By Joseph C. Dalton, Ph.D., University of Idaho, Caldwell
The three largest expenses of a dairy business are feed costs for the lactating herd, labor, and raising replacement heifers, and feed is the major cost in raising replacement heifers, accounting for 45 to 64% of total costs in US dairy farms.
Dairy producers and heifer raisers must have a plan for getting heifers into the reproductive program. Growth (weight and wither or hip height) of heifers should be monitored regularly. Groups of heifers should be moved into the breeding pen weekly, as soon as target size is reached, regardless of age. If heifers gain weight faster than expected and attain the proper size for breeding earlier, breeding should not be delayed, as the heifers will likely become over-conditioned.
When developing heifers, the focus should be on age at conception, not age at first calving. A delay in age at conception will lead to a delay in age at first calving, along with increased rearing costs, primarily from extra days on feed, and lost income opportunity.
Synchronization programs for dairy heifers have been developed to facilitate timely reproduction and help dairy producers and heifer raisers attain their age at conception and age at first calving goals. The simplest program for dairy heifers includes administering a single injection of prostaglandin (PGF2α) on the day of breeding eligibility to synchronize estrus, and facilitate estrous detection and AI. Treatment of heifers not identified in estrus with a second dose of PGF2α 11 to 14 days after the first dose may cause those heifers to exhibit estrus. The discussion in this article will focus on two new reproductive strategies and economic outcomes.
Strategy #1: Pre-synchronization of dairy heifers with a 14-day CIDR protocol
Pre-synchronization is an effective management strategy applied during the voluntary wait period in lactating dairy cows to enhance pregnancy per AI (P/AI) to a timed AI (TAI) protocol, or facilitate AI following detection of estrus, shortly after breeding eligibility. Pre-synchronization of dairy heifers, however, is not often used to manage the immediate pre-breeding period. Nevertheless, pre-synchronization of heifers may be an effective strategy to accomplish first AI shortly after eligibility, and has the potential to decrease days on feed prior to first calving. In dairy heifers, 14-day CIDR (controlled internal drug release insert containing progesterone) treatment has been shown to be effective to synchronize ovulation.
The use of a CIDR insert for 14 days inhibits estrus and ovulation, and induces a persistent dominant follicle that can ovulate after CIDR removal. Ovulation of the dominant follicle results in a synchronized estrous cycle that can be used for pre-synchronization. In this scenario, PGF2α is injected 16 days after CIDR removal and followed by an injection of GnRH and TAI or AI upon detected estrus.
A 2015 study investigated pre-synchronization of dairy heifers, either with a 14 day CIDR or PGF2α, followed by PGF2α on the day of breeding eligibility and AI upon detected estrus, as compared to control heifers, which received no pre-synchronization, but PGF2α on the day of breeding eligibility and AI upon detected estrus. The objectives were to evaluate pregnancy per AI (P/AI), days to first AI, proportion of heifers pregnant within the first week of breeding eligibility, and economic outcomes of heifers subjected to pre-synchronization compared with control heifers.
Heifers and treatments: Following selection based on projected criteria on day of entry to AI pen (weight ≥ 860 lb., height at the withers ≥ 51 in, and age ≥ 12.5 mo.), 358 Holstein heifers were randomly assigned to one of three treatments:
- The 14-day CIDR-PGF2α group (n = 119) received a CIDR on day -30, which was removed on day -16. Immediately after CIDR removal, all heifers received an Estrotect patch to aid in estrous detection following CIDR removal. No heifers received AI at this time. The 14-day CIDR-PGF2α group received an injection of PGF2α upon entry to the breeding program (day 0).
- The 2X PGF2α group (n = 118) received an initial injection of PGF2α on day -11, and a second injection of PGF2α on day 0.
- The control (1X PGF2α) group (n = 121) received an injection of PGF2α on day 0.
All heifers received tail paint on day 0, were observed for behavioral estrus once daily, and received AI within 1 hour after detected estrus. Heifers were housed in dry lots with self-locking stanchions.
Strategy #1 results
Detection of estrus: Claypool et al. reported 96.7% of heifers were detected in estrus within 7 days after CIDR removal. Following PGF2α administration on day 0, 95.8% of heifers in the 14-day CIDR-PGF2α group were detected in estrus during the first week, as compared to 74.6% and 66.9% for the 2X PGF2α and control groups, respectively (Table 1).
