Analysis of complications in 97 periprosthetic Vancouver B2 fractures treated either by internal fixation or revision arthroplasty

INTRODUCTION

The treatment of Vancouver B2 periprosthetic fractures after hip arthroplasty is still a matter of debate. Revision Arthroplasty (RA) was long thought to be the treatment of choice, however several recent papers suggested that Open Reduction and Internal Fixation (ORIF) is a viable option for selected B2 fractures. Complication rates of 14-26% have been reported following surgical treatment of B2 fractures. No significant difference between RA and ORIF in the complication rates nor in the functional outcome was observed.

METHOD

We conducted a retrospective analysis of 97 consecutive Vancouver B2 fractures treated according to the algorithm at our institution from 2007 to 2020 and recorded complications and patient specific data.

RESULT

From the 97 patient, 45 fractures were treated with RA while 52 fractures were treated with ORIF. Thirteen patients in the RA group had a complication that needed revision (28%) and 11 patients in the ORIF group needed revision (21%). There was no significant difference between complication rates. The reason for failure in the 13 RA patients were infection (n = 4), stem subsidence (n = 1), refracture after a new fall (n = 3), secondary dislocation of the greater trochanter (n = 1) and dislocation (n = 4). The reason for failure in the 11 ORIF patients that were revised were infection (n = 5), persistent symptomatic stem loosening (n = 3) and refracture (n = 3) after a new fall.

CONCLUSION

ORIF can be used to revise cemented and non-cemented shafts in more than half of Vancouver B2 fractures with no difference in complication rates when compared to RA. A periprosthetic fracture around the hip has a 21-28% risk of a re-operation after revision surgery with infection and re-fracture after a new fall being the most frequent cause of re-operation.

Diet, cellular, and systemic homeostasis control the cycling of potassium stable isotopes in endothermic vertebrates

The naturally occurring stable isotopes of potassium (41K/39K, expressed as δ41K) have the potential to make significant contributions to vertebrate and human biology. The utility of K stable isotopes is, however, conditioned by the understanding of the dietary and biological factors controlling natural variability of δ41K. This paper reports a systematic study of K isotopes in extant terrestrial endothermic vertebrates. δ41K has been measured in 158 samples of tissues, biofluids, and excreta from 40 individuals of four vertebrate species (rat, guinea pig, pig and quail) reared in two controlled feeding experiments. We show that biological processing of K by endothermic vertebrates produces remarkable intra-organism δ41K variations of ca. 1.6‰. Dietary δ41K is the primary control of interindividual variability and δ41K of bodily K is +0.5-0.6‰ higher than diet. Such a trophic isotope effect is expected to propagate throughout trophic chains, opening promising use for reconstructing dietary behaviors in vertebrate ecosystems. In individuals, cellular δ41K is related to the intensity of K cycling and effectors of K homeostasis, including plasma membrane permeability and electrical potential. Renal and intestinal transepithelial transports also control fractionation of K isotopes. Using a box-modeling approach, we establish a first model of K isotope homeostasis. We predict a strong sensitivity of δ41K to variations of intracellular and renal K cycling in normal and pathological contexts. Thus, K isotopes constitute a promising tool for the study of K dyshomeostasis.

A comparison of commercially available feeds for rabbits, guinea pigs, chinchillas and degus with evidence of their diet and feeding behaviour in natural habitats

INTRODUCTION

A large variety of pet feeds is commercially available for pet herbivores; these feeds may differ in nutrient composition from the natural diet, and may trigger different feeding behaviours than observed in natural habitats. Here, we surveyed literature on the natural diet and activity budget of rabbits (Oryctolagus cuniculus), guinea pigs (Cavia porcellus), chinchilla (Chinchilla lanigera) and degus (Octodon degus), as well as 260 compound feeds commercially available for these species between 1982 and 2020. The species are classified as herbivores, with available data on natural diets suggesting a crude fibre (CF) level of approximately 250 g/kg dry matter (DM), natural feeding activity at a magnitude of 4-7 h per day, with distinctively shorter feeding when fed on compound pet feeds. Only for a minority of feeds did the first 5 listed ingredients not include a starchy ingredient, or only ingredients not considered suitable for human consumption. The percentage of feeds whose CF level was less than 150 g/kg DM was 22 % for production rabbits, 18 % for pet rabbits, 26 % for guinea pigs, 18 % for chinchillas and 14 % for degus; in other words, a majority of currently marketed products have CF levels in accord with published recommendations, even if that means a discrepancy to natural diets. Screening the producers' feeding instructions suggests they should generally not be followed uncritically. No temporal trends in the CF levels of these diets was evident. There is no consensus whether only products resembling natural diet items should be included in pet feeds, or whether vegetable byproducts not edible by humans should also be included. The observed practice of pet feed composition largely did not follow either concept, questioning the general rationale of pet feed composition. Whole forage like hay is recommended as the main diet component for these species, and 76 % of pet feed products noted that hay should be fed in the feeding instructions.

