Evaluation of the efficacy of doramectin against an artificial infection of Dictyocaulus viviparus in calves

Three groups of eight Friesian calves, reared parasite-free, were experimentally infected with 1000 infective larvae of Dictyocaulus viviparus. Two groups were injected subcutaneously with 1% doramectin at 0.2 mg/kg body weight, one group 5 days after infection and the other 25 days after infection. A third group served as untreated controls. Faecal samples were examined for lungworm larvae on days 28, 32, 33, 34 and 35 after infection; the calves were killed and necropsied 39 or 40 days after infection and any lungworms present recovered and counted. Doramectin proved 100% effective against both 5-day-old and mature D. viviparus infections.     

Skeletal muscle sarcoplasmic calcium regulation and sudden death syndrome in chickens

1. Sudden Death Syndrome (SDS) is a disease of well‐developed, predominandy male broiler chickens where death appears to occur because of cardiovascular failure. The role of skeletal muscle sarcoplasmic calcium regulation as a potential cause of SDS has been investigated.

2. Calcium regulation of skeletal muscle sarcoplasmic reticulum was compared between broiler and Leghorn chickens. Calcium regulation matured from the 2nd to the 11 th week and, at any age, broiler chickens showed significandy lower calcium transport rates and transport efficiencies. The mechanism of calcium transport in broiler chickens was more energy‐consuming than that of the Leghorn chickens.

3. Sarcoplasmic calcium regulation is pivotal for muscle metabolism. As in porcine malignant hyperthermia, weaker calcium regulation might lead to hyperactivation of skeletal muscle, followed by elevated lactic acid concentrations and cardiovascular failure.     

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.     

A test for photorefractoriness in high‐producing stocks of laying pullets

1. Pullets of 2 high‐producing commercial stocks (both brown‐egg layers) were exposed to 5 different lighting patterns between 18 and 72 weeks to test the hypothesis that photoperiods used in commercial lighting programmes early in the laying year may be unnecessarily long and, by accelerating the development of photorefractoriness, may contribute to the decline in egg production observed after the initial peak. Two rooms of 288 pullets were allocated to each treatment.

2. The rate of lay observed with a Step‐Up treatment which gave increases in photoperiod from 8L:16D at 18 weeks to 15L:9D at 27 weeks of age was not significantly different from that of treatments which held the birds on 11L:13D during peak egg production but gave increments up to 15L:9D later in the laying year.

3. A control group maintained on 11L:13D from 20 to 72 weeks laid 295 eggs per bird housed and a further group held on 8L:16D from 0 to 72 weeks laid 284 eggs per bird. These yields were lower than the Step‐Up treatment (299 eggs) but show the potential of modern hybrid stocks to lay prolifically even without light stimulation.

4. It is concluded that the stocks tested in this experiment showed no advantage when given lighting programmes in the first laying year which were designed to minimise the adverse effects of photorefractoriness.     

Identification of tissue hypoxia in the livers of ascitic and hypoxia‐induced broilers using trypan blue

1. The perfusion of livers with the vital dye trypan blue was performed to test for evidence of tissue hypoxia in 3 groups of young broiler chickens, namely, ascitic, hypoxia‐induced and controls.

2. Hepatocytes that stained with trypan blue were considered to be dead or dying before fixation and represented damaged cells.

3. The proportion of trypan blue‐stained hepatocytes in the livers of ascitic birds was slightly less than half that observed in the hypoxia‐induced birds but significandy more than the proportion of stained cells observed in control birds.

4. Liver damage in the ascitic birds was also assessed biochemically by an altered enzyme profile.

5. The study demonstrated that increased trypan blue uptake in the livers of ascitic birds reared at sea‐level may be the consequence of hypoxia stress caused by reduced oxygen utilisation.     

Effect of probiotic supplementation on serum/yolk cholesterol and on egg shell thickness in layers

1. The effect of probiotic supplementation on egg production, on serum and yolk cholesterol and on egg shell thickness in 24 White Leghorn layers was studied from 28–38 weeks of age.

2. In 3 treatments the diet was supplemented with 0, 100 and 150 mg probiotic/kg food.

3. In the 100 mg probiotic group, egg production improved by 5%, and shell thickness improved slightly, with fewer thin‐shelled eggs than in the control (8.6% compared to 18.6%).

4. The initial serum cholesterol concentration of 170.2 mg/dl in control birds remained similar throughout the 10‐week experimental period, whereas in the 150 mg group the initial value of 176.5 mg/dl decreased to 114.3 mg by week 10.

5. Yolk cholesterol concentration was 14.69 mg in the control group and 11.28 and 11.37 mg/g in the 100 and 150 mg probiotic groups respectively. Overall mean total egg cholesterol was thus reduced by probiotic supplementation.     

Evaluation of the effects of enzootic pneumonia in pigs on weight gain and days to slaughter under New Zealand conditions

The effects of enzootic pneumonia on average daily weight gain and number of days taken to reach slaughter weight was studied in 333 bacon-weight pigs. Each 1% of lung volume affected by enzootic pneumonia was shown to reduce average daily gain by 2.2 grams and increase the numbers of days to slaughter by 0.61 days. The cost of these reductions in performance was calculated to be about NZD 1 for each 1% of lung affected.     

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.     

Effect of cycling temperature on growth,energy metabolism and nutrient retention of individual male turkeys

1. Each week, from 12 to 20 weeks of age, male turkeys of a heavy strain were subjected to cool (C; 16°C), hot (H; 29°C), and cycling temperatures, and fed on a standard diet ad libitum for 4 d. Lighting was intermittent, 3 h on, 3 h off. Food was given when lights were on. Those given cycling temperatures (3 h C; 3 h H) were given food and light during the cool (eat‐when‐cool, EC) or hot (EH) periods.

2. Birds in all treatments gained similar amounts of weight from 12–14 weeks of age. Thereafter, birds in C maintained gains, the body weight gains of birds in EC and EH declined moderately and birds in H lost weight.

3. Birds in C produced more metabolic heat. Those in H showed increased heat production as they became older.

4. Protein retention was greater in turkeys in C, EC and EH. It was lower in H, becoming negative between 18–20 weeks of age. Birds in H suffered body fat losses which increased with age.

5. Birds in EH and EC gained similar amounts of body weight. Birds in EH exhibited lower heat production and greater energy retention than those in EC.

6. Body temperatures were higher in H than in the other environments.     

Monoclonal antibodies identifying chick gonadal cells

1. The aim of the present study was to raise monoclonal antibodies (MAbs) which discriminate gonadal cell types in chickens.

2. A panel of 180 MAbs was generated, from which 14 were chosen for their specificity.

3. These MAbs were characterised immunohistologically on frozen sections of embryonic, newly‐hatched and adult, male and female, left gonads.

4. Three of these MAbs are described: AGC5, AGC7, and AGC13 which recognise respectively germinal epithelial cells, supporting cells and germ cells.

5. These MAbs may be useful in following the developmental pathways in the chicken gonad and analysing the interactive role(s) taking place between gonadal stromal cells and primordial germ cells.