Increasing concern about non-point source pollutants released from grazing livestock, a worldwide problem, motivated the present study on the effects of vegetative filter strips (VFS) for controlling pollutants (nutrients, micro-organisms and sediment loading) from grazed, irrigated pastures. Flood-irrigated pastures are an important source of forage for livestock during summer months in California, USA when the surrounding rangelands are dry and dormant. Significant amounts of runoff can be generated from these pastures during irrigation events.

Nine plots on an irrigated pasture were assigned randomly to one of three treatments: Control (no VFS), Treatment VFS-1 (8·3×7 m, 0·0058 ha VFS) and Treatment VFS-2 (17·1×7 m, 0·012 ha VFS). In 2000, two grazing events (in April and June/July) occurred during the irrigation season prior to the experiment; further, the experimental plots were grazed between irrigations 2 and 3. Attenuation of runoff loads by VFS treatment was measured during four irrigation events (between 1 August and 3 October 2000) for total suspended solids (TSS), ortho-phosphate (Ortho-P), inorganic phosphate (Inorg-P), total phosphate (Total-P), organic phosphate (Org-P), polyphosphate (Poly-P), total Kjeldahl nitrogen (TKN), NH3, NO3 and presumptive faecal coliforms (FC).

On average, approximately 0·43 of the applied water left the plots as runoff. Treatment effects approached significance for TSS and TKN and were significant (P<0·05) for Poly-P and NH3. Irrigation number effects were significant for all but TSS, NO3 and FC. The effects of VFS treatments were not consistent. Treatment VFS-2, although representing the largest buffer strip, did not always produce the lowest pollutant loads in runoff. Slope, relatively high runoff volumes and some channelled flow were probably responsible for the limited effectiveness of VFS in the present study. These results suggest that effectiveness of VFS for reducing sediment and nutrient transport from irrigated pastures may be questionable.

Livestock slurries contain organic matter, nitrogen, phosphorus and potassium, which can be recycled in arable systems; however, excess applications can cause pollution problems and therefore an estimation of the nutrients in slurries is necessary. The aim of the present experiment was to test methods of rapidly estimating nutrient contents of pig slurries based on physical and chemical analysis. A total of 216 samples with a dry matter content in the range 22·5 to 91·8 g/kg were collected in Beijing during 2003 and 2004. One part of each original sample was analysed for physical and chemical properties, such as electrical conductivity (EC), pH and specific gravity (SG). The other part of each original sample was analysed in the laboratory to measure organic matter (OM), total nitrogen (TN), ammonium nitrogen (AN), total phosphorus (TP) and total potassium (TK). Analytical results showed that OM could be estimated by a single property regression with SG (R2=0·92, P<0·001), TN could be estimated by a multiple property regression with SG and pH (R2=0·86, P<0·001), AN could be estimated by a single property regression with EC (R2=0·82, P<0·001), TP could be estimated by a single property regression with SG (R2=0·81, P<0·001), and TK could be estimated by a multiple property regression with EC and SG (R2=0·81, P<0·001).

Field experiments were conducted at the village Kasiadihi, Dhenkanal district, Orissa, India during wet seasons 2001, 2002 and 2003 under non water-stressed conditions (0–25 cm standing water) to assess variability in N uptake and utilization by medium and late duration rice varieties. The N rates were 0, 40, 80 and 120 kg N/ha applied as urea in four equal splits at transplanting, active tiller initiation, panicle initiation and flowering stages. The grain yield response was up to 80 kg N/ha. The optimum grain yield attainable by the efficient medium duration varieties was 4·5 t/ha. The N efficient late duration varieties produced optimum grain yield of 5·8 t/ha. The relationship for total dry matter and grain yield production between N fertilized (40, 80 and 120 kg N/ha) and non-fertilized treatments were all significant, suggesting cultivar selection under optimum N fertilized conditions. The difference in optimum yield of the medium and late duration varieties was due to the differences in the amount of N uptake and its use efficiency by the plant for grain production. There was a curvilinear relationship between grain yield and N use efficiency for grain production. The relationship between N use efficiency for grain production and N contents of leaf, stem and grain at maturity was quadratic. The optimum plant N use efficiency of medium duration varieties was 49 kg grain/kg N uptake, achieved with leaf, stem and grain N contents of 10, 8 and 14 g/kg, respectively, at maturity. For late duration varieties, the optimum plant N use efficiency was 68 kg grain/kg N uptake and it was maintained with leaf and stem N content of 4·0 g/kg each and grain N content of 9·0 g/kg at maturity. The N content in plant organs could be the selection guide used to obtain efficient rice varieties.

