Variations in the number of nucleoli in the granulosa cells of the domestic fowl during follicular growth

1. The proportions of granulosa cells containing one, two, or more nucleoli were determined in ovarian follicles of the domestic fowl (Gallus domesticus). Follicles ranged in size from 5 to 37 mm diameter.

2. The greatest proportion of cells (65%) contained one nucleolus. Cells containing two nucleoli were fewer (29%) and those containing more than two were rare (6%).

3. There was a tendency for the proportion of multinucleolar cells to decrease with increasing size of the follicle. Conversely there was a similar tendency for the proportion of cells with single nucleoli to increase with size of the follicle. These relationships are curvilinear.

4. Suitable linear models confirmed these observations (P < 0.005).

5. These results may provide an explanation for the previously reported progressive decrease in cellular DNA as the follicle increases in size.     

A field study on estrus detection in lactating beef cattle

Estrus detection efficacy and heat detection protocol were studied by means of a field study carried out on 878 lactating beef cows in 60 French herds. Average herd size was 48, and 75% of the farmers partly or exclusively used artificial insemination. The cows were calved between October 1992 and March 1993. Estrus was recorded daily by the farmers. Cycling status was determined by progesterone radioimmuno-assay 2 months after calving. The relationship between the estrus detection protocol and the delay period from calving to first observed estrus was analysed using survival curves and the Cox proportional hazard model, adjusting for confounders. Seventy-one percent of the cows were seen in estrus by the farmers; the interval between calving and the first observed estrus ranged from 9 days to more than 5 months and the median was 56 days. Two months after calving, 44% of the cycling cows had not been seen in heat by the farmers and 11% of the non-cycling cows had been reported to have been in estrus. The heat detection protocol varied widely between farmers, depending on the considered estrus signs, schedule and time spent looking for signs. Two factors were significantly related to a shorter interval from calving to first observed heat: the use of artificial insemination (which relates to the farmer's interest in heat detection) and an overall daily time spent for heat detection greater than 1 h. Cows in tie stalls had a delayed interval to the first observed estrus. These results show that many farmers did not adapt their reproduction practice sufficiently to an earlier calving period. There is room for improvement since in many cases the heat detection protocol does not match the required standards for optimal heat detection.     

Electrical stunning of red deer (Cervus elaphus)

Eighteen of 23 red deer (Cervus elaphus) at a deer slaughtering premises were successfully stunned with an apparatus modified from that normally used to stun sheep. The five unsuccessful electrical stuns were associated with poor head restraint and poor head contact by the electrodes. The median stunning current was 0.9 A, and in the majority of cases the duration of stunning was less than 1 second. The signs of the electrically induced epileptiform seizures in the deer were dissimilar to those seen in sheep, cattle and pigs, in that the initial tonic phase was less marked, and of shorter duration. A similar shorter and less obvious tonic phase was noted in four deer shot with a captive bolt pistol. Two animals which were electrically stunned, and bled within 10 seconds, showed no signs of recovery while bleeding. The electroencephalograms of four deer stunned with currents of 1.3 A for a duration of either 0.5 or 1.0 seconds were recorded under more controlled conditions. All four animals developed electroencephalograms typical of an epileptiform seizure. The animals exhibited behavioural reactions similar to the other 18 animals in the trial at the deer slaughtering premises and were rendered unconscious for between 54 and 122 seconds. The electroencephalogram activity amplitude was greater than that recorded immediately before stunning and took between 6 and 9 seconds to build up to maximum value. It is concluded that, providing the heads of deer are adequately restrained, head-only electrical stunning can be incorporated into a humane method of slaughter for deer.     

