Effect of dietary medium chain triglyceride on protein and energy utilisation in growing chicks.

1. Protein, fat and energy retentions of chicks fed on diets containing medium chain triglyceride (MCT) and long chain triglyceride (LCT), at 100 and 200 g fat/kg diet, were investigated. Maize oil was used as the LCT source. The MCT used was glyceryl tricaprylate. 2. Body weight gain and food intake were decreased with the diets containing MCT and these effects were greater at the higher fat concentration. Protein retention was also reduced by dietary MCT, although the efficiency of protein utilisation (protein retained/protein intake) was not altered. 3. The values for fat and energy retentions were significantly lower in the chicks fed on the MCT-supplemented diets than in those receiving the LCT-containing diets. Dietary ME values and efficiencies for energy utilisation (energy retained/ME intake) were also reduced by dietary MCT.     

Influence of energy intake on growth and utilisation of dietary protein and energy in germ-free and conventional chicks

The effect of metabolisable energy (ME) intake on the growth and utilisation of dietary protein and energy in germ-free (GF) and conventional (CV) chicks was investigated in two experiments. In experiment 1 a high energy diet (HED, 14.8 kJ ME/g) and a marginally-adequate energy diet (AED, 11.7 kJ ME/g) were fed to the GF and CV chicks at 240 g/2 birds/10 d. In experiment 2 a diet with 13.7 kJ ME/g was fed at 118 g (low level, LL) or 128 g (high level, HL)/bird/10 d. Body weight gain, protein retention and protein retention rate were similar in GF and CV chicks on both AED and HED in the first experiment, but in the second were higher in GF than in CV chicks. The increased ME intake of the CV chicks in experiment 2 may be too small to compensate for the increased requirement. ME intake was significantly higher in the CV chicks than in the GF chicks, whereas energy retention was similar in both groups.     

Effect of the gut microflora on chick growth and utilisation of protein and energy at different concentrations of dietary protein

The effect of the gut flora on chick growth and protein and energy utilisation at a marginal dietary energy level (calculated metabolisable energy value 11.7 MJ/kg) was determined with diets containing 227 or 293 g protein/kg. Germ-free (GF) and conventional (CV) chicks were reared for 10 d on the diets, and excreta were collected during the last 4 d. The chicks were killed and carcases and droppings were analysed for N and fat. The GF chicks grew significantly faster than the CV controls on both diets. The growth of CV chicks given the high protein diet was similar to that of GF chicks given the adequate protein diet. Protein and energy utilisation were significantly less for CV than for GF chicks on both diets. It was concluded that the energy requirement of CV chicks was greater than that of their GF counterparts, and that their poorer growth was due to utilisation of some dietary protein as an energy source.     

Improvement of dietary protein utilisation in chicks by medium chain triglyceride

1. To improve the influence of variation of ME intake, an experiment was carried out using equalised feeding to investigate the comparative effects on protein and energy utilisation in chicks of diets containing medium chain triglyceride (MCT) and long chain triglyceride (LCT). Experimental diets were given at 3 different food intakes, namely, 100, 120 or 147 g/bird/10 d. The diets contained MCT or LCT on an isoenergetic basis. Maize oil and caprylic acid triglyceride respectively, were used as LCT and MCT sources.

2. Body weight gain and food efficiency of chicks significantly increased with the supplement of dietary MCT compared with dietary LCT at all food intakes. Protein retention and the efficiency of protein utilisation (protein retained/protein intake) at all food intakes also significantly increased with dietary MCT, while body fat and fat retention were significantly reduced. Chicks fed the LCT‐supple‐mented diet, on the other hand, had a lower protein retention, but significantly higher fat retention. The value for energy retention and the efficiency of energy utilisation (energy retained/ME intake) were not significantly different between MCT‐ and LCT‐supplemented diets.

3. It was concluded that supplementing MCT to the chick diet would improve body weight gain and protein utilisation while regulating fat deposition compared to the LCT supplemented diet, under equalised feeding conditions.     

