Changes in single unit activity in the lateral hypothalamic area of goats during feeding

The Physiological Suppressing Factors of Dry Forage Intake and the Cause of Water Intake Following Dry Forage Feeding in Goats - A Review

The goats raised in the barn are usually fed on fresh grass. As dry forage can be stored for long periods in large amounts, dry forage feeding makes it possible to feed large numbers of goats in barns. This review explains the physiological factors involved in suppressing dry forage intake and the cause of drinking following dry forage feeding. Ruminants consume an enormous amount of dry forage in a short time. Eating rates of dry forage rapidly decreased in the first 40 min of feeding and subsequently declined gradually to low states in the remaining time of the feeding period. Saliva in large-type goats is secreted in large volume during the first hour after the commencement of dry forage feeding. It was elucidated that the marked suppression of dry forage intake during the first hour was caused by a feeding-induced hypovolemia and the loss of NaHCO3 due to excessive salivation during the initial stages of dry forage feeding. On the other hand, it was indicated that the marked decrease in feed intake observed in the second hour of the 2 h feeding period was related to ruminal distension caused by the feed consumed and the copious amount of saliva secreted during dry forage feeding. In addition, results indicate that the marked decreases in dry forage intake after 40 min of feeding are caused by increases in plasma osmolality and subsequent thirst sensations produced by dry forage feeding. After 40 min of the 2 h dry forage feeding period, the feed salt content is absorbed into the rumen and plasma osmolality increases. The combined effects of ruminal distension and increased plasma osmolality accounted for 77.6% of the suppression of dry forage intake 40 min after the start of dry forage feeding. The results indicate that ruminal distension and increased plasma osmolality are the main physiological factors in suppression of dry forage intake in large-type goats. There was very little drinking behavior observed during the first hour of the 2 h feeding period most water consumption occurring in the second hour. The cause of this thirst sensation during the second hour of dry forage feeding period was not hypovolemia brought about by excessive salivation, but rather increases in plasma osmolality due to the ruminal absorption of salt from the consumed feed. This suggests the water intake following dry forage feeding is determined by the level of salt content in the feed.

Stereotaxic atlas of the goat brain for an accurate approach to the hypothalamic nuclei

While the external acoustic meatus of mice, rats and cats are at right angles to the side of the head, they are angled forward in ruminants. Because of this, the coordinates of stereotaxic atlases created using the same methods as for small animals were not suitable for practical use and made it very difficult to place electrodes in hypothalamic nuclei. The aim of this study was to produce a highly accurate stereotaxic atlas for goats that enables precise placement of electrodes in the hypothalamic nuclei. A method of fixing the head in place so as to maintain the basis cranii interna in a horizontal position was established allowing right angled three dimensional axes to be superimposed in the brains of Japanese Saanen goats. This research attempted to establish a new landmark alternative to the external acoustic meatus. The new landmark is the extremitas posterior clivus presphenoidale (EPCP) at the base of cranial bone. This landmark can easily be visualized through lateral radiography. This enabled the AP (anterior-posterior) and H (height) coordinates of the position to be fixed at 30 and 5, respectively. The A30 and H5 coordinates of the serial frontal, sagittal, and horizontal stereotaxic atlases in the present experiment were set to coincide with the position of the EPCP. In order to clarify whether the deviation of the stereotaxic brain coordinates due to inconsistent immobilization the goat's head was eliminated, the AP and H coordinates of the extremitas anterior fossa hypophysialis and the extremitas posterior fossa hypophysialis were measured using the corrected axes. In the three dimensional stereotaxic atlas created using the new landmark, it became possible to approach the hypothalamic nuclei of goats accurately. This method significantly differentiates the stereotaxic atlas from its predecessors.