Progress 07/01/01 to 06/30/06
Outputs
Trials were conducted to examine various management procedures on reproductive performance in lactating dairy cows. The effect of length of voluntary waiting period (VWP) and the time of initiation of BST supplementation on lactation and reproductive performance was examined. It was found that extending the VWP by 56 d (from 56 to 112 DIM) only increased the days to conception by 29 d and calving interval by 38 d. Extending the VWP resulted in a higher conception rate at first and second service and a higher pregnancy rate at 305 d. Moreover, the average daily milk yield to 305 DIM and for the complete lactation was increased. Fewer cows left the herd for health or reproductive problems when the VWP was extended. Waiting to initiate the supplementation of BST until 4 wk after the first AI compared to initiating BST supplementation before the start of the breeding program resulted in better reproductive performance without compromising milk yield. The effect of Human
Chorionic Gonadotrotopin (HCG) administration on conception rate at first service and pregnancy rate at 180 DIM in lactating Holstein cows was also examined. Treatments were: (1) control, no HCG treatment; or (2) 3300 I.U. HCG. The HCG is being given i.m. on d 5 after a timed AI to stimulate the formation of accessory CL. Conception rates were not consistently affected by the administration of HCG. First service conception rate to AI based on observed estrus were (49.2% vs 50.0%) and based at a timed AI (20.5% vs 12.0%, control vs HCG, respectively). Conception rates at repeat services were (22.6% vs 31.3%, control vs HCG, respectively). Thus, reproductive performance was improved when cows were bred based on an observed estrus compared to a controlled timed AI. Also, HCG administration of d 5 after AI improved reproductive performance in cows bred at a repeat service but not for first service cows.
Impacts
Profitability of dairy operations might be enhanced by extending the voluntary waiting period before breeding beyond the commonly recommended length and by delaying the start of BST supplementation until after the cows have received their first breeding. Administration of HCG on d 5 after AI did not improve establishment and maintenance of pregnancy in lactating dairy cows bred at first service but did for cows bred at a repeat service. Administration of HCG might have an economic benefit to dairy producers for cows being bred to a repeat service but not for first service cows.
Publications
- No publications reported this period
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Progress 10/01/04 to 09/30/05
Outputs
A trial is in progress to determine if Human Chorionic Gonadotropin (HCG) administration will increase conception rate at first ervice and pregnancy rate at 180 DIM. Lactating Holstein cows are being blocked by calving date and parity and assigned randomly to one of the following two treatments: (1) control, no HCG treatment; or (2) 3300 I.U. HCG. The HCG is being given i.m. on d 5 after a timed AI to stimulate the formation of accessory CL. The breeding program is scheduled so that the first AI will occur after a voluntary waiting period of 66 days. A modified timed AI (TAI) program (Heatsynch) is being used to insure that all cows receive first insemination at the desired time postpartum. The treatment protocol consists of administration of GnRH (100 ug, i.m.), followed 7 d later with PGF and TAI 48 h after ECP. Cows observed in estrus by 24 h after ECP are being inseminated at 24 h and all remaining cows inseminated at 48 h after ECP. Pregnancy is being determined
by evaluation of the reproductive tract per rectum by palpation. Results to date suggest that conception rates were not consistently affected by the administration of HCG. First service conception rates to AI based on observed estrus were (49.2% vs 50.0%) and based on TAI (20.5% vs 12.0%) for control vs HCG, respectively. Conception at repeat services to AI based on observed estrus were (23.4% vs 38.3%) for control vs HCG, respectively. The trial is not yet complete.
Impacts
The original hypothesis was that administration of HCG on d 5 after AI would improve establishment and maintenance of pregnancy in lactating dairy cows. Results to date fail to support this hypothesis for cows bred at first service but might for cows bred at a repeat service. These preliminary findings suggest that administration of HCG on d 5 after AI might have an economic benefit to dairy producers for cows being bred at a repeat service but not for first service cows.
