Exploring multiple stressor effects with Ecopath, Ecosim, and Ecospace: Research designs, modeling techniques, and future directions.

Understanding the cumulative effects of multiple stressors is a research priority in environmental science. Ecological models are a key component of tackling this challenge because they can simulate interactions between the components of an ecosystem. Here, we ask, how has the popular modeling platform Ecopath with Ecosim (EwE) been used to model human impacts related to climate change, land and sea use, pollution, and invasive species? We conducted a literature review encompassing 166 studies covering stressors other than fishing mostly in aquatic ecosystems. The most modeled stressors were physical climate change (60 studies), species introductions (22), habitat loss (21), and eutrophication (20), using a range of modeling techniques. Despite this comprehensive coverage, we identified four gaps that must be filled to harness the potential of EwE for studying multiple stressor effects. First, only 12% of studies investigated three or more stressors, with most studies focusing on single stressors. Furthermore, many studies modeled only one of many pathways through which each stressor is known to affect ecosystems. Second, various methods have been applied to define environmental response functions representing the effects of single stressors on species groups. These functions can have a large effect on the simulated ecological changes, but best practices for deriving them are yet to emerge. Third, human dimensions of environmental change - except for fisheries - were rarely considered. Fourth, only 3% of studies used statistical research designs that allow attribution of simulated ecosystem changes to stressors' direct effects and interactions, such as factorial (computational) experiments. None made full use of the statistical possibilities that arise when simulations can be repeated many times with controlled changes to the inputs. We argue that all four gaps are feasibly filled by integrating ecological modeling with advances in other subfields of environmental science and in computational statistics.

Riparian Forest Cover Modulates Phosphorus Storage and Nitrogen Cycling in Agricultural Stream Sediments.

Watershed land cover affects in-stream water quality and sediment nutrient dynamics. The presence of natural land cover in the riparian zone can reduce the negative effects of agricultural land use on water quality; however, literature evaluating the effects of natural riparian land cover on stream sediment nutrient dynamics is scarce. The objective of this study was to assess if stream sediment phosphorus retention and nitrogen removal varies with riparian forest cover in agricultural watersheds. Stream sediment nutrient dynamics from 28 sites with mixed land cover were sampled three times during the growing season. Phosphorus dynamics and nitrification rates did not change considerably throughout the study period. Sediment total phosphorus concentrations and nitrification rates decreased as riparian forest cover increased likely due to a decline in fine, organic material. Denitrification rates were strongly correlated to surface water nitrate concentrations. Denitrification rate and denitrification enzyme activity decreased with an increase in forest cover during the first sampling period only. The first sampling period coincided with the greatest connectivity between the watershed and in-stream processing, indicating that riparian forest cover indirectly decreased denitrification rates by reducing the concentrations of dissolved nutrients entering the stream. This reduction in load may allow the sediment to maintain greater nitrogen removal efficiency, because bacteria are not saturated with nitrogen. Riparian forest cover also appeared to lessen the effect of agriculture in the watershed by decreasing the amount of fine material in the stream, resulting in reduced phosphorus storage in the stream sediment.

Is reduced freshwater flow in Tigris-Euphrates rivers driving fish recruitment changes in the Northwestern Arabian Gulf?

Like fishing, natural regime shifts and human-induced environmental changes are often equally important factors in driving fish stock declines. In the Northwestern Arabian Gulf, many fish stocks are declining, raising questions about the reduction in the flow of Tigris-Euphrates rivers. Here we investigate the relationship between Tigris-Euphrates river flow and the estimated recruitment patterns from assessment models. We found a positive correlation between the estimated finfish recruitment trends and the flow of Tigris-Euphrates rivers. Additionally, the assessment model showed remarkably weak compensation ratio, likely indicating a reduction in the productivity of nursery area of two finfish stocks but not in that of the crustacean stock. Our investigation would be very critical in providing guidelines to the government agencies in the Northwestern Arabian Gulf as well as countries of Tigris-Euphrates basins: to consider the impacts associated with reductions in Tigris-Euphrates river flows on the ecosystem services of the region.

