Effects of phenylephrine on systemic and cerebral circulations in humans: a systematic review with mechanistic explanations.

We conducted a systematic review of the literature reporting phenylephrine-induced changes in blood pressure, cardiac output, cerebral blood flow and cerebral tissue oxygen saturation as measured by near-infrared spectroscopy in humans. We used the proportion change of the group mean values reported by the original studies in our analysis. Phenylephrine elevates blood pressure whilst concurrently inducing a reduction in cardiac output. Furthermore, despite increasing cerebral blood flow, it decreases cerebral tissue oxygen saturation. The extent of phenylephrine's influence on cardiac output (r = -0.54 and p = 0.09 in awake humans; r = -0.55 and p = 0.007 in anaesthetised humans), cerebral blood flow (r = 0.65 and p = 0.002 in awake humans; r = 0.80 and p = 0.003 in anaesthetised humans) and cerebral tissue oxygen saturation (r = -0.72 and p = 0.03 in awake humans; r = -0.24 and p = 0.48 in anaesthetised humans) appears closely linked to the magnitude of phenylephrine-induced blood pressure changes. When comparing the effects of phenylephrine in awake and anaesthetised humans, we found no evidence of a significant difference in cardiac output, cerebral blood flow or cerebral tissue oxygen saturation. There was also no evidence of a significant difference in effect on systemic and cerebral circulations whether phenylephrine was given by bolus or infusion. We explore the underlying mechanisms driving the phenylephrine-induced cardiac output reduction, cerebral blood flow increase and cerebral tissue oxygen saturation decrease. Individualised treatment approaches, close monitoring and consideration of potential risks and benefits remain vital to the safe and effective use of phenylephrine in acute care.

Phylogenetic convergence and multiple shell shape optima for gliding scallops (Bivalvia: Pectinidae).

An important question in evolutionary biology is how often, and to what extent, do similar ecologies elicit distantly related taxa to evolve towards the same phenotype? In some scenarios, the repeated evolution of particular phenotypes may be expected, for instance when species are exposed to common selective forces that result from strong functional demands. In bivalved scallops (Pectinidae), some species exhibit a distinct swimming behaviour (gliding), which requires specific biomechanical attributes to generate lift and reduce drag during locomotive events. Further, a phylogenetic analysis revealed that gliding behaviour has independently evolved at least four times, which raises the question as to whether these independent lineages have also converged on a similar phenotype. Here, we test the hypothesis that gliding scallops display shell shape convergence using a combination of geometric morphometrics and phylogenetic comparative methods that evaluate patterns of multivariate trait evolution. Our findings reveal that the gliding species display less morphological disparity and significant evolutionary convergence in morphospace, relative to expectations under a neutral model of Brownian motion for evolutionary phenotypic change. Intriguingly, the phylomorphospace patterns indicate that gliding lineages follow similar evolutionary trajectories to not one, but two regions of morphological space, and subsequent analyses identified significant differences in their biomechanical parameters, suggesting that these two groups of scallops accomplish gliding in different ways. Thus, whereas there is a clear gliding morphotype that has evolved convergently across the phylogeny, functionally distinct morphological subforms are apparent, suggesting that there may be two optima for the gliding phenotype in the Pectinidae.

Potential rapid evolution of foot morphology in Italian plethodontid salamanders (Hydromantes strinatii) following the colonization of an artificial cave.

How organisms respond to environmental change is a long-standing question in evolutionary biology. Species invading novel habitats provide an opportunity to examine contemporary evolution in action and decipher the pace of evolutionary change over short timescales. Here, we characterized phenotypic evolution in the Italian plethodontid salamander, Hydromantes strinatii, following the recent colonization of an artificial cave by a forest floor population. When compared with a nearby and genetically related population in the natural forest floor and a nearby cave population, the artificial cave population displayed significant differences in overall foot shape, with more interdigital webbing relative to the other populations. Further, this population evolved significantly larger feet, which corresponded more closely to those found in other cave populations than to forest floor populations to which the cave population is closely related. Finally, we quantified the rate of evolution for both foot shape and foot area, and found that both traits displayed large and significant evolutionary rates, at levels corresponding to other classic cases of rapid evolution in vertebrates. Together, these findings reveal that the response to novel environmental pressures can be large and rapid and that the anatomical shifts observed in the artificial cave population of H. strinatii may represent a case of rapid evolution in response to novel environmental pressures.

