Significant Line Effects Research Articles

Effects of heat stress on cyto(chemo)kine and inflammasome gene expression and mechanical properties in isolated red and white blood cells from 4 commercial broiler lines and their ancestor jungle fowl

Commercial broilers have been selected for high growth rate and productivity; however, this has negatively impacted their susceptibility to heat stress (HS). Insight into the molecular mechanisms underlying this vulnerability can help design targeted strategies for improvement of HS tolerance. Red blood cells (RBC) and white blood cells (WBC) were isolated from red jungle fowl and 4 lines of commercial modern broilers. Lines A and B are considered standard-yielding lines, whereas Lines C and D are high-yielding. Cells were cultured at either 37°C or 45°C for 2 h to induce heat stress (HS). Gene expression of cytokines, chemokines, and inflammasome components were measured. Heat shock proteins 27 and 70 (HSPs) in RBC were significantly affected by line (P < 0.05), whereas HSP27 and 60 were affected by temperature (P < 0.05). In WBC, there was a significant line effect on HSP gene expression (P < 0.05), and a significant increase (P < 0.05) in HSP90 in Line D in HS compared to TN conditions. In RBC, there was a main effect of HS on TNFα, CCL4, and CCLL4 (P < 0.05). HS significantly increased IL-8L1 (>30-fold, P < 0.0001) in Line C. Inflammasome genes (NLRP3, NLRC5 and NLRC3) were significantly affected by the line studied (P < 0.05). In WBC, the effect of line was significant for all cytokines, chemokines, and inflammasome components studied (P < 0.05). To examine the mechanical properties of isolated RBC from the 4 commercial lines and jungle fowl, RBC were placed into nematic liquid crystals, where Lines B and D were the most strained, and Line A and the jungle fowl were the least strained. Together, these findings indicate not only the dynamic nature of circulating cells, but the differences in the stress and inflammatory response among commercially available lines and their common ancestor. These profiles have the potential to serve as a future marker for stress responses in broilers, though further study is warranted.

Effect of expression of PPARG, DNM2L, RRAD, and LINGO1 on broiler chicken breast muscle satellite cell function

Disorders affecting the breast muscle of modern commercial broiler chickens have increased in recent years. Wooden Breast (WB) myopathy is characterized by a palpably hard breast muscle with increased fat deposition. WB is a metabolic disorder with lipid accumulation considered to be a primary causal factor. The adult myoblasts, satellite cells, are a partially differentiated stem cell population and primarily function in muscle growth and regeneration. The satellite cells also express adipogenic genes. The objective of this study was to determine the expression of the adipogenic genes PPARG, DNM2L, RRAD, and LINGO1 in commercial Ross 708 (708) and Randombred (RBch) satellite cells. RBch satellite cells are from commercial 1995 broilers before WB and 708 broilers are a modern commercial line. In general, expression of these genes was different between the 708 and RBch satellite cells during proliferation and differentiation. Expression of PPARG and RRAD were both significantly increased during both proliferation and differentiation in the 708 cells (P ≤ 0.05). Knocking down the expression of these genes with small interfering RNAs did not greatly affect either proliferation or differentiation. Lipid accumulation was affected by the knockdown of these genes with significant line effects from 48 h of proliferation through 72 h of differentiation. In general, 708 satellite cells had higher lipid levels. Knockdown treatment effect was specific to each gene. The results demonstrate that lipid biosynthesis has been affected in breast muscle satellite cells which may contribute to the increased lipid deposition in modern day commercial broiler chickens.

Do thermal acclimation and an acute heat challenge alter myonuclear domain of control- and fast-growing quail?

