Under the animal model genetic variance is estimated in the base population taking into account inbreeding and is otherwise assumed to remain unchanged over generations. In practice, phenotypic variation differs randomly or systematically over time. Intuitively, such changes would be attributed mostly to environmental effects, and so lower heritability would be expected when variation is inflated. Studies in dairy cattle show contradictory results (e.g. Boldman and Freeman, 1990). Laying hens are kept under environmental conditions intended to be constant, but show substantial heterogeneity in phenotypic variance (VP) over generations. The aim was to investigate how variance components change.

Consumption of poultry meat is associated with human Salmonella infections (Revolledo etal. 2006). One way to control the presence of these bacteria in broiler flocks is to make chickens less susceptible to colonisation. Fermented liquid feed may be a potential tool to reduce the Salmonella carriage in broiler chickens (Heres etal. 2003). Fermented liquid feed is a moistened feed with high numbers of lactobacilli (=109cfu/gr), high concentration of lactic acid (= 150mM) and a low pH (<4.5) (Brooks etal. 2003). In the present experiment, a strain identified as Lb. salivarius that has been isolated from chicken gut and has been selected for its probiotic and fermentation properties after a screening method, was assessed for its efficacy in reducing the shedding of Salmonellatyphimurium in poultry.

Enriching chicken meat with long chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) is a viable means of increasing population intakes (minimum recommended 450 mg/d, SACN, 2004) of these essential fatty acids. Feeding broilers fish oil to achieve this causes problems with taint in the meat, whereas feeding an oil rich in C18:3 n-3 (LNA) does not result in the deposition of LC n-3 PUFA (Rymer and Givens, 2006). Stearidonic acid (C18:4n-3) is further down the conversion pathway of LNA to LC n-3 PUFA and appears to be converted much more efficiently by humans to LC n-3 PUFA than LNA (James et al., 2003). Feeding birds an oil rich in C18:4n-3 may therefore result in more enrichment of poultry meat with n-3 PUFA other than LNA, without the taint associated with feeding fish oil. The objective of this experiment was to determine what the effects on meat fatty acid composition and sensory characteristics were when broilers were fed an oil (SDA) derived from soyabean genetically modified to produce high concentrations of C18:4 n-3.

Indigenous poultry breeds are of a major importance to supply the rural population with eggs and meat in many developing countries of the world (Esmaelkhanian et al., 2004). A successful animal breeding plan is a continuous process of elimination and searching in a way that breeder could be able to manipulate genetic variation for changing a population to optimise desired phenotypes (Williams et al., 2002). As highlighted by Chambers (1990) animal’s body weight, which could be easily measured, is probably the most frequently used indicator of growth at a specific age. In practical animal breeding programmes, the breeding objective is usually genetic improvement of production and reproduction traits for a population under consideration. Knowledge of genetic parameters is of crucial importance to be implemented for predicting breeding value of candidate animals. The main objective of this study was to estimate heritability of body weight at week 8 for Iranian indigenous chickens through Bayesian statistical approach using an animal model.

Single injection of chronic dose of P4 in laying hens during the preovulatory open period has been shown to have positive effects on inducing a preovulatory LH surge and ovulation (Johnson et al., 1985). However, chronic injection of P4 has been shown to increase baseline concentrations of P4 and result in arrested laying and disrupted distribution of hierarchical follicles in turkeys (Bacon and Liu, 2004). The current study was designed to examine the effects of a simulated progesterone surge (by injection of chronic dose of P4) on broiler breeder hens performance, ovary morphology, plasma metabolites and hormones concentrations in either feed-satiated or feed-restricted hens.

The prophylactic use of antibiotic (as growth promoters) in animal feeds has made intensive farming possible and improved feed conversion. In the presence of low levels of an antibiotic, resistant cells survive and grow which produces an antibiotic-resistant population. Consequently, the use of antibiotic for broilers has been limited. Therefore, a number of studies on alternative products that can aid promotion of growth, improved feed utilization, and maintenance of gut health have taken placed (Hernandez et al, 2004). Herbs and organic acid have received an increased attention as an alternative to antibiotics (Craig, 1999; Ricke, 2003). The main aim of the present research was to evaluate the efficiency of alternative antibiotic growth promoters on Ross broiler performance.

Vitamin E (VE) is known for its role as an antioxidant, protecting unsaturated bonds of cellular membrane phospholipids against free radical attack. VE also has been shown to be a requirement for normal development and function of the immune system. Although poultry are renal synthesizers of ascorbic acid, synthesis is inadequate under stressful conditions such as high environmental temperature, high humidity, high egg and meat production rate and parasite infestation. The main objective of this study was to assess the effects of various levels of dietary VE supplementation and Vitamin C (VC) in drinking water on performance, humoral and cell mediate immune response.

