JWSS - Journal of Water and Soil Science

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This experiment was conducted to study egg production traits in a flock of native fowl from Isfahan region and their crosses with three improved exotic breeds. Sexual maturity (SM), weight of the first egg (WFE), number of eggs (EP), egg weight (EW), feed intake (FI), and feed conversion ratio (FCR) were recorded individually during laying period up to 52 weeks of age. There were no significant differences (P < 0.05) in WFE between the four groups, but the difference between the four genetic groups was highly significant (P < 0.01) for SM, EP, EW, FI and FCR. During laying period, pooled coefficients of heritability (sire component) for SM, WFE, EP, EW, FI and FCR were estimated to be 0.24 ± 0.10, 0.03 ± 0.08, 0.41 ± 0.12, 0.48 ± 0.12, 0.13 ± 0.09 and 0.18 ± 0.09, respectively. In combined analysis, part record egg production (SM to 34 weeks of age) was positively correlated (genetically and phenotypically) with EP up to 52 weeks of age (r_g = 0.74 ± 0.11, r_p = 0.71). The values suggested that there is a relatively appropriate relationship in the combined groups analysis. In addition, EP up to 34 weeks of age was negatively correlated with FCR during the same period (r_g = -0.92 ± 0.53, r_p = -0.81).The estimated genetic and phenotypic correlation in this study suggested that selection based on part record egg production can not only be used successfully to improve EP during full record, but may also cause a better laying performance during laying period.

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To estimate heritability, and genetic and phenotypic relationships and also to study the effect of sex and rearing environment on body weight, weight gain, feed consumption and feed conversion coefficient, the data from 1200 pedigreed male and female chickens from three genetic groups including 90 sires were used. The included genetic groups were crosses of native chickens and an exotic breed (group A), native chickens which were selected for two generations on the basis of 8th week body weight (group B) and a control group of native chickens (group C). All the chicks were reared up to four weeks of age on the ground in separated pens according to their sire groups. In order to calculate feed conversion coefficient, 498 chicks were placed in individual cages during four to ten weeks of age. The results showed that the cross group (A) compared to the other two groups had a higher body weight at 2, 3, 6, 8 and 10 weeks of age. Weight gain, feed conversion coefficient and consumption at periods of 4-6, 6-8, 8-10 and 4-10 weeks were also higher in the cross group. Genetic groups B and C, in spite of better performance of group B for most of the traits, did not have any significant differences for the compared traits. Estimated heritabilities on the basis of sire variance component showed that these traits were medium to highly heritable. Estimated heritabilities for feed consumption at different ages ranged from 0.15 to 0.44 which at any age was lower than that estimated for feed conversion coefficient. Genetic and phenotypic correlations between growth traits were positive and, in most of the cases, high. Correlations between nutritional traits at different ages were variable.

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Data of 1200 male and female chicks from 90 sires were used to estimate the heritabilities as well as genetic and phenotypic correlations of body measurements and carcass characteristics in three genetic groups, namely, crosses of native chickens with an exotic breed (group A), native chickens which were selected for two generations on the basis of 8th week body weight (group B) and a native control group (group C).

The effects of genetic group, sex and system (litter vs. cage) on body measurements (shank and breast traits) and carcass characteristics were studied. Data of body measurements were collected at 6th week of age, and carcass traits were recorded at slaughter time at 10th week of age (except breast angle which was recorded at 8th week).

All carcass traits and body measurements except shank were significantly affected by genetic groups (P<0.05). Sex and system of rearing did not have any significant effect on body measurements and carcass traits. Estimated heritabilities for body measurements and carcass traits showed a wide range. Breast and shank measurements had the lowest and those related to abdominal fat had the highest heritabilities. Phenotypic correlations for all of the body measurements were lower than genetic correlations among these traits. Genetic correlations between body measurements and carcass characteristics were mostly significant

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In this study 2510 records of reproductive traits from the mating of 879 ewes with 164 rams of Bakhtiari sheep breed, during 1989 to 1997, were used in order to estimate the effects of environmental factors on their reproductive performance.

