Carcass conformation comparisons of growing broiler and laying strain chickens

The conformations of growing broiler and laying strain chickens were compared in an attempt to discover whether, in the course of selecting broilers of high growth potential, the conformations of such birds had been so altered as to predispose them to skeletal failure. It was found that broilers had essentially similar proportions by weight of their various body complexes to laying strain birds of equal body weights. Broilers had slightly greater trunk proportions and lower leg proportions than laying strain birds of equal weights but the differences were insufficiently great to explain satisfactorily the supposed predisposition of the broiler leg skeleton to failure. Broilers, at any given body weight, had bones shorter in length than laying strain birds, explaining the more compact appearance of the broiler when compared with the more slender laying strain bird. A compact skeletal system is one which would appear less rather than more likely to fail.     

Tendon lesions in broiler fowls

Tendon lesions have been studied in 35 broiler or broiler breeder fowls. Tendon rupture most commonly affected the gastrocnemius and flexor muscles but was also seen in cranial tibial muscles (four cases) and the patellar tendon (one case). In nine birds tenosynovitis, characterised by a marked inflammatory response, was identified. In others, however, rupture occurred without appreciable inflammation and these cases were concluded to be comparable to spontaneous tendon rupture in other species. A traumatic aetiology is suggested in these cases, as other pelvic limb tendons or ligament rupture was a frequent concomitant finding. Degenerative tendon lesions were present but it is uncertain whether such changes are primary or secondary to rupture.     

Pattern of vascular canals in the bone extremities of the pelvic appendicular skeleton in broiler type fowl

Broiler fowls were reared from hatching till 20 weeks old. Birds were killed throughout the growth period and the bone extremities of the pelvic appendicular skeleton prepared for study. The patterns of vascular canals in these broiler fowls were very similar to earlier reports in laying strain fowls. There was a great range of and variation in the vascular morphology of broiler fowl. The physeal vasculature of the rapidly growing broilers was frequently disrupted, and such areas were often associated with dyschondroplastic lesions. The rapidly growing bone extremities in broiler fowls were susceptible to occlusion of epiphyseal vascular canals. lesions were frequently seen at similar sites in different specimens. Links are suggested between the growth rate, weight and behavioural characteristics of broiler fowls and the development of lesions.     

Chronic orthopaedic disease in adult male broiler breeding fowls

An assessment has been made of spontaneous orthopaedic disease in 100 male broiler breeding fowls aged between 51 and 62 weeks. Lesions were identified in the pelvic limbs of 92 birds, 85 of which showed total or partial rupture of ligaments or tendons. Total ligament or tendon failure was identified at one or more skeletal sites in 54 birds. In two cases, avulsion of the femoral origin of the cranial tibial muscle had occurred. Other findings included degenerative changes in a number of joints but there was no correlation with ligament derangement. Partial or total detachment of the femoral head occurred in 16 birds. The primary lesion was disturbed endochondral ossification and, once detached, the femoral head normally became necrotic. In the reparative phase, 'creeping substitution' was identified.     

Patterns of physiological bone torsion in the pelvic appendicular skeletons of domestic fowl

Femoral, tibiotarsal and tarsometatarsal torsion was measured in 264 domestic fowls. Birds were either a laying strain fed ad libitum, or a broiler strain fed ad libitum or a broiler strain on restricted feed. They were killed at different times up to 24 weeks of age. Femora were normally rotated externally when the transverse axis of the distal articular surface was compared with that of the proximal joint surface. Tibiotarsi were similarly rotated externally but the high incidence of internal torsion in broilers fed ad libitum suggests that internal rotation is pathological. Tarsometatarsi were normally rotated internally. Mild degrees of intertarsal valgus angulation are physiological but asymmetrical angulation and torsion between each limb of individual birds suggests that a pattern of limb dominance occurs in domestic poultry.     

Non-infective factors in the aetiology of synovitis in chickens

A study was conducted to elucidate the relative susceptibility of broiler breed birds to synovitis and the relative resistance of laying breed birds to this disease. It was shown that difference in structure and chemical composition of fibrous connective tissue can be associated with this difference in susceptibility. A loose structure of fibrous connective tissue (common in broiler breed birds) appears to predispose to synovitis, whereas a compact structure (common in laying breed birds) can be associated with resistance to synovitis. The most fundamental approach to the synovitis problem would be the breeding of broiler breed birds with a compact structure of fibrous connective tissue. However, this approach does not seem to offer favourable prospects in the near future. For the present, synovitis resistance in broiler parents can be enhanced by practising a management scheme aiming at activation of the birds.     

