Body fat and plasma leptin involvement in the voluntary feed intake of cattle

Abstract

The involvement of adipose derived leptin in feed intake regulation remains elusive. Hence, the purpose of this chapter is to clarify the involvement of body fat measures and endogenous leptin in feed intake of cattle. In study one, 6 16-month old Holstein steers were offered ad libitum feed for seven months. Feed intake, body weight and backfat thickness (BFT) between 6th to 7th and 12th to 13thrib were measured at selected monthly ages from day 1 to 8. On day 8, pre-prandial blood was sampled to measure leptin, insulin, glucose, NEFA, triglyceride and total cholesterol, then ultrasound BFT was taken. In study two, eight heads of finishing (n=4) and growing (n=4) steers were used for cross-over experimental design to know the effects of 2-hour interval of physiological dose intravenous insulin administration (6 mU per kg BW0.75) on plasma leptin and TDN intake per kg BW0.75 from 08:00 until 22:00 hours. Blood was sampled 15 minutes before and after insulin administration to measure plasma metabolites and hormones of growing and finishing Holstein steers. In study one, the inter-relationship of BFT, plasma leptin and TDN intake for the period of seven months, revealed significant positive relationship between backfat thickness and plasma leptin. Negative relationship of TDN intake to plasma leptin (P=0.004; r=0.49) and backfat thickness (P=0.005; r=0.048) was also observed. The reduction of TDN intake from 16 to 23 months was 25%. This inter-relationship between backfat thickness, plasma leptin and TDN intake implies strongly that 12th to 13th rib backfat, an indicator of adiposity reflects correlated elevation of plasma leptin and TDN intake reduction per kg BW0.75 of finishing steers. In study two, no daytime plasma leptin variation was observed for growing and finishing steers. Plasma glucose was depressed in growing, while depression was observed only at certain period after insulin administration for finishing steers. Plasma leptin was not elevated significantly in growing steers, whereas significant plasma leptin elevation was observed among finishing steers at 11:45 and 15:45. At this period of plasma leptin elevation, insulin administration caused 25% reduction in shortterm TDN intake of finishing steers (P<0.07), whereas no short-term TDN reduction was observed in growing steers. Both growing and finishing steers did not show reduction in the 24 hour feed intake. Briefly, the over-all results revealed that leptin elevation is necessary for feed intake reduction; hence leptin is involved only in long-term feed intake regulation in cattle. © 2013 by Nova Science Publishers, Inc. All rights reserved.

Source or Periodical Title

Cattle: Domestication, Diseases and the Environment

Page

39-58

Document Type

Article

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