Efforts to determine physiological traits that may render species resilient or susceptible to changing global temperatures have accelerated in recent years. Temperature is of critical importance to biological function; thus, climate change has the potential to severely affect all levels of biological organization in many species. For example, increases in environmental temperatures may alter muscle structure and function in birds. Myonuclear domain (MND), an under-studied aspect of avian muscle physiology that changes in response to thermal stress, is defined as the amount of cytoplasm within a muscle fiber that each nucleus is responsible for servicing. Here, we used two random bred lines of Japanese quail (Coturnix japonica) representing examples of control and fast growth rates. We used a factorial design to administer four treatment combinations to each line - an initial period of either heat-stress acclimation (Acclimation) or no acclimation (Not acclimated) followed by either a heat-stress challenge (HS) or no challenge (NC) after week 8 of age - to determine the effects of thermal acclimation and acute thermal stress on quail MND. We found a significant interaction between line * final treatment with fast-growing, HS birds demonstrating the lowest numbers of nuclei per mm of fiber, and Acclimated control-growing birds showing the highest numbers of nuclei per mm of fiber. There was a significant effect of line on MND with the fast-growing line having larger MNDs. Initial treatment with Not Acclimated birds showed larger MNDs. Additionally, control growing quail demonstrated positive correlations with fiber size, whereas fast growing quail did not. This may mean that nuclei in larger fibers of fast-growing quail may be functioning maximally, and that increases in temperature may also demonstrate similar effects.

PSIII-9 The Effect of Sire Line on Reproductive Performance During Lactation

Abstract The objective of this study was to estimate the effect of sire line on sow and piglet performance during lactation. Commercial Landrace x Large White females (n = 60) were bred to one of the following sire lines: a purebred Duroc line (Line S1), a synthetic (Line S2), or purebred Duroc (Line S3) from a different genetic source. Matings were balanced by line and parity. Females were fed a common gestation and lactation diet during these respective phases. Sow and piglet data were analyzed as a completely randomized design using the GLM procedure of SAS. Results show that, during lactation, females bred to line S3 lost significantly (P = 0.01) more BW (-16.93 ± 3.56 kg) than females bred to line S2 (-2.00 ± 3.50 kg). However, no evidence of a difference (P = 0.18) in BW loss was detected between females bred to line S3 (-16.93 ± 3.56 kg) vs. Line S1 (-7.90 ± 3.56 kg). Further, sows bred to line S3 weaned significantly (P = 0.03) more piglets (12.0 ± 0.28) than females bred to line S2 (10.9 ± 0.27), but not (P = 0.1) compared to females bred to line S1 (11.7 ± 0.27). No significant effect of line (P &amp;gt; 0.05) or parity (P &amp;gt; 0.05) on total number of piglet’s born, number born alive, number of stillborn piglets, or preweaning mortality was detected. The number of mummified fetus tended to be lower in line S2 (0.17 vs 0.66; P = 0.079) and line S3 (0.12 vs 0.66; P = 0.051) sows compared with line S1 sows, respectively. In conclusion, sire line did not have a significant effect on total number born, number born alive, number stillborn, or preweaning mortality. However, females bred to line S3 lost significantly more BW during lact but weaned significantly more piglets than females bred to line S2.

Divergent genotypes for fatness or residual feed intake in Angus cattle. 3. Performance of mature cows

This experiment evaluated the productivity of 500 Angus cows that differed in genetic merit for either subcutaneous rib fat depth (Fat) or residual feed intake (RFI) based on estimated breeding values (EBVs) and managed under two levels of nutrition. Reproductive rate over four calving opportunities in mature cows and growth performance of progeny to weaning was assessed. Level of nutrition significantly affected all body composition traits for both Fat and RFI line cows. Cows on High-Nutrition were 14–16% heavier (P &lt; 0.001) than those on Low-Nutrition. Differences in EBVs for fatness were reflected in phenotypic fatness at maturity. High-RFI line cows were fatter for both scanned rump (P8) and rib (RIB) fat depth relative to their Low-RFI contemporaries. Of those cows that were lactating, there was no significant effect of line or nutrition on pregnancy rate or days to calving (DC). There was, however, a trend (P &lt; 0.1) in the Low-Fat line cows towards longer DC compared with the High-Fat line cows. There was no significant effect of either line or nutrition on calf birthweight. Calves with mothers on High-Nutrition were 8% heavier at weaning (P &lt; 0.001) than those on Low-Nutrition. Lower EBVs for RFI was associated with higher 200-day growth EBV and heavier calves at weaning. Current carcass BREEDPLAN EBVs can be used to select for changes in cow body composition if desired. In this experiment, Angus cows selected for lower RFI or with below-average fatness EBV and had raised a calf at every previous opportunity were not compromised in pregnancy rate or DC at maturity under varying nutrition such as can be experienced during normal seasonal conditions in southern Australia. However, selection for lower RFI was associated with lower weaning rate (P &lt; 0.05), which warrants further investigation to confidently predict the implications for commercial cattle production.

