A. Ahmadzadeh

Effect of clinical mastitis and other diseases on reproductive performance of Holstein cows.

The objective of this study was to evaluate the effect of clinical mastitis and (or) other diseases on reproductive performance in lactating Holstein cows. Cows (n=967) from a commercial dairy farm were divided into four groups retrospectively: cows with clinical mastitis and other diseases (MD, n=54), clinical mastitis only (M, n=154), other diseases only (D, n=187), and cows with no record of clinical mastitis or other diseases (H, n=572). Days in milk at first service (DIMFS), services per conception (S/C), days not pregnant (DNP), the rate at which animals became pregnant over time and the proportion of cows that remained non-pregnant during 224 days of lactation were evaluated. Groups MD and M had greater (P<0.05) DNP compared with H (155+/-15 and 140+/-5 vs. 88+/-2, respectively). Moreover, MD and M had greater (P<0.05) S/C compared with H (3.0+/-0.4 and 2.1+/-0.1 vs. 1.6+/-0.1, respectively). The rate at which animals became pregnant over time was less (P<0.05) for MD and M and tended (P=0.1) to be less for D when compared with H. In addition, proportion of cows that remained non-pregnant by 224 days of lactation was greater (P<0.05) in MD, M, and D compared with H. Cows with mastitis were also divided into three groups according to the day of occurrence of the first case of clinical mastitis: (1) clinical mastitis occurred before 56 days postpartum (MP1); (2) clinical mastitis occurred between 56 and 105 days after parturition (MP2); and (3) clinical mastitis occurred after 105 days postpartum (MP3) Regardless of the time of occurrence, DNP was greater (P<0.05) for cows with mastitis compared with H. Time of mastitis occurrence affected S/C in that cows in MP2 and MP3 had a greater S/C compared with H cows (P<0.05). Reproductive efficiency was decreased by the presence of clinical mastitis alone because a greater proportion of cows with mastitis remained non-pregnant over time. Moreover, a greater proportion of cows with mastitis or diseases remained non-pregnant by 224 postpartum. Furthermore, the negative effects on reproduction were exacerbated when cows experienced both clinical mastitis and other diseases.

Effect of synchronization protocols on follicular development and estradiol and progesterone concentrations of dairy heifers.

The objectives were to evaluate the effect of synchronization protocols on follicular development and estradiol 17-beta (E(2)) and progesterone (P(4)) concentrations in dairy heifers. In experiment 1, 36 heifers were assigned to 1 of 6 synchronization protocols in a 3 x 2 factorial design: presynchronization with GnRH on study d -6 or -9 [study d 0 = initiation of the Cosynch + CIDR (controlled internal drug releasing insert containing P(4)) protocol] or no presynchronization (control) and one injection of PGF(2 alpha) or not on study d 0. In experiment 2, 126 heifers were assigned to 1 of 4 synchronization protocols in a 2 x 2 factorial arrangement: presynchronization or not with GnRH on study d -6 and injection of PGF(2 alpha) or not on study d 0. In experiments 1 and 2, all heifers received a modified Cosynch protocol with CIDR for 7 d starting on study d 0. After the PGF(2 alpha) of the Cosynch and removal of the CIDR, heifers were detected in estrus and inseminated. Those not inseminated by study d 10 received an injection of GnRH and were timed-inseminated. Ovaries were scanned by ultrasound on d 0, 2, and 5, daily from d 7 to 14, and on d 16. Blood samples collected on d 0, 2, 7, 9, and 16 were analyzed for P(4), and the blood sample collected on d 9 was analyzed for E(2). Pregnancy was diagnosed at 28 and 40 +/- 3 d after artificial insemination. In experiment 1, there was a tendency for the presynchronization protocol to affect the proportion of heifers ovulating in response to the first GnRH injection of the Cosynch + CIDR protocol. In experiment 2, a greater proportion of presynchronized heifers ovulated in response to the first GnRH injection. Although heifers receiving PGF(2 alpha) had larger ovulatory follicles on d 7 and before ovulation and shorter intervals to estrus and ovulation, these heifers tended to have decreased concentrations of E(2) during proestrus. Presynchronization of dairy heifers with GnRH increased ovulation in response to the first GnRH injection, and treatment of heifers with PGF(2 alpha) at initiation of the Cosynch + CIDR protocol increased the size of the ovulatory follicle and reduced the intervals to estrus and ovulation.