Rupture of gastrocnemius tendon in broiler breeder hens

Lameness and mortality of 0.55% to 1.00% per week occurred in 32-to-33-wk-old broiler breeder hens in a complex involving eight houses. Males were not affected. Laboratory evaluation of 19 birds, over 2 wk, revealed complete rupture or partial tear, primarily of the gastrocnemius tendon; the fibularis longus, fibularis brevis, and flexor muscles and their tendons were injured in a few birds. Rupture of the gastrocnemius tendon has been observed in broiler breeder chickens older than 12 wk of age and it is characterized by lameness secondary to unilateral or bilateral rupture of the tendon. The cause of this condition has been primarily attributed to reovirus infection but rupture by other causes can also occur. In this case, there was no evidence of synovitis or reovirus infection in the birds. The cause of the ruptures was attributed to aggressive males when the ratio of males to females was increased from seven or eight males per 100 females at 22-23 wk to nine or 10 per 100 at 31 wk of age.     

Red cell size and various lung arterial measurements in different strains of domestic fowl

Red cell size and various lung arterial measurements were examined in different strains of young commercial broiler and layer fowls. The broilers were: Marshall, Cobb, Ross 'selected', Ross 'relaxed' and the layers were: Isa Brown, Ross Brown and Hisex Brown. The Ross relaxed bird had a significantly larger red cell than any other strain. Overall, broilers had larger red cells than layers. The internal elastic lamina, a measure of arterial size, was small in the Ross relaxed bird (138 microns) and was at its maximum (163 microns) in the selected Ross strain. The medial area (muscle coat) was least in the Ross relaxed bird (984 microns2) and greatest in the Cobb strain (1516 microns2). In some strains there was a slight correlation among birds between red cell and arterial size but not with the medial area. The results appeared to indicate that red cell size may not be the only important correlating factor in the aetiology of pulmonary hypertension in fowls.     

Drop of egg production in chickens by experimental infection with an avian metapneumovirus strain PLE8T1 derived from swollen head syndrome and the application to evaluate vaccine

Decreases in egg production and increased incidence of abnormal eggs due to malformation of egg shells were observed in specific pathogen free (SPF) 173-day-old laying hens inoculated intravenously with an avian metapneumovirus (aMPV) strain PLE8T1. This strain was derived from an isolate from broiler birds exhibiting swollen head syndrome (SHS). Some SPF birds inoculated with the virus showed, slight diarrhea without any respiratory symptoms. Thus, the PLE8T1 strain was used as a challenge virus to evaluate efficacy of aMPV vaccines. SPF chickens which received a live attenuated aMPV vaccine (NEMOVAC; Merial) at 7 or 77 days old and an inactivated aMPV vaccine (OVO-4; Merial) at 105 days old were protected against poor egg production caused by the challenge with the PLE8T1 strain. Thus, aMPV, the PLE8T1 strain passaged 22 times after isolation, from birds exhibiting SHS, could induce a drop in egg production in laying hens accompanied by malformation of egg shells. It was suggested that this challenge system could be applied to evaluate the efficacy of aMPV vaccine.     

Comparisons of the skeletal systems of growing broiler and laying strain chickens

Skeletal systems of growing broiler and laying strain chickens were compared in an attempt to establish whether the rapid growth rates of broilers lead to qualitative or quantitative skeletal deficiencies. Qualitative comparisons included studies of bone histology and of bone ash, density and compression strength. Quantitative comparisons related bone weight to body weight. Bone “ matured “ very rapidly, as judged by its density, ash content and weight relative to bird weight in the first fortnight of life and thereafter more slowly in both broilers and laying strain birds. After the age of I week bones “ matured “ mainly by replacement of water by mineralised osteoid—the degree of mineralisation of osteoid being a less important factor in bone “ maturation “. There were no significant differences from the viewpoint of either quality or quantity between the skeletal systems of broilers and laying strain birds of the same age. At equal body weights, however, broilers had skeletal systems which were both qualitatively and quantitatively less “ mature “ than those of laying strain birds. These differences were most marked during early life when the rate of skeletal “ maturation “ was high.     

Effect of unilateral weight-bearing on pelvic limb development in broiler fowls: vascular studies

Fifteen broiler fowls which habitually adopted a unilateral weight bearing stance were studied. In the majority of fowls the left pelvic limb was weight bearing and the right limb showed severe angular deformity. Dyschondroplasia occurred most frequently in the load-bearing limb. In the load-bearing limb the majority of lesions were in the femur and proximal tibiotarsus. In the non-load-bearing limb lesions most frequently occurred in the bone extremities of the distal tibiotarsus and proximal tarsometatarsus. Occluded epiphyseal vascular canals occurred in conjunction with physeal thickening at some dyschondroplastic sites. The majority of dyschondroplastic lesions contained elongated penetrating epiphyseal vessels and vessels derived from the perichondrial ring. These vessels were associated with chondrocyte hypertrophy and matrix calcification, which was considered to lead to the repair of the lesions. There was minimal calcification of cartilage at the base of the dyschondroplastic lesions and the underlying metaphyseal vessels were blunt ending. This suggested that a band of abnormal physeal cartilage was acting as a barrier to penetration by the metaphyseal vessels and so preventing subsequent endochondral ossification.     

