BackgroundTo conduct a hematological analysis of avian blood samples, standard automated cell counting is unreliable because all avian blood cells are nucleated. Therefore, quantitative white blood cell counting in birds is still performed manually, whereby the Natt-Herrick method is widely used in veterinary laboratories. The aim of this study was to evaluate a new commercially available single test system for avian white blood cell counting, the Natt-Herricks-Tic®, which would allow easy in-house analysis by clinicians or technicians. A total of 40 avian ethylenediaminetetraacetic acid (EDTA) blood samples from 24 different species were included in the study. To assess method agreement, each blood sample was analyzed for total white blood cell count with the test method and the Natt-Herrick reference method. To determine the imprecision of the reference method and the Natt-Herricks-Tic® method, the noncorrected white blood cell count was determined ten consecutive times from one avian EDTA blood sample for each method.ResultsThe Natt-Herricks-Tic® method performed well concerning staining quality and countability of the granulocytes by the hemocytometer. In the agreement study, the Natt-Herricks-Tic® method showed a small proportional systematic error with a small positive mean bias of 282 white blood cells/μL but had wide 95% limits of agreement (− 4683 cells/μL to 5227 cells/μL), indicating random error. The precision study resulted in a coefficient of variation of 16% for the Natt-Herricks-Tic® method (the mean ± standard deviation: 9.7 ×  103/μL ± 1.5 × 103/μL) and 23% (the mean ± standard deviation: 7.9 × 103/μL ± 1.8 × 103/μL) for the reference method.ConclusionsThe Natt-Herricks-Tic® method showed acceptable precision for a manual method and demonstrated good agreement with the reference method. It can be recommended as a reliable and suitable method for determining white blood cell counts in avian EDTA blood if nonstatistical quality control measures are used in the daily routine. The application of individual reference intervals for the interpretation of white blood cell counts in birds may improve the diagnostic performance of this important analyte in a clinical setting.

While seasonality has often been investigated with respect to reproduction, seasonality of mortality has received less attention. We investigated whether a seasonal signal of mortality exists in wild ruminants kept in zoos, using data from 60,591 individuals of 88 species. We quantified the mortality in the 3 consecutive months with the highest above-baseline mortality (3 MM). 3 MM was not related to relative life expectancy of species, indicating that seasonal mortality does not necessarily impact husbandry success. Although 3 MM was mainly observed in autumn/winter months, there was no evidence for an expected negative relationship with the latitude of the species' natural habitat and no positive relationship between 3 MM and the mean temperature in that habitat, indicating no evidence for species from lower latitudes/warmer climates being more susceptible to seasonal mortality under zoo conditions. 3 MM was related to reproductive biology, with seasonally reproducing species also displaying more seasonal mortality. This pattern differed between groups: In cervids, the onset of seasonal mortality appeared linked to the onset of rut in both sexes. This was less evident in bovids, where in a number of species (especially caprids), the onset of female seasonal mortality was linked to the lambing period. While showing that the origin of a species from warmer climate zones does not constrain husbandry success in ruminants in terms of an increased seasonal mortality, the results suggest that husbandry measures aimed at protecting females from rutting males are important, especially in cervids. Zoo Biol. 36:74-86, 2017. © 2016 Wiley Periodicals, Inc.

Gestation periods in mammals are generally in line with scaling laws. There are several exceptions in which species of relatively similar size and degree of neonatal maturation show a significant difference in gestation length. For example the giraffids have a very long gestation period, compared to bovids of similar size. By using published data about the placental surface area at term, we show that in ungulates this surface area is more tightly correlated to the average fetal growth rate than to fetal and placenta weight. These data suggest that, within one type of placenta, gestation length and placental surface area are associated parameters. Relationship between placental surface area and fetal growth rate in artiodactyls and perissodactyls DOI 10.1515/mammalia-2016-0032 Received March 9, 2016 accepted June 7, 2016 Abstract: Gestation periods in mammals are generally in line with scaling laws. There are several exceptions in which species of relatively similar size and degree of neonatal maturation show a significant difference in gestation length. For example the giraffids have a very long gestation period, compared to bovids of similar size. By using published data about the placental surface area at term, we show that in ungulates this surface area is more tightly correlated to the average fetal growth rate than to fetal and placenta weight. These data suggest that, within one type of placenta, gestation length and placental surface area are associated parameters.