Habituation and individual variation in the endocrine stress response in the Trinidadian guppy (Poecilia reticulata).

The vertebrate stress response enables individuals to react to and cope with environmental challenges. A crucial aspect of the stress response is the elevation of circulating glucocorticoids. However, continued activation of the stress response under repeated exposure to stressors can be damaging to fitness. Under certain circumstances it may therefore be adaptive to habituate to repeated exposures to a particular stressor by reducing the magnitude of any associated release of glucocorticoids. Here, we investigate whether Trinidadian guppies (Poecilia reticulata) habituate to repeated exposure to a mild stressor, using a waterborne hormone sampling approach that has previously been shown to elicit a stress response in small fish. We also test for individual variation in the extent of habituation to this stressor. Concentrating on freely circulating cortisol, we found that the first exposure to the assay induced high cortisol release rates but that guppies tended to habituate quickly to subsequent exposures. There were consistent differences among individuals in their average cortisol release rate (after accounting for effects of variables such as body size) over repeated exposures. Our analyses did not find evidence of individual differences in habituation rate, although limitations in statistical power could account for this finding. We repeated the analysis for free 11-ketotestosterone, which can also respond to stressors, but found no obvious habituation pattern and no among-individual variation. We also present data on conjugated forms of both hormones, which were repeatable but did not show the expected time-lagged habituation effect. We discuss consistent individual differences around the general pattern of habituation in the flexible stress response, and highlight the potential for individual variation in habituation to facilitate selection against the deleterious effects of chronic stress.

Nasal and sinus symptoms and chronic rhinosinusitis in a population-based sample.

BACKGROUND: The objective of this study was to describe the first US-based study to use the European Position Paper on Rhinosinusitis (EPOS) criteria to study the prevalence of chronic rhinosinusitis (CRS) in a general-population sample. METHODS: A CRS symptom questionnaire was mailed to 23 700 primary care patients from Geisinger Clinic, a health system serving 45 counties in Pennsylvania. CRS cases were categorized into four unique subgroups based on EPOS symptoms: obstruction and discharge with no smell loss or pain/pressure; smell loss without pain/pressure; facial pain and/or pressure without smell loss; and both smell loss and pain/pressure. All cases were required to have nasal obstruction or discharge. Logistic regression was used to evaluate potential factors associated with CRS subgroups. RESULTS: We found that 11.9% of patients met criteria for CRS. Prevalence peaked at 15.9% between ages 50 and 59 years and then dropped to 6.8% after age 69. The odds of CRS was higher among patients who were white, younger, smokers, had a history of Medical Assistance, and had other diseases. When CRS subgroups were modeled separately, these associations were no longer significant for some CRS subgroups. Comorbid diseases were most strongly associated with CRS cases who reported smell loss and facial pain and/or pressure and had the weakest associations with CRS cases who did not report these symptoms. CONCLUSIONS: CRS is a highly prevalent and heterogeneous condition. Differences in risk factors and health outcomes across symptom subgroups may be indicative of differences in etiology that have implications for disease management.

Fundamental problems with the cooperative breeding hypothesis. A reply to Burkart & van Schaik.

The cooperative breeding hypothesis (CBH) states that cooperative breeding, a social system in which group members help to rear offspring that are not their own, has important socio-cognitive consequences. Thornton & McAuliffe (2015; henceforth T&M) critiqued this idea on both conceptual and empirical grounds, arguing that there is no reason to predict that cooperative breeding should favour the evolution of enhanced social cognition or larger brains, nor any clear evidence that it does. In response to this critique, Burkart & van Schaik (2016 henceforth B&vS) attempt to clarify the causal logic of the CBH, revisit the data and raise the possibility that the hypothesis may only apply to primates. They concede that cooperative breeding is unlikely to generate selection pressures for enhanced socio-cognitive abilities, but argue instead that the CBH operates purely through cooperative breeding reducing social or energetic constraints. Here, we argue that this revised hypothesis is also untenable because: (1) it cannot explain why resources so released would be allocated to cognitive traits per se rather than any other fitness-related traits, (2) key assumptions are inconsistent with available evidence and (3) ambiguity regarding the predictions leaves it unclear what evidence would be required to falsify it. Ultimately, the absence of any compelling evidence that cooperative breeding is associated with elevated cognitive ability or large brains (indeed data suggest the opposite is true in non-human primates) also casts doubt on the capacity of the CBH to explain variation in cognitive traits.

