The impact of diet and arginine supplementation on pancreatic mass, digestive enzyme activity, and insulin-containing cell cluster morphology during the estrous cycle in sheep

• Published in: Domestic animal endocrinology Vol. 59; pp. 23 - 29
• Main Authors: Keomanivong, F.E., Grazul-Bilska, A.T., Redmer, D.A., Bass, C.S., Kaminski, S.L., Borowicz, P.P., Kirsch, J.D., Swanson, K.C.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.04.2017
• Subjects: Animal Feed; Animal Nutritional Physiological Phenomena; Animals; Arginine; Arginine - administration & dosage; Arginine - pharmacology; Diet - veterinary; Dietary Supplements; Digestion - physiology; Enzymes; Estrous Cycle - physiology; Feed intake; Female; Insulin - metabolism; Pancreas; Pancreas - anatomy & histology; Pancreas - drug effects; Sheep; Sheep - physiology; Enzymes; Sheep; Arginine; Pancreas; Feed intake
• ISSN: 0739-7240; 1879-0054
• DOI: 10.1016/j.domaniend.2016.10.001

To determine the effect of feed intake and arginine treatment during different stages of the estrous cycle on pancreatic mass, digestive enzyme activity, and histological measurements, ewes (n = 120) were randomly allocated to 1 of 3 dietary groups; control (CON; 2.14-Mcal metabolizable energy/kg), underfed (UF; 0.6 × CON), or overfed (OF; 2 × CON) over 2 yr. Estrus was synchronized using a controlled internal drug release device for 14 d. At controlled internal drug release withdrawal, ewes from each dietary group were assigned to 1 of 2 treatments; Arg (L-Arg HCl, 155-μmol/kg BW) or Sal (approximately 10-mL saline). Treatments were administered 3 times daily via jugular catheter and continued until slaughter on d (day) 5 and 10 of the second estrus cycle (early luteal phase, n = 41 and mid-luteal phase, n = 39; yr 1) and d 15 of the first estrus cycle (late luteal phase, n = 40; yr 2). A blood sample collected from jugular catheters for serum insulin analysis before slaughter. The pancreas was then removed, trimmed of mesentery and fat, weighed, and a sample snap-frozen until enzyme analysis. Additional pancreatic samples were fixed in 10% formalin solution for histological examination of size and distribution of insulin-containing cell clusters. Data were analyzed as a completely randomized design with a factorial arrangement of treatments. Diet, treatment, and diet × treatment were blocked by yr and included in the model with initial BW used as a covariate. Day of the estrous cycle was initially included in the model but later removed as no effects (P > 0.10) were observed for any pancreatic variables tested. Overfed ewes had the greatest (P < 0.001) change in BW, final BW, change in BCS, and final BCS. A diet × treatment interaction was observed for change in BW and final BW (P ≤ 0.004). Overfed and CON had increased (P < 0.001) pancreas weight (g) compared with UF ewes. Protein concentration (g/pancreas) was the lowest (P < 0.001) in UF ewes, whereas protein content (mg/kg BW) was greater (P = 0.03) in UF than OF ewes. Activity of α-amylase (U/g, kU/pancreas, U/kg of BW, and U/g protein) and trypsin (U/pancreas) was greater (P ≤ 0.003) in OF than UF ewes. Serum insulin was the greatest (P < 0.001) in OF ewes. No effects were observed for pancreatic insulin-containing cell clusters. This study demonstrated that plane of nutrition affected several measurements of pancreatic function; however, the dosage of Arg used did not influence pancreatic function. •Pancreatic digestive enzymes and serum insulin increased with increased feed intake.•Pancreatic insulin-containing clusters were not influenced by feed intake.•Arginine treatment had minimal effects on pancreatic function.•Arginine did not rescue nutritionally induced reduction in pancreatic function.