Nitrogen Fixation by Irrigated Berseem Clover versus Soil Nitrogen Supply

Nitrogen fixation was estimated by the difference method for two cultivars of berseem clover ( Trifohum alexandrinum L.), using annual ryegrass ( Lolium multiflorum Lam.) as the control in field trials from 1983 to 1988. Five or six cuttings were obtained each year under supplemental irrigation, and dry matter production and uptake of nitrogen into harvested forage were measured.
Estimates of nitrogen fixation by berseem clover ranged from 272 to 400 kg N/ha depending on year and cultivar, while plant N derived from soil (based on N uptake by the ryegrass) ranged from 50 to 235 kg N/ha. Graphs of nitrogen fixed versus available soil nitrogen had a reverse linear-plateau shape with a plateau at lower soil nitrogen levels that broke sharply in a linear decline as available soil N surpassed a minimum threshold. Such a two-phase response suggests that nitrogen fixation by the clover was limited by soil N supply above this threshold and by other limiting factors at low soil N levels, perhaps genetic traits controlling carbon assimilation or environmental limitations other than nitrogen. Seasonal nitrogen process patterns showed abundant nitrogen fixation by the clover after it had depleted most of the soil nitrogen supply.     

Prevalence and intensity of non-strongyle intestinal parasites of horses in northern Queensland

A quantitative post-mortem study of 57 horses from northern Queensland was done to determine the prevalence and intensity of non-strongyle intestinal parasites. The following species (% prevalence) were found: Draschia megastoma (39%); Habronema muscae (43%); Gasterophilus intestinalis (34%), G. nasalis (30%); Parascaris equorum (15%); Strongyloides westeri (6%); Probstmayria vivipara (2%); Oxyuris equi (26%); Anoplocephala magna (2%); A. perfoliata (32%). Mean parasite numbers of individual species ranged from 10 to 1310. Prevalence and intensity data were compared to recent studies in Western Australia and in the United States of America. Differences between stabled and paddocked horses were noted, particularly for botfly larvae and spiruroids. Climatic and seasonal changes in prevalence were restricted to H. muscae, G. nasalis and P. equorum with highest prevalence in the wet season or in horses from wet coastal areas. Only P. equorum showed any age effect being restricted to horses less than 5 years old. Breed and sex of horses was not important. The likelihood of changing parasite population dynamics with improved anthelmintic regimen is discussed.     

Biodiversity assessment and conservation strategies

The efficient representation of all species in conservation planning is problematic. Often, species distribution is assessed by dividing the land into a grid; complementary sets of grids, in which each taxon is represented at least once, are then sought. To determine if this approach provides useful surrogate information, species and higher taxon data for South African plants and animals were analyzed. Complementary species sets did not coincide and overlapped little with higher taxon sets. Survey extent and taxonomic knowledge did not affect this overlap. Thus, the assumptions of surrogacy, on which so much conservation planning is based, are not supported.     

Expression of behavioural signs of oestrus during mid-cycle in a dairy cow

Abstract

Extract

Routine monitoring of commercial dairy herds has confirmed the occurrence of oestrus during the luteal phase of the cycle in a small proportion (<5%) of cows (Royal et al 2000 Royal, MD, Darwash, AO, Flint, APF, Webb, R, Wooliams, JA and Lamming, GE. 2000. Detecting fertility in dairy cattle: changes in traditional and endocrine parameters of fertility. Animal Science, 70: 487–501.  [Google Scholar]). One such event occurred in one of four Friesian dairy cows being intensively monitored for progesterone and luteinising hormone (LH) concentrations in daily milk samples and 6-hourly blood samples collected from the jugular vein, throughout the postpartum period (Peters et al 1981 Peters, AR, Lamming, GE and Fisher, MW. 1981. A comparison of plasma LH concentrations in milked and suckling post-partum cows. Journal of Reproduction and Fertility, 62: 567–573.  [Google Scholar]; Fisher 1983 Fisher, MW. 1983. “The control of reproduction in the post-partum cow”. In PhD thesis, Sutton Bonington, , UK: Nottingham University.  [Google Scholar]). Consequently, the endocrine parameters associated with heat during the luteal phase were noted (Figure 1). Although an observation on a single cow, the intensive sampling data available for this animal warrant publication.     

Distribution of K and L cells in the feline intestinal tract

Glucose-dependent insulinotropic peptide (GIP), glucagon-like peptide (GLP)-1 and GLP-2 are hormones secreted from specialized K cells (GIP) and L cells (GLP-1, GLP-2) in the intestinal mucosa. These hormones play major roles in health and disease by modulating insulin secretion, satiety, and multiple intestinal functions. The aim of this study was to describe the distribution of K cells and L cells in the intestines of healthy cats. Samples of duodenum, mid-jejunum, ileum, cecum, and colon were collected from 5 cats that were euthanized for reasons unrelated to this study and had no gross or histologic evidence of gastrointestinal disease. Samples stained with rabbit-anti-porcine GIP, mouse-anti-(all mammals) GLP-1, or rabbit-anti-(all mammals) GLP-2 antibodies were used to determine the number of cells in 15 randomly selected 400× microscopic fields. In contrast to other mammals (eg, dogs) in which K cells are not present in the ileum and aborally, GIP-expressing cells are abundant throughout the intestines in cats (>6/high-power field in the ileum). Cells expressing GLP-1 or GLP-2 were most abundant in the ileum (>9/high-power field) as in other mammals, but, although GLP-1–expressing cells were abundant throughout the intestines, GLP-2–expressing cells were rarely found in the duodenum. In conclusion, the distribution of GIP-secreting K cells in cats is different from the distribution of K cells that is described in other mammals. The difference in distribution of GLP-2– and GLP-1–expressing cells suggests that more than 1 distinct population of L cells is present in cats.     

Agroforestry for high value tree systems in Europe

Most farm-based agroforestry projects focus on the integration of trees on arable or livestock enterprises. This paper focuses on the integration of understorey crops and/or livestock within high value tree systems (e.g., apple orchards, olive groves, chestnut woodlands, and walnut plantations), and describes the components, structure, ecosystem services and economic value of ten case studies of this type of agroforestry across Europe. Although their ecological and socio-economic contexts vary, the systems share some common characteristics. The primary objective of the farmer is likely to remain the value of tree products like apples, olives, oranges, or nuts, or particularly high value timber. However there can still be production, environmental or economic benefits of integrating agricultural crops such as chickpeas and barley, or grazing an understorey grass crop with livestock. Three of the systems focused on the grazing of apple orchards with sheep in the UK and France. The introduction of sheep to apple orchards can minimise the need for mowing and provide an additional source of revenue. Throughout the Mediterranean, there is a need to improve the financial viability of olive groves. The case studies illustrate the possibility of intercropping traditional olive stands with chickpea in Greece, or the intercropping of wild asparagus in high density olive groves in Italy. Another system studied in Greece involves orange trees intercropped with chickpeas. Stands of chestnut trees in North-west Spain can provide feed for pigs when the fruit falls in November, and provide an excellent habitat for the commercial production of edible mushrooms. In Spain, in the production of high quality walnut trees using rotations of up to 50–60 years, there are options to establish a legume-based mixed pasture understorey and to introduce sheep to provide financial and environmental benefits.