The effect of various levels of lysine infused intraperitoneally on mohair quality and nitrogen metabolism in Angora goats

Nutritional manipulation of mohair quality was investigated by measuring the effects of various intraperitoneal lysine doses on mohair quality and N metabolism in 18 mature Angora wethers. Animals were infused intraperitoneally with lysine (0, 1.18, 2.23, 3.35, 4.67, or 5.92 g day-1) for 28 days. Lysine infusion decreased linearly the percentage of fibers that were medullated (R = 0.30; P = 0.0006). Fiber diameter (R = 0.16; P > 0.10) was not affected. However, several metabolic changes were observed when the highest doses (4.67 and 5.92 g) of lysine were infused, which may be indicative of an amino acid imbalance or toxicity. Plasma lysine concentrations increased quadratically (R = 0.51; P < 0.10) when lysine infusions exceeded 3.35 g lysine day-1 and urinary N excretion increased (linear: R = 0.55; P < 0.02). DM intake, N absorbed, N retention, and N retention as a percentage of dietary and infused N, were not affected (P > 0.10) by lysine infusion. Plasma urea was elevated (linear: P < 0.015). The percentage of medullated fibers decreased linearly with increasing lysine content of the infusate. The infusate also caused accumulation of plasma lysine at infusions greater than 4.7 g lysine day-1.