Abstract
The objective of this study was to determine how milking frequency, estradiol cypionate (ECP) postpartum therapy given at 1 week after calving, and biweekly bovine somatotropin (bST) administration alter lactational and reproductive outcomes in dairy cattle. Holstein cows (n=144) were randomly assigned to eight treatments (18 cows per treatment): 1) twice daily milking frequency (2x), 10-mg injection of ECP at 1 week after calving (ECP), and bST (given biweekly according to label beginning in the ninth week of lactation); 2) 2x milked, oil (cottonseed oil vehicle for ECP), bST; 3) 2x milked, ECP, and no bST; 4) 2x milked, oil, and no bST; 5) four-times daily milking frequency (4x; first 30 days in milk then 2x thereafter), ECP, and bST; 6) 4x milked, oil, and bST; 7) 4x milked, ECP, and no bST; and 8) 4x milked, oil, and no bST. Milk yields were recorded at each milking during the first 90 days of lactation. Milk samples were collected weekly at each milking and composited to determine milk components (percentages of fat, protein, lactose, solids-not-fat [SNF], milk urea nitrogen [MUN], and somatic cell count [SCC]). Energy-corrected milk yields were calculated for the first 90 days and for whole lactation yields (305-2xME standardized lactation records). Ovulation before first AI was synchronized beginning between 59 and 72 DIM using 100 :g of GnRH given 7 days before 25 mg of PGF2, followed in 24 hr by 1 mg of ECP. Cows were inseminated after detected estrus or at 48 hr after ECP. Pregnancy rates were assessed by transrectal ultrasonography 28-30 days after AI. Postpartum ECP therapy increased milk production for first-lactation 2x cows, but decreased milk yields of the multiparous 4x cows until bST restored those yields. Pregnancy rates were greater for the 4x cows given the postpartum ECP therapy injection, despite fewer cows cycling before AI. In conclusion, postpartum ECP therapy increased pregnancy rates in 4x cows, but had a detrimental effect on milk yields of 4x milked cows unless bST was administered.
Highlights
Conception in lactating dairy cows began to decline in the mid 1970s and accelerated in the late 1980s during which time average milk yield for DHIA herds in the U.S has increased steadily from nearly 15,000 to nearly 21,000 lb per cow
The objective of this study was to determine how milking frequency, estradiol cypionate (ECP) postpartum therapy given at 1 week after calving, and biweekly bovine somatotropin administration alter lactational and reproductive outcomes in dairy cattle
Pregnancy rates were greater for the 4x cows given the postpartum ECP therapy injection, despite fewer cows cycling before AI
Summary
Conception in lactating dairy cows began to decline in the mid 1970s and accelerated in the late 1980s during which time average milk yield for DHIA herds in the U.S has increased steadily from nearly 15,000 to nearly 21,000 lb per cow. Because milk yield per cow can be increased by daily milking frequency and the administration of bovine somatotropin (bST), many dairy producers have opted to milk cows three times daily and use bST to increase gross income and thereby reduce fixed costs that are associated with empty milking parlors. Another common practice on many dairies is the use of a prophylactic postpartum therapy of estradiol cypionate (ECP) to assist transition cows that may have had calving difficulties and retained placentae. Legal label indications for ECP include: 1) correcting anestrus (absence of heat period ) in the absence of follicular cysts in some cases; 2) treating cattle having a persistent corpus luteum due to certain causes; 3) expulsion of purulent material from the uterus in pyometra of cows; and 4) stimulate uterine expulsion of retained placentas and mummified fetuses
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
