| Abstrakt: |
Urea supplementation in the diet of ruminants may alter the pH and protein concentration in different tissues and may affect the embryo quality and viability. Imbalances in nitrogen metabolism during the periods of oocyte growth and/or fertilization may dispose the zygote, pre-implantation embryo, and surviving conceptus to developmental errors. The aim of this research was to investigate the effect of feeding urea to goats on embryo quality. Eighteen Toggenburg goats, 48.6 ± 7.9 kg of BW, 2.9 ± 0.5 BCS, and 34.3 ± 20.8 months of age, were allocated randomly to 2 treatments: T1 (control, n= 8): no urea, and T2 (n= 10): 2.4% of dry matter (DM) as urea in the diet. The animals were fed diets based on Coast-cross hay (Cynodon dactylon) and concentrate (14% crude protein, DM basis) for 42 ± 2 days before embryo flushing. Estrus was synchronized with intravaginal sponges impregnated with 60 mg of medroxyprogesterone acetate (Progespon®, Syntex S.A., Buenos Aires, Argentina) for 11 days plus i.m. injection of 100 μg of cloprostenol (Ciosin®, Schering-Plough, Cotia, Brazil), on the Day 9. The superovulation protocol consisted of i.m. injections of 200 mg equivalent of NIH-FSH-P-1 (Folltropin®, Bioniche, Athens, GA), in 6 decreasing doses at 12-h intervals, on Days 9, 10, and 11 (Day 0 = sponge insertion). Estrus was monitored twice a day for 30 min from sponge withdrawal by use of teaser bucks, and females were mated by fertile bucks every 12 h during standing estrus. Early luteal regression was preventing by administration of an antiluteolytic (Banamine®, Schering-Plough) 72 h after sponge withdrawal, 1.1 mg kg-1per day i.m. for 3 days. Embryo recovery was done on the seventh day of estrous cycle by a transcervical technique. Recovered embryos were classified by quality (I = excellent, V = degenerated), development stage percent (1 = unfertilized oocytes, 9 = hatched blastocyst), and viability with the embryo grades 1 (excellent), 2 (good), and 3 (fair). The effect of urea supplementation on embryo stage and viability was analyzed by ANOVA. From the 18 goats, 12 (67%) were responsive to the superovulation protocol, 62.5% from T1 and 70.0% from T2. The number of embryos flushed (7.20 ± 2.39 v. 6.29 ± 2.93) and the percentage and number of viable embryos [100% (36/36) v. 100% (39/39)] from T1 and T2 were not different (P> 0.01). Thereafter, embryos in advanced stages of development (7, 8, and 9) were 58.65% from T2 compared with 0% from T1 (P< 0.01). In addition to the embryos, 13 unfertilized oocytes were recovered from the T2 goats v. none from the T1 goats (P< 0.01). These results suggest that urea may cause acceleration of embryo development and may affect oocyte fertilization.Supported by grants from CNPq, FAPEMIG, CAPES, Schering Plough®, Tecnopec®, and Carbogel®. [ABSTRACT FROM AUTHOR] |