Batesian mimics influence the evolution of conspicuousness in an aposematic salamander.

Conspicuousness, or having high contrast relative to the surrounding background, is a common feature of unpalatable species. Several hypotheses have been proposed to explain the occurrence of conspicuousness, and while most involve the role of conspicuousness as a direct signal of unpalatability to potential predators, one hypothesis suggests that exaggerated conspicuousness may evolve in unpalatable species to reduce predator confusion with palatable species (potential Batesian mimics). This hypothesis of antagonistic coevolution between palatable and unpalatable species hinges on the 'cost of conspicuousness', in which conspicuousness increases the likelihood of predation more in palatable species than in unpalatable species. Under this mimicry scenario, four patterns are expected: (i) mimics will more closely resemble local models than models from other localities, (ii) there will be a positive relationship between mimic and model conspicuousness, (iii) models will be more conspicuous in the presence of mimics, and (iv) when models and mimics differ in conspicuousness, mimics will be less conspicuous than models. We tested these predictions in the salamander mimicry system involving Notophthalmus viridescens (model) and one colour morph of Plethodon cinereus (mimic). All predictions were supported, indicating that selection for Batesian mimicry not only influences the evolution of mimics, but also the evolution of the models they resemble. These findings indicate that mimicry plays a large role in the evolution of model warning signals, particularly influencing the evolution of conspicuousness.

Ecomorphological variation in male and female wall lizards and the macroevolution of sexual dimorphism in relation to habitat use.

Understanding how phenotypic diversity evolves is a major interest of evolutionary biology. Habitat use is an important factor in the evolution of phenotypic diversity of many animal species. Interestingly, male and female phenotypes have been frequently shown to respond differently to environmental variation. At the macroevolutionary level, this difference between the sexes is frequently analysed using phylogenetic comparative tools to assess variation in sexual dimorphism (SD) across taxa in relation to habitat. A shortcoming of such analyses is that they evaluate the degree of dimorphism itself and therefore they do not provide access to the evolutionary trajectories of each sex. As such, the relative contribution of male and female phenotypes on macroevolutionary patterns of sexual dimorphism cannot be directly assessed. Here, we investigate how habitat use shapes phenotypic diversity in wall lizards using phylogenetic comparative tools to simultaneously assess the tempo and mode of evolution in males, females and the degree of sexual dimorphism. We find that both sexes have globally diversified under similar, but not identical, processes, where habitat use seems to drive macroevolutionary variation in head shape, but not in body size or relative limb length. However, we also observe small differences in the evolutionary dynamics of male and female phenotypes that have a marked impact on macroevolutionary patterns of SD, with important implications for our interpretation of what drives phenotypic diversification within and between the sexes.

A method for analysis of phenotypic change for phenotypes described by high-dimensional data.

The analysis of phenotypic change is important for several evolutionary biology disciplines, including phenotypic plasticity, evolutionary developmental biology, morphological evolution, physiological evolution, evolutionary ecology and behavioral evolution. It is common for researchers in these disciplines to work with multivariate phenotypic data. When phenotypic variables exceed the number of research subjects--data called 'high-dimensional data'--researchers are confronted with analytical challenges. Parametric tests that require high observation to variable ratios present a paradox for researchers, as eliminating variables potentially reduces effect sizes for comparative analyses, yet test statistics require more observations than variables. This problem is exacerbated with data that describe 'multidimensional' phenotypes, whereby a description of phenotype requires high-dimensional data. For example, landmark-based geometric morphometric data use the Cartesian coordinates of (potentially) many anatomical landmarks to describe organismal shape. Collectively such shape variables describe organism shape, although the analysis of each variable, independently, offers little benefit for addressing biological questions. Here we present a nonparametric method of evaluating effect size that is not constrained by the number of phenotypic variables, and motivate its use with example analyses of phenotypic change using geometric morphometric data. Our examples contrast different characterizations of body shape for a desert fish species, associated with measuring and comparing sexual dimorphism between two populations. We demonstrate that using more phenotypic variables can increase effect sizes, and allow for stronger inferences.

Mid-infrared designer metals.

We demonstrate the potential of highly-doped semiconductor epilayers as building blocks for mid-infrared plasmonic structures. InAs epilayers are grown by molecular beam epitaxy and characterized by Hall measurements and optical techniques. We show that the plasma frequency of our material can be controlled across a broad range of mid-infrared frequencies. Subwavelength disks are fabricated out of our material, and localized plasmonic resonances are observed from these structures. Experimental results are compared to both numerical simulations and a simple quasistatic dipole model of our disks with good agreement.

