H.D. Norman,1 J.R. Wright, S.M. Hubbard, R.H. Miller, and J.L. Hutchison
Animal Improvement Programs Laboratory, Agricultural Research Service, USDA, Beltsville, MD 20705-2350
2008 J. Dairy Sci. (?)
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Reproductive information from USDA's national dairy database since 1996 was used to provide yearly means in 8 traits in the Holstein and Jersey breeds. Respectively, data for Holsteins and Jerseys were from 21,528 and 1827 herds, 5,348,567 and 288,373 cows, 10,497,511 and 580,466 lactations, and 23,230,972 and 1,158,973 inseminations. Similar information was given for some reproductive traits by parity and service number for both breeds, as well as by geographical region in Holsteins. The Northeast had the highest conception rate (32%) and the fewest breedings per lactation (2.3); the Southeast had the lowest conception rate (23%) and the most breedings per lactation (2.7). Days to first breeding declined in Holsteins between 1997 and 2006, from 94 to 86 d, but any year differences for Jerseys were sporadic. First service 70-d non-return rate declined in both breeds by 4 to 7%, while number of services per lactation increased by 0.3 to 0.4. Later parities had lower first service 70-d non-return rate and conception rate for both breeds and longer days to first breeding for Holsteins compared to early parities. In spite of this, number of services per lactation remained fairly constant across parities for Holstein and increased slightly in Jerseys, perhaps reflecting a difference in willingness to keep rebreeding. First- and 2nd- service 70-d non-return rate declined as parity increased for both breeds. Second-service conception rate was highest within parity for both breeds, 1 to 2% above first-service conception rate. Conception rate for specific services generally declined with parity for both breeds. Trends appear to be impacted by geographical region, producer preferences, and increased use of synchronized breedings.
(Key words: non-return rate, conception rate, reproduction, trends)