فصلنامه تحقیقات تولیدات دامی
سال دوازدهم شماره 1 (بهار 1402)

Since the last two months of pregnancy (late pregnancy) constitute 75% of fetal growth, enriching the mother's diet can have positive consequences on the health and overall performance of the mother and children. Manganese functions in the immune system in different ways, including its activity in antioxidant pathways, its role in phagocytic activity, and maintaining the structural integrity of epithelial barriers against infection. Manganese deficiency can lead to dysfunction of innate and acquired immune systems in different species. Manganese toxicity is rarely observed. However, the main toxic effects attributable to this element are cardiotoxicity, hepatotoxicity, as well as deposition in specific components of the basal ganglia, and alteration of dopaminergic neuroenzyme activity. Diet enrichment with organic manganese increased feed consumption and improved dry matter digestibility in lambs. It has been documented that maternal manganese status is vital for ewe’s performance and the health of their newborn lambs. But, the required level and form of dietary manganese in ruminants are not well defined. Therefore, this study aimed to assess the influence of organic manganese supplementation on the performance, digestibility, milk yield and composition of Afshari ewes in the transition period, and the health of their lambs, For the present study, 24 single pregnant ewes were selected. They were kept in separate boxes (1 × 1 m2) with a concrete floor covered with straw during the experiment. Twenty-four lambs were born in three days from the experimental ewes. Forty-two days before lambing, the ewes were fed a diet rich in organic manganese. Water was also provided freely and separately. The experimental treatments included: 1. The first group (T1) was fed with the basal diet, 2. The second group (T2) was fed the basic diet enriched with 40 mg of organic manganese per kg DM (recommended by NRC), and 3. The third group (T3) received a basal diet enriched with 80 mg of organic manganese per kg DM (twice recommended by NRC). In this study, organic manganese (amino-manganese) contains an element of manganese and methionine, which are ionically connected. The diets of ewes were balanced using the NRC software. To calculate the weight change of the ewes, they were weighed five weeks before lambing, on the day of lambing, and five weeks after lambing. Also, the lambs were weighed on the day of birth and at the time of placental discharge. Feces and feed samples were collected in the last week for five days to test the digestibility of dry matter of ewes. They were determined in neutral detergent (NDF) by the Van Suest method, and crude protein and crude ash were measured according to the official Association of Analytical Chemists (AOAC) methods. The concentrations of fat, protein, lactose, and milk solids were measured by the Milkoscan device (MilcoscanTMS50-76510). A flame atomic absorption spectrometer model (Shimadzu-AA-670) with a wavelength of 279.5 nm was used to measure the magnesium concentration of milk. The feces of the lambs were evaluated daily. Stool scores were determined based on 1. Hard and consistent, 2. Soft and loose, 3. Loose and watery, 4. Watery with some blood, and 5. Watery with blood and mucus. At the end of the experiment, the weight and average feed consumption of ewes after delivery were influenced by organic manganese supplementation and showed a significant increase (P<0.05). While before delivery, there was no significant difference between the experimental treatments regarding the weight of the ewes (P>0.05). Also, the birth weight of the lambs and the time of placental discharge were not affected by the experimental treatments (P>0.05). The addition of different levels of organic manganese in the diet of ewes did not have a significant effect on digestibility parameters (dry matter, organic matter, crude protein, NDF, ADF, and ether extract) during the transition period (P>0.05). Supplementation of organic manganese in the diet of pregnant ewes during the transition period did not affect milk production (P>0.05). However, the amount of fat and solids in milk increased in the treatments with organic manganese supplementation, and this amount was higher in the animals that received 40 mg of organic manganese per kg DM (P>0.05). Also, the concentration of manganese in milk increased in animals that received organic manganese. In the present study, stool consistency improved under the effect of organic manganese supplementation. The number of lambs suffering from diarrhea and the average number of days suffering from diarrhea decreased significantly (P<0.05) due to the consumption of organic manganese supplements by the mother during the transfer period. Manganese is a nutrient associated with health and immunity. On the other hand, there is a close relationship between the antioxidant status of the body and the health of the animal because manganese plays a role in the structure of antioxidant enzymes such as superoxide dismutase (SOD). According to the results of this study, organic manganese acts as a valuable and safe supplement that can be used to improve the ewe’s performance and the health of newborn lambs.

