The present investigation is dealing with the dairy cows of different genotypes of dam in field condition considering the productive and reproductive performance of cows under the district Artificial Insemination (AI) center, Rajshahi and was conducted at 33 AI Sub-centers/Points of greater Rajshahi district from 1993 to 2002. The information regarding productive and reproductive performances of 313 dairy cows of different breeds belongs to 7 genotypes of bulls were accumulated from the record sheet maintained by field assistants (artificial inseminator) at 33 AI Sub-centers/Points of District AI center, Rajshahi. Thirty-three field assistants (AI) of respective AI Sub-center/Point were brought at District AI center, Rajshahi for the training on productive and reproductive performances records and organized by Assistant Director of District AI center, Rajshahi.
A questionnaire was made on dairy cows and detail instruction was given to the trainer and owner of cows. The main instructions were how to fill up the questionnaire for dairy cows. The contents of this questionnaire such as date of AI, bull ID, type of semen used, breed of bull, dam history like genotype of dam, milk production, date of birth, birth weight and management of progeny, age of puberty, age at first fertile service, age at first calving, gestation length, post-partum heat period, days open, wastage days, S/C, milk production/day, peak milk production per day, lactation length, dry period, weaning period, calving interval and management of dairy cows. The questionnaire had two parts, one was for Field assistant (artificial inseminator) and other was for owners of cows. A total of 500 questionnaires were distributed among the 33 field assistant (AI) to recorded the progeny information from the field. Field assistants (AI) had collected necessary information from AI and progeny register as obtained from respective AI Sub-centers/Points and rest of the information were collected from farmers by direct interviewing as per questionnaires.
A total of 313 questionnaires for respective cow’s information was collected from properly filled up forms or information collected by 33 Field Assistants (AI) of AI Sub-centers/Points of greater Rajshahi district. After collecting the questionnaire, preliminary sorting and checking, data were prepared for analysis.
The dairy cows of dam were classified into 5 genetic groups according to their nature of inheritance such as Group I: LocalxFriesian (LxF) cross, Group II: LocalxSahiwal (LxSL) cross, Group III: Local (L), Group IV: LocalxSahiwalxFriesian (LxSLxF) cross and Group V: LocalxSindhixSahiwal (LxSxSL) cross.
Feeding and management: Semi-intensive management system was maintained for rearing of dairy cows. This means that the cows are tied up and provide with minimum facilities for exercise. Feeds, both roughage and concentrate, were procured by the farmers and fed while tied up. The house of the animal was made of straw and bamboo and brick. Gunny bags were spread over the ventilation to protect them from rain and cold wind at night during winter season. Every day the floor and the manger were cleaned. The animals were identify by the farmer’s name. The animals were attached to the dwelling. Fumigation was always done once a day in the evening by burning dry leaf and straw to control mosquitoes. Dry straw was used as bedding during winter season. The commonly used feed ingredients were rice straw, wheat bran, rice bran, oil cake, rice gruel, rice crust, pulse bran, pulse crust, molasses, flour, common salts and green grass. On an average, ration per dairy cow contained approximately 2.5 kg concentrates, 5.5 kg rice straw and 15.0 kg green grass with ad libitum water. The amount of concentrate was raised to 5.0 kg for high milking of cows. The total amount of concentrate required per day were divided into parts and fed the cows twice daily. Rest of the period, the animal was maintained with rice straw and green grasses.
Insemination and medication: Artificial insemination was done by 33 trained field assistants (AI) with chilled or frozen semen of Friesian, Sahiwal bull or their cross-bred bulls. One FA (AI) was in-charge of each AI Sub-centres/Points for Artificial Insemination (AI) purpose. The farmers regularly de-wormed the cows by specific anthelmintics. All the animals received vaccination against Anthrax, Hemorrhagic septicemia, Black quarter and FMD. The treatment of diseased animal was done both by the Veterinarian and Veterinary technician.
The productive and reproductive performances of dairy cows were recorded.
Design of experiment: Both productive and reproductive traits of cows were used in this study. The collected data covered for five different genetic groups of cows. The number of animals in different AI Sub-centers/Point and groups were unequal.
Statistical procedure: Data were statistically analyzed to calculate the effect of dam genotypes productive and reproductive performance of dairy cow. Various standard statistical procedures had been adopted in this study. The mean and standard deviation for the traits were calculated using SPSS statistical package. Mean of different traits were then tested by Duncan Multiple Range Test (DMRT) to separate the mean of different natures according to Steel and Torrie.