L. Vincenti

Assessment of an accelerometer system for detection of estrus and treatment with gonadotropin-releasing hormone at the time of insemination in lactating dairy cows

Two experiments were conducted to evaluate an accelerometer system (Heatime; SCR Engineers Ltd., Netanya, Israel) to manage reproduction in lactating dairy cows. In experiment 1, lactating Holstein cows (n=112) were fitted with an accelerometer system and were treated with GnRH followed 7d later by PGF(2α) to synchronize estrus. A total of 89 cows that had a follicle >10mm in diameter and a functional corpus luteum at the PGF(2α) injection that regressed by 48 h after induction of luteolysis were included in the analysis. Overall, 71% of cows were detected in estrus by the accelerometer system and 95% of cows showing estrus ovulated within 7d after induction of luteolysis. Of the cows not detected in estrus by the accelerometer system, 35% ovulated within 7d after induction of luteolysis. Duration of estrus activity (mean ± SD) was 16.1±4.7 h and was neither affected by parity nor milk production. Intervals (means ± SD) from induction of luteolysis, onset of activity, peak raw activity, and peak weighted activity to ovulation was 82.2±9.5, 28.7±8.1, 20.4±7.8, and 16.4±7.4 h, respectively, and the interval from AI to ovulation was 7.9±8.7 h, but ranged from -12 to 26 h. In experiment 2, cows were assigned randomly to receive an intramuscular injection of GnRH at artificial insemination (AI) after detection of estrus by the accelerometer system or receive no treatment (control). Nine hundred seventy-nine AI services from 461 cows were analyzed. Treatment with GnRH at AI did not affect fertility at 35 or 65 d after AI, and no interaction was detected between treatment and season or treatment and AI number. Overall, two-thirds of the cows that were considered properly synchronized were inseminated based on the accelerometer system and ovulated after AI. The remaining cows either were not inseminated because they were not detected in estrus or would not have had a chance to conceive to AI because they failed to ovulate after estrus. Furthermore, mean time of AI in relation to ovulation determined by the accelerometer system was acceptable for most of the cows that displayed estrus; however, variability in the duration of estrus and timing of AI in relation to ovulation could lead to poor fertility in some cows. For lactating dairy cows detected in estrus by the accelerometer system, treatment with GnRH at the time of AI without reference to the onset of estrus did not increase fertility.

Early lactation ratio of fat and protein percentage in milk is associated with health, milk production, and survival

An observational study was conducted on 1,498 cows in 3 large Italian dairy farms. The objective of the study was to evaluate the prognostic value of early lactation fat-to-protein ratio in milk. In all 3 herds, an intensive herd health monitoring program was being practiced that included weekly visits and extensive data collection on health, reproduction, production, and culling. A milk sample was collected from all cows at approximately 7 d postpartum and the ratio of fat-to-protein percentage in this milk sample was measured. Animals with a fat-to-protein ratio in early lactation greater than 2.0 showed an increase in postpartum diseases such as retained placenta, left-displaced abomasums, metritis and clinical endometritis. We also observed a decrease in early lactation milk production but this was limited to cows in lactation 2 and higher when the fat-to-protein ratio was greater than 2.0 in the early postpartum milk sample. Finally, an increased risk of being culled from the herd was observed, with the risk of culling increasing with increasing fat-to-protein ratio in the early lactation milk sample. No effect of fat-to-protein ratio was found on the incidence of clinical mastitis in the 3 herds. From this study, we conclude that analyses of milk components in early postpartum (6-9 days in milk), particularly the ratio of fat-to-protein percentage, is a valuable indicator of lipo-mobilization and the negative energy balance status in postpartum cows. Because a single milk sample is sufficient to provide valuable information, we suggest that this is a valuable addition to herd health programs on dairy farms.

