نشریه اصلاح و به نژادی دام
سال دوم شماره 2 (پیاپی 4، تابستان 1401)

Using efficient mathematical methods can be effective in order to breed identification and genetic grouping. So, the aim of this study was to compare the morphological features of native camels of central desert of Iran with dairy camels of Pakistan using the principal component analysis method. For this purpose, 25 native camels of Iran and 62 dairy camels of Pakistan were used. Measurements of shoulder height, pin width, udder circumference and udder depth were considered. Principal component analysis (PCA) carried out using ggfortify package in R version 3.5.3. Also, scores of camel type were compared using the independent samples t-test in SPSS software (version 22). The results showed that Pakistan’s dairy camels was taller than native camels (p <0.05). Pin width, udder depth, and udder circumference in Pakistan’s camels were larger than native Iranian camels (p <0.05). The mean evaluation score of Iranian native camels was 57.12 ± 10.03 and in camels of Pakistani origin was 76.71 ± 12.31 (p <0.05). The results of PCA showed that native camels of the central desert of Iran and dairy camels of Pakistan are in two separate categories and have different morphologies. The results of the present study showed that it is possible to use mathematical methods including principal component analysis (PCA) in order to accurately distinguish Iranian native camels from dairy camels of Pakistan origin.

With due attention to increase of population and ahead that necessity of human to use of protein demand body, lead mankind pondered that breeding can provide demand protein of society. The purpose of this study was quantity of inbreeding and it’s changes at recent three decade among of Khuzestan’s buffalo population. The data were collected pedigree of 21,009 heads of buffaloes by the Centre for breeding and improve the country were used during the years 1981 to 2011. The results showed that the number of inbreeding animals at the pedigree was 1200 head. Average inbreeding coefficient of the population and inbred population was estimated 0.8 and 10.77%, respectively. Annual changes in inbreeding was 0.05 which was statistically significant (P <0.01). The negative effects of inbreeding on the quantity and quality of buffalo’s milk would prevent. Rapid rise in inbreeding should be prevented by appropriate management  and application of desired programs to avoid negative effects of inbreeding on quality and quantity of milk production.

The aim of the current project was study of population structure using pedigree analysis and also inbreeding depression of growth traits in Iran-Black sheep. Pedigree information related to 5481 animals and records of body weights at birth, weaning, six-month, nine-month and yearling, collected from 1982 to 2011 at Abbasabad Sheep Breeding Station in Mashhad, were used. Calculation of inbreeding coefficients was done by CFC, and Endog (v4.8) to compute other pedigree analyses, and WOMBAT software was used for estimating the inbreeding depression of growth traits. The total number of founders, the effective number of founders, the effective number of ancestors, the effective number of founder genomes, and the effective number of non-founder genomes, were 167, 22, 17, 11, 22 heads, respectively. The estimated average for coancestry, relationship and inbreeding coefficients was 4.71, 9.42 and 4.80 percent, respectively. The generation interval and the effective population size based on individual increase in inbreeding were 4.85 years and 26 heads, respectively. The average generation interval in the sire-progeny pathway was greater than the dam-progeny pathway. Also, half of the genetic diversity of the study population originated from 6 ancestors. The inbreeding depression for body weight traits at birth, weaning, six, nine and 12 months of age were 10.3, 130.6, 491.8, 525.5 and 414.7 g, respectively. The results showed a decrease in genetic diversity of the study population compared to the founder animals and observed inbreeding depression in the studied traits could also confirms it.

The aim of the present study was to estimate the impact of somatic cell count on daily milk yield of Iranian dairy cows using quantile regression statistical technique. A total of 784,532 test day records belonging to 93,259 first-parity cows distributed in 660 herds and calved during 2003-2013 were used. The studied trait was test day milk yield and the model was defined as a quantile regression. All of the estimated regression coefficients were negative, which indicated a decrease in the amount of daily milk production when milk somatic cell counts increased, so that, in the spite of lactation stage, on the basis of absolute value, the lowest and highest regression coefficients observed at ninety-fifth percentile and fifth, respectively. Considering lactation stage in the seventh stage of fifth percentile, the highest decrease was 238 g milk reduction per day, for increase of 100 thousand somatic cells per ml/L of milk, and in the 95th percentile of the fourth stage, the lowest decrease was 64 grams milk reduction per day, for increase 100 thousand somatic cells per ml/L of milk. The results revealed that in high quantiles of daily milk yield, the impact of SCC on milk production decreases indicating that high-producing cows are less influenced in terms of loss of milk production as SCC increases. The difference in the amount of somatic cell count on the amount of milk production in cows with different production potential should be considered in the genetic evaluation of herds.

The aims of this study were to estimate variance components, prediction of genetic parameters and correlations of growth curve parameters of nonlinear models such as Broody, Gompertz, Logistic and von in Kurdi sheep breed. Data comprised of 17659 body weights from birth to yearling of 5074 lambs belonging to 162 rams and 1968 ewes from 1996 to 2013. Growth parameters were estimated by NLIN procedure of SAS V.9.4., and parameters including A, B and K were calculated by individual fit according to the sex of the animal. Variance components were estimated by a mixed model of BLUPF90 and considering the influences of fixed effect including sex, birth type, year and month of birth. Heritability of mature weight was low in all models (0.05 to 0.09) and showed the low participation of genetic variance from the phenotypic variance. Therefore, to achieve the desired genetic gain and high accuracy, more records of lamb growth parameters are required for each ewe and ram, as well as, the improvement of environmental circumstances. Regarding high positive genetic and environmental correlations of A-B, it is expected that selection of animals with higher birth weight or improving the environmental circumstances, lead to a height mature weight, which needs more investigation over the increasing of lambing ease. The medium and negative genetic and phenotypic correlations between A-K imply the negative relationship between the mature rate and weight.

To determine the best function for describing lactation of Najdi cow in Khuzestan, the day-based milk production test records, collected by Shushtar support station from 1990 to 2014, were used. Records included 2369 data related to 444 first parity cows. To determine the best mathematical function, six functions includind incomplete gamma, wilmink, inverse polynomial, complex logarithmic, Cobby and Le Du, and polynomial regression were evaluated. All functions were fitted using PROC NLIN procedure of SAS software and Gauss-Newton iteration method on day-based milk production test records; and compared based on coefficient of determination R2, corrected coefficient of determination, the mean square error and Akaike index. The results showed that the inverse polynomial function offers a better description for lactation curve in Najdi cattle.  The lactation curve parameters (a, b, c) were estimated 4.4841, 0.2514, 0.00273, and their heritability were 0.354±0.120, 0.280±0.11 and 0.276±0.155, respectively. Moderate heritability suggests the opportunity of genetic response via selection program. Heritability of these traits can be improved by correcting the known environmental impacts.