Days to first AI and days to pregnancy: The same study found days to first AI following breeding eligibility were fewest for heifers in the 14-day CIDR-PGF2α group (3.6 days), intermediate for heifers in the 2X PGF2α group (5 days), and highest for heifers in the control group (6.8 days). Days from breeding eligibility to pregnancy were fewest for heifers in the 14-day CIDR-PGF2α group (15.1 days), as compared to heifers in the control group (25 days).
Pregnancy per AI (P/AI): Pregnancy per AI for first AI occurring during the first week of breeding eligibility were 71.9% (14 day CIDR-PGF2α), 58.0% (2X PGF2α), and 61.7% (control).
Proportion of heifers pregnant within first week of breeding eligibility: A greater proportion of heifers became pregnant within the first week of breeding eligibility in the 14-day CIDR-PGF2α group as compared to the 2X PGF2α and control groups (68.9 vs. 43.2% and 41.3%, respectively). There was no difference between 2X PGF2α and control groups.
Days on feed: There was a treatment effect for days on feed (DOF = day 0, date of breeding eligibility, to projected calving date). Days on feed, therefore, were calculated for pregnant heifers only, with 102/119, 104/118 and 112/121 in the 14-day CIDR-PGF2α, 2X PGF2α, and control groups, respectively. Days on feed were 295 days (14-day CIDR-PGF2α), 302 days (2X PGF2α), and 305 days (control), and were different between 14-day CIDR-PGF2α and control heifers, and tended to differ between 14-day CIDR-PGF2α and 2X PGF2α groups.
Strategy #1: Economic analysis
Claypool et al. (2016) developed a partial budget to describe the economic benefit of pre-synchronization of heifers (with a 14-day CIDR) relative to control heifers. No economic analyses were done between 14-day CIDR-PGF2α and 2X PGF2α groups, or between 2X PGF2α and the control group as these comparisons lacked statistical significance.
Expenses included were: PGF2α, per dose: $2.80; CIDR insert, per insert: $10.50; Labor was based on a wage of $15.00/hour. With two employees working together, the time required to complete a task, for example, identifying a heifer, loading the CIDR insertion device, addition of lubricant, insertion of the CIDR, trimming the exposed tail of the CIDR, identifying a heifer prior to removal of the CIDR, and removal of the CIDR, was estimated at 5 minutes per heifer. Feed costs at the collaborating facility were $2.35 per heifer per day during the experiment.
Due to fewer days on feed, the 14-day CIDR-PGF2α group had a reduced feed cost of $23.50 per animal, and decreased labor costs of $4.10 per animal, resulting in a total reduced cost of $27.60 per heifer compared with the control (Table 2).
There were, however, increased costs associated with the 14-day CIDR pre-synchronization treatment ($11.75 per heifer) as compared to the control, due to cost of the CIDR and increased labor ($10.50 + $1.25 = $11.75 per heifer). Subtraction of the treatment cost (cost of pre-synchronization) from the total reduced costs results in the treatment balance ($27.60 – $11.75 = $15.85), or the potential economic benefit to the producer. Pre-synchronization with the 14-day CIDR protocol resulted in an overall treatment balance of $15.85 per heifer. A potential limitation of the economic analysis, however, is the inclusion of pregnant heifers only in the economic analysis, as opposed to all heifers.
Strategy #1: Conclusions
Pre-synchronization of dairy heifers with a 14-day CIDR followed by a single injection of PGF2α on the day of entry to the AI pen appears to be an effective strategy to:
- Increase P/AI (first AI during the first week).
- Increase the proportion of pregnant heifers within the first week upon entry to the breeding program.
- Decrease days on feed.
- Provide an economic benefit to the producer.
Strategy #2: 5-day timed AI protocol
In 2010, Rabaglino et al. reported on the development of a 5-day timed AI (TAI) protocol for dairy heifers. Lima et al. in 2013 reported P/AI (first AI) of approximately 60% using a slightly modified version of the 5-day timed AI protocol (GnRH + CIDR IN-5d-CIDR OUT + PGF2α-24 h–PGF2α-48 h-GNRH + TAI).
Those researchers concluded that the use of GnRH at CIDR insertion requires two doses of PGF2α administered 24 hours apart to cause regression of a newly formed corpus luteum (CL), and that the P/AI of approximately 60% supports the use of the 5-day TAI protocol when estrous detection and AI is not used, as the results are similar to AI following estrous detection.
Neither of those studies were designed to compare TAI to AI after estrous detection. Consequently, Silva et al. (2015) investigated the reproductive performance and cost per pregnancy in dairy heifers following a 5-day TAI program as compared to AI following estrous detection.
