The Effect of Growth Intensity and Sex :1- On the Slaughter Value of Broiler Chicks Fattened To Higher Live Weights
Published: January 29, 2014
By: Mostafa Elsabbagh, Animal Production Department-College of Agriculture,Lebanese University
Summary
In this experiment we followed the effect of sex and live weight of broiler chicks of both sexes at the same age on the slaughter value of the chicks
Chicks of the age 49 days of hybrid combination RX fasted 12 hours before slaughtering were divided according to their live weight into categories differing by 100 grams. The live weight of the females varied from 1000 t0 1300 grams, that of the males from 1500 to 2300 grams...
From each category, 10 chicks were selected for the analysis.
The live weight of the chicks was 1848.0+/-22.87 and 1385.8+/-22.03 grams for males and females, respectively.
Sex differences in the live weight and carcass value were found to be highly significantly (p<0.01) higher with males than with females, and the carcass value of the males was higher by 1.25% than females.
Sex differences in the dressing percentage and giblets yield were not significant.
The dressing percentage, carcass value and giblets yield of the females and the carcass value, giblets yield of males showed a highly significantly(p<0.01) increase with the increasing live weight of chicks at the same age and expressed by an increasing part of concave parabola.
The main goal of this experiment was to study the factors affecting the most important indices of broiler carcass and nutritive values in broiler meat chicks.
In an experiment with 150 male and 150 female hybrid broiler chicks ROSSI fed on a litter adlibtum with starter with 22% protein and12.98 MJ ME/Kg and 20% protein and 13.40 MJ ME/Kg as a finisher .It was found from the results of this experiment that the sex of chicks at 49 days of age has a great effect on live weight, carcass value, breast muscle, breast skin, thigh meat, thigh muscle, thigh skin and the total breast and thigh meat percentages.
Values were higher in males than in the above parameters, significantly in carcass value (1.25%), breast muscle (0.50%) breast skin (0.33%) and by 2.17, 1.37, 1.36, 0.35 and 2,34% for thigh meat, thigh muscle, thigh skin and total breast and thigh meat percentages, respectively.
Feeding, Sex, Age –high live weights//Carcass values.
REVIEW OF LITERATURE
The growth of broiler chicks can be expressed by the daily gain that indicates the increasing of the total weight that increase in one day, the amount of growth promoted by voluntary feed consumption, and affected by genetically and environmental factors as sex, age, breed, strain, etc.
Reddy et. al, (19820, Sailor and Seemann (198) found that sex affected the weight gain of broilers significantly and males grew faster than females at all periods.
Changing in basic parameters of fattening of chicks is interesting for broiler chicks of both sexes at different ages, especially for dressing percentages, carcass values. Tan et. al, (1985) reported significant differences in the dressing percentage between sexes fed up to 19 weeks of age; it was 69.8% and 70.1% respectively for males and females.
While Mendes et al (1988) found that the dressing percentage of ROSSI broilers at 8 weeks of age was 73.4, 74.34, 74.75% for males and 71.6,71.08 and 71.2 %for females.
Sailor and Seemann (1986) found that when broiler chicks of both sexes fattened to 70 days of age the breast muscles were 15.6 and 15.2% of the total weight for males and females respectively.
MATERIALS AND METHODS
The biological material used in this experiment originated from the English ROSS I hybrid broiler chicks that fattened under the symbol RX.
The chicks were fattened from 16 January to 11 march .The chicks were selected according to their live weight ,the weight of the males varied from 1500 t0 2300 grams and the weight of females varied from 960 to 1800 grams.
FEEDING PROGRAM
Chicks were fattened on commercial starter mixture BR1 from one day old to 28 days of age with 22% protein and 12.98 MJ ME/Kg, and from the 28th day to the end of the experiment on finisher mixture BR2 with 20% protein and 13.40 MJ ME/Kg.
Vitamin program was applied
Chicks’ management: Chicks were selected and divided according to their live weight to 8 groups both for males and females as follows:
Chicks were fattened in pens on deep litter with a stocking density 15.6 chicks/m2, with automatic chained feeders and round automatic waterers.
Lighting program was 24 hours from one to 14 days of age ,then decreased to reach 16 hours to the end of the experiment.
At the end of the experiment the chicks were weighed individually, tagged on wings by metal numbers and fasted for 12 hours before slaughtering.
The following steps were followed:
- Chicks were weighed and registered the live weight.
- Chicks were killed ,bleeded ,plucked and cooled at 0-5*C
- The head of the chick was cutoff and the neck was separated.
- Chicks were eviscerated and the edible giblets separated. Gizzard was cleaned, gall bladder was separated from the liver.
- Edible giblets and eviscerated carcass were weighed.
- Thighs were cut out from the hip joints.
- Breast was cut out from the shoulders joint.
- Breasts and thighs were weighed separately with the skins.