Management of acute periprosthetic knee infection: a comparison of arthroscopic and open debridement

INTRODUCTION

In acute periprosthetic knee infections, debridement and implant retention (DAIR) is the preferred treatment prior to one- and two-stage revisions. The aim of this study is to compare the outcomes of arthroscopic and open debridement of infected primary total knee arthroplasties (TKA).

MATERIAL AND METHODS

We analyzed clinical, laboratory, and antibiotic treatment data, collected in patients with periprosthetic knee infection treated with DAIR at a Swiss Level 1 orthopedic and trauma center over a 10-year period between January 2005 and May 2015. Inclusion criteria were primary total knee arthroplasty and early postoperative or acute hematogenous periprosthetic joint infection (PJI). The primary endpoint was the need for further revision surgery due to persistent infection. The secondary endpoint was the prosthesis salvage in further infection surgeries.

RESULTS

Forty-two patients with 44 acute or hematogenous periprosthetic knee infections were included. We recorded 20 recurrent infections (45%) in our study population: 10 (77%) out of 13 in the arthroscopic DAIR group and 10 (32%) out of 31 in the open DAIR group. Two-stage revision, meaning complete removal of the TKA, insertion of a spacer and replantation at a second stage, had to be performed in three patients treated initially arthroscopically (23%) and in six patients treated initially with an open surgical procedure (21%).

CONCLUSIONS

Open debridement for acute periprosthetic knee infection shows clear benefits in terms of infection eradication and prosthesis salvage compared to arthroscopic DAIR.

The mammalian brain under domestication: Discovering patterns after a century of old and new analyses

Comparisons of wild and domestic populations have established brain reduction as one of the most consistent patterns correlated with domestication. Over a century of scholarly work has been devoted to this subject, and yet, new data continue to foster its debate. Current arguments, both for and against the validity of brain reduction occurring in domestic taxa, have repeatedly cited a small set of reviews on this subject. The original works, their sampling, methodological details, and nuances of results that would be key to establishing validity, particularly in light of new data, have not been investigated. To facilitate and encourage a more informed discussion, we present a comprehensive review of original brain reduction literature for four mammalian clades: Artiodactyla, Perissodactyla, Carnivora, and Glires. Among these are studies that generated the most cited brain reduction values in modern domestication literature. In doing so, we provide a fairer stage for the critique of traits associated with domestication. We conclude that while brain reduction magnitudes may contain error, empirical data collectively support the reduction in brain size and cranial capacity for domestic forms.

Particle size distribution in commercial pig compound feeds in Switzerland: survey and methodological considerations

INTRODUCTION

The grinding intensity of pig feed is considered one potential predisposing factor for gastric ulcers, and a variety of particle size recommendations have been published for pig feeds. We subjected 51 different commercial compound feeds for pigs (38 meals, 13 pellets/granulates) to dry and/or wet sieve analysis. The amount of particles passing the finest sieve (or being soluble) was estimated by the difference to the total dry matter weighed prior to sieving. Mean particle size was calculated based on the weighted average of the material retained on the sieves (MPSsieves), and additionally with accounting for this lost material (MPStotal). Dry sieve analysis of the meals yielded MPSsieves of 0,58-2,90 mm and MPStotal of 0,58-2,89 mm; only 0,02 to 2,71 % of the dry matter passed all sieves. Wet sieve analysis of all meals and pellets yielded similar MPSsieves of 0,63-1,66 mm, but dramatically lower MPStotal of 0,26-1,04 mm; between 35 and 66 % of the dry matter was not retained on the sieves. Pellets had smaller MPS, and a higher proportion of particles passing all sieves than meals. Depending on the reference used, a maximum of 26 % of meals conformed to recommendations for pig feed particle size. None of the pelleted feeds met these criteria, irrespective of the source consulted for the recommendation. Wet sieving should be considered the standard analysis, because in dry sieving, very fine particles adhering to larger particles may not be registered separately but contribute erroneously to larger particle weight. In addition, the MPS calculation should account for material lost through the finest sieve. Reasons why Swiss pig feed does not meet particle size recommendations should be further investigated.