 Lysophospholipids play an important role in animal nutrition. These substances, which are also classified as plant secondary metabolites, have a positive effect on the digestion and absorption of lipid nutrients in livestock. Lysophospholipids, mostly due to their emulsifying properties, increase the digestibility of fats and fat-soluble vitamins and can selectively prevent the growth of gram-positive bacteria. They can also emulsify dietary fats and increase fat absorption in the intestinal epithelium. The lysophospholipids can improve the consumption of fatty acid supplements and increase their digestibility. Therefore, they have substantial benefits for ruminants. The current study was conducted to evaluate the effects of consumption of different levels of lysophospholipids on degradability parameters, ruminal parameters, carcass fatty acid profile, microbial population, and protozoa in fattening male lambs.

 In this study, 24 crossbred male lambs with four treatments and six replications per treatment were used in a completely randomized design. The experimental diets included: 1. Basal diet (control) (without lysophospholipid in the diet and with a diet containing a lipid source), 2. Treatment containing a lipid source + 0.25% lysophospholipid in the diet, 3. Treatment containing a lipid source + 0.50% lysophospholipid in the diet, and 4. Treatment containing a lipid source + 0.75% lysophospholipid in the diet. The lipid source and lysophospholipid supplement were rumen-protected products. The total fattening period was 105 days (15 days of adaptation + 90 days of recording period).

 The results showed that adding 0.75% of lysophospholipid supplement increased feed consumption and daily weight gain and decreased FCR (P<0.05). With the addition of lysophospholipid supplement to the diet of fattening lambs, there was no significant difference between experimental diets with the control diet regarding the rapidly degraded fraction and slowly degraded fraction and total potential of degradability of dry matter, protein, and NDF (P>0.05). Experimental treatments had no significant effect on pH and ammonia nitrogen. The addition of 0.75% of the lysophospholipid supplement, compared to other treatments, increased the concentration of acetic acid and the ratio of acetate to propionate in the ruminal fluid and also increased linolenic acid (c18:3 ω3) (P <0.05) and the ratio of ω6/ω3 decreased in all experimental groups (P<0.05). The use of 0.5 and 0.75% lysophospholipid supplements in the diet increased the total ruminal bacterial population (P <0.05) but did not affect the population of protozoa (P<0.05).

 Based on the results of this experiment, it is possible to use lysophospholipid supplements at the levels of 0.5 and 0.75% of diets containing fat supplements in fattening male lambs.

