Feed intake pattern of broiler chickens under intermittent lighting: Do birds eat in the dark?

This paper reflects the results of a short experiment conducted in parallel with a larger trial which aimed to test the assumption that ‘consumption of feed by broiler chickens during periods of darkness is largely negligible’. To that effect, on d 31, feeders of birds raised under intermittent lighting (IL), i.e. 1 h of light [1L]:3 h of dark (3D):1L:3D:1L:3D:1L:3D:2L:6D, were weighed at the onset and at the end of each period of darkness (or scotoperiod). Moreover, in order to compare the feeding behavior of IL birds with that of broilers raised under continuous lighting (CL, i.e. 18L:6D), their feeders were weighed in parallel and at the same time points. On d 31, feed intake of IL birds during scotoperiods represented 45% of their 24 h feed intake. Both CL and IL birds presented anticipatory feed intake prior to the long nocturnal period of darkness (6D), as well as higher feed intake right at the onset of lighting at 06:00. Feed intake of CL birds during the 6D nocturnal scotoperiod was negligible at around 2% of their total feed intake. Intermittent lighting birds exhibited excitement at the start of each hour-length scotoperiod and, within that time, ingested around 2.5 times the amount of feed ingested by CL birds. Although short, this study revealed several interesting observations which might be worth further exploring in a larger, lengthier, behavior-focused experiment. Amongst other factors, it might be interesting to understand whether the high feed intake observed during scotoperiods for IL birds in reflective of the whole flock or rather a coping mechanism developed mainly by hierarchically lower-ranking birds to achieve their daily feed intakes requirements.     

Effect of light source and regimen on growing broilers

The aim of this study was to determine the effect of different light sources and light schedules on the growth and quality of commercial broilers. In each experiment 810 broiler chicks were divided into 3 groups, 3 replicates per group. All were reared at 20 lux. Body weight and food consumption were recorded weekly. Experiment 1. Birds were reared under 3 light sources: incandescent light bulb, warm-white fluorescent light tube or warm-white mini-fluorescent light bulb. Experiment 2. Birds were reared on 3 light schedules. 23 h light and 1 h dark (23L: 1D) throughout; an increasing light schedule with initial 23L:1D then 8L: 16D increasing daylight gradually to 16L:8D or an intermittently increasing daylight schedule (16:8P) where light and dark periods were shorter but portioned to achieve the same total hours per day up to 16L:8D. Broilers reared under mini-fluorescent light bulb were heavier than those under fluorescent tubes or incandescent bulbs by 49 d. Until 42 d of age, photoperiod had no effect on growth. However, at 49 d broilers reared under 16:8P and 16L:8D regimens were heavier than those or 23L:1D. At 42 d, female broilers on 23L:1D, were heavier than those on 16L:8D and 16:8P. Mortality was higher in groups on 23L:1D than on 16L:8D on 16:8P. At 49 d incidence of leg condemnation was higher in the 16:8P group. However, skin damage was lower in this group than in those on 23L: 1D and 16L:8D.     

Intermittent lighting and feeding schedules for broilers incorporating long periods of darkness

1. Intermittent lighting and feeding schedules incorporating long periods of darkness and periods without access to food were applied to growing broilers.

2. Birds exposed to a 2 h light(L): 10 h dark(D) lighting schedule with feeding restricted to the light periods ate significantly less food and grew more slowly than conventionally‐reared birds. Satisfactory growth and efficiency of food utilisation were obtained by allowing these birds access to food during the dark periods.

3. Altering the lighting schedule to 2L:6D resulted in birds with food intakes and growth rates similar to those reared conventionally, even when feeding was restricted to the light periods.

4. Releasing birds from the light and food restriction for the 2 weeks preceding slaughter resulted in greater food consumption which was not characterised by significantly better growth or food utilisation.

5. Feeding a diet of high energy or pelleting a diet of low energy during the period of restriction increased food intake and improved growth rate.

6. The response of broilers to intermittent lighting and feeding was not significantly influenced by ambient temperature within the range 16 to 35 °C or by the energy concentration of the diet fed before the introduction of the intermittent schedule.     

Influence of nutrient density and lighting regime in broiler chickens: Effect on antioxidant status and immune functiona

1.?The effects of nutrient density and lighting regime on oxidant status and immune function of broilers were investigated in a 2 × 4 experimental design (8 groups of 576 chickens).

