In order to investigate the rates of inbreeding trend and also the effect of inbreeding on milk, fat and protein yields, the pedigree data of 2,394,517 Iranian Holstein cattle from 1986 to 2019 which collected was used. CFC software was utilized to calculate the inbreeding coefficients, and WOMBAT program was applied to estimate the inbreeding depression by determining regression coefficient of production traits on inbreeding coefficient. The average of inbreeding coefficients in the whole population and inbred animals were estimated as 0.777 and 1.681 percent, respectively. In general, the rate of inbreeding trend was positive and for recent years it was 0.17 percent per year. However, this rate was estimated as -0.29 percent per year for inbred animals, the number of inbred animals was increasing. Examination of the effect of inbreeding on production traits showed that per 1 percent increase in inbreeding coefficient resulted in 11.87, 0.39 and 0.29 kg decrease in milk, fat and protein yields, respectively. The use of domestic sperms and cows has limited the population and increased relative mating. However, close relative mating has been controlled. The existence of negative effect of inbreeding on production traits and on the other hand, increasing the number of inbred animals indicates that breeding and mating strategies of animals need to be continuously reviewed, and if it is necessary close relative mating can be limited using imported sperms.

Osteopontin gene is located at the end of chromosome 6 in cattle and it is one of the most important genes influence on milk protein percentage and reproduction. In this study, blood samples were collected from100 Brown Swiss cows and DNA was extracted from whole blood by modified salting out procedure. Cows were genotyped for single nucleotide polymorphism of intron IV by PCR-RFLP and BsrI restriction enzyme method. Breeding values were individually predicted for milk production, fat and protein milk percent traits by restricted maximum likelihood method. Association between polymorphisms and breeding values were calculatedat a 5% significant level. Frequencies of TT, TC and CC genotypes were 0.32, 0.46 and 0.22, respectively. Studied population was inaccord with Hardy-Weinberg expectation. There was no significant association between genotypes and breeding values of milk production, fat or protein percent traits.

Acyl-CoA: diacylglycerol acyltransferase-1 (DGAT1) gene has been mapped at centromeric end of bovine chromosome 14 and is known as a factor affecting fat content of milk. Our objective was to determine the relationship between the K232A polymorphism at the gene and milk traits in Holstein cattle of Iran. A 411 bp fragment including this polymorphism was amplified and digested with the enzyme CfrI to determine the genotypes of 206 Holstein cows. The estimated allele frequencies were 0.66 and 0.34 for the A (alanine) and K (lysine) alleles, respectively. Average allele substitution effects of the K allele for all traits in the first and second lactations were estimated, separately. The statistical analyses showed positive and significant effects of the K allele for fat and protein content traits, as well as for the fat yield in both lactations. In contrast, negative and significant effects were found for milk and protein yield. The relatively lower frequency of the K allele than the A allele may be due to selection for milk yield in recent years. Our results showed that the DGAT1 K232A polymorphism can be a source that underlies the reported quantitative trait loci for fat content trait in the proximal region of bovine chromosome 14.

The aim of this study was to test the genotypes effect of DGAT1 gene on breeding value in Iranian Holstein milk production traits. For this purpose, 103 semen samples of registered bulls were collected and then gen-otyped for partial region of DGAT1 gene. The studied traits were milk yield (MY), fat yield (FY), protein yield (PY), fat percentage (FP) and protein percentage (PP). First lactation records of 43044 dairy cattle from 2000 to 2007 were used. The PCR-RFLP method was used for genotyping DGAT1 gene. The Hardy Weinberg equilibrium for allele and genotype frequencies was analyzed with Chi-square test using PoP-Gen software. Genetic parameters of studied traits were estimated by REML method under animal model with DFREML software. The breeding value of individual was predicted by BLUP method. Different geno-type effect of 97 of 103 proven bulls on breeding value of milk production traits were investigated by GLM procedure of SAS (9.1) software. The mean of breeding value of proven bulls with different genotype were compare with Duncan test. The observed genotype frequency results showed KK (0.592), KA (0.408) and AA (zero) and the allele frequency obtained was K (0.7961) and A (0.2039). The KK genotype was con-firmed by sequencing method and the K allele, with long of 411 bp, was registered in gene bank of NCBI with accession number EU077528. Estimated heritability of studied traits were 0.35 (0.02), 0.33 (0.02), 0.31 (0.017), 0.28 (0.02) and 0.27 (0.016) for MY, FY, PY, FP and PP, respectively. The average breeding values of MY, FY, PY, FP and PP were estimated as: 180.2 (28.8) kg, 3.7 (1.26) kg, 2.3 (1.06) kg, -0.036 (0.014) % and -0.03 (0.01) %, respectively. The average breeding value of MY for KA and KK genotypes were 288.8 and 109.6 kg, respectively and the difference was significant (P<0.01). The average breeding values of FY in bulls for KK and KA genotypes were 5.6 kg and 0.91 kg, respectively (P>0.05). The aver-age breeding values of PY for KA and KK genotypes were 0.025 and 5.5 kg, respectively (P<0.05). Differences between means of breeding values for FP and PP were significant (P<0.05), these values for genotype KK and KA were -0.009% and -0.067% for fat and -0.016% and -0.059% for protein, respectively.