Heifers and treatments: The researchers enrolled 611 Holstein heifers, approximately 400 days of age, in the study. On day -6 heifers were randomly assigned to either:
- A control group with 306 heifers, with AI after detected estrus from day 0 to 84. Control heifers not inseminated by day 7 received PGF2α, with treatment repeated every two weeks until AI.
- A timed AI (TAI) group of 305 heifers for first AI followed by AI after detected estrus for the remainder of the 84-d study. Heifers in the TAI group received GnRH and a CIDR insert on day −6, PGF2α and CIDR insert removal on day −1, PGF2α on day 0, and GnRH and TAI on day 2. Heifers in the TAI group detected in estrus the day before scheduled TAI received AI the same day. Estrus was detected daily starting on day 0. Heifers detected in estrus received AI on the same morning as detected estrus.
Duration of the study was 84 days to allow a breeding period equivalent to four 21-day estrous cycles.
Strategy #2 results
Days to first AI: Silva et al. (2015) reported days to first AI was approximately 8 days shorter for TAI heifers than for control heifers, at 1.7 days vs. 10.4 days respectively. (Table 3).
Pregnant at first AI: The same study reported the percentage of heifers pregnant, as determined 60 days after AI, did not differ between control heifers (58.3%) and TAI heifers (62.8%). Likewise, the percentage of heifers pregnant following AI with conventional semen was not different for control and TAI heifers (64.6 vs. 65.4%, respectively).
In contrast, there was an increased percentage of TAI heifers pregnant following AI with sexed semen as compared to control heifers (54.8% vs. 31.6% respectively).
Insemination rate and pregnancy rate: The 21-day insemination rate was greater for TAI than control heifers (91.4 vs. 82.4%, respectively), even when evaluated after the first 21 days of the study (TAI = 77.1% vs. control = 68.2). The increased insemination rate in the TAI group led to an improved 21-day pregnancy rate (57.2% vs. 47.9% for TAI and control heifers, respectively).
Days to pregnancy: The increased 21-day pregnancy rate of TAI heifers reduced the mean days to pregnancy by 10 days (18.9 d vs. 28.9 d for TAI and control heifers, respectively). Furthermore, the proportion of pregnant heifers was increased by 6.3 percentage points in the TAI group by the end of the 84-day study (91.5% vs. 85.2% for TAI and control heifers, respectively).
Strategy #2: Economic analysis
Silva et al. developed a partial budget to calculate the economic differences between the two reproductive programs. Briefly, expenses included hormones for synchronization of estrus or ovulation, labor, semen and AI supplies, pregnancy diagnosis, and feed. Costs used for GnRH and PGF2α were $2.00 per dose, while the CIDR insert was $8.00 per unit – but with two uses per insert (including the cost of cleaning and autoclaving) which resulted in a cost of $4.12 per insert. Labor was based on $10.00/hour. Cost of the 5-day TAI protocol was $12.87.
The researchers calculated the cost associated with extra days on feed in two ways: for heifers that became pregnant, and for heifers that never became pregnant. Considering first heifers that became pregnant, they used a calculated cost of approximately $2.11 per day ($0.17/kg dry matter (DM), with dry matter intake (DMI) of 13.0 kg/d) for each additional day. Secondly, they used a calculated cost of $1.80 per day (average value of TMR fed to breeding heifers: $0.20/kg DM, with DMI of 9.0 kg/d) for heifers that never became pregnant during the study.
Not surprisingly, whether the calculations were done on a cost per heifer or a cost per pregnancy basis, extra feed was the major factor to be considered. The cost per pregnancy was $17.00 less for TAI than control heifers.
Strategy #2: Conclusions
Implementation of a 5-day TAI protocol, beginning on day -6 before entry to the AI program (day 0), results in similar P/AI (first AI), reduces mean days to pregnancy, improves 21-day pregnancy rate, and reduces cost per pregnancy compared with AI after detected estrus.
Feed is the major cost in raising replacement heifers, accounting for 45 to 64% of total costs. When developing heifers, the focus should be on age at conception, not age at first calving. A delay in age at conception will lead to a delay in age at first calving, along with increased rearing costs, primarily from extra days on feed, and lost income opportunity.
Pre-synchronization of heifers with a 14-day CIDR protocol, followed 16 days later by a single injection of PGF2α on the day of AI eligibility, with AI upon detection of estrus, appears to be an effective strategy to generate pregnancies in a timely manner, with fewer days on feed ultimately resulting in an economic benefit to the producer. The 5-day TAI protocol results in fewer days to first AI, fewer days to pregnancy, less days on feed, and a cost per pregnancy $17.00 less than heifers that received AI following detection of estrus.