CROSSBREEDING is used in order to take advantage of the different and complementary strong points of two or more breeds and to utilize hybrid vigor. In this study the results of sheep CROSSBREEDING have been reviewed from published over the last years in Iran. The results showed that much of the CROSSBREEDING in the sheep industry in Iran due to incorrect selection of breeds was not suitable. The main disadvantages points of Iranian sheep are low reproduction performance, low longevity, insufficient growth rate, unsuitable carcasses composition and feed efficiency, respectively. While, in the most CROSSBREEDING schemes have been done between Iranian breeds of sheep, focused on improve growth traits and reduced fat-tail weight, which created low and no significant changes in crossbreds for these traits, leading to reducing economical efficiency and unsustainable of rearing sheep in semi-intensive or village system over last years. Sustainability could been achieved by combining desirable characteristics from the indigenous breeds to keep fitness and marketability with those of specialist exotic breeds that had already demonstrated genetic potential for traits of economical importance for commercial production. However, research findings suggested that in well-planned efforts to create composite breeds (with minimum 50% native) using the prolific breeds (such as Romanov), with high mothering ability, low maturity age, suitable carcass composition and medium ewe body weight could increased productivity of sheep in village system in Iran.

Supplementary experiments especially for estimation of general and special combining abilities are necessary for introducing and supply of new silkworm hybrids. These genetic parameters investigated at four Japanese pure lines including Xihang1, Xihang2, Xihang3 and 101433 and three Chinese pure lines including Koming1, Koming2 and Y. Twenty hybrids obtained using Chinese and Japanese pure lines crossing. Effects of general combining abilities at Japanese pure lines (JGCA) were significant for total traits except pupae vitality percentage, and double cocoon percentage. Also, effects of general combining abilities at Chinese pure lines (CGCA) were significant for total traits except produced cocoon number, low cocoon percentage, and cocoon shell percentage. Effects of special combining abilities (SCA) were significant for alive larvae number, alive pupae number, produced cocoon number, cocoon shell weight, and cocoon weight. Cocoon weight and cocoon shell weight traits had high additive genetic variance and also they are under heterotic and non-additive genetics effects. Therefore, CROSSBREEDING is the effective method for improvement of these economical characters in studied pure lines.

In order to study of variance components, heritability and genetic correlation of some economic traits, were used collected data during 2004-2007 in hybrids of six lines of silkworm. In all hybrids, cocoon weight heritability was higher than cocoon shell weight’s heritability. Heritability of cocoon shell percentage was lower than other traits. There was a high and positive genetic correlation between cocoon weight and cocoon shell weight and there was a low genetic correlation between cocoon weight and cocoon shell percentage. Heterosis effect on means of cocoon weight and cocoon shell weight was positive and increase in heterosis percentage increased means of this traits. Along increase in recombination percentage in cocoon shell percentage, mean of this trait increased. The results showed that there was an inverse relationship between heterosis and recombination effects. Also genetic gain and means of traits in 31, 32 and their hybrids were upper than others hybrids. So it is expected that the use of these liens is better in commercial level.

The study was conducted to investigate the fatty acid profile of intramuscular fat in longissimus lumborum (LL) of three genotypic groups: Qazvinian native (Q, n=10), crossbred Qazvinian native × Saanen breed (QS, n=10) and backcrossed Qazvinian native × Saanen breed (QSS, n=9) male kids. All of kids were weaned at 75-days-old and then fed with a diet consisted of concentrate (70%) and alfalfa hay (30%). The kids were slaughtered with an average age of 130 days and immediately samples of LL muscle were col-lected. Data were analyzed through one-way ANOVA using the generalized linear model (GLM) proce-dure. The total differences among genotypic groups were evaluated by a canonical discriminant analysis (CDA). The concentration of intramuscular fat (g/100g meat, Q=0. 94, QS=2. 01 and QSS=1. 05) and satu-rated fatty acids (SFA; Q=40. 87, QS=43. 25 and QSS=36. 9), polyunsaturated fatty acids (PUFA; Q=12. 99, QS=13. 89 and QSS=22. 41), total conjugated linoleic acids (CLA, Q=2. 1, QS=2. 32 and QSS=1. 02) and desirable fatty acids (Q=73. 63, QS=67. 18 and QSS=74. 87) as g/100 g total fatty acids between genotypic groups were significant (P<0. 05). Furthermore, the PUFA: SFA and linoleic (C18: 2 n-6): alpha-linolenic acids (C18: 3 n-3) ratio in genotypic groups were significant (P<0. 05). The genotypic groups were separated by CDA, based on their meat fatty acids profile. Results demonstrated that CROSSBREEDING could significantly change the intramuscular fatty acids profile. Therefore, it can be concluded that the fatty acids profile in crossbred kids are better than that of native Qazvinian kids. In these experimental conditions, results of the present study demonstrated that CROSSBREEDING could be a suitable strategy for producing meat with higher concentration of unsaturated fatty acids with beneficial properties for health of consumers.

