Flow routes of electric currents in domestic hens during pre‐slaughter stunning

1. For a bird to be adequately stunned, sufficient electric current needs to reach the brain in order to induce an epileptic seizure. Methods are presented for determining the percentage of the stunning current which reaches the brain.

2. A transverse section of the thorax was examined and tissues including epithelium, fat, muscle, liver, keelbone and heart, were tested for the percentage of current flowing through each tissue.

3. It was found that the proportion reaching the brain varied from bird to bird whereas, with the exception of a slight variation in the proportion reaching the heart, that flowing through the other tissues located in the thorax was similar in all the birds tested.

4. The variability in current reaching the brain and to some extent the heart may determine whether a bird is stunned, inadequately stunned or killed after having entered a water‐bath stunner.     

Effect of selected dietary antioxidants on fatty liver‐haemorrhagic syndrome in laying hens

1. Single comb White Leghorn hens of an inbred line highly susceptible to fatty liver haemorrhagic syndrome (FLHS) were fed supplemented dietary ascorbic acid (200 mg/kg), α‐tocopherol (75 mg/kg), or L‐cysteine (3 g/kg, and 6 g/kg) for 28 d in order to evaluate the potential therapeutic effect of these compounds against the disease.

2. Supplementation of ascorbic acid, α‐tocopherol, or a low level of L‐cysteine (3 g/kg) did not significantly affect any of the hepatic variables evaluated. Hepatic glutathione was not increased by the supplementation of dietary L‐cysteine.

3. L‐cysteine supplemented at a level of 6 g/kg decreased hepatic dry matter and fat contents without affecting the hepatic malondialdehyde or the liver haemorrhagic score.

4. Because one of the predisposing factors of FLHS is a high hepatic fat content it was concluded that dietary supplementation of L‐cysteine (6 g/kg) may be useful in the prevention of the disease.     

Individual and combined effects of t‐2 toxin and das in laying hens

1. The individual and combined effects of T‐2 toxin and 4,15‐diacetoxyscirpenol (DAS) on laying hens were investigated in an experiment consisting of a 2 X 2 completely randomised factorial design with dietary concentrations of 0 and 2 mg/kg T‐2 toxin and 0 and 2 mg/kg DAS.

2. Individually, T‐2 toxin and DAS induced oral lesions in half of the hens and decreased significantly egg production and food intake.

3. The effects of T‐2 toxin and DAS were additive for reduced food consumption and incidence of oral lesions. However, a synergism for reduced egg production was observed during the last experimental period.

4. No effects on body weight were observed during this study. Mild changes in selected plasma enzymes activities and no change in liver malondialde‐hyde content were detected.

5. The combination of T‐2 toxin and DAS was more toxic than the single mycotoxins, for some parameters, and therefore, may pose a greater economic threat to the poultry industry than either of the toxins individually.     

Rapeseed meal and egg tainting: in vivo metabolism and excretion of 14g‐trimethylamine by tainter and non‐tainter hens

1. From their abilities to produce tainted eggs when receiving dietary rapeseed meal (RSM) Shaver 585 hens, Ross 1 broiler breeder hens and Shaver 579 hens were identified as tainters or non‐tainters.

2. There was no significant difference in the mean renal clearances of ¹⁴C between six tainter and six non‐tainter shaver 585 hens infused with ¹⁴C‐trimethylamine (TMA).

3. When increasing concentrations of TMA were infused into five tainter and four non‐tainter broiler breeder hens receiving dietary RSM, at the highest infusion rate tainter hens excreted a larger proportion (95%) of ¹⁴C as unchanged TMA than did non‐tainter hens (76%). Eight weeks after removal of RSM from the diet this difference decreased (87 and 76% respectively).

4. Two tainter and five non‐tainter Shaver 579 hens receiving dietary RSM excreted 96 and 70%, respectively, of the infused ¹⁴C‐TMA unchanged.     

Plumage loss in medium‐bodied hybrid hens: The effect of beak trimming and cage design

1. Plumage loss was assessed by visual scoring in 288, 78‐week‐old hens, housed as groups of four in battery cages, which differed in the design of the cage front and the position of the nipple drinkers.

2. Half the hens had undergone beak trimming at 18 weeks, but in many cases regrowth had occurred.

3. Plumage damage and loss was significantly reduced in beak‐trimmed birds compared with birds with normal beaks. Tier and cage design had no effect.

4. This finding supports the idea that feather pecking is the important factor in causing plumage damage, rather than abrasion.

