G. De Groote

Ideal amino acid profile and dietary lysine specification for broiler chickens of 20 to 40 days of age

1. The aim of the study was to determine the ideal ratio of the essential amino acids lysine (Lys), methionine (Met), threonine (Thr), tryptophan (Trp), arginine (Arg), valine (Val) and isoleucine (Ile) and to assess the required dietary lysine concentration for optimum performance in broiler chickens of 2 commercial strains from 20 to 40 d of age. 2. An identical basal diet was used throughout all experiments. It consisted mainly of maize and soyabean meal and contained 172 g crude protein and 13.2 MJ AME(N) per kg. For each experiment, the basal diet was adequately supplemented with all essential amino acids except the one to be tested, which was supplemented in 6 graded concentrations in exchange for maize starch. One (Met, Trp, Arg, Val, Ile) or 2 (Lys, Thr) growth trials were conducted per amino acid tested and the response in weight gain, food: gain ratio, breast meat yield and abdominal fat were examined. 3. The ideal amino acid ratio relative to Lys (expressed as a percentage) was calculated to be 75% Met+Cys, 63% Thr, 19% Trp, 112% Arg, 71% Ile and 81% Val on a true faecal digestible basis when the data were subjected to broken-line regression analysis. From both lysine studies the concentration for optimum food: gain ratio was calculated, by exponential regression analysis, to be 11.5 g true faecal digestible lys per kg diet.

EFFICACY OF HEAT-INACTIVATED HEPATITIS B VACCINE IN HAEMODIALYSIS PATIENTS AND STAFF: Double-blind Placebo-controlled Trial

The efficacy of a heat-inactivated hepatitis B vaccine, 3 micrograms of surface antigen (HBsAg), given at 0, 1, 2, and 5 months, was evaluated in 401 haemodialysis patients in 18 centres by a placebo-controlled, double-blind, randomised trial. The attack-rate of hepatitis B virus (HBV) infections in the control group was 18% over 435 days. The protective efficacy rate of the vaccine was 78% against all HBV infections in the entire study (p = 0.00016), and 94% against HBsAg-positive hepatitis more than 3 months after day 0. Those patients in whom HBV developed showed no evidence of vaccine-acquired anti-HBs. Among 152 similarly randomised staff members receiving three monthly injections, all 5 HBsAg-positive infections occurred in the placebo group (p = 0.022). The vaccine induced anti-HBs in 88% of the patients and 100% of the staff. Immediately after the fourth injection, anti-HBs levels were as high in responding patients as in staff. There were no serious side effects. In the four-dose schedule the vaccine provides dialysis patients with protection of the same order as that given by other hepatitis B vaccines to normal subjects.

Early and temporary quantitative food restriction of broiler chickens. 2. Effects on allometric growth and growth hormone secretion

1. An experiment was conducted with male broiler chickens to investigate the effect of different early food restriction programmes on proportional weights and allometric growth coefficients of carcase parts and on pulsatile growth hormone secretion. 2. At 4 d of age the animals were restricted to 80% or 90% of the ad libitum intake for 4 d or 80% for 8 d. When the restriction was finished, all birds received ad libitum food again. 3. On d 1, 8, 11, 14, 21, 28, 35 and 42, from each group 8 birds were weighed, stunned and killed and the weights of the stomachs, liver, heart, sternum, right thigh, right drumstick, breast and abdominal fat pad were determined. On d 29, 30, 31, 32 serial blood samples of 2 birds from each group were taken to determine the plasma growth hormone (GH) content. 4. Only the most severe restriction resulted in a tendency for the stomachs to mature earlier and the thighs to mature later. No other significant effect on the allometric coefficients could be observed. 5. It is concluded that during the restriction the birds give priority to the development of the supply organs such as the stomach, which are more important during early development, at the expense of the demand tissues like breast and thigh. 6. No significant differences concerning the GH secretory parameters could be observed.

