Identification of dynamic growth of Hedera helix as response to variation in daily light levels

Summary

The dynamic responses in shoot growth of three pot plants ofHedera helix L. ‘Mein Herz‘ in relation to changes in photosynthetic photon flux density (PPFD) is identified. In the experiment a two-level strategy of PPFD to the plants was used. The current level of PPFD on any day was either high or low, and was determined using a pseudo random binary signal (PRBS) both to avoid any correlations between the PPFD and other variables, and to ensure that the dynamic characteristics of the plant growth were present in the data. For each of the three pot plants a discrete dynamic model of growth responses to PPFD was estimated, and an agreement between the parameters of the three models was observed. The results show that not only is the current PPFD level of the current day related to the daily increase in fresh weight, but growth is also a function of the PPFD level of the previous days. With respect to the previous days the effects of PPFD can be described as an exponential decay where from one day to the previous day the effect of PPFD is reduced to 67%, 66% and 80% respectively for the three pot plants in the experiment.     

Angiotensin Converting Enzyme in Bovine Ovarian Follicular Fluid and its Relationship with Oestradiol and Progesterone

The purpose of the present study was to identify angiotensin converting enzyme (ACE) in bovine ovarian follicular fluid and to relate the ACE activity to the phase of the oestrous cycle, pregnancy, and the follicular fluid concentrations of oestradiol and progesterone. The ACE activity was similar to that found in bovine serum and was completely inhibited by the specific ACE inhibitor captopril. The 50% inhibitory concentration (IC₅₀) was 1.4 × 10^?8 mol/l (range 0.8 × 10^?8 to 5.0 × 10^?8 mol/l; n=6), which is similar to that found in bovine and human serum. The ACE activity did not differ in the pre‐ovulatory and luteal phase, pregnancy or cystic follicles. It correlated with the follicular fluid concentration of progesterone in cycling cows (ρ=0.476; p < 0.005; n=36), but did not correlate with the diameter of the follicles, the follicular fluid concentration of oestradiol or the ratio between the oestradiol and progesterone concentrations. The demonstration of ACE in bovine ovarian follicular fluid provides further evidence for the presence of a local renin–angiotensin system in the bovine ovary.     

Dairy farmers' reasons for participation in the Danish control programme on bovine paratuberculosis

The Danish dairy industry initiated a voluntary, producer-paid control programme on Mycobacterium avium subsp. paratuberculosis (MAP) in 2006. Approximately 28% of the dairy herds, including 40% of the cows, are part of the programme. Farmers' reasons for participation are of great importance for the success of voluntary disease control programmes. This study was carried out to determine these reasons. Questionnaires with seven close-ended questions were mailed to the 1177 voluntary participants in 2008. A total of 1013 (86%) responded, and multiple reasons could be given by each farmer. The distribution of reasons for participation in the programme was: (1) control to increase animal health (91%); (2) certification "free of MAP infection" within 4-10 years (87%); (3) control to avoid production losses associated with MAP infections (86%); (4) control of MAP infections to increase consumer safety (64%); (5) certification for sale of livestock (58%); (6) control following production losses (48%); and (7) certification "free of MAP infection" within 1-3 years (31%). It was not possible to rank the reasons for participation since weighting of responses was not included. Therefore, the relative importance of the reasons given could not be determined. Based on the farmers' responses, control of MAP infections to increase animal health and avoid production losses were frequent reasons for participating in the Danish paratuberculosis control programme. The results also indicate that implementation of a certification programme would be desired by farmers. Animal health advisors should consider the diversity of participation reasons and address the specific reasons of individual farmers when establishing a strategy for control of MAP infections in a herd.     

The Pathology of Arylmercurial Poisoning in Swine

To produce arylmercurial poisoning, phenylmercuric chloride (PMC) was administered daily to 30 healthy five week-old piglets for periods of up to 90 days. The dosage used ranged from 0.19 to 4.56 mg of mercury (Hg)/kg. Levels exceeding 2.28 mg Hg/kg daily were moderately toxic.

The disease occurring in this intoxication resulted from injury to the kidneys and large intestine. Fetid diarrhea and failure to gain weight were consistent clinical signs. The primary gross lesions were necrotic typhlitis and colitis, and nephrosis. Degeneration and necrosis were found in affected organs. Regeneration was prominent in the proximal convoluted tubules.

The pathology of this disease was similar to that described for mercuric chloride poisoning in other species and, presumably, reflected the ease with which PMC was metabolized to release mercuric ion.

Tissue analysis for mercury suggested that only certain target organs, such as kidney and colon, accumulated significantly high levels of mercury. This, presumably, resulted from rapid metabolism of the compound and excretion of mercuric ion in the kidney and colon. The net effect was to spare other tissues, and to injure the excretory organs when the dose level was sufficiently high.

     

A mass attack by the biting midge culicoides nubeculosus (Mg.) (Dipteria, Ceratopogonidae) on grazing cattle in Denmark. A new aspect of sewage discharge.

A consequence of sewage discharge into a shallow marsh pool was large-scale hatching of the biting midge Culicoides nubeculosus from the recipient and mass attacks by this blood-sucking insect on grazing cattle. Culicoides nubeculosus is a great nuisance due to the painful bite and in Denmark it is a potential vector of pathogenic agents. In the future, these aspects of sewage discharge must be borne in mind.     

Simulated economic effects of improving the sensitivity of a diagnostic test in paratuberculosis control

Low sensitivity (Se) of diagnostic tools is often mentioned as a major problem in the control of paratuberculosis (PTB) and much effort is put into the improvement of these tests. The hypothetical perspectives of improving the Se of a milk-antibody ELISA (hereafter: milk-ELISA) used in test-&-cull strategies against PTB in dairy cattle were investigated by simulations. The current Se varies between 10 and 80%, increasing with increasing lactation stage, parity and infection stage. We simulated the effects on a dairy herd's production of improving this Se to 80% (independent of these factors) and assumed no concomitant decrease in specificity. By using a PTB model called PTB-Simherd, 12 scenarios were simulated to study three test-&-cull strategies in each of four herds with 200 dairy cows. To show the maximal effect of using test-&-cull with such an improved test we simulated three strategies: (1) no testing, (2) testing with milk-ELISA test with the current Se and culling of positive cows immediately and (3) testing with milk-ELISA test with a Se improved to 80% and culling positive cows immediately. The four herds were defined by a moderate (25%) or high (80%) initial true within-herd prevalence (including young stock), and a poor or good heat-detection success of 40 or 60%. We assumed that these factors influenced the effects of improving the Se of the milk-ELISA. Management both concerning calf management and in general was specified to represent a typical Danish herd. Using an improved milk-ELISA was predicted to reduce the prevalence of PTB more effectively than the current ELISA, and over 10 years bring the production of a herd with moderate initial prevalence up to a production level comparable to a non-infected herd (unlike if the current ELISA had been used). In a herd with high initial prevalence (80%) milk production was increased more by using the improved milk-ELISA, but after 10 years the replacement rate was still very high causing problems with having enough recruitment animals-especially in high-prevalence herds with poor reproductive performance. Economically important measurements in all four herds benefited from the improvement of the test over a 10-year period. However, in the first 3-5 years the improved test would be more expensive to use than the current test, due to increased replacement (reduced net annual revenue per cow euro15 on average) but after that, net annual revenue increased continuously; after 10 years it was euro70-90 higher, than if the current milk-ELISA was used. Also, the milk-ELISA test with its current Se seemed to be profitable already after 2 years in high-prevalence herds using a test-&-cull strategy based on the milk-ELISA alone.