2.?There were two nutrient densities: high (H) starter diet AME 13·39 MJ/kg, 230 g crude protein (CP)/kg: finisher 13·39 MJ/kg, 197 g CP/kg CP) and low (L) starter AME 12·03 MJ/kg, 208 g CP/k; finisher 12·14 MJ/kg, 183 g CP/kg C. The 4 lighting regimes were continuous (CL) 23L:1D, 20L:4D (12L:2D:8L:2D), 16L:8D (12L:3D:2L:3D:2L:2D) and 12L:12D (9L:3D:1L:3D:1L:3D:1L:3D). Blood and lymphoid organs were collected at d 21 and 42 for assay of antioxidant indices and immunity.

3.?Chickens fed low density diet had a higher Fabricius bursa weight (FBW). Low density diet tended (P = 0·089) to increase the a-Naphthylacetate esterase (ANAE) positive percentage response at 42 d.

4.?The 12L:12D schedule decreased serum malondialdehyde compared with other regimes at 21 d. At 42 d, it was lower in the 12L:12D and 16L:8D groups than in CL and 20L:4D. There was a trend (P = 0·086) for greater superoxide dismutase activity in the 12L:12D and 16L:8D groups than under the CL and 20L:4D regimes at 42 d. ANAE positive percentage in 12L:12D group at 42 d was higher than in CL and 20L:4D groups. Plasma IgG in the 12L:12D group at 42 d was higher than in the CL group.

5.?There was an interaction between nutrient density and lighting regime for FBW at 42 d.

6.?These results demonstrate that low nutrient density and a 12L:12D schedule lighting schedule can enhance oxidant-antioxidant balance and the immune functions of broilers.     

Serum concentrations of melatonin in prepubertal gilts exposed to either constant or stepwise biweekly alteration in scotophase

Melatonin (MEL), a hormone known to mediate photoperiodic cues, is secreted from the pineal gland in a circadian fashion in numerous species. The transduction of photoperiodic information into the secretion of MEL, however, remains controversial in the pig. To determine whether domestic pigs have a nocturnal increase in serum melatonin when exposed to equatorial photoperiods only, 24 prepubertal gilts (38.7 ± 0.7 kg; 104.5 ± 0.8 d) and 12 mature ewes, serving as positive controls, were assigned randomly to one of two environmentally regulated rooms. The light (L):dark (D) schedule in one room remained constant (10 L:14 D), while the other room scotophase (darkness duration) was decreased by 1 hr every 2 wk (Experiment 1). After a 2-wk acclimation to each new schedule, 6 ewes and 6 gilts in each room were bled by venipuncture at 2-hr intervals for 22 hr. Experiment 2 was conducted as described for Experiment 1, except that the LD schedule in one room remained constant (15L : 9D) while length of scotophase in the other room was increased by 1 hr every 2 wk. In gilts that were exposed to constant 10L:14D, scotophase MEL in serum averaged 103 ± 13 pg/ml as compared with 57 ± 13 pg/ml in the photophase. Using each gilt's initial photophase value as a statistical covariate, scotophase MEL in the constant 10L:14D schedule was higher (P < 0.001) than photophase MEL. A similar analysis of MEL in gilts exposed to stepwise biweekly decreases in scotophase revealed a scotophase elevation (P < 0.05) in only certain LD schedules (i.e., 12L: 12D and 13L:11D) but the same trend was present throughout all LD schedules. Subjective examination of individual gilt profiles revealed that 56% of gilts had a nocturnal increase in serum MEL in Experiment 1. However, only 10% of the MEL profiles were closely coupled to the environmental LD periods. Overall, mean serum MEL was slightly elevated during scotophase in gilts, but the nocturnal elevation of MEL in gilts was of lesser magnitude and more variable than in ewes. Data from these two experiments suggest that the domestic pig has an inherently weak nocturnal elevation in serum MEL, and the ability to detect these rises is dampened by considerable pig-to-pig variability.     

Sex differences in the effect of intermittent compared with continuous light on growth rate, testes and body weight of broilers reared under commercial conditions

The effect of intermittent light (IL) on the growth of broilers was tested under commercial conditions. One-d-old chickens were subjected to continuous light (CL) until 7 d of age and then received either CL or 7.5L:4.5D:7.5L:4.5D until 53 d. Body and testes weights were measured. At 53 d of age, the mean body weight of males was greater on IL than on CL; for females there was no difference. The testes of males on IL weighed more than those on CL. Growth of broilers was greater (P less than 0.05) at 35, 49 and 53 days of age if light was provided continuously from hatch to 7 d of age and then switched to IL than those remaining on CL during the entire periods.     