5. A comparison between 64 birds in which beak regrowth had occurred, and 64 in which it remained truncated, showed that both groups had similar plumage scores.

6. It appears to be the beak‐trimming procedure which is important; subsequent regrowth being irrelevant.     

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.     

Ovarian morphology and rates of ovarian follicular development in laying broiler breeders and commercial egg‐producing hens

1. Ovaries from a light‐bodied egg laying strain and a broiler breeder strain were compared at 26 and 82 weeks of age.

2. The rate of lay in both strains was lower in the older hens. The 82‐week‐old hens were subdivided into good and poor layers: the poor layers produced eggs at about half the rate of the good layers.

3. The yellow‐yolky ovarian follicles in both strains were smaller, more numerous and more closely ranked in hierarchies in 26‐week‐old hens than in 82‐week‐old hens.

4. No marked differences were seen between the strains at 26 or 82 weeks of age in the sizes, numbers or hierarchical arrangements of yellow‐yolky ovarian follicles.

5. The ovaries from 82‐week‐old good and poor layers from both strains contained similar numbers of yellow‐yolky follicles.

6. After feeding a fat‐soluble dye, the number of days over which eggs containing dye were laid did not differ between 26‐, 52‐ and 113‐week‐old hens from an egg laying strain. However, fewer eggs with dyed yolks were laid by the older hens.

7. These observations suggest that the decrease in egg production with age is due initially to a reduction in the rate of recruitment of yellow‐yolky follicles. Towards the end of the laying year it may also be due to an increased incidence of follicular atresia, internal ovulation and the production of membraneous or soft shelled eggs.     

Behavioural and anatomical consequences of two beak trimming methods in 1‐ and 10‐d‐old domestic chicks

1. To examine the effects of beak trimming on behaviour, beak anatomy, weight gain, food intake and feather condition 360 ISA Brown chicks were trimmed by hot cut or cold cut at 1 d or 10 d of age or were sham‐operated controls. The experiment was a 3 × 2 factorial design, with the chicks housed in littered pens in groups of 10 and observed for 6 weeks after trimming.

2. In the first week after trimming, when trimmed birds were compared with untrimmed controls, they were less active (sat and slept more), fed less, preened less and generally engaged in less beak‐related behaviour.

3. These differences waned sharply during week 2 and had disappeared by week 5. There were very few differences between hot‐ and cold‐cut birds.

4. There were also differences in production variables: trimmed birds grew more slowly during the week after trimming, their food intake was depressed for 3 weeks and food conversion efficiency improved for 2 weeks.

5. The only significant effect on feather scores was better plumage condition in the groups trimmed at 1 d and scored at 6 weeks.

6. To examine the anatomical effects 36 ISA Brown chicks trimmed by hot or cold cut at 1 d or 10 d of age were killed at 21 and 42 d after trimming, and their beaks were processed and examined histologically. In all trimmed groups healing was very rapid and no scar tissue was seen but, unlike the controls, the regrown tips contained no afferent nerves or sensory corpuscles.

7. Beak lengths immediately after trimming were 40% to 50% shorter than controls; the anatomical consequences of both methods were identical.

8. Overall, it was judged that the effects on behaviour and beak anatomy were much less severe than previously reported for birds trimmed at older ages. If birds do have to be trimmed then the procedure should be carried out in young birds: from the birds' standpoint 1 d appears to be the most suitable.     

Variation among individual white‐leghorn hens in the concentration of minerals in the albumen and yolk content of their eggs

1. The mineral composition of the albumen and yolk was determined in several eggs from each of a number of individual hens from the same White‐Leghorn strain. X‐ray fluorescent spectrometry was used to undertake two independent series of analyses. A total of 8 minerals (calcium, chlorine, iron, magnesium, phosphorus, potassium, sodium, sulphur) were included in the analyses of the yolk and the same minerals, but excluding iron (which is present in only small amounts), in the albumen.

2. There was considerable variation between individuals in the mineral concentration in their eggs (coefficients of variation ranged between 3.8% for sodium to 19.9% for calcium in the albumen, and between 4.3% for phosphorus to 11.8% for iron in the yolk).

3. At the same time, the moderately high repeatability of mineral concentration (t = 0.4?0.6) in successive eggs from the the same hen for several of the minerals analysed is indicative of some positive control by the hen of the mineral composition of her eggs.

