Bovine spongiform encephalopathy: epidemiological features 1985 to 1990.

Following the identification of bovine spongiform encephalopathy (BSE) in the British cattle population in 1986 epidemiological studies were launched. This paper provides an updated account of the epidemiological features of BSE from 1985, when the first cases, based on clinical histories, occurred, until 1990. The number of cases up to December 1989 represents an annual incidence of 3.9 confirmed cases per 1000 adult animals in Great Britain. Many more dairy herds were affected than beef suckler herds, a difference attributable to the difference in feeding practices between the two herd types. The geographical variation in incidence previously described has persisted with the highest incidence in the south and east of England. Other features of the epidemiology, including the low within-herd incidence, remained unaltered from the earlier findings. The results support the previously suggested hypothesis that the outbreak of BSE was due to the sudden exposure of the cattle population to a scrapie-like agent in 1981/82. There was no evidence of direct transmission between cattle during the period considered.     

Behaviour of laying hens in a deep litter house

1. Flocks of medium hybrid laying hens were housed in a modified deep litter system; the house was divided into 2, 3 and 4 pens in three successive years. Flock size was 300 or 370 and stocking density varied from 3.4 to 10.7 birds/m2. Higher densities used were above those recommended by the Ministry of Agriculture, Fisheries and Food (MAFF). 2. A random sample of 100 birds was identified with individual tags in each of the 9 flocks; regular observations using a scanning technique were made in each laying cycle to determine bird location and behaviour. 3. In all flocks the use of area by some individuals was uneven, that is, they were sighted in certain areas significantly more often than would have been expected by chance. The proportion of such individuals varied between flocks from 35 to 65%. Overall, birds spent more time on the slatted area than would have been expected from the area that it occupied. 4. A wide variety of different behaviour patterns was observed both on litter and on slats, but with foraging occurring more on litter and feeding more on slats. 5. Movement appeared to be constrained by crowding, because time spent in locomotion decreased in approximately linear fashion with increased stocking density. This provides support for MAFF recommendations of limits on stocking density in deep litter houses.     

Ovarian follicular characteristics, embryo recovery, and embryo viability in heifers fed high-fat diets and treated with follicle-stimulating hormone.

Postpubertal beef heifers (n = 55) were used to examine the effects of high-fat diets, independently of energy intake, on nonesterified fatty acid and lipoprotein metabolic patterns, ovarian follicular dynamics, and embryo recovery/viability after FSH superstimulation. High-lipid (HL) diets (5.4% added fat) increased (P < .01) serum concentrations of cholesterol, but not of nonesterified fatty acids, during the 35-d period before FSH treatment. Development of medium-sized (5 to 9.9 mm) follicles was enhanced (P < .05) during this period in heifers fed the HL diet. The HL diet increased total cholesterol (P < .05) and progesterone (P = .14) concentrations in follicular fluid obtained at ovariectomy (n = 10) 60 h after the onset of FSH treatment, but neither estradiol-17 beta nor androstenedione was affected. Granulosa cells recovered from FSH-induced, estrogen-active follicles in heifers fed the HL diet produced greater quantities of progesterone (P = .06) and less estradiol-17 beta (P < .05) in vitro than did granulosa cells from heifers fed the normal lipid diet. Dietary treatment did not influence FSH-stimulated recruitment of medium and large follicles, number of ovulations, embryo recovery, or embryo viability. Data suggest that increments in dietary fat intake can alter specific aspects of ovarian steroidogenic potential and can increase the population of medium-sized follicles theoretically available for maturation and harvest during the estrous cycle. However, conditions that limited the latter process in the current experiment are not understood and require further investigation.     

Experimental infection of pregnant gilts with swine hepatitis E virus

To determine the effect of swine hepatitis E virus (HEV) infection on pregnant gilts, their fetuses, and offspring, 12 gilts were intravenously inoculated with swine HEV. Six gilts, who were not inoculated, served as controls. All inoculated gilts became actively infected and shed HEV in feces, but vertical transmission was not detected in the fetuses. There was no evidence of clinical disease in the gilts or their offspring. Mild multifocal lymphohistiocytic hepatitis was observed in 4 of 12 inoculated gilts. There was no significant effect of swine HEV on fetal size, fetal viability, or offspring birth weight or weight gain. The offspring acquired anti-HEV colostral antibodies but remained seronegative after the antibodies waned by 71 days of age. Swine HEV infection induced subclinical hepatitis in pregnant gilts, but had no effect on the gilts' reproductive performance, or the fetuses or offspring. Fulminant hepatitis associated with HEV infection was not reproduced in gilts.     

Choice of social conditions by laying hens

1. To test the preferences of hens for particular social conditions when laying, they were provided with choices of nest‐sites varying in seclusion. Three experimental conditions were used.

2. In Experiment 1, nest‐site selection by members of a group of light hybrids was studied in a complex pen‐system. Eggs were clumped in distribution ; only one individual laid in the most secluded part of the system.

3. Experiment 2 provided light hybrids with an extensive outdoor area, but similarly clumped laying was observed; there was no indication that hens attempted to find concealment for nesting.