Heat stress can compromise sheep's productive performance and growing lambs are considered to be one of the most susceptible groups to heat stress. Exposure to heat stress increases inflammatory cytokines secretion and impairs insulin signaling in muscle which may underlie poor growth responses. Therefore, enhancing insulin sensitivity through the addition of insulin-sensitizing dietary additives may improve animal performance during heat stress. Phytogenics, compounds with antioxidant, antimicrobial, and metabolic enhancing effects, have been used in animal nutrition to enhance performance and prevent diseases in stress-related conditions. It has been reported that supplementing a phytogenic-rich herbal mixture containing clove, rosemary, cinnamon, and turmeric improved the antioxidant status and enhanced insulin sensitivity of transition dairy cows. It has been indicated that the duodenal infusion of quercetin increased insulin secretion and insulin sensitivity. Possible mechanisms responsible for the insulin-sensitizing activity of herbal plants include increasing insulin receptors or enhancing receptor sensitivity to insulin, increasing PPARy activity, increasing glycogen synthase activity, modulating inflammatory cytokine expression, stimulating fatty acid oxidation as well as increasing antioxidant status. The objective of this study was to investigate the effects of a phytogenic-rich herbal mixture (PRHM) supplementation on gene expression of insulin-related genes in the muscle of feedlot lambs experiencing severe heat stress conditions.
Eighteen 11-12-month-old growing male Afshari×Chaal lambs (41.2 ± 3.04 kg) were housed in individual stalls (1.2 × 1 m, with individual feed troughs) on wooden slatted flooring, located within an indoor animal facility with a natural and artificial lighting system for 16 h/d. Lambs were randomly allocated to one of three experimental diets for a 48-day feeding period. The treatments included control diet without PRHM (0%PRHM), diet supplemented with 1% PRHM (1%PRHM), and diet supplemented with 2% PRHM (2%PRHM). The PRHM was added to the basal diet and mixed thoroughly. Diets formulated to meet nutritional requirements for maintenance and growth and offered twice daily at 0700 and 1700 h. The lambs had free access to feed and water during the experiment. The main ingredients of the basal diet were alfalfa hay, ground corn, wheat bran, beet pulp, soybean meal, and soy oil. The herbal mixture consisted of 50% rosemary leaves (Rosemarinus offıcinalis), 20% cinnamon barks (Cinnamomum zeylanicum), 20% turmeric roots (Curcuma longa), and 10% clove buds (Eugenia caryophyllata Thunb.). The total phenolic content of the PRHM was 89.6 g tannic acid equivalent per kg. The daily climate data, such as daily mean temperature and relative humidity, were recorded using a digital thermo-hygrometer (Testo 608-H1, Germany). At the end of the study, all lambs were transported to a local abattoir where they were slaughtered after 12-h feed withdrawal according to Halal method. Post-slaughter, longissimus lumborum muscle samples between the 12th and the 13th rib of the right side of carcass were collected as quickly as possible (i.e., within 3–5 min). For expression analysis of Insulin receptor (INSR), Insulin receptor substrate 1 (IRS1), glucose transporter 1 (GLUT1), glucose transporter 4 (GLUT4), Peroxisome Proliferator-Activated Receptor Gamma (PPARγ) genes, total RNA was isolated from the sheep muscle tissue using the SinaPure RNA according to the manufacturer’s instructions. The quantity and integrity of isolated RNA were determined for each sample by using both NanoDrop (260/280 ratio) and 1% agarose gel electrophoresis. cDNA was synthesized with RevertAid First Strand cDNA Synthesis Kit according to the manufacturer’s instructions. Forward and reverse primers were designed for five genes and GAPDH as reference gene by Oligo 7. The real-time PCR was done in 25 µL containing 1x BIORON GreenHot Master Mix (BIORON, Germany), 1 µL cDNA, 0.3 µM of each forward and reverse primers and nuclease-free water to reach final volume. Real-time PCR was performed on Bio-Rad CFX96 as follows; Initial denaturation 2 min at 94 °C, followed by 39 cycles of denaturation 20 sec at 94 °C, annealing 25 sec at annealing temperature, extension 20 sec at 72 °C following by melting curve analysis from 65 °C to 95 °C with 0.5 °C increase per each step. Relative gene expression was determined based on Livak method (2-ΔΔCT). All data were analyzed using the MIXED procedure of SAS. Model included the effect of the treatment as the fixed effect and lambs within treatments as a random effect. The significance level was declared at P<0.05.
The results showed that the gene expressions of INSR (P<0.01) and GLUT4 (P<0.01) in muscle tissue were linearly upregulated in lambs supplemented with increasing levels of herbal mixture. A quadratic effect of herbal mixture supplementation was found on gene expression of IRS1 such that lambs fed a 2% mixture had the highest gene expression. Moreover, both supplementation levels of 1 and 2% mixture equally increased GLUT1 gene expression (P<0.01) compared to control lambs. In contrast to the other genes, PPARγ gene expression was quadratically (P<0.01) downregulated by mixture supplementation such that the lowest gene expression was observed in lambs receiving a 2% mixture. Although there is some evidence suggesting that PRHM supplementation has modulatory effects on insulin resistance in transition dairy cows, to our knowledge, there is currently no published data investigating the effects of PRHM supplementation on mRNA expression of genes related to insulin and glucose metabolism in lambs’ skeletal muscle. Our results may suggest that PRHM supplementation enhanced insulin sensitivity and glucose uptake in the skeletal muscle of heat-stressed lambs. In agreement with our results, it has been found that cinnamaldehyde promotes gene expression of IRS-1 and GLUT4 genes in muscle cells, which the latter gene is affected by activating the peroxisome proliferator-activated receptor gamma coactivator 1-alpha. In addition, greater GLUT1 gene expression might be indicative of improved insulin-independent glucose uptake, besides enhanced insulin-dependent glucose transporter, GLUT4 gene.
The results showed that the mixture of medicinal plants including cinnamon, turmeric, rosemary, and clove affected the expression of genes related to insulin metabolism and increased the efficiency of glucose utilization.

