Anoestrous postpartum dairy cows: CIDR progesterone-insert programme vs no treatment — POSSIBLE

In postpartum dairy cows not detected in oestrus (anoestrous) before the seasonal breeding programme, how does a progesterone-insert (CIDR) programme compare with no treatment for resumption of oestrus/ovulation, time to conception and pregnancy rate?

Shelf #360 · gate-verified and approved by the developer

POSSIBLE: In the New Zealand seasonal system, progesterone-insert programmes for anoestrous cows buy earlier conception, not more pregnancies by season's end. The largest randomised test (McDougall 2010; 2,222 cows in 12 herds) found every programme shortened the interval from the first day of breeding to conception versus untreated controls — by 16 days for the insert-containing Ovsynch-56+P4 — with more cows showing normal luteal function, but no effect on the final pregnancy rate; McDougall 2003 shows the same shape for the programme's resynchrony component (Day 28 pregnancy 61.1% vs 54.5% in absolute terms, a relative increase of about 12%, with no Day 56 or final difference). The evidence is split by endpoint (positive on timing and early pregnancy, null on final pregnancy), so no 'no difference' suffix is attached. Anchor correction: the draft pointed to 'McDougall 2004'; the carded records are the 2010 randomised trial and the 2003 resynchrony trial — the direct standalone CIDR-plus-oestradiol vs no-treatment trial (McDougall & Compton 2005) could not be carded because its PubMed record could not be fetched and verified at drafting. Randomisation is established from the records for the 2010 trial ('randomly assigned') and for the 2003 resynchrony arms, while the 2003 prostaglandin arms used alternate assignment. Gaps: no carded trial measures the first-ovulation endpoint directly by ovarian scanning from Day 0; all carded evidence is from New Zealand pasture-based seasonal herds. Drafted Nov 10, 2026 (VetMed build, topic #360); all figures from abstracts fetched and verified at drafting.

McDougall 2010: progesterone-insert Ovsynch (Ovsynch-56+P4) shortened the interval to conception by 16 days vs untreated controls, but final pregnancy rate was unchanged (2,222 cows)

Randomised field trial (the abstract states cows 'were then randomly assigned to one of 4 treatments within each herd'); the record's only publication type is Research Support, Non-U.S. Gov't

Who: Cattle: 2,222 dairy cows from 12 New Zealand herds (pasture-based, seasonal breeding, field setting) that were not detected in oestrus by 9 days before the start of breeding, with the presence or absence of a corpus luteum determined by ultrasonography, randomly assigned within each herd to (1) Ovsynch (100 µg gonadorelin, 500 µg sodium cloprostenol 7 days later, 100 µg gonadorelin 54 to 56 hours after that, fixed-time AI 13 to 18 hours after the final GnRH), (2) Ovsynch-56+P4 (as (1) but with an intravaginal progesterone (P4)-releasing insert placed between the initial GnRH and PGF2α), (3) Cosynch-72+P4 (as (2) but with the final GnRH delayed until 71 hours after PGF2α and insert removal, with AI 0 to 5 hours after GnRH and AI of cows detected in oestrus before the second GnRH), or (4) untreated controls.

Result: All treatments resulted in shorter intervals from first day of breeding to conception compared with the controls. The Ovsynch-56+P4 treatment resulted in start of breeding to conception intervals 3, 6, and 16 d shorter than those of Cosynch-72+P4, Ovsynch, or controls, respectively, and the positive effect occurred both in corpus-luteum-positive and in corpus-luteum-negative cows. The Ovsynch-56+P4 treatment resulted in fewer short interestrus intervals than did Ovsynch (<18 d; 16 vs. 31%) and more cows with elevated (>1 ng/mL) milk P4 concentrations at d 7 (88 vs. 74%) and d 14 (80 vs. 60%). It was concluded that treatment of anestrous cows before the start of breeding resulted in earlier conception than no treatment but had no effect on the final pregnancy rate, and that addition of P4 to the Ovsynch program resulted in earlier conception and in more cows with normal subsequent luteal-phase lengths.

Watch out: The progesterone insert was tested as an add-on within GnRH/PGF2α timed-AI programmes, not as the classic standalone CIDR-plus-oestradiol anoestrus programme; the insert-vs-no-insert contrast (Ovsynch-56+P4 vs Ovsynch) is a 6-day difference in time to conception, and the 16-day figure is against wholly untreated controls. 'Anestrous' here means not detected in oestrus — the paper's introduction notes 10 to 30% of such cows have a corpus luteum.

