Abstract
SUMMARY The artificial insemination (AI) by cervical retraction using fresh or commercially available frozen semen was evaluated. Santa Inês ewes (n=151) were assigned in five groups. Natural mating (NM) composed the control group. Four groups were submitted to hormonal treatment and timed insemination by cervical retraction (CRI) or laparoscopy (LAI), using fresh or frozen semen. To perform CRI, the ewes were kept in standing position. The time required to penetrate the cervical canal and to perform CRI were recorded; local deposition of semen and the reaction intensity of the ewe (weak, moderate or strong) were measured. Blood samples were collected to perform the progesterone dosage at days 0, 3, 5, 12 and 17 (day 0 = AI/NM). Non-return to estrus rate (NRE), pregnancy (at D35) and fertility (birth / mated ewes) were evaluated. Mean time for cervical penetration and CRI were 52.8 ± 21.2s and 3:26min ± 47s, respectively. Reaction intensity to CRI was weak or moderate in 92.3% of the ewes. Serum levels of progesterone after CRI, LAI or NM were similar. NRE of the inseminated ewes were similar, except for CRI with frozen semen, which was lower (P<0.05). Fertility rates were similar between CRI and LAI (35.4% and 42.2%, respectively). Artificial insemination by cervical retraction with ewes in a standing position is practical, and does not change the progesterone profile, providing reproductive rates similar to laparoscopy. However, the use of this technique along with commercial frozen semen presents low fertility rate.
Highlights
Productive characteristics of sheep farming, such as a short production cycle and exploitation in small areas, are required to meet the increasing demand for food
Our objective was to evaluate the feasibility of adapted Artificial insemination (AI) by cervical retraction (CRI) in Santa Inês ewes kept in a standing position by using fresh or commercially available frozen semen
For CRI, the ewes were kept in standing position by using a cattle crush with ventral supporting boards, and their hind limbs were immobilized with straps
Summary
Productive characteristics of sheep farming, such as a short production cycle and exploitation in small areas, are required to meet the increasing demand for food. Laparoscopic AI (LAI) increases fertility rates because it enables intrauterine deposition of semen This technique is difficult to apply commercially because of the high cost of the equipment, need for specialized professionals, and concern for the animals’ well-being (Cardoso et al, 2009). Halbert et al (1990) developed a transcervical AI method with a curvetipped probe and by restraining the ewe in a dorsal recumbency; this method is called the Guelph system of transcervical AI Because this technique may cause lesions on the cervix (Campbell et al, 1996), various adjustments to the transcervical method were investigated, as adjustments to conventional applicators include the use of cervical dilation drugs (Leethongdee et al, 2010; Álvarez et al, 2012). Our objective was to evaluate the feasibility of adapted AI by cervical retraction (CRI) in Santa Inês ewes kept in a standing position by using fresh or commercially available frozen semen
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