ﺑﺮآورد ﻣﯿﺰان ﺷﯿﻮع و ﺑﺮرﺳﯽ ﻓﺎﮐﺘﻮرﻫﺎی ﻣﺤﯿﻄﯽ و ژﻧﺘﯿﮑﯽ ﺑﯿﻤﺎری ورم ﭘﺴﺘﺎن و ﻣﺘﺮﯾﺖ در ﮔﺎوﻫﺎی ﻫﻠﺸﺘﺎﯾﻦ

زمینه مطالعاتی: طول عمر گاوها در سود دهی یک مزرعه شیری اهمیت بسزایی دارد و حذف گاوها در نتیجه اختلالات اصلی سلامتی خطر مهمی است که امروزه سیستمهای تولیدی را تهدید می‌کند. ظهور این اختلال‌ها می تواند به بخش‌هایی از قبیل فاکتورهای محیطی و مدیریتی ربط داده شود. اما، مدارکی دال بر وجود یک جزء ژنتیکی نیز برای هر کدام وجود دارد.هدف: هدف از این مطالعه گزارش آماری از میزان شیوع دو بیماری مهم ورم پستان بالینی و متریت ، بررسی عوامل محیطی و ژنتیکی موثر بر این بیماریها، تخمین وراثت پذیری صفات بیماری و اندازه گیری همبستگی میان صفات بیماری و تولیدی در یک گله تجاری گاو هلشتاین است. روش کار: به منظور این پژوهش اطلاعات تندرستی و تولیدی گله ی 1600 راسی گاو هلشتاین در استان آذربایجان شرقی و همچنین اطلاعات شجره ای این حیوانات مورد بررسی و آنالیز قرار گرفت. داده ها از تعداد جمعاً 5052 دوره ی شیردهی از 1796 راس گاو هلشتاین فریزین که در فواصل زمانی 1388 1384 زایمان کرده بودند گرفته شده است. در این مطالعه با استفاده از متغیرهای تولید شیر305روز، نوبت زایش، سال گوساله زایی،فراوانی وقوع دو بیماری ورم پستان بالینی و متریت در دام ها با استفاده از نرم افزار sas با به کارگیری رویه ی لجستیک پیش بینی شده است. داده های تولیدی به کار رفته برای آنالیز مربوط به همان دوره ی شیردهی است که گاو در آن به عنوان دارنده یا فاقد یک بیماری ثبت شده است. یک گاو برای تمام بیماری هایی که در سرتاسر همه ی دوره ی شیردهی اش اتفاق افتاده است مورد بررسی قرار گرفته است. پارامترژنتیکی برآورد شده در این تحقیق وراثت پذیری صفات بیماری بوده واین برآوردها با به کارگیری نرم افزار asrmlصورت گرفته است. نتایج: درصد حیوانات مبتلا در گله برای ورم پستان 3.11 درصد و برای متریت 1.67 درصد بدست آمد که متریت نرخ وقوع پایینتری نسبت به ورم پستان دارد. همچنین میانگین فاصله زایش تا وقوع بیماری 129.5 روز برای ورم پستان و 167.3 روز برای متریت به دست آمد نتیجه گیری نهایی: تجزیه و تحلیل ارتباط بین شیوع متریت و شیر 305 روز، نوبت زایش، سال گوساله زایی و فصل گوساله زایی نشان داد که هیچکدام از فاکتور های خطر بررسی شده اثری بر روی وقوع بیماری ورم پستان بالینی نداشتند. بیماری متریت وراثت پذیری کمتری نسبت به بیماری ورم پستان بالینی دارد.

prevalence and estimation of effective environmental and genetic factors on mastitis and metritis in holstein cows

