Selection for food conversion in broilers: Direct and correlated responses to selection for body‐weight gain,food consumption and food conversion ratio

1. Direct and correlated responses were determined after five generations in four lines of chickens selected either for increased body‐weight gain (line W), for increased food consumption (line F), for decreased food conversion ratio (line E), or at random (line C).

2. Realised heritability estimates calculated after five generations of selection were : 0–37 + 0.04 for weight gain (WG); 0.44 + 0.05 for food consumption (FC); 0.21 + 0.04 for food conversion ratio (FCR).

3. Realised genetic correlation estimates were: WG and FC, +0.71 ±006; WG and FCR, ‐0.40±0.09; FC and FCR, +0.27 + 0.09.

4. Zero‐generation heritability and genetic correlation estimates were greater than the realised estimates, and sex linkage appeared to be important in the expression of all three traits.

5. The genetic correlation between FC and FCR was asymmetrical with considerable positive response in FCR in line F (r_g = +0.79) but negligible response in FC in line E (r_g = —0.01).

6. There was an apparent plateau in response in FCR in line E from the third to the fifth selected generations.     

On predicting the presence of birds in Eucalyptus forest types

We examine the relationship between the number of bird species and environment within 500 000 ha of eucalypt forests in south-eastern New South Wales, Australia. Birds were surveyed at 39 sites within 31 eucalypt communities, which were, in turn, scored by altitude, temperature, rainfall, basal areas of trees and levels of the nutrients nitrogen, phosphorus, potassium and magnesium in the eucalypt foliage.

Ninety bird species were recorded. Numbers per site, averaged over the whole sample period, ranged between 20 and 38 over all surveys, 24 and 42 in ‘summer’ (October to March) when migrant species were present, and 13 and 38 in ‘winter’ (April to September). A forward stepwise Poisson regression model was used to fit bird species richness to the environmental variables. Over all surveys and in ‘summer’, foliar magnesium and tree basal area (including the basal area of dead trees) were significantly (positive) correlated with the number of bird species. In ‘winter’ the correlations were with altitude and temperature (both negative), presumably the result of emigration of species that avoid cold weather, and tree basal area (positive).

The positive association of number of species over all surveys and in ‘summer’ with tree basal area, including dead trees, and foliar magnesium may index the level of forest maturity and productivity.

Forest management directed solely to timber production reduces the basal area and the number of dead trees and may thereby reduce bird species richness permanently.

A methodology is offered, based on the relationship between the physical environment and the more productive eucalypt communities, for determining forest areas containing the most species of birds.     

Application of a numerical algorithm to the selection of reserves in semi-arid New South Wales

An iterative analysis was used to identify the number and area of pastoral properties needed to contain the full range of natural environments (land systems) in part of western New South Wales. A minimum of 32 properties (3·1% of total number) and 7980 km² (5·7% of total area) was required to represent every land system at least once. Full representation required a greater overall number and area when the analysis began with properties already acquired for conservation. Excluding land systems atypical of the study area did not greatly reduce the number and area of properties required. Complete representation of land systems in each geographical subdivision in which they occur required a much greater overall number and area of properties than when the analysis was run for the study area as a whole. The algorithm used in this study produced very similar results to other iterative analyses applied to reserve selection in Australia.     

Outbreaks of proliferative haemorrhagic enteropathy on two pig farms

SUMMARY Clinical signs of proliferative haemorrhagic enteropathy (PHE) including anaemia, dysentery and sudden death were observed in finisher pigs and young breeding stock on 2 farms. On farm A, PHE occurred 12 months after repopulation of the farm. Other outbreaks of PHE occurred after the withdrawal of therapeutic concentrations of in-feed antibacterial agents (farm A), or after monensin sodium (100 g/t) replaced olaquindox (100 g/t) in feed (farm B). The outbreaks, the possible sources of contamination and the role of antibacterial feed additives in the treatment and control of PHE are described.     

Lungworm: (Dictyocaulus arnfieldi) infection in donkeys.

The clinical, parasitological and pathological findings in a group of six donkeys naturally infected with D arnfieldi larvae are described. One animal had to be sacrificed at an early date because it developed pneumonia. The remaining five were unthrifty, showed mild clinical respiratory signs and had heavy strongyle infections. They had varying numbers of adult worms in the airways of the lungs and eggs were found coiled up in the smaller bronchi where they had apparently lead to an obstruction to airflow in that segment. The most striking gross pathological changes were circular discrete areas of over-inflation surrounding such bronchi. Histologically the infected bronchi exhibited a marked bronchiolitis with goblet cell hyperplasia and a mainly lymphoid inflammatory infiltrate. These areas also showed a localised bronchiolitus and overinflated alveolar tissue although true emphysema was not present. It is postulated that the parasite is well-adapted to its host and is able to survive for long periods within the lung without causing a debilitating amount of damage to the host. The immunological aspects of the infection are discussed briefly.     

Advances and Perspectives in the Biological Control of Greenhouse Pests with Special Reference to Colombia

This paper analyses the state of the art of biological control of greenhouse pests with special reference to Colombia, one of the world's largest producers of cut flowers. After a discussion of the use and impacts of selected natural enemies on a variety of arthropod pests in greenhouses, suggestions on how to enhance the effectiveness of inundative release strategies further to achieve successful biological control of key pests are provided.     

Effects of yard weaning and training on the behavioural adaptation of cattle to a feedlot

Two experiments were conducted to determine the effect of weaning in small yards, with or without a feed bunk training procedure, on the subsequent behaviour and performance of Bos taurus steers in a feedlot. A reduction in the incidence of bovine respiratory disease (BRD) was the primary objective. In each experiment, about 200 male beef calves (Angus × Hereford and Hereford) were separated from their mothers at 7–9 months of age and allocated to one of three matched weaning treatment groups. The treatments were (1) yard weaning with hay or silage, (2) yard weaning with hay or silage plus a novel handling procedure to train the animals to be able to find a grain ration in a trough, and (3) paddock weaning without supplement or handling according to common industry practice in southeastern Australia. Paddock weaning is the practice of abrupt separation of cows and calves followed by return to separate pasture paddocks, whereas yard weaning involves abrupt separation but the calves remain in the yards for several days. Experimental vaccines against the major BRD pathogens were given to half of each group 1–2 months prior to entry into a commercial feedlot. The yard weaned and yard trained cattle had a significantly greater weight gain in the first month and over the 90-day feeding period than the paddock weaned control groups. There was no difference between the groups in pre-feedlot weight gain. The yard trained groups showed greater feeding activity during the first few days in the feedlot, but were not significantly different in weight gain from yard weaned. The vaccination treatment also significantly improved the weight gain in the first month and over 80 days. The combination of yard weaning and vaccination produced the highest weight gains overall. There was consistently less morbidity in the yard weaned groups compared to paddock weaned controls. The morbidity in yard trained groups was intermediate between these two. Weaning in small yards and the appropriate use of effective BRD vaccines 1–2 months before feedlot entry are recommended for B. taurus feeder steers in southeastern Australia to minimise sickness and improve productivity in the feedlot. Associated benefits are reduced risks of antibiotic residues and of animal welfare problems.