SUMMARYHerbage from the same timothy/meadow fescue/white clover sward was ensiled at four different dry matter contents. The resulting silages had dry matter contents of 19·0, 27·3, 32·3 and 43·2%, the dry matter content increasing with the length of the wilting period. An experiment was carried out to determine the voluntary intake of the silages. Each silage was given to 7 animals individually, the mean live weight of these being 334 kg.Although the silages made from wilted herbage were lower in digestibility than that made from unwilted herbage, wilting increased dry matter intake and metabolizable energy (ME) intake. The mean daily intakes of digestible organic matter were 53·0, 58·1, 59·6 and 59·6 g/kgW0·73, for silages of increasing dry matter content. The corresponding ME intakes, expressed as a multiple of the ME requirement for maintenance, were 1·17, 1·29, 1·30 and 1·28. The percentage of acetic acid in the silage dry matter was significantly (r= −0·56) and linearly related to voluntary intake. The relationship between lactic acid concentration and voluntary intake was significantly curvilinear (r= 0·48).

I . Two experiments are reported. In both experiments a cereal-based diet containing 5 mg copper/kg was fed to two breeds of laying hens for 336 d. In Expt I four other groups were given this diet with the addition of CuSO,. 5H,O to give added levels of ZOO, 400, 600 and 800 mg Cu/kg diet. In Expt 2 the levels of added dietary Cu used were IOO, zoo, 300 and 400 mg/kg.2. In Expt I records were kept of food intake, water intake, body-weight and egg production for eight 28 d periods and body-weight and egg number only were recorded for the full twelve periods. In Expt 2 full records, excluding water intake, were taken for all twelve periods.3. Food and water intake showed a quadratic response to level of added dietary Cu, being enhanced at lower levels and depressed at higher levels of addition.4. There was a quadratic response of total egg weight, mean egg weight and egg number to added dietary Cu. In Expt I egg number was maximum at 235 mg added Cu/kg diet for Warren Studler SSL (breed I ) and at 170 mg added Cu/kg diet for Shaver 288 (breed 2). In Expt 2 no breed effect occurred, the maximum egg number being calculated to occur at 176 mg added Cu/kg diet.5. Depression of body-weight gain occurred at high levels of Cu addition. The depression of liver and oviduct weight found at high levels of addition appeared to be directly related to body-weight. A marked amount of feather loss also occurred at a high inclusion of CuSO, in the diet.6. The reproductive systems of the hens did not appear to be adversely affected at the levels of additive used. Gross and microscopic examination of specific tissues revealed no pathological effects although gizzard and intestinal weights were increased and caecal weight decreased by high levels of added Cu. Those aspects of the blood chemistry examined did not reveal any consistent effect between the two experiments.7. The liver Cu analyses indicate that between 600 and 800 mg added Cu/kg diet the liver Cu concentration rises sharply. Both liver Fe and Zn concentrations showed a positive linear response to added dietary Cu. In the kidney Cu and Zn concentrations were increased but only to a limited extent, while the concentration of Fe was unaffected.The effects of adding copper compounds to the diet of the fowl have been briefly reviewed (Jackson, 1977). The growth and food conversion responses of adding Cu compounds to the diet of the growing bird have been statistically analysed (Fisher et al. 1971 ;Fisher, 1973). Th: ir results indicated a quadratic response of body-weight gain and food conversion efficiency to added dietary Cu. This was clearly defined at higher levels due to growth depression, but the positive response at lower levels (up to 300 mg Cu/kg diet) was considered to be real. There was a maximum growth stimulation at approximately 170 mg Cu/kg diet and a maximum food conversion at 140 mg/kg. In the broiler, Janssen ( There have been few studies on the effect of added Cu as salts or oxides in the diet of the laying hen. In a recent study (Jackson, 1977) Cu, as sul...

1. A cereal-based diet containing 16 mg copper/kg was fed ad lib. to a group of laying hens for 35 d. Five other groups were given this control diet to which was added 120, 240, 480, and 1920 mg Cu/kg (as copper sulphate). 2. Records were kept of daily food intake, water intake and egg production. 3. After 35 d the hens were slaughtered and blood haemoglobin, packed cell volume, Cu and aspartate aminotransferase (EC 2.6.1.1) levels assayed. Liver, oviduct, kidney and breast muscle Cu and iron concentrations were measured. 4. Food and water intakes were depressed by the two highest levels of dietary Cu and water intake was increased by the diet with 240 mg added Cu/kg. Both food and water intake showed a quadratic relationship with the level of added dietary Cu. 5. Body-weight loss was increased by the addition of Cu and showed a significant linear relationship with the concentration of added Cu in the diet. Liver and oviduct weights were depressed at the two highest levels of Cu addition. 6. Liver and oviduct Cu and Fe concentrations were significantly increased by high dietary Cu and mean total liver and kidney Cu and Fe showed an increase although for the liver this was not statistically significant.

The effect of temperature on the heat production, of temperature-acclimatized feathered and defeathered cockerels was examined at 15, 22, 25, 29, 34 and 38 °C. The maintenance ME requirements and the net availability of ME (NAME) were determined for each temperature.The fasting heat production of defeathered cockerels measured at 22, 29, 34 and 38 °C, decreased continually with increasing temperature. The feathered cockerels also showed a general decrease in fasting heat production with increasing temperature between 15 and 34 °C, but there were relative increases in fasting heat production between 22 and 29 °C.The ME requirement for maintenance and the NAME were determined from measurements of heat production at different levels of ME intake. In general, the maintenance ME requirement decreased with increasing temperature for both feathered and defeathered cockerels. The NAME for the defeathered birds varied between 75 and 77 % at 29, 34 and 38 °C. There was evidence for the feathered birds of an increasing NAME with increasing temperature, one feathered bird having a NAME of 56% at 15 °C, increasing to 81 % at 34 °C.The importance of feathering and environmental temperature on the heat production and the possible effect of feather cover and activity on the NAME are discussed.

An experiment is described in which extracted Algerian rapeseed meal was included at levels of 4, 8, 12, 16 and 20% in the diet of two hybrid strains of caged laying hens.The rapeseed meal was thyrotoxic and this effect, when assessed by thyroid weight per kg of body weight, was more marked for the light-weight hybrid than for the medium-weight hybrid birds.The light-weight hybrids exhibited a high mortality when fed rapeseed meal at a level of 8 % or above in the diet but inclusion of rapeseed meal did not cause increased mortality in the medium-weight hybrids.The medium-weight hybrids gave satisfactory egg production when fed up to 16% of dietary rapeseed meal; food conversion efficiency was best with 8% of dietary rapeseed meal, and metabolisable energy conversion (Mcal/kg eggs) and the efficiency of utilisation of protein were satisfactory at all levels of rapeseed meal inclusion. The rapeseed meal used had a standard metabolisable energy content of 1820 kcal/kg at a dry matter content of 89 %.