Effects of trimethoprim-sulfadiazine and detomidine on the function of equine Kv 11.1 channels in a two-electrode voltage-clamp (TEVC) oocyte model.

The long QT syndrome (LQTS) is a channelopathy that can lead to severe arrhythmia and sudden cardiac death. Pharmacologically induced LQTS is caused by interaction between drugs and potassium channels, especially the Kv 11.1 channel. Due to such interactions, numerous drugs have been withdrawn from the market or are administered with precautions in human medicine. However, some compounds, such as trimethoprim-sulfonamide combinations are still widely used in veterinarian medicine. Therefore, we investigate the effect of trimethoprim-sulfadiazine (TMS), trimethoprim, sulfadiazine, and detomidine on equine-specific Kv 11.1 channels. Kv 11.1 channels cloned from equine hearts were heterologously expressed in Xenopus laevis oocytes, and whole cell currents were measured by two-electrode voltage-clamp before and after drug application. TMS blocked equine Kv 11.1 current with an IC50 of 3.74 mm (95% CI: 2.95-4.73 mm) and affected the kinetics of activation and inactivation. Similar was found for trimethoprim but not for sulfadiazine, suggesting the effect is due to trimethoprim. Detomidine did not affect equine Kv 11.1 current. Thus, equine Kv 11.1 channels are also susceptible to pharmacological block, indicating that some drugs may have the potential to affect repolarization in horse. However, in vivo studies are needed to assess the potential risk of these drugs to induce equine LQTS.

Shorter preschool, leukocyte telomere length is associated with obesity at age 9 in Latino children.

The aim of this study was to determine the potential role of leukocyte telomere length as a biomarker for development of childhood obesity in a low-income Latino population. A birth cohort of Latino children (N = 201) in San Francisco (recruited May 2006-May 2007) was followed until age 9 and assessed annually for obesity and dietary intake. Leukocyte telomere length was measured at 4 and 5 years (n = 102) and assessed as a predictor for obesity at age 9, adjusting for known risk factors. Furthermore, leukocyte telomere length at age 4 and 5 was evaluated as a possible mediator of the relationship between excessive sugar-sweetened beverage consumption and obesity at age 9. Shorter leukocyte telomere length in preschoolers was associated with obesity at age 9 (adjusted odds ratio 0.35, 95% confidence interval 0.13-0.94) after adjustment for known risk factors. Telomere length mediated 11% of the relationship between excessive sugar-sweetened beverage consumption and obesity. Shorter leukocyte telomere length may be an indicator of future obesity risk in high-risk populations as it is particularly sensitive to damage from oxidative stress exposure, including those from sugar-sweetened beverages.

Zona pellucida protein B2 messenger ribonucleic acid expression varies with follicular development and granulosa cell location.

The freshly ovulated ovum in avian species is surrounded by a protein layer called the inner perivitelline layer (IPVL). The IPVL contains zona pellucida proteins and 6 distinct zona pellucida genes have been identified (ZPA, ZPB1, ZPB2, ZPC, ZPD and ZPX1) in the chicken. In the present research, the expression of the mRNA for ZPA, ZPB2, and ZPX1 was investigated in 2 lines of turkey hens selected for either increased egg production (E line) or increased body weight (F line). Theca and granulosa cell expression of the mRNA for ZPA and ZPB2 was also investigated in hierarchical and prehierarchical follicles from broiler breeder hens. Granulosa tissue was collected from F1 through F4 and F1 through F10 follicles in E line and F line hens, respectively. A one cm2 section of the granulosa layer around the germinal disc (GD) and an equivalent sized nongerminal disc (NGD) area was also collected from the F1 and F2 follicles from other hens from each genetic line. Granulosa and theca tissue was collected from hierarchical and prehierarchical follicles of broiler breeder hens. Total RNA was extracted from the samples. Minor groove-binding probes and primers for detecting ZPA, ZPB2, and ZPX1, were made for real-time PCR analyses. Expression of ZPA, ZPB2, and ZPX1 was detected in all follicle sizes from both genetic lines of hens. No significant differences in ZPA and ZPX1 mRNA expression were detected between the GD and NGD granulosa cells. However, the expression of the mRNA for ZPB2 was significantly greater in the GD granulosa cells when compared to the NGD granulosa cells in F1 and F2 follicles from E line and F line hens. In broiler breeder hens, the mRNA expression of ZPA and ZPB2 was greatest in the smallest prehierarchical follicles. The results suggest that higher expression of ZPB2 in the germinal disc area may be important for the preferential binding of sperm to this region of the IPVL.

