Crossbreeding effects on reproductive traits in two strains of duck (Anas platyrhynchos): Brown Tsaiya and Pekin

1. The reproductive performances of 211 domestic duck females (Anas platyrhynchos) from the pure breeds Brown Tsaiya (Ts) and Pekin (Pk) and their two reciprocal crossbreds were analysed.

2. Differences in the 4 genotypes, additive direct and maternal crossbreeding effects and heterosis were estimated on the following traits: age at first egg, egg production to the ages of 30, 35, 40 and 52 weeks of age, egg weight at 30 weeks of age, and (egg) fertility by artificial insemination with Muscovy drakes’ pooled semen.

3. Egg production up to 52 weeks of age was higher in Ts than in Pk (respectively 214 ± 7 and 150 ± 8 eggs), but not statistically different from that of the reciprocal crossbreds. The ratio of settable eggs to total eggs was nearly 90%, without any difference between genotypes.

4. Average egg weight at the age of 30 weeks was 75 ± 0.9 g for Pk, which was higher than the corresponding values for Ts (62 ± 0.8 g), but not significantly different from the crossbreds.

5. An effect of genotype was found on egg fertility: the Pk strain exhibited the lowest value, 71.3 ±3.1% compared with 75.9 ±2.1% for Ts, 80.6 ± 2.6% for Ts × Pk and 74.6 ± 1.9% for Pk × Ts.

6. Crossbreeding genetic variables showed favourable direct genetic effects for egg production and (egg) fertility in Ts, while Pk had favourable direct genetic effects on egg weight. The Pk genotype had a favourable maternal effect on fertility. Direct heterosis was 34% and 10% for egg production up to 30 and 52 weeks of age respectively, 8.8% for egg weight and 5.4% for (egg) fertility.

7. Crossing Ts with Pk seems profitable for the production of mule ducklings.     

Changes in blood and spleen lymphocyte populations following antigen challenge in immature male chickens

1. The effects of antigen (Ag) injection on the distribution of lymphocyte populations of Cornell K‐strain male chickens were studied.

2. Two experiments were conducted. In the first, chickens were injected with Brucella abortus (BA), a purported T‐independent antigen. In the second, chickens were injected with sheep red blood cells (SRBC), a T‐dependent antigen. Peripheral blood lymphocytes (PBL) and spleen lymphocytes isolated at 0, 3, 6, 9, 12 and 24 h following Ag injection were stained with monoclonal antibodies (mAb) detecting B‐lymphocytes, CD4⁺ and CD8⁺ cells.

3. B‐lymphocytes in the blood or spleen showed no significant changes following either BA or SRBC injection. In contrast, CD4⁺ cells were decreased in the blood and increased in the spleen following BA and SRBC injections. CD8⁺ cells were decreased in both blood and spleen following BA injection but were unchanged in either blood or the spleen following SR8C injection.

4. These results indicate that there is a change in both spleen and circulating lymphocyte populations, especially T‐helper cells, following Ag injection. T‐helper cells are apparently the primary population involved in the initiation of humoral immunity.     

Soluble matrix of hen's eggshell extracts changes in vitro the rate of calcium carbonate precipitation and crystal morphology

1. Extra and intramineral eggshell matrix proteins were solubilised before and after demineralisation by sequential extractions using guanidine hydrochloride and EDTA.

2. The intramineral electrophoretic profile of SDS‐PAGE showed the presence of 80, 66, 43, 36 and 15 kDa bands with a predominance of a 17 kDa band. In the extramineral part, the major protein was the 15 kDa band.

3. The introduction of intramineral extract to a metastable solution of calcium carbonate delayed the rate of crystal growth. The delay in the rate of precipitation was elicited by a single fraction (MW 50–80 kDa), isolated by gel filtration chromatography, of eggshell extracts. Extramineral extracts had no effect.

4. Addition in vitro of intramineral eggshell extracts modified the morphology of calcite; the crystals aggregated and showed irregular surfaces.

5. These observations suggest that constituents of the eggshell matrix are involved in the control of calcite growth and crytallographic structure of the hen's eggshell.     

Artificial increase of eggshell conductance improves hatchability of early laid goose eggs

1. The purpose of this work was to test the possibility of increasing the hatchability of goose eggs with low mass specific eggshell gas conductance (G_sp), by drilling holes through the eggshell into the air cell, and thus solving both the low water loss rate and low oxygen availability problems.