Publications
- No publications reported this period
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Progress 10/01/03 to 09/30/04
Outputs
A trial is in progress to determine if Human Chorionic Gonadotrotopin (HCG) administration will increase conception rate at first service and pregnancy rate at 180 DIM. Lactating Holstein cows are being blocked by calving date and parity and assigned randomly to one of the following two treatments: (1) control, no HCG treatment; or (2) 3300 I.U. HCG. The HCG is being given i.m. on d 5 after a timed AI to stimulate the formation of accessory CL. The breeding program is scheduled so that the first AI will occur after a voluntary waiting period of 66 days. A modified timed AI (TAI) program (Heatsynch) is being used to insure that all cows receive their first insemination at the desired time postpartum. The treatment protocol consists of administration of GnRH (100 ug, i.m.), followed 7 d later with PGF (25 mg, i.m.), followed with ECP (1 mg, i.m.) 24 h after the PGF and TAI 48 h after ECP. Cows observed in estrus by 24 h after ECP are being inseminated at 24 h and all
remaining cows inseminated at 48 h after ECP. Pregnancy is being determined by evaluation of the reproductive tract per rectum by palpation. Results to date suggest that conception rates were not consistently affected by the administration of HCG. First service conception rate to AI based on observed estrus were (44.4% vs 48.5%) and based on TAI (23.8% vs 11.8%, control vs HCG, respectively). Conception at repeat services to AI based on observed estrus were (22.2% vs 27.6%) and based on TAI (16.7% vs 14.3%, control vs HCG, respectively). The trial is not yet complete.
Impacts
Results to date fail to support the original hypothesis that administration of HCG on d 5 after AI would improve establishment and maintenance of pregnancy in lactating dairy cows. If final results confirm the preliminary findings, administration of HCG on d 5 after AI will not have an economic benefit to dairy producers.
Publications
- No publications reported this period
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Progress 10/01/02 to 09/30/03
Outputs
A trial is in progress to determine if Human Chorionic Gonadotrotopin (HCG) administration will increase conception rate at first service and pregnancy rate at 180 DIM. Lactating Holstein cows are being blocked by calving date and parity and assigned randomly to one of the following two treatments: (1) control, no HCG treatment; or (2) 3300 I.U. HCG. The HCG is being given i.m. on d 5 after a timed AI to stimulate the formation of accessory CL. The breeding program is scheduled so that the first AI will occur after a voluntary waiting period of 66 days. A modified timed AI (TAI) program (Heatsynch) is being used to insure that all cows receive their first insemination at the desired time postpartum. The treatment protocol consists of administration of GnRH (100ug, i.m.), followed 7 d later with PGF (25 mg, i.m.), followed with ECP (1 mg, i.m.) 24 h after the PGF and TAI 48 h after ECP. Cows observed in estrus by 24 h after ECP are being inseminated at 24 h and all
remaining cows inseminated at 48 h after ECP. Pregnancy is being determined by evaluation of the reproductive tract per rectum by palpation. Preliminary results suggests that conception rates are not improved by the administration of HCG at either first-service (34.5% vs 36.0%) or repeat-services (21.9% vs 26.2%, control vs HCG, respectively). Additional data are being collected.
Impacts
The expected improvement in establishment and maintenance of pregnancy in lactating dairy cows following the administration of HCG may not be accomplished. Preliminary results fail to show an economic benefit to the administration of HCG on d 5 after AI.
Publications
- No publications reported this period
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Progress 10/01/01 to 09/30/02
Outputs
A trial was initiated to determine if Human Chorionic Gonadotropin (HCG) administration will increase conception rate at first service and pregnancy rate at 180 DIM. Lactating Holstein cows will be blocked by calving date and parity and assigned randomly to one of the following two treatments: (1) control, no HCG treatment; or (2) 3300 I.U. HCG. The HCG will be given i.m. on d 5 after a timed AI to stimulate the formation of accessory corpora lutea. The breeding program will be scheduled so that the first AI will occur after a voluntary waiting period of 66 days. A modified timed AI (TAI) program (Heatsynch)will be used to insure that all cows receive their first insemination at the desired time. The treatment protocol consists of administration of GnRH (100ug, i.m.), followed 7 d later with PGF (25 mg, i.m.), followed with ECP (1 mg, i.m.) 24 h after the PGF and TAI 48 h after the ECP. Cows observed in estrus by 24 h after ECP will be inseminated at 24 h and all
remaining cows inseminated at 48 h after ECP. Pregnancy will be determined by evaluation of the reproductive tract per rectum by palpation or ultrasound. Conception and pregnancy rates will be determined.