Goat milk production is very important in Iran. Artificially extending day length affected milk production in several domesticated species. In the dairy cow industry, the use of photoperiod management is usual because it is a safe, non-expensive, and effective method to increase milk production. Dairy cows with late gestation exposed to short days produce more milk than cows exposed to long days. But, long-day photoperiod during early lactation increases daily milk yield. In contrast to cows, small ruminants such as goats have seasonal reproductive cycles and therefore their response to photoperiod may differ. To date, no study was conducted to evaluate the magnitude of the response of native goats of Iran to photoperiod. Therefore, the objective of this study was to compare the magnitude of the effect of artificially shortening and extending day length on milk yield in black native goats of Chaharmahal and Bakhtiari province in Iran.
Six weeks before the start of giving birth in the flock, 80 does whose parturition dates were close to each other were selected from a local black goat flock and each one was randomly assigned to one of the following four treatments (n=20 for each treatment). Treatment 1: Does exposed to natural day length during pregnancy and lactation (control); Treatment 2: Does exposed to natural day during the pregnancy period and exposed to long day length at the beginning of the lactation period; Treatment 3: Does exposed to short day length at the end of the pregnancy period and exposed to natural day length during the lactation period; Treatment 4: Does exposed to short day length at the end of the pregnancy period and exposed to long days at the beginning of the lactation period. Milk production and levels of prolactin, melatonin, and IGF-1 hormones were measured. The does were milked manually once a week at 07:00 starting one week after parturition. Before milking the does, their kids were separated for 12 hours. Blood samples (five mL) were collected at the start of the experiment, 20 days before parturition, parturition, 15 and 30 days after parturition from each doe via jugular venipuncture into a sterile evacuated tube and immediately placed on ice. Plasma was harvested by centrifugation at 2000 rpm for 20 min and stored at -20 °C until use.
In treatments 2, 3, and 4, the amount of milk obtained in each milking time increased until the third week of the lactation period, and then its increasing process slowed down. In the control treatment, the amount of milk obtained in each milking time increased until the third week, but the amount of milk obtained in the fourth week was less than that in the third week, although this difference was not statistically significant. The average milk obtained in four milking times for treatments 1, 2, 3, and 4 was equal to 868.5, 959.25, 1005, and 1085 mL, respectively. Over the monitored lactation period, the averages of milk yield in the second, third, and fourth treatments were 10%, 15%, and 24% more than that in treatment 1 (control). According to the results of this research, it was reported that milk production in goats that were placed in short-day length conditions in the last third of their pregnancy period was 26% higher than in goats that were in long-day length conditions at the same time. In another study, a 20% increase in milk production was reported in Saanen goats that were exposed to a long light period after giving birth. The amount of prolactin hormone in treatments 1 and 2 in 20 days before delivery was higher than in treatments 3 and 4 (P<0.05), but no significant difference was observed between treatments 1 and 2 as well as between treatments 3 and 4. At the time of parturition, the amount of prolactin hormone in all treatments was similar. At 15 and 30 days after delivery, the amount of prolactin hormone was higher in treatments 2 and 4 than in treatments 1 and 3 (P<0.01). Before giving birth, the amount of melatonin in female goats of treatments 3 and 4 was higher than in treatments 1 and 2 (P<0.01). Fifteen days after birth, the amount of melatonin hormone in female goats of treatment 2 was lower than that of female goats of treatment 1 (control treatment) (P<0.05), and the difference between other treatments was not significant. The amount of melatonin in different treatments was similar 30 days after birth. In the 20 days before parturition, the difference between the female goats of treatments 3 and 4 with those treated with natural day length (treatments 1 and 2) was significant (P<0.01) in terms of IGF-1 hormone levels. At 30 days after birth, the difference between female goats of treatment 4 and other treatments was significant in terms of the amount of IGF-1 hormone (P<0.05). According to the results of the present research, it has been reported that the long lighting period increases the concentration of prolactin and IGF-1 hormones. Decreased secretion of melatonin hormone with the increasing length of photoperiod has been reported in cattle and other animals. Increasing the duration of the light period reduces the time when melatonin secretion is at its peak.
In general, the application of a short light period before parturition and a long light period after parturition increased the amount of milk produced by female goats.