2. A linear relationship was found between the area of a hole drilled and the apparent increase in eggshell gas conductance (G). Drilling more than one hole increased apparent G 3.6 times more than one hole only, of the same total area.

3. Hole‐drilling did not increase egg contamination. The drilling of a 5 mm² hole on day 17 of incubation increased hatchability both in laboratory tests and in commercial hatcheries (6.1% and 10.5% respectively).

4. Drilling holes on days 15 to 22 of incubation increased hatchability when the predicted mean water loss was lower than 14%. Drilling on day 25 did not have a significant effect, and drilling on day 11 of incubation was too early.

5. Drilling a hole into the aircell (during the second half of incubation) may increase hatchability of low conductance eggs, although oxygen pressure under the eggshell should then be checked in order to evaluate oxygen availability to the embryo.     

Prevalence and duration of insensibility following electrical stunning in calves

Sixty-one calves were electrically stunned with 100-250 V currents (103-1806 mA) and the prevalence and duration of insensibility was assessed from their physical behaviour, the presence of epileptiform activity in their electrocorticograms, and the absence of visual evoked responses in their electrocorticograms. A current applied at 100 V across the head for 3 s failed to induce insensibility in all cases. Currents at 150-250 V induced insensibility in all calves and the shortest duration of insensibility was 44 s. It is recommended that a 150-200 V current would be appropriate for commercial use.     

The effectiveness of benzimidazole-levamisole combination drenches in the presence of resistance to both benzimidazole and levamisole anthelmintics in New Zealand sheep

Examination of 25 cases of multiple benzimidazole and levamisole resistance, identified in sheep by faecal egg count reduction testing at the Batchelar, Lincoln and Invermay Animal Health Laboratories, showed that benzimidazole-levamisole combinations provided effective control in eight (47%) of 17 cases in which they were tested. Overall, the use of combination drenches resulted in average improvements in faecal egg count reductions of 25.6% (p<0.01) and 23.2% (p<0.05), respectively, over those achieved by the use of benzimidazole or levamisole drenches alone. The results suggest that instances of multiple resistance in which combination drenches might be effective are unlikely to be predictable either by identification of the parasites involved, or from the levels of benzimidazole or levamisole resistance present.     

Book reviews

Amino Acids in Farm Animal Nutrition. Edited by J. P. F. D'Mello. 1994. 417 pp. £55.00 Wallingford, Oxon, CAB International. ISBN 0 85198 8814

Avian Hematology and Cytology. Terry W. Campbell. 1995. 104 pp. Illustrated. £48.00. Ames, Iowa State University Press. ISBN 0 8138 2970 4.     

Individual variation in prelaying behaviour and the incidence of floor eggs

1. Floor eggs are a problem in non‐cage systems for laying hens, as they require secondary egg collecting. Failure to lay in a well‐defined nest site may also be a welfare problem for the hens, but only if their nesting motivation has been thwarted.

2. We investigated the relationships between a hen's prelaying behaviour and its tendency to lay on the floor by recording the behaviour of 20 hens housed individually in wire cages with single littered nest boxes.

3. Most floor eggs (80%) were laid by the same 6 hens. These 6 “floor‐layers” performed more nest seeking behaviour, less nest‐building behaviour and less sitting prior to oviposition than the 14 hens that consistently laid in nest boxes.

4. The incidence of floor eggs declined with age. Both nest and floor laying hens performed less nest seeking behaviour with age. Floor layers, however, increased their performance of nesting behaviour, whilst nest layers performed less nesting behaviour with age.

5. Floor laying hens behaved as if they found the nest box less attractive than nest‐laying hens; perhaps because they had lower nesting motivation, or perhaps because their nesting motivation was as high, but they less readily perceived the nest box as an appropriate nest site.     

The diagnosis of Neospora abortions in cattle

An indirect immunofluorescent antibody test (IFAT) and an enzyme-linked immunosorbent assay (ELISA) for specific anti-Neospora antibodies in bovine sera and foetal fluids were compared with histological examination results on aborted foetal material. The agreement between serological and histological examination results was poor, while the two serological tests showed a high degree of agreement. Serological testing of diagnostic serum samples and foetal fluids suggests that the prevalence of anti-Neospora antibodies in cattle which recently aborted is around 40%, in line with previous estimates of the number of abortions in dairy cattle caused by Neospora sp. A sero-epidemiological approach to the diagnosis of Neospora abortions in cattle may be suggested from these data.