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.

A note on attainment of puberty of september-born early-maturing ewe lambs in relation to level of nutrition

1991 ◽  
Vol 53 (3) ◽  
pp. 407-409 ◽  
Author(s):  
F. Forcada ◽  
J. A. Abecia ◽  
L. Zarazaga
Keyword(s):  
Sexual Activity ◽  
Breeding Season ◽  
Ovulation Rate ◽  
Corpora Lutea ◽  
Plasma Progesterone ◽  
Ewe Lambs ◽  
Early Maturing ◽  
Age At Puberty

The attainment of puberty in September-born early-maturing ewe lambs was studied at Zaragoza (latitude 41° 40' N). Thirty twin Salz females were allocated to two groups receiving two nutrition levels after 3 months of age: high (500 g/day lucerne hay and 500 g/day concentrate) (H) and low (500 g/ day lucerne hay) (L). Oestrus was detected daily by aproned rams. Corpora lutea were counted after oestrus and plasma progesterone levels monitored each week.In the first breeding season (January to February) the percentage of females showing sexual activity (silent emulation or oestrus and ovulation) was higher in the H compared with the L group (67 and 20%; P < 0/05). Nonpubertal oestrus before the main breeding season was detected in 67% of animals. In the main breeding season and for H and L groups respectively, percentage of females showing silent ovulation before puberty was 67 and 33% and mean age at puberty extended to 319 (s.e. 4-8) and 314 (s.e. 3·7) days. Ovulation rate at puberty was 1·73 (s.e. 0·13) and 1·33 (s.e. 0·15) respectively (P < 0·05).

Peripheral androgen levels in the male brush-tail possum (Trichosurus vulpecula)

1985 ◽  
Vol 105 (1) ◽  
pp. 63-70 ◽  
Author(s):  
J. D. Curlewis ◽  
G. M. Stone
Keyword(s):  
Breeding Season ◽  
Sampling Period ◽  
Sampling Procedure ◽  
Seasonal Effect ◽  
Poor Correlation ◽  
Time Intervals ◽  
Progressive Decline ◽  
Collection Period ◽  
Initial Blood ◽  
Androgen Levels

ABSTRACT Radioimmunoassays were established for the measurement of total androgens and the specific measurement of testosterone and 5α-dihydrotestosterone in peripheral plasma of the brush-tail possum. Androgen concentrations were measured in blood collected from indwelling jugular cannulae (i) to determine whether the normal pattern of androgen secretion in this species was episodic and (ii) to attempt to relate total androgen and the pattern of testosterone secretion to the changes previously reported in prostatic, but not epididymal, weight in the breeding season. Blood was collected from restrained animals at varying time-intervals during daylight hours and darkness. Despite an apparent good adaptation to the sampling procedure there was generally a progressive decline in plasma androgen level during the collection period. This was true for animals bled during or out of the breeding season. There was no significant seasonal effect on the androgen concentration in the initial blood sample. When less restraint was used, two of three animals showed fluctuations in androgen levels over the 7-h sampling period. Testosterone levels in blood obtained by cardiac puncture were four- to nine-fold higher than those of 5α-dihydrotestosterone but levels of these androgens in samples obtained during the breeding season were not significantly different from those obtained out of season. The results do not argue for a pulsatile release of testosterone in the possum but do demonstrate a marked capacity for changes in the peripheral androgen concentration. There was a poor correlation between testosterone and 5α-dihydrotestosterone levels and prostatic weight. J. Endocr. (1985) 105, 63–70

scholarly journals The annual cycle of the White-ruffed ManakinCorapipo leucorrhoa, a tropical frugivorous altitudinal migrant, and its food plants

1994 ◽  
Vol 4 (2-3) ◽  
pp. 143-160 ◽  
Author(s):  
Loreta Rosselli
Keyword(s):  
Breeding Season ◽  
Annual Variation ◽  
Subcutaneous Fat ◽  
Food Plants ◽  
Forest Site ◽  
Fruit Species ◽  
Altitudinal Migration ◽  
Tentative Evidence ◽  
Moult Period ◽  
Almost All

