2 ASIAN POULTRY MAGAZINE – March 2008

Reducing stress in poultryremains a topic of concern amongstproducers and scientists. Anincreased concentration of glucosein blood and a decreased proteinlevel are associated with stressinduction along with an increase incirculatory cortisol level. Atemperature >30oC represents aheat-stressed condition for birds andis one of the most commonstressors that affect the productioncriteria in poultry in the Indiansubcontinent. Methods to alleviatethe effect of heat stress focus onmanipulating the diet. Trivalentchromium (Cr3+) may be used as atool to handle such stress situation.Recommendation with regards tothe exact inclusion level of Cr indiet is not yet available.

Chromium picolinate is perhapsthe most widely explored compoundin research work conducted on Cr.By virtue of a different absorptivepathway, Cr picolinate is more bio-effective than inorganic compoundslike Cr chloride. The presentexperiment was conducted to assessthe efficacy of Cr picolinate as adietary supplement for heat-stressedbroiler chickens.

Bird husbandry and dietarytreatments

Cobb 400 broiler chickens (n =225), obtained 12 h post hatchfrom a local hatchery, weresupplemented with 0 (control), 0.5mg and 1.0 mg Cr/kg (asChromium picolinate) from 10 to40 days of age. A flock of 15 chickswas slaughtered on day 1 for

assessing the blood metaboliteprofile and carcass traits at the pre-experimental stage. The birds wereplaced in pens (1.5 m x 1.5 m) onlitter floors. The pens, each housing10 birds, were the replicates andthere were 7 replicates in eachtreatment group. The birds were feda basal starter diet till day 10 andCr was supplemented to the diet as

Cr picolinate from day 11 onwards.The starter diet was fed to day 30and a finisher diet for the remainingperiod (see Table 1 for dietcomposition). Temperature insidethe experimental room was kept at35-36˚C throughout theexperimental period to put the birdsunder a moderately heat stressedcondition which was evidenced by

Chromium as a tool againstheat stress

A study in India by SUDIPTO HALDAR and TAPAN K.GHOSH* indicates that supplementation of chromium in the

form of chromium picolinate may be an effective tool foralleviating heat stress in nutritionally restricted

broiler chickens.

Figure 1: Live weight (kg), live weight gain and FCR.

Liveweight Liveweight gain FCR0.0

0.5

1.0

1.5

2.0

2.5

Control 0.5mg Cr 1.0mg Cr

1.5 1.8 1.6 1.5 1.7 1.6 2.0 1.7 1.9

Significant improvement in performance in birds receiving 0.5mg supplement Cr

Figure 2: Live weight gain at different age intervals.

0D10 D20 D30 D40

200

869g

704g

623g

The maximum benefit ofCr supplementation was

observed during thefinisher stage

400

600

800

1,000

Control

0.5mg Cr

1.0mg Cr

Sudipto Haldar Tapan K.Ghosh

ASIAN POULTRY MAGAZINE – March 2008 1

panting and dispersed distributionof the birds within the pens.However, no mortality was recordedduring the study

Blood was collected on day 1during the initial slaughter and onday 40 prior to the final slaughter.Birds were fed ad-libitum during thestarter phase (d 1-30) but physicalfeed restriction was imposed duringthe finisher (d 31-40) phase. Grosscarcass traits including the carcassyield was determined. Meat wasanalyzed for ash, protein and fat inthe carcass obtained on days 1 and40 and the total accretion of thesaid nutrients was calculated. Theefficiency of protein utilization in

terms of live weight gain per unitprotein consumed and the proteinconversion efficiency expressed interms of protein intake for eachunit of protein accretion wascalculated.

Benefits of Chromiumsupplementation

The results of this trial indicates

Figure 3: Yield (g) of dressed carcass, breast and legs.

Dressed carcass Breast Leg0

400

800

1,200

Control 0.5mg Cr 1.0mg Cr

833 985 889 259 324 266 295 335 314

Cr improved carcas yield

Table 1: Ingredients and chemical composition of the basal diet.