Bifidobacterium spp. and Lactobacillus spp genera are useful and important microbiota which affect poultry performance. These bacteria are natural inhabitants of the intestine of broilers. These bacteria have a unique hexose metabolism that occurs via the phosphoketolase pathway. Bifidobacterium spp. produces the vitamins B1, B2, B6, B12, nicotinic acid and folic acid. Enzymatic hydrolysis by Bifidobacterium spp. increases bioaccessibility of lipids and proteins. Lactobacillus spp. exhibit properties which include the ability to adhere to cells, persist and multiply and produce acids, hydrogen peroxide and bacteriocidal and bacteriostatic agents. The ability of Lactobacillus to inhibit bacterial pathogens including E. coli and Salmonella species and to influence parasitic infection including Cryptosporidium parvum, Eimeria acervulina, and Giardia intestinalis (Seidavi et al. 2008). The aim of this study was to develop a method for the direct and simultaneous detection of Bifidobacterium spp. and Lactobacillus spp.in the intestine by multiplex PCR.

Salmonellosis is an infectious disease caused by Salmonella spp. that continues to plague human populations in both developed and third-world countries (Bohórquez, 2007). Conventional culture-based methods of detection that rely on enrichment of the sample and plating onto selective agar media may not be as sensitive as immunologic-or genetic-based rapid methods (Feng, 2001). PCR-based methods offer the advantages of high specificity and sensitivity. Some efforts have been made to reduce the time required and to increase the sensitivity and the accuracy of the methods to quantification of Salmonella in poultry samples (Mandrell and Wachtel 1999). This study was conducted in order to determine the relative population of Salmonella spp. in the duodenum, jejunum, ileum and caecum of chickens at different ages using densitometry.

Escherichia coli is a commensal bacterium of the gut microflora of the chicken. Escherichia coli infections are responsible for significant economic losses in the poultry industry world-wide. The pathogenesis and the role of virulence factors are not yet fully elucidated, although considerable progress has been made in recent years to establish the mechanisms of pathogenesis. Escherichia coli strains cause a number of diseases in domestic poultry, ultimately leading to disease and death, or to a decrease in egg and meat production or condemning of carcasses. On the other hand, our knowledge about the composition of the gut flora and microbial ecology of the gastrointestinal tract is still limited. Previous investigations have mainly used culture-dependent approaches. Studies on the composition of the intestinal flora of chickens date back to 1901 (Rahner, 1901) and were continued in the 1940s (Shapiro and Sarles, 1949), but comprehensive surveys that attempted to culture as many of the intestinal bacteria as possible were not carried out until the 1970s (Barnes et al. 1972; Salanitro et al. 1974). Such studies are technically difficult since strict anaerobic conditions have to be maintained during isolation and biochemical differentiation of the bacteria. It is well recognized that many bacteria have not been cultured yet in the laboratory because their growth requirements are still unknown. Recent molecular studies have yielded more detailed insight into the composition of the microbial community of this ecosystem (Zhu et al. 2002). The objective of this study was to develop a PCR based method for rapid quantification of Escherichia coli and investigation on its relative frequency in duodenum, jejunum, ileum and cecum of broilers.

In recent years there has been increasing interest in cultivating canola in tropical areas. This product is used to supply edible oil for humans, and also as a high quality protein source for poultry (Baker and Chang 1992), soybean meal has been replaced by canola meal and there were some negative and positive effects on egg production, egg quality, egg shell quality (Roth-maier1999) In the present study, investigating the effect of canola meal on egg quality, different levels of soybean meal were replaced by canola meal in laying hen diets.

Several methods have been introduced to estimate the optimum level of dietary nutrients such as metabolisable energy (ME), crude protein (CP), and lysine (Lys) in broiler chicken production. Performance optimisation is usually measured as maximising body weight gain and minimising adjusted feed conversion ratio (Adj FCR). One useful method is to model a system that requires an explicit mathematical input-output relationship. Group method of data handling-type neural network (GMDH-type NN) and genetic algorithm (GA) is used to model and optimise an output in an imprecise environment (Yao, 1999). The purpose of this study was to apply the GMDH-type NN and GA methods to provide an optimised formula for broiler chicken performance based on the dietary level of ME, CP, and Lys.

Palm oil is the most abundant of all oils produced globally. It is very high in saturated fatty acids specifically palmitic acid, but other fatty acids (monounsaturated (MUFA) and polyunsaturated) are presented at low concentrations. In the processing plant some high amount of oleic acid with some other unsaturated fatty acids are extracted and marketed as Palm olein oil, and used to reduce blood or egg cholesterol (Rievelles et al., 1994). The objective of this study was to determine the optimum level of dietary palm olein oil required to enrich the mono-unsaturated fatty acid content of yolk, egg cholesterol and antibody titre.

Mating of related individuals produces an inbred progeny, with an inbreeding coefficient that is one-half the additive relationship between its parents. One of the consequences of inbreeding is reduction of the mean phenotypic value or inbreeding depression, particularly for reproductive and fitness characters. Another consequence of inbreeding is reduction in additive genetic variance within lines or increasing homozygosity and higher risk for the incidence of lethal or deleterious recessive alleles. In recent years many studies show that inbreeding reduces reproduction and fitness capacity, for example Inbreeding depression in reproductive and productive traits has been reported by Flock et al (1993), Smith et al (1998), Klemetsdal (1998), Thompson et al (2000a,b) and Nwagu et al (2007).

