Rowett Research Institute

About: Rowett Research Institute is a based out in . It is known for research contribution in the topics: Rumen & Population. The organization has 2986 authors who have published 4459 publications receiving 239472 citations.

Leptin receptor and neuropeptide y gene expression in the sheep brain

Abstract: Leptin, a protein secretory product of adipocytes, is important in appetite control, energy balance and reproduction. In rodents, the physiological effects of leptin are centrally mediated, in part via the neuropeptide Y (NPY) system in the hypothalamus. The role of leptin in ruminants, where appropriate nutrition and reproductive status are of major economic concern, is largely unknown. To elucidate the function of leptin in sheep we have investigated putative sites of action for leptin in the brain and pituitary gland using both in-situ hybridization to detect expression of the signalling form of the leptin receptor (OB-Rb) and in-vitro autoradiography using (125I)leptin to detect sites of specific leptin binding. OB-Rb gene expression occurred in the hippocampus, cerebral cortex, preoptic area, stria terminalis and choroid plexus, and within the hypothalamus in the paraventricular (PVN), ventromedial (VHM) and arcuate (ARC) nuclei. OB-Rb gene expression in the ovine pituitary gland was not detected by in-situ hybridization. Sites of OB-Rb and NPY gene expression were compared using both in-situ hybridization on adjacent sections containing the arcuate and ventromedial nuclei, and dual in-situ hybridization on sections containing these areas. In serial sections, OB-Rb expression was found to correspond closely with that of NPY over the arcuate nuclei. Using dual in-situ hybridization, NPY expressing neurones in the arcuate nuclei were also positive for OB-Rb gene expression. Therefore, it appears that leptin may partly act via OB-Rb located on NPY neurones in the sheep hypothalamus as in the rodent.

The effects of feeding procedure on closure of the oesophageal groove in young sheep.

Abstract: 1. Barium sulphate suspensions were given to young sheep by mouth or by injection via an oesophageal catheter. Closure of the oesophageal groove was assessed by observing radiographically whether the suspension passed to the ruminoreticulum or to the abomasum.2. Complete closure of the groove took place in lambs that were trained to drink small meals from a trough after being weaned from their dams, a finding similar to that for lambs weaned on to a teat-bottle.3. When barium was injected into the oesophagus of lambs that were excited by being offered their bottle or trough beyond their reach, the barium passed direct to the abomasum if the normal feeding routine was closely imitated. When the lambs were able to discriminate between this teasing procedure and the normal routine, the barium frequently passed to the ruminoreticulum. If the lambs were not teased the barium passed invariably to the ruminoreticulum.4. It is concluded that the reflex closure of the groove can be conditioned by the feeding procedure adopted at weaning so that it no longer depends on the stimuli associated with sucking and swallowing.

The efficiency of utilization of metabolizable energy and apparent absorption of amino acids in sheep given spring- and autumn-harvested dried grass.

Abstract: Three experiments were conducted with sheep given spring-harvested dried grass (SHG) and autumn-harvested dried grass (AHG). The first was a calorimetric trial to determine the metabolizable energy (ME) content of each grass and the efficiency with which sheep utilize their extra ME intakes above the maintenance level of intake. The second examined the relative amounts of extra non-ammonia-nitrogen (NAN) and individual amino acids absorbed from the small intestine per unit extra ME intake as the level of feeding was raised from energy equilibrium (M) to approximately 1.5 M. The third was a further calorimetric trial to investigate the effect of an abomasal infusion of 30 g casein/d on the efficiency of utilization of AHG. The ME content of the SHG (11.8 MJ/kg dry matter (DM] was higher than that of AHG (10.0 MJ/kg DM). The efficiency of utilization of ME for productive purposes (i.e. above the M level of intake; kf) was higher when given SHG (kf 0.54 between M and 2 M) than when given AHG (kf 0.43 between M and 2 M). As the level of intake of each grass was raised from M to 1.5 M there was a greater increment in the amounts of NAN (P less than 0.001) and the total amino acid (P less than 0.05) absorbed from the small intestines when sheep were given the SHG (NAN absorption, SHG 5.4 g/d, AHG 1.5 g/d, SED 0.54; total amino acid absorption SHG 31.5 g/d, AHG 14.3 g/d, SED 5.24). Infusion of 30 g casein/d per abomasum of sheep given AHG at M and 1.5 M levels of intake increased (P less than 0.05) the efficiency of utilization of the herbage from kf 0.45 to kf 0.57. Consideration is given to the possibility that the higher efficiency of utilization of ME in sheep given SHG may be related to the amounts of extra glucogenic amino acids absorbed from the small intestine which provide extra reducing equivalents (NADPH) and glycerol phosphate necessary for the conversion of acetate into fatty acids.