4. There was a highly significant correlation (P≤ 0.001) between the mean concentration of potassium in the albumen and the hatchability of the eggs, supporting the claim that a deficiency of potassium in the egg could be the basis of some failures in hatchability.

5. The study also revealed variation among individual birds in the concentration of iron in the yolk which was negatively correlated (P≤0.01) with hatchability. No clear basis could be suggested for this variation among individual birds.     

Battery gage shape: The laying performance of medium‐ and light‐body weight strains of hens

1. One thousand two hundred and ninety‐six medium‐ and 1296 lightweight hens were housed, four to a cage, in deep (conventional) cages, 405 mm wide by 460 mm deep, or shallow cages, 610 mm wide by 305 mm deep, between 18 and 70 weeks of age. The performance of the hens during different periods of the laying stage and over the full laying year was measured.

2. Egg number per medium‐weight hen housed in shallow cages was significantly higher than of hens housed in deep cages between 18 and 30 weeks and 31 and 42 weeks. Thereafter significant differences were not found. With the light‐weight hens the increase was significant only in the 18‐ to 30‐week period. Apart from the 19‐ to 30‐week period hens of both strains housed in shallow cages consumed significantly less food than those in deep cages, the reduction over the full year being about 4%. In all periods the hens housed in the shallow cages converted food more efficiently. Gage shape had no significant effect on mortality.

3. The incidence of hair‐cracked, cracked and broken eggs between 60 and 70 weeks of age from hens housed in shallow cages was lower than that from hens housed in the deep cages but only with the light‐weight hens did this difference reach significance. Shell thickness, shell weight and albumen quality of eggs laid by hens housed in the different shaped cages were not significantly different.     

The effect of reserpine on plasma LH concentrations in intact and Gona‐dectomised domestic fowl

1. Reserpine was found to inhibit the secretion of luteinising hormone when injected into intact and gonadectomised fowl at a dose rate which caused heavy sedation.

2. This could indicate that reserpine or its derivatives should not be used for breeding poultry.     

Egg‐shell deposition and blood plasma inorganic phosphorus concentration in individual laying hens

1. The relationship between plasma inorganic phosphorus measured at the end of the dark period and the weight of the next egg shell produced was investigated in 30 Hisex Brown hens.

2. Hens received an adequate conventional layers’ diet and the lighting pattern was conventional (17 L:7 D). Observations were made early (31 to 40 weeks) and late (62 to 68 weeks of age) in the laying period.

3. Eggs were classified by position in the clutch sequence and significant negative correlations were found between shell weights of early eggs in the sequence and plasma phosphate at the end of the dark period.

4. No significant trends were found in plasma total calcium.

5. No significant differences were found in bone compositions of birds producing consistently more or less than average shell weight during the laying period.

6. The negative correlations between plasma phosphate and shell weight are consistent with the observations of Sauveur and Mongin (1983) and show that impairment of shell deposition is associated with skeletal mobilisation as indicated by increase in plasma phosphate. This is consistent with the observations on bone composition and indicates that selection for shell quality will tend to select birds which are not dependent on excessive skeletal mobilisation during shell formation.     

Effects of feeding deoxynivalenol‐contaminated oats on reproduction performance in white leghorn hens

1. The effect of feeding trichothecene‐contaminated diets with graded concentrations of deoxynivalenol ranging from 120 to 4900 μg/kg to groups of laying hens was investigated.

2. Food intake, weight gain and egg production were not affected by mycotoxin administration. No significant differences were found between groups.

3. The overall results from the hatching tests did not reveal any significant differences in fertility, hatchability or perinatal mortality, which could be explained by the mycotoxin content in the diets.

4. Body weight at hatching and viability of the chicks were not affected by the mycotoxin concentrations in the diets.

5. The incidence of chick developmental anomalies was increased in the mycotoxin‐administered groups compared to controls. Minor malformations were the dominating anomalies and included unwithdrawn yolk sac and delayed ossification. The most frequent major malformations were cloacal atresia and cardiac anomalies.     

Disease outbreak in laying hens arising from the consumption of fumonisin‐contaminated food

1. During the last quarter of 1995 an unusual disease outbreak characterised by black sticky diarrhoea, severe reduction in food intake, egg production and body weight follow by lameness and death was observed in 2 layer farms in Andhra Pradesh. A total of 6700 hens of 64 weeks age and 3000 hens of 36 weeks age were affected.

2. Around 10% mortality and a 20% reduction in egg production was observed. Postmortem examinations showed pale yellow coloured livers with peripheral congestion, mild haemorrhage in the proventriculus and watery accumulations in the intestine.