4. In Experiment 3, hens from a group of light hybrids just coming into lay and from a group of mature medium hybrids were tested singly, in an area that included a cage containing some of their flockmates. Most subjects from both groups laid near the other birds rather than in isolation.

5. In semi‐intensive conditions, the majority of hens are apparently gregarious rather than solitary in their nesting behaviour.     

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.     

Nesting and dust bathing by hens in cages: Matching and mis‐matching between behaviour and environment

1. Medium hybrid hens were housed as groups of 4 at 18 weeks of age in cages of 4 different types: control battery cages allowing 675 cm2/bird; similar cages with a rear‐mounted dust bath, 290×345×240 mm, containing sand (D); cages with a rear‐mounted nest box of the same size, containing wood shavings (N); cages with both (DN). In half the experimental cages access to nests was restricted to the morning and access to baths was restricted to the afternoon, by automatic sliding doors.

2. During the first 24 weeks of lay about 95% of eggs were laid in nest boxes in treatments N and DN. Slightly fewer were laid in boxes where doors were present. Over 90% were laid in dust baths in D cages without doors and 67% with doors, which birds learned to open. Prelaying behaviour was least disturbed in nest boxes, most disturbed on the floor and intermediate in dust baths.

3. Fully developed dust bathing occurred in D and DN as bouts lasting 5 to 10 minutes; its incidence, surprisingly, was greater when doors were present and greater still when nest boxes were present, even though it was not performed in them. It was also performed by some hens in nest boxes in N (without doors). In N with doors and in control cages, dust bathing occurred on the bare floor in truncated form, as serial bouts each lasting only about 10 s. This truncated dust bathing was also occasionally observed in D and DN.

4. Plumage, foot and claw damage were less in hens from modified cages than from controls. Egg production was very good in all treatments but more eggs from control cages were downgraded because they were dirty or cracked.

5. When a choice was available birds generally partitioned their behaviour appropriately between nest box and dust bath. In N and DN virtually all prelaying and nesting behaviour took place in the nest boxes. Matching between dust bathing and the environment was less close; the reasons for its relatively low incidence and occurrence in truncated form outside dust baths remain to be established.     

The Edinburgh modified gage for laying hens

1. Behaviour, production and welfare of ISA Brown medium hybrids were assessed in 2 trials (each from 20 to 44 weeks of age) of a novel design of cage for laying hens: the Edinburgh Modified Cage (EMC).

2. The EMC was 600 mm wide, 450 mm deep and 450 mm high at the rear; it had a softwood perch and at one side a 250 mm wide nest box (containing litter or artificial turf) with a dust bath direcdy above. It housed 4 birds and provided 675 cm^2/bird in the main cage with an additional 281 cm² /bird in the nest box. The nest box and dust bath had automatically controlled doors which were closed at night. There were 18 EMC; in the first trial these were compared with 6 control cages with perch but without next box or dust bath.

3. Hens spent 32 to 37% of day time on the perch, 5 to 7% in the dust bath and 5 to 6% in the nest. At night 92 to 98% roosted on the perch.

4. Initially only 55 to 70% of eggs were laid in the nest box partly because some eggs were laid before dawn. Once the door was retimed to open 3h before lights‐on the proportion rose to 91 to 96%. Very few eggs were laid in the dust bath. Pre‐laying behaviour lasted longer in treatments with nest boxes (55 to 76min) than in control cages (48min); disturbance was slight in all treatments, but lowest in control cages.

5. Dust baths were well used, with on average 61% of hens dust bathing during a 3‐h afternoon observation period compared with only 17% in control cages. Two birds could use the dust bath simultaneously.

6. It was concluded that although a number of minor design features still required attention the EMC has potential to reduce the disadvantages of conventional cages for welfare while retaining their advantages and has possible commercial application.     

Perch length in cages for medium hybrid laying hens

1. ISA Brown hens were housed as groups of 4 from 18 to 72 weeks in 24 cages 450 mm deep, each with a softwood perch of rectangular cross‐section fitted across the rear. There were 4 treatments, each with 6 cages: cage widths and perch lengths were 480, 520, 560 or 600 mm.

2. Daytime perching did not differ significantly between the treatments. At night, over the whole year, 81% of birds in the 480 mm cages and 86% in the 520 mm cages roosted on the perch. This figure reached about 95% in the 560 and 600 mm cages, significantly more at most ages than in the 480 mm cages.

3. Feather damage was slightly less, but claw problems slightly more, in the 2 wider treatments than in the 2 narrower treatments. Birds in the wider cages were calmer when approached or handled by humans than those in the narrower cages. This may have been associated with variation in space allowance between the treatments.

4. There was a trend for lower production in the 480 mm cages than in the other treatments which may have been associated with the reduced feeding space in this treatment. There were few other treatment differences in production traits.

5. The balance of the evidence from this study is that when perches are provided in laying cages for medium weight hybrids, 140 mm of perch space per hen is adequate. For the amelioration of a number of the welfare problems of conventional cages, provision of perches should be combined with other modifications.