Evaluation of the prevalence of stomach ulcers in slaughtered pigs in a Swiss -abattoir

INTRODUCTION

The development of gastric ulcers in pigs has various reasons. In Switzerland, the last survey on the prevalence of gastric ulcers and possible risk factors was performed in 2005. We aimed to reassess gastric ulcers prevalence today, in 2021. A total of 1005 stomachs from fattening pigs from 136 batches and around 87 herds were evaluated at a Swiss abattoir. The Pars oesophagea of the stomach was scored from 0=healthy to 10=severe ulceration and strictures. Scores were compared between pigs produced under the labels «Integrierte Produktion Schweiz» (IPS, n=242 stomachs, 18 farms) and «Qualitätsmanagement-Schweizerfleisch» (QM, n=649, 58 farms) and others (n=114). The results showed a prevalence of 27,2 % mild mucosal changes (Scores 1-3), 14,9 % moderate mucosal changes (Scores 4-6) and 19,1 % severe mucosal changes (Scores 7-10). Only 38,8 % of the stomachs were rated 0 and thus considered healthy. Compared to the results from 2005, there is no difference concerning the lowest scores (0-2) and the highest scores (9-10). However, there was a shift from the medium scores (3-4) to higher scores (5-8). Stomach scores turned out to be herd specific. There were differences (p < 0,01) between labels, indicating that IPS pigs had less affected stomachs. Stomachs that were empty at slaughter showed higher scores (p < 0,001). The mean carcass weight of the pigs in the slaughter groups was negatively correlated (p < 0,05) to their median stomach score. Confiscations were not related to stomach scores. The results suggest that pig stomach health has not improved since 2005. The differences between labels seem to have resulted from different regulations prescribing a minimum particle size of enrichment material in IPS. The reasons for gastric ulcer development, including those on the individual herd within label, still have to be further clarified in order to allow targeted countermeasures. Given apparent farm-specificity, scoring of a limited number of stomachs per herd during the slaughter process could facilitate the establishment of a feedback scheme.

Intensive human contact correlates with smaller brains: differential brain size reduction in cattle types

Cattle are one of the most intensively bred domestic animals, providing humans with a multitude of products and uses. Using data from the fossil record, we test if their domestication, as for other taxa, has resulted in a reduction of their brain size. We not only conclude that Bos taurus (domestic cattle) have smaller brains than their wild ancestor, Bos primigenius (aurochs), but that brain size varies significantly by breed, with some having much smaller brains than others. Differences in husbandry practices between several breed categories align with a range of human engagement, which also aligns with the degree of selection for docility. Sampling 317 domestics from 71 breeds, we investigate if differences in brain size correlate with the intensity of human contact. A clear pattern emerges whereby a brain reduction gradient parallels a gradient in behavioural selection. Bullfighting cattle, which are bred for fighting and aggressive temperament, have much larger brains than dairy breeds, which are intensively selected for docility. Our results add to a fundamental aspect of animal domestication theory: the interplay between basic features of the domestic environment-selection for docility, absence of predators and human provision of resources-seems to explain differences in brain size.

Theory of medical scoring systems and a practical method to evaluate Asian elephant (Elephas maximus) foot health in European zoos

Several established models in human and veterinary medicine exist to evaluate an individual health or disease status. Many of these seem unsuitable for further epidemiological research aimed at discovering underlying influential factors. As a case example for score development and choice, the present study analyses different approaches to scoring the foot health of Asian elephants (Elephas maximus) living in European facilities. Sum scores with varying degree of detail, and without or with a weighting method, were compared using descriptive statistics, ie kurtosis, skewness, Shannon entropy, total redundancy, their maximum and their actual ranges. With increasing score complexity, a higher level of differentiation was reached. In parallel, the distribution of score frequencies in the population shifted systematically: with the least complex scoring model the pattern indicated a severely unhealthy population with an opposite skew to a hypothetically healthy population, whereas the most complex scoring model indicated a mildly affected population with a skew corresponding to that expected for a healthy population. We propose the latter, in the form of the Particularised Severity Score (ParSev), which accounts for every nail and pad individually and weights the sub-scores by squaring, as the most relevant score for further investigations, either in assessing changes within an elephant population over time, or correlating foot health in epidemiological studies to potentially influencing factors. Our results emphasise the relevance of choosing appropriate scoring models for welfare-associated evaluations, due to implications for the applicability as well as the perceived welfare status of the test population.

