Desempenho reprodutivo de �guas crioulas submetidas a controle reprodutivo ou monta a campo / Reproductive performance of pasture mated and hand mated Criollo Mares

RESUMO

O objetivo deste estudo foi comparar o desempenho reprodutivo de �guas manejadas com monta a campo com o de �guas submetidas a controle reprodutivo e monta controlada. Foram avaliados os dados reprodutivos de 433 �guas crioulas, com idades entre 4 e 28 anos, na temporada reprodutiva 2009-2010. Os animais apresentavam condi��o corporal ≥4(numa escala de 1 at� 5) e foram mantidos exclusivamente a campo em pastagens nativas melhoradas, sem suplementa��o. As �guas foram submetidas a dois sistemas de manejoG1- Monta a campo (202 �guas, alocadas em oito grupos compostos por um garanh�o e em m�dia 20,3 �guas (m�nimo oito e m�ximo 30 �guas), sendo realizado um �nico diagn�stico de gesta��o, 20 dias ap�s a retirada do garanh�o da manada); G2 � Controle reprodutivo(231 �guas foram examinadas, atrav�s de palpa��o retal e exame ultrassonogr�fico, sendo cobertas atrav�s de monta controlada quando apresentavam um fol�culo pr�-ovulat�rio (>35mm), associado a uma redu��o do grau de edema uterino. As coberturas eram feitas atrav�s de monta natural controlada, com as �guas contidas atrav�s de maneias. Todas as �guas receberam uma inje��o de 3000 UI de gonadotrofi na cori�nica humana (hCG)imediatamente ap�s a cobertura. O diagn�stico de gesta��o realizado no 14� dia ap�s a detec��o da ovula��o). Os dados foram comparados atrav�s do teste de qui-quadrado. Para a compara��o, dentro de cada grupo as �guas foram subdivididas em residentes tempor�rias e permanentes. As �guas manejadas atrav�s de controle reprodutivo apresentaram uma taxa maior de prenhez do que aquelas trabalhadas com monta a campo (G1=87,6%; G2=96,5%).Entre as residentes tempor�rias, a taxa de prenhez das �guas manejadas com monta a campo(G1=80%) foi menor (p=0,0002) do que a das �guas submetidas ao controle reprodutivo(G2=98,7%). Nas residentes permanentes, uma tend�ncia (p=0,06) a taxa de prenhez superior foi encontrada nas �guas submetidas ao controle reprodutivo (G1=89,8%; ...

ABSTRACT

The aim of this study was to compare the pregnancy rates of pasture bred and in-hand bred criollo mares. Data of a commercial herd consisting of 433 mares, 4 to 28 years old, body condition score ≥4 (crescent range from 1(thin) to 5 (obese)) and kept exclusively in native pasture without supplementation, in 2009/2010 breeding season, were evaluated. The effect of different reproductive managements was evaluated comparing pregnancy rates of the (G1) pasture breeding (202 mares) (G2) hand breeding (231 mares have been examined at maximal intervals of 48 hours, in order to evaluate follicular growth and grade of uterine edema. Both groups were composed of permanent and temporary mares. Mares in G2 have been bred when a pre-ovulatory follicle (>35mm) and low grade of uterine edema were found. All mares in this group received an injection of 3000 IU of human chorionic gonadotropin(hCG) immediately after breeding. A new examination was performed 36 to 48 hours after breeding to confirm ovulation). Pregnancy diagnosis was performed 14 days after ovulation (day 0) in G2 mares. In G1 mares, a single clinical and ultrasonography examination was performed at the end of breeding season. The data were compared by chi-square test and within each group the mares were sub-divided into permanent and temporary residents. A significant difference between G1 (87.6%) and G2 (96.5%) mares was observed (p=0.0005).In resident mares, a lower pregnancy rate (p=0.0002) was observed in pasture breeding (G1=80%) in comparison of hand breeding mares (G2=98.7%). A tendency (p=0.06) was observed in permanent mares (G1=89.8%; G2=97.4%). In pasture breeding, permanent mares tended (p=0.078) to present a higher pregnancy rate that temporary mares. In conclusion, hand breeding results in a higher pregnancy rate that pasture breeding when there is temporary mares on the herd