Relationships of neonatal plasma oxytocin with the behavioral characteristics of cattle introduced into a novel environment

To examine the influence of postnatal oxytocin (OXT) on behavioral development, we examined individual variations in basal OXT and suckling‐induced changes in OXT, and their relationship with emotional traits during development. Blood OXT were measured in 20 Holstein heifer calves at 1 (wk1), 2 (wk2), and 6 weeks of age (wk6). The relationships of OXT variables with principal component scores in the open‐field tests at wk2 and 2 months and the number of flinch, step and kick responses during first artificial insemination and machine milking were analyzed. The basal OXT showed individual variability and significantly correlated (wk1 vs. wk2: r = 0.753, P < 0.001; wk1 vs. wk6: r = 0.499, P < 0.05; wk2 vs. wk6: r = 0.476, P < 0.05). The personality traits reflecting a response in the form of escape from novel environments in the open‐field test at wk2 were inversely correlated with basal OXT at wk1 (r_s = ?0.640, P < 0.01) and wk2 (r_s = ?0.447, P < 0.05). However, none of the behavioral variables after 2 months correlated with OXT. These findings suggest that, postnatal OXT might be related to behavioral characteristics in novel environments only during the early stages of life.     

Individual difference in serum oxytocin concentrations of calves and the correlation with those in dams

We examined individual differences in serum oxytocin concentrations (OT) of calves, and assessed whether these differences were correlated with their dams’ milk and serum OT. Eight Holstein (H), nine Japanese Shorthorn (JS), and six Japanese Black (JB) calves were examined. Blood was collected three times during the first month in H calves, while their dams’ blood was collected three times prior to parturition. Milk was collected twice after parturition from H cows. Blood from JS and JB calves were collected at 1 and 4 months old, while of their dams only once before parturition. Serum OT in H calves at 7 days old was significantly correlated with that at 30 days. Serum OT of JS calves at 1 month old was significantly correlated to that at 4 months, while of JB calves was also positively correlated (r = 0.70). Serum OT of calves showed significant individual differences in each breed. Serum OT of calves was not correlated with the milk OT of dams, except for 3‐day‐old calves that fed on their dams’ milk. We concluded that although serum OT differed among individuals, this difference was stable within each individual and not affected by the serum OT of the dams.     

Density-induced social stress alters oxytocin and vasopressin activities in the brain of a small rodent species

It is known that social stress could alter oxytocin (OT) and arginine-vasopressin (AVP) expression in specific regions of brains which regulate the aggressive behavior of small rodents, but the effects of density-induced social stress are still unknown. Brandt's voles (Lasiopodomys brandtii) are small herbivores in the grassland of China, but the underlying neurological mechanism of population regulation is still unknown. We tested the effects of housing density of Brandt's voles on OT/AVP system with physical contact (allowing aggression) and without physical contact (not allowing aggression) under laboratory conditions. Then, we tested the effects of paired-aggression (no density effect) of Brandt's voles on OT/AVP system under laboratory conditions. We hypothesized that high density would increase aggression among animals which would then increase AVP but reduce OT in brains of animals. Our results showed that high housing density induced more aggressive behavior. We found high-density-induced social stress (with or without physical contact) and direct aggression significantly increased expression of mRNA and protein of AVP and its receptor, but decreased expression of mRNA and protein of OT and its receptor in specific brain regions of voles. The results suggest that density-dependent change of OT/AVP systems may play a significant role in the population regulation of small rodents by altering density-dependent aggressive behavior.     

Actions of intravenous injections of AVP and oxytocin on plasma ACTH,GH, insulin and glucagon concentrations in goats

This study was conducted to investigate the arginine‐vasopressin (AVP)‐ and oxytocin‐induced changes in plasma adrenocorticotropic hormone (ACTH), growth hormone (GH), insulin and glucagon levels and their metabolite concentrations in goats. In this study, five goats were intravenously injected with either AVP (0.3 nmol/kg body weight (BW)) or oxytocin (0.7 IU/kg BW). AVP injection significantly increased ACTH and GH secretions compared to controls, although insulin and glucagon concentrations were not altered. The incremental areas (ICAs) of the ACTH and GH concentrations were higher in the AVP group than in the saline group. Oxytocin injections increased insulin and glucagon secretions, while ACTH level was not altered. GH levels became elevated 30 min after the oxytocin injection. The ICAs of insulin and glucagon after oxytocin was injected were higher than those of the control. Results indicate that AVP is a potent stimulant of ACTH and GH secretions, while oxytocin uses different pathways to regulate insulin and glucagon secretions in goats.     

Relationships between mineral concentrations and physicochemical characteristics in the Longissimus thoracis muscle of Japanese Black cattle

The relationship between mineral concentrations, and the relationship of mineral concentrations with physicochemical characteristics in muscles were investigated using the Longissimus thoracis (LT) muscle of 44 Japanese Black steers. We determined moisture content, fat content, meat color, fatty acid composition and mineral concentrations in the LT muscle. Magnesium (Mg), potassium (K) and zinc (Zn) concentrations had negative correlations with fat content, but sodium (Na), manganese (Mn), copper (Cu) and molybdenum (Mo) concentrations were not correlated with fat content. The concentrations of Mg, Mn, Fe, Cu and Zn largely and positively contributed to the first principal component of mineral concentrations. Because the red muscle was rich in these minerals compared to the white muscle, the variation of these minerals probably results from the abundance of red fibers in the LT muscle. The concentration of K was positively correlated with moisture content but Na concentration was not related to moisture content, suggesting that the intracellular fluid volume can largely affect moisture content. The results of the present experiment suggest that mineral concentrations reflect some traits such as not only fat content but also the composition of myofiber type and the intracellular fluid volume in the LT muscle of Japanese Black cattle.     

Time lag between peak concentrations of plasma and salivary cortisol following a stressful procedure in dairy cattle

Background

Measurement of salivary cortisol has been used extensively as a non-invasive alternative to blood sampling to assess adrenal activity in ruminants. However, there is evidence suggesting a considerable delay in the transfer of cortisol from plasma into saliva. Previous studies in cattle have used long sampling intervals making it difficult to characterise the relationship between plasma and salivary cortisol (PLCort and SACort, respectively) concentrations at different time points and determine whether or not such a time lag exist in large ruminants. Therefore, the objective of this study was to characterise the relationship between plasma and salivary cortisol and determine if there is a significant time lag between reaching peak cortisol concentrations in plasma and saliva across a 4.25 h time-period, using short sampling intervals of 10–15 min, following social separation in dairy cattle.Five cows were separated from their calves at 4 days after calving, and six calves were separated from a group of four peers at 8 weeks of age. Following separation, the animals were moved to an unfamiliar surrounding where they could not see their calves or pen mates. The animals were catheterised with indwelling jugular catheters 1 day before sampling. Blood and saliva samples were obtained simultaneously before and after separation.

Results

In response to the stressors, PLCort and SACort increased reaching peak concentrations 10 and 20 min after separation, respectively. This suggested a 10 min time lag between peak cortisol concentrations in plasma and saliva, which was further confirmed with a time-series analysis. Considering the 10 min time lag, SACort was strongly correlated with PLCort (P < 0.0001).

Conclusions

Salivary cortisol correlates well with plasma cortisol and is a good indicator of the time-dependent variations in cortisol concentrations in plasma following acute stress. However, there is a time lag to reach peak cortisol concentrations in saliva compared to those in plasma, which should be considered when saliva samples are used as the only measure of hypothalamic-pituitary-adrenal axis response to stress in cattle.