Regulation of Breeding Season and Estrous Cycles by Light and External Stimuli in some Mammals

1966 ◽  
Vol 25 (suppl) ◽  
pp. 119-139 ◽  
Author(s):  
C. Thibault ◽  
M. Courot ◽  
Lise Martinet ◽  
P. Mauleon ◽  
F. du Mesnil du Buisson ◽  
...  
Keyword(s):  
Breeding Season ◽  
Estrous Cycles ◽  
External Stimuli

THE DURATION OF THE BREEDING SEASON OF FOUR BREEDS OF SHEEP

1974 ◽  
Vol 54 (3) ◽  
pp. 389-392 ◽  
Author(s):  
J. J. DUFOUR
Keyword(s):  
Sexual Activity ◽  
Breeding Season ◽  
Estrous Cycles ◽  
Progressive Decline ◽  
Daily Exposure ◽  
Almost All

Three breeds of sheep (Dorset, Leicester, and Suffolk) and a crossbred line from these breeds (DLS) were observed throughout 1 yr to determine their sexual activity by daily exposure of the ewes to vasectomized rams. The DLS and Dorset ewes exhibited their first estrus earlier in the year (P < 0.01) and stopped cycling later than the Leicester and Suffolk ewes (P < 0.01). The duration of the breeding season in the DLS ewes was 20 days (P > 0.05) longer than in the Dorsets and 70 and 115 days (P < 0.01) longer than in the Leicester and Suffolk ewes, respectively. The percentage of Dorset and DLS ewes showing one or more estrous periods increased progressively from June to reach 100% in September for both breeds. The Suffolk and Leicester ewes commenced to cycle in late August and by September almost all ewes had shown an estrous period. The progressive decline in estrous activity became evident first with the Suffolk in January, then with the Dorset and Leicester in February and with the DLS in March. The Dorset, DLS and Leicester ewes had longer estrous cycles than the Suffolk ewes. Within ewes, length of estrous cycles was highly repeatable for all breeds. False estrus and silent estrus occurred in 1.0 and 3.9% of the estrous periods, respectively. Over successive estrous cycles, length of estrous cycles increased significantly.

AN INVESTIGATION OF THE REFRACTORY PERIOD OF REPRODUCTION IN MALE BIRDS BY MEANS OF EXOGENOUS PROLACTIN AND FOLLICLE STIMULATING HORMONE

1958 ◽  
Vol 17 (1) ◽  
pp. 91-NP ◽  
Author(s):  
B. LOFTS ◽  
A. J. MARSHALL
Keyword(s):  
Breeding Season ◽  
Wild Species ◽  
Refractory Period ◽  
Anterior Pituitary ◽  
Neural Control ◽  
Follicle Stimulating Hormone ◽  
And Migration ◽  
Breeding Seasons ◽  
External Stimuli ◽  
Stimulating Hormone

SUMMARY At the end of the breeding season wild birds become refractory to photostimulation, and at the same time there is cessation of spermatogenesis, production of cholesterol-positive tubular lipids, tubular collapse and an overall reduction in size of the testis. These natural events can be duplicated by hypophysectomy or prolactin injection. Just before the onset of such changes the males of at least some wild species produce prolactin. It is shown in pigeons that exogenous prolactin is probably without direct effect on the avian testis, operating merely by inhibiting adenohypophysial activity. However, since in pluralbrooded wild species such collapse is delayed until the last clutch of the season has been fertilized and the males of some of these also brood the eggs, it seems likely that, in nature, prolactin can only temporarily depress, and not inhibit, the output of gonadotrophin. The seasonal inhibition of adenohypophysial function, and the resultant metamorphosis of the testis, is probably essentially under neural control with external stimuli ultimately involved. As regards the termination of the refractory period, it is demonstrated that very small quantities (0·6 i.u.) of exogenous follicle stimulating hormone will clear the tubules of experimentally produced (by hypophysectomy) 'post-nuptial' lipids and cholesterol almost immediately after their appearance. This is interpreted as confirmatory evidence that it is the anterior pituitary, and not the testis, that becomes seasonally refractory. The time taken for the rhythmical annual recovery of adenohypophysial function is probably one of the most important events in the regulation of avian breeding seasons and migration.

224 OVARIAN FOLLICLE DEVELOPMENT DURING SEASONAL TRANSITION IN WAPITI

2006 ◽  
Vol 18 (2) ◽  
pp. 220
Author(s):  
R. McCorkell ◽  
M. Woodbury ◽  
G. Adams
Keyword(s):  
Breeding Season ◽  
Ovarian Follicle ◽  
Follicular Development ◽  
Maximum Diameter ◽  
Follicle Development ◽  
Estrous Cycles ◽  
Ovarian Follicle Development ◽  
Array Transducer ◽  
October 17 ◽  
Ovulatory Follicles