Staphylococcus aureus lipoteichoic acid triggers inflammation in the lactating bovine mammary gland

The response of the bovine mammary gland to lipoteichoic acid (LTA), which is a major pathogen-associated molecular pattern of Gram-positive bacteria, was investigated by infusing purified Staphylococcus aureus LTA in the lumen of the gland. LTA was able to induce clinical mastitis at the dose of 100 microg/quarter, and a subclinical inflammatory response at 10 microg/quarter. The induced inflammation was characterized by a prompt and massive influx of neutrophils in milk. LTA proved to induce strongly the secretion of the chemokines CXCL1, CXCL2, CXCL3 and CXCL8, which target mainly neutrophils. The complement-derived chemoattractant C5a was generated in milk only with the highest dose of LTA (100 microg). The pro-inflammatory cytokine IL-1beta was induced in milk, but there was very little if any TNF-alpha and no IFN-gamma. The re-assessment of CXCL8 concentrations in milk whey of quarters previously challenged with S. aureus, by using an ELISA designed for bovine CXCL8, showed that this chemokine was induced in milk, contradicting previous reports. Overall, S. aureus LTA elicited mammary inflammatory responses that shared several attributes with S. aureus mastitis. Purified LTA looks promising as a convenient tool to investigate the inflammatory and immune responses of the mammary gland to S. aureus.     

Hatching and nutritional quality of Artemia cysts progressively deteriorates as a function of increased exposure to hydration/dehydration cycles

Nauplii hatching from Artemia cysts are crucial in larviculture nutrition. Artemia cysts may be exposed to repeated hydration/dehydration (H/D) cycles pre-harvesting or during processing and storage. To observe the effect of these cycles on cyst quality, Artemia franciscana cysts were exposed to a comprehensive set of various H/D treatments, differing in the number of cycles (1, 2, or 3) and the duration of the freshwater hydration period (2 or 4 h). Cyst quality was assessed using the criteria of immediate relevance for aquaculture use, such as hatching percentage directly after H/D treatment and after ?18 °C storage up to 1 month, longevity of axenically hatched starved nauplii, cyst and naupliar energy content, and (for the most extreme H/D treatment) cyst and naupliar fatty acid and vitamin C content. Repeated H/D cycles resulted in significantly (P < 0.05) decreased cyst hatching, reduced starved naupliar longevity and individual energy content, loss in vitamin C and fatty acid content, and moreover a close correlation between these parameters as a function of progressive H/D treatments. This is of immediate relevance for aquaculture nutrition, as commercial Artemia cysts may have gone through an unknown sequence of H/D cycles in nature or in the processing line, which affects the nutritional quality of the nauplii used in larviculture operations.     

Hydration/dehydration cycles imposed on <Emphasis Type="Italic">Artemia</Emphasis> cysts influence the tolerance limit of nauplii against abiotic and biotic stressors

The brine shrimp Artemia franciscana is an important live feed for fish and shellfish larviculture. Cysts of Artemia are naturally found in a wide variety of harsh environments worldwide where they are exposed to different changing environmental conditions. Artemia cysts are also exposed to different hydration/dehydration (H/D) conditions during the post-harvest processing period in the Artemia processing industry. In this study, cysts of two strains of A. franciscana originating from two different geographical locations—one a natural population from Great Salt Lake (GSL), Utah, USA, and the other cultured in the Vinh Chau (VC) salt ponds, Vietnam—where they experience different environmental factors, were exposed to successive hydration/dehydration (H/D) cycles with the aim of determining the effects of these conditions on the stress (i.e., induction of Hsp70) and functional (i.e., resistance toward abiotic and pathogenic biotic factors) responses of the emerged nauplii. Our results showed that a short period of H/D of the cysts did not appear to have a deleterious effect on the emerged nauplii of both strains, as was evidenced by the absence of significant difference in the survival of nauplii emerged from the control and treated cysts, upon challenge with a thermal stressor or with pathogenic Vibrio campbellii. A limited exposure to H/D treatment even leads to the induction of enhanced thermotolerance in GSL nauplii. In essence, these observations add some insights to our current understanding of stress responses in Artemia under the described experimental conditions. In addition, the impact of H/D cycles associated with stress response should be taken into consideration when Artemia is considered as a model organism for future research and applications.