Effect of an inverse subtropical (19°13′N) photoperiod on ovarian activity, melatonin and prolactin secretion in Pelibuey ewes

Cerna, Corpus; Porras, A.; Valencia, Miguel; Perera, Gerardo; Zarco, L.

doi:10.1016/s0378-4320(00)00127-5

Cited by 18 publications

(16 citation statements)

References 24 publications

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“…No seasonal differences were observed in blood samples collected before (17:00 hr) or after (8:00 hr) the annual dusk and dawn times respectively (Table 3). These results are in agreement with those existing in the literature, which have demonstrated that all seasonal changes, which characterize the classic annual pattern of plasma melatonin concentration, occur during the nocturnal times [26,27,29,30].…”

Section: Discussionsupporting

confidence: 93%

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Annual pattern of plasma melatonin and progesterone concentrations in hair and wool ewe lambs kept under natural photoperiod at lower latitudes in the southern hemisphere

Coelho¹,

Rodrigues

Nonaka³

et al. 2006

Journal of Pineal Research

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To study the annual pattern of plasma melatonin and progesterone concentrations in hair [Santa Inês (SI)] and wool [Romney Marsh (RM) and Suffolk (SU)] ewe lambs kept under natural photoperiods at 21 degrees 59'S, 12 ewe lambs (four/breed) were used. For melatonin, blood samples were collected monthly throughout the year at the onset (17:00, 19:00 and 21:00 hr) and end (04:00, 06:00 and 08:00 hr) of the night, and for progesterone the samples were collected in the morning, two to three times a week throughout the year. Plasma melatonin concentrations at different times of the day changed according to the season. In diurnal periods (17:00 and 8:00 hr) no seasonal differences were observed but they became evident in the nocturnal intervals (21:00 and 4:00 hr) and transitional night-day (6:00 hr) times. The patterns of melatonin secretion were higher in winter and autumn than in spring and summer. The patterns of plasma progesterone secretion were affected by interaction between breed and season. There was no seasonal variation in plasma progesterone concentrations for SI females. The progesterone pattern for RM and SU females varied with season. The plasma levels were higher in autumn and winter than in spring and summer. At 21 degrees 59'S hair and wool ewe lambs showed the same annual pattern of plasma melatonin concentration while the annual progesterone profiles were quite different. For SI females this pattern was constant along all seasons and for RM and SU females this pattern was higher during autumn and winter than spring and summer.

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Section: Discussionsupporting

confidence: 93%

“…Ewes were judged to be in anovulation if plasma progesterone concentration never exceeded 1 ng/mL for more than two consecutive samples or during a 10-day period [17,33]. Other researchers consider the ovulatory activity when two or more consecutive blood samples show progesterone concentrations above 0.4-1 ng/mL [28,29,32,34].…”

Section: Discussionmentioning

confidence: 99%

Annual pattern of plasma melatonin and progesterone concentrations in hair and wool ewe lambs kept under natural photoperiod at lower latitudes in the southern hemisphere

Coelho¹,

Rodrigues

Nonaka³

et al. 2006

Journal of Pineal Research

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“…When some degree of seasonality of reproductive activity is evidenced, it is conditioned to other factors more important than photoperiod, such as rainfall, nutrition, air temperature and humidity (Gonzalez et al, 1992;Galina et al, 1996;Mbayahaga et al, 1998). More recently, Cerna et al, (2000) and Hernandez et al (2002) have suggested that the photoperiod would be the main regulator of the reproductive activity in hair sheep bred in the tropics. The present research seems to confirm this latter indication since during the shortest days there was a slight change in the reproductive pattern of Santa Inês ewe lambs, which was translated as a reduction in the number of periods of estrus in summer and a great number of silent ovulations in spring and summer.…”

Section: Resultsmentioning

confidence: 99%

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

Rodrigues

Coelho²,

Nonaka

et al. 2007

Sci. agric. (Piracicaba, Braz.)

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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...

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“…In contrast, the difference in minimum and maximum day length that occurs during the year at 18°37′ N (2 h and 16 min) could be thought to be too small to induce seasonality. However, Cerna et al (2000) demonstrated that this small variation in day length can evoke significant changes in Pelibuey sheep in the duration of melatonin secretion, strongly affecting the breeding season and prolactin profiles of some ewes. Furthermore, in a more recent study Chemineau et al (2004) proved that topical hair female sheep were sensitive to the photoperiod.…”

Section: Discussionmentioning

confidence: 99%

Seasonal variations in sexual behavior, testosterone, testicular size and semen characteristics, as affected by social dominance, of tropical hair rams (Ovis aries)

Aguirre¹,

Orihuela²,

Vázquez³

2007

Animal Science Journal

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The purpose of this study was to examine the effect of day length on seminal characteristics, testicular size, sexual behavior and testosterone concentration (T4) in dominant and subordinate Pelibuey rams. Six groups of three animals were evaluated every 2 weeks over a 12 month period. Dominant (D), medium (M) and subordinate (S) animals in each group were identified through a food competition test every 15 days. All rams ejaculated and produced semen throughout the year. A linear hierarchy was clearly established and maintained during the year. S rams had lower levels (P < 0.05) of semen volume, sperm concentration and testicular volume than D rams, regardless of season. Scrotal circumference was not influenced (P > 0.05) by their social position. D rams were more affected by the photoperiod, decreasing (P < 0.05) reaction times, increasing (P < 0.05) T4 and producing more (P < 0.05) sperm per ejaculation than S rams during short days (14.65 ± 1.22 vs 26.92 ± 1.65 s; 8.68 ± 0.44 vs 7.37 ± 0.40 ng/mL and 3.37 ± 0.17 vs 2.04 ± 0.16 sperm/109, respectively). Semen volume and sperm concentration were significantly (P < 0.05) greater during short days in all rams, regardless of their social status, with the exception of sperm concentration in D rams where no variation was found. M rams displayed variable values in the range between the D and S rams. It was concluded that the magnitude of the seasonal effects was not sufficient to prevent the rams being used for breeding throughout the year and that seasonal variation within the variables affected the social ranks differently.

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Effect of an inverse subtropical (19°13′N) photoperiod on ovarian activity, melatonin and prolactin secretion in Pelibuey ewes

Cited by 18 publications

References 24 publications

Annual pattern of plasma melatonin and progesterone concentrations in hair and wool ewe lambs kept under natural photoperiod at lower latitudes in the southern hemisphere

Annual pattern of plasma melatonin and progesterone concentrations in hair and wool ewe lambs kept under natural photoperiod at lower latitudes in the southern hemisphere

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

Seasonal variations in sexual behavior, testosterone, testicular size and semen characteristics, as affected by social dominance, of tropical hair rams (Ovis aries)

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