Accuracy of methane emissions predicted from milk mid-infrared spectra and measured by laser methane detectors in Brown Swiss dairy cows

Since heritability of CH₄ emissions in ruminants was demonstrated, various attempts to generate large individual animal CH₄ data sets have been initiated. Predicting individual CH₄ emissions based on equations using milk mid-infrared (MIR) spectra is currently considered promising as a low-cost proxy. However, the CH₄ emission predicted by MIR in individuals still has to be confirmed by measurements. In addition, it remains unclear how low CH₄ emitting cows differ in intake, digestion, and efficiency from high CH₄ emitters. In the current study, putatively low and putatively high CH₄ emitting Brown Swiss cows were selected from the entire Swiss herdbook population (176,611 cows), using an MIR-based prediction equation. Eventually, 15 low and 15 high CH₄ emitters from 29 different farms were chosen for a respiration chamber (RC) experiment in which all cows were fed the same forage-based diet. Several traits related to intake, digestion, and efficiency were quantified over 8 d, and CH₄ emission was measured in 4 open circuit RC. Daily CH₄ emissions were also estimated using data from 2 laser CH₄ detectors (LMD). The MIR-predicted CH₄ production (g/d) was quite constant in low and high emission categories, in individuals across sites (home farm, experimental station), and within equations (first available and refined versions). The variation of the MIR-predicted values was substantially lower using the refined equation. However, the predicted low and high emitting cows (n = 28) did not differ on average in daily CH₄ emissions measured either with RC or estimated using LMD, and no correlation was found between CH₄ predictions (MIR) and CH₄ emissions measured in RC. When individuals were recategorized based on CH₄ yield measured in RC, differences between categories of 10 low and 10 high CH₄ emitters were about 20%. Low CH₄ emitting cows had a higher feed intake, milk yield, and residual feed intake, but they differed only weakly in eating pattern and digesta mean retention times. Low CH₄ emitters were characterized by lower acetate and higher propionate proportions of total ruminal volatile fatty acids. We concluded that the current MIR-based CH₄ predictions are not accurate enough to be implemented in breeding programs for cows fed forage-based diets. In addition, low CH₄ emitting cows have to be characterized in more detail using mechanistic studies to clarify in more detail the properties that explain the functional differences found in comparison with other cows.

Microanatomy of the digestive tract, hooves and some visceral organs of addax antelope (Addax nasomaculatus) following a concentrate or forage feeding regime

Subacute ruminal acidosis is a common disease in captive non-domesticated ruminants and is mainly diagnosed by rumen fluid pH and rumen histology. Furthermore, differences in ruminant gastrointestinal histology have been hypothesized to correlate with the browser-grazer continuum. Twelve surplus addax antelope (Addax nasomaculatus) were divided into two groups, fed either their usual diet, consisting of a concentrate feed with a limited amount of hay, or a diet of unlimited hay only, for 3 months. After culling, descriptive and morphometric histology and pH measurements were compared between groups. Significant variations in cellular subpopulations were noted between groups, with roughage-fed individuals presenting primarily with balloon cells of the Stratum corneum and living layer cell vacuolization, whereas parakeratosis and intermediate-type cells were more frequent in the concentrate-fed group. Lesions typical of subacute ruminal acidosis were significantly more pronounced in concentrate-fed individuals. Ruminal pH measurements did not differ significantly, but were more consistent in forage-fed individuals, indicating a more stable reticuloruminal environment. The results indicate that ruminal histology may be more appropriate in assessing ruminal health compared to a single post-mortem pH measurement. It is proposed that Stratum corneum balloon cells may indicate cell maturation and not, as previously assumed, hyperfunction. Concentrate-fed individuals scored higher on the presence of inflammatory cells on hoof corium histology. The study further emphasizes the adaptability of ruminant digestive tract microanatomy in adult animals even after a short period of time and the positive effects an increased roughage diet may have in populations of captive grazing ruminants.

