Annual characteristics of estrous activity in wool and hair ewe lambs under subtropical conditions

Abstract

The increased emphasis placed on lamb production in Brazil points to the need for a better knowledge of the annual pattern of reproductive activity in ewe lambs. This study evaluates the annual estrous activity pattern of hair and wool ewe lambs raised in southeast Brazil. Estrous characteristics were recorded for 12 months in ten Santa Inês and 21 Romney Marsh and Suffolk ewe lambs. Santa Inês ewe lambs exhibited a greater length of the normal estrous cycle (14 to 19 days) than Romney Marsh and Suffolk ewe lambs (17.0 ± 0.1 days vs. 16.5 ± 0.2 and 15.9 ± 0.2 days). All the ewe lambs presented a greater number of periods of estrus per animal per month for single estrous cycles (up to 26 days) during autumn and winter. During spring and summer there was a reduction of this number but this decline varied according to the breed. For Santa Inês ewe lambs the reduction was only significant in the summer. For wool ewe lambs the reduction was significant in both seasons but was more accentuated for Romney Marsh. The Romney Marsh ewe lambs had a more restricted breeding season than Suffolk and both presented optimal estrus activity in autumn and winter. Santa Inês ewe lambs had a continuous distribution of estrous cycles along the year, although presenting a reduction in the number of estrous periods in the summer. The ewe lambs of three breeds presented characteristics of sexual immaturity, like irregular estrous cycles and silent ovulations. Key words: breeds, estrous cycle, sheep, subtropics, seasonality CARACTERÍSTICAS ANUAIS DA ATIVIDADE ESTRAL EM BORREGAS LANADAS E DESLANADAS MANTIDAS SOB CONDIÇÃO SUBTROPICALRESUMO: Em função do maior interesse pela ovinocultura de corte na região Sudeste do Brasil há necessidade de conhecer melhor o padrão anual da atividade reprodutiva das borregas. Esse estudo avaliou esse padrão anual em borregas deslanadas e lanadas criadas nessa região. A atividade cíclica reprodutiva foi avaliada durante 12 meses em dez borregas da raça Santa Inês e 21 borregas das raças Romney Marsh (11) e Suffolk (10). A duração dos ciclos estrais normais (14 a 19 dias) das fêmeas Santa Inês foi maior do que a duração observada nas fêmeas Romney Marsh e Suffolk (17,0 ± 0,1 dias vs. 16,5 ± 0,2 e 15,9 ± 0,2 dias). Todas as borregas apresentaram um elevado número de períodos de estros/animal/mês para ciclos estrais simples (até 26 dias) durante o outono e inverno. Houve redução desse número durante a primavera e o verão, mas esse declínio variou conforme a raça. Para as borregas Santa Inês essa redução só foi significativa no verão enquanto que para as fêmeas das raças lanadas, a redução foi significativa em ambas as estações e mais acentuada nas fêmeas Romney Marsh. As fêmeas dessa raça também apresentaram uma estação reprodutiva mais restrita do que as fêmeas Suffolk havendo uma concentração dos estros durante o outono e inverno para as fêmeas de ambas as raças. As fêmeas Santa Inês apresentaram uma distribuição equilibrada dos estros ao longo do ano embora tenha havido uma redução do número de p...

Plasma Melatonin and Progesterone Profiles of Suffolk and Romney Marsh Ewes Implanted with Melatonin during Anoestrus Season at Lower Latitudes in Southern Hemisphere

“…It has been demonstrated that the efficacy of the ovulatory response to male effect varied according to the degree of reproductive seasonality of the ewe [31]. In our previous studies, it was indicated that the breeding season of Romney Marsh ewes was more restricted than the breeding season of Suffolk ones [7,29]. In the present study, it seems that no-implanted Suffolk ewes appear to have a slight anoestrus [31] and could respond to introduction of rams by increasing the plasma progesterone concentrations.…”

“…The ewes were 1.2 ± 0.9 years old and the mean live weights of Romney Marsh and Suffolk females were 43.3 ± 0.2 and 47.5 ± 0.8 kg, respectively. To induce male effect, 3 vasectomized adult rams of hair Santa Inês breed with no annual variation in breeding behavior [29], were used during the study. All the animals, previously vaccinated and dewormed, were confined in stalls and received feeding based on commercial ration, grass hay (Cynodon dactylon) cost-cross cultivar, twice a day, according to the nutritional requirements for sheep [24], and water ad libitum.…”

Reproductive efficiency of Pelibuey and Romanov × Pelibuey ewes synchronized with synthetic progesterone and low doses of PMSG under a hot environment

“…This adverse effect on the dominant follicle development reduces plasma concentrations of estradiol, LH, and inhibin. Thus, heat stress decreases the intensity and duration of estrus expressions and increases the incidence of anestrous and silent ovulations (Rodrigues et al, 2007). Some investigations have provided insight into potential means of mitigating the effects of heat stress on reproductive efficiency of sheep.…”

Onset of reproductive activity of white and natural colored corriedale ewe lambs

“…Progesterone Estrus Rodriguez et al (2007) monitored the annual estrus activity of Santa Ines, Rommey Marsh, and Suffolk sheep in Northern Brazil and observed that plasma P4 of Santa Ines sheep remained higher than 1ng ml -1 throughout the year, differently from the other breeds. The authors observed values higher than 1ng ml -1 from January in Rommey Marsh and Suffolk sheep, the former maintaining such concentration until August and the latter until October.…”