An effort was made to assess the comparative efficacy of liquid DL- methionine hydroxy analogue free acid (MHA-FA) and DL- methionine (MET) in maize-soybean diet on meat production performance of broiler chickens at 6 weeks of age. Three hundred (300) thrifty and bright looking unsexed chicks (commercial strain, Hubbard) were selected, wing banded, weighed and randomly distributed into 30 groups of 10 chicks each. The experiment was conducted following completely randomized design having 3 dietary treatments with 10 observations (replicates) in each (3 x 10 x 10). Three dietary treatments (iso-nitrogenous, 21% crude protein and iso-caloric, 3150 kcal ME/kg during starting phase i.e. 0-3 weeks; and 20% crude protein with 3200 kcal ME/kg during finishing phase i.e. 3-6 weeks of age) were formulated viz., D1- Maize-soya based basal diet (Control), D2- Maize-soya based basal diet+ supplemented with DL- methionine to meet its requirements and D3- Maize-soya based basal diet supplemented with MHA-FA @ 1.54 times of DL-methionine of treatment 2. All the birds were housed in battery cages under uniform housing, management and feeding practices except the variations in the dietary treatments as envisaged above. The body weight change of individual birds and feed intake were recorded weekly. Two metabolism trials (total excreta collection method) involving all birds, each of three days duration, were conducted at 3rd and 6th week of age. At the end of 6th week of age, 20 birds were taken out randomly from each treatment and sacrificed to study carcass traits and organs' yield.
The data of 0-3 weeks period revealed that broiler chickens received supplemental methionine (D2) had significantly higher gain in body weight (472g/bird) which was followed by MHA supplemented group (451 g/b) and un-supplemented control (421 g/b). The live weight gain recorded in MET supplemented group (1095 g/b) during 3-6 weeks of age were similar to that of MHA groups (1092 g/b) but the gains in both the treatments were significantly higher than the un-supplemented control (980 g/b) group. During overall growth phase though highest gain in body weight was recorded in MET group (1570 g/b) but it was statistically similar to MHA group (1543 g/b) and both the treatments resulted in better gain (P<0.0001) than un-supplemented control (1400 g/b). The efficacy of methionine hydroxy analogue in comparison to methionine for growth was 62.11, 64.82 and 63.88% at 0-3, 3-6 and 0-6 weeks of age, respectively.
The feed intake during 0-3 weeks of age in the dietary treatment D2 differed (P>0.076) from control diet, but remained similar to that recorded in MHA group. During 3-6 weeks and overall period (0-6wk) the feed intake differed significantly due to treatments being highest in D2, followed by in D3 and D1. Feed conversion efficiency improved significantly on supplementation of either methionine (1.55) or MHA (1.60) in the basal diet containing maize and soybean meal (1.69) during 0-3 weeks of age. During this period the improvement was significantly higher in methionine-supplemented group than MHA group. In contrary, the broilers kept on finisher diet supplemented with MHA (1.92) had better FCR than methionine supplemented (2.00) or un-supplemented group (2.01). The feed conversion efficiency calculated for overall period however did not differ significantly and the values were 1.98, 1.91 and 1.94, respectively. The efficacy of methionine hydroxy analogue in comparison to methionine for feed efficiency was 62.98, 67.73 and 64.01% at 0-3, 3-6 and 0-6 weeks of age, respectively. The energy and protein efficiency differed during 0-3 weeks of age, while thereafter or during overall growth phase efficiencies remained similar. The mortality (%) recorded were 3, 3 and 4 in D1, D2 & D3 and not attributable to dietary treatments. Dry matter metabolizability did not differ due to dietary treatments. Nitrogen retention increased significantly in diets supplemented with methionine or MHA both at 3rd and 6th weeks of age. Nitrogen retention however, did not differ due to methionine or MHA-FA supplementation.
The carcass characteristics in terms of feather loss (P<0.011), eviscerated yield (P<0.004), abdominal fat pad (P<0.007), and breast yield (P<0.04) were significantly different among the treatments. The loss of feather, as percent of live weight, was significantly higher in un-supplemented control (6.16%) than MET (5.20%) or MHA (4.75%) supplemented group. Though feather development did not differ statistically, but it was numerically lower in MHA groups than MET group. The eviscerated yields emanated from diets D3 (72.69 %) or D2 (71.75 %) were statistically higher (P<0.004) to that of control (70.09 %). Abdominal fat pad was also significantly higher in broilers fed control diet (2.58 %) than MET (2.23 %) or MHA (2.03 %) supplemented group. Breast yield was higher in MHA (17.34 %) fed broilers than those fed methionine supplemented (16.70 %) or un-supplemented diets (16.14 %). Crude protein content in breast muscle increased significantly with the addition of methionine or MHA in diet. There was apparent reduction in ether extract contents in breast muscle in MET or MHA group. The composition of thigh muscle did not differ due to dietary treatments. The efficacy of methionine hydroxy analogue in comparison to methionine was 65.85%, 71.40% and 67.49% for eviscerated yield, abdominal fat pad reduction and breast yield, respectively. The weight of spleen as per unit body weight was significantly higher in MET (0.17%) or MHA (0.17%) supplemented diets than control diet (0.13%). The yield of other immune organs (thymus and bursa) were, however, statistically similar. The length of small and large intestine decreased significantly (P < 0.01) in MHA supplemented group.
It can be concluded that supplementation of methionine or methionine hydroxy analogue improved growth, efficiency of feed utilization, eviscerated yield and breast yield. The supposition that methionine hydroxy analogue - free acid (MHA-FA) is about 65% efficient to that of DL- methionine for meat production performance of broiler chickens at 6 weeks of age is valid.