Inbreeding and thermal adaptation inDrosophila subobscura

Using a well-adapted Drosophila subobscura population (Avala, Serbia), a drastic experiment of inbreeding was carried out to assess whether the expected level of homozygosity could be reached or if other evolutionary forces affected the process. In general, no significant changes of inversion (or arrangement) frequencies were detected after 12 brother-sister mating generations. Furthermore, no significant differences were obtained between observed and expected (under the inbreeding model) karyotypic frequencies. Thus, these results seemed to indicate that the main evolutionary factor in the experiment was inbreeding. However, in the G12 generation, complete chromosomal fixation was reached only in two out of the eight final inbred lines. In these lines, the chromosomal compositions were difficult to interpret, but they could be likely a consequence of adaptation to particular laboratory conditions (constant 18 °C, food, light period, etc.). Finally, in a second experiment, the inbred lines presented higher fertility at 18 °C than at 13 °C. Also, there was a significant line effect on fertility: inbred line number 6 (A1, J1, U1+2; U1+2+6, E8, and O3+4+7) presented the highest values, which maybe the result of an adaptation to laboratory conditions. Thus, the results obtained in our experiments reflect the adaptive potential of D. subobscura inversions.

Behavioral effects of bidirectional selection for behavior towards human in virgin and lactate Norway rats

Although numerous studies have demonstrated strong differences in behavioral, hormonal and neurobiological characteristics between male rats selected for elimination (tame) and enhancement (aggressive) of aggressiveness towards humans, few studies have examined changes in female behavior under this selection. The objective of the current work was to evaluate the effects of bidirectional selection for aggressiveness towards humans on behavioral profiles of virgin and lactating rats compared with the behavior in tame, aggressive and unselected (wild-type) females. The behavior of virgin females was studied using the light-dark box, the startle response test and the modified glove test. Tame females were less anxious and more tolerant towards humans than unselected and aggressive rats. Principal component analysis of all behavioral parameters produced three independent factors, explaining 66.37% of the total variability. The measures of behavior towards humans and the measures of anxiety mainly loaded on PC1 (first principal component) which separated the tame females from the unselected and aggressive ones. These data suggest the genetic correlation between the selected behavior towards humans and anxiety-related behavior in virgin rats. No significant effect of line was found for PC2 scores, associated with risk assessment behavior. Measurements of freezing behavior mainly loaded on PC3, and this component separated rats of different genetic groups from each other. The behavior of lactating rats was studied in maternal defense and pup retrieval tests. Females of selected lines did not significantly differ in behavioral measurements of these tests and were characterized by higher maternal motivation than unselected rats. It is suggested that long-term breeding of tame and aggressive rats in captivity has reduced the threshold for maternal behavior.

Effect of soybean meal substitution by different concentrations of sunflower meal on egg quality traits of white and coloured dwarf dam lines

1. The effect of soybean meal substitution by different concentrations of sunflower meal on egg quality traits of white and coloured dwarf dam lines was investigated. 2. A total of 144 dwarf hens (38 weeks of age) from the same hatch were randomly divided into 12 groups of 12 birds (4 dietary treatments × 3 replicates). 3. A 2 × 4 factorial design was used to study the effect of 2 lines (Factor A) and substitution of soybean meal (SBM) with 4 concentrations (0, 10, 15 and 20%) of sunflower meal (SFM) [Factor B] on egg quality traits of dwarf dam line hens. 4. All the diets were designed to be isocaloric (11⋅3 MJ ME/kg) and isonitrogenous (180 g/kg crude protein) The duration of the experiment was 12 weeks. 5. Analysis of variance indicated a highly significant line effect. There were non-significant effects of substitution of soybean meal with different concentrations of sunflower meal on egg quality traits except for Haugh unit. 6. White plumaged dwarf broiler breeder dam line produced significantly fewer, but larger, eggs than coloured dwarf dam line hens.

