Postpartum follicular and luteal activity in Holstein-Friesian cows genetically selected for high or low mature bodyweight: Relationships with follicle stimulating hormone,insulin, insulin-like growth factor-1 and growth hormone

AIM: To investigate ovarian follicular and luteal activity during the postpartum period of cows genetically selected for high or low mature bodyweight, in relation to metabolic and reproductive endocrine parameters, to determine whether there are differences between strains that could affect fertility outcomes.

METHODS: The presence of follicles ≥5 mm diameter and luteal structures was mapped in the ovaries of 12 high (heavystrain) and 12 low (light-strain) mature bodyweight cows by daily trans-rectal ultrasonography from Day 7 postpartum until the end of their first normal oestrous cycle. Blood samples were collected daily, for measurement of concentrations of follicle stimulating hormone (FSH), progesterone, growth hormone (GH), insulin-like growth factor-1 (IGF-1), and insulin. Intervals to first ovulation were calculated from ultrasonography data.

RESULTS: Heavy-strain cows had shorter intervals than light-strain cows from calving to the emergence of the first (9.0 (SE 0.9) vs 12.4 (SE 1.3) days) and second (16.4 (SE 1.8) vs 20.6 (SE 1.6) days) dominant follicles (p<0.05). Concentrations of FSH in heavy-strain cows prior to the emergence of the second, third and fourth dominant follicles were higher than in light-strain cows (p<0.05). Heavy-strain cows were more likely to have a large (>15 mm diameter) follicle earlier than light-strain cows (p<0.01). Concentrations of insulin and IGF-1, but not those of GH, were higher in heavy- than light-strain cows during the postpartum period (p=0.01 and p=0.02, respectively), and concentrations of both on Day 6 were inversely related to the time of emergence of the first dominant follicle (p>0.01).

Concentrations of progesterone were similar in both strains of cow until Day 10 of the first oestrous cycle, but thereafter were higher in light- than heavy-strain cows until Day 16. Progesterone concentrations in heavy-strain cows declined earlier and more rapidly than in their lighter counterparts.

CONCLUSION: These results indicate that there is a rapid postpartum resumption of follicular activity in both heavy-and light-strain cows, but that there is an earlier emergence of dominant follicles and ovulation in the former. Differences in luteal function, in terms of lower dioestrus progesterone concentrations and an earlier onset of luteolysis, in heavy- than light-strain cows might be sufficient to impair the fertility of the former.     

Musculoskeletal responses of 2-year-old Thoroughbred horses to early training. 6. Bone parameters in the third metacarpal and third metatarsal bones

AIM: To determine the effect of a known training regimen on the size and mineral content of the third metacarpal (Mc3) and third metatarsal (Mt3) bones of 2-year-old Thoroughbred horses trained on racetracks.

METHODS: Mc3 and Mt3 of seven horses trained on grass and sand tracks were scanned at several sites using conventional quantitative and peripheral computed tomography (CT). Bone dimensions and density in the diaphysis and epiphysis were compared with those from seven untrained horses. Calcein label was injected in two clusters, during Weeks 9 and 12. The extent and rate of diaphyseal modelling was determined by confocal fl uorescent microscopic examination of thin plane parallel sections of the mid-metacarpal region.

RESULTS: Volumetric bone mineral density (BMDv) of the epiphysis was markedly higher and of the diaphysis was slightly higher in trained compared with untrained horses, but greater bone size in the trained horses had the greatest effect on an index of bone strength. Active osteons, defined as Haversian systems containing calcein label, were fewer, of smaller diameter at the time of calcein injection, and had a greater bone apposition rate in trained than in untrained horses.

CONCLUSIONS: Conventional training of 2-year-old Thoroughbred racehorses over a 13-week period had a significant effect on bone size, density and strength index when compared to untrained horses.

CLINICAL RELEVANCE: Bone responded rapidly to early training. The data provide reference values and sites for use in longitudinal studies of commercial training regimens.     

Magnetic Field and Plasma Observations at Mars: Initial Results of the Mars Global Surveyor Mission

The magnetometer and electron reflectometer investigation (MAG/ER) on the Mars Global Surveyor spacecraft has obtained magnetic field and plasma observations throughout the near-Mars environment, from beyond the influence of Mars to just above the surface (at an altitude of approximately 100 kilometers). The solar wind interaction with Mars is in many ways similar to that at Venus and at an active comet, that is, primarily an ionospheric-atmospheric interaction. No significant planetary magnetic field of global scale has been detected to date (<2 x 10(21) Gauss-cubic centimeter), but here the discovery of multiple magnetic anomalies of small spatial scale in the crust of Mars is reported.     

Case Study: Chronic Erysipelas of the Sow – a Subclinical Manifestation of Reproductive Problems

Systemic infections with Erysipelothrix rhusiopathiae are usually associated with skin lesions, vegetative endocarditis and arthritis, but they can also cause reproductive symptoms such as abortion, increased stillbirths, and smaller litter size. In a large Hungarian breeding unit that had ceased to vaccinate the sows against erysipelas, an increased incidence of pre- and post-partal vulval discharge, increased weaning-to-oestrus intervals, decreased farrowing rates, and reductions in total number of pigets born and live-born litter size were reported. Anterior vaginal swabs were obtained from 64 sows shortly before parturition and they all yielded heavy growths of E. rhusiopathiae . A vaccination programme with a killed vaccine was reinstated and subsequently the incidence of vulval discharge and weaning-to-oestrus intervals were decreased and total born and live-born litter size were increased. In the absence of a control group definitive conclusions can not be made regarding the effect of vaccination against E. rhusiopathiae on sow fertility. However, it is not unreasonable to suggest that the aetiology of the reduced sow fertility in the present herd did involve E. rhusiopathiae and that appropriate vaccinations subsequently protected the sows from the disease.     