Impacts
The administration of HCG is expected to produce accessory corpora lutea and raise circulating progresterone concentrations which is expected to favor the establishment and maintenance of pregnancy. The results could lead to a simple method to improve reproductive efficiency in dairy herds.
Publications
- Alejo,D., and Larson,L. 2001. Effect of time of initiation of the breeding program and bovine somatotropin supplementation on reproduction. Neb. Coop. Ext. MP78-A:26-28.
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Progress 10/01/00 to 09/30/01
Outputs
A trial was conducted to study the effect of length of voluntary waiting period and time of initiation of BST supplementation on lactation and reproductive performance. Holstein cows (n=164) were blocked by pariety and assigned randomly by calving date to a 2X2 factorial arrangement of treatments. The two factors were: 1) voluntary waiting period (VWP, 56 DIM or 112 DIM), and 2) time of first BST administration (3 d before the start of the breeding program or 4 wk after the first AI). It was found that extending the VWP by 56 d (from 56 to 112 DIM)only increased the days to conception by 29 d and calving interval by 38 d. Extending the VWP resulted in a higher conception rate at first and second service and a higher pregnancy rate at 305 d. Moreover, the average daily milk yield to 305 DIM and for the complete lactation was increased. Fewer cows left the herd for health or reproductive problems in the extended VWP group. Waiting to initiate the supplementation of BST
until 4 wk after the first AI compared to initiating BST supplementation before the start of the breeding program resulted in better reproductive performance without compromising milk yield.
Impacts
Profitability of dairy operations might be enhanced by extending the voluntary waiting period beyond the commonly recommended length and by delaying the start of BST supplementation until after the cows have received their first breeding.
Publications
- Alejo,D.M. 2001. Effect of length of voluntary waiting period and time of initiation of rbST supplementation on reproduction and lactation. M.S. Thesis, University of Nebraska, Lincoln, 72 pp.
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Progress 10/01/99 to 09/30/00
Outputs
A trial was initiated to study the effect of length of voluntary waiting period and time of initiation of BST administration on reproductive and lactation performance. Holstein cows (n=160) will be blocked by pariety and assigned randomly by calving date to a 2x2 factorial arrangement of treatments. The two factors will be 1) voluntary waiting period (56 DIM or 112 DIM)and 2)time of first BST injection (3 d before first PGF or 4 wk after first AI). The breeding program will be initiated on the Monday after 56 or 112 DIM. Insemination will be by standard AI procedures. Cows will receive BST beginning the Friday before the start of the breeding program (3d before PGF) or 4 wk after the first AI and biweekly thereafter until 30 d before dry off. Estrous activity will be monitored utilizing an electronic pressure sensing system. Lactation, reproduction and health data will be collected. An economic comparison of the programs will be performed.
Impacts
Reproductive performance is a major problem in dairy cows with high milk production. The effect of time of initiation of BST administration relative to the start of the breeding program needs to be determined. The results could lead to a simple method to improve reproductive performance in dairy herds.
Publications
- Son,J.,Larson,L.L. and Grant,R.J. 2000. Effect of time of initiating dietary fat supplementation on performance and reproduction of early lactation dairy cows. Asian-Aus.J.Anim.Sci. 13:182-187.
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Progress 10/01/98 to 09/30/99
Outputs
The effect of time of initiating fat supplementation to diets on lactation and reproductive performance in dairy cows was evaluated. Forty-two Holstein cows (21 multiparous) were assigned by calving date and parity to one of three dietary sequences. The dietary sequences were: 1) control, no supplemental fat from 1 to 98 days-in-milk; 2) control diet from 1 to 28 days-in-milk then 3% supplemental fat (calcium salts of long-chain fatty acids) from 29 to 98 days-in-milk; or 3) 3% supplemental fat from 1 to 98 days-in-milk. Feeding supplemental fat did not enhance mean milk and 4% fat-corrected-milk yields, but efficiency of fat-corrected-milk production was higher for cows fed supplemental fat. Milk fat percentage was unchanged whereas milk protein percentage was depressed with fat supplementation. Feeding supplemental fat reduced dry matter intake and energy balance but there were no differences among treatments on time to resumption of ovarian cyclicity or conception
rate to first service. Concentrations of progesterone during the first two ovulatory cycles tended to be greater in the fat-supplemented groups. Feeding supplemental fat starting at either parturition or 29 days-in-milk increased efficiency of fat-corrected-milk production, but did not greatly enhance reproductive performance.
