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Hierarchy of factors affecting behavioural signs used for oestrus detection of Holstein and Normande dairy cows in a seasonal calving system

Cutullic, Erwan, Delaby, Luc, Causeur, David, Michel, Guillaume, Disenhaus, Catherine
Animal reproduction science 2009 v.113 no.1-4 pp. 22-37
dairy cows, estrus detection, standing reflex, female reproductive system, biomarkers, body condition, lactation, validity, calving, seasons, milk yield, Holstein, dairy farming, seasonal variation, estrus, mating behavior
As oestrous expression of dairy cows has decreased over the last decades oestrus detection has become more difficult. The objective of this study is to identify the main factors that affect oestrus detection in seasonal calving dairy cows, and to establish their relative importance. In each of 5 years 36 Normande and 36 Holstein cows were assigned to a Low or High winter-feeding level group. Half of each group was then assigned to a Low or High pasture-feeding group. The Low-Low strategy resulted in the lowest milk yield and the greatest body condition (BC) loss from calving to nadir BC score (6302kg; -0.98unit). The High-High strategy had the converse effect (7549kg; -0.75units). Low-High and High-Low strategies had intermediate values. The Normande cows had lower milk yield and BC loss than Holstein cows (6153kg versus 7620kg; -0.82unit versus -1.20unit). A database of 415 observed spontaneous oestruses was created. Oestruses were classified according to detection signs: (1) standing to be mounted, (2) mounting without standing, (3) other signs without standing or mounting (slight signs). Presence of another cow in oestrus, access to pasture, Normande breed and Low-Low strategy increased standing detection. In the Normande breed, 97% of oestruses were detected by standing while combining the presence of a herdmate in oestrus and access to pasture with a milk production of less than 6550kg. Holstein cows had a higher frequency of slight signs oestruses than Normande ones, which was associated with a decreased subsequent calving rate (P <0.05). In multiparous Holstein cows, the odds of slight signs detection was multiplied by 7.8 for the High-High group in comparison with the Low-Low group (P <0.05). In our study milk yield had an effect on oestrus detection which was not explained by BC loss. As High-High cows produced more milk than others, we logically found that an increase in milk yield increased slight signs detection. Conversely, as they lost less BC than others, BC loss improved the chance of standing or mounting detection. These two results show that an increase in milk yield may reduce oestrous behaviour even if BC loss is moderate. Oestrus detection is crucial in seasonal compact calving systems. High phenotypic milk yields appear unsuitable with such systems in regard to depressed oestrous behaviour.