Effect of short chain fatty acids on the performance and intestinal weight in germ-free and conventional chicks

1. In experiment 1, the performance and tissue weights of germ-free (GF) and conventional (CV) chicks fed on diets containing 25.4 g acetic acid/kg diet (AD) or 25.4 g kaolin/kg diet (KD) were investigated. Body weight gain in GF chicks was significantly higher on the AD, but significantly lower on the KD compared with their CV counterparts. The values for food efficiency, protein retention and energy retention followed a similar pattern to that of the body weight gain. 2. The weights of all sections of the intestine except the colon were significantly greater in CV chicks. In CV but not in GF birds the jejunum and ileum were heavier from birds fed on the AD than from those on the KD diet. 3. In experiment 2, the influence of butyric acid administration on the weight of some organs in chicks was investigated. The weight of duodenum, jejunum and ileum was significantly increased by intraperitoneal administration of butyric acid (2 ml of 100 mM solution/d) for 4 d, but no significant effect was observed by oral administration. 4. It might be suggested that short chain fatty acids such as acetic and butyric acids formed by bacterial action in the crop and subsequently absorbed are at least partly responsible for the heavier gut weight in CV birds.     

Involvement of food intake in the decreased energy retention associated with single deficiencies of lysine and sulphur-containing amino acids in growing chicks.

1. Growth and energy utilisation were determined in growing chicks fed ad libitum on diets deficient either in lysine (5.95 g/kg) or in sulphur-containing amino acids (SAA, 3.5 g/kg). Food intake, body weight gain, energy retained as protein and as fat, and total energy retention were significantly (P less than 0.05) reduced by single deficiencies of either lysine or SAA. 2. Another two experiments were conducted to determine if the decreased total energy retentions in chicks fed on diets deficient in lysine (experiment 3) or SAA (experiment 4) were associated with reduced food intake, by using tube-feeding to control the amount and pattern of food consumption. Chicks fed on diets deficient in lysine or SAA retained less energy as protein and more energy as fat than the control chicks. Neither total energy retention nor heat increment was affected by these deficiencies. Total energy retention was proportional to metabolisable energy (ME) intake alone. 3. It is concluded that the decreased total energy retentions caused by single deficiencies of lysine and SAA were associated with decreased food intake.     

Effect of the gut Microflora on the size and weight of organs of chicks fed diets of different protein content

1. Germ‐free (GF) and conventional (CV) chicks were reared for 14 d on diets containing 50 (LD), 200 (AD) and 400 (HD) g protein/kg. Food and water were provided ad libitum. The size and weight of the proven‐triculus, gizzard, duodenum, jejunum, ileum, caeca, colon, liver, pancreas, heart, spleen, adrenal glands and kidneys were measured, and liver composition was examined.

2. The absolute and relative (weight/kg body‐weight) weights of the intestine of CV chicks fed AD and HD diets were greater than those of GF chicks. The LD diet did not affect the absolute and relative weights of the duodenum and jejunum.

3. The absolute weight, relative weight and fat content of the liver of GF chicks given LD diet were greater than those of their CV counterparts.

4. The size and weight of some organs are affected by the diet (dietary protein content)‐microflora‐host interaction.

     

Comparison of the utilisation of palm kernel meal,brewers' dried grains and maize offal by broiler chicks

