length, percent body composition (ash, fat, moisture and protein) at six weeks of age, and three-to six-week feed consumption (CONS) and efficiency (EFF = PWG/CONS). Efficiency of body constituent gains (ash, fat, protein and caloric value) were determined by dividing each constituent by CONS. Relative to selection treatments, replicate variation in the array of traits was small and was primarily attributable to the effects of genetic drift; more frequent significant replicate differences among traits in W⁺T^– were associated with a replicate difference in cumulative selection differentials. Selection for different criteria involving WT6 and TL6 did not change the allometric relationship between tail length and body weight in the three-to six-week age interval. The significant divergence between W⁺T ° and W °T⁺ and between W⁺T^– and W^–T⁺ was as expected for WT6 and TL6. Significant asymmetry of selection response between W⁺T^– and W^–T⁺ for WT6 and TL6 was attributed to maternal effects. In agreement with theory, antagonistic index selection generally yielded smaller genetic responses than single trait selection. Positive correlated responses in CONS and EFF were found for M16 and W⁺T °. Significant correlated changes in CONS (positive in W °T⁺ and negative in W^–T⁺) were not accompanied by a significant change in EFF. In contrast, W⁺T^– evinced an increased EFF and no change in CONS. Percent fat increased significantly in W⁺T ° and M16. For W⁺T^o, W⁺T^– and M16, an increased energetic, fat and ash efficiency was observed, whereas M16 exhibited a positive increment in protein efficiency as well. Among selection treatment means, there were high positive correlations between WT6 and fat weight, protein weight, percent fat, CONS and EFF and a high negative correlation between WT6 and percent protein.Paper No.4916 of the Journal Series of the North Carolina Agricultural Experiment Station, Raleigh, N.C. 27607. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Experiment Station of the products named, nor criticism of similar ones not mentioned.     

The composition and properties of beaver (Castor fiber) meat

We analyzed the meat composition of ten females and seven males of sexually mature European beavers (Castor fiber L.). Cutting yield, percentage of particular elements, and chemical composition of the meat were determined. On average, a beaver carcass constitutes 48.6% of beaver body mass and contains 62.8% of meat, 14.5% of fat and 22.4% of bones. The thigh was found to be the largest and most valuable element constituting 33.4% of carcass weight and containing 66.7% of meat. Beaver meat has a high concentration of protein (20.9–21.8% wet wt.) and minerals (1.27–1.31%). The fat was characterized by a high proportion of polyunsaturated fatty acids (48.0–53.1%).