Comparative development of digestive organs,intestinal disaccharidases and some blood metabolites in broiler and layer‐type chicks after hatching

1. Body weight, digestive organ weights, and activities of disaccharidases (maltase and saccharase) activities were determined from day of hatch to 21 d of age in meat‐ and egg‐type chickens. Blood plasma was analysed for enzyme activities and metabolite concentration.

2. In meat‐type chickens food intake and growth rate were about 3‐fold those in egg‐type chickens. Food efficiency was superior in meat‐type chickens throughout the experimental period.

3. Meat‐type chickens hatched with disaccharidase activities exceeding those found in their egg‐type counterparts 2‐ to 5‐fold. From 7 d of age on, this trend reversed, i.e. activity was much higher in egg‐type than in meat‐type chickens.

4. Blood plasma amylase activity increased gradually in meat‐type chickens and was higher than in egg‐type chickens to 14 d of age. No breed differences were observed for alkaline phosphatase or lactate dehydrogenase activities during the experimental period.

5. Blood plasma concentrations of total protein, albumin, glucose, and calcium, were lower in meat than in egg‐type chickens.     

Cage size and flooring preferences in litter‐reared and cage‐reared hens

1. Pullets (Ross Rangers) reared commercially either in cages or on deep litter were tested for their responses to small (0.38 × 0.43 m) and large (0.76 x 0.86 m) cages with wire floors and to small and large cages with litter floors.

2. When tested at 29 weeks of age, the birds' responses were significantly affected both by cage size (large preferred to small) and by flooring (litter preferred to wire).

3. No difference in cage preference was apparent between cage‐reared and litter‐reared birds either when they were first tested at 17 weeks or when they were re‐tested at 29 weeks. Birds do not have to be reared on litter in order to be attracted by it.     

Comparison of post‐hatch holding time and subsequent early performance of broiler chicks and Turkey poults

1. The effect of a holding period, lasting up to 48 h post‐hatch, on early growth and mortality rate was studied in broiler chicks and turkey poults.

2. After 48 h of food and water deprivation, birds of both species lost about a tenth of their initial post‐hatch weight. Weight loss was more marked in poults subjected to heat stress. Thus, duration of the holding period adversely affected early growth.

3. During the 48‐h holding period, the relative weight of residual yolk decreased in both species by approximately half of its weight in the just hatched chicks and poults. Relative yolk size was much higher in poults than in broilers.

4. On day 1 weight loss was attributed to degradation of the yolk sac, whereas on day 2 only about two‐thirds of the loss could be attributed to residual yolk. Body composition of newly‐hatched broiler chicks did not differ from those held for 24 h despite shortages of energy. However, after 48 h body fat content was markedly reduced compared to newly‐hatched or 24‐h‐old birds.

5. Irrespective of access to food, the relative size of the gastrointestinal tract increased with holding time in both species, reflecting its importance.

6. It was concluded that post‐hatch birds deprived of food and water for 48 h face a severe shortage of energy, causing alterations in body composition. This in turn adversely affects early growth and increases mortality rate under heat stress.     

Influence of diet on the intestinal microflora and meat flavour of intensively‐reared broiler chickens

1. An attempt has been made to modify the composition of the gut flora of broiler chickens by dietary means in order to determine any concurrent changes in meat flavour.

2. Birds given a diet containing an increasing proportion of whole wheat supplemented with fresh green vegetable matter (special diet) were compared with conventionally‐fed controls. At 12 weeks of age those receiving the special diet had 10 to 100‐fold higher counts of Escherichia colt and faecal streptococci in the duodenum and lower small intestine and showed differences in the intestinal incidence of species and biotypes of lactobacilli.

3. Evaluation of cooked breast‐meat samples by a trained sensory panel showed a significant difference in flavour (P < 0.01) between conventional and special‐diet birds which varied from perceptually very slight to slight. The main terms used in distinguishing special‐diet birds from conventional controls included ‘richer’, ‘meatier’ and ‘sweeter’.

4. Storage of plucked, uneviscerated birds at 4 °C for 8 d maintained the flavour difference between the dietary groups but the effect of storage on flavour was greater in both groups of birds than the influence of diet alone. The likely influence on flavour of autolytic changes occurring in the muscle during storage of the birds is discussed.     

Response of broiler chicks to threonine‐supplemented diets to 4 weeks of age

1. Two experiments were carried out to determine the response of broiler chicks to threonine‐supplemented diets between 10 and 28 d and 7 and 21 d of age, respectively.