Elevated glucocorticoid concentrations during gestation predict reduced reproductive success in subordinate female banded mongooses.

Dominant females in social species have been hypothesized to reduce the reproductive success of their subordinates by inducing elevated circulating glucocorticoid (GC) concentrations. However, this 'stress-related suppression' hypothesis has received little support in cooperatively breeding species, despite evident reproductive skews among females. We tested this hypothesis in the banded mongoose (Mungos mungo), a cooperative mammal in which multiple females conceive and carry to term in each communal breeding attempt. As predicted, lower ranked females had lower reproductive success, even among females that carried to term. While there were no rank-related differences in faecal glucocorticoid (fGC) concentrations prior to gestation or in the first trimester, lower ranked females had significantly higher fGC concentrations than higher ranked females in the second and third trimesters. Finally, females with higher fGC concentrations during the third trimester lost a greater proportion of their gestated young prior to their emergence from the burrow. Together, our results are consistent with a role for rank-related maternal stress in generating reproductive skew among females in this cooperative breeder. While studies of reproductive skew frequently consider the possibility that rank-related stress reduces the conception rates of subordinates, our findings highlight the possibility of detrimental effects on reproductive outcomes even after pregnancies have become established.

Broad line emission from iron K- and L-shell transitions in the active galaxy 1H 0707-495.

Since the 1995 discovery of the broad iron K-line emission from the Seyfert galaxy MCG-6-30-15 (ref. 1), broad iron K lines have been found in emission from several other Seyfert galaxies, from accreting stellar-mass black holes and even from accreting neutron stars. The iron K line is prominent in the reflection spectrum created by the hard-X-ray continuum irradiating dense accreting matter. Relativistic distortion of the line makes it sensitive to the strong gravity and spin of the black hole. The accompanying iron L-line emission should be detectable when the iron abundance is high. Here we report the presence of both iron K and iron L emission in the spectrum of the narrow-line Seyfert 1 galaxy 1H 0707-495. The bright iron L emission has enabled us to detect a reverberation lag of about 30 s between the direct X-ray continuum and its reflection from matter falling into the black hole. The observed reverberation timescale is comparable to the light-crossing time of the innermost radii around a supermassive black hole. The combination of spectral and timing data on 1H 0707-495 provides strong evidence that we are witnessing emission from matter within a gravitational radius, or a fraction of a light minute, from the event horizon of a rapidly spinning, massive black hole.

Effects of feeding birdsfoot trefoil hay on neutral detergent fiber digestion, nitrogen utilization efficiency, and lactational performance by dairy cows.

This experiment was conducted to determine effects of feeding birdsfoot trefoil hay-based diets in comparison with an alfalfa hay-based diet on N utilization efficiency, ruminal fermentation, and lactational performance by mid-lactation dairy cows. Nine multiparous lactating Holstein cows (131 ± 22.6 d in milk), 3 of which were rumen fistulated, were fed 3 experimental diets in a replicated 3 × 3 Latin square design with 3 periods of 14 d of adaptation and 7 d of data and sample collection. Within squares, cows were randomly assigned to diets as follows: alfalfa hay-based diet (AHT), alfalfa and birdsfoot trefoil hay-based diet (ABT), and birdsfoot trefoil hay-based diet (BT). Intakes of dry matter and crude protein were similar across treatments, whereas ABT and BT diets resulted in decreased fiber intake compared with AHT. Feeding BT tended to increase neutral detergent fiber digestibility compared with AHT and ABT. Milk yield tended to increase for cows consuming ABT or BT diets. Milk true protein concentration and yield were greater for cows consuming ABT relative to those fed AHT. Concentration of total volatile fatty acids tended to increase by cows fed BT compared with those fed AHT and ABT. Feeding birdsfoot trefoil hay in a total mixed ration resulted in a tendency to decrease acetate proportion, but it tended to increase propionate proportion, leading to a tendency to decrease acetate-to-propionate ratio. Whereas concentration of ammonia-N was similar across treatments, cows offered BT exhibited greater microbial protein yield relative to those fed AHT and ABT. Cows offered birdsfoot trefoil hay diets secreted more milk N than AHT, resulting in improved N utilization efficiency for milk N. The positive effects due to feeding birdsfoot trefoil hay were attributed to enhanced neutral detergent fiber digestion, and thus it could replace alfalfa hay in high-forage dairy diets while improving N utilization efficiencies and maintaining lactational performance compared with alfalfa hay.