1. Palm kernel meal (PKM), brewers dried grains (BDG) and maize offal (MO) were included in broiler diets, each at 100, 150 or 200 g/kg; the diets were fed up to 35 d of age. 2. Overall food intake and weight gain decreased in the order BDG, PKM and MO. There were, however, significant interactions between the test ingredients and dietary concentrations in all the growth responses. Food intakes increased with the dietary concentrations of each test ingredient, but the increase was greater for BDG than PKM or MO. For weight gain, at 100 g/kg, the final body weights of the chicks fed on the diets with BDG and MO were similar, and those of chicks fed on the diet with PKM slightly lower. However, at 200 g/kg, growth rate of chicks fed on the BDG and PKM diets were similar while those of chicks fed on the MO diet was 7% lower. Efficiency of food utilisation was similar at 100 g/kg for all the ingredients and decreased as their concentrations increased; however, the decrease was considerably less for the PKM than for the MO and BDG diets. 3. Broilers fed on the BDG-based diets voided most excreta followed by those fed on the PKM and MO diets; excreta water content was highest from birds fed on the MO diets followed by the PKM and BDG diets. Apparent retention of dry matter was similar with all the test ingredients, but it decreased only significantly at 200 g/kg dietary concentration. The rate of passage was faster with the PKM diets followed by the MO and BDG diets; it was increased at 200 g/kg dietary concentration of the test ingredients.     

Calcium and phosphorus utilisation in chickens fed on diets high in N-alkane-grown yeast

Interactions between calcium (Ca) and phosphorus (P) were studied in young chickens fed on diets high in n-alkane-grown yeast and in chicks fed on control soya-fishmeal diets for 14 d. Additions of inorganic Ca to diets containing 300 g yeast/kg caused increases in body-weight gain, gain:food ratio and bone mineralisation up to a total dietary concentration of 13.9 g Ca/kg. At all additions of Ca, bone mineralisation was inferior in yeast-fed chicks compared with control chicks. Supplementation of high Ca diets (16.8 g Ca/kg) with inorganic P led to further improvements in body-weight gain, food intake and food utilisation of chicks fed on high-yeast diets. Bone mineralisation also improved but was always inferior in the yeast-fed chicks compared with control chicks. It was concluded that Ca and P supplementation was necessary in high-yeast diets due to low dietary Ca concentrations and low availability.     

Nutritional evaluation of high-digestible sorghum for pigs and broiler chicks

Two experiments were conducted to evaluate the nutritional quality of 2 varieties of Purdue high-digestible sorghum (PHD1 and PHD2) and a normal sorghum, compared with corn, in diets of pigs and broiler chicks. In Exp. 1, 12 pigs (average BW, 55 kg) fitted with ileal T-cannula were fed 4 diets containing 946 g of corn or sorghum (PHD1, PHD2, and normal) per kg in a 2-period crossover design (i.e., each pig received 2 diets over a 2-wk period with 6 pigs per dietary treatment) to determine apparent ileal or total tract digestibility of nutrients and energy. There was no difference in the ileal or total tract digestibility of DM, energy, P, Ca, or N among dietary treatments. In Exp. 2, a total of 192 broiler chicks were grouped by weight into 8 blocks of 4 cages each with 6 chicks per cage, and cages were assigned randomly to 1 of the 4 dietary treatments within each block. Chicks were fed corn-soybean meal (SBM) or sorghum-SBM diets for 21 d to determine apparent total tract retention and then switched to diets containing 935 g of the corresponding corn or 1 of the 3 sorghum varieties per kg for 7 d to determine apparent ileal digestibility and total tract retention. Apparent ileal digestibilities of DM and P, as well as energy, were not different in chicks fed diets containing 935 g of corn or 1 of the 3 sorghum varieties per kg. However, apparent total tract retention of DM, energy, and N in chicks fed corn was greater (P < 0.05) than those fed 1 of the 3 sorghum varieties. Although the apparent ME content of corn was greater than PHD1 and normal sorghum (P < 0.01), it was not different from PHD2 sorghum. There was no difference in apparent total tract retention of DM between chicks fed the corn-SBM and PHD-SBM diets, but it was greater (P < 0.05) in chicks fed the corn-SBM diet than those fed the normal sorghum-SBM diet. Apparent total tract retention of N in chicks fed the PHD1-SBM diet was lower (P < 0.05) than in those fed the corn-SBM diet but greater (P < 0.05) than in chicks fed the normal sorghum-SBM meal diet. No difference in the apparent ME content between the corn-SBM and PHD2-SBM diets was observed, but it was greater (P < 0.05) for the corn-SBM diet than the PHD1- or normal sorghum-SBM diet. Weight gain, feed intake, and feed efficiency were not different in chicks fed the corn-SBM or sorghum-SBM diets. Sorghum could serve as a substitute for corn in cereal grain-SBM diets for pigs and broiler chicks.     

