Antimicrobial substances and chick growth promotion: Comparative studies on selected compounds in vitro and in vivo

1. Antibacterial activity of selected compounds in vitro and their ability to promote growth when added to the diet of chicks were not correlated.

2. The difference in growth‐promoting activity between streptomycin, which was active, and kanamycin which was not, was not related to their effects on the flora adhering to the wall of the crop, jejunum or ileum, to their relative toxicity to the chick nor to differences in their stability in the diet.

3. When low concentrations ofkanamycin or streptomycin were given, the antibiotic was concentrated in the caecal contents. In contrast, penicillin was undetectable in the caeca of birds given high concentrations of benzyl penicillin.

4. In chicks given benzyl penicillin, the numbers of Streptococcus faecium increased at the expense of Strep, faecalis. This probably resulted from changes in the crop flora.

5. Birds given high dietary concentrations of benzyl penicillin showed improved weight gains, in spite of increased numbers of Escherichia coli in the small intestine.     

Diurnal patterns of feeding and activity in laying hens in relation to dietary restriction and cage shape

1. The diurnal feeding pattern and motor activity of medium‐weight hybrid hens housed in groups of four were observed. Cages of two shapes were compared: conventional deep cages (406 × 457 mm) and shallow cages (610 × 305 mm).

2. Birds in conventional deep cages were more active than those in shallow cages in each of four different periods of day. Activity reached a peak between 11.00 and 13.00 h irrespective of cage shape.

3. Mean feeding activity was greater in the shallow (45.6%) than in the conventional deep cages (39.9%).

4. Mean feeding activity was greater in birds fed ad libitum (43.3%) than in those fed on a restricted diet (40.4%).

5. Although restricted birds in shallow cages showed more feeding activity than those in conventional deep cages they consumed less food (56% against 67%) in the 7 h between supply of their daily ration and the onset of the dark period.

6. Feather damage was greater in the conventional deep cages than in the shallow cages.

7. The more efficient utilisation of food by hens in shallow cages is probably due largely to three factors: reduced levels of motor activity and general disturbance, a more leisurely eating pattern and better feather cover.     

The hen's egg: Relationship of mean strain energy at shell fracture to shell compression speed,the nature of the compressing body and the location on the shell of the point of contact

1. The mean energy, E_f, required for fracture of an egg shell at its equator by a flat plate is known to depend on shell compression speed, v_m, for speeds in the range 20 μm/s to 2.lb5 mm/s; analysis of published data shows that E_f bears a linear relationship to log (v_m ) throughout the industrially important speed range from 20 μm/s to 1.lb1 m/s, increasing from 1.lb3 to 5.lb0 mJ.

2. At lower speeds down to 2 μm/s E_f is constant.

3. E_f is reduced if the flat plate is replaced by a sphere or cylinder; the greater its curvature, the smaller E_f.

4. E_f for the narrow pole is greater and for the broad pole smaller than that for the equator but these differences may be due in part to . systematic differences in shell thickness as well as curvature.     

Biochemical,physiological and production indices related to fat metabolism in the laying fowl at various stages of physiological development

1. The significance of fat accumulation during physiological development of layers was studied using White Leghorn x Australorp pullets from 12 weeks of age.

2. Liver fat, carcass fat, liver weight and body weight increased markedly at the onset of sexual maturity.

3. Within the liver, the protein to DNA ratio did not alter significantly during development; glycogen was not consistently depleted by egg production.

4. Liver fat content was significantly correlated with carcass fat, liver weight and DNA concentration, and plasma total lipid and cholesterol, independent of stage of development; with body weight, liver protein, moisture, and protein to DNA ratio, excluding the period prior to commencement of sexual maturation; and with plasma phospholipid during lay.

5. Obesity was a feature of faster growing fowls which matured earlier, consumed more, utilised food less efficiently for egg production and produced fewer saleable eggs.     

The relative growth of internal organs in light and heavy breeds

1. The relative weights of the gastrointestinal segments and of some other internal organs from light and heavy breed chicks from hatching to 21 days of age were compared.

2. The relative weight of the duodenum and jejunum was higher in the light breed than in the heavy one, the reverse relationship was found for the ileum and caecum.

3. The relative growth of the pancreas, heart, cerebrum and cerebellum was greater in the light breed.     

Agonistic interactions in developed and undeveloped breeds of chickens

1. Agonistic interactions were observed over a 24‐week period in Rhode Island Red and in Nigerian local fowl aged 32 weeks or 12 weeks at the start of the experiments.

