The egg‐laying response of the domestic hen to variation in dietary calcium

1. Eight diets (1 to 8) containing respectively 36.8, 30.9, 19.6, 9.7, 5.5, 1.9, 0.96 and 0.48 g of calcium/kg food were each fed for 11 weeks to 24 individually‐caged laying hens (Gallus domesticus) aged 24 weeks. After the experimental period, all birds were returned to a normal diet (34.9 g calcium/kg).

2. Food consumption and egg production decreased as dietary calcium decreased. Shell weight was unaffected on diets 1 and 2; on diet 3 there was slight reduction of shell weight and on diets 4 to 8 the reduction was marked. The proportion of calcium in the shell was affected particularly on diets 7 and 8, though those from diet 5 also showed a decreased shell calcium.

3. The values for calcium intake and calcium loss in the egg showed that, generally, birds restricted calcium loss to less than intake. Only on the very low concentrations of calcium (diets 6, 7 and 8) did output appear to exceed input.

4. The main mechanism for controlling calcium loss involves the regulation of the number of eggs produced, i.e. the number of ovulations. Alterations in shell quality are of less importance with respect to calcium balance, although shell strength was impaired on the more restrictive diets (5 to 8).     

The contribution of anorexia to reduced growth in zinc‐deficient chickens

1. It was shown, using a paired‐feeding technique, that the growth depression in zinc‐deficient chicks was largely caused by the greatly reduced consumption of the deficient diet.

2. Chicks receiving a zinc sulphate solution directly into the crop ate an amount of zinc‐deficient diet similar to that of the zinc‐sufficient diet eaten by the control chicks; palatability was thus ruled out as the cause of the anorexia.

3. Only chicks receiving the zinc‐deficient diet displayed signs of zinc deficiency.     

Antimicrobial substances and chick growth promotion: The growth‐promoting activities of antimicrobial substances,including fifty‐two used either in therapy or as dietary additives

1. Fifty‐five antimicrobial substances were tested for their ability to promote growth when added to the diet of chicks.

2. Both cephalosporins and all the nine penicillins tested were active.

3. Of six aminoglycosides, streptomycin and gentamicin had the greatest activity and neomycin had none.

4. Growth rate was significantly improved by clindamycin, lincomycin, vancomycin, spectinomycin, rifampicin, oxytetracycline, chlortetracycline, erythromycin, tylosin, flavomycin, virginiamycin and zinc bacitracin. Chloramphenicol and nalidixic acid were inactive. Polymixin B, novo‐biocin, cycloserine, phosphonomycin, and sodium fusidate had little activity. Fusidic acid promoted growth at 250 mg/kg diet.

5. Trimethoprim was inactive alone and in combination with sulpha‐diazine. Of seven 5‐nitroimidazoles, only dimetridazole and metronidazole showed slight activity. Of the six 5‐nitrofurans, only nitrovin, the standard reference substance used, promoted growth.

6. Caprylohydroxamic acid, a urease inhibitor, had no beneficial effect on growth rate or on the efficiency of food conversion.

7. The growth‐promoting properties of the various substances could not be related with their known antimicrobial and absorption characteristics in mammals.     

Effects of dietary protein content,addition of nonessential amino acids and dietary methionine to cysteine balance on responses to dietary sulphur‐containing amino acids in broilers

1. Two experiments were conducted with male broiler chicks from 2 to 5 weeks of age to determine the effect of dietary protein content and amino acid balance on the response to dietary sulphur‐containing amino acids (SAA) in terms of performance and carcase quality.

2. In experiment 1, 5 graded amounts of a DL‐methionine and L‐cysteine (1:1 by weight) mixture were added to basal diets containing 197 or 233 g crude protein/kg. The diets containing 197 g protein/kg were fed with or without the further addition of 36 g crude protein/kg from nonessential amino acids. The amino acid balance of all diets was kept constant for all essential amino acids except the SAA. In experiment 2, 5 graded amounts of SAA from either a crystalline source (DL‐methionine or a mixture of DL‐methionine and L‐cysteine) or from intact proteins were added to a diet containing 208 g protein/kg.