Correlates of whole-blood polyunsaturated fatty acids among young children with moderate acute malnutrition.

BACKGROUND: Severe acute malnutrition (SAM) has been associated with low polyunsaturated fatty acid (PUFA) status. However, investigations regarding PUFA status and correlates in children with moderate acute malnutrition (MAM) from low-income countries are scarce. The aim of this study was to describe whole-blood PUFA levels in children with moderate acute malnutrition (MAM) and to identify correlates of PUFAs. METHODS: We conducted a cross-sectional study using baseline data from a prospective nutritional intervention trial among 1609 children with MAM aged 6-23 months in Burkina Faso,West Africa. Whole-blood PUFAs were measured by gas chromatography and expressed as percent of total whole-blood fatty acids (FA%). Potential correlates of PUFAs including infection, inflammation, hemoglobin, anthropometry (difference between children diagnosed as having MAM based on low mid-upper-arm-circumference (MUAC) only, low MUAC and weight-for-height z-score (WHZ), or low WHZ only) and diet were assessed by linear regression adjusted for age and sex. RESULTS: Children with MAM had low concentrations of whole-blood PUFAs, particularly n-3 PUFAs. Moreover, children diagnosed with MAM based only on low MUAC had 0.32 (95% confidence interval (CI), 0.14; 0.50) and 0.40 (95% CI, 0.16; 0.63) FA% lower arachidonic acid (AA) than those recruited based on both low WHZ as well as low MUAC and those recruited with low WHZ only, respectively. Infection and inflammation were associated with low levels of all long-chain (LC)-PUFAs, while hemoglobin was positively associated with whole-blood LC-PUFAs. CONCLUSION: While PUFA deficiency was not a general problem, overall whole-blood PUFA concentrations, especially of n-3 PUFAs, were low. Infection, inflammation, hemoglobin, anthropometry and diet were correlates of PUFAs concentrations in children with MAM. TRIAL REGISTRATION: The trial is registered at http://www.isrctn.com ( ISRCTN42569496 ).

My sibling, my weight. How gender, sibling gender, sibling weight and sibling weight level perception influence weight perception accuracy.

OBJECTIVE: The objective of this study was to examine the impact of sibling weight level perception and sibling weight on the accuracy of respondent weight level perception dependent on sibling-pair gender composition. DESIGN: A cross-sectional study based on the survey data, which include the children of a nationally representative sample of Danes. Logit regression models were used. SUBJECTS: Two thousand nine hundred and sixty-eight respondents comprising 397 female sibling pairs, 357 male sibling pairs and 730 opposite-sex sibling pairs. The inclusion of both same-sex siblings and opposite-sex siblings is novel for studies on weight perceptions. MEASUREMENTS: Weight underestimation and weight overestimation were calculated on the basis of difference between actual weight level and self-perceived weight level. Respondent gender, sibling gender, sibling body mass index (BMI) and the siblings' self-perceived weight level were included as the main controls. RESULTS: Women frequently overestimate their weight level, whereas men often underestimate theirs. Women are more likely to overestimate their weight if their sister does the same but less likely if their brother overestimates his weight. Likewise, women are more likely to underestimate their weight if their sister also underestimates her weight but less likely if their brother underestimates his weight. The higher the BMI of their brother and the lower the BMI of their sister, the more likely men are to underestimate their own weight level. CONCLUSION: RESULTS underline the importance of social context when looking at body formation and weight perceptions. The weight and weight perceptions of siblings influence own weight perception. Gender is central to studies on weight-related issues, not only respondent gender - equally so the gender of interaction.

