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Benchmarking reproductive efficiency in commercial dairy herds in California
Our objective was to benchmark reproductive efficiency for both Holstein (HO) and Jersey (JE) dairy herds in California (CA). Reproductive records from DHIA’s database (AgriTech Analytics) for all cows that calved in CA in 2011 were used. The initial dataset included artificial insemination records from 511 dairy operations and 554,523 lactating cows (501,616-HO; 52,907-JE) in a total of 1,377,729 breedings (1,262,926-HO; 114,803-JE). Only herds reporting at least 200 breedings and having overall conception results within 15% to 75% were included in the analysis. Breeding intervals that were less than 3d or greater than 150 days were discarded from final analysis. In addition, cows that were sold or died before pregnancy confirmation or re-inseminated (and assumed non-pregnant) were disregarded. Conception rate (CR) was defined as number cows pregnant by total number of AIs. Service rate (SR) was calculated based on the average interval between breedings (Woods-index). Statistical analysis were performed with the Proc HPMIXED of SAS (version 9.3), with herd and cow used as a random effect in the model. Overall, milk production level 305ME did not affect (P>0.10) CR or SR results for either HO or JE cows. However, CR and SR from JE-cows (CR=38.8%; SR=66.7%) were better (P<0.05) than in HO-cows (CR=32.8%; SR=60.1%), but with great variation in milk production and reproductive performance within each breed. As suspected, CR was drastically affected (P<0.05) by season, with a major decrease for both breeds during the warmer months of the year – as shown in the Table 1. In contrast, SR remained fairly constant throughout seasons and this was independently from cow breed. In summary, these results indicate a major detrimental effect of summer heat stress on fertility of California dairies that seem to disturb both HO and JE cows.
Table 1. Conception rate (CR) by month for lactating Holstein (HO) and Jersey (JE) cows
Year |
2011 |
2011 |
2011 |
2011 |
2011 |
2011 |
2011 |
2011 |
2011 |
Month |
Apr |
May |
Jun |
Jul |
Aug |
Sep |
Oct |
Nov |
Dec |
CR-JE |
47.2%a |
45.3%a |
42.3%a |
34.5%b |
34.0%b |
31.2%c |
35.6%b |
41.0%a |
43.2%a |
CR-HO |
37.3%a |
37.5%a |
33.2%b |
28.2%c |
27.6%c |
25.9%c |
28.7%c |
35.0%a |
38.5%a |
a,b,c different letters within rows (P<0.05)
Keywords:
Dairy cows
Heat stress
Breed