بررسی عوامل موثر بر نسبت جنسی ثانویه گاوهای شیری هلشتاین

نوع مقاله : علمی پژوهشی- سایر

نویسندگان

1 دانشگاه فردوسی

2 دانشگاه فردوسی مشهد

چکیده

نسبت ثانویه جنسی، نسبت گوساله های نر به ماده زنده متولد شده است. مطالعات انجام شده در گونه های مختلف پستانداران نشان می دهد که فاکتورهای متعددی بر نسبت جنسی ثانویه تاثیر دارند. تغییر در نسبت جنسی ثانویه در گاوهای شیری به لحاظ اقتصادی اهمیت داشته و مورد توجه قرار گرفته است و توانایی تغییر آن می تواند درآمد و سوددهی یک گاوداری را تحت تاثیر قرار دهد. هدف از این آزمایش بررسی تاثیر پاره ای از عوامل موثر بر نسبت جنسی در گاوهای هلشتاین ایران بود. در مطالعه حاضر از داده‌های شش گله بزرگ گاو شیری در خلال سال‌های 1375 تا 1389 استفاده شد. میانگین تولید استاندارد شده 305 روز گله‌ها 8145 کیلوگرم (با دامنه 7578 تا 8670 کیلوگرم) بود. گله های مزبور تحت پوشش مرکز اصلاح نژاد ایران بوده و ثبت مشخصات و رکوردگیری آن‌ها به صورت منظم توسط کارشناسان شرکت‌های تعاونی گاوداران انجام می‌شد. این گله‌ها در ناحیه شمال شرقی کشور قرار داشتند. داده های تولیدی (روز تولید و تولید تجمیعی ظیر شیر تصحیح شده بر اساس 60 و 305 روز شیردهی)، داده‌های تولید مثلی (نظیر سال زایش، فصل زایش، نوع زایش، جنس گوساله متولد شده، آخرین اطلاعات مربوط به تلقیح، روزهای باز)، و جزئیات حذف احتمالی از گله و یا مرگ ثبت می‌شد. داده‌های جمع‌آوری شده از گله‌ها پیش از تجزیه و تحلیل مجدداً راستی آزمایی شد. بر اساس اسپرم استفاده شده، اسپرم‌ها به چهار گروه ایرانی، کانادایی، آمریکایی و سایر کشورها (شامل اسپرم‌های تهیه شده از کشورهای اروپایی) تقسیم بندی شدند. برای آنالیز آماری داده ها از مدل رگرسیون لجستیک استفاده شد. نتایج نشان داد که درصد گوساله های نر به گوساله های ماده 53 به 47 بود. در مطالعه حاضر نوع اسپرم مورد استفاده در تلقیح مصنوعی (شامل: ایرانی، آمریکایی و کانادایی) تاثیر معنی داری بر نسبت ثانویه جنسی نداشت. سال زایش نیز تاثیری بر نسبت جنسی نداشت. نتایج مطالعه حاضر نشان داد که نوع زایمان (طبیعی و یا غیرطبیعی) تاثیر معنی داری بر نسبت ثانویه جنسی داشت (0.001P

کلیدواژه‌ها


عنوان مقاله [English]

Factors Affecting SSR in Holstein Dairy Cows

نویسندگان [English]

  • Alireza Heravi Mosavi 1
  • Abolghasem Golian 2
  • Seyed Jalaa Modaresi 2
1 Ferdowsi University of Mashhad
2 Ferdwosi University of Mashhad
چکیده [English]

Introduction Secondary sex ratio (SSR) is the proportion of males to females at birth. It has been shown in many different mammalian species, many factors are associated with SSR. Changes in secondary sex ratio in dairy cows is considered economically important and the ability to change it could affect the revenues and profitability of a dairy farm. Thus, sperm or embryo sexing techniques in recent years has attracted more attention. Most breed of dairy cattle are more likely to have female calf is born to use them as replacement heifers and in order to maintain their productive herd number. On the contrary, when the goal is the production of meat, bull calves due to higher growth rates and production efficiency, are more convenient and more economically efficient. The aim of present study was to investigate some key factors affecting SSR in Iranian Holstein cows.
According to Fisher, the sex ratio in the population under the control of natural selection is not always the same. There is overwhelming evidence to support the theory that shows Fisher Primary and secondary sex ratio sex ratio can deviate from this balance and natural selection caused a change in this ratio can be in certain circumstances. For example, the secondary sex ratio of 52:48 has been reported in dairy cows. Studies on mammalian species suggest that several factors, including latitude of the location, the dominant regional climate model, time and frequency of mating to ovulation, diet, age of parents, physical score, breed and produced eggs from ovarian left or right can have a significant effect on the secondary sex ratio. Weather conditions may modify the internal environment and the effect on physiological mechanisms or through the impact on the frequency and type of foods available to parents, the secondary sex ratio is impressive. The impact on the quantity and quality of parent's access to food sources in many species of mammals, the sex ratio has been fixed. Previous reports have shown that high environmental temperature and higher rates of evaporation from a week to a month before conception secondary sex ratio was increased.
Materials and method The demographic, production and reproduction data of six large dairy farms between years 1375 and 1389 were used. The rolling average of 305 d fat corrected milk yield was 8145 kg with a range of 7578 to 8670 Kg. Breeding Center of Iran and the herds covered by the registration and recording them on a regular basis carried out by experts dairy cooperatives. The flocks were in the area northeast of the country. Production data (date corrected milk production and the cumulative production by 60 and 305 days of lactation), reproductive data (such as calving year, calving season, type of birth, sex of calf, the latest information on AI, days open) , and details the possible removal of the flock or death were recorded. Data were collected from flocks before the analysis was re-verification. Used by sperm, sperm into four groups: Iranian, Canadian, American and other countries (including sperm taken from European countries) groups. The data were analyzed using multivariate logistic regression model.
Statistics 0/05 was used to ensure meaningful results.
Results and discussion Results showed that the ratio of males to females was 53 to 47. Origin of the sires (including Iranian, American, or Canadian) had no impact on secondary sex ratio. Type of calving (eutocia vs. non-eutocia calving including dystocia and still birth) had significant impact on SSR (P

کلیدواژه‌ها [English]

  • Holstein dairy cow
  • Secondary sex ratio (SSR)
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