Ecological radiation with limited morphological diversification in salamanders.

A major goal of evolutionary biology is to explain morphological diversity among species. Many studies suggest that much morphological variation is explained by adaptation to different microhabitats. Here, we test whether morphology and microhabitat use are related in plethodontid salamanders, which contain the majority of salamander species, and have radiated into a striking diversity of microhabitats. We obtained microhabitat data for 189 species that also had both morphometric and phylogenetic data. We then tested for associations between morphology and microhabitat categories using phylogenetic comparative methods. Associations between morphology and ecology in plethodontids are largely confined to a single clade within one subfamily (Bolitoglossinae), whereas variation in morphology across other plethodontids is unrelated to microhabitat categories. These results demonstrate that ecological radiation and morphological evolution can be largely decoupled in a major clade. The results also offer a striking contrast to lizards, which typically show close relationships between morphology and microhabitat.

Funneling light through a subwavelength aperture with epsilon-near-zero materials.

We present a comprehensive study of enhanced light funneling through a subwavelength aperture with realistic (lossy) epsilon-near-zero (ENZ) materials. We realize experimentally an inclusion-free ENZ material layer operating at optical frequencies and characterize its performance. An analytical expression describing light funneling through several structures involving ENZ coupling layers is developed, validated with numerical solutions of Maxwell equations, and utilized to relate the performance of the ENZ coupling systems to their main limiting factor, material losses.

Multiscale beam evolution and shaping in corrugated plasmonic systems.

We analyze, theoretically and experimentally, the dynamics of the wavepackets in plasmonic beaming devices, and show that the beam evolution in this class of structures is a multiscale phenomenon, which initiates in the near-field proximity of the device, develops continuously over a new length scale many times the wavelength of the light, and is completed well into the far-field of the system. We develop a quantitative description of the light evolution in the beaming structures and verify our theoretical predictions with experiments. Our analytical results are utilized to develop plasmonic geometries for shaping the mid-field beam evolution, and experimental results from these structures are demonstrated.

Selective thermal emission from patterned steel.

Patterned metal films have been shown to possess unique optical properties resulting from the excitation of surface plasmon polaritons at the patterned metal surface. Here we demonstrate spectrally selective thermal emission from patterned steel substrates. The materials and processes used in this work were chosen for their potential scalability to large-area and low cost production of metal films with distinct and designable thermal signatures. The samples studied were characterized by reflection and emission spectroscopy, and a factor of 2.6 emission enhancement is demonstrated for the design wavelength. These results are compared to numerical simulations.

Winter grazing system and supplementation of beef cows during late gestation influence heifer progeny.

A 2 × 2 factorial arrangement of treatments was used to evaluate effects of dam winter grazing system and supplementation in the last third of gestation on subsequent BW gain, feed efficiency, and reproduction in heifer progeny. Crossbred cows (yr 1, n = 109; yr 2, n = 114; yr 3, n = 116) grazed range (WR) or corn residue (CR) during winter and within grazing treatment received 0.40 kg/d of 31% CP (DM basis) cubes (PS) or no supplement (NS). Heifer calves (yr 1, n = 56; yr 2, n = 56; yr 3, n = 54) grazed dormant pasture for 114 d postweaning and were individually fed for 87 d before a 45-d natural service breeding. Dam PS reduced (P = 0.04) heifer birth date and CR tended to increase (P = 0.07) heifer birth BW. Both PS and CR increased (P ≤ 0.05) heifer weaning BW; however, adjusted 205-d weaning BW was only lighter (P = 0.03) if the dam grazed WR with NS. Heifers from PS dams tended to be younger (P = 0.09) at puberty than NS, and there was a trend (P = 0.11) for more heifers to be pubertal by breeding if the dam grazed WR with PS compared with other treatment groups. Heifers from WR-NS dams tended to weigh less (P ≤ 0.09) at breeding and at pregnancy diagnosis than WR PS. There was a trend (P = 0.13) for pregnancy rate to be greater for heifers born to PS dams. Individually fed heifer DMI was not affected (P = 0.25) by treatment; however, heifers from dams that grazed CR with PS gained the least BW (P = 0.04) during individual feeding and had the smallest (P = 0.03) G:F. In contrast, there were no differences (P > 0.15) in feed efficiency when expressed as residual feed intake. The first calf birth and weaning BW of the heifer was unaffected (P > 0.15) by dam treatment. Heifers from dams that grazed WR with NS tended to have lighter (P = 0.09) BW before the second breeding season but similar (P = 0.97) pregnancy rates. Cows grazing CR with NS produced the most valuable heifer calf at weaning; however, heifers from cows that grazed WR with NS cost the least to develop per pregnant heifer. Winter grazing system and late gestation supplementation affected heifer progeny BW, feed efficiency, and fertility.