Factors associated with pregnancy-associated glycoprotein (PAG) levels in plasma and milk of Holstein cows during early pregnancy and their effect on the accuracy of pregnancy diagnosis

Lactating Holstein cows (n = 141) were synchronized to receive their first timed artificial insemination (TAI). Blood and milk samples were collected 25 and 32 d after TAI, and pregnancy status was determined 32 d after TAI using transrectal ultrasonography. Cows diagnosed pregnant with singletons (n = 48) continued the experiment in which blood and milk samples were collected and pregnancy status was assessed weekly using transrectal ultrasonography from 39 to 102 d after TAI. Plasma and milk samples were assayed for pregnancy-associated glycoprotein (PAG) levels using commercial ELISA kits. Compared to ultrasonography, accuracy was 92% for the plasma PAG ELISA test and 89% for the milk PAG ELISA test 32 d after TAI. Plasma and milk PAG levels for pregnant cows increased from 25 d to an early peak 32 d after TAI. Plasma and milk PAG levels then decreased from 32 d after TAI to a nadir from 53 to 60 d after TAI for the plasma PAG assay and from 46 to 67 d after TAI for the milk PAG assay followed by an increase from 74 to 102 d after TAI. Overall, plasma PAG levels were approximately 2-fold greater compared with milk PAG levels, and primiparous cows had greater PAG levels in plasma and milk compared with multiparous cows. The incidence of pregnancy loss from 32 to 102 d after TAI based on ultrasonography was 13% for cows diagnosed with singleton pregnancies, and plasma and milk PAG levels decreased to nonpregnant levels within 7 to 14 d after pregnancy loss. Both plasma and milk PAG levels were negatively correlated with milk production for both primiparous and multiparous cows. We conclude that stage of gestation, parity, pregnancy loss, and milk production were associated with plasma and milk PAG levels after TAI similarly. Based on plasma and milk PAG profiles, the optimal time to conduct a first pregnancy diagnosis is around 32 d after AI, coinciding with an early peak in PAG levels. Because of the occurrence of pregnancy loss, all pregnant cows should be retested 74 d after AI or later when plasma and milk PAG levels in pregnant cows have rebounded from their nadir.

Postpartum uterine diseases and their impacts on conception and days open in dairy herds in Italy

The objective of this study was to describe the incidence and the impact of postpartum uterine diseases in postpartum cows on future uterine status and reproductive performance in large Italian dairy herds. This study provides an important quantitative estimate of uterine and postpartum diseases incidence that afflict high-producing Italian dairy cows. The total number of cows included in the study was 1498 on three farms; all cows were followed from the dry period until 300 days postpartum. All farms used high-quality data collection systems and standard operating procedures: weekly herd health visits, monthly Dairy Herd Improvement Association visits, and, due to cheese-making milk quality requirements, a supplementary milk sample collected at 7 ± 3 days postpartum evaluated for milk components. Clinical metritis in primiparous cows did not change the time to the first artificial insemination (AI) or days open; conversely, clinical metritis in multiparous cows had impact on the time to first AI (hazard ratio: 0.66, P < 0.01) and resulted in a lower conception rate at first insemination and a increase in days open (odds ratio: 0.64, P < 0.05). Clinical endometritis had a strong deleterious effect on first AI conception rate (odds ratio: 0.34, P < 0.05) and days open across all lactations (hazard ratio: 0.68, P < 0.05). Persistent metritis, defined as the presence of both clinical metritis and clinical endometritis in the same animal in the same lactation, caused low conception rate both in the first-lactation and in older cows and had a strong negative effect on the proportion of pregnant cows at 300 days (P < 0.05). In conclusion, the impact of endometritis on fertility was true across lactation groups. A good management and precocious diagnosis of the pathologies is not resolutive to restore good fertility parameters, and understanding the immune response in first-lactation cows may be of value for developing alternative intervention protocols for older-lactation cows.

Evaluation of Subclinical Endometritis and Consequences on Fertility in Piedmontese Beef Cows

