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Relationships between Methionine Supply, Nitrogen Retention and Plasma Insulin-like Growth Factor-I in Growing Sheep Nourished by Total Intragastric Infusions |
Chong Li, Guangyong Zhao |
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Abstract |
Four 4-month old CharolaisDorset male sheep (initial liveweight 25.01.1 kg), fitted with rumen and abomasal fistulas and nourished by total intragastric infusions, were used to study the relationships between methionine (Met) supply, nitrogen (N) retention and plasma insulin-like growth factor-I (IGF-I). Four graded levels of Met, i.e. 0 g/16 g N, 1.76 g/16 g N, 3.52 g/16 g N and 7.04 g/16 g N, were infused into abomasums as experimental treatments. The sheep and treatments were allocated in a 43 incomplete Latin square design (Yudon square design). The experiment lasted 3 periods and each period was 10 days. Quadratic correlations were found between Met level (x, g/16 g N) and N retention (y, g/d): y = -0.03x2+0.41x+2.62, r2 = 0.66, n = 12, p = 0.008, and between methionine level (x, g/16 g N) and plasma IGF-I concentration (y, ng/ml): y = 0.80x2-4.53x+190.24, r2 = 0.51, n = 12, p = 0.009. No significant correlation was found between plasma IGF-I (x, ng/ml) and N retention (y, g/d) (p>0.05). It was concluded that Met level had a significant influence on N retention and plasma IGF-I concentration whereas IGF-I might not be an important mediator in the regulation of N metabolism by Met in growing sheep nourished by total intragastric infusions. |
Keywords:
Methionine; Nitrogen Retention; IGF-I; Sheep |
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