The following parameters studied in the experiment:
- Live weight after 1 hours of starvation
- Carcass value= weight of the carcass/live weight >< 100
- Edible giblets yield,heart,liver,gizzard,neck without skin
- Dressing % =weight of carcass weight of edible giblets/live weight><100
- Percentage of breast with skin from carcass weight = Weight of breast/weight of carcass><100
- Percentage of breast meat from the total breast weight = weight of breast meat/total breast weight ><100
- Percentage of breast skin of the total breast weight = Breast skin weight/total breast weight ><100
- Percentage of thigh with skin from the carcass weight = Weight of thighs/weight of carcass><100
- Percentage of thigh meat from total thigh weight = Weight of thigh meat/total thigh weight><100
- Percentage of thigh skin from the total thigh weight = Thigh skin weight/Total thigh weight ><100
Evaluation of the results was done by using the t-test-analysis of variance, regression analysis (linear, parabolic functions) according to Snedecor and Cochran (1971).
RESULTS AND DISCUSSION
The average of slaughter value characteristics of male and female broilers are shown in the following table:
Tab1- Slaughter value 1) of broiler chicks:
The live weight of male broilers was 1848.8+/- 22.87 grams (mean +/- standard error of the mean) and 1385.8+/-22.03 grams for females.
Differences between sexes in dressing percentage and giblets yield were not significant, but the carcass value of male broilers was higher by 1.25%than of females (p<o.o1).
In the percentage of breast meat (with skin) no significant differences were observed between broiler sexes, but the percentage of breast muscles were highly significantly higher and the percentage of breast skin was highly significantly (p<0.01) lower in the males than in females. The percentage of thigh meat, thigh muscle, thigh skin and total breast and thigh meat of males was highly significantly (p<0.01) higher than of females.
The portion of breast and thigh meat from carcass was 42.19+/- and 39.85+/-0.374 for males and females, respectively.
The sex differences in live weight and carcass value were found to be highly significantly (p<0.01), this because male broilers grew faster and gave highly significantly higher live weights than females at the same age. Similar observations were made by Mathur and Ahmed (1988), Reddy et al (1982) and others.
Moreover, male broilers showed a significantly higher carcass value(68.08%) than females (66.83%).this may be because the female broilers had a higher quantity of viscera, blood volume, feathers and reproductive organs as a percentage of live weight than males, and due to the fact that females showed a lower carcass value.
The effect of sex on the dressing percentage and giblets yield was found to be insignificant, moreover the male broilers showed a higher dressing percentage (74.36%) than females(73.23%) but a lower giblet yield (6.23%) than females(7.02%).
Similar observations were made by Reddy et al (1988), while Tan et al (1975) on the contrary, found that females had a higher dressing % than males.
Faruga et al (2983), Ehinger (1982), Mendes et al (1988) and others found that males had a significantly higher dressing % than females at the same age.
Tab2: The dependence of slaughter value on live weight of chicks in grams-regression equations:
The dressing percentage, carcass value and giblets yield in females and the carcass value, giblets yield in males showed a highly significantly (p<0.01) increase with the increasing live weight of chicks at the same age.
This dependence was more exactly (p<0.01) expressed by an increasing part of concave parabola than by linear regression equations. The portion of breast meat of females showed a linear increase (p<0.05) with live weight.
CONCLUSIONS
From our results in this experiment we can conclude that the sex of chicks at 49 days of age has a great effect on live weight, carcass value, breast muscle, breast skin thigh meat, thigh muscle, thigh skin and total breast and thigh meat percentages.
From our results in this experiment we can conclude that the sex of chicks at 49 days of age has a great effect on live weight, carcass value, breast muscle, breast skin thigh meat, thigh muscle, thigh skin and total breast and thigh meat percentages.
Values were higher in males than in females in the above parameters, significantly in carcass value (1.25%), breast muscle (0.50%), breast skin (0.33%) and by 2.17, 1.36, 0.35 and 2.34% for thigh meat, thigh muscle, thigh skin and total breast and thigh meat percentages respectively.
References:
Ehinger,F:The influence of feed ,age and sex on the growing performance and carcass quality of broiler chicks from different strains.Arch.Geflugelkde 46 :97-100,1982.
Mendes,A.A-Cury,P:Effect of dietary energy levels and sex on broiler performance and carcass traits.Env.Poult.Cnf 24-543-550.1998
Reddy,Y,G –Siddiqui,S.M-Mathur,C:The effect of strain,sex,age on weight gains, feed efficiency, carcass yields and composition of broilers-Indian Veter.J .59:209-216,1988
Sailer,K-Seeman,G:Newere Versuchsergbnisse Zur Broiler Langnost.Lohmann Infor.5-6 ,1986.
Tan,K.Chen,P>C:Meat,skin and bone yields of broilers.Singapore .J.3 :13-20, 1987
To read part 2, The Effect of Growth Intensity and Sex: 2- On the Chemical Composition of Breast and Thigh Meat, please click here
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