Programming of glucose-insulin homoeostasis: long-term consequences of pre-natal versus early post-natal nutrition insults. Evidence from a sheep model.

AIM: Exposure to adverse intra-uterine conditions can predispose for metabolic disorders later in life. By using a sheep model, we studied (i) how programming of glucose-insulin homoeostasis during late gestation is manifested later in life depending on the early post-natal dietary exposure and (ii) whether dietary alteration in obese individuals can prevent adverse outcomes of early life programming. METHODS: During late gestation, twin-pregnant sheep were fed 100% (NORM) or 50% (LOW) of energy and protein requirements. After birth, offspring were exposed to a moderate (CONV) or high-carbohydrate-high-fat (HCHF) diet until around puberty. Offspring remaining thereafter (exclusively females) were fed a moderate diet until young adulthood. RESULTS: LOW lambs had increased insulin secretory responses during intravenous glucose tolerance tests indicative of reduced insulin sensitivity. HCHF lambs were hypertriglyceridaemic, 75% had mild pancreatic collagen infiltration, and their acute insulin secretory response and insulin clearance during intravenous glucose and insulin tolerance tests, respectively, were reduced. However, NORM-HCHF in contrast to LOW-HCHF lambs had normal glucose tolerance, indicating that later health outcomes are highly influenced by pre-natal nutrition. Dietary alteration normalized glucose-insulin homoeostasis in adult HCHF females, whereas late-gestation undernutrition (LOW) permanently depressed insulin sensitivity. CONCLUSION: Maintenance of glucose tolerance in sheep exposed to pre-natal undernutrition relied on pancreatic hypersecretion of insulin to compensate for reduced insulin sensitivity. A mismatching high-fat diet in early post-natal life interfered with this pancreatic hypersecretion resulting in reduced glucose tolerance. Early post-natal, but not late pre-natal, impacts on glucose-insulin homoeostasis could be reversed by dietary correction later in life.

Stream Sediment Sources in Midwest Agricultural Basins with Land Retirement along Channel.

Documenting the effects of agricultural land retirement on stream-sediment sources is critical to identifying management practices that improve water quality and aquatic habitat. Particularly difficult to quantify are the effects from conservation easements that commonly are discontinuous along channelized streams and ditches throughout the agricultural midwestern United States. Our hypotheses were that sediment from cropland, retired land, stream banks, and roads would be discernible using isotopic and elemental concentrations and that source contributions would vary with land retirement distribution along tributaries of West Fork Beaver Creek in Minnesota. Channel-bed and suspended sediment were sampled at nine locations and compared with local source samples by using linear discriminant analysis and a four-source mixing model that evaluated seven tracers: In, P, total C, Be, Tl, Th, and Ti. The proportion of sediment sources differed significantly between suspended and channel-bed sediment. Retired land contributed to channel-bed sediment but was not discernible as a source of suspended sediment, suggesting that retired-land material was not mobilized during high-flow conditions. Stream banks were a large contributor to suspended sediment; however, the percentage of stream-bank sediment in the channel bed was lower in basins with more continuous retired land along the riparian corridor. Cropland sediments had the highest P concentrations; basins with the highest cropland-sediment contributions also had the highest P concentrations. Along stream reaches with retired land, there was a lower proportion of cropland material in suspended sediment relative to sites that had almost no land retirement, indicating less movement of nutrients and sediment from cropland to the channel as a result of land retirement.