Ingredients Starter Grower

Corn 580 620Soybean meal 46 350 322Sunflower cake 24 –Fat 30 40Salt 1.47 1.47Dicalcium Phosphate 8.8 9.5Lysine sulfate 0.3 1.6DL Methionine 0.8 1.3Trace mineralsa 1.5 1Maduramycin 0.5 0.5Enzymes 0.26 0.26Ascorbic acid 0.1 0.1Toxin binder 1 1Organic acids 1 1Vitamins 0.27 0.27

Total, kg 1000 1000

Nutrients, DM basis

Proteinb, % 21.0 19.4MEc, Kcal/kg 3083 3203Lysinec, % 1.3 1.2Methioninec, % 0.5 0.5M+Cc, % 0.73 0.68Calciumb, % 0.35 0.42Available Pc, % 0.31 0.37Chromiumb, mg 0.18 0.20

a Contained (per kg) manganese 40 mg, iron, 30 mg, zinc 25 mg, copper 3.5 mg, iodine 0.3mg, selenium 0.15 mg, choline chloride 200 mg

b estimated in laboratoryc calculated values

Figure 4: Protein ultilization andconversion efficiency.

0

1

2

3

Gain:Intake Intake:Accretion

Control

0.5mg Cr

1.0mg Cr

that dietary Cr supplementationimproves the performance andcarcass traits of the broiler chickensand the effects were perhapsmediated through a reduction inthe circulatory cortisol level.

Cr supplementation improved allthe performance and carcass relatedtraits studied. The dose level of 0.5mg Cr/kg diet showed superioreffects compared to the higher doselevel of 1.0 mg Cr/kg diet. Bothfinal live weight and total liveweight gain in 40 days improved(P<0.05) due to Cr supplementation(Figure 1). Consequently the feedconversion efficiency (FCR) alsoimproved with Cr supplementation(P<0.05).

Table 2 highlights the rather largeperformance and carcass responsesto the 0.5 mg/kg Crsupplementation.

Live weight gain was similar

Figure 5c: Circulatory cortisolconcentrations (mmol L-1)

Figure 5a: Circulatory serum protein(g I-1) and glucose (mmol L-1) level.

2 ASIAN POULTRY MAGAZINE – March 2008

1000

1100

1200

40

30

20

10

0

Control 0.5mg Cr 1.0mg Cr

Protein g/L Glucose mmol/L

Control

0.5mg Cr

1.0mg Cr

41.1

35.8

38.2

8.9

1232.1

mm

ol/L

1116.9

mm

ol/L

1103.5

mm

ol/L

7.9

9.2

Table 2: Summary of performance and carcass responses to 0.5 mg/kg Cr.

Treatment Control + 0.5 mg/kg Cr Change (%)

Liveweight, 40 d, g 1415b 1755a +16Liveweight gain, 1-40 d, g 1472b 1714a +16.4FCR, 1-40 d 2.01b 1.73a +14Liveweight gain, 31-40 d,

Grams 623b 869a +39Grams/day 62.3b 86.9a +39

FCR, 31-40 d 2.21b 1.65a +25.3

Carcass yield, g 833b 985a +18Breast, g 259b 325a +25Legs, g 295b 335a +30.5Carcass yield, % 60 62 +3.3

ab P< 0.05

Table 3: Chemical composition, nutrient accretion (g/kg fresh weight) andefficiency of protein conversion in broiler chickens supplemented with gradeddoses of Cr.

Chromium, mg/kg diet PooledMeasurement 0 0.5 1.0 SE Significance

Moisture 712 724 724 1.3 **Ash 120.2 119.9 120.2 3.17 NSCrude protein 21.6 22.7 21.9 0.37 NSEther extract 7.4 6.3 6.5 0.25 **Protein accretion 317.5 389.1 344.5 8.79 *Fat accretion 109.9 107.1 100.9 3.95 NSAsh accretion 175.9 204.8 188.6 6.69 NSProtein intake g: 1.85 1.52 1.74 0.04 **Protein accretion g(1-40 days)

