Reproductive performance in South Australian dairy herds

SUMMARY Herd breeding records (161) were examined from a random 10% sample of dairy farms (96) in South Australia with more than 40 cows and suitable breeding records for 1988 and/or 1989. Of these farms, 53 (55.2%) had a year-round calving pattern, 42 (43.8%) claimed to be seasonal and one was changing from a year-round to a seasonal pattern. Only 14.6% of farmers observed oestrous behaviour outside milking times and 18.8% used tailpaint. Overall, the average proportion of unobserved heats was estimated to be 32%. Artificial insemination (AI) was carried out on 85.4% of farms (16.7% used AI alone and 68.7% also used bulls) of which 32.9% used commercial technicians and 67.1% were do-it-yourself operators. Overall, the average 30-day submission rate was 59.9% and the average 49-day non-return to service rate was 58.9%. Investigation into the probable causes of suboptimal reproductive performance gave a tentative diagnosis of inefficient oestrous detection, deferral of service, inadequate nutrition, poor AI technique, insufficient bulls, and venereal/other diseases in 69.1, 32.1, 27.2, 28.4, 13.6 and 7.4% of records, respectively.     

Stabilisierung der Erträge virusinfizierter Kartoffelherkünfte durch das antiphytovirale Präparat 2,4-Dioxohexahydrotriazin

Zusammenfassung In mehrj?hrigen Parzellenversuchen wurde durch Behandlung mit 2,4-Dioxohexahydrotriazin (DHT), einer neu entwickelten antiphytoviralen Substanz im Durchschnitt von 57 st?rker virusinfizierten Herkünften (durchschnittlicher Virusbesatz 24.6%) der Ertrag hochsignifikant um 1.1 t/ha (=6.5%) erh?ht. Bei 49 gesunden Herkünften (durchschnittlicher Virusbesatz 4.8%) wurden demgegenüber die Ertr?ge nicht ver?ndert. Demnach darf die angeführte Ertragserh?hung der antiviralen Wirkung des DHT zugeschrieben werden. In 44 Grossfl?chenversuchen in Konsumkartoffelbest?nden (Virusbesatz etwa zwischen 10 und 30%), wurde der Ertrag hochsignifikant um 1.4 t/ha (=8.0%) erh?ht. Werden die im trocken-heissen Jahr 1976 in ausgesprochenen Dürregebieten erhaltenen Ergebnisse eliminiert, ergeben sich in den Parzellenversuchen mit virusinfizierten Herkünften hochsignifikante Mehrertr?ge von 1.9 t/ha (=9.7%) und bei den Grossfl?chenversuchen von 2.3 t/ha (=12.6%).

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Summary Studies have been made to determine whether the use of 2.4-dioxohexahydrotriazine (DHT), a newly developed antiphytoviral compound with satisfactory virostatic activity and a favourable chemotherapeutic index (Schuster et al., 1979a, b) can reduce or prevent viral depression of the yield of ware potatoes. Between 1973 and 1977 a total of 106 plot tests were made, using a block design with four replicates. In addition, between 1975 and 1977, 44 large-scale field trials were carried out, the area treated in most of these being 20 ha. In every case, yields from plants treated with DHT five times at intervals of fourteen days were compared with those from untreated control plants. Seed stocks used for the plot tests were classified on the basis of eye excision tests as ‘healthy’ (virus infection less than 10%, average 4.8%) or ‘virus-infected’ (infection greater than 10%, average 24.6%). In the case of 57 ‘virus-infected’ stocks, DHT treatment resulted in a highly significant increase in yield—on average 1.1 t/ha=6.5% (Table 1). On the other hand, treatment with DHT had no material effect on the yield from 49 ‘healthy’ stocks. This indicates that the increase in yield resulted from the antiviral activity of DHT. In the 44 large-scale field trials, carried out in ware crops in which the level of virus infection was generally between 10% and 30%, a highly significant increase in yield was obtained — on average 1.4 t/ha=8%. Included in the data, however, are minor increases in yield recorded in the trials carried out in 1976 (an unusually hot, dry year) in areas badly affected by drought. If these are ignored, a highly significant average increase in yield of 1.9 t/ha=9.7% is obtained when the results of the plot and field trials are combined (Table 1). It is evident from these results that a considerable increase in yield may be obtained through the use of DHT to stabilize yields from virus infected seed stocks. This antiviral preparation has the added advantage of being non-toxic and very economical in use.