In this study, the effect of CROSSBREEDING were studied on local cattle performance, using information Holstein and Brown Swiss crossbred cows collected from 1993 to 2003 by Animal Breeding Center of Iran (ABCI). Milk and fat yield traits were considered in this research The data were analyzed by least squares method with a model that included fixed effects of years and season of birth, genetic groups, lactation and region. Statistical analysis using least squares methods showed significant effects of genetic groups, lactation, region, year and season of birth on milk and fat yield in crossbred cattle (p<0.001). The average milk and fat yield were 1599.15±90.52 and 1989.54±110.15 and 2148.94±91.81 kg 60.71±3.34 kg, and 82.26±4.59 kg and 85.27±3.42 kg for local and Brown Swiss × Local and Holstein × Local crossbred cows, respectively. The highest values for both traits were for the cows having 87.5% Holstein and 62.5% Brown Swiss inheritance and lowest values for those having 12.5% exotic inheritance. Estimates of breed and individual heterosis effects carried out with Weight Least Square method. These effects for Holstein × Local crossbred were 20.9 and 15.32 kg for milk yield, 867 and 651 gr for fat yield.It was cocluded that the productive potential of local cattle can be increased by using exotic semen of genetically superior sires, through intensive management and with effective disease control program me.

Cross-breeding of grass carp and bighead carp resulted into viable hybrid. Artificial propagation was induced by I.P. injection of LRH-A. Percentage of egg fecundity, hatching ratio and active swimming larvae were found to be 88%, 90% and 90%, respectively. Larval development of hybrids during incubation was normal and nearly identical to other Chinese carps until the fifth day. Then they were transferred into 400 m2 ponds for further rearing. The high mortality rate of 60% "vas observed in the first day of feeding, due to the failure in development of gill and mouth of hybrids. During the early life stage, the larvae were zooplankton feeder and then turned to a mixed phyto-zooplankton feeding regime and finally after day 48 were completely phyto feeder. Morphological analysis on color, scales, structure of fins, mouth, body shape, body length, vertebral bones, body ratios and the form of pharyngeal teeth of the hybrid showed significant differences with control fish. Furthermore, blood smears of hybrids indicated different shape and cell volume in the erythrocytes in comparison with control. Chromosomal preparation also indicated that the majority of hybrids were triploid (2n=72) as well as some diploid (2n=48) whereas both the grass carp and bighead carp were totally diploid with 2n=48.The proximate analysis results of hybrids meat showed different amount in protein, fat and ash with control, too.

Among the types of foods that are consumed to meet the physiological needs of humans, animal protein is more valuable than other nutrients in terms of nutritional value and nutrients. Today, consumers are looking for healthy and quality foods. Therefore, knowledge of the qualitative characteristics of meat is considered to be important. In this study, the quality and durability characteristics of Arabia and Arabia -Romanov meat were studied during 7 days of ageing period under commercial conditions at 4 °C. Samples were taken from the top round section including Semimembranosus muscles. This research was conducted as a randomized complete design. One-way ANOVA and Fisher test were used at 5% statistical level to study the differences between treatments. Finally, the results were analyzed using Minitab version 16 software. The pH value for Arabia meat decreased from 6.33 immediately after slaughter to 5.7 and for the Arabic-Romanian meat, the mean of 6.36 immediately after slaughter, decreased to 6.05 after 168 hours. The mean value of pH indicating that there was no statistically significant difference between treatments. The results showed that there were significant differences between the two treatment in characteristics of texture, sensory and cooking loss (P <0.05). In general, Arabia- Romanov meat has a higher overall acceptance rating and desirable texture characteristics.

Widespread immigrant beekeeping activity, inadequate quality queen bee production and the excess of uncontrolled CROSSBREEDING are great problems for the quality of honey bee races in Türkiye. However, the effects of uncontrolled CROSSBREEDING on the spermatological parameters are not fully known. In this study, samples were analyzed in terms of morphometric parameters such as cubital index, hantel index and discoidal shift. Drones belonging to the same colonies were investigated in terms of spermatological parameters such as total motility, Plasma Membrane Integrity (PMI), Mitochondrial Membrane Potential (MMP) and spermatozoa concentration (SCON). The wing index values of the samples were similar to the wing values of some races. Racial similarities rates were50% Caucasian (A. m. caucacia), 49% Anatolian (A. m. anatoliaca), 24% Brown (A. m. mellifera), 13% Italian (A. m. ligustica) and 8% Carnolian (A. m. carnica). These results showed that the expected Anatolian race in the region had changed greatly and there is a danger of CROSSBREEDING of bee races (Apis mellifera anatoliaca) in Central Anatolia Region. The averages of spermatological parameters were 85% motility, 82% PMI, 78% MMP and 5.9 × 109/ml sperm concentration. In addition, no significant correlative relationship was found between morphometric and spermatological parameters (p˃0.05). In this study, the samples of honey bee colonies in the Central Anatolia Region showed random and uncontrolled CROSSBREEDING among different races. The spermatological parameters were found to be sufficient for fertility but there was no significant relationship detected statistically between the spermatological and morphometric parameters.