Winter grazing system and supplementation during late gestation influence performance of beef cows and steer progeny.

A 2 x 2 factorial study evaluated effects of cow wintering system and last trimester CP supplementation on performance of beef cows and steer progeny over a 3-yr period. Pregnant composite cows (Red Angus x Simmental) grazed winter range (WR; n = 4/yr) or corn residue (CR; n = 4/yr) during winter and within grazing treatment received 0.45 kg/d (DM) 28% CP cubes (PS; n = 4/yr) or no supplement (NS; n = 4/yr). Offspring steer calves entered the feedlot 14 d postweaning and were slaughtered 222 d later. Precalving BW was greater (P = 0.02) for PS than NS cows grazing WR, whereas precalving BCS was greater (P < 0.001) for cows grazing CR compared with WR. Calf birth BW was greater (P = 0.02) for CR than WR and tended to be greater (P = 0.11) for PS than NS cows. Prebreeding BW and BCS were greater (P 0.32) by PS. Calf weaning BW was less (P = 0.01) for calves from NS cows grazing WR compared with all other treatments. Pregnancy rate was unaffected by treatment (P > 0.39). Steer ADG, 12th-rib fat, yield grade, and LM area (P > 0.10) were similar among all treatments. However, final BW and HCW (P = 0.02) were greater for steers from PS-WR than NS-WR cows. Compared with steers from NS cows, steers from PS cows had greater marbling scores (P = 0.004) and a greater (P = 0.04) proportion graded USDA Choice or greater. Protein supplementation of dams increased the value of calves at weaning (P = 0.03) and of steers at slaughter regardless of winter grazing treatment (P = 0.005). Calf birth and weaning BW were increased by grazing CR during the winter. Calf weaning BW was increased by PS of the dam if the dam grazed WR. Compared with steers from NS cows, steer progeny from PS cows had a greater quality grade with no (P = 0.26) effect on yield grade. These data support a late gestation dam nutrition effect on calf production via fetal programming.

Natural selection drives patterns of lake-stream divergence in stickleback foraging morphology.

To what extent are patterns of biological diversification determined by natural selection? We addressed this question by exploring divergence in foraging morphology of threespine stickleback fish inhabiting lake and stream habitats within eight independent watersheds. We found that lake fish generally displayed more developed gill structures and had more streamlined bodies than did stream fish. Diet analysis revealed that these morphological differences were associated with limnetic vs. benthic foraging modes, and that the extent of morphological divergence within watersheds reflected differences in prey resources utilized by lake and stream fish. We also found that patterns of divergence were unrelated to patterns of phenotypic trait (co)variance within populations (i.e. the 'line of least resistance'). Instead, phenotypic (co)variances were more likely to have been shaped by adaptation to lake vs. stream habitats. Our study thus implicates natural selection as a strong deterministic force driving morphological diversification in lake-stream stickleback. The strength of this inference was obtained by complementing a standard analysis of parallel divergence in means between discrete habitat categories (lake vs. stream) with quantitative estimates of selective forces and information on trait (co)variances.

Effect of prebreeding body weight or progestin exposure before breeding on beef heifer performance through the second breeding season.