Effect of lighting treatment on the productivity,health, behaviour and sexual maturity of heavy male Turkeys

1. Turkey poults (1620) were used to compare the effects of three lighting programmes on heavy strain males reared to 188 d: constant light (24L:0D, CON); increasing light (6L:18D at 7 d gradually increasing to 20L:4D by 63 d, INC); a pattern identical to INC followed by a decrease in daylength from 84 d to 10L:14D at 112 d (DID).

2. Lighting affected growth pattern but had no effect on body weight at 118 d or overall food to gain ratio.

3. Both INC and DID lighting reduced overall mortality in comparison to CON light primarily because of a reduction in the incidence of skeletal disease and spontaneous cardiomyopathy. INC and DID lighting increased the incidence of cannibalism.

4. Turkeys given INC or DID lighting had a superior ability to walk in comparison to those birds given CON light.

5. INC and DID males stood, ate and drank more frequently, and sat less often than CON turkeys during behavioural observation.

6. There were no lighting effects on carcase composition except that INC and DID birds had heavier keel bones. The ultimate force per cm² (stress) required to break femora was greater for turkeys given INC and DID lighting (P = 0.065).

7. Plasma testosterone concentrations at 117 d were 272.5, 115.2 and 29.5 pg/ml for turkeys given CON, INC and DID lighting, respectively (P= 0.072). Testosterone concentration was not related to growth rate.     

Effect of lighting period on the performance of male turkeys from 6 to 18 weeks of age

A total of 468 male turkeys which had been fed ad libitum and received light for 23 h each day for the first 6 weeks oflife were used to study the effects of subsequent lighting pattern on performance. Three lighting treatments were used: a constant 23 h/d (L1), a constant 14 h/d (L2) and a step‐down pattern in which the light period was reduced from 22 h/d, by 1 h each week, to 14 h/d at 14 weeks, after which it was kept constant until 18 weeks (L3). Within each lighting treatment there were two feeding treatments: birds were either offered food ad libitum or received a restricted amount of food that was the same for all lighting treatments.

At 18 weeks of age there was no difference between body weights of birds receiving treatments L2 and L3, but birds receiving treatment Li were significantly (P< 0.05) heavier. This difference was independent of feeding treatment. Despite the difference in body weight voluntary food intake was slightly greater in birds receiving treatment L2 than in those receiving Li. As a result, a significantly (P < 0.01) more efficient food conversion was associated with L1 than with L2 and L3.     

Effects of dietary particulate limestone, vitamin K3 and fluoride and photostimulation on skeletal morphology and osteoporosis in laying hens

1. Female chicks of a White Leghorn strain were fed three different diets from one day old: control, additional vitamin K3 (10 mg/kg), and a diet containing a combination of additional vitamin K3, sodium fluoride (10 mg/kg) and limestone in particulate rather than powdered form. At 16 weeks photoperiod was increased for half the birds from 8:16 L:D to 16:8 L:D immediately or by one hour per week to the same ultimate photoperiod for the other half. 2. Age at first egg was lower by 4.0 d for birds on the fast lighting regime but there were no overall effects of lighting on bone quality at either 25 or 70 weeks. 3. Additional vitamin K3 resulted in higher proximal tarsometatarsus cancellous bone volumes at 15 weeks and throughout the laying period compared with controls. Plasma osteocalcin concentrations were unaffected by vitamin K3 supplementation during growth. 4. The combination diet resulted in beneficial responses of 12 to 20% in most bone characteristics in hens at 70 weeks. The magnitude of these effects was similar to a previous study involving a particulate calcium source alone (Fleming et al., Poultry Science, 39: 434-440, 1998b). We conclude that the beneficial effects of the combined treatment over the lifetime of the hens were attributable mainly to the presence in the diet of a calcium source in particulate form.     