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Résumé Des études ont été effectuées afin de conna?tre dans quelle mesure la 2,4-dioxohexahydrotriazine (DHT), substance antiphytovirale nouvellement développée, permet de réduire ou d'éviter les chutes de rendement dans les cultures de pommes de terre de consommation. Ce produit ralentit considérablement, et de manière durable la reproduction du PVX ainsi que celle d'autres virus (Schuster et al., 1979a, b). Au cours des années 1973 à 1977, 106 parcelles disposées en blocs avec 4 répétitions ont été testées. D'autre part, de 1975 à 1977, 44 essais en grande culture couvrant une surface de 20 ha ont été effectués. Dans tous les cas, les surfaces traitées 5 fois à la DHT, à des intervalles de 14 jours, ont été comparées avec des parcelles non traitées. Lors de la récolte des parcelles, il a été prélevé un tubercule par plante pour un postcontr?le virologique. Suivant les résultats du test, les plants ont été classés selon leur taux de contamination par les virus. Pour les lots présentant un taux de contamination de moins de 10% au départ, le taux de contamination moyen fut de 4.8%. Les lots contaminés à plus de 10% présentèrent une attaque moyenne de 24%. Dans les lots contaminés par le virus, la DHT cut pour effet une augmentation hautement significative du rendement, soit 1,1 t/ha (=6,5%, tableau 1). En revanche, par le traitement de 49 parcelles saines, les rendements n'ont pas été influencés par la DHT. Par conséquent, l'augmentation du rendement mentionnée peut être attribuée à l'action anti-virale de la DHT. Sur 44 essais de pommes de terre de consommation en grande culture où la proportion de plantes contaminées atteignait 10–30%, une augmentation hautement significative de rendement a été obtenue, 1,4 t/ha (8.0%). Ces chiffres comprennent également les résultats des essais 1976, année chaude et séche dans certaines régions. En excluant les résultats de 1976, on obtient par les traitements sur les essais parcellaires, une augmentation de récolte hautement significative, soit 1,9 t/ha (=9.0%), et 11,3% pour les traitements en grande culture (tableau 1). Ces résultats démontrent que par le traitement avec la préparation anti-virale DHT, une augmentation non négligeable de rendement peut être obtenue sur des cultures contaminées par le virus, les frais étant économiquement acceptables.

     

Effect of Grazing-Mediated Dimethyl Sulfide (DMS) Production on the Swimming Behavior of the Copepod Calanus helgolandicus

Chemical interactions play a fundamental role in the ecology of marine foodwebs. Dimethyl sulfide (DMS) is a ubiquitous marine trace gas that acts as a bioactive compound by eliciting foraging behavior in a range of marine taxa including the copepod Temora longicornis. Production of DMS can rapidly increase following microzooplankton grazing on phytoplankton. Here, we investigated whether grazing-induced DMS elicits an increase in foraging behavior in the copepod Calanus helgolandicus. We developed a semi-automated method to quantify the effect of grazing-mediated DMS on the proportion of the time budget tethered females allocate towards slow swimming, typically associated with feeding. The pooled data showed no differences in the proportion of the 25 min time budget allocated towards slow swimming between high (23.6 ± 9.74%) and low (29.1 ± 18.33%) DMS treatments. However, there was a high degree of variability between behavioral responses of individual copepods. We discuss the need for more detailed species-specific studies of individual level responses of copepods to chemical signals at different spatial scales to improve our understanding of chemical interactions between copepods and their prey.     