A total of 125 Russian Red Pied cows were genotyped for the prolactim-related gene. The PRL-RsaI genotypes were analysed using the Polymerase chain reaction -restriction fragment length polymorphism (PCRRFLP) method. In this breed, the frequencies of alleles were as follows; A= 0.794 and B= 0.206. The frequencies of AA, AB and BB genotypes were 0.598, 0.392 and 0.01; respectively. Results showed that: BB genotype had higher milk yield than AA and AB individuals (P< 0.05). BB genotype showed higher milk fat yield than AA and AB individuals (P< 0.05). With respect to milk fat content (%), the AB genotype had higher levels than the AA and BB individuals (P< 0.05). No differences between the cows of different PRL-RsaI genotypes were found in terms of milk fat yield and milk protein concentration. The results showed that the highest milk and milk fat yields were obtained by cows with the genotype PRL-RsaI BB. The results presented here demonstrate that the prolactin gene may be considered as a marker for dairy traits in cattle.

To study milk production traits and estimate genetic related parameters, 3245 records of milk yield, fat yield and fat percentage of Khuzestan Holstein cows were used. The effects of the region, herd, parity, calving year, season and month of calving were evaluated on the traits. Also the effect of Herd-Year-Season (H-Y-S) was investigated on the traits in a mixed model including age of calving as a covariate. The effects of the region, herd and calving year were significant on all traits, but the effects of parity and calving season were not significant on fat percentage. The effect of H-Y-S was significant on all traits, too. The mean and standard deviation of milk yield, fat yield and fat percentage were 3851.57±1073.34 Kg, 136.08±43.51 Kg and 3.57±0.70 percent, respectively. Heritability of milk yield, fat yield and fat percentage were 0.24±0.10, 0.25±0.11 and 0.36±0.10 using univariate model and were 0.19±0.06, 0.30±0.08 and 0.31±0.05 using repeatable model Estimated. Repeatability was 0.32, 0.32 and 0.32 for milk yield, fat yield and fat percentage, respectively. The genetic, residual and phenotypic correlation were 0.70, 0.76 and 0.75 between milk yield - fat yield, -0.30, -0.32 and -0.31 between milk yield – fat percentage and 0.47,0.32 and 0.37 between fat yield - fat percentage. Lactation curves were studied for four calving seasons, using monthly records. The highest peak of milk production and the best persistency of lactation curve were found for winter calving cows and fall calving cows, respectively.

Identifying the constraining factors of production and yield gap is very important. Therefore; this research was performed to identify the production constraining factors of local rice cultivars. All management practices from nursery preparation to harvesting stages for 100 paddy fields of local rice cultivars were recorded through field studies, in Sari, from 2015-2016. In the CPA, the actual and calculated potential yield were 4495 and 5703 kg/ha, respectively and the gap was 1221 kg/ha. The yield gap caused by number of top-dressing variables was 324 kg/ha, equal to 27% of the total yield gap. The yield gap related to previous year of legumes cultivation was 218 kg ha-1, equal to 18% of the total yield variation. Among the 10 variables entered in the CPA model, the effects of top-dress fertilizer application and its application frequency and foliar application were remarkable, which could compensate a significant part of the yield gap (444 kg/ha, 37% of total) in the farmers’ fields by managing these variables. According to boundary line analysis (BLA) finding, actual yield mean on the basis of optimal limit related to 12 variables under study was 5369 kg/ha, with 881 kg/ha yield gap . Mean relative yield and relative yield gap for 12 variables (transplanting date, seedling age, number of seedlings per hill, planting density, nitrogen and phosphorous per hectare, nitrogen before transplanting, harvesting date, lodging problem, pest problem, diseases problem and weeds problem) were 83.64 and 16.35 kg/ha, respectively. Based on the finding, it can be stated that the model precision is appropriate and can be applied for both estimation of the quantity of yield gap and determining the portion of each restricting yield variables.

This study was conducted in a private sector buffalo farm in Al-Qurna, located north of Basra Governorate, between December 2023 and November 2024. It covered the summer (July and August 2024), autumn (October and November 2024), and winter (December 2023, January and February 2024) seasons. The purpose of the experiment was to examine the impact of the mid-lactation stage on genetic polymorphism in the growth hormone (GH) gene members (E4, E5, E6, E8) in the blood of buffaloes, and their relationship with serum GH levels during mid-lactation. Thirty blood samples were collected from the same buffaloes (n=30). Polymerase Chain Reaction (PCR) was used to amplify the targeted genes, and nucleotide sequence analysis was performed to detect polymorphisms. The results were compared with GH gene genotypes in the GenBank database. Two genotypes of the GH gene were identified in the mid-lactation buffaloes. DNA sequencing of the GH genes (E4, E5, E6, E8) was carried out, and the sequence data were compared with two references from the NCBI database. The E4 gene showed no differences when compared with Acc. NC_059175, but several mutations were observed compared with Acc. HG738860. The E5 gene sequence revealed polymorphisms when compared with both Acc. KC107765 and Acc. NC_059175 references. Although the E6 gene sequence showed no polymorphisms, the E8 gene sequence displayed a single-point mutation. Additionally, the results indicated significantly higher (P≤0.05) serum growth hormone levels in genotype A compared to genotype B.