3. At each protein concentration there were significant responses to the SAA addition in weight gain, food conversion efficiency, and carcase quality. Non‐linear exponential regression analyses were used to describe bird responses to SAA concentration. The broiler chick's requirement for SAA increased with increasing dietary protein concentrations ranging from 197 to 259 g protein/kg.

4. The utilisation of SAA differed also with differences in origin (crystalline or peptide‐bound), and methionine:cysteine balances. Compared to DL‐methionine, a 1:1 mixture of DL‐methionine and L‐cysteine was only 81% or 86% as effective in supporting growth or food conversion, respectively. SAA from added protein was even less effectively utilised.

5. The addition of nonessential amino acids tended to decrease food intake without affecting SAA utilisation.

6. Slaughter yield and breast meat yield were clearly increased while fat deposition was clearly decreased, by SAA addition. The response in breast meat yield suggested an important economic benefit for further meat processing. Nitrogen retention was significantly enhanced by SAA supplementation from crystalline sources, and this led to reductions of up to 30% in the amount of nitrogen excreted per kg weight gain.     

Growth,viscosity and beta‐glucanase activity of intestinal fluid in broiler chickens fed on barley‐based diets with or without exogenous beta‐glucanase

1. Three groups of birds were fed for up to 35 days on diets containing 500 g barley (cv. Condor) /kg diet, with or without exogenous β‐glucanase, either a commercial preparation or a recombinant endoglucanase.

2. Birds which received diets containing the exogenous enzymes grew faster for the first 3 weeks but after that there was no apparent difference in rate of growth.

3. β‐Glucanase activities in the crop and small intestine of birds given exogenous enzymes were generally higher than those of birds given only the basal diet.

4. Viscosity of intestinal fluid in birds given only the basal diet decreased with age but there was no corresponding increase in β‐glucanase activity. This discounts bacterial β‐glucanase as a contributory factor in the adaptation to β‐glucanase apparent in older birds.     

Interaction between dietary 1,25‐dihydroxycholecalciferol and calcium and effects of management on the occurrence of tibial dyschondroplasia,leg abnormalities and performance in broiler chickens

1. Two experiments were performed to compare the relative effectiveness of feeding 1,25‐dihydroxycholecalciferol (1,25‐DHCG) in minimising leg abnormalities in broilers with other methods and to investigate interactions between dietary 1,25‐DHCC and calcium.

2. Adding 5 μg 1,25‐DHCC/kg to a diet containing 12 g calcium/kg was more effective than early food restriction or meal feeding in preventing leg abnormalities but was found to cause a growth depression.

3. The second experiment, which had a factorial design, with diets containing 7.5, 100 and 12.5 g calcium and 0, 2.0, 3.5 and 5.0 μg 1,25‐DHCC/kg, showed linear and quadratic interactions between these dietary factors. Diets with higher concentrations of both 1,25‐DHCC and calcium resulted in growth depression associated with hypercalcaemia.

4. The incidence of tibial dyschondroplasia (TD) at 3 weeks of age was highest with the basal diet containing 7.5 g calcium/kg and was markedly reduced by addition of 1,25‐DHCC and/or calcium. The incidence was very low or non‐existent when 1,25‐DHCC was fed at 3–5 μg/kg or greater.

5. Feeding 5 μg/kg 1,25‐DHCC had no effect on plasma 1,25‐DHCC concentrations, although at the higher dietary calcium contents plasma concentrations of 25‐hydroxy‐ and 24,25‐dihydroxy‐cholecalciferol were lower in those birds fed 1,25‐DHCC.

6. It is concluded that 1,25‐DHCC is most effective in preventing TD without accompanying growth depression when it is fed in conjunction with diets containing less than 10 g calcium/kg.     