2. In the first experiment female broiler chicks were fed on 11 experimental diets. Two iso‐energetic basal diets (diets 1 and 2) were prepared with 200 and 160 g CP/kg and 7·6 and 6·0 g threonine/kg respectively. Both diets contained 11·5 g lysine and 8·7 g sulphur‐containing amino acids/kg. Diet 3 was composed of diet 2, supplemented with all essential and non‐essential amino acids (EAA and NEAA, respectively) except threonine, to the concentrations of the amino acids in diet 1. The NEAA were added as a combination of glutamic acid and glycine. Diets 4 to 11 had the same compositions as diet 3, but contained increasing amounts of threonine.

3. For birds fed on diet 2, gain was significantly lower and food/gain ratio was significantly higher than for birds fed on diet 1. Supplementation with EAA, NEAA and threonine to the same concentrations in diet 1 resulted in a performance similar to that found on diet 1.

4. In experiment 2, male and female broiler chicks both received 10 experimental diets. Diet 1 contained 220 g CP/kg and 8.5 g threonine/kg, diet 2 contained 160 g CP/kg from natural raw materials and 6 g threonine/kg. Both diets contained 12·4 g lysine and 9·3 g sulphur‐containing amino acids/kg. Basal diet 2 was supplemented with all EAA and NEAA to the concentrations of basal diet 1, except for threonine. Diets 3 to 10 had the same compositions as the supplemented diet 2, but contained increasing amounts of threonine.

5. For male and female chicks on diet 2, gain was significantly lower and food/gain ratio significantly higher than those on diet 1. Diet 10 (160 g CP/kg plus all EAA, including threonine, and NEAA supplemented to the concentrations of diet 1) resulted in the same performance as diet 1.

6. The results indicate that, when low protein maize‐soyabean meal diets supplemented with EAA and NEAA with 13·31 MJ ME/kg were fed to male and female broiler chicks until 21 d of age, improvements in gain and food/gain ratio were obtained when the dietary threonine content was increased to 7·25 g/kg. When female chicks were fed threonine‐supplemented diets to 28 d of age, improvement in gain and food/gain ratio was obtained when the threonine concentrations were increased to 6·32 g/kg diet.

7. Curves have been fitted to the data, from which a cost‐benefit analyses can be made and an optimum threonine dose calculated, using local prices.     

Dietary chloride requirement of broiler chicks fed on a wheat‐soyabean diet

1. A diet based on soyabean meal and wheat contained insufficient chloride to support normal growth in chicks.

2. Ammonium chloride and sodium chloride were equally good sources of supplementary chloride for the chick.

3. When seven diets providing increasing proportions of chloride from 608 to 1808 mg/kg, were fed to chicks, maximal growth at 21 d was obtained at about 1200 mg chloride/kg diet.     

Growth and the plasma concentrations of growth hormone and prolactin in chicks: Effects of “environmental enrichment”, sex and strain

1. The effects of including novel objects in the environment ("environmental enrichment “) on body‐weight gain, relative body‐weight gain, gain : food ratio, plasma growth hormone (GH) and prolactin concentrations in male and female broiler and layer chicks was investigated.

2. Environmental enrichment improved body‐weight gain, relative body‐weight gain and gain: food ratio but had no effect on circulating GH or prolactin concentrations.

3. Weight gain and gain : food ratio were greater in the broilers than in the layer chicks, while plasma GH and prolactin (females only) concentrations were less.

4. There were no sex differences in weight gain and relative weight gain but gain : food ratio was significantly greater in females than in males. In both strains plasma GH concentrations were higher in males than in females and prolactin concentrations were higher in male than in female broilers.     

Differential effect of age on metabolisable energy content of high protein‐low energy and low protein‐high energy diets in young broiler chicks1

1. An experiment was carried out with 6‐d old male broiler chicks in an attempt to understand better the effect of age on dietary AME_n of high protein‐low energy (HPLE) and low protein‐high energy (LPHE) diets which are used in the determination of the AME_n content of grains when substituted for the entire diet. The experiment was carried out in a split‐plot design in which the effects of 2 diets (HPLE‐reference and LPHE‐test, containing maize) on food intake, faecal excretion, dietary AME_n and the utilisation of the nutrients were evaluated in 3 age periods (A = 11–13, B = 15–17 and C = 20–22 d of age).

