Calves delay estrus cycles in postpartum cows by mechanisms other than suckling

It is generally accepted that the suckling stimulus and the interactions between lactation and level of nutrition regulate the interval from calving to cycling in beef cows. However, rnastectomized cows (udder removed) kept with their calves had longer postpartum intervals to ovulation and estrus than mastectomized cows without calves. We conclude that ovulation and estrus can be suppressed by some cow-calf interaction that is independent of lactation and suckling

How does cow-calf association inhibit the onset of estrous cycles after calving?

The "suckling response" maintains anestrus in beef cows for about 40 to 60 days postpartum. The suckling response remains intact in mastectomized cows, so stimulation of the inguinal area, and not milk flow or teat stimulation, must be part of the response. Cow-calf recognition is part of the suckling response because suckling by cross-fostered calves after nose-to-nose contact followed by suckling of an alien calf does not prevent cycling. We believe the suckling response involves a cow recognizing her own calf, followed by the calf stimulating her inguinal area. It may be possible to initiate estrus by simply blocking the cow's recognition of her own calf

Pattern of ovulation in the East African root rat ( Tachyoryctes splendens

The East African root rat, Tachyoryctes splendens is a solitary dwelling subterranean rodent that exhibits a marked seasonal reproduction linked to the bimodal rainfall pattern of East Africa. The current study set out to determine whether the East African root rat is an induced or spontaneous ovulator. Five wild caught adult females were monitored non-invasively for ovarian cyclicity by measuring urinary progesterone every two days over a period of 120 days. Females were subjected to three different experimental treatments namely, initially singly housed/Control (C), Non-Physical Contact with a male (NPC) and Physical Contact with a vasectomised male (PC), respectively. The concentration of urinary progesterone was higher during PC than during either NPC or C. The act of coitus appears to be necessary for ovulation to occur in the females, despite the fact that the males were vasectomised and incapable of fertilising the females. The male root rats were found to possess epidermal spines on the penis which can be used to remove copulatory plugs as well as bring about cervical stimulation during coitus. The spines result in the induction of ovulation as has been proposed for other solitary subterranean rodents. The findings from the female progesterone profiles and the assessment of penile morphology suggest that the female root rat is an induced ovulator stimulated by penile intromission during coitus.Le rat-taupe splendide (Tachyoryctes splendens (Rüppell, 1835)) est un rongeur souterrain solitaire qui présente une reproduction nettement saisonnière associée au motif de pluviosité bimodal de l’Afrique de l’Est. L’étude visait a` déterminer si l’ovulation est provoquée ou spontanée chez ce rongeur. La cyclicité ovarienne de cinq femelles capturées a` l’état sauvage a été surveillée de manière non intrusive en mesurant la progestérone urinaire tous les deux jours pendant 120 jours. Les femelles ont fait l’objet de trois traitements expérimentaux différents, a` savoir qu’elles étaient maintenues initialement seules (témoin; C), en contact non physique avec un mâle (NPC) et en contact physique (PC) avec un mâle vasectomisé, respectivement. La concentration de progestérone urinaire était plus élevée durant le traitement PC que durant les traitements NPC ou C. Le coït semble être nécessaire pour que l’ovulation ait lieu chez les femelles. Il a été constaté que des épines épidermiques sont présentes sur le pénis des rats-taupes splendides mâles, qui peuvent être utilisées pour stimuler le col utérin durant le coït. Ces épines provoquent l’ovulation, comme cela a été proposé pour d’autres rongeurs souterrains solitaires. Les profils de progestérone des femelles et l’évaluation de la morphologie du pénis donnent a` penser que l’ovulation des rats-taupes splendides femelles est provoquée par la stimulation produite par l’intromission pénienne durant le coït. [Traduit par la Rédaction]The University of Pretoria (UP PhD fellowship grant), South Africa and the South African Research Chair of Mammal Behavioural Ecology and Physiology from the DST-NRF to NCB.http://www.nrcresearchpress.com/journal/cjzhb2017Zoology and Entomolog