Impacts
Efficiency of fat-corrected-milk production and certain measures of reproductive performance can be enhanced by feeding supplemental fat to early lactation dairy cows. There appears to be little benefit from initiating the feeding of supplemental fat starting at parturition compared to starting at 29 days-in-milk.
Publications
- Chapman,W., Larson,L. and Grant,R. 1999. Effect of soyhull:soy lecithin:soapstock mixture on reproduction in early lactation dairy cows. Neb. Coop. Ext. MP74-A:3-4.
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Progress 10/01/97 to 09/30/98
Outputs
The effects of a soyhull:soy lecithin:soapstock mixture on long-term milk production and, reproductive parameters of the early postpartum dairy cow was evaluated. Thirty-seven Holstein cows were blocked by parity and assigned to one of two dietary treatments 1) control (no added lipid), or 2) soy lecithin and soapstock in a 1:1 ratio to supply 3% of dietary DM from 4 wk until 14 wk postpartum. Fat-corrected milk production, DMI and DMI as percentage of BW were increased by the incorporation of lipid into the diet. Milk fat and milk protein percentages were not affected by the supplementation of lecithin and soapstock; however, total kilograms of milk fat and protein were greater in the lipid-supplemented group. Cows supplemented with lipid were in more positive energy balance. There was no treatment effect on body weight, efficiency of milk production, or body condition score. There was no treatment effect on days to first ovulation postpartum. Serum concentrations of
progesterone during the luteal phase and the peak values following the first ovulation postpartum and following the timed insemination were not different between the two dietary groups. Supplementation with lipid did not influence conception rate to a timed artificial insemination protocol. Soy lecithin and soapstock had no effect on ruminal fiber fermentation. There is potential for soy lecithin and soapstock as an economical lipid source to increase energy density of the diet and improve performance of early lactation dairy cows.
Impacts
(N/A)
Publications
- Chapman, W.M. 1998. Effect of soyhull:soy lecithin:soapstock mixture on reproduction and production in early lactation dairy cows. M.S. Thesis, University of Nebraska, Lincoln, 95 pp.
- Chapman, W.M., Ward, J.C., Grant, R.J. and Larson, L.L. 1998. Effect of soyhull:soy lecithin:soapstock mixture on lactation performance in dairy cows. J. Anim. Sci. 76(Suppl. 1)/J. Dairy Sci. 81(Suppl. 1):261.
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Progress 10/01/96 to 09/30/97
Outputs
The response to selenium and vitamin E administration prepartum on placental retention and early lactation performance in dairy cows was evaluated. Holstein cows (n=253) calving over a 2-year period were assigned to: (1) control, no treatment; (2) Se bolus (release rate of 3 mg Se/d); (3) vitamin E (3000 IU); and (4) both Se and vitamin E. The Se bolus and vitamin E treatments were given 14 to 21 d prior to anticipated calving and a second vitamin E injection again on the day of calving. Supplemental Se and vitamin E alone and in combination did not affect the overall incidence of placental retention, 27.6%, or abnormal uterine discharges, 15.2%; but the percentage of live births was slightly lower in the Se only group (84.6% vs 95.2%). Milk yield, 33.9 kg/d, average somatic cell count, 337,000 and incidence of clinical mastitis, 22.6%, to 120 DIM were not affected by treatment. Some measures of rebreeding performance were improved in the Se + vitamin E compared to
the Se alone group, but neither group was different from the controls. These data indicate that Se and vitamin E supplementations were not beneficial under these conditions.
Impacts
(N/A)
Publications
- Chapman, W., Grant, R., Larson, L. 1997. A soyhull:soy lecithin:soapstock mixture for early lactation dairy cows. Neb. Coop.
- Larson, L.L., Chapman, W.M., Grant, R.J. 1997. Effect of selenium and vitamin E administration prepartum on placental retention and early lactation responses in dairy cattle. Annual Meeting ASAS/ADSA
- Son, J.H., Chapman, W., Grant, R., Larson, L. 1997. Time of initiating dietary fat supplementation on lactation and reproduction.
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