Occurrence of repeat breeding in crossbred dairy cattle

The present research work was undertaken to evaluate the occurrence of repeat breeding (RB) among crossbred dairy cattle for three years from January 2017 to December 2019. Crossbred cows having apparently normal genitalia and showing regular oestrous cycle but failing to conceive even after three consecutive inseminations were selected as RB cows based on data collected from breeding registers. The occurrence of RB in the year 2017, 2018 and 2019 were 29.20, 24.12 and 19.52 per cent, respectively with an overall occurrence of 23.60 per cent. Detailed clinico-gynaecological and ultrasonographic examinations of 41 RB cows were carried out for the identification of various etiological factors during the study period (September 2019 to August 2020). Samples for endometrial cytology were collected during oestrus by cytobrush technique to rule out cytological endometritis (sub clinical endometritis). The occurrence of various identified causes of RB were cytological endometritis (17.07 %), fibrosis of cervix (7.31 %), endometritis (7.31 %), follicular cyst (4.88 %), kinked cervix (2.44 %), uterine unicornis (2.44 %) and other reasons (58.54 %). Repeat breeding is a major cause of infertility in crossbred dairy cattle and early diagnosis is essential for the effective management and to enhance production.

↵Assessment on Milk Yield and Reproductive Performances of Crossbred Dairy Cattle in Selected Dairy Production Systems of Central Highlands of Ethiopia

Background: Productive and reproductive performances are the most important parameters in the Ehiopian dairy sector. The objective of the current study was to assess milk yield, reproductive performances of crossbred dairy cattle and occurrence of reproductive health problems and veterinary services provider/s. Methods: A cross-sectional study using semi-structured questionnaire was used to collect information from 160 randomly selected dairy farm owners found in urban and peri-urban areas of Assela, Bishoftu, Holetta and Sululta of the central highlands of Ethiopia. Result: The higher average daily milk yields were 11.7 and 11.2 litres in urban and peri-urban Bishoftu. The average age at first service of crossbred dairy heifers was 18.8 months in urban and 19.1 months in peri-urban Bishoftu, respectively. The average age at first calving of crossbred dairy heifers was 27.8 months in urban Bishoftu and 28.1 months in peri-urban Bishoftu areas. The longest average age at first service (29.3 months) and age at first calving (38.3 months) were in peri-urban Assela. The number of services per conception was 1.4 in urban Assela and 1.3 in peri-urban Assela and these were shorter than the 1.65 from urban Bishoftu and the 1.85 of peri-urban Bishoftu areas. The average 168.0 days calving to conception interval from peri-urban Assela was the longest calving to conception interval in this study. The average calving intervals 14.9 and 13.9 months of peri-urban Assela and Sululta were relatively longer than the respective urban areas.

Characterization of Lactation Curve Patterns using Non-linear Models in Crossbred Dairy Cattle

Background: Lactation curve patterns are currently integrated in dairy cow’s management software. Lactation curve modeling is useful for monitoring individual yields for diet planning, determining optimum strategies for insemination and genetic evaluation. It also helps for predicting expected missing values on field records and gives concise summary of biological efficiency and persistency of dairy cows.Methods: The study was aimed to characterize the lactation curve pattern for crossbred dairy cattle using different non-linear models. During the period 1991 to 2018, daily milk yield (DMY) consisted of 281698 records of 750 crossbred dairy cows maintained at Livestock Farms. GADVASU, Ludhiana, were collected for the study. Different non-linear models viz. exponential decline function (EDF), parabolic exponential model (PEM), inverse polynomial model (IPM), gamma-type function (GTF), mixed log function (MLF) and Ali and Schaeffer model (ASF) were used for the analysis. The model(s) that best fit and describe the curve characteristics was selected on the basis of coefficient of determination (R2), coefficient of variation (CV), Akaike information criterion (AIC) and mean square error (MSE).Result: The study clearly revealed that the PRM gave highest fit to DMY data with R2, MSE, AIC and CV values of 98.10%, 0.087, -743.31 and 2.37%, respectively. The IPM had also best fitted the observed DMY data with highest R2 (98.05%), lower MSE (0.089), low AIC (-735.8972) and lower CV (2.40%) values. The fitting of observed DMY data with predicted DMY were also found to be higher in the MLF (R2= 96.46%, MSE= 0.159, AIC= -558.16 and CV= 3.21%) and GTF (R2= 95.85%, MSE= 0.190, AIC= -505.24 and CV= 3.50%), whilst the EDF and PEM Models depicted relatively low fit to the DMY data when compared with the other non-linear models. However, IPM and GTF models can be used for accurate prediction of daily milk yield in the crossbred cattle population because they were typical standard lactation curves.