Whole-body protein turnover response to short-term high-protein diets during weight loss: a randomized controlled trial.

To determine whole-body protein turnover responses to high-protein diets during weight loss, 39 adults (age, 21±1 years; VO2peak, 48±1 ml kg(-1) min(-1); body mass index, 25±1 kg m(2)) were randomized to diets providing protein at the recommend dietary allowance (RDA), 2 × -RDA or 3 × -RDA. A 10-day weight maintenance period preceded a 21-day, 40% energy deficit. Postabsorptive (FASTED) and postprandial (FED) whole-body protein turnover was determined during weight maintenance (day 10) and energy deficit (day 31) using [1-(13)C]leucine. FASTED flux, synthesis and breakdown were lower (P<0.05) for energy deficit than weight maintenance. Protein flux and synthesis were higher (P<0.05) for FED than FASTED. Feeding attenuated (P<0.05) breakdown during weight maintenance but not energy deficit. Oxidation increased (P<0.05) between dietary protein levels and feeding stimulated oxidation, although oxidative responses to feeding were higher (P<0.05) for energy deficit than weight maintenance. FASTED net balance decreased between dietary protein levels, but in the FED state, net balance was lower for 3 × -RDA as compared with RDA and 2 × -RDA (diet-by-state, P<0.05). Consuming dietary protein at levels above the RDA, particularly 3 × -RDA, during short-term weight loss increases protein oxidation with concomitant reductions in net protein balance.

Effects of altering alfalfa hay quality when feeding steam-flaked versus high-moisture corn grain on ruminal fermentation and lactational performance of dairy cows.

This experiment was performed to test a hypothesis that nutritive benefits of feeding high-moisture corn (HMC) would be different when fed with different qualities of alfalfa hay (AH) due to associative effects on ruminal fermentation and nutrient utilization efficiency. Eight multiparous lactating Holstein cows were used; 4 were surgically fitted with ruminal cannulas. Days in milk averaged 184 ± 10.7 at the start of the experiment. The experiment was performed in a duplicate 4 × 4 Latin square design. Within each square, cows were randomly assigned to a sequence of 4 diets during each of the four 21-d periods (14 d of treatment adaptation and 7 d of data collection and sampling). A 2 × 2 factorial arrangement was used; fair-quality AH [FAH; 39.6% neutral detergent fiber (NDF) and 17.9% crude protein (CP)] or high-quality AH (HAH; 33.6% NDF and 21.9% CP) was combined with steam-flaked corn (SFC) or HMC to form 4 treatments: FAH with SFC, FAH with HMC, HAH with SFC, and HAH with HMC. The AH was fed at 32% dry matter (DM) content, whereas SFC or HMC was included at 17% DM content. Quality of AH did not affect DM intake, whereas feeding HMC decreased DM intake, regardless of quality of AH. Digestibility of DM was greater for cows fed HAH compared with those fed FAH (70.1 vs. 67.6%). Digestibility of NDF increased by feeding HMC (67.6 vs. 58.4%), but not by quality of AH. Under FAH, starch digestibility decreased by feeding HMC compared with SFC (85.7 vs. 95.0%), but it was similar under HAH, resulting in an interaction between quality of AH and type of corn grain (CG). Feeding different qualities of AH did not affect milk yield; however, feeding HMC decreased milk yield in FAH diet, causing an AH × CG interaction. Efficiency of milk yield/DM intake was improved due to feeding HMC, regardless of the quality of the AH. In addition, dietary N utilization for milk N tended to increase by feeding HMC, but it was not influenced by quality of AH. Yield of microbial protein increased by feeding HAH diets compared with FAH diets, whereas feeding the HMC diet increased microbial protein yield under the HAH diet, leading to an interaction between and AH and CG. Overall results in this experiment indicate that feeding HMC in AH-based diets improved feed efficiency as well as N utilization efficiency, regardless of quality of AH.

Feeding protein supplements in alfalfa hay-based lactation diets improves nutrient utilization, lactational performance, and feed efficiency of dairy cows.

