Effects of chromium picolinate, L-carnitine and thyroxine on the performance, nutrient digestibility and nitrogen balance in pigs weaned at 21 days of age

A 3-week-growth trial was conducted to investigate the effects of chromium picolinate, L-carnitine, and thyroxine on the growth performance, nutrient digestibility, and N balance in starter pigs. Eighty starter pigs (Landrace x Yorkshire x Duroc, 21+/-2 days of age, 5.4 kg of average initial body we ight) were employed in a completely randomized block design with four treat ments: 1. Control: without additives, 2. CrP: control diet + 0.05% of chrom ium picolinate, 3. Carnitine: control diet; 0.5% of Carnifeed ( 10% of carn itine), 4. Thyroxine: control diet + L-thyroxine injection (0.1 mg/day/ hea d), 5 replications and 4 heads per pen. Although there were no significant differences (P>0.05) in average daily gain (ADG) and average daily feed int ake (ADFI), all of the pigs supplemented with CrP, L-carnitine and thyroxin e grew better than pigs in the control group. Pigs fed L-carnitine showed t he best ADG (15% of improvement compared with control group) through the en tire experimental period and feed/gain ratio was improved (P<0.05). Digesti bilities of energy, dry matter, crude protein and crude ash were improved ( P<0.05) by the inclusion of L-carnitine, chromium picolinate or injection o f thyroxine. Pigs fed chromium picolinate showed the best nutrient digestib ilities. In a N balance trial. excreted N was lower (P<0.05) in pigs of all treated groups than in the control group. The N in feed also was more effi ciently retained in pigs of treated groups. The DNA content of the liver wa s higher (P<0.05) in all treated groups. Only the pigs fed L-carnitine show ed a higher (P<0.05) RNA content. The protein content of the liver tended t o be higher (P>0.05) in pigs fed chromium picolinate or injected L-thyroxin e. Total liver DNA, RNA and protein contents were higher (P<0.05) in pigs f ed L-carnitine. it may be concluded that chromium picolinate, L-carnitine a nd thyroxine may be useful for improving growth rate, nutrient digestibilit ies, and N balance in pigs weaned at 21 days of age, although the feasibili ty of an economic return seems quite weak.