A comparison of a new net energy system with the metabolisable energy system in broiler diet formulation, performance and profitability 1

Synopsis Two trials were conducted with unsexed broilers to compare a net energy (NE) system and a metabolisable energy (ME) system on least‐cost broiler diet formulation, broiler performance and economic efficiency. Both energy systems were compared in the range of 3000 (2161) to 3400 kcal ME/kg (2560 kcal NE/kg) using rations with increasing energy concentration of about 100 kcal/kg food. The two different energetic evaluation systems had considerable effect on dietary composition, the penalty cost of rejected ingredients, the marginal profit of some limiting constraints and the position of the least‐cost nutrient concentration. The starter and finisher rations, based on NE values, were on average 4.77 and 2.43 BF2/100 kg cheaper, respectively than those based on ME values. For equal NE contents, they contained 50 to 70 kcal less ME/kg and 1% less crude protein. The broiler performances were on average better on the NE‐diets. The mean difference of 20 to 30 g in body weight was significant at 4 and 6 we...

A marginal income and cost analysis of the effect of nutrient density on the performance of white leghorn hens in battery cages 1

Synopsis In an experiment lasting 40 weeks with 576 caged White Leghorn (WL) hens and using linearly programmed least‐cost rations, the influence of increasing the nutrient density by increments of 100 kcal metabolisable energy (ME)/kg food, within the range 2500 to 3200 kcal ME/kg, on production was studied. Increasing the nutrient density was accompanied by increases in egg weight, body weight and ME intake/hen d but mortality and the number of eggs laid were not affected (P<0.01). From a regression analysis carried out on the combined results of this and of another similar experiment, it was found that with each 100 kcal/kg rise in the ME content, the mean ME intake/hen d increased by 3.14 ± 0.59 kcal, the body weight by 38.85 ± 10.7 g and the egg weight by 0.21 ± 0.04 g. A marginal income and cost analysis, using the above data, was carried out for three price situations of raw materials in 1970 and for two price situations of eggs and carcasses. The rations had a marginal cost structure for each nutr...

The efficiency of nitrogen retention during compensatory growth of food-restricted broilers

1. Two experiments were conducted to investigate the influence of compensatory growth, induced by early quantitative food restrictions, on the efficiency of nitrogen-retention in two lines of Ross broilers. 2 . Birds were restricted to 80% of the ad libitum intake of the previous 24 h of the control group from d 4 to d 7. After the period of restrictions all birds were fed ad libitum . 3 . In both trials, the final body weight of the restricted Ross 208(308) birds was similar or even higher than that of the control group. For the Ross 508 line, compensatory growth was substantial in the first trial, but non-existent in the second trial. In all cases, the mortality of restricted birds was lower than in control birds. 4. Not only environmental factors, but mainly chick quality, seemed to have a major influence on the capacity of the chickens to establish compensatory growth. 5. As compensatory growth was established, some improvement in N retention was induced. Although differences were not significant, they may be environmentally important. 6. It is concluded that a retardation of the early growth of fast growing broiler chickens can, in certain circumstances, reduce mortality and increase performance and N retention.

Optimum isoleucine requirement of laying hens and the effect of age

1. Medium weight laying hens were used for an assay to determine their isoleucine requirement between 26 and 36 weeks of age and again between 46 and 56 weeks of age. 2. Two isoleucine-limiting mixtures were formulated with similar amino acid profiles, one containing 198 g and the other 110 g crude protein per kg diet. These mixtures were blended to give a series of 11 diets with isoleucine contents ranging from 7.6 to 3.8 g/kg. The lowest protein diet was also fed with a supplement of L-isoleucine. Each of the 12 diets was given to 5 groups of 24 laying hens. 3. The daily isoleucine requirement of individual laying hens was estimated to be 9.48 mg/g egg output plus 44.47 mg/kg body weight per day for the 1st period and 12.11 mg/g egg output plus 6.86 mg/kg body weight per day for the 2nd period. Calculated optimum intakes of isoleucine for various ratios of cost of input to value of output are tabulated. For example, for a flock of medium weight hens producing an average of 50 g daily egg mass, the optimum isoleucine intake (mg/hen d) varied between 760 and 890 varying for ratios of costs to egg prices. 4. It is concluded that the isoleucine required per day does not decrease during the first laying year despite a decrease in rate of egg output.