Abundant genetic variation in transcript level during early Drosophila development.

Variation in gene expression may underlie many important evolutionary traits. However, it is not known at what stage in organismal development changes in gene expression are most likely to result in changes in phenotype. One widely held belief is that changes in early development are more likely to result in changes in downstream phenotypes. In order to discover how much genetic variation for transcript level is present in natural populations, we studied zygotic gene expression in nine inbred lines of Drosophila melanogaster at two time points in their development. We find abundant variation for transcript level both between lines and over time; close to half of all expressed genes show a significant line effect at either time point. We examine the contribution of maternally loaded genes to this variation, as well as the contribution of variation in upstream genes to variation in their downstream targets in two well-studied gene regulatory networks. Finally, we estimate the dimensionality of gene expression in these two networks and find that-despite large numbers of varying genes-there appear to be only two factors controlling this variation.

Autosomal variation for male body size and sperm competition phenotypes is uncorrelated in Drosophila melanogaster

Correlations between male body size and phenotypes impacting post-copulatory sexual selection are commonly observed during the manipulation of male body size by environmental rearing conditions. Here, we control for environmental influences and test for genetic correlations between natural variation in male body size and phenotypes affecting post-copulatory sexual selection in Drosophila melanogaster. Dry weights of virgin males from 90 second-chromosome and 88 third-chromosome substitution lines were measured. Highly significant line effects (p<0.001) documented a genetic basis to variation in male body size. No significant correlations were identified between male body size and the components of sperm competitive ability. These results suggest that natural autosomal variation for male body size has little impact on post-copulatory sexual selection. If genetic correlations exist between male body size and post-copulatory sexual selection then variation in the sex chromosomes are likely candidates, as might be expected if sexually antagonistic coevolution was responsible.

Conceptus development during blastocyst elongation in lines of pigs selected for increased uterine capacity or ovulation rate1,2

Lines of pigs selected for increased uterine capacity have improved conceptus survival, whereas pigs selected for increased ovulation rate have decreased conceptus survival relative to an unselected control line. The objective of this study was to evaluate conceptus development during blastocyst elongation as a potential contributing factor to differences in conceptus survival rate among these pig lines. Conceptuses were recovered from pregnant control, uterine capacity, and ovulation rate line gilts at d 10 and 12 of gestation. At d 10 of gestation, conceptus morphologic diversity was assessed by comparing within-litter average conceptus diameter and the standard deviation of conceptus diameters. At d 12 of gestation, conceptus morphologic diversity was assessed by comparing blastocyst populations obtained from individual gilts. Real-time PCR analyses for transcripts involved in steroidogenesis, cellular differentiation, and immune responsiveness were performed on spherical, ovoid, and filamentous conceptuses recovered from these selection lines. Uterine flushings were also assayed for total protein and estradiol-17beta at d 10 and 12 of gestation. Morphological data were analyzed using ANOVA with the fixed effects of line, farrowing season, and their interactions. Conceptus mortality, uterine flushing, and real-time PCR data were analyzed using ANOVA with the fixed effects of line, day or blastocyst morphology, farrowing season, and their interactions. Conceptus mortality, measured as the ratio of conceptus recovery to ovulation rate, was not different between the lines on d 10 and 12 of gestation. There were no significant line effects for conceptus morphologic diversity at d 10 and 12 of gestation. Expression of transcripts associated with steroidogenesis (steroidogenic acute regulatory protein, cytochrome P450 side chain cleavage, and aromatase), cellular differentiation (cytokeratin-18 and vimentin), and immune responsiveness (interleukin-1beta) in spherical, ovoid, and filamentous conceptuses was not different between the lines. Furthermore, protein and estradiol-17beta in uterine flushings at d 10 and 12 of gestation were not different between the selection lines. These findings indicate limited, if any, deviations between these lines of pigs in conceptus development during blastocyst elongation and suggest that mechanisms involved in generating line differences in survival rate likely are manifested later in gestation.