SummaryFrugivorous White-ruffed ManakinsCorapipo leucorrhoa(Pipridae) showed pro nounced seasonal emigration from a pre-montane wet forest site (550 m) on the Atlantic slope of Costa Rica. “Resident” breeders left the area between August and October, and returned between February and April, at the onset of the breeding season. Female patterns differed from those of males primarily in later departure (October) and later return (April). I documented 57 fruit species in the diet at this locality and monitored phenology for 43 of those species, many of which were understorey members of the Melastomataceae. The emigration did not coincide with a period of local fruit shortage (relative to abundance at the same locality in other months), but the relative abundance and species composition of fruit resources in the areas to which the manakins migrated remains unknown. However, peak resources did coincide with the period in which recent fledglings would be commonest and the period during which most individuals were moulting prior ot emigration. Resources were lowest from November, when residents were absent, untilJune, well into the breeding season. Tentative evidence suggests considerable annual variation, possibly owing to differences in the timing of the rainy season. Individuals captured during the period when almost all “resident” breeders were absent (November) appeared to be transients, and were rarely recaptured. Weights differed between sexes, with females (χ = 12.5 ± 1.0) significantly heavier than males (χ = 11.1 ± 0.8). Males were lightest during the breeding season, intermediate in weight during the moulting period, and both sexes were heaviest during the migration period, when they accumulated subcutaneous fat. Females were lightest during the moult period, at which time many may also have dependent fledglings. Many other frugivores and nectarivores may engage in similar altitudinal migrations. Even where altitudinal migration is not possible, birds might migrate to other habitats with different fruit resources or phenologies. The design of nature reserves should accommodate the possibility of significant altitudinal (or cross-habitat) migration for many species of frugivores and nectarivores.

The effect of exogenous melatonin and the plane of nutrition after weaning on ovulation rate in salz ewes lambing in the seasonal anoestrus

1994 ◽  
Vol 1994 ◽  
pp. 83-83
Author(s):  
L. Zarazaga ◽  
F. Forcada ◽  
J.A. Abecia ◽  
J. Mozota
Keyword(s):  
Nutritional Status ◽  
Sexual Activity ◽  
Breeding Season ◽  
Nutrient Status ◽  
Ovulation Rate ◽  
The Other ◽  
Cyclic Activity ◽  
Exogenous Melatonin ◽  
Short Period ◽  
Ovarian Cyclicity

Induction of oestrus and pregnancy in the seasonal anoestrus permits lambing during the breeding season and mating in a short period of time after weaning, but after spring lambing postpartum anoestrus is longer than it is in autumn lambing, and no breeds are able to resume cyclic activity two months after lambing. Nutrient status has been shown to be a major factor affecting the onset of ovarian cyclicity in postpartum ewes. On the other hand, melatonin implants were demonstrated to be efficient in advancing the annual breeding season, but the efficiency of this treatment could be modified by the nutritional status of the animals. The aim of this experiment was to determine the effect of exogenous melatonin, connected with the plane of nutrition after weaning, on the resumption of sexual activity and ovulation rate (OR) in a synthetic Spanish sheep breed lambing in spring.

Operant control of ambient temperature during sleep deprivation

1997 ◽  
Vol 272 (2) ◽  
pp. R682-R690 ◽  
Author(s):  
P. J. Shaw ◽  
B. M. Bergmann ◽  
A. Rechtschaffen
Keyword(s):  
Energy Expenditure ◽  
Sleep Deprivation ◽  
Ambient Temperature ◽  
Thermal Gradient ◽  
Progressive Increase ◽  
Thermal Preference ◽  
Body Temperatures ◽  
Progressive Decline ◽  
Baseline Levels ◽  
Almost All

Rats subjected to total sleep deprivation (TSD) by the disk-over-water method were provided with a continuously available operant by which they could increase ambient temperature (T(amb)). TSD rats progressively increased operant responses for heat to 700% of baseline levels. During the last quarter of sleep deprivation, they maintained mean T(amb) at 9 degrees C above baseline and held T(amb) over 40 degrees C for 35% of the day. In contrast, yoked control rats (TSC) did not change mean T(amb). Although both TSD and TSC rats showed a progressive decline in intraperitoneal temperature (T(ip)), TSD rats maintained an elevated T(amb) even during periods when T(ip) and brain temperatures (T(br)) were above baseline levels. Thus these results confirm and extend earlier findings that rats subjected to TSD show an increase in temperature set point (T(set)). The earlier studies, which utilized short daily trials in a thermal gradient, demonstrated an increase in T(set) early in the deprivation period. The present study, which obtained more extensive data on thermal preference at a range of body temperatures demonstrated an increasing T(amb) for almost all T(ip) and T(br) values, suggesting a progressive increase in T(set) over the course of sleep deprivation. Surprisingly, survival time was shorter than in previous TSD studies. Reduced survival could not be attributed to differences in T(br), T(ip), energy expenditure, or sleep loss from previous studies.

