FEED STRATEGIES ▶▶▶


respectively, relative to the growth of control birds. Male broilers exhibited complete body weight recovery at 49 days of age, with no difference between the birds restricted by the dietary glycolic acid addition or those subjected to phys- ical feed restriction. Due to its natural occurrence, glycolic acid may serve as a safe and useful anorectic compound for restricting feed intake in poultry.


In one study, the use of 50g/kg of calcium propionate as an appetite suppressor has resulted in gains of birds close to those obtained under a recommended program of quantitative feed restriction between 2 to 6 weeks of age.


Chemical methods In one study, the use of 50g/kg of calcium propionate as an appetite suppressor resulted in gains of birds close to those obtained under a recommended program of quantitative feed restriction between 2 to 6 weeks of age. Glycolic acid has also been used as a chemical means of restricting feed intake of broilers. The feed intake of birds given diets supple- mented with 1.5% and 3% glycolic acid was depressed by 17% and 45%, respectively. These reductions in feed intake due to glycolic acid supplementation resulted in growth re- tardation during the under nutrition period to 71% and 41%


Table1 – Production performance of unrestricted and feed restricted broiler chickens on whole production period (6 weeks of age).


Treatment


T0 T1 T2 T3 T4 T5 T6


Feed intake (g)


3300.9 3206.4 3215.8 3175.2 3082.2 3220.6 3145.2


Weight gain (g)


1460.66 1551.58 1466.69 1483.10 1412.96 1603.56 1474.53


Feed conversion Final body ratio 2.26 2.06 2.19 2.14 2.18


2.004 2.13


weight (g) 1503.69 1594.61 1509.72 1526.13 1455.99 1646.59 1517.56


Experimental treatments: control (T0) and other six groups were fed restricted as: T1 (8 h/day in 7-14 days of age), T2 (16 h/day in 7-14 days of age), T3 (8 h/day in 14-21 days of age), T4 (16 h/day in 14-21 days of age), T5 (8 h/day in 21-28 days of age), T6 (16 h/day in 21-28 days of age). Source: S. N. Saber et al, 2011


14 ▶ POULTRY WORLD | No. 2, 2018


Duration and timing of restricted feeding The longer the period of underfeeding, the more difficult it is for broilers to compensate for the reduction in weight gain. Most workers recommended feed restriction of not more than seven and five days for male and female broilers, re- spectively, to allow for full body weight recovery. The restric- tion of the feed intake of birds to 90% of that of control birds from 7 to 49 days of age has resulted in a significantly lower final body weight at 56 days of age, probably due to the in- sufficient time allowed for the birds to exhibit complete growth compensation. Initiation of 6 days feed restriction at any age between 3 and 11 days of age seems to permit complete body weight recov- ery by 8 weeks of age in broilers. On the other hand, when initiating a feed restriction program at 3 weeks of age, very little evidence of compensatory growth has been noticed, probably because of the little time allowed for recovery.


Feed restriction and growth performance The effects of feed restriction on the performance of broiler chickens are shown in Table1. Feed intake, body weight gain, feed conversion ratio (FCR), and final weight at 1-42 days were not significantly affected by feed restriction. The lack of significant effects of feed restriction systems may be due to the gradual physiological adaptation of the birds to the different feeding regimes which probably improved the efficiency of conversion of the feed available.


Feed restriction and carcass quality The largest and most obvious fat depot is the abdominal fat pad which may comprise up to 4% of body weight. The ab- dominal fat is usually discarded at processing each year, the cost of which is directly or indirectly charged to the consum- er, thereby presenting an additional economic burden. With feed restriction, fat accumulation is reduced (Table 2). This reduction may be explained by two basic mechanisms: 1- Feed restriction results in lower hepatic acetyl-CoA car- boxylase activity, a rate-limiting enzyme for fatty acid syn- thesis. This may limit hepatic triglyceride synthesis causing lower serum triglyceride concentration and hence reduces fat accumulation in the body. 2- Feed restriction influences the recovery of the fat cell number during re-feeding and hence decreases total body fat and abdominal fat contents. In addition to the economic problems associated with the excessive fat formation, the type of fat formed in the carcass


PHOTO: STUDIO KASTERMANS


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28