Effects of male body weight,strain and dietary protein content on fertility and musculo‐skeletal disease in naturally mated broiler breeder males

1. The effects of male body weight at mating and different rates of gain on overall fertility were studied in two strains of broiler breeder males fed on a diet containing 160 or 120 g crude protein/kg. Sexual activity, musculo‐skeletal disease and culling were also assessed.

2. There were no differences in early fertility between males weighing 3–0 or 3–5 kg at the start of the mating period, or between males gaining 1.0 or 1.5 kg body weight from mating to 60 weeks of age.

3. There were no differences in fertility between males fed on the two diets differing in crude protein content.

4. One strain of male had lower fertility than the other and this was associated with a greater weight of breast muscle, lower frequency of observed copulations and a higher number of incompleted matings.

5. Sexual activity declined and the number of spermatozoa trapped on the perivitelline membrane increased with age.

6. There were no differences among the treatments in the prevalence of musculo‐skeletal lesions (destructive cartilage loss). As a proportion destructive cartilage loss occurred in 0^‐67 of the males at 66 weeks of age. Degeneration of the antitrochanter was present in 3 of 50 females examined and a cartilage flap in the medial condyle of the tibiotarsus occurred in 15 of these birds.

7. Beak lesions were the most important cause of male culling which averaged 0–24 as a proportion of the males at the start of the experiment.     

Effects of dietary electrolyte balance and addition of electrolyte–betaine supplements in feed or water on performance,acid–base balance and water retention in heat-stressed broilers

1. The effects of dietary electrolyte balance (DEB) and electrolyte–betaine (El-Be) supplements on heat-stressed broiler performance, acid–base balance and water retention were evaluated during the period 31–40 d of age in a 2 × 3 factorial arrangement of treatments.

2. A total of 240 broilers were assigned to 6 treatment groups each with 8 replicates of 5 birds per cage and were exposed to cyclic high temperature (32 – 24 ± 1°C). Birds were provided with diets having DEB of either 180 or 220 mEq/kg. El-Be supplements were either added to the diet, water or not added to either of them to complete the array of 6 treatment groups.

3. An additional 80 birds were kept at thermoneutral temperature (20 ± 1°C) and were provided with tap water and diets with DEB of either 180 or 220 mEq/kg to serve as negative controls.

4. Exposure to high temperature depressed growth performance, increased rectal temperature and decreased potassium (K⁺) retention. In high-temperature room, birds fed on diets with DEB of 220 mEq/kg tended to increase BW from 35–40 d of age. However, at thermoneutral temperature, broilers fed on diets with DEB of 220 mEq/kg increased K⁺ retention.

5. Adding El-Be supplements in feed or water improved feed conversion ratio (FCR), enhanced water consumption and increased K⁺ and sodium (Na⁺) retention.

6. Interactions between DEB and El-Be supplements tended to affect body weight gain and FCR during the periods 35–40 and 31–40 d of age, respectively. It is suggested that when using a diet with DEB of 180 mEq/kg, adding the El-Be supplements in drinking water was more beneficial than in feed. Adding the supplements in feed or water was equally useful when using DEB of 220 mEq/kg.

     

Responses in growth,food intake and food conversion efficiency to different dietary protein concentrations in meat‐type lines of Japanese quail

1. A total of 360 Japanese quail of 4 commercial meat‐type lines and two diet treatments (260 and 216 g/kg or 238 and 195 g/kg of crude protein (CP) in the starter and grower diet, respectively) were used.

2. The positive effect of a high CP diet on body weight was significant only for the first 4 weeks after hatching.

3. The mean age at inflection point of the growth curve (t ⁺) across lines and sexes was 1.4 d (0.6 to 2.8 d within line/sex groups) earlier for quail fed on a high CP diet than in quail receiving a low CP diet. The inflection (y ⁺) and asymptotic (A) weights were similar under both dietary protein concentrations. Nevertheless, the shape of the growth curve, characterised by the ratio y⁺1A and parameter of the maturing rate k, was significantly influenced by diet.