Ophthalmopathy in a broiler breeder flock reared in dark-out housing

Eight 22-week-old broiler breeder replacements were presented from a flock experiencing a mild mortality problem. Approximately 2-3% of the birds were not getting onto the slats to eat or drink. The birds had been reared in dark-out houses under an experimental lighting schedule. Upon examination, several birds appeared blind or partially blind; others exhibited a photophobic response. Two birds lacked a unilateral menace reflex. No other gross abnormalities or lesions were noted. Histopathologic sections of the eyes revealed retinal degeneration and detachment with early degenerative lesions in one lens. The breeder flock came into production normally but peaked below average. Light intensity in the pullet house was measured at 0.3 footcandles (3.2 lux). Although the lighting program under which the pullets were grown is suspect, the etiology of the disorder remains unclear.     

Effects of environmental enrichment, fluorescent and intermittent lighting on injurious pecking amongst male turkey poults

1. Under commercial and experimental conditions domestic turkeys often cause injuries to pen-mates by repeated pecking, sometimes fatally. Environmental enrichment or lighting manipulations might be used to mitigate such injurious pecking. 2. This study examined responses to 4 treatments (2 rooms/treatment) of 8 groups of 100, non-beak trimmed, non-desnooded, male domestic turkeys from 1 to 35 d of age. 3. Birds of 1 treatment were reared under conditions approximating to commercial rearing (12L:12D incandescent, Control) whereas the experimental treatments were 12L:12D incandescent plus supplemental ultraviolet radiation, straw supplementation of litter, pecking substrates and visual barriers (Enriched), 12L:12D fluorescent lighting (Fluorescent), and 2(2L:3D):2L:12D incandescent (Intermittent). 4. Compared to control birds, the incidence of injuries caused by wing or tail pecking were both lower in the Enriched but not significantly different in the Fluorescent or Intermittent. 5. Injuries caused by head pecking did not occur in the Enriched rooms but were observed in at least 1 of the rooms with Control, Fluorescent and Intermittent treatments. 6. Despite considerable environmental differences between treatments, there was remarkable consistency within each type of injurious pecking in age at which injuries were 1st recorded (wing pecking, 9.38+/-1.31 d; tail pecking, 20.43+/-2.42 d; head pecking, 27.8+/-2.13 d). The roles of feather emergence, hierarchy formation in wild turkey poults and appearance of feathers are discussed as possible explanations of these consistencies.     

Compensatory growth of broiler chickens is associated with an enhanced pulsatile growth hormone (GH) secretion: Preferential amplification of GH secretory burst mass

1. The present study was conducted to establish the effect of compensatory growth of broiler chickens on pulsatile growth hormone (GH) secretion.

2. Exposing male broiler chickens to intermittent lighting (IL) at 10 d of age was associated with a transient reduction in body weight gain which was followed by compensatory growth from 4 weeks of age onwards. At 34 d of age, cannulated IL broiler chickens manifesting compensatory growth and control chickens reared under continuous illumination (CL) were serially sampled at 10 min intervals over 5 consecutive hours and plasma GH concentrations measured. The resultant GH time series were analysed by deconvolution analysis.

3. The overall mean GH concentration was higher for IL than for GL broilers. The burst frequency did not differ between lighting treatments, but during each GH surge, IL broilers released a higher GH mass which resulted in higher GH amplitude values. As a consequence, GH production rates of IL broilers during the entire sampling session were markedly elevated compared to those of dieir age‐matched CL broilers. There were no differences in the monoexponential GH half‐life.

4. Compensatory growth in broiler chickens is associated with an amplification of GH secretory burst mass. The underlying causal mechanisms remain to be elucidated.     

Cold-induced ascites in broiler chickens and its improvement by temperature-controlled rearing

Pulmonary hypertension syndrome (PHS), also known as ascites, in broiler chickens prevailed in the local area of Ibaraki prefecture, Japan, and was investigated epidemiologically, serologically, and pathologically. PHS developed in chickens older than 35 days of age when rapid increase of body weight started. Approximately 90% of affected birds were males, in which weight increase was greater than in females. Serologic test revealed that PHS broilers had an increase of hematocrit value. Pathologic studies indicated that the heart of affected birds had an obese-induced pressure and cold exposure triggered congestion in the right ventricle/cava and an increase in peritoneal fluid. These changes were consistent with the previous reports of PHS, so we designed the experiment of effects on cold-induced PHS birds in a temperature-controlled house. After the 10 PHS birds at 55 days were reared for 14 days in a temperature-controlled house at 20 +/- 5 C, ascites disappeared in eight birds and hematocrit values decreased to normal range in nine birds. Our finding indicated that temperature-controlled environment may be one solution to reduce mortality in PHS birds.     

