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

T. R. Morris  P. J. Sharp  E. A. Butler 《British poultry science》1995,36(5):763-769

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.  相似文献   

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

M. H. Maxwell  I. A. Alexander  G. W. Robertson  M. A. Mitchell  C. C. McCorquodale 《British poultry science》1995,36(5):791-798

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.  相似文献   

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

B. Mohan  R. Kadirvel  M. Bhaskaran  A. Natarajan 《British poultry science》1995,36(5):799-803

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.  相似文献   

Perch length in cages for medium hybrid laying hens     

M. C. Appleby 《British poultry science》1995,36(1):23-31

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.  相似文献   

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

P. E. Waibel  M. G. Macleod 《British poultry science》1995,36(1):39-49

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.  相似文献   

Monoclonal antibodies identifying chick gonadal cells     

R. Kingston  N. Bumstead 《British poultry science》1995,36(2):187-195

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.  相似文献   

Evidence that the eumelanin restrictor genes (Co) and (Db) are present in the genome of the Buff Rock bantam     

W. C. Carefoot 《British poultry science》1995,36(2):205-207

1. An investigation was conducted among the progeny from crosses between Buff Rock and Light Sussex bantams, and between Buff Rock and Gold‐Pencilled Hamburgh bantams in order to ascertain whether the eumelanin restrictor genes Columbian (Co) and Dark‐brown (Db) were present in the genome of the Buff Rock.

2. The Light Sussex and Gold‐Pencilled Hamburgh bantams used in this study were known to be Co/ Co db⁺ / db⁺ and co⁺ / co⁺ Db/ Db respectively.

3. In both F₂ generations the least eumelanin restricted segregants were as the parent mated with the Buff Rock, thus demonstrating the Buff Rock bantam tested to be Co/ Co Db/ Db, or possess similar alleles at these loci.

4. The Buff Rock bantam male was found to be heterozygous for a eumelanin inhibitor gene which appears to be dominant white (I).  相似文献   

The role of ion transport in the formation of sub‐embryonic fluid by the embryo of the Japanese quail     

E. M. Babiker  G. K. Baggott 《British poultry science》1995,36(3):371-383

1. Using a modification of the method of New (1955) explanted blastoderms of the Japanese quail were cultured for up to 72 h, and the role of ions in the formation of sub‐embryonic fluid (SEF) investigated.

2. Culture media deficient in either sodium or chloride ions reduced the volume of SEF secreted by up to a quarter. Ionic composition of the fluid was little altered, and sodium was transported against a concentration gradient.

3. Amiloride, an inhibitor of Na⁺/H⁺ exchange, reduced SEF production by half, whereas ionic composition and osmolality of the fluid was unchanged.

4. Likewise, acetazolamide, an inhibitor of carbonic anhydrase, reduced SEF production by the blastoderm, and left the ionic composition and osmolality of the fluid unaltered.

5. Neither furosemide or 4,4´‐diisothiocyanatostilbene‐2,2´‐disulfonic acid at the concentrations used changed the volume of SEF formed or its ionic composition.

6. It is concluded that the secretion of SEF is dependent upon the active transport of sodium across the blastoderm; an amiloride‐sensitive Na⁺/H⁺ exchanger and carbon dioxide hydration catalysed by carbonic anhydrase are also involved.

7. Furthermore, it is proposed that fluid transport across the blastoderm is the result of local osmotic gradients, not from a sub‐embryonic fluid hyperosmotic to albumen, as has been suggested previously.  相似文献   

Effect of diet and natural variations in climates on the performance of laying hens     

J. Njoya 《British poultry science》1995,36(4):537-554

1. Laying hens raised in 3 natural tropical environments were fed on 2 series of diets with a view to defining the optimum combination of climate and dietary energy.

2. A combination of 3 growing climates, 3 laying climates (temperate, hot dry, hot humid), and 2 dietary energy concentrations (10.03 and 11.70 MJ ME/kg with protein concentrations proportional to energy) were tested for 46 weeks using 432 point‐of‐lay pullets.

3. Both growing and laying climates significantly affected most traits measured during the laying period. The patterns of egg production showed good persistency in all environments and differences observed reduced with age.

4. The difference between the high and low energy intake reduced at high ambient temperatures. Feeding low energy diets did not affect mean age at first egg, rate of lay or the egg output in the hot dry environment, nor egg weight in either hot dry or hot humid climates. Rather, feeding low energy diets resulted in improved body weight change in all 3 laying environments.

5. The growing climate and diet interacted significandy on body weight change, while highly significant interactions between laying climate and diet occurred on rate of lay, food and energy intake and egg weight during the laying period.  相似文献   

Dynamics ofRhizoctonia solani (black scurf) in successive potato crops     

G. Jager  H. Velvis 《European journal of plant pathology / European Foundation for Plant Pathology》1995,101(4):467-478

The position of plants withRhizoctonia solani sclerotia (black scurf) on progeny tubers was mapped for an experimental field at Haren where potatoes were grown continuously and in rotation with other crops for five successive years, and for another field at Borgercompagnie with a 12 frequency of potatoes during three potato crops. Initially, the distribution of plants with black scurf on both fields was rather dense and homogeneous. In the following years the distribution became heterogeneous and patchy. The local decline ofR. solani AG 3 (the common potato pathogen) in Haren was apparently caused by an unknown factor selectively suppressingR. solani AG 3, while simultaneouslyR. solani AG 5 increased in mass. This AG 5 type proved to be an inferior competitor of AG 3 on the potato plant in a laboratory experiment. The specificR. solani antagonistVerticillium biguttatum did not play a role. A similar factor could have reduced the formation of black scurf in the experimental field at Borgercompagnie, whereV. biguttatum was also too infrequent to account for the decline.R. solani AG 5 was not present here and could not indicate the presence of a selective factor against AG 3.  相似文献