Chronic increase of dietary l-tryptophan decreases gentle feather pecking behaviour

Many studies show the involvement of the serotonergic (5-HT) system in the performance of abnormal behaviour in both human and animals. Recently, we showed that acute reduction of 5-HT turnover in the forebrain, increased gentle and severe feather pecking behaviour in chicks from a high (HFP) and low feather pecking (LFP) line of laying hens, suggesting that the performance of feather pecking behaviour involves low 5-HT neurotransmission. In the present study, we postulated that if low 5-HT is causally underlying feather pecking, increasing 5-HT turnover in the forebrain will decrease the development and performance of feather pecking. Augmentation of 5-HT neurotransmission in the brain was induced by chronically increasing dietary levels of the essential amino acid l-tryptophan (TRP) from which 5-HT is synthesised. From the age of 34 days, LFP and HFP chicks were fed a diet containing 2% TRP, whereas control birds of both lines were continuously fed with the normal rearing feed (0.16% TRP). From 35 days of age, litter was removed from the pens (10 pens/line-treatment) and all chicks (10 chicks/pen) were housed on a slatted floor until the end of the experiment. At 49 days of age, feather pecking behaviour was studied for 30 min. At 50 days of age baseline corticosterone, TRP and other large amino acids (LNAAs) were measured in the blood plasma of decapitated chicks (10 chicks per line-treatment). Furthermore, plasma corticosterone and central 5-HT turnover levels in response to manual restraint (5 min) were determined (10 chicks/line-treatment). For neither gentle nor severe feather pecking a significant line × treatment interaction was found. However, TRP treatment resulted in a significant [ P = 0.02] overall decrease of the frequency of gentle feather pecking. For severe feather pecking a similar but not significant pattern was found. Significant line effects were found for gentle and severe feather pecking. HFP birds showed significantly higher levels of gentle and severe feather pecking behaviour than LFP birds [ P < 0.001]. TRP treatment significantly increased the TRP/LNAA ratio in the plasma of the chicks. Furthermore, TRP treatment overall increased baseline and stress-induced levels of plasma corticosterone (although more pronounced in the LFP line). TRP supplementation significantly increased 5-HT turnover in the hippocampus and archistriatum and tended to do so in the remainder of the forebrain. The results confirm our hypothesis that feather pecking behaviour is triggered by low serotonergic neurotransmission, as increasing serotonergic tone, by increasing dietary TRP, decreases gentle feather pecking behaviour.

Effects of cold stress on immune responses and body weight of chicken lines divergently selected for antibody responses to sheep red blood cells