Castrated male black Bengal kids were supplemented daily with 0, 0·5, 1·0, 1·5 and 2·0 mg chromium (Cr3+ as chromic chloride hexahydrate) for 150 days. Metabolic stresses such as a feeding challenge, an intravenous glucose tolerance test (IVGTT) and a short-term (72 h) feed deprivation were imposed on the animals to ascertain if supplemental Cr could alleviate these stresses and whether the stress-alleviating effect could provide an explanatory basis for the performance traits of the supplemented animals. The kids were fed with a concentrate diet containing 0·197 mg Cr/kg DM. DM intake (g/kgw0·75) was lower (P=0·006) in the 0·5 and 1·5 mg groups. Feed efficiency tended (P=0·086) to improve in the Cr-supplemented kids, although a distinct dose response was absent. Basal serum T3 increased linearly (P=0·01) with increased dose of Cr although the post-prandial change did not follow any definite trend. Basal serum insulin increased (P=0·001) linearly while the post-prandial increment was higher (P=0·037) in the control group. The IVGTT indicated that the kids supplemented with 1·5 mg Cr had significantly (P<0·05) higher serum clearance rate and lower half-life for insulin. Serum Cr during the IVGTT declined (P<0·05) until 45 m after glucose infusion and then increased again (P<0·10) at 60 m in the 0·5 and 1·5 mg groups although in the rest of the experimental groups serum Cr was stable during the entire course of the IVGTT. The body weights at the beginning of the fast were higher (P=0·036) in the kids supplemented with 0·5 and 1·5 mg Cr. However, the change in body weight at the end of the 72 h fast did not vary (P>0·10) between the groups. Cr supplementation reduced (P<0·05) serum cortisol level in the supplemented animals consistently throughout the duration of the feed deprivation. Moreover, as the fast progressed serum cortisol tended to increase (P=0·059) in all the experimental groups irrespective of the level of Cr supplementation. It was concluded that inorganic Cr supplementation might appreciably increase serum T3 concentration and reduce the level of cortisol which might augment animal productivity. However, further research with a more sensitive design is required to establish the exact level of Cr supplementation for enhancing performance of livestock.

Two 2-year field trials were conducted in Nigeria to investigate the effectiveness of tomato intercropped at different times with cowpea or okra in controlling the field densities of cowpea pod-sucking bugs and okra flea beetles. The two experiments were arranged as split-plots within a randomized complete block design. The main plots were 4-week-old tomato seedlings transplanted into a field, with cowpea or okra intercropped at 0, 2 or 4 weeks after transplanting tomatoes, while the two sub-plots were cowpea or okra sole crop and tomato/cowpea or tomato/okra intercrop. The densities of the pod-sucking bugs Clavigralla tomentosicollis, Riptortus dentipes, Anoplocnemis curvipes and Nezara viridula were significantly lower (P<0·05) on cowpea intercropped at 2 weeks after transplanting tomatoes than those obtained in the sole crop. Similarly, cowpea seed damage was significantly lower (P<0·05) on cowpea planted at 2 and 4 weeks after transplanting tomatoes than in the monocrop and when cowpea and tomato were planted simultaneously. Cowpea yields were influenced by both time of intercropping and cropping system; in the intercrop, the highest yield was obtained at 2 weeks after transplanting tomatoes. In the tomato/okra intercrop, the numbers of flea beetles (Podagrica spp.) were significantly influenced (P<0·05) by cropping system alone; their density was significantly lower (P<0·05) in the intercrop than in the sole crop irrespective of time of intercropping. Similarly, damage was significantly higher (P<0·05) in the sole crop than in the intercrop while yield comparable to that of the monocrop was obtained at 2 WAT. The highest land equivalent ratio (LER) for cowpea (1·8 and 1·6) or okra (0·7 and 0·8) was obtained at 2 weeks after transplanting tomatoes in both years. Two weeks after tomato establishment appeared to be the best time to introduce either cowpea or okra into the cropping system.