4. A higher food intake and less efficient food conversion were found for quail fed on a high CP diet in the period from 15 to 28 d of age.

5. The fattening traits such as body weight, cumulative food intake and food conversion, were not affected by dietary CP content at the age of 5 weeks.

6. The effects of line on body weight, food intake and food conversion are discussed.     

Interactions between dietary fat type and xylanase supplementation when rye‐based diets are fed to broiler chickens 2. Performance,nutrient digestibility and the fat‐soluble vitamin status of livers

1. The interactions between dietary fat type and xylanase supplementation of rye‐based diets were investigated using a 2×2 factorial design in which a rye‐based diet (610 g rye/kg) was combined with 100 g/kg of soya oil or beef tallow, with or without xylanase supplementation at 3000 IU/kg, and fed to 1‐d‐old male broilers for 35 d. Growth, nutrient digestibility and AMEn values were determined and the vitamin status of livers assessed at various ages.

2. There were significant interactions between crude fat and xylanase supplementation on the faecal digestibility of crude fat and crude protein. Fat digestibility was improved by xylanase in both fat type groups but to a greater extent for the tallow diets. However, the effects were found to be significant only for oleic, linoleic and linolenic acids. Similarly, protein digestibility and AMEn values were significantly improved by xylanase, but only for the tallow diet.

3. Heal digestibility of nitrogen and amino acids also were affected by enzyme for both fat type diets, the effect generally being more pronounced for the tallow diet.

4. The deposition of the fat soluble vitamins A and E in livers was significantly increased by xylanase supplementation and was also better for soya oil than for tallow.

5. Xylanase supplementation increased the digestibility of insoluble pentosans whereas for the soluble pentosans the opposite effect was noted.

6. Without xylanase supplementation the tallow‐based diet caused high mortality. Liveweight gain and the efficiency of food utilisation were greatest in the soya oil‐based, xylanase‐supplemented diet, followed by the unsupplemented soya oil‐, supplemented tallow‐ and unsupplemented tallow‐based diets.     

Induced moulting in cockerels: Effects on sperm production,plasma concentrations of luteinising hormone,testosterone and thyroxine,and on pituitary sensitivity to luteinising hormone‐releasing hormone

1. The ability of a moult‐inducing procedure to restore high levels of sperm production was assessed, in two experiments, using cockerels with reduced sperm production. The moulting procedure consisted of a period of food and light restriction for 6 weeks. The moulted birds were compared with control birds for 20 weeks.

2. Moult induction resulted in decreased daily sperm output (DSO) and plasma testosterone concentration, from weeks 3 to 7. In the first experiment, plasma luteinising hormone (LH) concentration in moulted birds was reduced on week 5.

3. No change in pituitary sensitivity to chicken luteinising hormone‐releasing hormone‐I (cLHRH‐I) was detected at week 3 in moulted cockerels. In moulted birds, a transient increase in plasma thyroxine concentration was detected.

4. After the end of moult induction, testosterone concentrations increased, plasma LH showed a rebound at week 7 and the pituitary sensitivity to LHRH was increased at week 9.

5. This increased activity of the pituitary‐testicular axis resulted for a short time in an increase in DSO of moulted birds compared with that of controls. Although amelioration was moderate, this result indicates the possibility of improving sperm production in the cockerel by using an induced moulting procedure.     

Effects of endotoxin,interleukin‐1/3 and prostaglandin injections on fever response in broilers

1. The effect of endotoxin, interleukin‐1β and prostaglandin on fever response was studied in 80 broilers (Hubbard strain). Endotoxin (E. coli, LPS) was injected iv (1.5 μg/kg) and icv (1.5 μg/bird); interleukin‐1 (human recombinant IL‐1β, 80 pg/bird) and prostaglandin E₂ (5 μg/bird) were injected icv. Indomethacin (10 mg/kg, iv) pretreatment was also used before iv endotoxin injection.

