L‐aspartic acid and urea supplementation of low‐protein layer diets1

1. Urea supplementation of low‐protein (125 g/kg) conventional‐type diets for layers, whether containing fish meal or not, did not appear advantageous.

2. Supplementation of the low‐protein diet with aspartic acid did not affect egg production rate or efficiency.

3. Soyabean meal supplementation of the low‐protein diet increased egg weight significantly whereas aspartic acid did not.     

Factors affecting the variability in cracked and dirty eggs and egg production profitability on an integrated poultry operation

1. A number of factors causing variability in the percentages of cracked, and dirty eggs and weekly standard margin (WSM) of returns from eggs over production costs were examined on an integrated commercial poultry plant in Scotland.

2. As the bird aged, the percentage of cracked eggs increased (P <0.01) and the percentage of grade A eggs and WSM decreased (P <0.01). Cracks in dirty eggs (10.1%) were more than double those in all eggs laid (4.9%).

3. Seasonal effects on percentage cracked eggs and percentage grade A eggs were one‐third the magnitude of those due to age but were significant (P <0.05).

4. Variability in percentage cracked eggs, dirty eggs and WSM accounted for by the factors measured, were 72, 64 and 92% respectively.

5. The variability in WSM was significantly affected by percentage lay, food consumption and age but not by percentage cracked eggs, originally dirty and grade A eggs.

6. Flock management and climate inside the laying house each increased the amount of variability accounted for in the percentage cracked eggs and dirty eggs by at least 10%.     

On estimating non‐additive genetic parameters in chickens 1

1. Several economically important traits in two Leghorn populations (over 9000 birds) were examined for additive and non‐additive components of genetic variance and sex‐linked effects. Data were analysed by two different statistical models based on least‐squares procedures.

2. Six different covariances were first calculated between relatives; i.e., full‐sibs, 3/4‐sisters, half‐sisters, dam‐daughters, grandam‐granddaughters and aunt‐nieces.

3. From the covariances, weighted least‐squares equations were used to obtain estimates of variance components for additive genetic, dominance, maternal and sex‐linkage effects.

4. The estimates of non‐additive components were highly variable but generally small compared with the additive genetic estimates.

5. In general this study suggests that for most traits, with the possible exception of rate of egg production, there is relatively little non‐additive genetic variation.

6. The consequences of possible negative correlations between additive effects and maternal effects are considered as they might apply to egg production in poultry.     

Broiler growth and feeding behaviour in three different lighting regimes

1. Female broiler chicks reared in a 12‐h photoperiod which included a simulated “dawn” and “dusk” grew slightly faster than those reared in a 12‐h photoperiod of uniform light and others kept in continuous light.

2. This was apparently because the chicks subjected to dawn and dusk ate more food than those subjected to 12‐h uniform light and converted food more efficiently than those in continuous light.     

Ultrastructural changes in leaf and needle segments treated with herbicides containing picloram

The herbicide Tordon 50D (picloram+2,4-D) affected the integrity of the nucleus and cell membranes in Pinus radiata needle segments and caused the swelling of internal chloro plast membranes and the eventual disintegration of the chloroplasts. Tordon 22K (picloram) only affected chloro plast structure. Both herbicides had similar adverse effects on cell membranes and chloroplasts of Eucalyptus viminalis.     

The effect of soil aggregate size and water content on herbicide concentration in soil water

Suspensions of wettable powders of metribuzin and simazine were sprayed onto samples of two soils of two particle size grades, > 2.5 mm and <0.5 mm. The soils were either air-dry or at a water content of 12%. After either 1 h or 1 week, water was added to give a soil to water ratio of 1:1. Samples of solution were analysed after 1, 24 and 48 h. With metribuzin the intial concentration for both soils after wetting was greater from the >2.5 mm samples than the <0.5 mm samples, following application to dry soil, but by 48 h the differences were negligible. With simazine WRO soil did not show this effect at all and with Kirton soil only small differences were seen. If the soil was wet at the time of application, particle size had no effect except with simazine in Kirton soil. Generally metribuzin concentrations were higher after application to wet than to dry soils for at least 24 h after wetting whereas simazine concentrations were higher from initially dry soils and the differences had virtually disappeared 24 h after wetting. With the WRO soil herbicide concentrations in soil water were higher if the soil was wetted 1 h after spraying than if left for 1 week but the differences rarely persisted for 48 h. No such trend was observed with Kirton soil. It is concluded that the differences observed in these experiments could be responsible for variations in the performance of soil-applied herbicides.     