Management of photoperiod to control caprine reproduction in the subtropics

2004 ◽  
Vol 16 (4) ◽  
pp. 471 ◽  
Author(s):  
José Alberto Delgadillo ◽  
Gonzalo Fitz-Rodríguez ◽  
Gerardo Duarte ◽  
Francisco Gerardo Véliz ◽  
Evaristo Carrillo ◽  
...  
Keyword(s):  
Sexual Activity ◽  
Breeding Season ◽  
Management Systems ◽  
Reproductive Seasonality ◽  
Male Effect ◽  
Breeding Management ◽  
Cashmere Goats

Reproductive seasonality is observed in some breeds originating from or adapted to subtropical latitudes. In ‘photoperiodic flexible breeds’, such as Australian cashmere goats, the annual breeding season can be manipulated through nutrition, whereas in ‘photoperiodic rigid breeds’, such as Creole goats from subtropical Mexico, sexual activity can be controlled by altering the photoperiod. In males from the latter breed, artificial long days, whether or not accompanied by the administration of melatonin, stimulate sexual activity during the non-breeding season. These treated males are able to induce the sexual activity of anoestrous females through the male effect under intensive or extensive conditions. Photoperiodic treatments and the male effect can be easily integrated into different breeding management systems in subtropical latitudes.

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

Effect of light on spring breeding of mutton merino ewes

1969 ◽  
Vol 73 (2) ◽  
pp. 177-180 ◽  
Author(s):  
H. Goot
Keyword(s):  
Birth Weight ◽  
Sexual Activity ◽  
Breeding Season ◽  
Control Group ◽  
Artificial Light ◽  
Breeding Activity ◽  
Short Day ◽  
Light Group ◽  
Effect Of Light ◽  
Length Of Gestation

SUMMARYMutton Merino ewes, all of which had lambed in the preceding in-season, were divided into two groups some 30 days after lambing.The ‘light’ group was subjected, over 84 days, to a simulated decrease in daylength, achieved by first adding artificial light to the daylight and then stepping down the light at weekly intervals, from approximately 17 h, on 22 January, to natural daylength (13 ¾ h), on 20 April 1967. The control group was exposed to the normally increasing daylength.Starting on 1 March, the ewes in both groups were ‘teased’ and hand-service commenced on 20 April.The breeding activity (oestrus, ewes lambing, lambs born and twin births) as well as the length of gestation and birth weight appeared to be unaffected by the light.It would appear that the ‘short-day’ photoperiodic theory is not applicable to all breeds of sheep, and it is suggested that in sheep with a long sexual season genetic heterozygosity may be responsible for regulating the breeding season by allowing other environmental stimuli, besides light, to trigger-off sexual activity.

Silver gull breeding at two colonies in the Sydney-Wollongong regio, Australia

1992 ◽  
Vol 19 (4) ◽  
pp. 429 ◽  
Author(s):  
GC Smith ◽  
N Carlile
Keyword(s):  
Clutch Size ◽  
Breeding Season ◽  
Food Availability ◽  
Breeding Success ◽  
Artificial Structures ◽  
Sydney Harbour ◽  
The 1960S ◽  
Almost All

Silver gulls have increased in abundance in Sydney-Wollongong this century. Both the number of colonies and their sizes have grown. The largest colony of 43 000-50000 pairs is on Big I., off Wollongong. Breeding was compared at this colony with that at a satellite colony on artificial structures in Rozelle Bay, Sydney Harbour. Breeding occurred from July to February at Big I., a lengthening of the season since the 1960s. At Rozelle Bay, breeding occurred almost all year round. Egg and clutch size varied within and between years at Big I. First-eggs of clutches, laid during the first breeding peak, were significantly larger than those laid later in each breeding season. The size of third-eggs in clutches differed between years. It is proposed that these disparities were a result of differences in food availability between years. Clutch sizes were significantly larger during the first breeding peak than later clutches of each season. Clutch size was larger at Rozelle Bay. Variation in clutch size was linked to quality of individuals and food availability. Breeding success at colonies was low, indicating that carrying capacities have been reached.

A note on the effect of continuous contact with ewes showing regular oestrus and of post-weaning growth rate on the sexual activity of Corriedale rams

1978 ◽  
Vol 27 (3) ◽  
pp. 361-364 ◽  
Author(s):  
C. G. Winfield ◽  
A. W. Makin
Keyword(s):  
Growth Rate ◽  
Sexual Activity ◽  
Breeding Season ◽  
Sexual Experience ◽  
Continuous Contact ◽  
Treatment Groups ◽  
Low Level ◽  
High Level ◽  
Mating Tests

ABSTRACTThirty-six Corriedale rams were weaned at 3 months of age and subjected to four treatments until 2½ years of age. The treatments consisted of two levels of nutrition, with rams on the high level of nutrition being maintained approximately 15% heavier than those on the low level, and two levels of sexual experience. Sexually experienced rams were kept throughout with ewes that were infertile but showed regular oestrus and inexperienced rams were reared in monosexual groups isolated from females except during periodic mating tests. These 2-h tests were carried out at intervals of 3 to 4 months commencing when the rams were 6 months old. Up to 17 months of age there were no significant differences between treatment groups in the development of ability to serve ewes, except that low nutrition reduced the number of rams which had served ewes at 10 months of age. Between 17 and 28 months of age, rams kept with ewes tended to achieve more serves per test during the breeding season than rams kept without ewes.

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