Two experiments evaluated prebreeding target BW or progestin exposure for heifers developed lighter than traditional recommendations. Experiment 1 evaluated the effects of the system on heifer performance through subsequent calving and rebreeding over 3 yr. Heifers (229 kg) were assigned randomly to be developed to 55% of mature BW (299 kg) before a 45-d breeding season (intensive, INT; n = 119) or 50% of mature BW (272 kg) before a 60-d breeding season (relaxed, RLX; n = 142). Prebreeding and pregnancy diagnosis BW were greater (P 0.15) between systems. Cost per pregnant 2-yr-old cow was less for the RLX than the INT heifer development system. Of heifers that failed to become pregnant, a greater proportion (P = 0.07) of heifers in the RLX than in the INT system were prepubertal when the breeding season began. Therefore, a second 2-yr experiment evaluated melengestrol acetate (MGA, 0.5 mg/d) as a means of hastening puberty in heifers developed to 50% of mature BW. Heifers were assigned randomly to the control (n = 103) or MGA (n = 81) treatment for 14 d and were placed with bulls 13 d later for 45 d. Prebreeding and pregnancy diagnosis BW were similar (280 and 380 kg, respectively; P > 0.10) for heifers in the control and MGA treatments. The proportion of heifers pubertal before breeding (74%), pregnancy rate (90%), calving date, calf weaning weight, and second breeding season pregnancy rate (92%) were similar (P > 0.10) between treatments. Developing heifers to 50 or 55% of mature BW resulted in similar overall pregnancy rates, and supplementing the diets of heifers developed to 50% of mature BW with MGA before breeding did not improve reproductive performance.

Effects of dam nutrition on growth and reproductive performance of heifer calves.

A 3-yr study was conducted with heifers (n = 170) whose dams were used in a 2 x 2 factorial arrangement of treatments to determine the effects of late gestation (LG) or early lactation (EL) dam nutrition on subsequent heifer growth and reproduction. In LG, cows received 0.45 kg/d of a 42% CP supplement (PS) or no supplement (NS) while grazing dormant Sandhills range. During EL, cows from each late gestational treatment were fed cool-season grass hay or grazed sub-irrigated meadow. Cows were managed as a single herd for the remainder of the year. Birth date and birth weight of heifer calves were not affected (P > 0.10) by dam nutrition. Meadow grazing and PS increased (P = 0.02; P = 0.07) heifer 205-d BW vs. feeding hay and NS, respectively. Weight at prebreeding and pregnancy diagnosis were greater (P < 0.04) for heifers from PS dams but were unaffected by EL nutrition (P > 0.10). There was no effect (P > 0.10) of LG or EL dam nutrition on age at puberty or the percentage of heifers cycling before breeding. There was no difference (P > 0.10) in pregnancy rates due to EL treatment. Pregnancy rates were greater (P = 0.05) for heifers from PS dams, and a greater proportion (P = 0.005) of heifers from PS dams calved in the first 21 d of the heifers' first calving season. Nutrition of the dams did not influence (P < 0.10) heifers' average calving date, calving difficulty, and calf birth weight during the initial calving season. Weight at the beginning of the second breeding season was greater (P = 0.005) for heifers from PS dams but was not affected by maternal nutrition during EL (P > 0.10). Dam nutrition did not affect (P > 0.10) heifer ADG or G:F ratio. Heifers from PS dams had greater DMI (P = 0.09) and residual feed intake (P = 0.07) than heifers from NS cows if their dams were fed hay during EL but not if their dams grazed meadows. Heifers born to PS cows were heavier at weaning, prebreeding, first pregnancy diagnosis, and before their second breeding season. Heifers from cows that grazed meadows during EL were heavier at weaning but not postweaning. Despite similar ages at puberty and similar proportions of heifers cycling before the breeding season, a greater proportion of heifers from PS dams calved in the first 21 d of the heifers' first calving season, and pregnancy rates were greater compared with heifers from NS dams. Collectively, these results provide evidence of a fetal programming effect on heifer postweaning BW and fertility.

Phenotypic plasticity in two marine snails: constraints superseding life history.

In organisms encountering predictable environments, fixed development is expected, whereas in organisms that cannot predict their future environment, phenotypic plasticity would be optimal to increase local adaptation. To test this prediction we experimentally compared phenotypic plasticity in two rocky-shore snail species; Littorina saxatilis releasing miniature snails on the shore, and Littorina littorea releasing drifting larvae settling on various shores, expecting L. littorea to show more phenotypic plasticity than L. saxatilis. We compared magnitude and direction of vectors of phenotypic difference in juvenile shell traits after 3 months exposure to different stimuli simulating sheltered and crab-rich shores, or wave-exposed and crab-free shores. Both species showed similar direction and magnitude of vectors of phenotypic difference with minor differences only between ecotypes of the nondispersing species, indicating that plasticity is an evolving trait in L. saxatilis. The lack of a strong plastic response in L. littorea might be explained by limits rather than costs to plasticity.

Effects of pre- and postpartum nutrition on reproduction in spring calving cows and calf feedlot performance.