Sickness, mortality and the buller steer syndrome in a western Canadian feedlot

Objective To determine if an association existed between sickness, mortality and bullers in a western Canadian feedlot.
Design A retrospective epidemiological study.
Animals 78,445 male cattle that entered a 24,000-head feedlot in western Canada from 1991 to 1993.
Procedure Animal health records for bullers were collected and analysed to see if they were at greater risk of sickness and mortality than other steers, and to see if pens with a high prevalence of bullers also had a high prevalence of sickness and mortality.
Results The prevalence of bullers increased with increasing age of cattle on arrival at the feedlot (R = 0.36; P < 0.001). Sickness and mortality decreased with increasing age of cattle on arrival. However, sickness and mortality in bullers relative to other steers actually increased with increasing age on arrival suggesting an interaction existed between sickness and bullers. Bullers were significantly (P < 0.05) more likely to get sick and to die than other steers. In all cases, there was a strong temporal association between sickness and bullers, with sickness and bullers mostly occurring within the first 30 days of the feeding period. On average, pens of cattle with a high prevalence of bullers did not have a correspondingly high prevalence of sickness or mortality.
Conclusion This study suggests that sickness is an effect modifier of dominance behaviour and therefore bullers in feedlot steers. Bullers should always be checked for signs of sickness and treated accordingly. Further research is needed to investigate the effects of sickness on dominance behaviour in pens of feedlot cattle.     

Effects of temperature, soil water status, and soil type on swine slurry nitrogen transformations

Manure N dynamics are affected by manure characteristics, soil factors, and environmental conditions. An incubation experiment was conducted to assess the relationship of these factors. The effects of temperature (11, 18, and 25°C), soil texture (three soils, silt loam to sandy loam), and soil water status (constant at 60% water filled pore space, WFPS, and fluctuating between 30% and 60% WFPS) on net mineralization and nitrification of swine manure N were assessed. Swine manure was applied at an equivalent rate of 350 kg total N ha^-1 to 250 g air-dry soil in 2-l canning jars. Subsamples were taken from each jar for NO₃^- and NH₄⁺ determination when fluctuating moisture treatment dried to 30% WFPS, with sampling continuing through four wet-dry cycles at each temperature. Manure NH₄⁺ was rapidly nitrified to NO₃^-. The relationship between NO₃^- accumulation and degree days after application (DDAA, 0°C base) could be described across temperatures using a single pool exponential model for each soil. More NO₃^- accumulated in coarser-textured soils (150-200 mg N kg^-1 soil), compared to 130 mg N kg^-1 soil in the silt loam soil. Fluctuating soil water status did not alter estimates of rate and extent of NO₃^- accumulation, but slowed NH₄⁺ disappearance somewhat.     

Impacts of the Cretaceous Terrestrial Revolution and KPg extinction on mammal diversification

Previous analyses of relations, divergence times, and diversification patterns among extant mammalian families have relied on supertree methods and local molecular clocks. We constructed a molecular supermatrix for mammalian families and analyzed these data with likelihood-based methods and relaxed molecular clocks. Phylogenetic analyses resulted in a robust phylogeny with better resolution than phylogenies from supertree methods. Relaxed clock analyses support the long-fuse model of diversification and highlight the importance of including multiple fossil calibrations that are spread across the tree. Molecular time trees and diversification analyses suggest important roles for the Cretaceous Terrestrial Revolution and Cretaceous-Paleogene (KPg) mass extinction in opening up ecospace that promoted interordinal and intraordinal diversification, respectively. By contrast, diversification analyses provide no support for the hypothesis concerning the delayed rise of present-day mammals during the Eocene Period.     

Musculoskeletal responses of 2-year-old Thoroughbred horses to early training. 7. Bone and articular cartilage response in the carpus

AIM: To describe features of the morphology of the carpus, quantify the thickness of hyaline and calcified cartilage, and to describe the morphology and density of subchondral bone in the third carpal bone (C3) of young Thoroughbred horses in early training.

METHODS: C3 of seven 2-year-old horses in training and seven untrained horses matched for age, sex and breed were assessed by gross appearance, computed tomography, fine-structure radiography, image analysis of high-resolution photographs, and histology.

RESULTS: Macroscopic lesions in cartilage were few and mild, and not significantly different between groups. High bone mineral density (BMD), in some cases typical of cortical bone, was confined to the dorsal load path, and was significantly higher in trained than in untrained horses (p<0.01). In the most dorsoproximal aspect of the radial articular facet, apparently outside the dorsal load path, the BMD in both trained and untrained horses was significantly less than in other regions of interest (ROIs). Adaptive increase in density was associated with thickening of the (junctions of) trabeculae oriented proximo-distally. Hyaline cartilage was thicker (p<0.001) in the concavity of the radial articular facet than dorsal or palmar to it, and was thicker in the trained than untrained group (p=0.007). No such differences were detected in the thickness of articular calcified cartilage (ACC).

CONCLUSIONS: The rapid response of bone in C3 to relatively small amounts of high-speed exercise was confirmed. A previously unreported increase in thickness of hyaline cartilage was evident, perhaps indicating that this tissue may be more responsive than hitherto thought, at least to particular types of exercise at particular times. These changes occurred with little evidence of abnormality, and thus appeared to be adaptive to the exercise regimen. The model developed should be used for further definition of the exercise stimulus required to produce adaptive, protective changes in sites susceptible to athletic injury.

CLINICAL RELEVANCE: The data will serve as reference for use in subsequent imaging studies in which sophisticated aids such as magnetic resonance imaging (MRI) may be used to predict carpal lesions.