Some effects of termitaria on veld in the eastern Cape

A survey was conducted to determine some effects of termite mounds on the veld. Termitaria were found to occupy approximately 0,4% of the area of the paddock under investigation. Growth of grasses immediately surrounding intact termitaria increased as shown by the higher number of tillers and a high percentage of reproductive tillers. Although the plant species composition surrounding intact termitaria did not appear to differ very much from the adjacent veld, weathered termitaria revealed a change in species more typical of disturbed conditions. Nitrogen content was highest in soil from the centre of intact termitaria, but there were no significant differences in the surface soil from the edge of termitaria, from weathered mounds, or from undisturbed veld. Runoff from termitaria caused increased moisture penetration surrounding the mounds. The significance of an infestation of termite mounds on the veld is discussed.     

Nutrient Biogeochemistry of the Coastal Zone

The coastal seas are one of the most valuable and vulnerable of Earth's habitats. Significant inputs of nutrients to the coastal zone arrive via rivers, groundwater, and the atmosphere. Nutrient fluxes through these routes have been increased by human activity. In addition, the N:P:Si ratios of these inputs have been perturbed, and many coastal management practices exacerbate these perturbations. There is evidence of impacts arising from these changes (in phytoplankton numbers and relative species abundance, and deep-water oxygen declines) in areas of restricted water exchange. Elsewhere, the nutrient fluxes through the coastal zone appear to be still dominated by large inputs from the open ocean, and there is little evidence of anthropogenic perturbations.     

Identification of shark and ray fins using DNA barcoding

Fisheries managers and scientists worldwide are struggling with a lack of basic information for many shark and ray species. One factor hampering the data collection is inaccurate identification of many chondrichthyan species and their body parts. Morphologically similar species, and specimens which are poorly preserved or have had key diagnostic features removed, can be difficult to identify. This study examined DNA barcoding as a method to identify shark species from dried fins, confiscated from a vessel fishing illegally in Australian waters. 211 left pectoral fins were examined. 18 either did not provide a sequenceable product or yielded a microbial sequence, while 193 fins (91.5%) provided a chondrichthyan sequence. All of these could be matched to reference specimens in a DNA barcode database, and so were able to be identified. 27 species were detected, 20 species of sharks and seven species of rays The most abundant species (22% of fins) was Carcharhinus dussumieri. Many of these species are listed on the World Conservation Union (IUCN) Red List and include one, Anoyxpristis cuspidata (3%), rated as critically endangered. Fishing authorities can use DNA barcoding to gather data on which chondrichthyan species are targeted by illegal fishers, information that will greatly assist in management and conservation.     

A preliminary account of growth characteristics and seed germination of Cassia mimosoides L. in Dohne Sourveld

An autecological study of Cassia mimosoides L., which invades mismanaged Dohne Sourveld, was initiated at the Agricultural Research Institute, Dohne. A study of the growth characteristics revealed that the nature of the root distribution enabled the plant to take up moisture from superficial as well as deeper soil layers, while the position of the crown buds at or below soil level offered protection from fire damage. These characteristics plus the unpalatability of the plant to sheep and cattle placed it in a favourable position in competition with grasses. However, the relatively low‐growing C. mimosoides plants appeared to be at a disadvantage in rested veld. Although seeds were dormant when released, germination took place and seeds retained their viability over a long period. Under natural conditions the germination of non‐dormant seeds was controlled largely by temperature and moisture. Few seedlings established themselves in rested veld. It was suggested that a long rest period for the veld, followed by a spring burn, would be most effective in controlling the establishment of seedlings.     

Translocation of radioactive paraquat in some veld grasses

In two pot experiments radioactive paraquat was applied to certain important veld grasses (Experiment I — Aristida junciformis, Themeda triandra, Elyonurus argenteus, Andropogon filifolius, Eragrostis cur‐vula ; Experiment II — A. junciformis, E. argenteus) to determine the extent of translocation at a young stage of growth and with treatment at different times of the day. In the first experiment movement occurred in all grasses along the length of the treated leaf, while in E. curvula and A. filifolius the herbicide was translocated to other leaves also. The second experiment indicated the importance of application of paraquat at. 1700 hours for maximum translocation.