The study was designed to evaluate the growth performance of exotic dual-purpose chicken breed of Koekoek (K) and Kuroiler (Ku) crosses with an improved Horro (H) chicken under reciprocal mating to select potential crosses for development of a synthetic breed in Ethiopia. The experiment was carried out on seven genotypes, including three pure lines (i.e., Horro, Koekoek, Kuroiler) and their direct (K × H, Ku × H) and reciprocal crosses (H × K and H × Ku). A total of 446one-day-old chicks from the seven genotypes were randomly distributed between pens using a completely randomized design with three replications (experiment period?). Data on body weight at hatch (DO), 4, 8, 12, 16 and 20 weeks of age, body weight gain, feed conversion rate (FCR) and mortality rate were calculated during the experiment. The CROSSBREEDING effects were estimated to select the best genotype as a dam or a sire line in the synthetic breed for the next generation. The result showed that the highest mean body weight (P < 0.05) and body weight gain were related to Horro×Kuroiler crossbred chicken that followed by Ku×H, and pure Ku at most of studied ages. Average feed intake was comparable among genotypes. Additive (Ae), maternal and heterosis effects for body weight were significantly (P < 0.05) positive at most ages for both crosses. Additive effects range from 1.79 to 10.1% for Horro-Koekoek crosses, whereas it ranges from 1.6 to 44% for Horro-Kuroiler crosses. In Horro-Koekoek crosses, the highest positive contribution of maternal effect was observed for body weight at eight weeks (8.22 %). Estimates of heterosis effects (He) were positive and ranged from 6.54 to 13.79%. In the Horro-Kuroiler crosses, estimates of maternal additive (Me) and the heterosis effects on body weight were positive and significant (P < 0.05) at 8- and 12-weeks of age. Generally, the positive and significant additive effects suggest merits of the sire line in the growth performance which favors use of Kuroiler and Koekoek as sire lines to improve the body. Positive values and significant contribution of heterosis indicate the substantial effect of CROSSBREEDING on body weight at most of the studied ages. From this study it can be recommended that crossbred hens sired by improved Horro (H × Ku) can be used for growth performance potential in the forthcoming synthetic breed development program.

CROSSBREEDING in sheep is strategically used to improve production and reproduction, especially when pastures have low quality. The objective of this study was to compare growth performance, birth and weaning body weights, and survivability between purebred Balouchi (n=53) and crossbred Balouchi × Romanov (n=114) lambs. In addition, carcass characteristics (n=24) were determined. Balouchi ewes were inseminated with Romanov semen to produce crossbred lambs. All experimental lambs were weaned at 77 d of age and slaughtered at 10 months of age. Birth body weight of the purebred Balouchi lambs was significantly greater than that of the crossbred lambs (3. 75 vs. 3. 56 kg, P<0. 01). However, weaning body weight (16. 6 vs. 12. 4 kg) and average daily gain from birth until weaning (152. 2 vs. 126. 0 g/d) and slaughter (125 vs. 95 g/d) were greater (P<0. 05) for the crossbred lambs than for the purebred lambs. Slaughter body weight at 10-month age (36. 9 vs. 36. 1 kg) tended to be greater (P=0. 08) for the crossbred lambs. Litter size was also increased by CROSSBREEDING (1. 13 vs. 1. 00), but lamb survivability was not different between the two groups. The fat-tail-free carcass yield tended to increase with CROSSBREEDING. CROSSBREEDING increased (P<0. 05) the weights of testis (0. 24 vs. 0. 16 kg), liver (0. 61 vs. 0. 52 kg), heart (0. 15 vs. 0. 12, kg), and lung (0. 47 vs. 0. 40 kg), while it decreased the weights of skin (3. 16 vs. 3. 72 kg), fat-tail (0. 30 vs. 1. 29 kg), and total internal fats (1. 08 vs. 2. 06 kg). It is concluded that CROSSBREEDING Balouchi ewes with Romanov’, s semen resulted in improved litter size, weaning and slaughter body weights, average daily gains from birth until weaning and slaughter, and carcass characteristics without affecting lamb survivability. Therefore, CROSSBREEDING can be a profitable strategy to increase lamb (meat) production in Balouchi sheep.