2. Chicks fed on the HPLE diet consumed significantly less food than those fed on the LPHE diet during periods A and B, but not in G. They also produced a significantly larger amount of droppings during periods B and C. Food‐to‐droppings ratio, which was consistently and significantly lower in chicks fed on the HPLE diet, decreased markedly in period C only in these birds.

3. Absolute and relative retention (RR) of dry matter (DM) and starch, and RR of nitrogen (N) from birds fed on the HPLE diet, were consistently and significandy lower than from those fed on the LPHE diet, but fat retention (absolute and relative) was higher. RR of DM and of N in period C was significantly lower than in periods A and B, while RR of fat and of starch was not affected by age. The effect of age on RR of N was observed only with the HPLE diet.

4. AME_n of the HPLE diet, but not of the LPHE diet, in period C was significandy lower than in periods A and B, resulting in a significant interaction between age and diet and a general reduction with age. The calculated AME_n contents of the maize in periods A and B were essentially the same (14.91 and 14.85 MJ/kg, respectively), and lower than in period C (15.28 MJ/kg). It is concluded, therefore, that because of its effect on AME_n of the HPLE reference diet in chicks older than 17 d, bird age is of considerable importance in the determination of AME_n in grains when substituted for the entire diet.     

Evaluation of fatty acid metabolism and innate immunity interactions between commercial broiler,F1 layer × broiler cross and commercial layer strains selected for different growth potentials

Background: The broiler industry has undergone intense genetic selection over the past 50 yr. resulting in improvements for growth and feed efficiency, however, significant variation remains for performance and growth traits. Production improvements have been coupled with unfavourable metabolic consequences, including immunological trade-offs for growth, and excess fat deposition. To determine whether interactions between fatty acid(FA) metabolism and innate immunity may be associated with performance variations commonly seen within commercial broiler flocks, total carcass lipid %, carcass and blood FA composition, as wel as genes involved with FA metabolism, immunity and cel ular stress were investigated in male birds of a broiler strain, layer strain and F1 layer × broiler cross at d 14 post hatch. Heterophil:lymphocyte ratios, relative organ weights and bodyweight data were also compared.Results: Broiler bodyweight(n = 12) was four times that of layers(n = 12) by d 14 and had significantly higher carcass fat percentage compared to the cross(n = 6; P = 0.002) and layers(P = 0.017) which were not significantly different from each other(P = 0.523). The carcass and whole blood FA analysis revealed differences in the FA composition between the three groups indicating altered FA metabolism, despite al being raised on the same diet. Genes associated with FA synthesis andβ-oxidation were upregulated in the broilers compared to the layers indicating a net overal increase in FA metabolism,which may be driven by the larger relative liver size as a percentage of bodyweight in the broilers. Genes involved in innate immunity such as TLR2 and TLR4, as wel as organel e stress indicators ERN1 and XBP1 were found to be nonsignificant, with the exception of high expression levels of XBP1 in layers compared to the cross and broilers. Additional y there was no difference in heterophil: lymphocytes between any of the birds.Conclusions: The results provide evidence that genetic selection may be associated with altered metabolic processes between broilers, layers and their F1 cross. Whilst there is no evidence of interactions between FA metabolism, innate immunity or cel ular stress, further investigations at later time points as growth and fat deposition increase would provide useful information as to the effects of divergent selection on key metabolic and immunological processes.     

Behavioural development in groups of pen‐housed pullets in relation to genetic strain,age and food form

1. Behavioural development in groups of 8 pullets kept in pens with litter floors, and fed on either mash or pellets, was studied from 0 to 10 weeks in a White Leghorn X broiler (F2) hybrid line (experiment 1) and from 0 to 24 weeks in Hisex, White Leghorn and Brown Leghorn strains (experiment 2). The aim was to identify precursors of feather pecking and cannibalism.

2. Rates of body weight gain were consistently greater with pellets than with mash in both experiments. In experiment 2, the onset of lay was at 17 weeks of age in Hisex, 21 weeks in White Leghorns and 23 weeks in Brown Leghorns.

3. Persistent feather pecking, which was not seen in experiment 1, developed in 2 of 12 groups (one Hisex and one White Leghorn, both fed on pellets) in experiment 2, and was studied in detail at 23 and 24 weeks. The more damaging pecking in the Hisex group was followed by cannibalism in the same group.