The mean and standard errors of reproductive traits were as follows: conception rate, 0.9±0.01 number of lambs born per ewe exposed, 1.06±0.01 number of lambs born alive per ewe exposed, 1.01 ±0.0l, number of lambs weaned per ewe exposed, 0.93±0.01 litter size alive at birth, 1.10±0.01 litter size at weaning, 1.01±0.02 and number of lambs weaned per lambing ewe, 1.09±0.01. The effect of joining year was highly significant (P, 0.01) for all of the considered reproductive traits. Age of ewe at joining time was also a significant (P<0.05 and 0.01) source of variation for most of the reproductive traits. Maximum reproductive performance occurred for ewes of 4 to 5 years of age. Mating time was also a significant factor (P<0.05 and 0.01) for all of the reproductive traits. Maximum reproductive performance occurred for ewes mated during the first half of the mating season. Type of birth was a highly significant factor (P<0.0l) for the number of lambs alive and weaning traits. However, due to significant effects of environmental factors on considered traits, and in order to increase reproductive efficiency, one should improve environmental conditions (barn, management, feeding system and ... ) as well as organizing mating plan for the first half of the mating season and make a suitable age combination of ewe herd. In this combination, decreasing the percentage of ewes older than five years could benefit herd performance.

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In order to estimate the heritability of morphological characters of worker honey bee and honey yield, 30 queen-mothers were selected randomly from the apiary of Research Center of Animal Science and Natural Resources in Isfahan Province. From each queen-mother, five queen-daughters were reared and introduced to equalize colonies after natural mating of queens. Summer honey yield was measured, while fall honey production was calculated from area of sealed honey combs. The total honey was calculated by adding summer honey production to fall honey production. Morphological characters were measured under a stereo-dissecting microscope fitted with a calibrated micrometer reticle according to Ruttners method (1985).

 Heritabilities were estimated by intraclass correlation method. Heritabilities of summer, fall and total yearly honey yields were estimated to be 0.64, 0.51 and 0.30, respectively. Estimates of heritability of morphological characters for probscis length, tibia length, femur length, metatarsus length, metatarsus width, forewing length, forewing width, cubital index, hindwing length and number of hamuli were 0.64±0.08, 0.45±0.07, 0.50±0.07, 0.47±0.07, 0.33±0.06, 0.42±0.06, 0.89±0.10, 0.5±0.07, 0.94±0.10 and 0.45±0.07, respectively. It could be concluded that in order to increase honey yield in either season (summer or fall), selection must be based on the amount of honey yield in the corresponding season. Thus, heritabilities of forewing and hindwing lengths were high selection according to these morphological characters would, therefore, change the size of these characters.

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This experiment was conducted to estimate genetic parameters of some of the important traits of silkworm in two populations, namely, Japanese and Chinese lines in Iranian Silkworm Rearing Co-Natanz. Based on single pair mating method, 9 male moths mated with 9 female moths and then raised under standard environmental conditions. Performance of 30 progenies of each pair was recorded.

Heritability coefficients (parental full-sib method) of single cocoon weight (CW), shell weight (SW), pupal weight (PW) and shell ratio (SR) were estimated to be 0.209±0.123, 0.228±0.129, 0.174±0.109 and 0.044±0.042 in the Japanese race and 0.196±0.1l8, 0.234±0.132, 0.159±0.103 and 0.00, in the Chinese race, respectively. Genetic and phenotypic correlation between CW & SW were 0.645 & 0.957, CW & PW, 0.962 & 0.982, CW & SR -0.351 & 0.123, SW & PW, 0.496 & 0.871, SW & SR, 0.265 & 0.457, PW & SR, -0.446 & 0.169, respectively. Selection, based on heritability coefficients of single cocoon weight and shell weight, can be applied successfully to genetic-gain in this trait. Based on correlation coefficients between traits, selection for shell weight can be applied successfully to improve other traits such as single cocoon weight and shell ratio.

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To estimate the relationship between honey yield and some of the morphological characters, five queen-daughters from each of 30 queen-mothers were studied. The queen-mothers were selected randomly from the apiary of Research Center of Animal Science and Natural Resources in Isfahan Province. Summer honey yield was measured from the difference of honey comb before and after honey extraction while fall honey production was calculated from area of sealed honey combs. Morphological characters were recorded using a stereodissecting microscope fitted with a calibrated micrometer reticule according to Ruttner’s procedures. The mean of honey yield for a year was estimated to be 10.05 kg. Phenotypic correlations between yearly honey production and summer and fall honey productions were estimated to be 0.49 and 0.88, respectively, while the correlation between summer and fall honey yields was low (0.019). There were significant correlations between summer honey yield with cubital-b index, tibia length and forewing width (0.28, 0.27 and 0.25, respectively). Also there were significant correlations between metatarus width with total and fall honey yields (0.22 and 0.23, respectively). Genetic correlations between metatarus length and cubital index with summer honey yield were negative (-0.75 and -0.45, respectively). It may be concluded that due to the high correlation between summer honey production and total honey yield, one could improve yearly honey production by selecting on the basis of summer yield of colonies. Among morphological traits, metatarus length, forewing width and cubital index could be used in the breeding plan in order to increase honey yield.