McDougall S. Effects of treatment of anestrous dairy cows with gonadotropin-releasing hormone, prostaglandin, and progesterone. Journal of Dairy Science. 2010;93(5):1944-59. PMID: 20412908. Registry ID: none in the record. MeSH: Abortion, Veterinary · Anestrus/drug effects · Animals · Cattle · Dairying · Estrus/drug effects · Female · Fertilization/drug effects · Gonadotropin-Releasing Hormone/pharmacology · Hormones/pharmacology · Milk/chemistry · Pregnancy · Pregnancy Rate · Progesterone/pharmacology · Prostaglandins/analysis · Prostaglandins/pharmacology · Time Factors

McDougall 2003: resynchrony with a second CIDR raised the Day 28 pregnancy rate (61.1% vs 54.5%) but not Day 56 or final pregnancy rates; prostaglandin for CL-positive cows did nothing

Field trial with randomised and alternate assignment as stated in the abstract (resynchrony arms 'randomly assigned'; prostaglandin arms 'alternately assigned'); the record as fetched lists no publication types and no MeSH terms

Who: Cattle: New Zealand dairy cows not detected in oestrus by 1 week before the start of the seasonal breeding programme (field setting), categorised as anovulatory anoestrous (AA) or not detected in oestrus with a palpable corpus luteum (NDO/CL+), based on absence or presence of a palpable CL. All AA cows were treated with an intravaginal device containing 1.36 g progesterone (CIDR-B) for 6 days, and 1 mg oestradiol benzoate (ODB) by intramuscular injection 1 day after the device was removed (Day 0). Half the AA cows detected in oestrus between Days 0 and 3 were randomly assigned to resynchrony (reinsertion of a clean used CIDR-B device on Day 15 for 6 days, followed by 0.5 mg ODB 1 day after removal; 432 cows in the Day 28 pregnancy analysis) or no resynchrony (435 cows). NDO/CL+ cows were alternately assigned to 25 mg dinoprost tromethamine on Day 0 or untreated controls.

Result: Resynchrony increased the percentage of cows detected in oestrus between Days 14 and 28 (212/282 = 75.2% vs 155/285 = 54.4%, for RS vs no-RS respectively; p<0.001), but had no effect on conception rate to a service within the first 3 days of the mating period (146/397 = 36.8% vs 148/399 = 37.1%; p>0.9), or to a service between Days 14 and 28 (84/159 = 52.8% vs 114/217 = 52.5%; p>0.9). Resynchrony increased the Day 28 pregnancy rate (264/432 = 61.1% vs 237/435 = 54.5%, for RS vs no-RS respectively; p=0.03), but had no effect on the Day 56 or final pregnancy rates (p>0.1). Prostaglandin treatment of NDO/CL+ cows did not affect the percentage of cows detected in oestrus by Day 7 (43/106 = 40.6% vs 51/101 = 50.5%, for Con vs PG respectively; p=0.15), or Day 28 (92/106 = 86.8% vs 91/101 = 90.1%; p>0.4), nor the Day 28 pregnancy rate (55/103 = 53.4% vs 54/98 = 55.1%; p>0.9), the Day 56 pregnancy rate (81/103 = 78.6% vs 74/98 = 75.5%; p>0.6), or the final pregnancy rate (98/103 = 95.1% vs 89/97 = 91.8%; p>0.3).

Watch out: This trial does not compare the initial CIDR treatment with no treatment — every anoestrous cow received the first CIDR programme; the randomised contrast is the added resynchrony. The prostaglandin comparison is in cows with a corpus luteum (not truly anoestrous) and used alternate, not random, assignment. In relative terms the Day 28 pregnancy gain with resynchrony is about 12% relative (61.1% vs 54.5% absolute), and it washes out by Day 56.

McDougall S. Resynchrony of previously anoestrous cows and treatment of cows not detected in oestrus that had a palpable corpus luteum with prostaglandin F(2 alpha). New Zealand Veterinary Journal. 2003;51(3):117-24. PMID: 16032310. Registry ID: none in the record. MeSH: none listed in the record as fetched.

Synthesis: progesterone-insert programmes bring conception forward and normalise luteal function, but controls catch up — final pregnancy rate is unchanged

Synthesis

Who: Synthesis of the cards above: McDougall 2010 (2,222 cows not detected in oestrus in 12 herds, randomly assigned to Ovsynch, Ovsynch+progesterone insert, Cosynch+insert, or untreated controls) and McDougall 2003 (anoestrous cows all given an initial 6-day CIDR-B + oestradiol programme, then randomly assigned to CIDR resynchrony or none; CL-positive cows alternately assigned to prostaglandin or none) — both New Zealand seasonal, pasture-based field trials.

Result: (1) Progesterone-programme treatment reliably brings conception forward: the insert-containing Ovsynch-56+P4 shortened the start-of-breeding-to-conception interval by 16 days versus untreated controls (McDougall 2010), and adding CIDR resynchrony lifted the proportion pregnant by Day 28 from 54.5% to 61.1% (McDougall 2003). (2) It does not raise the final pregnancy rate in either trial — untreated or non-resynchronised controls catch up as the season progresses. (3) The insert also normalises what follows treatment: fewer short interestrus intervals (16% vs 31%) and more cows with elevated milk progesterone at days 7 and 14 than Ovsynch without an insert, i.e. more normal luteal phases.

Watch out: Neither carded trial is the classic head-to-head of a standalone CIDR-plus-oestradiol programme against wholly untreated anoestrous cows from Day 0: in McDougall 2010 the insert rides inside a timed-AI programme, and in McDougall 2003 every anoestrous cow had already received one CIDR course before the randomised contrast. Oestradiol benzoate, part of the classic programme, is no longer available in several jurisdictions — which is why the 2010 trial exists.

Synthesis of McDougall S. PMID: 20412908; McDougall S. PMID: 16032310. Registry IDs as on the individual cards.

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