Changes in hematological, blood gas, and serum biochemical variables in broilers during exposure to simulated high altitude.

One-day-old broilers were reared until 35 days of age at both natural low (100 m) and simulated high altitude (2133 m) to assess the incidence and development of ascites syndrome. Clinical measurements were conducted at 7, 14, 21, 28, and 35 days of age. Birds reared at 2133 meters exhibited significantly (P less than or equal to 0.05) reduced body weights at 7 through 28 days of age. Total serum calcium and biochemical enzyme activities were found to be altered at 35 days of age. In addition, the high-altitude group had significantly (P less than or equal to 0.05) higher erythrocyte counts, hematocrits, and hemoglobin at 14, 21, 28, and 35 days of age and higher serum inorganic phosphorus at each weekly sample time than birds at the low altitude. Total mortality was 20.3% at 2133 meters and 4.6% at 100 meters. The incidence of ascites syndrome in the high-altitude group ranged from 16.6% to 61.1% during the 5-week experimental period.     

A Study of Electrocardiographic Patterns in a Population of Commercial Broiler Chickens

Olkowski, A.A., Classen, H.L., Riddell, C. and Bennett, C.D., 1997. A study of electrocardiographic patterns in a population of commercial broiler chickens. Veterinary Research Communications, 21 (1), 51-62. A study was completed to characterize the electrocardiographic (ECG) patterns of male broiler chickens. Data were collected from 300 commercial broilers. ECG readings were collected from all birds between 12 and 15 days of age and then twice more at 10-day intervals. The measurements included heart rate and rhythm, QRS complex duration, amplitude and mean electrical axis (MEA), incidence of ascites and incidence of sudden death syndrome (SDS). Eight birds died from SDS and 4 birds died from ascites. Twelve birds were condemned for ascites at the processing plant. The overall population heart rate declined with age. Birds that died of SDS had a higher heart rate, whereas those that developed ascites had a lower heart rate than the remainder of the population. The normal MEA was found to be between 0° and 180°. On average 30% of birds showed left or right QRS axis deviation, and this pattern was observed in 14 of the 16 birds that developed ascites. Several types of cardiac arrhythmias were observed, the most common being premature ventricular contractions (PVC). The incidence of PVC increased with age, ranging from 1% at 12-15 days of age to 8.9% at 32-35 days of age. QRS axis deviation was present in 5 SDS birds. It is concluded that some 30% of the broiler flock tested was at risk of developing heart failure or heart-related disease.     

Responses of broiler chickens to high-frequency and low-frequency fluorescent light.

1. The influence of the flicker frequency on physical activity and energy expenditure of broilers was studied using commercially available high-frequency (HF) and low-frequency (LF) fluorescent lamps in a 23L:1D lighting schedule. 2. Broilers were reared under and adapted to HF. They were alternately subjected to HF and LF during measurement of activity and energy expenditure. 3. In comparison with HF, LF inhibited activity (number and intensity of movements), but did not influence energy expenditure. 4. It was concluded that the 100 Hz flickering of low-frequency light is detected by broilers and has measurable behavioural effects upon them. 5. The results were discussed in relation to current knowledge of human and birds' critical flicker frequency and perception.     

Effect of asymmetrical lighting on the body weight and carcase composition of laying hens and their influence on the efficiency of food utilisation

The body weight, carcase composition and component energy concentrations of laying hens were determined under 17L:7D and 2L:4D:8L:10D lighting regimens.

2. Hens subjected to 2L:4D:8L:10D lighting had lower body weights at end of lay and during most of the laying year, than the 17L:7D control birds.

3. Intermittently illuminated hens had similar absolute water, crude protein and ash contents to, but more water on a proportional basis than, controls.

4. Hens subjected to the 2L:4D:8L:10D lighting regimen had significantly less fat, in both absolute and proportional terms, than the controls.

5. There were no significant differences between the energy concentrations of the fat or fat‐free components of the two lighting groups.

6. There was no significant difference in the regression of fat content on body weight at end of lay for the intermittently and conventionally‐illuminated birds.