Due to the increasing cost of soybean meal and concerns of excess N being excreted into the environment, new protein supplements have been developed. Two products that have shown potential in increasing N utilization efficiency are slow-release urea (SRU; Optigen; Alltech Inc., Nicholasville, KY) and ruminal-escape protein derived from yeast (YMP; DEMP; Alltech Inc.). The objective of this study was to assess the effects of feeding these 2 supplements in alfalfa hay-based [45.7% of forage dietary dry matter (DM)] dairy diets on nutrient utilization, feed efficiency, and lactational performance of dairy cows. Twelve multiparous dairy cows were used in a triple 4 × 4 Latin square design with one square consisting of ruminally cannulated cows. Treatments included (1) control, (2) SRU-supplemented total mixed ration (SRUT), (3) YMP-supplemented total mixed ration (YMPT), and (4) SRU- and YMP-supplemented total mixed ration (SYT). The control consisted only of a mixture of soybean meal and canola meal in a 50:50 ratio. The SRU and the YMP were supplemented at 0.49 and 1.15% DM, respectively. The experiment consisted of 4 periods lasting 28 d each (21 d of adaptation and 7 d of sampling). Cows fed YMPT and SYT had decreased intake of DM, and all supplemented treatments had lower crude protein intake compared with those fed the control. Milk yield tended to have the greatest increase in YMPT compared with the control (41.1 vs. 39.7 kg/d) as well as a tendency for increased milk fat and protein yields. Feed efficiencies based on yields of milk, 3.5% fat-corrected milk, and energy-corrected milk increased at 10 to 16% due to protein supplementation. Cows fed protein supplements partitioned less energy toward body weight gain, but tended to partition more energy toward milk production. Efficiency of use of feed N to milk N increased by feeding SRUT and YMPT, and milk N-to-manure N ratio increased with YMPT. Overall results from this experiment indicate that replacing the mixture of soybean meal and canola meal with SRU and YMP in alfalfa hay-based dairy diets can be a good approach to improve nutrient utilization efficiencies in lactating dairy cows.

Extra-group mating increases inbreeding risk in a cooperatively breeding bird.

In many cooperatively breeding species, females mate extra-group, the adaptive value of which remains poorly understood. One hypothesis posits that females employ extra-group mating to access mates whose genotypes are more dissimilar to their own than their social mates, so as to increase offspring heterozygosity. We test this hypothesis using life history and genetic data from 36 cooperatively breeding white-browed sparrow weaver (Plocepasser mahali) groups. Contrary to prediction, a dominant female's relatedness to her social mate did not drive extra-group mating decisions and, moreover, extra-group mating females were significantly more related to their extra-group sires than their social mates. Instead, dominant females were substantially more likely to mate extra-group when paired to a dominant male of low heterozygosity, and their extra-group mates (typically dominants themselves) were significantly more heterozygous than the males they cuckolded. The combined effects of mating with extra-group males of closer relatedness, but higher heterozygosity resulted in extra-group-sired offspring that were no more heterozygous than their within-group-sired half-siblings. Our findings are consistent with a role for male-male competition in driving extra-group mating and suggest that the local kin structure typical of cooperative breeders could counter potential benefits to females of mating extra-group by exposing them to a risk of inbreeding.

Effects of feeding brown midrib corn silage with a high dietary concentration of alfalfa hay on lactational performance of Holstein dairy cows for the first 180 days of lactation.

This experiment was conducted to test a hypothesis that lactating dairy cows fed 35% brown midrib (BMR) corn silage and 25% alfalfa hay (dry matter (DM) basis) would consume more DM around peak lactation compared with those fed conventional corn silage (CS), resulting in longer peak milk production. Twenty-eight multiparous Holstein cows were used starting at the onset of lactation through 180 d in milk (DIM). Treatments were formulated to maintain a forage-to-concentrate ratio of 60:40, differing only in the CS hybrids used. Two dietary treatments were assessed in a completely randomized design: total mixed ration based on conventional CS (CCS) and total mixed ration based on BMR silage. Through peak lactation (1-60 DIM), DM intake was not different between dietary treatments, whereas DM intake post-peak lactation (61-180 DIM) tended to increase by feeding the BMR diet compared with the CCS diet (25.8 vs. 24.7 kg/d). Cows fed the BMR diet tended to lose less body weight through peak lactation compared with those fed the CCS diet (-0.22 vs. -0.52 kg/d). Although milk yield was not different between dietary treatments through peak lactation, milk yield post-peak lactation increased by feeding the BMR diet compared with the CCS diet (41.0 vs. 38.8 kg/d). Yield of 3.5% fat-corrected milk was similar between dietary treatments throughout the experiment (41.4 kg/d, on average), but milk fat concentration decreased by feeding the BMR diet compared with the CCS diet post-peak lactation (3.47 vs. 3.80%). Overall milk protein concentration was similar between dietary treatments throughout the experiment (2.96%, on average), whereas milk protein yield tended to be higher for the BMR diet post-peak lactation compared with the CCS diet (1.19 vs.1.13 kg/d). Feeding BMR silage with a high dietary concentration of alfalfa hay maintained more body weight, but did not affect milk production through peak lactation; however, cows fed the BMR diet post-peak lactation consumed more feed and maintained longer peak milk yield, leading to greater overall milk production and milk protein yield.