Vergleichende Untersuchung zur Krankheits-verteilung bei Kaninchen, Meerschweinchen, Ratten und Frettchen

Gegenstand und Ziel: Auswertung der Krankengeschichten der kleinen Heimtiere, die zwischen 1994 und 2003 in der Klinik für Zoo-, Heimund Wildtiere, Vetsuisse-Fakultät, Universität Zürich vorgestellt wurden. Ziel war es, retrospektiv die Entwicklung der Fallzahlen im Patientengut zu analysieren und die häufigsten Krankheitsbilder der häufigsten Arten zu ermitteln. Material und Methoden: Aus den Patienten-kar teien wurde eine Datenbank erstellt und aus dieser die häufigsten Tierarten der Klasse der Säuger und die Prävalenz der Diagnosen und Vorstellungsgründe ermittelt. Es erfolgte eine Gegenüberstellung der Daten zu Resultaten vergleichbarer Studien aus Deutschland. Ergeb-nisse: Im ausgewerteten Zeitraum fanden 11833 Patientenvorstellungen (Säuger, Vögel und Reptilien) statt. Die Säuger stellten die Klasse mit der größten Anzahl von Tieren (n = 5793) dar. Vertieft beurteilt wurden bei den Säugern die Tierarten Kaninchen (n = 2125), Meerschweinchen (n = 2009), Ratte (n = 651) und Frettchen (n = 162). Die Tierarten Kaninchen und Frettchen nahmen im Untersuchungszeitraum signifi-kant zur Gesamtklassenzahl zu. Als häufigste Diagnose wurden bei Kaninchen und Meerschweinchen Zahnerkrankungen ermittelt, bei Ratten und Frettchen Neoplasien. Ein insgesamt häufiger Vorstellungsgrund war die Kastration. Schlussfolgerungen und klinische Relevanz: Die Ergebnisse weisen tierartliche Unterschiede bei den Krankheiten nach. Beim Frettchen zeigen sie den Zusammenhang zwischen Kastrationsalter und Manifestation des Hyperadrenokortizismus auf. Zudem verdeutlicht die Arbeit, dass bei den Heimtieren mangels entsprechender Untersuchungsmöglichkeiten oftmals nur eine Verdachts-diagnose gestellt wird.

A comparative meta-analysis on the relationship of faecal calcium and phosphorus excretion in mammals

To investigate the relationship between faecal calcium (Ca) and phosphorus (P) excretion in different mammalian species, a meta-analysis on digestibility data derived from the literature was conducted. Seventy-three studies on carnivores, omnivores, large and small hindgut fermenters, ruminants and hippos (a total of 21 mammalian species, precondition for inclusion dietary Ca/P ratio 1.5/1 - 3.0/1) were analysed for Ca and P digestibility. Dietary Ca/P ratios were lower than faecal Ca/P ratios in carnivores, omnivores, ruminants and hippos. In hindgut fermenters, dietary Ca/P ratios were higher than faecal Ca/P ratios, indicating higher intestinal Ca absorption in these species. In all species investigated, there was a significant positive relationship between Ca intake and faecal Ca excretion and between P intake and faecal P excretion. In the biologically relevant range, these equations predicted lower faecal Ca losses in hindgut fermenters than ruminants, for faecal P vice versa. In all species, faecal Ca and P excretion correlated significantly. In carnivores, this highly linear correlation was exceptionally strong (R² = .92). Yet, the linearity of the correlation was questionable in omnivores and ruminants. Possibly, the strong linear correlation of faecal Ca and P excretion in carnivores is due to the formation of insoluble Ca/P complexes in their relatively short and simple gastrointestinal tract. Another hypothesis is that in carnivores, Ca homeostasis relies on modifying bone turnover to a higher degree than on changes in intestinal Ca absorption. For the formation of bone matrix, a constant ratio of Ca and P absorption is of advantage.

Comparative selective retention of particle size classes in the gastrointestinal tract of ponies and goats

There is a discrepancy in the literature on potential digesta separation mechanisms in horses, with both a selective retention of fine and of large particles postulated in different publications. To assess the net effect of such mechanisms, we fed ponies on a hay-only diet a pulse dose of whole (unchopped) marked hay together with a solute marker, collected faeces on a regular basis, measured marker concentrations in whole faeces and in their large (2.0-16 mm), medium (0.5-1.0 mm) and small (0.063-0.25 mm) particle fraction, and calculated the corresponding mean retention times (MRTs). For comparison, the same experiment was performed in goats. In goats, as expected, MRT_solute (35 hr) was significantly shorter than MRT_particle (51 hr); only a very small fraction of particle marker was excreted as large particles (2%); and the MRT of these large particles was significantly shorter than that of small particles (with a relevant difference of 8.6 hr), indicating that those few large particles that escape the rumen do so mostly soon after ingestion. In ponies, MRT_solute (24 hr) did not differ from MRT_particle (24 hr); a higher fraction of particle marker was excreted as large particles (5%); and the MRT of these large particles was longer than that of small particles (but with a non-relevant difference of less than 1 hr). These results indicate that no relevant net separation of digesta phases occurs in horses and that selective particle retention mechanisms in the large intestine are unlikely to represent important characteristics of the horse's digestive physiology.