4. Based on the (often inconsistent) effects of genetic strain, age and food form on behaviour diat were observed, a working hypothesis was constructed to account for the aetiology of feather pecking and cannibalism in situations where there is floor litter.

5. An age‐related decline in one or more foraging activities may coincide with increases in preening and non‐damaging pecking at other birds. Consumption of litter particles and moulted feathers may be reinforcing. Dustbathing may enhance the stimulus value of litter particles when they are contrasted against background plumage colour. This may direct pecking towards the backs of birds, where feathers as well as litter particles may be removed and eaten. Regular pecking and feather removal may lead eventually, after the onset of lay, to vent pecking and cannibalism. This sequence of events may be more likely in groups where activity levels are high.     

Plasma growth hormone and insulin‐like growth factor‐I (IGF‐I) concentrations at the onset of lay in ad libitum and restricted broiler breeder fowl

1. Plasma concentrations of growth hormone (GH) and insulin‐like growth factor I (IGF‐I) were determined in individually caged broiler breeder females from 17 to 30 weeks of age. The birds were fed ad libitum or restricted during rearing in a randomised block design. Restricted birds were fed ad libitum after laying an egg and egg production was recorded to 54 weeks.

2. GH concentrations were higher in restricted compared with ad libitum‐fed birds at 17 to 21 weeks of age and were similar thereafter. Plasma IGF‐I concentrations were higher in restricted compared with ad libitum‐fed birds throughout the sampling period of the experiment.

3. The age at first egg was delayed by about two weeks in restricted birds. At 54 weeks of age they had laid 114 compared with 67 eggs in birds fed ad libitum throughout and had produced less than half the number of eggs with defective shells.

4. It was suggested that differences in egg production between ad libitum and restricted broiler breeder females could be related to changes in the pattern of GH and/or IGF‐I secretion.     

Replacement value of blue‐green alga (spirulina platensis) for fishmeal and a vitamin‐mineral premix for broiler chicks

1. The effect of sun‐dried Spirulina platensis in poultry diets was studied in a 12‐week feeding trial by replacing either fishmeal (FM) or groundnut cake (GC) in a commercial diet with algae at isonitrogenous concentrations of 140 g/kg and 170 g/kg respectively. Additional vitamins/ minerals were omitted from the algal diets because Spirulina is rich in them.

2. Efficiency of food utilisation, protein efficiency ratio and dressing percentage indicated that substitution of FM or GC by alga did not affect the performance of broilers.

3. None of the diets affected the weights, compositions and histopathology of the various organs of the chicks.

4. Meat quality remained unchanged except for a more intense colour in the case of birds fed on the alga‐containing diets.     

Effects of dietary sulphur‐containing amino acids on performance and breast meat deposition of broiler chicks during the growing and finishing phases

1. Two growth trials were performed to measure the effects of dietary methionine and cystine (SAA) on growth rate, food conversion efficiency and breast meat deposition in male broilers.

2. In experiment 1, broilers were grown on 6 experimental diets covering a range from 6.9 to 9.6 g SAA/kg. The diets were fed from 15 to 33 d of age. Similarly, in experiment 2, 6 diets containing 6.0 to 8.5 g SAA/kg were fed to finishing broilers 33 to 43 d of age. In each experiment 60 birds per treatment were processed, and carcase yield and breast meat percentage were determined.

3. Significant responses in weight gain, efficiency of food conversion and breast meat percentage were detected, which could be described well by exponential regression curves. Dietary SAA requirements to obtain maximum efficiency of food utilisation and maximum breast meat deposition were estimated to be about 9.0 g/kg from 15 to 33 d of age, and about 8.0 g/kg from 33 to 43 d of age.

4. Economic aspects were considered to calculate optimum SAA specifications from the results. In both trials, the dietary optimum of SAA was found to be higher for birds to be further processed than for birds to be marketed as whole carcases.     

The incidence of breast‐blister down‐grading in broiler chickens

1. A survey was conducted into down‐grading due to breast blisters at a large processing plant.

2. The relationships between incidence of down‐grading and age, body weight, sex, size of rearing site and its distance from the processing plant, and various weather conditions during the rearing period of each flock were examined using regression analysis.

3. Age and body weight and rearing site size were the only factors significantly correlated with amount of blistering.     

Anti‐nutritive activity of wheat pentosans in broiler diets

1. To assess their possible anti‐nutritive activity wheat pentosans were isolated from a milling by‐product and added at graded levels to a sorghum‐based broiler chicken diet.

