Study areas and population:
The study was conducted at Rajshahi district in Bangladesh. The cows were selected from 6 Upazilas viz. Charghat, Puthia, Poba, Godagari, Tanore, Mohanpur and 4 metro thanas were Motihar, Boalia, Rajpara, Shahmukdhm of Rajshahi district. Fifty cows were randomly selected from each upazila and metro thana for this study on a total of 500 dairy cows.
Method of data collection:
The data were collected directly from the dairy cows owners/farmers/attendant by using questionnaires and diagnoses of reproductive disorders were made on the basis of the history, clinical signs and response to treatment during the period from July 2013 to June 2015. The data were collected from the randomly selected farms by the researcher every three (3) months interval in the year. After collecting the information, data were prepared for analysis.
Reproductive traits of cows studied:
The following reproductive traits of dairy cows were studied in this study.
Age at puberty: The age at which a heifer first shows the estrous signs and behaviors may be defined as age at puberty. It was measured in month (m).
Age at first calving: It is defined as the age when a heifer first calving a newborn calf. It was measured in month (m).
Post-partum heat period: It is considered as the interval between date of calving and the date of first insemination or first heat show after parturition. It was calculated in days (d).
Service per conception: The average number of services or inseminations required for each successful conception in case of heifer and cows.
Days open: Days open was measured in days. Day’s open is referred as interval from parturition to date of conception of cows. Calving interval: The number of days between two successful calving of the same cows or the period from one calving to the next was termed as calving interval. It was measured in days.
Definition of recorded diseases taken mostly from Sarder et al. (2010):
Abortion: Abortion is a condition in which the foetus is delivered live or dead before reaching the stage of viability and in which the delivered foetus is generally visible by naked eyes.
Anoestrus: Lack of expression of the oestrus at an expected time is called anoestrus. Clinically if a heifer is 18 or more months old or a cow has passed (40-60) days post-partum but did not show oestrus the condition is referred as anoestrus.
Metritis: Metritis is the inflammation of the uterus generally caused by infectious agents. Usually, cows have red to brown discharge during the first two weeks after calving. If discharge persists beyond two weeks or if the discharge is foul-smelling, this is evidence of metritis.
Mastitis: The term mastitis refers to inflammation of the mammary gland regardless of the cause. It is characterized by physical, chemical and usually bacteriological changes in the milk and by pathological changes in the gland (Radostits et al., 2006). Diagnosis of mastitis was based on history, physical abnormalities of udder and gross abnormalities in the milk like discoloration and presence of clots/flakes. Palpation of udder revealed enlarged and painful with the presence of clots/ flakes in the milk confirmed the diagnosis of mastitis.
Retained placenta: A cow was considered to have retained placenta when the foetal membranes were visible at the vulva or were identified in the uterus or vagina by vaginal examination more than 24 hrs after calving.
Repeat breeders: Cows failing to conceive after a defined number of inseminations (generally three or more) with fertile semen, have been classified as repeat breeders (Levine, 1999).
Data management and analysis:
The data obtained from the questionnaire was entered into Microsoft Excel 2007 and transferred to SPSS version 17. Data were statistically analyzed to estimates the clinical trends of reproductive performances and reproductive disorders of dairy cows. Various standard statistical procedures (percentages, mean and chi-square test etc.) had been adopted in this study. Mean of different traits were then tested by using Analysis of Variance (ANOVA) by Duncan Multiple Range Test (DMRT). Descriptive statistics was done to explore the clinical trends of reproductive disorders of cows at Rajshahi district. Data were presented as Mean±SE. P<0.05 was considered as significant.