Debridement and implant retention in the management of hip periprosthetic joint infection: outcomes following guided and rapid treatment at a single centre

AIMS

To analyse the effectiveness of debridement and implant retention (DAIR) in patients with hip periprosthetic joint infection (PJI) and the relationship to patient characteristics. The outcome was evaluated in hips with confirmed PJI and a follow-up of not less than two years.

PATIENTS AND METHODS

Patients in whom DAIR was performed were identified from our hip arthroplasty register (between 2004 and 2013). Adherence to criteria for DAIR was assessed according to a previously published algorithm.

RESULTS

DAIR was performed as part of a curative procedure in 46 hips in 42 patients. The mean age was 73.2 years (44.6 to 87.7), including 20 women and 22 men. In 34 hips in 32 patients (73.9%), PJI was confirmed. In 12 hips, the criteria for PJI were not fulfilled and antibiotics stopped. In 41 (89.1%) of all hips and in 32 (94.1%) of the confirmed PJIs, all criteria for DAIR were fulfilled. In patients with exogenous PJI, DAIR was performed not more than three days after referral. In haematogenous infections, the duration of symptoms did not exceed 21 days. In 28 hips, a single debridement and in six hips two surgical debridements were required. In 28 (87.5%) of 32 patients, the total treatment duration was three months. Failure was noted in three hips (9%). Long-term follow-up results (mean 4.0 years, 1.4 to 10) were available in 30 of 34 (88.2%) confirmed PJIs. The overall successful outcome rate was 91% in 34 hips, and 90% in 30 hips with long-term follow-up results.

CONCLUSION

Prompt surgical treatment with DAIR, following strict diagnostic and therapeutic criteria, in patients with suspected periprosthetic joint infection, can lead to high rates of success in eradicating the infection. Cite this article: Bone Joint J 2017;99-B:330-6.

[Veterinary care of birds of prey: Development from 1985 to 2015]

INTRODUCTION

A retrospective study was conducted which analysed the patient histories of free-living birds of prey presented to the Clinic of Zoo Animals, Exotic Pets and Wildlife of the University of Zürich from 2009 to 2015. The data were compared with a previous study on the period from 1985 to 1994. The average number of cases presented per year increased from 55 to 109. Most cases are presented in the months of February, June and July. Surgical problems were most frequently diagnosed and occurred in 61.5% of the cases, with 66.5% of patients presenting with one or more fractures. Regarding medical cases (29.5%) the most frequent finding was unspecified weakness (47.8%). Ophthalmic pathologies were diagnosed in 9% of the patients. With respect to outcome 41.7% of the patients could be released, 47.3% and 11.0% had to be euthanized or died, respectively. In 6 of 9 of the most frequently presented species the rate of release increased significantly compared to the previous study.

Biological implications of longevity in dairy cows: 1. Changes in feed intake, feeding behavior, and digestion with age

Milk production strategies focusing on longevity and limited use of concentrate are receiving increasing attention. To evaluate such strategies, knowledge of the development with age of animal characteristics, particularly digestion, is indispensable. We therefore investigated the development of feed intake, chewing activity, and digestion in 30 lactating Brown Swiss cows (876-3,648 d old) and 12 heifers (199-778 d old). We also studied whether age effects were exhibited differently in animals selected from herds subjected for 11 yr either to a forage-only or to a forage-concentrate feeding regimen. Forages consisted of grass hay (the only feed for heifers), corn silage, and grass pellets. Measurements lasted for 8 d, where amounts and composition of feeds, feces, and milk were recorded and analyzed. Ruminal pH data and eating and rumination activity were assessed by pH sensors put into the rumen and halter-mounted noseband sensors. The mean retention time of feed particles was assessed using Cr-mordanted fiber and data were used to calculate dry matter gut fill. Data were subjected to regression analyses with age and feeding regimen as explanatory variables, and body weight, milk yield, and proportion of hay in forage as covariates. This allowed separating age-related changes of body weight and milk yield from independent age effects and correcting for differences in preference for individual forages. In cows, organic matter intake increased with age (from slightly below to above 20kg/d), as did mean retention time and gut fill. Digestibility of organic matter did not show a clear age dependency, but fiber digestibility had a maximum in cows of around 4 to 6 yr of age. Ruminal pH and absolute eating and rumination times did not vary with cow age. Young and old cows chewed regurgitated boluses more intensively (60-70 times) than middle-aged cows (about 50 times). Effects of feeding regimen were small, except for fiber intake and rumination time per unit of intake, owing to the different fiber content of the diets. No significant interactions between age and feeding regimen were found. Heifers spent more time eating and ruminating per unit of feed than cows, which resulted in a high fiber digestibility. Irrespective of the feeding regimen tested, older cows maintained intake and digestion efficiency with longer retention times and chewing rumination boluses more intensively. The results support efforts to extend the length of productive life in dairy cows.

