Nutritional value of animal feed grade wheat as replacement for maize in lamb feeding for mutton production

The utilization of abundantly available animal feed grade wheat (AFW) as a replacement for conventional and costly cereal supplement in lamb feeding to lower the cost of mutton production was explored. Thirty-five growing lambs divided into five equal groups and were fed diets containing 0, 118, 235, 353 or 470 g kg(-1) AFW replacing equal quantity of maize. The diets were fed in the form of composite feed mixture, which had a roughage (Prosopis cineratia leaves) to concentrate ratio of 25:75. Dry matter intake (DMI) was not different in these groups, ranging from 35 to 42 g kg(-1) body weight, while AFW inclusion linearly (P < 0.05) reduced DMI. The digestibility coefficients of dry matter (DM), organic matter (OM), crude protein (CP) and cellulose were not affected by AFW addition, whereas neutral detergent fibre and acid detergent fibre digestibility coefficients were reduced (P < 0.05). The digestible CP content (142.7-162.7 g kg(-1) diet) increased (P < 0.01) linearly with increased AFW inclusion levels. However, AFW additions did not affect metabolizable energy (ME) value of diet (10.2-10.5 MJ kg(-1) diet DM). Digestible CP intake was similar but digestible DM and OM intake tended to decrease (P < 0.05) linearly when expressed in terms of g kg(-1) W-0.75. ME intake (MJ d(-1)) was not different among the diets but showed linear (P = 0.041) reducing trends with increasing AFW levels in diet. The efficiency of ME and N utilization for unit gain was also not affected by AFW incorporation. N retained as g d-1, percentage of intake and percentage of absorbed ranged from 15.4 to 19.5 g, 49.7% to 60.3% and 62.6% to 74.6%, respectively. Intake and utilization of dietary N was not affected but urinary N excretion reduced (P < 0.05) linearly by AFW. Daily microbial N (MN) flow estimated by urinary purine derivative excretion was significantly (P < 0.01) higher for lambs fed a diet with AFW 235 g kg(-1) (3.05 g MN) and 353 g kg(-1) (2.51 g MN) compared to without AFW diet (1.31 g MN). MN when expressed as g kg(-1) digestible organic matter intake (DOMI) and microbial protein g kg(-1) digestible organic matter apparently fermented in rumen (DOMR) followed a similar trend. During the growth trial, lambs fed diets containing AFW (353 g kg(-1)), which replaced 75% maize had higher total gain (14 kg, P < 0.05) and average daily gain (ADG 154 g, P < 0.05). However, feed efficiency (feed consumed kg(-1) live weight gain) was not different. Rumen pH and microbial enzyme activities studied 4 h post feeding revealed that AFW did not affect rumen pH, which ranged from 5.95 to 6.30. Similarly, carboxymethyl cellulase and beta-xylosidase enzyme activities were not different among treatments, but AFW inclusion linearly (P = 003) increased carboxymethyl cellulase enzyme activities. The alpha-amylase enzyme activity differed significantly (P < 0.05) and was highest (22.6 IU) in groups where AFW replaced maize completely. It was concluded that, in lambs reared under intensive system for mutton production on high concentrate diets, conventional and costly energy supplements like maize can be replaced up to 75% with a low-cost animal feed grade wheat to economize on cost of production. However, more studies are required to confirm these inclusion levels for greater economic returns. (C) 2007 Society of Chemical Industry.