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In this study, 14322 growth trait records of 2387 sheep bred and reared in the Rearing and Breeding Station of Bakhtiari Sheep during 1989-1997 were used to estimate the phenotypic, genetic, and environmental trends for some of the growth traits using Animal Model for lambs, rams, and ewes. The genetic trend of birth weight, weaning weight, six month's weight, daily gain from birth to weaning, daily gain from weaning to six month and daily gain from birth to six month were 12.2 (+2.9), 19.6 (+5.5), 28.7 (+8.7), .15(+0.04), 0.06 (+0.05) and 0.014 (+0.04) gr. for ewes as an indicator of genetic level of the herd respectively. Also, average of the genetic change rate per year for rams and lambs were calculated. Overall, the maximum progress rate was for six-month body weight (28.7 gr. per year) and the next was weaning weight (19.6 gr. per year). The results for lambs and rams also showed that these traits had the same rank for the genetic progress. The progress could be due to direct selection for these traits in the selection index criterion although there were negative phenotypic and environmental trends during the study years. Negative phenotypic and environmental trends could be due to bad environmental conditions, especially to nutrition of the sheep in an unsuitable (drought) climate during the study years. .

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In a completely randomized design, the effects of six different additive compounds including limestone, hydrochloric acid, zeolite, aluminum sulfate, pad ammoniac, and fatty acids on nitrogen, pH, temperature, moisture, water soluble phosphorus, and microbial count of litter of broiler chicken were investigated. Each compound was added at a level of one kg/m² of litter. Six–hundred-and-sixteen (616) day- old broiler chickens (both sexes) were divided into 28 groups, 22 chicks per group. Four replications were allocated to each treatment from 1 to 56 days. All groups were fed with the same diet. Litter moisture was not affected by the treatment. Experimental treatments significantly (p<0.05) influenced the litter pH on day 21. The lowest pH was obtained with aluminum sulfate and the highest pH was obtained with limestone. At the end of the experimental period, all treatments had nearly the same pH levels. Litter temperature was not affected by the treatments . Experimental treatments had a significant (p<0.05) effect on litter nitrogen and bacterial count. Correlation between litter pH and nitrogen was significant and negative (r = -0.95, p<0.05). Effect of treatments on soluble P was significant and the lowest soluble P belonged to aluminum sulfate and pad ammoniac. Correlation between soluble P and pH was positive (r = 0.48, p<0.05). The results showed that some chemical compounds can be used to reduce litter pH, nitrogen, and soluble P and their effectiveness diminishes as chicks grow older.

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In order to assess and determine amino acids profile and their availability in different sorghum grain (SG) varieties, three SG varieties including low tannin (0.09% , LTS), medium tannin (0.19%, MTS) and high tannin (0.37%, HTS) were grown at the same location. The grains were analysed for their proximate analyses, tannin and amino acids. True amino acid availability (TAAA) was obtained by Sibbald’s method using ceacectomized single comb leghorn cockerels. The results showed that methionine and cystine were the first and the second limiting amino acids, respectively in LTS and MTS. But in HTS, lysine (0.166%) was the first and methionine (0.176%) was the second limiting amino acid. Methionine content was 0.114% , 0.182% and 0.176% for LTS, MTS and HTS, respectively. Although, crude protein was lower in HTS (10%) than the other SG, but histidine, methionine and isoleucine were higher for HTS in comparison to LTS and MTS. TAAA decreased when tannin content increased and all amino acids had a lower availability in HTS than LTS and MTS (P<0.05). Methionine in HTS and LTS and glutamic acid in MTS had the highest availability. The availability of proline was most affected by tannin, and its availability was 91.55% for LTS, 84.82% for MTS and 22.82% for HTS (P<0.05).