Effect of supplementary choline on the performance of broiler breeders fed on different energy sources

1. Laying performance, egg quality, fertility and hatchability, and fat deposition in liver and abdomen were recorded in broiler breeders (29 to 48 weeks of age) fed on diets containing perarl millet (Pennisetum typhoides) (PM), broken rice (BR) or yellow maize (YM) (600 g/kg diet). Constant ratios of metabolisable energy (ME) to other nutrients were maintained in all the diets. Food grade choline chloride (50%) was added to the diets at 3 concentrations (0, 760 and 1,520 mg/kg). Each diet was offered to 3 replicate groups of 15 birds (12 hens and 3 cockerels), maintained in deep litter pens, to provide 1.46 MJ ME/bird/d. 2. Neither the source of energy nor dietary choline content had any influence on hen-d egg production, fertility or hatchability. Food efficiency and egg weight were significantly reduced in BR-fed groups compared to those fed on the other energy sources. 3. The efficiency of energy and protein utilisation increased and liver fat content was decreased significantly by dietary choline supplementation. 4. Haugh unit score, egg shell weight, liver weight and intestinal weight were not influenced by either supplementary choline or the source of energy. However, the yolk colour index was significantly reduced in PM- or BR-fed groups compared to those fed on the maize-based diet. 5. Deposition of abdominal fat was significantly greater in BR-fed birds compared to those fed on the YM-based diet, while liver fat content was significantly greater in the birds fed on the PM-or BR-based diets than those based on YM. Although supplementation of the diet with choline had no influence on abdominal fat deposition, liver fat content was significantly reduced in birds given diet containing 760 mg supplemental choline/kg diet. 6. The present study indicates that PM or BR can be used as principal energy sources in place of YM in broiler breeder diets without affecting egg production, fertility or hatchability. Liver fat content can be reduced by adding choline at 760 mg/kg to diets based on different energy sources.     

An experimental study of the utilisation, by the laying hen, of dietary energy partially supplied as animal fat

Experiments were carried out at two centres in which laying hens were fed diets containing up to 28.25 per cent tallow and in which an attempt was made to maintain a fairly constant calorie : protein ratio. The most satisfactory production was obtained on a diet containing 3.5 per cent added fat in one experiment and 7.5 per cent added fat in the other experiment. Food conversion efficiency (kg food/kg eggs) increased with increasing dietary fat content.

The efficiency of ME utilisation (Mcal/kg egg) decreased with increasing dietary ME content. The data indicate that at the higher levels of fat addition the net utilisation of ME was decreased.

In both experiments mean egg weight was increased by the addition of tallow to the diet whilst at the highest level of addition there was a very high mortality.     

Protein requirement of fast- and slow-growing chicks

1. Responses of male broiler chicks and male chicks of an egg-laying stock to dietary crude protein (CP) concentrations ranging from 167 to 251 g/kg (metabolisable energy content 13 MJ/kg) were compared from 0 to 21 d of age, using 20 groups of 9 or 10 chicks (5 diets x 2 stocks x 2 replicates). 2. Average growth rate in the broilers was three times that of the layer chicks. The broilers needed at least 251 g CP/kg to maximise their liveweight gain but the layer chicks needed only about 188 g CP/kg. 3. The broiler chicks ate less than twice as much food as the layers and their maximum gain/food ratio was 0.6 compared with 0.4 for the layer chicks. These maximum efficiencies of conversion of food to liveweight were achieved in both cases with a diet containing 230 g CP/kg. 4. The efficiency of protein utilisation (above maintenance) was the same in fast- and slow-growing genotypes (about 0.47 g protein gain/g protein consumed). 5. Carcase analysis at 3 weeks of age showed that the broilers had deposited more fat than the layers and that protein content of the diet had markedly influenced fat deposition in both stocks. Fat in the whole body increased from 29 to 87 g/kg in the layer chicks and from 81 to 123 g/kg in the broilers as dietary protein was reduced from 251 to 167 g/kg. 6. The optimum protein to energy ratio of a chick starter diet will depend on the growth potential of the stock, as well as the cost of ingredients and the value of fatter or leaner carcases.     