Late gestation undernutrition can predispose for visceral adiposity by altering fat distribution patterns and increasing the preference for a high-fat diet in early postnatal life.

We have developed a sheep model to facilitate studies of the fetal programming effects of mismatched perinatal and postnatal nutrition. During the last trimester of gestation, twenty-one twin-bearing ewes were fed a normal diet fulfilling norms for energy and protein (NORM) or 50% of a normal diet (LOW). From day 3 postpartum to 6 months (around puberty) of age, one twin lamb was fed a conventional (CONV) diet and the other a high-carbohydrate-high-fat (HCHF) diet, resulting in four groups of offspring: NORM-CONV; NORMHCHF; LOW-CONV; LOW-HCHF. At 6 months of age, half of the lambs (all males and three females) were slaughtered for further examination and the other half (females only) were transferred to a moderate sheep diet until slaughtered at 24 months of age (adulthood). Maternal undernutrition during late gestation reduced the birth weight of LOW offspring (P<0·05), and its long-term effects were increased adrenal size in male lambs and adult females (P<0·05), increased neonatal appetite for fat-(P=0·004) rather than carbohydrate-rich feeds (P<0·001) and reduced deposition of subcutaneous fat in both sexes (P<0·05). Furthermore, LOW-HCHF female lambs had markedly higher visceral:subcutaneous fat ratios compared with the other groups (P<0·001). Postnatal overfeeding (HCHF) resulted in obesity (.30% fat in soft tissue) and widespread ectopic lipid deposition. In conclusion, our sheep model revealed strong pre- and postnatal impacts on growth, food preferences and fat deposition patterns. The present findings support a role for subcutaneous adipose tissue in the development of visceral adiposity, which in humans is known to precede the development of the metabolic syndrome in human adults.

Contribution of fish to the marine inorganic carbon cycle.

Oceanic production of calcium carbonate is conventionally attributed to marine plankton (coccolithophores and foraminifera). Here we report that marine fish produce precipitated carbonates within their intestines and excrete these at high rates. When combined with estimates of global fish biomass, this suggests that marine fish contribute 3 to 15% of total oceanic carbonate production. Fish carbonates have a higher magnesium content and solubility than traditional sources, yielding faster dissolution with depth. This may explain up to a quarter of the increase in titratable alkalinity within 1000 meters of the ocean surface, a controversial phenomenon that has puzzled oceanographers for decades. We also predict that fish carbonate production may rise in response to future environmental changes in carbon dioxide, and thus become an increasingly important component of the inorganic carbon cycle.

The mRNA for zona pellucida proteins B1, C and D in two genetic lines of turkey hens that differ in fertility.

The avian inner perivitelline layer (IPVL) contains zona pellucida protein-B1 (ZPB1), zona pellucida protein-C (ZPC) and zona pellucida protein-D (ZPD). These three proteins may be involved in sperm binding to the IPVL. ZPB1 is produced by the liver and transported to the developing preovulatory follicle, while ZPC and ZPD are synthesized and secreted by the granulosa cells of the preovulatory follicle. The mRNA of ZPB1, ZPC, and ZPD was investigated in two lines of turkey hens selected for over 40 generations for either increased egg production (E line) or increased body weight (F line). Total RNA was extracted from the liver and from 1cm(2) sections of the granulosa layer around the germinal disc and a nongerminal disc area of the F(1) and F(2) follicles of hens from each genetic line. Northern analysis was performed using chicken cDNA probes for all three ZP proteins. Hepatic mRNA for ZPB1 was greater (P<0.05) in turkey hens from the E line than the F line. Although, there was no difference in ZPC mRNA between the germinal disc and nongerminal disc region of the two largest follicles in E line hens, ZPC mRNA was greater in the nongerminal disc region compared to the germinal disc region in the two largest follicles obtained from the F line hens. There were no differences in ZPD mRNA between the germinal disc and nongerminal disc regions of the F(1) and F(2) follicles for either genetic line. The results suggest that the greater rates of fertility previously observed in eggs from the E line hens compared with the F line of hens may be related to differential amounts of the potential sperm binding proteins ZPB1 and ZPC.

