Abstract
ABSTRACT The objective of this study was to compare the reproductive efficiency of dairy buffaloes undergoing fixed-time artificial insemination (FTAI) protocols based on progesterone/estrogen (P4/E2) and eCG during unfavorable breeding season using cooled (CS) and frozen semen (FS). A total of 446 buffaloes (> 40 days postpartum) were randomly distributed into four blocks (years): B1-2014 (n = 143), B2-2015 (n = 34), B3-2016 (n = 90), and B4-2017 (n = 179). Each block was subdivided into two (AI with CS and FS using the same ejaculate of each bull). Thus, the block subdivision was as follows: B1 (CS = 71 and FS = 72); B2 (CS = 18 and FS = 16); B3 (CS = 47 and FS = 43); and B4 (CS = 90 and FS = 89). The ejaculates of eight Murrah bulls collected using an artificial vagina were divided into two aliquots: one aliquot was diluted in Botu-Bov® commercial extender and cooled (BB-CS), and the other was diluted in the same extender and frozen (BB-FS). BB-CS aliquots were cooled at 5 °C/24 h using a refrigerator. BB-FS group aliquots were also cooled, and after equilibrating at 5 °C for 4 h, were placed in a 21-L Styrofoam box, 5 cm above the surface of liquid nitrogen. In the afternoon (A) on D0 (2:00 p.m.) the animals received EB 2.0 mg IM (Estrogin®) and an ear implant (CRESTAR® 3.0 mg P4). At D9 (A), the implant was removed, and the animals received eCG 400 IU IM (Folligon® 5000) + Cloprostenol PGF2α 0.530 mg IM (Sincrocio®). At D10 (A), the animals received EB 1.0 mg IM (Estrogin®), and at D12 (8:00 a.m.), AI was performed. At D42, pregnancy was diagnosed via ultrasonography. Total CRs were 48.2% CS and 34.6% FS for years 2014 to 2017, with a significant difference of 13.7% (P<0.05). In conclusion, cooled semen resulted in higher CR than frozen semen in dairy buffaloes under the P4/E2 and eCG FTAI during the unfavorable reproductive season.
Highlights
The population count of Brazilian buffalo species is estimated to be 1.434.141 (IBGE, 2019); only 1% of females of reproductive age are inseminated (IBGE, 2016)
Some studies have reported that fixed-time artificial insemination (FTAI) is a biotechnology that brings together the benefits of genetic improvement and reproductive management, as it allows a greater number of buffaloes to be artificially inseminated
The present findings show that buffalo females inseminated with cooled semen (CS) are 4.6-fold more likely to become pregnant presenting better quality and a less injured cells when chilling was used
Summary
The population count of Brazilian buffalo species is estimated to be 1.434.141 (IBGE, 2019); only 1% of females of reproductive age are inseminated (IBGE, 2016). Considering the aforementioned problems, some solutions have been proposed, such as the use of fixed-time artificial insemination (FTAI), which leads to the insemination of a large number of females on a predetermined day and time with no need for estrus observation and at the beginning of the breeding season, reducing the interval between calving and allowing the removal of females that have already undergone estrus at the end of the breeding season (Baruselli et al, 2004). It makes insemination possible during periods (spring and summer) that are unfavorable for natural reproduction (Carvalho et al, 2011)
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