The purpose of this study was to investigation recent trends in inbreeding in Iranian Native Fowls and relationship between increase in inbreeding and decreases in economic traits including body weight, age at first egg, egg production and egg weight.

The mulberry belongs to the genus Morus of the family Moraceae. There are 24 species of Morus and one subspecies, with at least 100 known varieties. One of the most important points about mulberry fruit is its sensitivity to environmental conditions during harvesting time and also the methods of harvesting. Because of these sensitivities, there is a lot of waste in the production of mulberry fruit. In the animal feed industry, agricultural by-products are used in animal and poultry nutrition. However, there is no information about the use of mulberry fruit waste in poultry nutrition; therefore this experiment was carried out to investigate the effect of mulberry fruit in broiler nutrition.

Sunflower (Helianthus annuusL.) is one of the most widely cultivated oilseeds in the world and ranks third in importance as a source of vegetable oil. As an alternative to fats and oils, full-fat oilseeds such as soybean seed are used to replace the supplemented fats and oils in broiler diets. However, soybean seed has anti-nutritional factors such as trypsin inhibitors, which need further processing, thus increasing the cost of soybean seed. Among the various oilseeds available on the market, full-fat sunflower seed (FFSS) contains more ether extract (EE) and is available at a relatively low price. This experiment was conducted to study the effect of FFSS (that FFSS had 18% CP, 38% EE, 14.3% CF, and 3868 kcal/kg ME) on performance of broiler chickens.

Sunflower (Helianthus annuus L.) is one of the most widely cultivated oilseeds in the world and ranks third in importance as a source of vegetable oil. In our experiment, full-fat sunflower seed (FFSS) had 180 g/kg CP, 380 g/kg EE, and 143 g/kg CF. Among the various oilseeds available on the market, FFSS contains more ether extract (EE) and is available at a relatively low price. This high EE content contributes to a high ME per unit or high energy density of feed. The increased production and availability of hybrid FFSS coupled with its oil content make FFSS a potentially desirable ingredient in poultry feeds. In the last few years, unextracted whole seed has been used as a feed ingredient in poultry diets. This experiment was conducted to determine the apparent metabolizable energy (AMEn) of FFSS in broiler chickens.

Cereal grains, such as wheat, have been regarded as one of the most affordable ingredients to supply dietary energy for fast growing broilers. However, broilers compete with humans for wheat to satisfy their nutritional needs and also they cannot effectively utilise wheat due to the limited ability of their gut enzymes to utilise dietary fibre. The efficiency of wheat utilisation can be increased by adding exogenous enzymes into cereal based diets for these birds (Annison and Choct, 1993). These enzymes can also reduce fermentation in the small intestine and so help maintain the gut health. Therefore, we compared the effect of adding a commercial fibrolytic enzyme to wheat and barley-based diets on the utilisation of either diet by broilers from 0 to 35 days of age.

The use of supplementary fat in commercial poultry diets has been wide-spread since the 1960s. In addition to their value as a dense source of energy, supplemental fats are an excellent source of essential fatty acids and enhance the absorption of fat soluble vitamins. The efficiency of nutrient digestion in poultry largely depends on the microorganisms which live naturally in its digestive tract (Apajalahti et al. 2003). It has been reported that intestinal microflora influences the absorption of fats (Pesti, 2002).Today, antibiotics and probiotics are used for manipulating the gut microflora in poultry production and act as growth-promoting agents. Thus, using these growth promoters (GP) will probably affect nutrients absorption, especially of dietary fats. The aim of this study was to evaluate the effects of supplementary antibiotics and probiotics in diets containing different levels of fat on broiler performance.

Antibiotics have been used for 50 years to enhance growth performance and to prevent disease in poultry production. Recently, most of the antibacterial growth promoters have been banned because the feeding of antibiotics is risky due not only cross-resistance but also to multiple resistances. Plants (especially herbs) have been used as food and medicinal purposes and some of them have played a significant role in maintaining human health and improving the quality of human life for thousands of years. Herbs or products containing plant extracts, essential oils or main components of the essential oil are among the alternative growth promoters that are already being used in practice. (Acamovic and Brooker, 2005; Ocak et al., 2008). There is evidence suggesting that herbs, spices, and various plant extracts have appetizing, digestion-stimulating and antimicrobial properties. But, there is only limited evidence about whether the inclusion as a solid herb material would have the growth promoting effects in live birds. The aim of this study was to evaluate the antibacterial effects of dietary dry peppermint (Mentha piperita L.), Cumin (Cuminum L.), Milfoil (Achellia millefolium L.) and poley (Teucrium Polium L.) on the performance of broiler.