Effects of age and diet on the lipid content and composition of gallbladder bile, liver and serum in laying strains of hen

1. Changes in lipid content and composition of liver and bile during pre- and post-laying periods were investigated in hens of a laying strain. 2. The large increase in liver lipid concentration, particularly triacylglycerols, at the onset of laying was accompanied by the appearance of triacylglycerols in the bile. 3. Accumulation of triacylglycerol in the liver was increased by a diet containing maize and soyabean meal. This was associated with increases in the triacylglycerol concentration in both serum and bile. 4. Liver microsomal phosphatidate phosphohydrolase activity was positively correlated with liver triacylglycerol content in birds given the maize/soyabean meal diet. 5. The time course of triacylglycerol accumulation in the liver and associated changes in the bile triacylglycerol concentration in laying strain hens were different to those previously observed in broiler hens. 6. Over the lifetime of the bird, secretion of triacylglycerols into bile may play an important role in the prevention of fatty liver syndromes.     

Effect of unilateral weight-bearing on pelvic limb development in broiler fowls: morphological and radiological findings

Twenty-five broiler chickens, which habitually adopted a unilateral weight-bearing stance, were studied. In all cases the contralateral limb was held free of the ground, normally as a result of gross valgus angulation of the intertarsal joint. The left pelvic limb was more frequently weight-bearing than the right which suggests that a pattern of limb dominance may occur in broiler fowls. Metaphyseal lesions, suggestive of dyschondroplasia, were more common in the load-bearing limb. This suggests that altered load-bearing or posture can initiate or exacerbate dyschondroplasia in susceptible birds. The load-bearing limb also showed altered patterns of bone torsion. These findings are similar to those observed in induced physeal (growth plate) osteochondrosis in mammals and the pathogenesis of lesions is likely to be similar.     

Sequential spread of Campylobacter infection in a multipen broiler house

Generally, colonization with Campylobacter jejuni is first detected in broilers 2-3 wk after hatching. Once introduced into a flock, this infection spreads very rapidly. The sources and routes of transmission of C. jejuni in broilers remain debatable. In this study, the spread of infection was monitored in a commercial multipen broiler house in which birds were contained in discrete groups and sampled sequentially. Colonization was monitored in two broiler flocks up to slaughter. Serotyping and fla typing methods were applied to differentiate all the C. jejuni strains isolated. In flock 1, colonization was first detected at 32 days of age in birds located at the rear of the house. By 40 days, nearly all the birds were infected with the same strain (fla type 1.9). However, at 46 days of age, a second strain (fla type 3.7) was detected in some of the birds. These birds were also located toward the rear of the house. In flock 2, infection was detected at 5 wk of age. This infection was once again first detected in birds located at the rear of the house. In this flock, only a single fla type (1.1) was isolated throughout. A survey of the broiler house relative to the location of first point of infection indicated the use of an entrance door unprotected by boot dips. However, securing this door during the second flock study did not prevent infection.     

Some effects of feeding lathyrogens to laying fowls

The lathyrogen semicarbazide inhibited egg‐laying in fowls. The primary target of the drug appeared to be the pituitary gland. Ovulation and normal egg production were resumed soon after withdrawal. The eggs laid during administration appeared to be normal except that their shell membranes were heavier and less pigmented. Amino acid composition of the membranes from treated birds was normal, but they yielded more soluble hydroxyproline‐containing material when autoclaved for 5 h. Prolonged (20 h) autoclaving of membranes from both treated and control birds produced a soluble material very rich in hydroxyproline. Deprivation of dietary calcium did not influence the observed effects of semicarbazide. Plasma‐free hydroxyproline assays indicated that in laying birds semicarbazide produced labilisation of body collagen, but in pre‐laying birds it caused lack of appetite to the point of inanition.     