2. Agonistic interactions were both more numerous and more severe (fights and peck avoidances) in groups of the local breed than in those of Rhode Island Reds.

3. The outcome of severe interactions favoured local males and Rhode Island females in the first experiment and Rhode Island males in the second.

4. Small body and comb size might account for the relatively high number of agonistic interactions and the submissiveness of local females and young males while physical strength or some other breed characteristic might account for the high number of agonistic interactions of local males as well as their dominance in breed encounters.     

Effect of different patterns of food restriction from different ages on growth and efficiency of broilers

1. The effect of restricted feeding on performance and carcass characteristics of broilers was determined in three experiments.

2. In the first experiment, removal of food for 8 h/d from 42 to 56 d of age significantly improved food conversion efficiency of broilers on deep litter. Removal of food for 16 h/d or on alternate days tended to cause slower growth and also improved conversion efficiency.

3. In the second experiment, denial of food for 8 h/d did not significantly affect either growth rate or conversion efficiency of caged broilers. Denial of food on alternate days, from 28 d of age, depressed food intake and growth rate. Food restriction decreased dressing percentage regardless of the age of introduction. With 32, 40 or 48 h food denial each 72 h there was a large depression in growth rate and dressing percentage. Carcass dry matter was also less, indicating less carcass fat, when food was denied for 48 h each 72 h.

4. In the third experiment, growth rate of broilers on deep litter was significantly improved by denying food for 8 h/d from 28 d of age, and was significantly depressed by food denial on alternate days. This depression was significantly more severe if restriction started at 28 d rather than at 42 d of age. Conversion efficiency was not significantly improved by denial for 8 h/d.

5. In the last two experiments conversion efficiency was much worse in severe restriction.     

Rapeseed meal and egg taint: Treatment of rapeseed meal to reduce tainting potential

1. Treatment of rapeseed meal with calcium hydroxide suspension decreased the sinapine content by up to 90%. Smaller decreases were obtained by autolysis, steaming and treatment with ammonia.

2. When this treated meal was fed to susceptible ("tainting") hens the concentration of trimethylamine in the eggs was decreased to much less than that required to cause taint.     

Effect of light,vitamin d and dietary phosphorus on egg‐shell quality late in the pullet laying year

1. Eighteen diets supplying all combinations of three phosphorus contents (3.1, 4.0 and 4.8 g non‐phytate P/kg) and six vitamin D supplements (37.5 or 150 μg cholecalciferol/kg; or 16 or 24 μg 25‐hydroxy‐cholecalciferol/kg; or 37.5 μg cholecalciferol/kg with either 16 or 24 μg 25‐hydroxycholecalciferol/kg) were fed to 2 880 pullets of two stocks from 64 to 74 weeks of age. The birds were housed in eight light‐proof rooms, four of which had 24‐h light‐dark cycles (16L : 8D) and four had 28‐h cycles (20L : 8D).

2. The dietary treatments had no significant effect upon food intake, egg output, shell thickness, shell deformation or specific gravity of the eggs.

3. The 28‐h cycle reduced mean rate of lay by 4.5%, increased egg weight by 5.8% and increased shell thickness by 9.4%. The proportion of eggs with shell faults revealed on candling was reduced from 4.1 % to 2.8%.

4. It is concluded from this and other sources that decreasing dietary phosphorus or modifying vitamin D supplements may sometimes lead to increases in shell thickness of the order of 1 to 2%, but that these changes are unlikely to result in a measurable reduction in the proportion of cracked eggs late in the laying year.

5. A 28‐h light‐dark cycle results in a longer and more uniform interval between consecutive ovipositions and thus gives reliable increases in shell thickness which are large enough to reduce the proportion of cracked eggs in many practical situations. Whether it is profitable to use an ahemeral cycle will depend upon the relative prices paid for eggs of different sizes.     

Comparison of maize,wheat and triticale in broiler diets

1. Wheat, triticale 131 or triticale 72‐S could replace up to half the maize in broiler diets without affecting performance. Replacing more of the maize on either an equal nitrogen basis or a weight basis adversely affected performance.

2. Triticale 72‐S appeared to be superior to triticale 131 as a direct replacement for maize, but both grains were inferior to maize as energy sources.