Exposure to a dog elicits different cardiovascular and behavioral effects in pregnant and lactating goats

Abstract

BackgroundHeart rate and plasma cortisol concentration are often used in evaluation of physiological reactions to stress and fear, but arterial blood pressure is rarely measured in farm animals. Goats are prey animals and can be expected to react strongly to a predator, especially when they have kids. We hypothesized that exposure to a dog elicits a flight response during pregnancy and a fight response when goats have kids to defend. Arterial blood pressure and heart rate should increase in both these cases, due to a synchronized discharge of the sympathetic nervous system.MethodsSeven goats were exposed to a dog for 15 minutes at 12 ± 3 days before, and again at 10 ± 1 days after, parturition. Arterial blood pressure, heart rate, and activity were registered by telemetry. Behavioral data were collected during 5 minute sessions, followed by blood samples obtained via intrajugular catheters. Plasma cortisol concentration was analyzed by radioimmunoassay.ResultsAt the appearance of the dog, the mean arterial blood pressure of the goats increased from 90 ± 8 to 111 ± 8 mmHg (p < 0.001) during pregnancy and from 96 ± 8 to 108 ± 8 mmHg during lactation (p < 0.001). Heart rate did not change at dog exposure during lactation, but increased from 117 ± 6 to 126 ± 10 beats/min (p < 0.01) during pregnancy. Dog exposure resulted in plasma cortisol concentration increasing from 17 ± 1 to 43 ± 7 nmol/l (p < 0.01) during pregnancy and from 21 ± 1 to 49 ± 6 nmol/l (p < 0.01) during lactation. In response to the dog, goats vocalized at a higher frequency and started to ruminate later during lactation compared to pregnancy.ConclusionsWhen goats were exposed to a dog during pregnancy, their heart rate, blood pressure, and plasma cortisol increased, in contrast to lactation when only their blood pressure and plasma cortisol increased. However, when they were lactating, goats vocalized more and started to ruminate later compared to when they were pregnant.

The hypothalamo-pituitary-adrenal (HPA) axis in sheep is attenuated during lactation in response to psychosocial and predator stress

“…We showed that the presence of the offspring and sucking by the offspring are important in attenuating HPA axis responses to isolation and restraint in lactating ewes [4] . The mechanisms by which the presence of the lambs, and suckling, influence the activity of the HPA axis are unknown, but at least part of the mechanism may involve oxytocin, which is released in response to cues from the infant, especially sucking [5] , [11] , [12] , [13] . There is experimental evidence that oxytocin can act centrally to attenuate the activity of the HPA axis [for review see [14] ], and we showed in the sheep that oxytocinergic neurons are located in close proximity to corticotrophin releasing hormone (CRH) and arginine vasopressin (AVP) neurons in the paraventricular nucleus (PVN) [4] .…”

Introducing young dairy goats into the adult herd after parturition reduces social stress

“…In LK, an increase was measured in only half of the animals and the size of the increase was smaller. Baseline values and cortisol increases in response to an acute stressor (a dog) did not differ between pregnant and lactating goats (Olsson and Hydbring-Sandberg, 2011), indicating no general difference in HPA axis reactivity due to reproductive stage and supporting the interpretation that the smaller increase in cortisol in LK indeed reflects lower levels of stress during introduction.…”

The Effect of Mother Goat Presence during Rearing on Kids’ Response to Isolation and to an Arena Test

“…At two weeks, the vocalization rate after dog bark in DAY-SEP and NON-SEP kids increased, while the SEP kids continued vocalising at a lower level. The sound of a dog bark has been shown to cause alertness in isolated goats [ 49 ] and exposure to a dog caused increased vocalization and elevated blood pressure and plasma cortisol in lactating goats [ 50 ]. Hence, the dog bark probably initiated an enhanced fear response in the arena test.…”

“…Cortisol concentration and heart rate are commonly used as physiological indicators of stress in goats [ 39 , 46 , 50 , 59 , 60 , 61 , 62 , 63 ]. Overall, concentrations of saliva cortisol were low in all samples, with large individual differences.…”