Reproductive performance of dairy cows in a pasture based Automatic Milking System research farm: a retrospective analysis.

A retrospective study of 365 cows with 798 lactations was conducted to identify the production and health traits associated with reproductive outcome variables in an automatic milking System (amS) research farm. Generalised linear mixed model analyses were performed to determine the factors associated with the outcome variables (100day pregnancy rate and conception within two inseminations). In 36% of lactations, cows were pregnant by 100 days in milk (DIm) and in 75% of lactations, cows had conceived within two inseminations. Cows that were first inseminated after d 79 of lactation were less likely (odds ratio: 0.18, P< 0.001) to be pregnant by 100 DIm compared with cows first inseminated before d 79 of lactation. moreover, cows that showed first oestrus after d 57 of lactation had a reduced likelihood (odds ratio: 0.57) of being pregnant by 100 DIm compared with cows showing first oestrus before d 57 of lactation. Cows that were producing milk with a fat to protein ratio in the range of 1.21 to 1.30 had the highest odds (odds ratio 2.0) of conceiving compared to cows that were producing milk with a fat to protein ratio less than (or equals to) 1.09. Cows in the bottom two quartile of milk production (100-day cumulative milk yield of 1950 kg or less) were less likely (P< 0.05) to conceive within two inseminations compared with cows producing more than 2521 kg. Cows were more likely to be pregnant by 100 DIm if they were detected in oestrus and inseminated sooner, and were not within the bottom two quartiles for milk production.

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5th Australasian Dairy Science Symposium

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978-0-646-58966-4

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