Intensity of estrus following an estradiol-progesterone-based ovulation synchronization protocol influences fertility outcomes

Abstract

The objective of this study was to examine the association between increased physical activity at the moment of timed artificial insemination (AI), detected by an automated activity monitor (AAM), and fertility outcomes. This paper also investigated factors affecting estrous expression in general. A total of 1,411 AI events from 1,040 lactating Holstein cows were recorded, averaging 1.3 ± 0.6 (±standard deviation) events per cow. Activity (measured as steps/h) was monitored continuously by a leg-mounted AAM located on the rear leg of the cow. Ovulation was synchronized by a timed AI protocol based on estradiol and progesterone. Ovarian ultrasonography was performed in all cows on d −11 (AI = d 0) and in a subset of cows on d 0 (n = 588) and d 7 (n = 819) to determine the presence of a corpus luteum and follicles. The body condition score (1 to 5 scale) was assessed on d 0 and a blood sample was collected for progesterone measurement on d 7. Using the AAM, an estrus event was determined when the relative increase (RI) in physical activity of the cow exceeded 100% of the baseline activity. The physical activity was classified as strong RI (≥300% RI), moderate RI (100-300% RI), or no estrus (<100% RI). Milk production was measured daily and averaged between d −11 and 0. Pregnancy was diagnosed at 32 and 60 d post-AI and pregnancy losses were calculated. The mean RI at estrus was 328.3 ± 132.1%. Cows with strong RI had greater pregnancy per AI than those with moderate RI and those that did not express estrus (35.1 vs. 27.3 vs. 6.2%). When including only cows that successfully ovulated after timed AI, those that displayed strong intensity RI still had greater pregnancy per AI than those with moderate intensity RI or those that did not express estrus (45.1 vs. 34.8 vs. 6.2%).Cows expressing strong RI at timed AI had greater ovulation rates compared with moderate RI and cows that did not express estrus (94.9 vs. 88.2 vs. 49.5%). Furthermore, pregnancy losses were reduced in cows with strong RI compared with cows expressing moderate RI (13.9 vs. 21.7%). Cows with a strong RI at estrus were more likely to have a corpus luteum at the beginning of the protocol and had greater concentration of progesterone 7 d post-AI. Multiparous cows expressed lower RI compared with primiparous cows. Cows with lower body condition score tended to have decreased RI at estrus. No correlation between estrous expression and pre-ovulatory follicle diameter was observed. Also, no correlation was observed between milk production at AI and RI. In conclusion, strong intensity RI of estrus events at timed AI was associated with improved ovulation rates and pregnancy per AI, and reduced pregnancy losses. These results provide further evidence that measurements of estrous expression can be used to predict fertility at the time of AI and possibly be used as a tool to assist decision making strategies of reproduction programs.

Effect of Body Condition Score at Calving on Ovarain Activity and Subsequent Reproductive Characteristics during Postpartum Period in Crossbred Cows تأثیر حالة الجسم عند الولادة على النشاط المبیضى والخصائص التناسلیة اثناء فترة مابعد الولادة فى الأبقار الخلیطة

“…Positive association has been observed in crossbred cows between progesterone concentrations at estrus and d7 post-mating and BCS level. According to the present finding, Madureira et al (2019) reported that lower concentrations of progesterone d 7 post-mating in cows with BCS <2.75 (2.5 ± 0.2 ng/ml) compared to cows with BCS ≥3.0 (3.2 ± 0.1 ng/ml) were found. Positive associations between post-mating and BCS concentrations of progesterone d 7 and the pregnancy rate in cows (Madureira et al, 2019).…”

“…According to the present finding, Madureira et al (2019) reported that lower concentrations of progesterone d 7 post-mating in cows with BCS <2.75 (2.5 ± 0.2 ng/ml) compared to cows with BCS ≥3.0 (3.2 ± 0.1 ng/ml) were found. Positive associations between post-mating and BCS concentrations of progesterone d 7 and the pregnancy rate in cows (Madureira et al, 2019). Spencer and Bazer (2002) stated that post-service progesterone concentrations were positively associated with cows conception rates maybe progesterone is vital for pregnancy maintenance.…”

Pregnancy Loss (28–110 Days of Pregnancy) in Holstein Cows: A Retrospective Study

“…Furthermore, Pereira et al [ 41 ] reported that the reduction in pregnancy loss in cows that expressed oestrus at AI occurred regardless of the diameter of the pre-ovulatory follicle and the hormonal protocol. Madureira et al [ 15 ] elucidated that the actual factor related to increased CR and decreased PL could be the intensity of oestrus expression, irrespective of the reproductive strategy implemented. In the present work, the type of AI with less PL pregnancies included those pregnancies after natural breeding, which may be the deffinitive factor, supporting the results of Madureira et al [ 15 ] because animals inducing bulls to mount and tolerating natural breeding express estrous adequately.…”

“…Madureira et al [ 15 ] elucidated that the actual factor related to increased CR and decreased PL could be the intensity of oestrus expression, irrespective of the reproductive strategy implemented. In the present work, the type of AI with less PL pregnancies included those pregnancies after natural breeding, which may be the deffinitive factor, supporting the results of Madureira et al [ 15 ] because animals inducing bulls to mount and tolerating natural breeding express estrous adequately. Moreover, the factor reproductive strategy which included all hormonal protocols and AI after observed oestrus, was not significantly associated with PL in the current study.…”

“…Progesterone level at AI and during the first days of pregnancy has also been related to PL [ 10 , 11 , 12 ]. Similarly, the serum concentration of pregnancy-associated glycorproteins (PAGs) [ 13 , 14 ] is correlated to PL probability; the intensity of oestrus at AI [ 12 , 15 ], season at AI [ 16 , 17 ], the protocol for timed AI (FTAI) [ 18 , 19 ], twin pregnancy [ 9 ], and ovulation number [ 12 ]. Some other factors were not associated with pregnancy loss, such as the rank of AI [ 16 ], extended lactation [ 20 ], calving-AI interval [ 16 ], corpus luteum, and uterine blood flow at first pregnancy diagnosis observed with ultrasonography [ 10 ].…”