In order to assess the influence of nutrient elements on the accumulation of β-N-oxalyl-L-α, β-diaminopropionic acid (β-ODAP; the probable cause of lathyrism) in Lathyrus sativus L. (grass pea), it was first examined under field conditions during the lifespan of a grass pea plant using high-performance liquid chromatography (HPLC). β-ODAP mainly accumulated in young seedlings, in developing and mature seeds and in young leaves, especially in young seedlings. In contrast, all mature leaves, roots, and stems showed a low level of β-ODAP. The β-ODAP accumulation pattern in seedlings grown in a nutrient-deficient solution was highest (3·57 mg/g) in shoots at 7 d growing in the nitrogen-deficient solution and higher compared to the control (2·31 mg/g) in zinc-, calcium-, phosphorus- and molybdenum-deficient shoots (P<0·05). The contents of β-ODAP in seedlings growing in other element-deficient solutions were similar to controls. When the content of β-ODAP in grass pea seedlings fertilized with different forms of organic nitrogen was assayed the results indicated that amino acids such as glutamine and serine, as well as nucleotide nitrogen, all significantly enhanced the accumulation of β-ODAP in young seedlings relative to controls (P<0·05). Taken together, these data suggest that β-ODAP accumulation in grass pea might be related to the level of total free nitrogenous compounds and that nitrogen and phosphate may be the crucial nutrient factors influencing β-ODAP content under field conditions. Thus, the application of appropriate nitrogen and phosphorus fertilizers to the soil could decrease the content of β-ODAP in the seeds and leaves of grass pea.

The importance of mechanistic models for ration balancing with forages is indicated and physical limitations to intake emphasized, because these limit energy and nutrient supply to cows grazing forages, especially grass. Ration-balancing models using fresh or ensiled forages to complement pasture will need to accommodate intake limitations due to rumen fill, clearance, chewing or other criteria. The potential of the Cornell Net Carbohydrate and Protein System (CNCPS) model to predict milk production from diets based on pasture and forage supplements was tested using data from two experiments. Data were obtained from studies in which pasture was complemented with contrasting silages including maize, pasture, sulla, lotus and forage mixtures, comprising 0·30–0·40 of dry matter intake (DMI). Twelve diets were used in the evaluation. DMI, liveweight (LW), days in milk, and diet composition were determined during the trials and used as inputs in the model. Across all diets, a significant relationship existed between predicted and actual values for DMI (R2=0·58), milk yield (R2=0·59) and LW change (R2=0·51), but there were still large unexplained sources of variation. No significant mean bias was observed for any of the variables, but the slope of residual differences against predicted values was significantly different from zero for milk yield, LW change and for DMI (P<0·06). The results indicate a satisfactory prediction of milk production when cows are neither gaining nor losing weight, but that a systematic bias exists probably because of the failure of the CNCPS model to account for energy and nutrient partitioning.

Cattle tuberculosis in Great Britain is out of control, rising at some 18% a year, but there is great confusion as to why cattle control measures are not working (Hancox 2004a). Culling over 10000 badgers so far in the Krebs Randomised Badger Culling Trial has had no effect, despite repeated calls for mass culls by farmers and vets (Hancox 2004b). Badgers are blamed for this crisis because it is claimed cattle-to-cattle transmission is unimportant, and badgers with TB are found after repeat breakdowns in herds supposedly free of TB after negative tests.