José Carlos dos Santos Breda

Comparison between deep intracornual artificial insemination (dIAI) and conventional artificial insemination (AI) using low concentration of spermatozoa in beef cattle

This study aimed to compare the pregnancy rate using the conventional artificial insemination (AI) or deep intracornual artificial insemination (DIAI), with low number of spermatozoa (4.0 million sperm) in 270 Nelore cows. The animals were divided in two groups (G: G1 (135 cows) conventional AI was performed (=semen deposition in the uterine body) and in G2 (135 cows) to DIAI, in ipsilateral horn where the dominant follicle in the ovary had previously been detected, by ultrasound examinations. For both the methods, a single artificial insemination was carried out after visual estrus observation, checked three times a day (morning, afternoon and evening). The pregnancy diagnosis after 45 days was conducted by ultrasound. Results showed a better pregnancy rate in the DIAI group (67.4% - p<0.01), when compared to conventional AI (48.8%) with low spermatozoa concentration.

Estrus synchronization and Fixed Time Artificial Insemination (FTAI) in dairy buffaloes during seasonal anestrus

The aim of this work was to study estrus synchronization and fixed time artificial insemination (FTAI) in dairy buffaloes during season anestrus. One hundred thirty-nine dairy buffaloes in seasonal anestrus were divided in two groups as G1(n=66) and G2(n=73). The protocols for both the groups were the same until day (D)14:D0 administration of 2.0 mg estradiol benzoate and implantation of progesterone device (P4) for 14 days; D14 removal of P4 plus 150 mg of cloprostenol and 400 IU of equine chorionic gonadotropin. On D16, G1 received 10 mg of buserelin and G2 100 mg deslorelin acetate. On D17, both the groups were submitted to FTAI. Ultrasonographic examinations of ovaries were performed on D0, D14, D16 and D17. Results showed that pregnancy rates in G1 and G2 were 20 and 41% (p 0.05). Thirty-five percent of the animals in G1 and 54.1% in G2 showed a diameter DF greater than 8.0 mm on D16 (p>0.05). Thus, it could be concluded that the protocols synchronized the estrus, leading the concentration of the parturitions in the period of low milk production. Deslorelin was more efficient than buserelin due the higher percentage of DF ovulation and higher pregnancy rates.

Pregnancy and repeat breeding rate of high producing dairy cows for morning, evening or night artificial insemination

The study aimed (1) to verify if artificial insemination (AI), performed in the morning, evening or nighttimehas influence on the pregnancy rate on high production dairy cows, and (2) to determine the repeat breedingrate after the AI at intervals of 01-21, 22-43 and 44-65 days. We analyzed 1980 AI data from HolsteinFriesian cows from years 2004 to 2008. The average milk production on this period was 39 kg/milk/day/cow (305 days of lactation). The AI was performed 12 hours after the first detection of estrus. For the dataanalysis one AI was computed. The AI was done based on conventional method. The incidence of the AI in themorning, evening and night was 29.8; 50.4 and 19.8% respectively; and the pregnancy rate 45.7; 44.9 and48.4%. The frequency of the repeat breeding rate at the interval of 1-21 days on morning, evening and nightafter failed AI was 28.0; 22.3 and 19.8% respectively; at the interval of 22-43 days was 52.0; 52.2 and 55.2%,respectively and at interval of 44-65 days was respectively 20.0; 25.5 and 25.0%. Comparing the three timesof the day each other, the cows showed greater repeat breeding on 22-43 days (P<0.05) after the AI. It wasconcluded that times of the day has no influence on the on pregnancy rate; the highest repeat breeding ratetook place between 22 and 43 days after AI, resulting significant delaying of the open period.

Temporary Calf Removal and Equine Chorionic Gonadotropin (Ecg) Administration after Progesterone-Based Protocol Improves the Reproductive Performance of Beef Cattle

This study aimed to evaluate the effects of equine chorionic gonadotropin (eCG) administration and the temporary 48-h calf removal (CR) in a long-term progesterone (P4)based protocol in suckled Nelore cows. In all, 150 cows were randomly submitted to P4 protocol as follows. At day 0 (d 0), an intravaginal device containing 1.9 g P4 was inserted, and 1 mg estradiol benzoate (EB) was injected intramuscularly (im). On d 8, the P4 device was removed, and cows were im injected 500 µg of prostaglandin F group 2 alpha (PGF 2α ). On the same day, 75 cows (eCGCR group) received 400 IU im of eCG and were separated from their calves for 48 h. The other 75 cows (NoeCGCR group) stayed with the calves and did not receive eCG. On d 10, the calves were returned to the eCGCR group. After 8 days, all the cows were observed for estrus. The ovulatory follicle size was measured using ultrasonography at the day estrus was detected, and artificial insemination (AI) was performed 12 h later. Pregnancy was diagnosed 35 days after AI. The respective parameters for the eCGCR and NoeCGCR groups were as follows: pregnancy rate, 74.6% and 50.6% ( p 0.05). Thus, eCGCR after a long-term P4 protocol markedly improved pregnancy rates and estrus induction.