Wapiti are seasonally polyestrous. The transition into and out of the breeding season is marked by resumption of ovulation in autumn and cessation of ovulation in winter. Onset of ovulatory cyclicity is distinct and associated with aggressive breeding behavior of stags in rut. Cessation of ovulation at the end of the breeding season is not distinguished by behavioral patterns. The objective of the present study was to characterize follicular and luteal dynamics in wapiti during the transitional periods into and out of the breeding seasons. Transition from anestrus to estrus was monitored in 15 hinds, aged 2 to 14 years, over two successive seasons (11 in year 1, with 5 hinds from year 1 used again in year 2 along with 4 new hinds; n = 20 observations). Transition from estrus to anestrus was monitored in 11 hinds over 1 season (n = 11 observations). Hinds were maintained on a farm near Saskatoon, Saskatchewan (52°07′N, 106°38′W). The ovaries were examined daily during September through October by transrectral ultrasonography using a B-mode ultrasound machine and a 7.5 MHz linear array transducer for transition to estrus, and December through April for transition to anestrus. The first ovulation was recorded on September 15 and all hinds had ovulated for the first time by October 7. In 17 of 20 observations, the duration of the first interovulatory interval (IOI) was 9.3 ± 0.4 days (mean ± SEM). With one exception, these IOIs were characterized by one wave of follicular development. The remaining three IOIs ranged from 16 to 23 days and consisted of two or three waves of follicle development. The second ovulation occurred by October 15 in hinds with a short IOI and by October 17 in all remaining hinds. The mean dates of first and last ovulation were September 25 and February 7, respectively, an interval of 135 days. The median date of the last ovulation was February 15 and the range was from December 3 to March 22. Duration of the last IOI of the season (21.2 ± 0.6 days) was similar to the notional 21-day cycle for wapiti, but longer (P < 0.05) than the duration of the first IOI (10.9 ± 1.0 days). Maximum diameters of the first 2 ovulatory follicles were similar (11.3 ± 0.4 vs. 11.3 ± 0.2 mm), but were larger (P < 0.05) than the last 2 ovulatory follicles of the breeding season (10.3 ± 0.3 vs. 10.1 ± 0.4 mm). Maximum diameter of the corpus luteum (CL) tended (P = 0.06) to be smaller for the short IOI than for longer IOI of the first and last cycles. Diameter of the last CL of the season was not different from that of the previous CL (12.8 ± 0.6 vs. 12.5 ± 0.6 mm); however, it was detected for a longer period (22.3 ± 1.2 vs. 19.3 ± 0.7 days; P < 0.05). Estrous cycles during transition into the breeding season have been described as being irregular and those out of the breeding season as increasingly long. In the present study, the transition periods were characterized by regular events. Transition to regular estrous cycles was preceded by one short (9 days) IOI. The last IOI of the breeding season was the same as that reported during the rut. Transition to anestrus occurred most commonly in February and was marked by a failure of the dominant follicle to ovulate after luteal regression.

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

2007 ◽  
Vol 64 (5) ◽  
pp. 468-475 ◽  
Author(s):  
Paula de Almeida Rodrigues ◽  
Lia de Alencar Coelho ◽  
Keico Okino Nonaka ◽  
Aya Sasa ◽  
Wilter Ricardo Russiano Vicente ◽  
...  
Keyword(s):  
Estrous Cycle ◽  
Breeding Season ◽  
Activity Pattern ◽  
Continuous Distribution ◽  
Reproductive Activity ◽  
Estrous Cycles ◽  
Southeast Brazil ◽  
Ewe Lambs ◽  
Santa Inês ◽  
Autumn And Winter

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.

Observation on the breeding biology of Polypedates teraiensis (Dubois, 1987) (Amphibia: Rhacophoridae)

2017 ◽  
Vol 17 (1) ◽  
pp. 25-32
Author(s):  
Jacinta Lalchhanhimi ◽  
Lalremsanga H.T.
Keyword(s):  
Sexual Dimorphism ◽  
Breeding Season ◽  
Sound Production ◽  
Reproductive Function ◽  
Breeding Biology ◽  
Tree Frog ◽  
University Campus ◽  
Morphometric Measurements ◽  
Advertisement Calls ◽  
Males And Females

The breeding biology of tree frog, Polypedates teraiensis was studied during the breeding season at Mizoram University Campus. It was found that sound production by male during the breeding season was primarily a reproductive function and advertisement calls attract females to the breeding areas and announce other males that a given territory is occupied. The aim of this study was to provide the detailed information on the breeding behaviour and the advertisement calls of Polypedates teraiensis. The morphometric measurements of the amplecting pairs (males and females) for sexual dimorphism along with clutch sizes were also studied.

Catastrophe Theory in Explaining Price Dynamics on the Real Estate Market

2013 ◽  
Vol 21 (3) ◽  
pp. 51-61 ◽  
Author(s):  
Mirosław Belej
Keyword(s):  
Real Estate ◽  
Catastrophe Theory ◽  
Open Systems ◽  
Real Estate Market ◽  
Sensitivity Threshold ◽  
State Variables ◽  
The Real ◽  
The Real Estate ◽  
The Real Estate Market ◽  
External Stimuli

Abstract The real estate market is an open system, which implies that it is able to exchange signals with other open systems and dynamic systems. The evolution of a market system over time can be described mathematically. If the system's sensitivity threshold to external stimuli is exceeded, it becomes destabilized and moves from a near-balanced state to a state that is far from equilibrium. Those dynamic processes often induce key changes in the system's trajectory of evolution. In search of equilibrium, the system becomes transformed in a process of discontinuous and discrete changes in state variables. The above statement constitutes the research hypothesis in this article. In this study, an attempt was made to develop a mathematical model for visualizing the evolutionary path of the real estate market in the form of continuous changes interrupted by discontinuous changes. The qualitative transformation of the system will be evaluated with the use of the catastrophe theory.

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