ABSTRACT
The study was planned to compare the influence of high and low input feeding
systems on nutrients ingestion, digestibilities, nitrogen retention (NR), blood urea
nitrogen (BUN), metabolic hormones, liver enzymes and economics of weight gain in
growing male lohi lambs. Eighty lambs, 3 months of age, were randomly divided into
ten groups with eight animals in each. Ten diets were formulated. The diet F only
contained barseem fodder (hay) while nine isocaloric diets with three levels of crude
protein (CP) i.e. low protein (LP, 18%CP), medium protein (MP, 22%CP) and high
protein (HP, 26%CP) with ionophores (LPI, MPI and HPI) and probiotics (LPP, MPP
and HPP) were formulated. Inclusion rate of ionophores and probiotics in diets was
20ppm and 0.1% of ration, respectively. The LP, MP and HP diets were grouped as
concentrate (C) diets. These CP diets when supplemented with ionophores and
probiotics were grouped as CI and CP diets. Lambs fed C, CI, CP diets consumed
higher feed than those fed F diet. A linear and quadric increase (p<0.05) in nutrients
intake was observed in lambs fed C, CI and CP diets with increasing dietary CP level.
Similar trend was noticed for neutral detergent fiber (NDF) and acid detergent fiber
(ADF) intakes (p<0.05). However, ionophores and probiotics supplementation did not
affect feed consumption in lambs fed C, CI and CP diets. Dry matter digestibility and
nitrogen retention was higher (p<0.05) in lambs fed C, CI and CP diets than those fed F
diet. The blood urea nitrogen (BUN) increased linearly with increasing dietary CP in
the concentrate diets. However, ionophores and probiotics supplementation did not  affect BUN (p<0.05). Serum creatinine was not affected by ionophores or probiotics,
however, increased linearly with increasing dietary CP in the concentrate diets.
Cholesterol, triglyceride, LDL and HDL were higher (p<0.05) in lambs fed
concentrates than those fed fodder only. Serum calcium, P and Cl were higher (p<0.05)
and blood pH was lower (p>0.05) in lambs fed concentrate diets than those fed fodder
only. A gradual increase in dietary crude protein concentration of C, CI and CP diets
increased triiodothrionine (T3), thyroxin (T4) and testosterone in lambs compared to  those fed on fodder. Alanine aminotransferase (ALT) were higher (P<0.05) in lambs
fed concentrates than those fed fodder only. A linear increase was observed in blood
ALT with increasing CP levels in concentrate diets. Economic appraisal indicated that
feed to gain ratio was lower in lambs fed concentrate diets than those fed diets
containing fodder only. Total feed cost of lambs fed concentrate diets was higher (p
<0.05) than those fed fodder only. However, cost to produce one kg live weight of
lambs fed concentrates were lower (p >0.05) than those fed diets containing fodder only
reflecting that high concentrate portion in feed reduced the cost of production in
growing lambs.