Horse has been of great interest to humans due to its speed, strength, and endurance. Based on its role in human history and civilization, it is considered the most important domesticated animal. Iranian horse breeds are bred in the north, south, and west regions of the country. Arabian horse is one of the international breeds in the world, which is bred in more than 60 countries. Preliminary evidence shows that the Arabian horse breed was established about 3000 years ago and was bred in small populations in many countries of the Middle East, including Egypt, Iran, Saudi Arabia, and Syria. These separate populations have led to the development of different maternal strains of the Arabian horse. Genetic diversity is necessary for genetic conservation and survival of the breeds. Molecular markers are used to assess the structure and genetic diversity of different populations. Therefore, one of the suitable markers is a microsatellite. Regarding the importance of genetic diversity in the survival of the breed, and designing the genetic conservation and breeding programs, the purpose of this study was to investigate the population structure and genetic diversity of Arabian horse breeds using microsatellite markers.
In this study, hair root samples were obtained from 8673 (5602 mares and 3071 stallions) Arabian horses from Khuzestan, Yazd, Kerman, Isfahan, Lorestan, and Alborz provinces. DNA samples were extracted from hair roots using the Direct PCR Kit (Thermo Fisher Scientific, Vilnius, Lithuania). The quantity and quality of the extracted DNA were controlled by spectrophotometry and agarose gel methods. The number of 10 microsatellite markers including AHT04, AHT05, ASB02, ASB17, ASB23, HMS03, HMS06, HMS07, HTG10, and VHL20 were used based on ISAG recommendation. Then, the amplification of genomic fragments and the genotype of samples was determined by COrDIS Horse Reagent Kit (Moscow, Russia). Forward primers were labeled with fluorescent dye at 5'-end. These microsatellite loci were amplified by the multiplex PCR method. Then, the PCR products were genotyped by the Genetic Analyzer system and the capillary electrophoresis method. Obtained data were used to estimate demographic parameters. The number of effective alleles, the number of observed alleles, the observed heterozygosity, the expected heterozygosity, and the Shannon index were calculated by GenAlex 6.5 software. Genpop 4.7.5 software was used to calculate the FIS statistic or Fixation index in the population.
The results showed that the lowest and highest number of observed alleles were related to ASB17 (17 alleles), HMS06 (eight alleles), and HMS07 (eight alleles) markers, respectively. The total number of alleles observed at all loci was 113 alleles. The average number of observed alleles was estimated to be 11.3, which indicates high allelic diversity in the Persian Arabian horse. The mean number of effective alleles, Shannon index, observed and expected heterozygosity and Fixation index were 3.97, 1.58, 0.721, 0.736, and 0.021, respectively. The mean genetic diversity in the Arabian horse’s population was calculated to be 0.736. The highest and lowest genetic diversity was observed in VHL20 (0.803) and ASB02 (0.620) markers, respectively. The average number of effective alleles per locus in studies conducted in different countries on Arabian horses, including Egypt, Syria, and Western countries, with Persian Arabian horses in this research, showed that number of effective alleles is higher in Persian Arabian horses. The average Shannon's index has been reported to be slightly lower in previous studies of Persian Arabian horses, which is probably due to the small number of samples in these studies compared to the present study.  The highest and lowest observed heterozygosities in this study were related to AHT4 (0.788) and ASB02 (0.613) markers, which were consistent with the results of the research conducted on Arabian horses of Iran, Syria, and Egypt. The positive FIS value in Arabian horses made a decrease in heterozygosity in the population, an increase in homozygosity and consequently inbreeding in Arabian horse populations. In this research, all studied loci showed a significant deviation from the Hardy-Weinberg equilibrium. Except for the AHT04 marker, which deviated from the Hardy-Weinberg equilibrium at P<0.01, the others have deviated at P<0.001. Deviation from the Hardy-Weinberg equilibrium can indicate the presence of some factors disturbing Hardy-Weinberg equilibrium, such as migration and selection, which in Persian Arabian horses, the entry of stallions from outside the herd and the gene flow between different maternal strains and also the existence of a selection program among breeders are the main factors of deviation from Hari-Weinberg equilibrium.
Evaluation of the genetic structure of Arabian horses of Iran and comparison with other Arabian horses in the world, including those in the Middle East region, showed that Arabian horses of Iran have a higher genetic diversity, which is probably due to the presence of different maternal strains in Iran, high gene flow among the different strains, a large import of Arabian horses and crossbreeding with Arabian horses of Iran, as well as a high number of samples and so identification of new alleles in this research. On the other hand, the rate of inbreeding was positive according to the FIS in Iran Arabian horses, indicating a risk of genetic diversity loss and increasing inbreeding in these horses. Therefore, management of genetic diversity and prevention of mating among related animals should be considered.