Methods for estimating detection efficiency and tracking acoustic tags with mobile transect surveys.

Mobile transect surveys were conducted for 5 years in a deep fjord looking for weak acoustic tags, most of which were in dead fishes lying on the seabed. Detection efficiencies were quantified because inferences about fish presence were made from tag detection data but a considerable proportion of tags were not detected. Methods for assessing transect widths using cumulative probabilities of measured perpendicular distances from blind transect lines to triangulated tag locations are described. Three methods for estimating detection efficiencies are presented: fitting attenuation functions to perpendicular distance data, simultaneous use of two receiver systems and test tag surveys. Several factors that influenced these detection efficiencies and ranges are shown, including boat speed, depth of tag, tag type, different hydrophone-receiver systems and variation among individual hydrophones and receivers of the same model. The trade-off between detection efficiency per unit area and area swept is discussed, which is largely based on boat speed during transects. Finally, several methods are suggested for increasing decoding efficiencies in mobile tracking studies when tags are heard but are difficult to decode.

Broiler embryo bone development is influenced by incubator temperature, oxygen concentration and eggshell conductance at the plateau stage in oxygen consumption.

1. Four experiments were conducted to evaluate the effects of temperature (TEM) and oxygen (O(2)) concentrations during the last 4 d of incubation on bone development. Fertile eggs from two strains were obtained that either exhibited Low or High eggshell conductance (G). 2. Four experimental cabinets provided either four TEM (36, 37, 38 or 39 degrees C) or four O(2) concentrations (17, 19, 21 or 23% O(2)). Data were analysed as a 2 x 2 factorial design. In the fourth experiment, two temperatures (36 and 39 degrees C), two O(2) concentrations (17 and 23%) and the same Low and High G strains were evaluated in a 2 x 2 x 2 factorial design. 3. Body weights (BW) and residual yolks were obtained, both legs were dissected. Femur, tibia and shank weights, length and thickness were recorded. Relative asymmetry (RA) of each leg section was calculated. 4. The results indicated that elevated TEM during incubation increased RA between the two legs, mainly in the Low G strain. Chickens at the lowest O(2) concentrations had lighter and shorter tibias, lighter shanks, and increased RA of femur length compared to chickens in the 23% O(2). In the fourth experiment no interactions were observed between O(2) and TEM. High TEM depressed BW of Low G broilers, but no significant effect of treatments was observed on BW of High G broilers. Nevertheless, the high TEM or low O(2) independently caused reduced femur and tibia weights and length, shank length and thickness, and both low O(2) and high TEM together increased RA in shank weight. 5. These results suggest that late incubation conditions affect long bone development in broilers.

Effects of incubator temperature and oxygen concentration during the plateau stage of oxygen consumption on Turkey embryo long bone development.

Temperature (TEM) and O(2) concentrations during the plateau stage of oxygen consumption are known to affect yolk utilization, tissue development, and thyroid metabolism in turkey embryos. Three experiments were conducted to evaluate these incubation effects on long bone development. Fertile eggs of Nicholas turkeys were used. In each trial, standard incubation conditions were used to 24 d, when the eggs containing viable embryos were randomly divided into 4 groups. Four experimental cabinets provided 4 TEM (36, 37, 38, or 39 degrees C) or 4 O(2) concentrations (17, 19, 21, or 23% O(2)). In the third experiment, 2 temperatures (36 and 39 degrees C) and 2 O(2) concentrations (17 and 23%) were evaluated in a 2 x 2 factorial design. Body and residual yolk weights were obtained. Both legs were dissected, and shanks, femur, and tibia weights, length, and thickness were recorded. Relative asymmetry of each leg section was calculated. Chondrocyte density was evaluated in slides stained with hematoxylin and eosin. Immunofluorescence was used to evaluate the presence of collagen type X and transforming growth factor beta. Hot TEM caused reduction of tibia weights and increase of shank weight when compared with cool TEM. The lengths of femur, tibia, and shanks were reduced by 39 degrees C. The relative asymmetry of leg weights were increased at 38 and 39 degrees C. Poult body and part weights were not affected by O(2) concentrations, but poults on 23% O(2) had bigger shanks and heavier tibias than the ones on 17% O(2). High TEM depressed the fluorescence of collagen type X and transforming growth factor beta. The O(2) concentrations did not consistently affect the immunofluorescence of these proteins. The chondrocyte density was affected by TEM and O(2) in resting and hypertrophic zones. In the third experiment, high TEM depressed BW, leg muscle weights, and shank length. Low O(2) reduced tibia and shanks as a proportion of the whole body. We concluded that incubation conditions affect long bone development in turkeys.