7. A prediction of the difference in daily energy requirement, based on egg output, body weight and mean daily body weight gain, very closely matched the actual difference in energy intake. This suggested that the more efficient food utilisation of intermittently‐illuminated hens could be explained by the lower body weight gain of these birds.     

Noise output of hens subjected to interrupted lighting regimens

1. Noise output from domestic hens subjected to an interrupted lighting regimen began before dawn of the apparent day. 2. Noise output did not cease during the scotoperiod(s) which interrupted the apparent day. 3. Differential noise outputs during the 30 min. 4 h and 10 h scotoperiods of a 1L:7(30D:30L):4D:2L:10D regimen indicated that the hen's interpretation of darkness, even within the apparent day, was complex and probably dependent on several factors. 4. Noise output data suggested that the intense feeding behaviour at the end of the apparent day, effected by the interrupted lighting regimen, appeared to prevent the pre-dusk reduction in activity observed in conventionally lighted birds. 5. Noise output was negligible during the scotoperiod which the hen interpreted as night.     

Diurnal‐nocturnal changes in food intake,gut storage of ingesta,food transit time and metabolism in growing broiler chickens: A model for temporal control of energy balance

1. Diurnal—nocturnal changes in food intake, gut storage of ingesta, food transit time and heat production were studied in male broiler chickens reared under a 14L:10D lighting schedule (lights on from 06.00 to 20.00 h).

2. Food consumption during the scotophase was negligible. Peak food consumption during the photoperiod occurred at the beginning of the photoperiod and in the late afternoon.

3. During the photoperiod, the crop and proventriculus/gizzard contained only small quantities of ingesta. However, at the beginning of the scotoperiod, dried ingesta content of crop and proventriculus/gizzard increased by 10.5‐ and 2.76‐fold respectively. This increase was followed by a gradual decrease towards the end of the scotoperiod.

4. Food transit time during the scotoperiod was significantly longer than that during the photoperiod.

5. The daily pattern of heat production closely followed the 14L:10D lighting schedule. Total heat production during darkness averaged 53% of total heat production during the photoperiod.

6. It was estimated that the storage of energy (as ingesta) in the crop and proventriculus/gizzard, followed by its gradual release and the increased food transit time during the night, contributed 75.5% of nocturnal energy needs. It must be recognised that these mechanisms play a major role in the energy balance of the growing chicken during periods without food intake.     

Activation of PKCalpha and pulmonary vascular remodelling in broilers

OBJECTIVE: The present study was conducted to examine the presence of protein kinase Calpha (PKCalpha) in the pulmonary arterioles of broilers during the development of pulmonary hypertension and pulmonary vascular remodelling. METHOD: One hundred and sixty day-old Avian-2000 broilers were divided equally into a control group and a cold temperature group. All the birds were reared in normal temperatures up to day 14, with the lighting schedule at 24 h per day. Thereafter, birds in the cold temperature group were subjected to low temperature by lowering 1-2 degrees C per day to 12-14 degrees C, and then kept constant until day 49, while birds in the control group were still brooded at normal temperatures. All the birds were fed a diet of pellets throughout the study. Samples of blood were taken from the wing vein, and of heart and lung collected after the birds were killed with an overdose of sodium pentobarbitial, at days 24, 32, 39 and 45 of age, respectively. Right ventricle to total ventricle ratio (RV/TV) and packed cell volume (PCV) were measured. Vessel wall area to vessel total area ratio (WA/TA) and mean media thickness in pulmonary arterioles (mMTPA) was examined using computer-image analytic software. Expression of PKC in pulmonary muscular arterioles was assessed by immunohistochemistry and quantified by measuring optical density (OD) using computer-image analytic software. RESULTS: The incidence of pulmonary hypertension syndrome (PHS) was 12.5% in birds exposed to cold, and 3.75% in the control group (P<0.05). PCV in the cold temperature group was elevated after day 32 (P<0.05), and RV/TV ratio increased on day 45 (P<0.05). Both the WA/TA and mMTPA of birds subjected to cold were significantly elevated (P<0.05). The OD values were not significantly increased before day 32 (P>0.05), however, one week later (at day 39 of age), the difference between the two groups was significant (P<0.05). The increased PKCalpha expression was positively correlated with the values of mMTPA and WA/TA. CONCLUSION: PKCalpha expression was up-regulated during the development of pulmonary hypertension. The activation of PKCalpha might be involved in the development of pulmonary vascular remodelling.