The selectivity of methabenzthiazuron between barley, perennial ryegrass and Poa trivialis

In field experiments methabenzthiazuron at 1.1 kg ai/ha applied pre-emergence gave good control of Poa trivialis L. in perennial ryegrass S23 which was undersown in spring barley (Zephyr); no significant damage to barley or perennial ryegrass resulted from 2.2 kg ai/ha. However this dose applied when barley had three to four leaves decreased the subsequent barley yield. In pot experiments in the glasshouse methabenzthiazuron was active mainly due to uptake through the soil. Much greater damage to barley and perennial ryegrass resulted when herbicide-treated soil was placed below seed level than above the seed. The difference was less marked with P. trivialis. The latter started to develop secondary roots near the soil surface earlier than either perennial ryegrass or spring barley.     

Weed competition in spring-planted strawberries

Annual weeds germinating after planting strawberry (Fragaria chiloensis (L.) Duch. cv. Cambridge Favourite) in late March had no effect on crop growth if removed by late May. Dense weed cover thereafter severely inhibited stolon growth, virtually eliminating it if allowed to remain beyond mid-August. Shading by weeds inhibited leaf production and caused etiolation of existing leaves. New leaves appeared shortly after weed removal and few plants died unless weed cover persisted for most of the growing season. Further weed germination was allowed on some plots. Although not removed until late autumn, these weeds only had adverse effects on crop growth where initial weeding had occurred before mid-June. In one experiment, delaying weed removal until 6 July, 31 August or 2 November in the first year reduced fruit yield in the second (weed-free) year by 34%, 54% and 67% respectively. In a later experiment, competition from weeds until July or later in the first growing season gave fruit yields similar to those in the first experiment, but totally weed-free plots and those kept clean after weeding in mid-June produced less fruit than plots which remained weedy between mid-June and mid-August. It is suggested that competition from uncontrolled stolon growth in this experiment severely inhibited crown and hence truss production on plots which did not suffer weed competition. Unless left untouched until early September, weeds had less adverse effect on truss production than the stolons which they displaced. The results are interpreted in relation to improving the efficiency of weed control techniques.     

Persistence and movement of ethofumesate in soil*

Persistence of ethofumesate [(±)2-ethoxy-2.3-dihydro-3,3-dimethylbenzofuran-5-yl-methansulphonate] in soil was associated with soil temperature. Ethofumesate applied at 4.5 kg/ha in November persisted about twice as long in soil as that applied the following March. In another field study, 88–91% of the herbicide had dissipated after 24 weeks in sandy loam soil, compared to 72–77% in loam soil when it was applied at rates of 2.2, 3.4, 4.5, and 9.0 kg/ha. The rate of degradation was independent of the initial rate of chemical applied. The time required for 50% of the herbicide to dissipate in sandy loam and loam soils was 7.7 and 12.6 weeks, respectively. The movement of ethofumesate in these two soils over a 24-weeks sampling period was confined mainly to the upper 7.5 cm of the soil profile.     

Structure-activity relationships of 1,2,3-benzothiadiazoles as synergists for carbaryl against the house fly (Musca domestica)

Fifty six 1,2,3-benzothiadiazoles and related compounds were evaluated as carbaryl synergists against the house fly (Musca domestica). Many of these were excellent synergists, the most active being those containing various combinations of halogen, alkyl, or alkoxy substituents in the 5- and/or 6-positions of the ring.Regression analysis on the data from 14 compounds for which substituents constants were available established that synergistic activity can be satisfactorily described by equations in terms of the hydrophobic bonding constant (π) and the homolytic free radical constant (σ ·).The results with compounds related to the 1,2,3-benzothiadiazoles suggest that synergistic activity is associated primarily with the diazosulfide moiety.