Effects of dietary cholestyramine on the utilisation of diets containing medium or long chain triacylglycerols by chicks

1. The effects of graded dietary concentrations of cholestyramine (CSTY, a bile acid binding polymer), which prevents micelle formation and bile acid reabsorption, on the lipid and energy metabolism of chicks given diets containing different dietary concentrations of medium chain triacylglycerol (MCT) and long chain triacylglycerol (LCT) were investigated.

2. MCT‐ or LCT‐supplemented diets containing 100 or 200 g oil/kg diet and 0, 10 or 20 g CSTY kg were fed to 7 d old chicks for 10 d. As dietary CSTY concentration increased, a reduction in the metabolisable energy value was observed for both dietary lipid sources. Consequently, fat and energy retentions were also reduced as the dietary CSTY content increased.     

Digestibility of pentose sugars and uronic acids and their effect on chick weight gain and caecal size

1. In the first experiment D-xylose, L-arabinose, D-galacturonic and D-glucuronic acids were fed ad libitum to young chicks for 2 weeks at 200 g/kg of diet and weight gains and food consumption were recorded. 2. L-arabinose and D-xylose did not depress food consumption in the first week but prolonged feeding caused food consumption to decrease and weight gain to be adversely affected. 3. D-galacturonic acid and D-glucuronic acid caused severe growth retardation as early as the first week of feeding, primarily because of voluntary starvation. 4. Apparent metabolisable energy values for the diets were obtained when chicks were 19 to 21 d of age and were 14.04 +/- 0.52, 12.03 +/- 0.61, 11.77 +/- 1.21, 11.68 +/- 0.34 and 11.66 +/- 0.45 KJ/g for the basal diet with glucose, xylose, arabinose, galacturonic and glucuronic acids respectively. 5. True metabolisable energy values for the diets were obtained from adult cockerels and were 15.07 +/- 0.16, 13.45 +/- 0.16, 13.12 +/- 0.37, 12.29 +/- 0.26 and 12.69 +/- 0.23 KJ/g for basal diet with glucose, xylose, arabinose, galacturonic and glucuronic acids respectively. 6. In the second experiment D-galactose, D-xylose, L-arabinose, D-galacturonic and D-glucuronic acid were fed ad libitum to young chicks for 3 weeks at 50 g/kg of diet and weight gains and food consumption were recorded. 7. Chicks grew and ate well on all diets. 8. The digestibilities of sugars and uronic acids were obtained by measurement of these constituents in diets and digesta using titanium dioxide as a marker. The digestibilities were 1.000 +/- 0.0, 0.997 +/- 0.002, 0.936 +/- 0.041, 0.628 +/- 0.103, 0.588 +/- 0.059, and 0.645 +/- 0.089 for D-glucose, D-galactose, D-xylose, L-arabinose, D-galacturonic and D-glucuronic acids respectively. 9. Both at 200 and 50 g/kg dietary inclusion there was noticeable caecal fermentation from L-arabinose, D-galacturonic and D-glucuronic acid. Only at 200 g/kg dietary inclusion did D-xylose produce significant evidence of caecal fermentation.     