Comparison of haematological values in restricted- and ad libitum-fed domestic fowls: white blood cells and thrombocytes

1. White blood cells and thrombocyte values were examined in normal domestic fowls of layer and broiler strains fed restricted or ad libitum diets. 2. Basophils were the only white blood cells to increase significantly in number after the period of food restriction. It is suggested that the increase may have been associated with stress. 3. There were more basophils in broilers than layers, in males than females and in younger than older birds. 4. In contrast, a decrease in the total number of white blood cells was seen in birds maintained on a restricted diet compared with those fed ad libitum. 5. Stress may also have been responsible for an increased thrombocyte count in the restricted birds as well as a slightly lowered eosinophil count. 6. Heterophil/lymphocyte ratios were not significantly altered by the restriction of food.     

Relationships of Body Weight,Feathering, and Footpad Condition with Reproductive and Carcass Morphology of End-of-Season Commercial Broiler Breeder Hens

Reproductive efficiency of broiler breeder hens declines with age. Whereas careful feed management can maximize BW uniformity at housing, there is variability in how rate of lay and flock behavioral dynamics will interact with subsequent growth during the breeder phase. This study characterized differences in carcass and reproductive morphology in end-of-cycle commercial broiler breeder hens based on BW, feather coverage, and footpad condition, and we discuss the potential implications of the findings. At 62 wk of age, 537 hens were studied from an original flock of 3,800. Birds were sorted into subgroups based on BW, feather score, footpad score, and whether they were in laying condition when dissected. The average flock BW was 3.56 kg, with means of 2.86, 3.56, and 4.20 kg for the low (LOW), standard (STD), and high (HIGH) BW groups, respectively. A higher proportion of birds from the STD (85%) and HIGH (81%) groups still had a fully formed reproductive tract compared with birds of the LOW (59%) group. The LOW birds in laying condition had a smaller ovary than the STD or HIGH birds. The ovary condition of birds in laying condition was not related to feather coverage. As feather coverage improved, final hen BW increased, demonstrating a potential role of feather coverage in growth efficiency or of BW in level of mating activity. Birds that received a feather score of 5 (complete back feather coverage) and had a normal reproductive tract made up 14.7% of this flock. It is likely that many of these birds were mating very infrequently or possibly not mating, which has implications for maintenance of flock fertility. Some may also have been returning from a molt. Footpad condition was not related to body size. External traits such as BW, feather score, and footpad score can provide insight into flock reproductive condition and male:female interaction.     

Comparative histomorphological and ultrastructural study of the luminal epithelium of the isthmus in laying and moulting domestic fowls (Gallus domesticus)

This study describes ciliated, nonciliated and mitochondrial luminal epithelial cells of the isthmus in laying and moulting domestic fowls using histological and ultrastructural techniques. The ciliated cells were nonsecretory, while numerous electron‐dense secretory granules were present in the nonciliated cells of laying birds. Mitochondrial cells, occurring in two morphologically distinct forms, constituted the third type of epithelial cell present in the isthmus. The SEM study showed that the luminal epithelium was dominated by ciliated cells, the cilia of which partially obscured adjacent nonciliated cells. The involution of the luminal epithelium in moulting birds occurred via autophagy, apoptosis and necrosis. Autophagic inclusions, which included autophagosomes and autolysosomes, were present in the early degenerative phases of ciliated, nonciliated and mitochondrial cells. Nonciliated cells underwent degeneration via apoptosis, which was characterized by nuclear and cytoplasmic condensation. Apoptotic and necrotic ciliated cells were evident during the intermediate and advanced stages of regression. The presence of apoptotic cell death was confirmed using the TUNEL assay. Loss of cilia via the formation of cilia packets was observed using TEM and SEM. Necrotic cell death occurred in mitochondrial cells during the intermediate and late stages of degeneration. In conclusion, the findings of the study on isthmus involution in moulting birds suggest that autophagy is a process confined to the early stages of degeneration, while apoptosis and/or necrosis occur in the terminal stages of regression.     

Morphometric and radiographic characteristics of tibial bone of broiler chickens with twisted leg disorders

Tibiae from normal broiler chickens were compared with those from broilers displaying twisted leg in an attempt to develop a pattern recognition for the disorder. Qualitative differences were determined using conventional radiography, and quantitative differences were determined using sequential morphometry. Sequential radiography revealed that twisted leg developed from a slight deviation or torsion of the distal tibiae. Progressive bowing of the tibiae and compensatory thickening of the cortex on the weight-bearing side were characteristic radiographic features of twisted leg and were most likely a functional adaptation to the disorder. Sequential morphometry suggests that the development of twisted leg in broilers may be related to a structural abnormality in the distal tibiae, namely shallow distal condyle grooves. Shallow distal condyle grooves may predispose the distal tibiae to a slight displacement of the gastrocnemius tendon and hence uneven strain on the distal condyles. Other changes in tibial morphology (diameter at midshaft, condylar width, cortical thickness) appeared to be functional adaptations to the deformation rather than the primary cause.