Subclinical endometritis (SEM) is poorly investigated in beef cows, as stated in the literature. This project aims to evaluate the rate and the consequences of SEM in Piedmontese cows, with a focus on bacteriological findings and fertility parameters. Uterine cytology was performed for 97 subjects; a total of 31% of the cows were diagnosed as being positive for SEM and as having an 8% neutrophil (PMN) presence on the slide, which is considered as the best cut-off to diagnose the pathology. Only 13% of the cows positive for SEM were pregnant within 130 dpp and generally showed increases of 40 days in the partum to conception interval compared with the negative cows (142 vs 182, p = 0.01). Cows positive for both bacteriology and cytology showed a lower fertility than cows with only inflammation or only a bacterial presence (p = 0.0004). Bacterial isolation detected different species, but no difference in regard to the impact of these bacteria on SEM was shown. Parity, presence of calves, hygiene condition, age and number of service did not affect whether a cow was positive for subclinical endometritis (p < 0.05). The housing system (free stalls vs tie stalls) used seems to affect the SEM rate in Piedmontese cows; cows bred in tie stalls were more likely to be positive for SEM (OR = 2.2; p = 0.04). In conclusion, cytology seems to be a good technique for the diagnosis of subclinical endometritis in beef cows, and as in dairy cows, subclinical endometritis has a detrimental effect on fertility, causing an increase in partum to conception and a decrease in the rate of cows who become pregnant within 130 dpp, particularly for those cows housed in a tie stall.

Evaluation of equine oocyte developmental competence using polarized light microscopy

The purpose of this study was to observe in vitro-matured equine oocytes with an objective computerized technique that involves the use of a polarized light microscope (PLM) in addition to the subjective morphological evaluation obtained using a classic light microscope (LM). Equine cumulus-oocyte complexes (COCs, n = 922) were subjected to different in vitro maturation times (24, 36 or 45 h), however, only 36-h matured oocytes were analyzed using CLM. The 36-h matured oocytes that reached maturity were parthenogenetically activated to evaluate the quality and meiotic competence. Average maturation percentages per session in groups 1, 2 and 3 (24-, 36- and 45-h matured oocytes respectively) were 29.31 ± 13.85, 47.01 ± 9.90 and 36.62 ± 5.28%, whereas the average percentages of immature oocytes per session were 28.78 ± 20.17, 7.83 ± 5.51 and 22.36 ± 8.39% respectively. The zona pellucida (ZP) birefringent properties were estimated and correlated with activation outcome. ZP thickness and retardance of the inner layer of the zona pellucida (IL-ZP) were significantly increased in immature oocytes compared with mature oocytes (P < 0.001 and P < 0.01 respectively). The comparison between parthenogenetically activated and non-activated oocytes showed a significant increase in the area and thickness of the IL-ZP in parthenogenetically activated oocytes (P < 0.01). These results show that the 36-h in vitro maturation (IVM) protocol allowed equine oocytes to reach maturity, and PLM observation of ZP can be used to distinguish mature and immature oocytes as well as activated and non-activated oocytes.

Effects of equine chorionic gonadotrophin on follicular, luteal and conceptus development of non-lactating Bos indicus beef cows subjected to a progesterone plus estradiol-based timed artificial insemination protocol

The aim of this study was to evaluate the effects of equine chorionic gonadotropin (eCG) on ovarian follicular responses, corpus luteum (CL) development and conceptus length on day 16 after timed artificial insemination (TAI). A total of 124 cows at day 0 (D0) received 2 mg of estradiol benzoate (EB) and the insertion of a progesterone (P4) intravaginal device. Eight days later, the device was removed, and cows received 0.15 mg of prostaglandin and 0.5 mg of estradiol cypionate (EC), and were randomly assigned to 1 of 2 treatments: eCG (n=60), in which cows received 300 U of eCG; and control (n=64). Cows were TAI 48 h after P4 device removal. The diameter of the largest follicle (LF) present on D8 and D10 and of CL on D15 and D26 were measured. Conceptus recovered rate, conceptus length, CL diameter and weight were determined at slaughter on D26. Plasma P4 concentration was determined on D15 and D26. Follicular growth from D8 to D10 (P=0.03), the diameter of CL at D15 (P=0.03) and D26 (P=0.003) and the CL weight at day 26 (P=0.04) were greater in the eCG group than the control. However, there was no effect of eCG treatment on oestrus occurrence, conceptus recovery rate and length, or P4 concentrations on either D15 or D26. In conclusion, although eCG increases follicular responses and the diameter of the CL, this gonadotropin treatment does not influence the length of the conceptus or the P4 concentration on the subsequent oestrus cycle.

Mating-Dependent Endocrinological Variations in Female Camelus dromedarius

Abstract LH, oestrogens and progesterone levels were evaluated in four one-humped camels during oestrus to find evidence of induced ovulation. Different LH and progesterone patterns are shown between mated and non-mated females, confirming the role of mating in the ovulatory response in this species.