2. A water‐insoluble pentosan preparation (WIP, 720 g arabinoxy‐lan/kg) caused a depression of apparent metabolisable energy (AME) of 1.63 MJ/kg DM at the highest level of inclusion (41.9 g/kg). Broilers maintained on this diet showed significant growth depression and a decrease in feed conversion efficiency.

3. A water‐soluble pentosan preparation (WSP, 520 g arabinoxy‐lan/kg) showed less anti‐nutritive activity.

4. In a second experiment the AME of rice (pearled), maize, sorghum, wheat, triticale, barley and rye was determined. The AME values obtained were highly correlated (r= — 0.98, P<0.001) with the summed levels of pentosans and β‐glucans found in the cereals.

5. It was concluded that the pentosans of wheat possess anti‐nutritive activity when present in broiler diets and that similar polysaccharides may influence the nutritive value of other cereals.     

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.     

Behavioural and anatomical consequences of two beak trimming methods in 1‐ and 10‐d‐old domestic chicks

1. To examine the effects of beak trimming on behaviour, beak anatomy, weight gain, food intake and feather condition 360 ISA Brown chicks were trimmed by hot cut or cold cut at 1 d or 10 d of age or were sham‐operated controls. The experiment was a 3 × 2 factorial design, with the chicks housed in littered pens in groups of 10 and observed for 6 weeks after trimming.

2. In the first week after trimming, when trimmed birds were compared with untrimmed controls, they were less active (sat and slept more), fed less, preened less and generally engaged in less beak‐related behaviour.

3. These differences waned sharply during week 2 and had disappeared by week 5. There were very few differences between hot‐ and cold‐cut birds.

4. There were also differences in production variables: trimmed birds grew more slowly during the week after trimming, their food intake was depressed for 3 weeks and food conversion efficiency improved for 2 weeks.

5. The only significant effect on feather scores was better plumage condition in the groups trimmed at 1 d and scored at 6 weeks.

6. To examine the anatomical effects 36 ISA Brown chicks trimmed by hot or cold cut at 1 d or 10 d of age were killed at 21 and 42 d after trimming, and their beaks were processed and examined histologically. In all trimmed groups healing was very rapid and no scar tissue was seen but, unlike the controls, the regrown tips contained no afferent nerves or sensory corpuscles.

7. Beak lengths immediately after trimming were 40% to 50% shorter than controls; the anatomical consequences of both methods were identical.

8. Overall, it was judged that the effects on behaviour and beak anatomy were much less severe than previously reported for birds trimmed at older ages. If birds do have to be trimmed then the procedure should be carried out in young birds: from the birds' standpoint 1 d appears to be the most suitable.     

Effectiveness of dietary 25‐ and 1‐hydroxycholecalciferol in combating tibial dyschondroplasia in broiler chickens

1. Three experiments were carried out to determine the effects of feeding diets containing different concentrations of cholecalciferol, 1 a‐hydroxychole‐calciferol (1‐HCC), 25‐hydroxycholecalciferol (25‐HCC), 1,25‐dihydroxycholecalcif‐erol (1,25‐DHCC) and ascorbic acid on the incidences and severities of tibial dyschondroplasia (TD) at 3 weeks of age in male broiler chicks.

2. In experiment 1, replacing 75 μg cholecalciferol/kg with the same weight of 25‐HCC decreased significantly (P<0.01) the incidence of TD from 65 to 10%.

3. In experiment 2, the incidence of TD in the control group was lower, but feeding amounts of 25‐HCC up to 250 μg/kg had a linear effect on the incidence of TD that was significant at P=0.06. There was no effect or interactions with dietary addition of 250 mg ascorbic acid/kg. Dietary addition of 5 μg 1‐HCC/kg decreased TD incidence from 21 to 5%, though the effect was not significant (P>0.1).

4. TD incidence in experiment 3 was too low to determine an effect of 25‐HCC or 1,25‐DHCC on TD incidence, though in this, as in both other experiments, the severities of TD lesions were always lower with diets containing cholecalciferol metabolites.

5. Hypercalcaemia was not observed after feeding up to 250 μg 25‐HCC/kg in either experiments 2 or 3.

6. It is concluded that 25‐HCC may be an effective practical means of improving broiler leg health by alleviating the incidence and severity of TD.