The comparison of plasma level and mRNA expression of leptin from Japanese Black steers and Holstein steers
Introduction
Leptin, the product of the ob gene, is a 16 kDa protein hormone produced mainly by adipose tissue and acts to regulate food intake, energy expenditure, and reproductive function (e.g., Keisler et al., 1999). Expressions of the ob gene and circulating leptin concentrations are highly correlated with percentage of body fat in rodents (Frederich et al., 1995) and with degree of obesity in humans (Considine et al., 1996).
In cattle, plasma leptin levels are closely linked to adipose tissue cellularity, body condition score, and nutritional state (Chilliard et al., 1998, Ehrhardt et al., 2000, Delavaud et al., 2002). Moreover, circulating leptin levels in beef cattle increased during fattening (Kawakita et al., 2001, Tokuda and Yano, 2001, Tokuda et al., 2001). The beef marbling standard (BMS) score was positively correlated with leptin levels (Minton et al., 1998), or not (Kawakita et al., 2001, Tokuda and Yano, 2001, Tokuda et al., 2001).
Carcass tissue production abilities differ between Japanese Black steers and Holstein steers (Zembayashi, 1987, Matsuzaki et al., 1997). Japanese Black steers have a higher muscle:bone ratio than that in Holstein steers, and they also have a unique fat deposition pattern characterized by a large amount of marbling (Zembayashi, 1994). However, the mechanisms involved in the differences of carcass characteristics, particularly fat accumulation, between these breeds have not been well understood.
Therefore, one of the objectives of this study was to examine whether circulating levels and mRNA expression in adipose tissue of leptin are different between Japanese Black steers and Holstein steers under typical Japanese feeding conditions for beef cattle, in order to obtain a better understanding of mechanisms involved in the regulation of body fat accumulation. We also investigated the relation between carcass characteristics and leptin profiles in these breeds.
Section snippets
Animals, sample collections, and analysis
Nine Japanese Black steers and five Holstein steers were used in this study. The Japanese Black steers and the Holstein steers were 360±7 and 386±3 days of age at the start of the experiment, respectively. The feeding conditions for both breeds were designed according to the Japanese Feeding Standard for Beef Cattle (Agriculture, Forestry and Fisheries Research Council Secretariat, 2000) to be typical for beef cattle in Japan. Briefly, the Japanese Black steers were offered diets composed of a
Performance and carcass characteristics
Performance and carcass characteristics of the Japanese Black and Holstein steers are presented in Table 2. The Holstein steers reached the final weight faster than did the Japanese Black steers (P<0.01), although they were slightly older at the start of this experiment. The amounts of the diets offered were different between these breeds, but feed intake was close to ad libitum. Average DM intake during the whole fattening period for the Holstein steers was greater than that for the Japanese
Discussion
It has been reported that the Multi-Species Leptin RIA for bovine plasma give underestimated absolute values compared to the specific bovine RIA developed by several groups (Ehrhardt et al., 2000, Delavaud et al., 2002). The commercial RIA used in this study, however, detected relative leptin values in cattle and significant differences when effects of treatments were large (Chilliard et al., 2001, Delavaud et al., 2002). The mean leptin content in the Holstein steers weighing about 700 kg
Acknowledgments
The authors thank Dr. T. Terada, the staff of the Ruminants and Field Management Section, and the staff of the Department of Animal Physiology and Nutrition for their technical assistance, and they are very grateful to Ms. M. Satoh for her technical assistance and chemical analyses.
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