Effect of dietary high-oleic acid sunflower seed, palm oil and vitamin E supplementation on broiler performance, fatty acid composition and oxidation susceptibility of meat

1. A study was conducted to evaluate the effect of inclusion of two fat sources: high-oleic acid sunflower seed (HOASS; 0, 50, 100, 150 and 200 g/kg diet) and palm oil (PO), and dietary supplementation of vitamin E (alpha-tocopheryl acetate, 200 mg/kg diet) on performance, fatty acid composition and susceptibility to oxidation of white and dark chicken meat during refrigerated storage. Female chicks (3 to 6 weeks) were given one of 5 diets containing 90 g/kg of added fat with increasing monounsaturated fatty acid (MUFA) content, adjusted by progressively replacing PO by HOASS. 2. Body weight gain and gain:food ratio of birds were depressed in diets containing the highest proportions of HOASS (150 and 200 g/kg). Relative abdominal fat was reduced in birds fed diets including HOASS, except in the diet containing 100 g HOASS/kg. The inclusion of alpha-tocopheryl acetate improved body weight gain and gain:food ratio. 3. According to the fatty acid profile of the diets, saturated and polyunsaturated fatty acid (SFA and PUFA, respectively) contents were significantly reduced and MUFA content was significantly increased in white and dark chicken meats when the saturated oil, PO, was replaced progressively by HOASS in the diet. The inclusion of alpha-tocopheryl acetate increased PUFA content in both meats. 4. After 4 and 7 d of refrigerated storage, white and dark meat samples obtained from birds fed on diets containing HOASS had significantly lower thiobarbituric acid reacting substance (TBARS) values than those derived from the PO diet. The addition of alpha-tocopheryl acetate significantly reduced the lipid oxidation in white and dark meat. 5. Overall, the results showed that increasing MUFA content of chicken meat by replacing dietary PO with HOASS (up to 100 g/kg) did not adversely affect broiler performance and reduced the susceptibility of meat to oxidation during refrigerated storage. Dietary alpha-tocopherol supplementation improved chicken performance and was effective in protecting lipid meat from oxidation.     

Effects of dietary chitosan on fat deposition and lipase activity in digesta in broiler chickens

1. The effect of dietary chitosan on fat deposition and lipase activity in the small intestinal contents was investigated in broiler chickens fed an adequate or high metabolisable energy (ME) diet. 2. Male broiler chickens at 14 d old were fed on the adequate or high ME diet supplemented with 0 or 50 g/kg chitosan, which has a low viscosity, for 3 weeks. 3. Dietary chitosan did not affect food intake, body weight gain or food efficiency in either dietary ME groups. 4. Dietary chitosan reduced the excessive abdominal fat deposition induced by the high ME diet. 5. Dietary chitosan increased the weight of intestinal contents irrespective of dietary ME concentration. 6. Dietary chitosan decreased the lipase activity per g of small intestinal contents. 7. These results suggest that dietary chitosan with low viscosity decreases lipase activity and fat absorption in the small intestine, consequently resulting in a reduction of fat deposition in broiler chickens. 8. It was concluded that dietary chitosan with low viscosity can decrease body fat deposition without reducing food intake and body weight gain in broiler chickens.     

Performance of broiler chicks fed on diets containing urea ammoniated neem (Azadirachta indica) kernel cake.