Genetic control of embryonic cardiac growth and functional maturation in turkeys.

Turkey experimental lines E (selected 44 yr for increased total egg production) and F (selected 38 yr for increased 16-wk BW) were mated reciprocally with the randombred control lines from which they were derived (RBC1 and RBC2, respectively), and the pureline and reciprocal cross poults were compared for their BW, heart weight, heart rates, myocardial glycogen and lactate concentrations, and plasma creatine kinase (CK) and lactate dehydrogenase (LDH) activities. The CK and LDH were used as indicators of cardiac insufficiency. Orthogonal contrasts of the data from the pureline and reciprocal cross data were used to estimate additive genetic effects, reciprocal effects (confounded maternal and sex-linked effects), and heterosis for each of the traits measured. Long-term selection for increased egg production in the E line has reduced embryo heart weight and has altered the energy metabolism of the myocardium. The differences in energy metabolism may be due to the more rapid heart rates. Conversely, long-term selection for increased 16-wk BW has significantly decreased the heart rate of F line embryos and has not changed the weight of the heart relative to the BW until the embryo has passed through the plateau stage. The F line embryos show a different energy metabolism that relies much more on gluconeogenesis. Embryo deaths occur more frequently in turkey embryos when the energy metabolism of the myocardium shows elevated glycogen to lactate ratios as it did in the pure E and F lines.

The effect of broiler breeder genetic strain and parent flock age on eggshell conductance and embryonic metabolism.

The effect of genetic strain (Ross 308; Cobb 500) and parent flock age [young (29 wk), peak (Ross = 34 wk; Cobb = 36 wk), postpeak (40 wk), mature (45 wk), old (55 wk), and very old (59 wk)] on eggshell conductance and embryonic metabolism were examined. At each flock age, eggs from each strain were incubated for 21.5 d in individual metabolic chambers to measure embryonic O(2) intake and CO(2) output. From these data, the respiratory quotient (RQ) and metabolic heat production were calculated. Data were analyzed by the GLM procedure of SAS at P < or = 0.05. Neither strain nor flock age influenced conductance. Total embryonic O(2) consumption, CO(2) output, RQ, and metabolic heat production over the entire incubation period were not affected by strain. Daily differences existed between strains for embryonic O(2) intake (1, 7, 16, 17, 19, 20 d of incubation), CO(2) output (1 to 4, 16 to 20 d of incubation), and heat production (4, 7, 16 to 19 d of incubation). Embryos from young, mature, old, and very old flocks produced significantly more total embryonic heat over the entire 21 d (1,712, 1,677, 1,808, and 1,832, respectively) than embryos from peak (1,601) and postpeak (1,693) flocks. Average RQ for the entire incubation period was higher in embryos from mature flocks compared with all other flock ages. Daily differences among embryos from different flock ages were shown for O(2) consumption (all but d 8 of incubation), CO(2) production (all but d 7 and 9 of incubation), and heat output. The results showed that genetic strain and parent flock age influence daily embryonic metabolism, especially during the early and latter days of incubation. These daily differences coincide with the days of incubation having a higher incidence of embryonic mortality; these 2 factors may be related. Further investigation into the relationship between embryonic metabolic heat production and mortality during incubation may lead to the development of specific incubation conditions for different genetic strains and flock ages.