Effects of cold stress (CS) on the immune system of chicken lines divergently selected for high (H line) and low (L line) antibody responses to SRBC next to a randombred control (C) line were studied. Three- to four-week-old growing chicks of the three lines were feed-restricted at 80% ad libitum and subjected to CS at 10 degrees C continuously for 7, 5, 3, 1, or 0 d prior to immunization with keyhole limpet hemocyanin (KLH). Specific and natural antibodies were measured in the three chicken lines subjected to or not subjected to various durations of CS prior to immunization. In addition to antibodies we also measured in vitro lymphocyte proliferation as a measure of cell-mediated immunity (CMI), zymosan-induced reactive oxygen intermediates (ROI) production as a measure of phagocytosis, and BW gain as a measure of production trait. In general, significantly higher antibody responses to KLH and natural antigens were found in the H line as compared to the other two lines. Specific antibody responses to KLH were not significantly affected by CS, but an acute transient increase in natural antibody titers to ovalbumin was found in H line birds subjected to 1 d of CS, which was not found in C or L line birds. On the other hand, an acute significant increase in natural antibody titers to lipopolysaccharide (LPS) was found in C and L line birds subjected to 1 d CS but not in H line birds. Cold stress enhanced the ROI production. In addition, 7 d of CS significantly enhanced cellular immunity in vitro, but no significant line effects with respect to cellular immunity were found. BW gain was negatively affected by CS, especially when CS was applied for longer periods. We concluded that birds responded immediately to CS with enhanced innate (phagocyte and natural antibody) immunity, irrespective of genetic background. When CS is prolonged, the cellular adaptive immune response is affected also. Although reallocation of energy was not measured, our data suggested that under limited conditions (e.g., restricted feeding) with simultaneous stress (e.g., CS), growth and cellular immunity were more sensitive than thermoregulation and humoral immunity. With respect to vital life traits, thermoregulation may have first priority followed by adaptive cellular immunity, humoral immunity, and BW gain. The relationships between immune responses and adaptation to stress are discussed.

Evaluation of serum insulin-like growth factor binding proteins (IGFBP) in Angus cattle divergently selected for serum IGF-I concentration

Postweaning serum insulin-like growth factor-I (IGF-I) concentrations and serum IGF binding proteins (IGFBP) were investigated in 68 (1992 Fall-born) and 84 (1999 Fall-born) Angus cattle selected for either high or low serum IGF-I concentrations since 1989. Relative serum levels of IGFBP were determined by [ 125 I ]IGF-I Western ligand blotting. IGFBP species of 38–42, 34, 30, and 24 kDa were identified. The 34 kDa species was identified as IGFBP-2 by immunoblot analysis. No significant line effects were observed for any of the IGFBP. In both 1992 and 1999, heifers had higher IGFBP-2 levels than bulls ( P<0.0005). In 1992 calves, relative levels of the 38–42 and 24 kDa species were significantly correlated with serum IGF-I concentration. In 1999 calves, none of the IGFBP were correlated with serum IGF-I, although IGFBP-2 was negatively correlated with several measures of body weight. No significant line effects were observed for growth or serum IGF-I traits in 1992 calves. However, 1999 high line calves had higher serum IGF-I concentrations and body weights than low line calves ( P<0.05). In both 1992 and 1999 calves, bulls had higher serum IGF-I concentrations and body weights than heifers ( P<0.05). Thus, while selection for high versus low serum IGF-I concentrations has resulted in divergence between the selection lines and also in changes in body weights, it has not resulted in changes in serum IGFBP levels. Furthermore, circulating IGFBP-2 appears to be higher in heifers than in bulls, and also appears to be negatively correlated with body weights.

Effects of improved, adapted white clover (Trifolium repens L.) germplasm on the productive properties of a hill pasture

White clover (Trifolium repens L.) herbage accumulation rate, nitrogen (N) fixation rate and efficiency, and plant growth characteristics were compared in pastures based on eight white clover lines on north‐ and south‐facing sites under sheep grazing in southern North Island hill country during years 4–7 following oversowing. The lines compared included three cultivars ('Grasslands Tahora’, ‘Grasslands Prestige’, and Prop) bred for hill country and/or sheep grazing systems with (notionally, at least) a moderate‐high degree of adaptation to the environment, and two cultivars ('Grasslands Huia’ and ‘Grasslands Kopu') known to have moderate—low adaptation. The control treatment comprised pastures based on the resident clover ecotype of the site, seed of which was sown at the same rate as the other lines. Two of the adapted lines (Tahora, Prestige) yielded significantly more white clover herbage than the resident ecotype over 3 full years of measurement. Prestige displayed consistently greater cool‐season growth in late winter‐early spring than all other lines. All three adapted cultivars fixed significantly more N than the resident ecotype over 12 months (mean for resident = estimated 64 kg N/ha per year compared to mean for three cultivars = 100 kg N/ha per year). There was a close linear relationship between white clover herbage accumulation rate and clover stolon density in most years and on both aspects. The adapted lines developed greater stolon densities through superior branching ability (higher frequency of occurrence of branches at stolon nodes). There was evidence that the adapted clover lines were able to compete more effectively with grasses for growth resources at some times of the year, e.g., for mineralised N in late winter‐early spring, resulting in lower N fixation efficiencies for Tahora and Prestige (mean 43 kg N fixed/t clover DM grown, versus 122 kg N/t clover DM for the resident ecotype). There were no statistically significant effects of clover line on total annual pasture herbage accumulation, but a difference between Prestige and all other lines in total pasture growth in winter gradually strengthened over 4 years of measurement so that, in the final year measured (year 7 after sowing), a statistically significant effect of line was recorded. In this winter, Prestige‐based pastures grew 1130 kg DM/ ha over 65 days from early June to late August, whereas resident pastures grew 570 kg DM/ha. The results are discussed within the context of pasture improvement strategies in hill country. Several important effects of adapted germplasm on the productive properties of hill pastures are identified.