Corn silage hybrid type and quality of alfalfa hay affect dietary nitrogen utilization by early lactating dairy cows.

This experiment was conducted to determine the effects of corn silage (CS) hybrids and quality of alfalfa hay (AH) in high-forage dairy diets on N utilization, ruminal fermentation, and lactational performance by early-lactating dairy cows. Eight multiparous Holstein cows were used in a duplicated 4 × 4 Latin square experiment with a 2 × 2 factorial arrangement of dietary treatments. The 8 cows (average days in milk = 23 ± 11.2) were surgically fitted with ruminal cannula, and the 2 squares were conducted simultaneously. Within square, cows were randomly assigned to a sequence of 4 diets: conventional CS (CCS) or brown midrib CS (BMR) was combined with fair-quality AH [FAH: 46.7% neutral detergent fiber (NDF) and 18.4% crude protein (CP)] or high-quality AH (HAH: 39.2% NDF and 20.7% CP) to form 4 treatments: CCS with FAH, CCS with HAH, BMR with FAH, and BMR with HAH. Diets were isonitrogenous across treatments, averaging 15.9% CP. Each period lasted a total of 21 d, with 14 d for treatment adaptation and 7d for data collection and sampling. Intake of DM and milk yield did not differ in response to CS hybrids or AH quality. Although feeding BMR-based diets decreased urinary N output by 24%, it did not affect fecal N output. Feeding HAH decreased urinary N output by 15% but increased fecal N output by 20%. Nitrogen efficiency [milk N (g/d)/intake N (g/d)] tended to increase for BMR treatments. Ruminal ammonia-N concentration was lower for cows fed BMR-based diets than for those fed CCS-based diets but was not affected by quality of AH. Feeding BMR-based diets or HAH decreased milk urea N concentration by 23 or 15%, respectively, compared with CCS-based diets or FAH. Total volatile fatty acid concentration increased with HAH but was not influenced by CS hybrids. Feeding BMR-based diets decreased urinary N-to-fecal N ratio (UN:FN), and it was further reduced by feeding HAH. Although cows fed the BMR-based diets tended to increase milk N-to-manure N ratio, the quality of AH did not affect the ratio. The lower ratio of UN:FN with a higher ratio of milk N-to-manure N ratio for the BMR-based diets indicates that feeding BMR may reduce manure ammonia-N by reducing excretion of urinary N and increasing secretion of milk N per unit of manure N excreted.

Simultaneous determination of electrical conductivity and thickness of nonmagnetic metallic foils using two-sided multifrequency eddy current techniques.

In this paper, we describe a simple method for performing multifrequency eddy current characterization of free-standing uniform-thickness metallic foils using a forked inductive coil arrangement. The method involves measuring the mutual inductance between two coils when a foil is present between the coils, and when it is not present; the ratio of these mutual inductances is compared with an analytical solution, and foil conductivity, thickness, and sheet resistance are simultaneously estimated using numerical inversion and least-squares fitting. This method was used to characterize 34 non-ferrous metallic samples with thicknesses between 50 and 640 µm and with conductivities between 0.8 × 107 and 5.8 × 107 S/m. The estimated thicknesses from eddy current characterization agreed well with those measured using confocal optical techniques; the two approaches agreed to within 1 µm for samples that were thinner than 200 µm, and to within 0.5% for samples that had a thickness of 200 µm or greater. The estimated conductivities from eddy current characterization were in close agreement with expected values, given knowledge of the materials used. A particular strength of this approach is that the instrumentation needed is broadly available in research and development laboratories and the associated fixturing is easy to manufacture and assemble. A calibration procedure is described that can be used to reduce errors from geometric uncertainties. This calibration requires a sample that has only a known conductivity or thickness; both do not need to be known. The method described herein is likely extensible to conductivities and thickness well outside the ranges measured as part of this work.

Alcohol-associated risks for young adults with Type 1 diabetes: a narrative review.