introduction: the longevity of cows is crucial to the profitability of a dairy farm, and the culling of cows as a result of major health disorders is a significant risk that threatens production systems today. the possibility of taking diseases into account in the selection of dairy cows depends on the economic importance of the diseases. mastitis and metritis are common diseases among dairy cows that are considered as risk factors for culling cows. the onset of these disorders can be attributed to factors such as environmental and managerial factors, but there is also evidence of a genetic component to each. many genes are associated with resistance or susceptibility to mastitis and metritis in cattle, and their alleles have been reported. subclinical mastitis seems to be one of the most important and damaging diseases threatening dairy cattle herds along with reproductive diseases, lameness and possibly some other common diseases such as para tuberculosis. obviously, reducing production costs supports the profitability of dairy farms. by studying the relationship between the incidence rate and health disorders, in order to minimize the deaths due to health disorders, more emphasis has been placed on the health management of cows. the direct and adverse effects of mammary gland disorders (mastitis and nipple injury) on culling are well documented, while there are differences of results on the correlation between reproductive disorders and culling. contradictory results may be due to differences in the purpose of the study, population, or the methods used. many factors such as age, breed, production level, and calving season can play a role in the incidence of diseases. aim: the purpose of this study is to report the prevalence of clinical mastitis and metritis, moreover to investigate environmental and genetic factors affecting these diseases, to estimate the heritability of disease traits and to measure the correlation between disease and production traits in a holstein cattle herd. due to the fact that health records are not recorded in the country’s farms in a regular and uniform manner, conducting this research is an experiment to collect this type of information so that in the future models can be provided for all holstein cows in iran to consider disease relating traits. material and methods: data of 5052 milk yield from 1796 holstein frisian cows has been gathered that had parturition from 2005 to 2009. in this study, using the 305 day milk production variables, parity, year of calving, the frequency of occurrence of clinical mastitis and metritis in cattle diseases using sas software, using logistic procedure is estimated. the cows have been studied for all the diseases that occurred in all milking period. in logistic regression analysis, the effect of 305 days of milk and other factors in the occurrence of the disorder was investigated as a binary model. the effect of the lactation period in which the disorder was created was included in all analyzes and the fixed effects included milk for 305 days, calving period, calving year and calving season.log [p. (1 p)] = b0 + b1 * milk305 + b2 * parity + b3 * calveyear + b4 * calve seasona coefficient of b1 is assigned for the risk factor of milk production, a coefficient of b2 is assigned for the parturition, a coefficient of b3 is assigned for the factor of calving year and a coefficient of b4 is assigned for the factor of calving season. b0 is the logistic regression estimate if there is no predictor other than the response variable in the model. for each estimate of regression coefficients, the probability level, standard error and 95% confidence interval are also calculated. for a particular disease b1, b2, b3 and b4 are regression coefficients. estimated genetic parameter in this research was heritability of diseases traits that has been done with asreml software. results and discussion: metritis incidence rate is lower than mastitis. the percentage of animals with mastitis and metritis in the herd was 3.11% and 1.67%, respectively. the average calving interval for metritis incidence was 167.3 days and 129.5 days for mastitis. data analysis of correspondence of metritis and 305 milk yield, parity, the year and the season of calving showed none of the risk factors had relation with the occurrence of clinical mastitis. the heritability of clinical mastitis and metritis were estimated to be 0.27 and 0.23, respectively. we could not find a relationship between milk production and metritis. can we consider the increase in milk production as a risk factor for disease occurrence? it is very difficult to prove and explain this relationship and there are many contradictions between the results of other studies. from the lack of a proven correlation between milk production and the occurrence of diseases, it can be concluded that if proper management and nutrition provided based on the biological needs of high yielding cows, then cows with high milk production will not necessarily suffer from diseases in comparison with low yielding cows.genetic studies have shown a positive correlation between mastitis and milk production. erb (1987) and dehu and martin (1984) concluded that high milk production could not be a risk factor for mastitis. a study of ayrshire cows in finland found that cows with higher milk production during the previous lactation period were at increased risk for mastitis (grun et al. 1989 and grun et al. 1990). there are few documented findings on the association between milk production and the incidence of disease. of course, it should be borne in mind that milk production is not the only risk factor for the disease. concerning diseases in holstein dairy cattle it seems the occurrence of the disease can also be the result of breeding and nutrition conditions and management. however, identifying all relevant factors and determining their quality and relative importance is difficulty accessible. it is also not easy to estimate all possible interactions between production and disease traits, even with the efficiency of today’s computer technology.conclusion: in dairy cattle genetic improvement programs, we suggest to record and estimate the breeding values for disease traits and consider them in multi trait selections among elite sires. the estimated heritability of metritis was lower than clinical mastitis. keywords: holstein friesian cows, clinical mastitis, metritis, milk 305 days, heritability.