Reproductive performance is quickly becoming the biggest challenge in dairy herds’ profitability, says Ricardo Chebel, University of Minnesota veterinarian. Most dairymen are quick to recognize reproductive inefficiencies as one of the most important and frustrating challenges in their dairy operations.
In 2007, the National Animal Health Monitoring System demonstrated that reproductive inefficiency is second only to mastitis as a cause of involuntary culling (culling other than for low production).
Many factors affect the reproductive ability of dairy cows and they are physiological, pathological and managerial in nature, says Chebel.
“Mastitis is perhaps the single most important disease affecting lactating dairy cows because of the economic losses related to lower milk yield, milk discarded, culling, and antibiotic therapy of cows,” he notes.
Another very important consequence of mastitis is reduced reproductive performance. Researchers at the University of Tennessee demonstrated that cows that had clinical mastitis before first postpartum AI had extended calving to AI interval (93.6 vs. 71 days).
The inflammatory and immune responses to the intra-mammary infection may affect reproduction by preventing ovulation and resumption of cyclicity after calving, by reducing fertilization rates and embryo development, and by compromising embryonic development and pregnancy establishment and maintenance (i.e. reduced embryonic/fetal survival and increased incidence of abortions), Chebel explains.
But what about body condition score?
It is normal for lactating dairy cows to lose body condition during the first 60 days in milk (DIM), says Chebel, but the body condition score (BCS) during the first 60 DIM and at 60 DIM are correlated with fertility.
Cows that lose 1.0 or more BCS units from calving to 60 DIM are more likely to be anovular (40.6 vs. 17.9 percent) and cows that have BCS less than 2.75 at 60 DIM are more likely to be anovular than cows with BCS greater than 3.0 (27.0 vs. 14.4 percent).
Source: University of Minnesota