Each treatment group consisted of 7 replicates of 10 Cobb 400 unsexed broiler chickens witha mean live weight of 41.4±0.23 g at 12 h post hatch. Slaughter was performed after 40days feeding trial by taking 2 birds at random from all the 7 replicates under each treatmentgroup. The data were pooled replicate wise for calculation and statistical analyses.

across the dietary treatments duringthe starter phase (1-30 days of age)and hence the utilization efficiencyfor energy and protein also did notdiffer due to Cr supplementationduring this stage. However, theirresponse changed during thefinisher stage (31-40 days of age)(Figure 2). Birds receiving Crsupplementation gained more(P<0.05) body weight during theage interval of 31-40 dayscompared to the control group. Asa result, the efficiency of energyand protein utilization alsoimproved (P<0.05) during thatphase (Table 3). This is importantas it was during this stage ofgrowth when physical feedrestriction was imposed.

This study, therefore, indicatesthat supplementation of Crpicolinate may help the birds in

efficiency (Table 3). Measurement of serum

metabolites revealed a decline(P<0.05) in circulatory proteinconcentration in chickens receivingdietary Cr supplementation. Thismay be due to enhanced utilizationof absorbed protein for conversioninto tissue protein. The lower

improving nutrient utilisation. Hot carcass weight and

eviscerated carcass weight improved(P<0.05) due to Cr supplementationand the effects were greater in birdsreceiving 0.5 mg Cr/kg. Weight ofthe whole breast increased(P<0.05) and those of the frameand the legs tended to increase(P<0.1) when Cr wassupplemented.

Fat content of the meat decreased(P<0.05) while protein accretionincreased (P<0.05) due to Crsupplementation. Hence, Crpicolinate was effective in reducingcarcass fat and increasing leanmeat production. The efficiency ofprotein conversion to meat proteinalso improved due to Crsupplementation with the birdsreceiving 0.5 mg supplemental Crshowing significantly higher

Figure 5b: Circulatory serum cholesterol andtryacylglycerol (mmol L-1)

ASIAN POULTRY MAGAZINE – March 2008 1

40

30

20

10

0Cholesterol Triacylglycerol

mmol/L mmol/L

(P<0.05) circulatory glucose concentration in the Crsupplemented birds suggests an increased turnover rateand utilization of glucose at the tissue level. The higherglucose level in the control group of birds may be dueto the heat stress the birds encountered during theexperiment and the results, therefore, further bolsteredthe stress alleviating effects of supplemental Cr (Figure5a).

The most intriguing aspect of the present study wasthe circulatory lipid lowering effect of Cr (Table 5b).Relative to the control group, the serum cholesterol andtryacylglycerol concentrations were lower (P<0.05)when 0.5 mg Cr was supplemented in the diet.

These above findings may be explained by thecirculatory cortisol level (Figure 5c) which was reducedwhen the birds received supplemental Cr (P<0.05).However, it is difficult to explain the lack of linearity indose response. It has been reported earlier that likemany other trace elements, Cr may also have a “zone ofbiological action” and elicits significant response only upto a certain dose level beyond which no beneficial effectof supplementation could be obtained.

The present study, therefore, indicated thatsupplementation of Cr in the form of Cr picolinate maybe an effective tool for alleviating heat stress innutritionally restricted broiler chickens. The effects aremediated via a cortsol lowering effect of Cr which shiftsthe balance more towards anabolism leading to agreater nutrient utilization efficiency and production oflean meat.

Inclusion of 0.5 mg Cr as chromium picolinate per kgdiet may be recommended as an innovative and efficientfeeding management tool for a better return frombroilers. �

* Dr Sudipto Haldar (sudipto.haldar@rediffmail.com) PhD, is Senior Lecturerand Dr Tapan K Ghosh, PhD, FANAI, is Professor and Head, Department ofAnimal Nutrition, Faculty of Veterinary & Animal Sciences, West BengalUniversity of Animal & Fishery Sciences, Kolkata, India. A list of references isavailable from the senior author.

Control

0.5mg Cr

1.0mg Cr