Effects of ultrasound-guided transvaginal follicular aspiration on oocyte recovery and hormonal profiles before and after gnrh treatment

Endocrine changes and recovered oocytes were evaluated during 16 wk of ultrasound-guided transvaginal follicular aspiration (TVFA) and prior to and following administration of GnRH at the cessation of aspiration. Nonlactating previously aspirated (PAC, n = 4) and non-aspirated, (AC, n = 4) Holstein cows were subjected to 16 wk of twice-weekly aspiration. Four control cows (OAC) were aspirated 1 time only at the final TVFA session (wk 16). Jugular blood samples were collected from all cows during aspiration, before and after the final TVFA session, and during an 18-d period following cessation of aspiration. Ovarian activity was monitored in all cows after cessation of aspiration for 18 d. The PAC and AC cows averaged 3.4 +/- 1.2 (+/- SE) and 6.8 +/- 1.2 oocytes per session, respectively. Progesterone concentrations during TVFA did not differ between the PAC and AC (0.8 +/- 0.1 and 0.9 +/- 0.1 ng/mL, respectively). Progesterone concentration in OAC was 4.5 +/- 0.2 ng/mL before TVFA, while the PAC and AC averaged 0.5 +/- 0.2 and 0.3 +/- 0.2 ng/mL, respectively, at 16 wk. At Week 16 LH was 1.0 +/- 0.2 ng/mL and it increased to 7.5 +/- 0.1 ng/mL after GnRH treatment. The LH concentration before the final aspiration session was higher at peak amplitude in PAC than in AC groups and peak length was longer in OAC than in AC cows (P < 0.07). Between 18 and 24 h after the last aspiration there were more LH peaks and greater peak frequencies in PAC than in OAC cows (P < 0.07), and the interval between peaks was longer in PAC and AC cows (P < 0.10) than in OAC cows. Mean FSH concentrations were lower (P < 0.01) for OAC than for PAC and AC groups at 20 and 24 h after the last aspiration. Follicle numbers after GnRH varied most among treatment groups for follicles < 9 mm, with the PAC, AC and OAC averaging 5.1 +/- 1.0, 5.1 +/- 1.0, and 3.8 +/- 1.0 follicles/d, respectively. Progesterone concentrations increased to 1.1 +/- 0.3 ng/mL in PAC cows and 2.5 +/- 0.3 and 3.4 +/- 0.3 ng/mL in AC and OAC groups, respectively, during the 18-d period. These results suggest that long-term TVFA affects progesterone, LH and FSH profiles and ovarian dynamics in cows.

Effect of Naloxone on Serum Luteinizing Hormone Concentration in Anovulatory Holstein Cows During the Early Postpartum Period

This experiment was conducted to investigate the effect of naloxone (NAL), an opioid receptor antagonist, on pituitary LH secretion in anovulatory Holstein cows during the early postpartum period when cows were expected to be in negative net energy balance. Twenty-three cows (11 primiparous) received either saline (n = 12) or 1 mg/kg BW NAL i.v. (n = 11) on Day 14 or 15 postpartum. Jugular blood samples were collected at 15-min intervals for 2 hr before and 2.5 hr after NAL or saline. All cows received 3 ug gonadotropin releasing hormone (GnRH) at 2.5 hr post-NAL or -saline and blood collection was continued for 1 hr. Mean serum progesterone concentration was 0.33 +/- 0.2 ng/ml. Mean net energy balance for all cows was -5.5 +/- 0.6 Mcal/day. Naloxone caused a transient increase (P < 0.05) in serum LH concentrations in both primi- and multiparous cows within 45 min after administration. In contrast, serum LH concentrations remained unchanged in saline-treated cows. GnRH increased (P < 0.05) LH and there was no effect of treatment. These results suggest that modulation of LH secretion, at least in part, may be mediated via endogenous opioids in dairy cows before first postpartum ovulation.