3. The disease was traced to a new batch of food and its withdrawal improved the health status of the flocks.

4. Analysis of the diet indicated contamination with fumonisin B₁ up to 8–5 mg/kg and with aflatoxin B₁ up to 0.1 mg/kg.

5. Diarrhoea was induced in day old cockerels by feeding the suspect diet containing 8.5 mg/kg fumonisin Bi, and in laying hens by feeding a normal diet with fumonisin B₁ additions of 8 and 16 mg/kg.     

Factors affecting food intake in the domestic chicken: The effect of infusions of nutritive and non‐nutritive substances into the crop and duodenum

1. Infusions of 10 g of diet mashed in 20 ml of water, increasing glucose loads and hypertonic solutions of glucose, sorbitol and KC1, were introduced into the crop of the adolescent cockerel (1.5 to 2.0 kg body weight and 12 to 20 weeks of age). All caused a significant reduction of food intake over the following 3‐h period.

2. Duodenal infusions of hyperosmotic solutions of sorbitol and KC1 at 3 osm significantly decreased food intake within an hour of infusion. Glucose infusions decreased intake only in birds starved for 3 h before the experiment.

3. The results are discussed in relation to the site of infusion and nutritive visceral mechanisms of food intake control. It is likely that there is a major osmotic control in the duodenum which may affect a secondary control system in the upper gastro‐intestinal tract.     

Faecal measurements of oestradiol and testosterone allow the non‐invasive estimation of plasma steroid concentrations in the domestic fowl

1. Radioimmunoassays were validated for oestradiol and testosterone in faecal and plasma samples from domestic fowls. Faecal samples were prepared in phosphate buffer. A delay of up to 24 h between defaecation and the freezing of a dropping did not affect faecal steroid concentrations.

2. Differences in plasma concentrations of testosterone and oestradiol between cockerels and hens were clearly reflected in faecal hormone concentrations. Faecal concentrations of oestradiol were low in males and did not overlap with much higher concentrations in females, whereas there was some overlap between the sexes in faecal concentrations of testosterone.

3. The correlation coefficients (r²) between plasma and faecal steroid concentrations were 0.464 for testosterone and 0.852 for oestradiol (log‐transformed data). The coefficients did not increase when the mean hormone concentrations for several droppings produced by each bird during a collection period were used.

4. Faecal steroid concentrations can be used as a measure of plasma steroid concentrations and hence of gonadal activity in chickens. The resolution of the faecal steroid method is less than if plasma measurements were used, but it offers a practical alternative to blood sampling that is non‐invasive and does not require birds to be handled.     

Plasma growth hormone and insulin‐like growth factor‐I (IGF‐I) concentrations at the onset of lay in ad libitum and restricted broiler breeder fowl

1. Plasma concentrations of growth hormone (GH) and insulin‐like growth factor I (IGF‐I) were determined in individually caged broiler breeder females from 17 to 30 weeks of age. The birds were fed ad libitum or restricted during rearing in a randomised block design. Restricted birds were fed ad libitum after laying an egg and egg production was recorded to 54 weeks.

2. GH concentrations were higher in restricted compared with ad libitum‐fed birds at 17 to 21 weeks of age and were similar thereafter. Plasma IGF‐I concentrations were higher in restricted compared with ad libitum‐fed birds throughout the sampling period of the experiment.

3. The age at first egg was delayed by about two weeks in restricted birds. At 54 weeks of age they had laid 114 compared with 67 eggs in birds fed ad libitum throughout and had produced less than half the number of eggs with defective shells.

4. It was suggested that differences in egg production between ad libitum and restricted broiler breeder females could be related to changes in the pattern of GH and/or IGF‐I secretion.     

Effect of clenbuterol on beta‐adrenoceptors and adenylate cyclase activity in smooth muscle and epithelium of the trachea of calves

Summary

A potent ß‐agonist (clenbuterol) was administered perorally to young calves for 50 days. After this period the animals were slaughtered and ß‐adrenoceptor density, ligand affinity, and basal and stimulated adenylate cyclase activities were studied in smooth muscle and epithelium of the trachea. Although the density of lung ß‐adrenoceptors was down regulated by clenbuterol, cAMP production remained constant (epithelium) or even increased (smooth muscle). Therefore desensitization of ß‐adrenoceptors in the trachea was not observed. This might be a reason for the effectiveness of long‐term treatment with ß‐agonists.