Associations between decreased fertility and management factors, claw health, and somatic cell count in Swedish dairy cows

Abstract

The aim of this retrospective single-cohort study was to investigate if a rapid change in feeding, management, or housing or an increasing incidence of claw diseases or udder health problems is associated with decreased reproductive performance. Data on individual cows and herds were retrieved from the Swedish official milk recording system and questionnaire data on feeding system was obtained from the regional dairy associations. In total, 63,561 cows in 759 herds were included in the study. The associations between the probability of pregnancy at first insemination and number of inseminations per animal submitted for artificial insemination and potential predictor variables were investigated using a logistic regression model and a Poisson regression model, respectively. The results indicated that cows with severe claw lesions or an increasing somatic cell count after calving had a lower probability of pregnancy at first insemination and had a higher number of inseminations per animal submitted for artificial insemination than healthy cows. Variables representing a change in housing, production system, or milking system within the period from 6 mo before calving until establishment of a new pregnancy were significantly associated with decreased reproductive performance. No differences in fertility were observed between cows milked in an automatic milking system compared with cows milked conventionally. The results indicate that a change of system, rather than the actual type of milking or housing system negatively affects reproductive performance. Special attention should therefore be paid to the fertility of cows when the herd management is changing. It is also important to prevent claw lesions and increasing cell counts after calving to avoid a decrease in reproductive performance.

Effect of Some Factors on Number of Services per Conception in Dairy Cows

“…They obtained SPC of 1.9-2.4 semen doses, with the highest values found in the early lactation periods (up to 60 days), which corresponds with our findings. Also Swedish studies [25] indicate that early insemination of the cows after calving (<60 days) results in a higher number of services per conception, recommending that the inseminations should be shifted in time to make them more effective.…”

“…This is due to the high nutritional requirements that are difficult to meet. The nutrients supplied are in the first place used for maintenance and milk production [27,28], leading to competition between milk yield and fertility [9,25], thus resulting in poorer SPC value.…”

“…Likewise, Gunay and Gunay [35] recognized clinical mastitis as a factor reducing fertility, with SPC increasing to 2.1 and 3.4 in the affected groups compared to 1.8 in the control group. Also Lomander et al [25] consider increasing SCC (from less than 200 thous. cells/ml to more than 200 thous.…”

Effect of signs of oestrus, disease stressors and cow activity on pregnancy rate following artificial insemination

“…Of note, Lomander and others (2013) showed that an elevated SCC per se at the time of AI was not as deleterious to fertility as an increasing SCC shift, indicating active development of clinical/subclinical mastitis. Also, Lavon and others (2010) identified 30 per cent of cows with subclinical mastitis that had an extended oestrus-to-ovulation interval of 56 hours compared with 28 hours in the remaining 70 per cent infected cows; there was no relationship with the level of SCC in affected cows.…”

High somatic cell counts and changes in milk fat and protein contents around insemination are negatively associated with conception in dairy cows

“…Recent studies have clearly shown that both the clinical and subclinical mastitis are associated with deteriorated fertility parameters, such as longer intervals from calving to conception, increased services per conception, and increased days open [8][9][10]. The odds ratio between clinical mastitis or high somatic cell count (SCC) and successful conception has varied from 0.40 to 0.85 [11][12][13][14]. The relationship between the severity of mastitis and conception rate appears to have a linear trend.…”