Identifying genes with large effects on economically important traits, has been one of the important goals in sheep breeding. A method to identify new loci and confirm existing quantitative trait loci (QTL) is through genome-wide association studies (GWAS). QTL-assisted selection and genomic regions affecting the production traits have been considered to increase the efficiency of selection and improve production performance. GWAS typically focuses on genetic markers with the strongest evidence of association. However, single markers often explain only a small component of the genetic variance and hence offer a limited understanding of the trait under study. A solution to tackle the aforementioned problems, and deepen the understanding of the genetic background of complex traits, is to move up the analysis from the single nucleotide polymorphism (SNP) to the gene and gene-set levels. In a gene-set analysis, a group of related genes that harbor significant SNP previously identified in GWAS is tested for over-representation in a specific pathway. The present study aimed to conduct a GWAS based on gene-set enrichment analysis for identifying the loci associated with economic traits using the high-density SNPs.

In this research, to identify genes and biological pathways associated with some economic traits, GWAS based on gene-set enrichment analysis was conducted in a F2 population derived from a reciprocal cross by using Illumina iSelect 4K Japanese quail SNP Bead chip. For each bird, traits including body weight gain, feed intake, feed conversion ratio, tibia ash, and foot ash were measured. The SNPs that were associated with traits were identified based on mixed linear models using GCTA software and no correction was made to adjust the error rate. The gene-set analysis consisted of three different steps: (1) the assignment of SNPs to genes, (2) the assignment of genes to functional categories, and (3) the association analysis between each functional category and the phenotype of interest. In brief, for each trait, nominal P<0.005 from the GWAS analyses were used to identify significant SNPs. Using the biomaRt R package, the SNPs were assigned to genes if they were within the genomic sequence of the gene or a flanking region of 15 kb up- and downstream of the gene, to include SNP located in regulatory regions. For the assignment of the genes to functional categories, the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway databases were used. The GO database designates biological descriptors to genes based on attributes of their encoded products and it is further partitioned into three components: biological process, molecular function, and cellular component. The KEGG pathway database contains metabolic and regulatory pathways, representing the actual knowledge of molecular interactions and reaction networks. Finally, a Fisher’s exact test was performed to test for overrepresentation of the significant genes for each gene set. The gene enrichment analysis was performed with the goseq R package. In the next step, bioinformatics analysis was implemented to identify the biological pathways performed in BioMart, Panther, DAVID, and GeneCards databases.

Gene-set enrichment analysis has proven to be a great complement to GWAS. Among available gene set databases, GO is probably the most popular, whereas KEGG is a relatively new tool that is gaining ground in livestock genomics. We hypothesized that the use of gene-set information could improve prediction. It is likely that a better understanding of the biology underlying meat production specifically, plus an advance in the annotation of the quail genome, can provide new opportunities for predicting production using gene-set information. 11 SNPs on chromosomes 2, 3, 4, 5, 10, 18, 20, 24, and 27 located in NPY, DRD2, PTPRN2, BMPR1B, MYF5, IGF2BP1, MYO1E, FGF2, LDB2, BMP4, ACOX1, PCK1, PLCB4, PLCB, and PLCG1 genes were identified. According to gene-set enrichment analysis, 23 categories from gene ontology and the KEGG pathway were associated with the traits (P˂0.05). Among those categories, Protein glycosylation, Myoblast differentiation, Positive regulation of muscle cell differentiation and Biological MAPK signaling pathway, and Calcium signaling pathway have a significant association with skeletal muscle fiber, feed intake, and availability utilization.

This study supported previous results from GWAS and revealed additional regions associated with these economically important traits. Using the findings of this study could potentially be useful for genetic selection to improve production in Japanese quail.