Analysis of a diallel cross to estimate effects of crossing on resistance to enteric septicemia in channel catfish, Ictalurus punctatus

The trend in commercial channel catfish, Ictalurus punctatus, production is toward increased stocking densities and feeding rates, and is often accompanied by disease problems. Enteric septicemia, caused by the bacterium, Edwardsiella ictaluri, is responsible for many disease losses in channel catfish cultured in the southern United States. A complete diallel cross among three strains, Red River, Norris, and M X K (Marion X Kansas), was used to estimate effects of crossing on resistance to E. ictaluri. Juveniles (mean weight 15.2 ± 3.8 grams) from all nine crosses were challenged by immersion, and survival determined 28 days following bacterial exposure. Mean survival of all crosses was 62.2% and ranged from 35.8% in the M X K female X Norris male cross to 90.0% in the Norris female X M X K male cross. Estimates for heterosis, line, maternal, reciprocal effects, and general combining ability corrected for maternal effects were obtained from contrasts among appropriate mean squares. Average, line or specific heterosis effects were not significant suggesting that crossbreeding these strains would not increase disease resistance due to heterosis. Significant line effects in Norris and M X K strains demonstrated differences for disease resistance in these strains. Significant maternal effects conveyed increased disease resistance to offspring in the Norris strain. Significant general combining ability indicated additive genetic differences for enteric septicemia resistance in Norris and M X K strains.

Genotype-specific habitat selection for oviposition sites in the cactophilic species Drosophila buzzatii

Isofemale lines of the cactophilic species, Drosophila buzzatii, exhibit genetic variation for their oviposition response to cactus yeast species in the laboratory. In general, interactions between yeast species preclude the use of pairwise preferences as predictors of preferences in three-way choice experiments. Two isofemale lines with relatively high laboratory preference for ovipositing on the yeast Pichia cactophila (as opposed to Cryptococcus cereanus) and two isofemale lines with relatively low preference for P. cactophila were used in a series of field release experiments to determine if laboratory preferences were also realized under field conditions. The influence of yeast species on both settling behaviour (long-distance response) and oviposition preference (short-distance response) were tested. The four lines were identical in their settling behaviour, preferring P. cactophila. The analysis of the oviposition preference tests showed significant line effects which correlated with the laboratory results. Thus a genetic component for oviposition preference under laboratory and field conditions was demonstrated and this strengthens the evidence for genotype-specific habitat selection in D. buzzatii. One low line, however, did not differ significantly from the two high lines under field conditions. A laboratory retest of this low line showed that the laboratory preference had not changed. The reason for the difference in the two situations is unknown but undoubtedly is attributable to uncontrolled variables under the field situation. Settling behaviour and oviposition response, in general, appear to be proximately linked to differences in the volatiles produced by the different yeast species.