AIM: To undertake a narrative review of the impact and pattern of alcohol consumption in young adults with Type 1 diabetes. DATA SOURCES: MEDLINE, EMBASE, PsycINFO, The Cochrane Library, Web of Science, meeting abstracts of the European Association for the Study of Diabetes, the American Diabetes Association and Diabetes UK, Current Controlled Trials, ClinicalTrials.gov, UK Clinical Research Network, scrutiny of bibliographies of retrieved papers and contact with experts in the field. INCLUSION CRITERIA: relevant studies of any design of alcohol consumption and young adults with Type 1 diabetes (age 14-25 years) were included. The key outcomes were the quantity, pattern and impact of alcohol consumption, the effect on diabetes control and the effect of interventions to minimize the risks of alcohol for this population. RESULTS: Six articles and two conference abstracts met the inclusion criteria. There were six cross-sectional studies, one qualitative study and one within-subjects design study. Quality of studies was variable. Alcohol use amongst young adults with Type 1 diabetes was reported to be common and potentially harmful. There was a paucity of evidence on interventions to minimize the risks of alcohol in this target group. CONCLUSIONS: Research is required to understand the social context of alcohol consumption in this population with a view to developing appropriate interventions to minimize the risks associated with its use.

Review of the relationship between milk urea nitrogen and days in milk, parity, and monthly temperature mean in Iranian Holstein cows.

The objectives of this study were to determine the relationships between milk urea N and days in milk, parity, and season in Iranian Holstein cows. Twelve Iranian commercial dairy herds participated in a 13-mo study from December 1, 2008, to December 31, 2009. All cows were milked 3 times daily, housed in freestalls, and fed a total mixed ration twice a day. Mean milk urea N over the study period was 16.0mg/dL. Mean milk urea N, categorized by 30-d increments of days in milk, paralleled changes in milk values and followed a curvilinear shape. However, milk urea N concentration reached a maximum at the fifth month of days in milk, but milk production reached a maximum at the third month. The concentration of milk urea N was lower during the first 30 d in milk category compared with all other days in milk categories. Overall mean milk urea N concentration of Holstein cows in the third and greater lactations was lower than in the first or second lactation. Milk urea N was at its lowest level in December (13 mg/dL), increased in the spring and summer months, and reached a maximum in July (18.8 mg/dL). From that point, milk urea N concentration progressively diminished to the autumn-winter level. In this study, milk urea N concentration was positively correlated with monthly temperature mean and may be a reason for the lower reproductive performance during the summer months. It has been recommended that milk urea N concentration should be evaluated in association with parity, days in milk, and season (or month). These variables should be considered potential sources of misinterpretation when exploring the relationship between milk urea N and nutritional management or measures of performance.

International Olympic Committee consensus statement on thermoregulatory and altitude challenges for high-level athletes.

Challenging environmental conditions, including heat and humidity, cold, and altitude, pose particular risks to the health of Olympic and other high-level athletes. As a further commitment to athlete safety, the International Olympic Committee (IOC) Medical Commission convened a panel of experts to review the scientific evidence base, reach consensus, and underscore practical safety guidelines and new research priorities regarding the unique environmental challenges Olympic and other international-level athletes face. For non-aquatic events, external thermal load is dependent on ambient temperature, humidity, wind speed and solar radiation, while clothing and protective gear can measurably increase thermal strain and prompt premature fatigue. In swimmers, body heat loss is the direct result of convection at a rate that is proportional to the effective water velocity around the swimmer and the temperature difference between the skin and the water. Other cold exposure and conditions, such as during Alpine skiing, biathlon and other sliding sports, facilitate body heat transfer to the environment, potentially leading to hypothermia and/or frostbite; although metabolic heat production during these activities usually increases well above the rate of body heat loss, and protective clothing and limited exposure time in certain events reduces these clinical risks as well. Most athletic events are held at altitudes that pose little to no health risks; and training exposures are typically brief and well-tolerated. While these and other environment-related threats to performance and safety can be lessened or averted by implementing a variety of individual and event preventative measures, more research and evidence-based guidelines and recommendations are needed. In the mean time, the IOC Medical Commission and International Sport Federations have implemented new guidelines and taken additional steps to mitigate risk even further.

A novel, noninvasive transdermal fluid sampling methodology: IGF-I measurement following exercise.