Fat inclusion in the diet presents positive features such as essential fatty acids and vitamin supply, slowing the passage rate, and lubricating the feed milling equipment. The price of conventional added fat sources has been increasing in the last few years; therefore, there is a growing interest in the use of alternative energy sources in poultry feeding. In this context, coproducts derived from the soybean oil refinement process represent an economic alternative and permit giving added value to residual products. Soybean lecithin, which is extracted from the soybean oil degumming process, is mainly composed of polar lipids (>60%), especially of phospholipids, but also contains an important amount of neutral lipids (30–40%), as triacylglycerols and free fatty acids. Soy lecithin may also act as a source of polyunsaturated fatty acids, which are important precursors of eicosanoids for human health benefits and neonatal growth. The inclusion of lecithin in the diet could improve lipid digestibility, liver function, and performance. Therefore, the present study was designed to evaluate the effect of fat source and soybean lecithin on performance, egg quality, nutrient digestibility, and blood parameters in laying hens.
A total of 144 Nick Chick laying hens were randomly divided into six treatments, six replicates, and four hens per replicate as a 2×3 factorial experiment in a completely randomized design. The experimental treatments included: 1) 3% soybean oil, 2) 3% soybean oil + 0.1% lecithin, 3) 3% tallow, 4) 3% tallow + 0.1% lecithin, 5) a mixture of soybean oil + tallow in equal proportions, and  6) a mixture of soybean oil + tallow in equal proportions + 0.1% lecithin. Lecithin contains 7480 kcal/kg metabolizable energy and is added to experimental diets at one kg/ton as per company recommendation. Productive performance and egg quality traits were recorded from 37 to 44 weeks of age. Egg production and egg weight were recorded daily and feed intake was recorded weekly. This information was used to calculate the feed conversion ratio. Egg quality was measured in four eggs which were individually weighed and the external and internal quality (shape index, yolk index, yolk weight, yolk color, Haugh unit, shell weight, and shell thickness) was determined. At the end of the experiment (44 weeks of age) celite was added to experimental diets as an insoluble marker. Apparent metabolizable energy, dry matter, fat and crude protein digestibility were measured. Liver enzymes’ activity (aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, and lactate dehydrogenase concentrations) and blood parameters (triglyceride, cholesterol, HDL, and LDL) were measured at the end of the experiment.
Feed intake (P<0.01), egg production, and egg mass improved by a mixture of soybean oil + tallow (P<0.05) in the entire experiment. The effects of the source of oil on the productive performance of laying hens are contradictory and depend on the oil source and fatty acid compositions of oil/lipids, strain, and age of hens. Inclusion of lecithin in the diet increased feed intake and yolk color (P<0.01) but decreased Haugh unit (P<0.05). The reasons for the discrepancies among researchers concerning the effects of dietary lecithin on poultry production are not known but might depend on the type of bird used, as well as on the characteristics of the diet, including the level, source, and fatty acid profile of the lipid source used. The information available on the effects of lecithin on yolk pigmentation is scarce. The unsaturated fatty acid profile of lecithin is more favorable for xanthophyll absorption and utilization than that of the more saturated fatty acid profile of animal fat. Lecithin facilitates the absorption and transfer of fats, so it can cause the absorption of pigment substances as fat-soluble compounds. Yolk color increased and eggshell thickness was decreased (P<0.05) by a mixture of soybean oil + tallow. Apparent metabolizable energy, dry matter, fat, and protein digestibility were not affected by fat source, lecithin inclusion, or fat source × lecithin interaction. Moreover, the data indicated that the addition of soy oil decreased the cholesterol in the plasma (P<0.05). Aspartate aminotransferase (P<0.01), lactate dehydrogenase (P<0.05), triglyceride (P<0.01), cholesterol, and LDL (P<0.05) concentrations of the plasma decreased by lecithin inclusion in the diet. Lecithin is one of the natural elements that have dispersing properties. Lecithin is capable of reducing LDL cholesterol. It also promotes HDL cholesterol synthesis. In addition, it is used to help reduce cholesterol and triglycerides and protect the liver in the prevention of kidney stone formation. The lecithin modifies the cholesterol homeostasis in the liver, increasing the HMG-CoA reductase (3-hydroxy-3-methyl-glutaryl-coenzyme A reductase) and alpha 7 hydroxylase cholesterol activities. The LDL concentration and size are also significantly reduced and the bile acid pool and bile lipid secretion are increased.
In general, soybean lecithin can be added, in combination with soybean oil and tallow as an energy source in laying hens' diet to improve performance.