2. The results showed that indomethacin was able to block the fever response induced by iv endotoxin injection, and IL‐1β and PGE₂ were both effective in producing fever when injected icv. These data suggest a prostaglandin‐mediated fever response by broilers, and also a strong evidence of the involvement of endogenous pyrogen (interleukin‐1) in fever response in birds.     

Effects of force‐feeding and dietary cereals on gastrointestinal size,intestinal absorptive ability and endogenous nitrogen in ducks

1. Gastrointestinal size, intestinal absorption of glucose and L‐methionine, and intestinal endogenous nitrogen in Pekin ducks were measured after the birds were subjected to force‐feeding with excessive amounts of a diet based on maize or barley for 12 d.

2. Force‐feeding significantly increased the weight and area of the crop, the weight of the proventriculus, the length and area of the jejunum and ileum, but decreased the weight of the gizzard and the thickness of its caudodorsal thick muscle. Feeding a barley‐based diet also decreased the thickness of caudodorsal thick muscle of gizzard.

3. Force‐feeding enhanced the absorption rates (μmol/cm²) of glucose and L‐methionine in both jejunum and ileum. Ducks fed on a maize‐based diet showed a slightly higher absorption rate of glucose compared to those fed on a barley‐based diet.

4. Force‐feeding caused a significant increase of endogenous non‐protein nitrogen (μg/cm²/h) in both jejunum and ileum and a slight increase of endogenous protein nitrogen in the jejunum.     

The effect of rotational grazing for periods of one or two weeks on the build‐up of lungworm and gastrointestinal nematode infections in calves

Summary

An experiment was carried out with three groups of grazing calves and one housed control group to study the effect of rotational grazing for periods of 1 and 2 weeks on the build up of lungworm and gastro‐intestinal nematode infections respectively. The experiment demonstrated that rotational grazing for periods of I week on six plots prevented the build‐up of heavy lungworm infections. A buildup of heavier lungworm infections was observed in a group that was rotationally grazed for periods of 2 weeks on three plots and a group which remained on one plot throughout the grazing season; there was no difference between these two groups. In all three situations, there was an adequate development of immunity against D. viviparus, as measured by worm recovery after challenge infection at the end of the experiment in comparison with worm recovery of the similarly challenged control group. Neither rotational grazing scheme protected the calves against gastrointestinal helminthiasis, because tracer calves, which grazed for 4 days only in August or October, acquired infections which would have resulted in severe illness or even death if necropsy had been postponed for a week.     

Sero‐epidemiological screening of pig sera collected at the slaughterhouse to detect herds infected with Aujeszky's disease virus,porcine influenza virus and Actinobacillus (Haemophilus) pleuropneumoniae in the framework of an Integrated Quality Control (IQC) system

Summary

Over a period of six months, approximately 4700 blood samples were collected from 97 pig‐finishing farms in the provinces of Noord‐Brabant and Gelderland and screened for antibodies with respect to Aujeszky's disease virus (ADV), porcine influenza virus (PI) and Actinobacillus (Haemophilus) pleuropneumoniae (App). There were significant differences in the percentages of seropositive pigs between the two provinces, which may be related to the difference in the density of the pig population in the two provinces.

In practice, it was possible to perform a reliable sera collecting procedure at the slaughterhouse. No farms remained seronegative with respect to most of the disease agents during the sampling period. There was a high degree of variation in the percentages of seropositive pigs per farm as to most of the disease agents. Evidence was found that animals that were seropositive with respect to ADV were significantly more susceptible to becoming seropositive with respect to App. serotype 2, and vice versa. The same connection was observed for PI serotype H₁N₁ and PI serotype H₃N₂. Furthermore, evidence was found that pigs seropositive with respect to PI serotype H₁N_i only, or to PI serotype H₁N₁ and ADV or PI serotype H₃N₂ show a significant decrease in average daily weight gain compared to pigs that were seronegative.