This study tested the hypothesis that transdermal fluid (TDF) provides a more sensitive and accurate measure of exercise-induced increases in insulin-like growth factor-I (IGF-I) than serum, and that these increases are detectable proximal, but not distal, to the exercising muscle. A novel, noninvasive methodology was used to collect TDF, followed by sampling of total IGF-I (tIGF-I) and free IGF-I (fIGF-I) in TDF and serum following an acute bout of exercise. Experiment 1: eight men (23 ± 3 yrs, 79 ± 7 kg) underwent two conditions (resting and 60 min of cycling exercise at 60% Vo(2)(peak)) in which serum and forearm TDF were collected for comparison. There were no significant changes in tIGF-I or fIGF-I in TDF obtained from the forearm or from serum following exercise (P > 0.05); however, the proportion of fIGF-I to tIGF-I in TDF was approximately fourfold greater than that of serum (P ≤ 0.05). These data suggest that changes in TDF IGF-I are not evident when TDF is sampled distal from the working tissue. To determine whether exercise-induced increases in local IGF-I could be detected when TDF was sampled directly over the active muscle group, we performed a second experiment. Experiment 2: fourteen subjects (22 ± 4 yr, 68 ± 11 kg) underwent an acute plyometric exercise condition consisting of 10 sets of 10 plyometric jumps with 2-min rest between sets. We observed a significant increase in TDF tIGF-I following exercise (P ≤ 0.05) but no change in serum tIGF-I (P > 0.05). Overall, these data suggest that TDF may provide a noninvasive means of monitoring acute exercise-induced changes in local IGF-I when sampled in proximity to exercising muscles. Moreover, our finding that the proportion of free to tIGF-I was greater in TDF than in serum suggests that changes in local IGF-I may be captured more readily using this system.

Effects of supplementing condensed tannin extract on intake, digestion, ruminal fermentation, and milk production of lactating dairy cows.

A lactation experiment was conducted to determine the influence of quebracho condensed tannin extract (CTE) on ruminal fermentation and lactational performance of dairy cows. The cows were fed a high forage (HF) or a low forage (LF) diet with a forage-to-concentrate ratio of 59:41 or 41:59 on a dry matter (DM) basis, respectively. Eight multiparous lactating Holstein cows (62 ± 8.8 d in milk) were used. The design of the experiment was a double 4 × 4 Latin square with a 2 × 2 factorial arrangement of treatments, and each period lasted 21 d (14 d of treatment adaptation and 7 d of data collection and sampling). Four dietary treatments were tested: HF without CTE, HF with CTE (HF+CTE), LF without CTE, and LF with CTE (LF+CTE). Commercial quebracho CTE was added to the HF+CTE and the LF+CTE at a rate of 3% of dietary DM. Intake of DM averaged 26.7 kg/d across treatments, and supplementing CTE decreased intakes of DM and nutrients regardless of forage level. Digestibilities of DM and nutrients were not affected by CTE supplementation. Milk yield averaged 35.3 kg/d across treatments, and yields of milk and milk component were not influenced by CTE supplementation. Negative effects of CTE supplementation on feed intake resulted in increased feed efficiency (milk yield/DM intake). Although concentration of milk urea N (MUN) decreased by supplementing CTE in the diets, efficiency of N use for milk N was not affected by CTE supplementation. Feeding the LF diet decreased ruminal pH (mean of 6.47 and 6.33 in HF and LF, respectively). However, supplementation of CTE in the diets did not influence ruminal pH. Supplementing CTE decreased total volatile fatty acid concentration regardless of level of forage. With CTE supplementation, molar proportions of acetate, propionate, and butyrate increased in the HF diet, but not in the LF diet, resulting in interactions between forage level and CTE supplementation. Concentration of ammonia-N tended to decrease with supplementation of CTE. The most remarkable finding in this study was that cows fed CTE-supplemented diets had decreased ruminal ammonia-N and MUN concentrations, indicating that less ruminal N was lost as ammonia because of decreased degradation of crude protein by rumen microorganisms in response to CTE supplementation. Therefore, supplementation of CTE in lactation dairy diets may change the route of N excretion, having less excretion into urine but more into feces, as it had no effect on N utilization efficiency for milk production.

Ruminal fermentation, milk fatty acid profiles, and productive performance of Holstein dairy cows fed 2 different safflower seeds.