Dam line and sire line effects on turkey embryo survival and thyroid hormone concentrations at the plateau stage in oxygen consumption.

Inheritance of embryo thyroid function was measured in lines of turkeys. Two lines that had been selected for either increased egg production (E) or increased 16-wk BW (F) and their respective randombred controls (i.e., RBC1 and RBC2) were examined. Reciprocal crosses of dams and sires from each selected line and its randombred control were made to estimate sire line and dam line effects. Orthogonal contrasts were used to determine if the differences found were due to the presence of additive, nonadditive, or maternal, sex-linked, or both, gene effects. With the data involved, sex-linkage and maternal effects could not be separated. Embryo survival was measured for all lines and their reciprocal crosses. Crossing the RBC1 sire and E dam also resulted in better embryo survival and lower death losses at pipping than for the other cross- or purelines. Reciprocal crosses of the F and RBC2 lines showed better total embryo survival, and they survived pipping better than the F or RBC2 purelines. Thyroxine (T(4)) and triiodothyronine (T(3)) concentrations differed between the reciprocal crosses at external pipping, but the effects were inconsistent for the 2 data sets. Reciprocal tests indicated that maternal, sex-linked, or both, effects were present for T(3) concentrations at internal pipping in the E and RBC1 lines and at external pipping for the F and RBC2 lines. Reciprocal effects were significant for T(4) at internal pipping for both data sets. The RBC1 sire embryos had significantly higher T(3):T(4) ratios than the E line sire embryos at internal and external pipping, and the pureline RBC1 embryos had consistently higher ratios than the pureline E embryos. The differences for the T(3):T(4) ratios between these 2 lines at internal pipping, external pipping, and hatch appeared to be consistently additive in nature, although significant nonadditive or heterotic effects were present for the ratio at external pipping. Similar effects on the T(3):T(4) ratio were observed for the F and RBC2 lines at external pipping.

Follicular development and expression of the messenger ribonucleic acid for the inhibin/activin subunits in two genetic lines of turkey hens that differ in total egg production.

The characterization of the follicular hierarchy and the expression of the mRNA for the inhibin/activin subunits was investigated in the follicles of 2 lines of turkey hens selected for over 40 generations for increased egg production (Egg line) or increased body weight (Growth line). The follicular hierarchies of 6 hens from the Egg and Growth lines were characterized in middle (45 wk of age) and late production (58 wk of age). Relative follicular weights for individual hierarchical follicles (>12 mm), pooled small yellow follicles (5 to 12 mm), and large white follicles (2 to 5 mm) were calculated. Total RNA was extracted for Northern blot analysis from individual granulosa cell layers of the F1 through F4 follicles, and from the combined granulosa and theca layers of small yellow follicles and large white follicles from an additional 6 hens from each genetic line. Egg line hens displayed a more distinct follicular size hierarchy than Growth line hens at 45 and 58 wk. Although total follicular weight relative to body size was greater at 45 and 58 wk of age for the Egg line hens than the Growth line hens, the total number of hierarchical follicles was greater in the Growth line hens at 45 and 58 wk of age. Expression of follistatin and the inhibin beta(B)-subunit was highest in nonhierarchical follicles, whereas the expression of the inhibin alpha- and beta(A)-subunits was highest in the hierarchical follicles. The inhibin alpha- and beta(A)-subunit mRNA expression pattern in the 4 largest follicles of the Growth line hens was not similar to the Egg line hens or characteristic of laying hens that have a high rate of egg production. The unusual inhibin subunit mRNA expression in the largest hierarchical follicles of the Growth line hens may account for their development of an abnormal follicular size hierarchy and for their poor egg production.