Early body‐weight selection of broiler breeder males in relation to reproductive and growth performance of their offspring

1. The effectiveness of selection of broiler breeder males for body weight at 3 weeks of age on later growth, semen quality and performance of progeny has been tested. 2. Correlation between 3- and 20-week body weights in the breeders was poor but significant. 3. On the basis of 3-week body weight males were divided into heavy birds (mean + 0.5 standard deviation) and all birds. 4. Semen quality was not different between the two groups, but some selection for semen quality was practised within groups. 5. There were no differences in fertility and hatchability of eggs produced from hens artificially inseminated with diluted, stored semen from both groups. 6. There was a small, positive, but non-significant, effect of selection of breeder males on body weight of progeny at 6 weeks of age.

Effect of plumage renewal after induced moulting on subsequent laying efficiency and persistence.

1. Brown egg layers and dwarf broiler breeder females were force-moulted by different diets. The relationship between the extent of feather replacement and subsequent laying performance was studied. Some brown hens were subjected to metabolic experiments in order to compare post-moult heat production in relation to moulting success. 2. The extent of moulting had a clear effect on the post-moult heat production, and the differences were still present after 6 months in the second year of laying. 3. The extent of feather renewal during moulting showed high and very significant rank correlations with efficiency of food utilisation during the subsequent laying cycle. These correlations were generally higher than those of other features of the moulting procedure (body-weight-loss, minimum weight, duration of pause in laying). 4. The long-term energetic implications of the extent of moulting play an important role in subsequent performances and the persistence of lay during the following year is related to the extent of feather replacement.

Efficacy of heat-inactivated hepatitis B vaccine (CLB) in dialysis units

The immunogenicity and safety of a heat-inactivated hepatitis B vaccine (CLB) was evaluated in 471 seronegative low-risk volunteers and 227 haemodialysis patients, treated in hepatitis B-free dialysis centres. Of 202 healthy low-risk volunteers who recieved three doses of 3 lag heat-inactivated HBsAg at intervals of I month, 42% developed anti-HBs within 1 month, 84% within 2 months and a total of 93~ within 5 months after the first injection of the vaccine. A second randomized study in which the immunogenicity of different dosages of HBsAg was compared in 269 volunteers, showed that decrease of the vaccine dose from 3 lag to 1.5 I.tg, 0.6 lag and 0.25 lag did not decrease the anti-HBs response, neither with regard to the proportions of anti-HBs responders (88-91~), nor with regard to the anti-HBs titres of the vaccinees. However, when the dose was decreased to 0.1 lag the anti-HBs response dropped significantly to 63% (P < 0.001). The difference in anti-HBs response between male and female recipients of 3-lag doses of the vaccine was negligible and the anti-HBs response was not age-related; only in males the younger vaccinees tended to develop higher anti-HBs titres than the older ones. In a third randomized trial, 227 haemodialysis patients were immunized at monthly intervals with either three doses of 3 lag or three doses of 27 lag hepatitis B vaccine. At 5 months after the first injection, 77~ of the patients in the 3-lag group and 94% in the 27-lag group had developed anti-HBs. At month 12, the proportions of anti-HBs responders in the 3-lag and the 27-lag group had dropped to 68~ and 87%, respectively. These results show that the impaired immune reactivity of haemodialysis patients to hepatitis B vaccines can be overcome by increasing the dose of the vaccine. In none of the vaccinees the reaction on HBsAg and/or anti-HBc became positive and in none of the vaccinees induction of autoantibodies, associated with autoimmune liver disease (ANA, AMA, SMA, LMA and LSPA), could be demonstrated after vaccination. These studies in low-risk volunteers and haemodialysis patients have revealed that the heat-inactivated hepatitis B vaccine (CLB) is safe and highly immunogenic.