A lactation trial was conducted to determine the effects of supplementing whole safflower seeds (SS) on ruminal fermentation, lactational performance, and milk fatty acid (FA) profiles. Nine multiparous Holstein cows (days in milk = 110 ± 20) were used in a replicated 3 × 3 Latin square design. Each period lasted 21 d, with 14 d of adaptation and 7 d of data collection. Within square, cows were randomly assigned to a sequence of 3 dietary treatments as follows: cottonseed total mixed ration (TMR; CST), conventional SS (variety S-208) TMR (CSST), and NutraSaff SS (Safflower Technologies International, Sidney, MT) TMR (NSST). Diets contained approximately 63% forage (36% alfalfa hay, 4% grass hay, and 23% corn silage) and 37% concentrate supplemented with 2% cottonseed to the CST and 3% conventional or NutraSaff SS to the CSST or the NSST, respectively. Intake of dry matter (DM) averaged 21.8 kg/d and did not differ across diets, but feeding the NSST decreased intake of neutral detergent fiber (NDF) due to lower dietary concentration of NDF in the NSST. Digestibilities of DM and nutrients were similar among treatments. No differences in yields of milk or milk components were observed in response to supplementing SS. Dietary treatments did not affect ruminal pH, total or molar proportions of ruminal volatile FA, and ammonia-N. However, cows fed SS had a higher molar proportion of isobutyrate than those fed the CST diet. Ruminal C16:0 FA concentration increased with the CST, whereas C18:1 cis-9 and C18:2 n-6 tended to increase with SS supplementation, indicating that conventional and NutraSaff SS were partially protected from microbial biohydrogenation. Supplementing SS decreased milk C16:0 concentration, whereas it increased C18:1 cis-9 and C18:1 trans-9. Milk FA C18:1 trans-11 and cis-9, trans-11 conjugated linoleic acid increased and tended to increase with feeding the NSST, respectively, but not the CSST diet. In conclusion, supplementing diets with whole SS at 3% of dietary DM can be an effective strategy of fat supplementation to lactating dairy cows without negative effects on lactational performance and milk FA profiles.

Effects of corn silage hybrids and dietary nonforage fiber sources on feed intake, digestibility, ruminal fermentation, and productive performance of lactating Holstein dairy cows.

This experiment was conducted to determine the effects of corn silage hybrids and nonforage fiber sources (NFFS) in high forage diets formulated with high dietary proportions of alfalfa hay (AH) and corn silage (CS) on ruminal fermentation and productive performance by early lactating dairy cows. Eight multiparous Holstein cows (4 ruminally fistulated) averaging 36±6.2 d in milk were used in a duplicated 4 × 4 Latin square design experiment with a 2 × 2 factorial arrangement of treatments. Cows were fed 1 of 4 dietary treatments during each of the four 21-d replicates. Treatments were (1) conventional CS (CCS)-based diet without NFFS, (2) CCS-based diet with NFFS, (3) brown midrib CS (BMRCS)-based diet without NFFS, and (4) BMRCS-based diet with NFFS. Diets were isonitrogenous and isocaloric. Sources of NFFS consisted of ground soyhulls and pelleted beet pulp to replace a portion of AH and CS in the diets. In vitro 30-h neutral detergent fiber (NDF) degradability was greater for BMRCS than for CCS (42.3 vs. 31.2%). Neither CS hybrids nor NFFS affected intake of dry matter (DM) and nutrients. Digestibility of N, NDF, and acid detergent fiber tended to be greater for cows consuming CCS-based diets. Milk yield was not influenced by CS hybrids and NFFS. However, a tendency for an interaction between CS hybrids and NFFS occurred, with increased milk yield due to feeding NFFS with the BMRCS-based diet. Yields of milk fat and 3.5% fat-corrected milk decreased when feeding the BMRCS-based diet, and a tendency existed for an interaction between CS hybrids and NFFS because milk fat concentration further decreased by feeding NFFS with BMRCS-based diet. Although feed efficiency (milk/DM intake) was not affected by CS hybrids and NFFS, an interaction was found between CS hybrids and NFFS because feed efficiency increased when NFFS was fed only with BMRCS-based diet. Total volatile fatty acid production and individual molar proportions were not affected by diets. Dietary treatments did not influence ruminal pH profiles, except that duration (h/d) of pH <5.8 decreased when NFFS was fed in a CCS-based diet but not in a BMRCS-based diet, causing a tendency for an interaction between CS hybrids and NFFS. Overall measurements in our study reveal that high forage NDF concentration (20% DM on average) may eliminate potentially positive effects of BMRCS. In the high forage diets, NFFS exerted limited effects on productive performance when they replaced AH and CS. Although the high quality AH provided adequate NDF (38.3% DM) for optimal rumen fermentative function, the low NDF concentration of the AH and the overall forage particle size reduced physically effective fiber and milk fat concentration.