Comparative analyses of tooth wear in free-ranging and captive wild equids

REASONS FOR PERFORMING STUDY

Captive breeding has played a crucial role in the conservation of threatened equid species. Grazing ruminants and rhinoceros in captivity have less abrasion-dominated tooth wear than their free-ranging conspecifics, with potential negative consequences for their health. However, a similar study on wild equids in captivity is missing.

OBJECTIVES

The aim was to establish if different tooth wear patterns are exhibited by free-ranging and captive equids.

STUDY DESIGN

Cross-sectional study of museum specimens comparing free-ranging and captive equids.

METHODS

Dental casts of maxillary cheek teeth of 228 museum specimens (122 from free-ranging and 106 from captive individuals) of 7 wild equid species were analysed using the extended mesowear method. Although teeth showing specific abnormalities were not scored, the presence of focal overgrowths (hooks) of the rostral premolars (106, 206) was recorded.

RESULTS

Captive Equus ferus przewalskii, E. grevyi, E. hemionus, E. quagga boehmi and E. zebra hartmannae have less abrasion-dominated tooth wear on their premolars than their free-ranging conspecifics (P<0.001). Fewer differences were exhibited between populations in the molars. No differences were exhibited in the distal cusp of the molars (110, 210) between populations, except in a small sample of E. kiang. Captive equids exhibited more homogeneous wear along the tooth row whereas free-ranging equids exhibited a tooth wear gradient, with more abrasion on premolars than molars. There were more rostral hooks on the premolars (106, 206) in the captive than the free-ranging population (P = 0.02).

CONCLUSIONS

Captive equids did experience less abrasion-dominated tooth wear than their free-ranging conspecifics, but the differences in tooth wear were less pronounced than those between captive and free-ranging wild ruminant and rhinoceros species. This indicates that feeding regimes for captive equids deviate less from natural diets than those for captive ruminants and rhinoceros but that factors leading to hook formation, in particular feeding height, should receive special attention. The Summary is available in Chinese - see Supporting information.

HIV Tat protein affects circadian rhythmicity by interfering with the circadian system

OBJECTIVES

Sleep disorders are common in patients with HIV/AIDS, and can lead to poor quality of life. Although many studies have investigated the aetiology of these disorders, it is still unclear whether impaired sleep quality is associated with HIV itself, social problems, or side effects of antiretroviral therapy (ART). Moreover, despite its known neurological associations, little is known about the role of the trans-activator of transcription (Tat) protein in sleep disorders in patients with HIV/AIDS. The purpose of this study was to test the hypothesis that the sleep quality of patients with HIV/AIDS affected by an altered circadian rhythm correlates with cerebrospinal HIV Tat protein concentration.

METHODS

Ninety-six patients with HIV/AIDS between 20 and 69 years old completed the Pittsburgh Sleep Quality Index. Their circadian rhythm parameters of blood pressure, Tat concentration in cerebrospinal fluid, melatonin concentration, CD4 cell count and HIV RNA viral load in serum were measured.

RESULTS

The circadian amplitude of systolic blood pressure and the score for sleep quality (Pittsburgh Sleep Quality Index) were negatively correlated with HIV Tat protein concentration, while the melatonin value was positively correlated with Tat protein concentration.

CONCLUSIONS

The HIV Tat protein affects circadian rhythmicity by interfering with the circadian system in patients with HIV/AIDS and further increases the melatonin excretion value. A Tat protein-related high melatonin value may counteract HIV-related poor sleep quality during the progression of HIV infection. This study provides the first clinical evidence offering an explanation for why sleep quality did not show an association with progression of HIV infection in previous studies.