1. The performance, nutrient utilisation, blood profile, carcase composition, gross pathology and sensory evaluation of meat from broiler chicks fed from 3 to 42 d on diets containing urea ammoniated neem (Azadirachta indica, A.juss) kernel cake (NKC) as a protein supplement to replace peanut meal (PNM), were evaluated. NKC was ammoniated with urea at 15 (UANKC 1) or 25 g (UANKC 2)/kg and incorporated into the test diets to replace either half (134.5 g/kg (L-UANKC 1) and 127.5 g/kg (L-UANKC 2), respectively) or all (269, g/kg (H-UANKC 1) and 255.0 g/kg (H-UANKC 2), respectively) of the nitrogen provided by the PNM. 2. The growth, food intake and efficiency of nutrient utilisation of the birds were comparable between the reference and L-UANKC 1 and 2 diets but were depressed on the other UANKC diets. 3. The retention of dry matter (DM), crude fibre (CF), nitrogen-free extract, total carbohydrate, gross energy, acid detergent fibre, calcium and phosphorus were similar among groups, except lower DM and higher CF and phosphorus retentions were noted in chicks fed on the H-UANKC 1, H-UANKC 2 and L-UANKC 2 diets. All the chicks were in positive nitrogen balance and percentage nitrogen retention did not differ between the reference and test diets. 4. Haemoglobin, total erythrocyte count and aspartate amino transferase activity were unaffected by diet, but total leucocyte count was higher in chicks fed on the H-UANKC 1 and 2 diets and alanine amino transferase activities were lower in chicks fed on the test diets. Blood urea increased as the amount of urea in the diets increased. 5. Most of the physico-chemical carcase characteristics from birds fed on the L-UANKC 2 were comparable to those from birds fed on the reference diet. No bitter taste was noticed in cooked meat from any diet by the sensory panel. 6. Incorporation of L-UANKC 2 was economical and responses were comparable to those observed on the reference diet. 7. It was concluded that NKC detoxified with 25 g urea/kg can economically and successfully replace half the nitrogen of PNM in broiler diets thereby mitigating the chronic shortage of costly oil cakes in developing countries.     

Effects of dietary protein concentration and corticosterone injections on energy and nitrogen balances and fat deposition in broiler chicks

Reducing dietary protein concentration in isocaloric diets consistently decreased nitrogen and energy excretion, and increased dry matter (DM), non-protein DM (NPDM), energy retention and fatness. There were significant correlations, negative between dietary energy-to-protein (E:P) ratio and nitrogen excretion and positive between the E:P ratio and the retention of DM, NPDM and energy. Nitrogen excretion was correlated with energy excretion, and NPDM retention with energy retention. Corticosterone injections increased fatness despite significantly increasing nitrogen and energy excretion. A positive relationship was observed in corticosterone-treated birds between nitrogen excretion on the one hand and the retention of DM and NPDM on the other. Increased food intake because of a low dietary protein concentration was not evident when a sorghum-based diet was used. Moreover, corticosterone injections increased neither the food intake nor the fatness of chicks fed this diet. Decreasing the protein concentration in diets containing identical metabolisable energy (ME) levels slightly, but significantly increased apparent ME values in three out of four experiments. Corticosterone injection did not affect this variable.     

Effects on egg production of including high residual lipid copra meal in laying hen diets

1. The effects on egg production of including copra meals of 220.9 (Copra‐1) and 205.0 (Copra‐2) g residual lipids/kg, in laying hen diets at up to 400 g/kg, were examined in two feeding trials. In a separate experiment, the dry matter retention and ME of a 400 g Copra‐2/kg diet were determined between 6 to 9, 9 to 12 and 12 to 15 d of feeding.

2. Food intakes, egg output and efficiencies of food utilisation (g eggs/g food) of hens fed on Copra‐1 at 100 and 200 g/kg diet were not significantly different from controls; while food intakes at 400 g Copra‐1/kg diet were similar to controls, egg output (6.0% lower), efficiency of food utilisation and body weights of hens were significantly reduced. Hens fed Copra‐2 at 400 g/kg diet had 5.0 and 6.9% lower food intakes and egg output, respectively, and lost body weight compared to controls; however, egg output increased to that of the control group by the 11th week of feeding.

3. Initially, dry matter retention of the 400 g Copra‐2/kg diet was similar to, and ME slightly higher than the control diet; however, both were reduced significantly in the second and third collection periods. The water content of excreta from hens fed on 400 g Copra‐2/kg diet was significantly higher than that from controls.

4. Complete replacement of dietary maize, mainly with copra (experiment 1) led to an increase in pale yolks, with the 400 g Copra‐1/kg diet producing cream‐coloured yolks. Inclusion of maize at 180.6 g/kg of the 400 g Copra‐2/kg diet (experiment 2) resulted in eggs with slightly golden‐yellow yolks.