Crossbred, spring-calving cows (yr 1, n = 136; yr 2, n = 113; yr 3, n = 113) were used in a 3-yr experiment to evaluate the influence of supplemental protein prepartum and grazing subirrigated meadow postpartum on pregnancy rates and calf feedlot performance. A 2 x 2 factorial arrangement of treatments was used in a switchback design. From December 1 to February 28, cows grazed dormant upland range in 8 pastures (32 +/- 2 ha each). The equivalent of 0.45 kg of supplement/cow per d (42% CP) was provided to half of the cows on a pasture basis 3 d/wk. For 30 d before the beginning of breeding (May 1 to May 31), half of the cows grazed a common subirrigated meadow (58 ha), and the remainder was fed grass hay in a drylot. Cow BW and BCS were monitored throughout the year, and steer calf performance was determined until slaughter. Feeding supplement prepartum improved (P = 0.01 to P < 0.001) BCS precalving (5.1 vs. 4.7) and prebreeding (5.1 vs. 4.9) and increased (P = 0.02) the percentage of live calves at weaning (98.5 vs. 93.6%) but did not affect (P = 0.46) pregnancy rate (93 vs. 90%). Calves born to dams fed supplement prepartum had similar (P = 0.29) birth weight (37 vs. 36 kg) but greater (P = 0.02) weaning weight (218 vs. 211 kg). However, steer feedlot DMI (8.53 vs. 8.48 kg), ADG (1.6 vs. 1.6 kg), and carcass weight (369 vs. 363 kg) were not affected (P = 0.23 to P = 0.89) by prepartum supplementation. Allowing cows to graze subirrigated meadow postpartum improved (P < 0.001) BCS prebreeding (5.2 vs. 4.9) but did not affect (P = 0.88) pregnancy rate (92 vs. 91%). Allowing cows to graze subirrigated meadow increased (P = 0.01) calf weaning weight (218 vs. 211 kg) but not (P = 0.62 to P = 0.91) feedlot DMI (8.4 vs. 8.3 kg), ADG (1.6 vs. 1.6 kg), or carcass weight (363 vs. 362 kg) of their steer calves. Increased percentage of live calves at weaning as a result of feeding supplemental protein increased net returns at weaning and after finishing in the feedlot. Net returns were increased by allowing cows to graze subirrigated meadow postpartum regardless of whether calves were marketed at weaning or after finishing in the feedlot.

Estimation of undegradable intake protein in forages using neutral detergent insoluble nitrogen at a single in situ incubation time point.

Two experiments were conducted to evaluate the use of neutral detergent insoluble nitrogen (NDIN) at a single in situ incubation time point to estimate the undegradable intake protein (UIP) in forages as well as to compare rates of NDIN degradation. Forage samples in Exp. 1 comprised diet samples collected from range and meadow pastures monthly from May through September. In Exp. 2, clipped samples of alfalfa, birdsfoot trefoil, kura clover, and smooth bromegrass, and diet samples of the mixed legume-grass and smooth bromegrass were evaluated. Forage samples were incubated in situ for their mean retention time (MRT) estimated from IVDMD plus a 10-h passage lag to yield the total MRT (TMRT). Samples were also incubated for 0 h, 10 h, 75% TMRT, and 96 h. Undegradable intake protein was measured at 75% TMRT and TMRT, and calculated using fractional rates of degradation and passage with a 10-h passage lag. Rates of ruminal NDIN degradation were calculated using the slope of the regression of the natural logarithm of the potentially degradable NDIN remaining (96-h undegradable fraction subtracted) against time. The estimated UIP values obtained using 75% TMRT were highly correlated with those obtained using fractional rates of degradation and passage plus accounting for a 10-h passage lag in Exp. 1 (R2 = 0.95) and Exp. 2 (R2 = 0.98). Rates of NDIN degradation of range and meadow samples in Exp. 1 were slower (P < 0.05) from 0 to 10 h in May and June compared with rates from 10 h to 75% TMRT, but rates of degradation were not different (P = 0.34 to 0.71) for the rest of the collection periods. Rates of degradation were not different from 0 to 10 h and 10 h to 75% TMRT in Exp. 2 for diet (P = 0.82) or clipped samples (P = 0.86). The UIP of the forages in these experiments was accurately estimated using NDIN at a single in situ incubation time point equivalent to 75% of the TMRT, and rates of protein degradation can be obtained at this time point when 0- and 96-h incubations are included.