Influence of physico-chemical material characteristics on staphylococcal biofilm formation--a qualitative and quantitative in vitro analysis of five different calcium phosphate bone grafts

Various compositions of synthetic calcium phosphates (CaP) have been proposed and their use has considerably increased over the past decades. Besides differences in physico-chemical properties, resorption and osseointegration, artificial CaP bone graft might differ in their resistance against biofilm formation. We investigated standardised cylinders of 5 different CaP bone grafts (cyclOS, chronOS (both β-TCP (tricalcium phosphate)), dicalcium phosphate (DCP), calcium-deficient hydroxyapatite (CDHA) and α-TCP). Various physico-chemical characterisations e.g., geometrical density, porosity, and specific surface area were investigated. Biofilm formation was carried out in tryptic soy broth (TSB) and human serum (SE) using Staphylococcus aureus (ATCC 29213) and S. epidermidis RP62A (ATCC 35984). The amount of biofilm was analysed by an established protocol using sonication and microcalorimetry. Physico-chemical characterisation showed marked differences concerning macro- and micropore size, specific surface area and porosity accessible to bacteria between the 5 scaffolds. Biofilm formation was found on all scaffolds and was comparable for α-TCP, chronOS, CDHA and DCP at corresponding time points when the scaffolds were incubated with the same germ and/or growth media, but much lower for cyclOS. This is peculiar because cyclOS had an intermediate porosity, mean pore size, specific surface area, and porosity accessible to bacteria. Our results suggest that biofilm formation is not influenced by a single physico-chemical parameter alone but is a multi-step process influenced by several factors in parallel. Transfer from in vitro data to clinical situations is difficult; thus, advocating the use of cyclOS scaffolds over the four other CaP bone grafts in clinical situations with a high risk of infection cannot be clearly supported based on our data.

Tooth length and incisal wear and growth in guinea pigs (Cavia porcellus) fed diets of different abrasiveness

Dental diseases are among the most important reasons for presenting guinea pigs (Cavia porcellus) and other rodents to veterinary clinics, but the aetiopathology of this disease complex is unclear. Clinicians tend to believe that the ever-growing teeth of rabbits and rodents have a constant growth that needs to be worn down by the mastication of an appropriate diet. In this study, we tested the effect of four different pelleted diets of increasing abrasiveness [due to both internal (phytoliths) and external abrasives (sand)] or whole grass hay fed for 2 weeks each in random order to 16 guinea pigs on incisor growth and wear, and tooth length of incisors and cheek teeth. There was a positive correlation between wear and growth of incisors. Tooth lengths depended both on internal and external abrasives, but only upper incisors were additionally affected by the feeding of whole hay. Diet effects were most prominent in anterior cheek teeth, in particular M1 and m1. Cheek tooth angle did not become shallower with decreasing diet abrasiveness, suggesting that a lack of dietary abrasiveness does not cause the typical 'bridge formation' of anterior cheek teeth frequently observed in guinea pigs. The findings suggest that other factors than diet abrasiveness, such as mineral imbalances and in particular hereditary malocclusion, are more likely causes for dental problems observed in this species.

Biofilm formation by staphylococci on fresh, fresh-frozen and processed human and bovine bone grafts

Biofilm formation is a multi-step process influenced by surface properties. We investigated early and mature biofilm of Staphylococcus aureus on 4 different biological calcium phosphate (CaP) bone grafts used for filling bone defects. We investigated standardised cylinders of fresh and fresh-frozen human bone grafts were harvested from femoral heads; processed humanand bovine bone grafts were obtained preformed. Biofilm formation was done in tryptic soy broth (TSB) using S. aureus (ATCC 29213) with static conditions. Biofilm density after 3 h (early biofilm) and 24 h (mature biofilm) was investigated by sonication and microcalorimetry. After 3 h, bacterial density was highest on fresh-frozenandfresh bone grafts. After 24 h, biofilm density was lowest on freshbone grafts (p < 0.001) compared to the other 3 materials, which did not differ quantitatively (p > 0.05). The lowest increase in bacterial density was detected on fresh bone grafts (p < 0.001). Despite normal shaped colonies, we found additional small colonies on the surface of the fresh and fresh-frozen samples by sonication. This was also apparent in microcalorimetric heat-flow curves. The four investigated CaP bone grafts showed minor structural differences in architecture but marked differences concerning serum coverage and the content of bone marrow, fibrous tissue and bone cells. These variations resulted in a decreased biofilm density on freshand fresh-frozenbone grafts after 24 h, despite an increased early biofilm formation and might also be responsible for the variations in colony morphology (small colonies). Detection of small colony variants by microcalorimetry might be a new approach to improve the understanding of biofilm formation.