Reproductive development in the hermaphroditic freshwater snail Physa monitored with complementing albino lines

We estimated age and size at onset of functional outcross- and self-fertility in three isofemale lines of Physa heterostropha carrying the recessive, non-allelic genes, alb1 and alb2 . 9Experimental’ snails of these lines were reared from 2 weeks of age to adulthood and periodically introduced to mature, complementing 9challenge’ snails. The three lines differed significantly in the size at which they matured, but not the age, under our culture conditions. Male reproductive maturity was reached at a mean of 5.7 weeks and female reproductive maturity at 7.3 weeks ( n = 50). These ages correspond to mean shell lengths of 5.3—6.2 mm as male and 6.9—7.6 mm as female. Over all three lines, first production of viable offspring by self-fertilization occurred at a mean age of 22 weeks ( n = 113). Again a significant line effect on size at reproduction was detected, with mean size at onset of self-fertilization ranging from 8.1 mm to 8.7 mm. Autosterility in the three lines ranged from negligible to 44 %. Among autofertile snails, we identified cases of outcross male-sterility, outcross female-sterility, and outcross double-sterility. Of 46 individuals demonstrating male function before female, two passed through brief periods of self-fertilization before outcrossing as females. We also identified three individuals maturing simultaneously in both capacities and one individual that matured as female before male. So, although the situation is complex, we suggest that ‘simultaneous hermaphroditism’ provides the best description of the reproductive biology of Physa . The great diversity of reproductive allocation described here implies considerable potential for life-history evolution in these snails.

Relationships between whole-body chemical composition, physically dissected carcass parts and backfat measurements in pigs

ABSTRACTLog-linear relationships between various measurements of the chemical and physical body composition of the pig were obtained in four datasets representing a range of sexes, genotypes and feeding treatments. One of these datasets (dataset 1) comprised genetic control and selection line Large White pigs. There were significant differences between datasets for most of the relationships investigated. The causes of the differences cannot be determined. Within datasets, relationships between various body components and the weight of crude protein in the whole body were unaffected by genotype or sex. The relationships of both intermuscular fat and trimmed carcass lipid with whole body lipid differed significantly between the control and selection lines in dataset 1. Fat thickness measurements taken over the m. longissimus at the last rib were less at the same body lipid in the selection line than the control line suggesting a redistribution of fat away from this area as a result of selection. Relationships between viscera, lungs and empty body weight were significantly affected by line while those between trimmed carcass, liver, kidneys and empty body weight were significantly affected by sex. Selection line pigs had less perinephric and retroperitoneal fat than controls at the same whole body fat weight and less subcutaneous fat at the same cold carcass weight. There were no significant line effects on lean or bone weight distribution. Selection line pigs had significantly less subcutaneous fat in the collar joint and more intermuscular fat in the ham. There were few significant sex effects on tissue weight distribution.

GENETIC EFFECTS AND RELATIONSHIPS AMONG CARCASS FAT CONTENT OF BROILER CHICKENS AND PLASMA TRIGLYCERIDE LEVELS AND LIVER TRAITS

The phenotypic and genetic relationships among carcass traits were studied in four pure lines of 44-day-old female broiler chickens. Two diets with the same energy to protein ratio but different nutrient densities were used. Liver weight was the only trait significantly affected by diet, whereas no significant differences among lines were noted for blood plasma triglyceride levels, abdominal fat, percent carcass fat and moisture, and percent liver fat and moisture. A significant effect of line was observed for liveweight, carcass weight, fat-free carcass weight, and liver weight, with birds from the two sire lines being larger than those from the two dam lines. A pedigreed population of one of the pure lines gave moderate to low heritability estimates for the three liver traits. The phenotypic correlations of blood triglyceride levels with the other traits studied were very low. Phenotypic and genetic correlations showed that there might be some potential for using percent liver fat and moisture in predicting carcass fat. However, when prediction equations were developed on a within-line basis, percent liver moisture contributed significantly to the total variance of carcass fat in only one of the lines, and the contributions of other liver traits were not significant. Carcass moisture percent, carcass weight, and abdominal fat weight were of more value in predicting carcass fat than were the liver and blood traits measured. Key words: Broiler chickens, carcass fat, blood triglyceride, liver