Fertility-associated antigen on Nelore bull sperm and reproductive outcomes following first-service fixed-time AI of Nelore cows and heifers

The objective was to determine whether the presence of fertility-associated antigen (FAA) on sperm collected from Nelore (Bos indicus) bulls can be used to assess potential fertility of sperm for use at first-service fixed-time AI (TAI). Six Nelore bulls were selected based on FAA status (FAA-negative: N = 3; FAA-positive: N = 3) and the ability to produce neat semen with ≥ 70% morphologically normal sperm and 60% estimated progressive motility before cryopreservation. In Experiment 1, suckled multiparous Nelore cows (N = 835) were evaluated for body condition score (BCS) and received an intravaginal progesterone device (CIDR) and 2.0 mg of estradiol benzoate (Day 0). On Day 9 the CIDR was removed, 12.5 mg of PGF(2α) and 0.5 mg of estradiol cypionate were administered, and calves were removed for 48 h. All cows received TAI on Day 11 (48 h after CIDR removal). Pregnancy per TAI (P/TAI) was not different between FAA-positive and FAA-negative bulls (41.5% vs. 39.3%, respectively). There was an effect of AI technician on P/TAI (36.0% vs. 43.9%; P < 0.05) and BCS tended to affect P/TAI (P = 0.09), as cows with BCS ≥ 2.75 were 1.4 times more likely to become pregnant compared with cows with BCS < 2.75. In Experiment 2, nulliparous Nelore heifers (N = 617) were evaluated for BCS and received a CIDR and estradiol benzoate (2.0 mg) on Day 0. On Day 7, all heifers received PGF(2α) (12.5 mg). On Day 9, CIDR inserts were removed and all heifers received estradiol cypionate (0.6 mg) and 200 IU eCG. All heifers received TAI on Day 11 (48 h after CIDR removal). Pregnancy/TAI was different (P = 0.04) between FAA-positive and FAA-negative bulls (33.7% vs. 40.7%, respectively). Presence of FAA on sperm was unsuccessful in assessing the potential fertility of sperm for use in TAI.

Evaluation of reproductive and economic outcomes of dairy heifers inseminated at induced estrus or at fixed time after a 5-day or 7-day progesterone insert-based ovulation synchronization protocol.

The objectives of the current experiment were to evaluate the reproductive performance and economic outcome of 3 synchronization strategies for first artificial insemination (AI) of dairy heifers. Holstein heifers from 2 herds (site A, California, n=415; site B, Idaho, n=425) were assigned to 1 of 3 treatments. Heifers assigned to the AI on estrus (AIE) treatment received an injection of 25mg of PGF(2α) at enrollment (d 0) and every 11 d thereafter until AI occurred. Heifers assigned to the CIDR5 treatment received a controlled internal drug release insert (CIDR) containing 1.38 g of progesterone, which was removed 5 d later concomitantly with an injection of 25mg of PGF(2α), and received fixed-time AI (TAI) concomitantly with an injection of 100 μg of GnRH 53 to 60 h later. Heifers assigned to the CIDR7 treatment received a CIDR insert, which was removed 7 d later concomitantly with an injection of 25mg of PGF(2α), and received TAI concomitantly with an injection of 100 μg of GnRH 53 to 60 h later. Heifers were observed for estrus and inseminated up to 98 and 73 d after enrollment in sites A and B, respectively. Thereafter, heifers were moved to pens with bulls and considered failure to conceive to AI if still not pregnant at the end of the observation period. Economic outcomes were based on cost of synchronization protocol (CIDR treatment=

Loss of body fat and associated decrease in leptin in early lactation are related to shorter duration of postpartum anovulation in healthy US women.

11, PGF(2α) or GnRH treatments=

Short communication: Characterization of early postpartum estrous behavior and ovulation in lactating dairy cows using radiotelemetry

2.5/treatment, estrous detection=

Effect of duration of progesterone-releasing device (controlled internal drug-release insert) treatment on reproductive performance in beef cows

0.80/heifer per day), rearing cost (

The Use of Gonadotropin-Releasing Hormone in a Progesterone-Based Timed Artificial Insemination Protocol in Replacement Beef Heifers

2.75/heifer per day), and economic loss if a heifer did not conceive to first AI (