NUTRITION ▶▶▶


Apart from other strategies, skip-a-day feed- ing, intermittent lighting pro- grammes and feed supple- mentation can help to alleviate SDS.


vitamin K (1, 5 and 10 mg/kg) were added to the diets fed to broiler chickens. There were fewer deaths due to SDS among the broilers fed diets containing 10 mg/kg of vitamin K. The incidence of SDS was also reduced by the inclusion of ad- ditional vitamins. Biotin supplementation of 33 mg/kg in the diet reduced the incidence of SDS compared with diets where biotin was not supplemented. Excessive intake of vitamins A, D, E, C and niacin were found to be associated with a variety of metabolic lesions and ad- versely affect heart performance, leading to an increased risk of heart failure and SDS in broilers. Over-supplementation may be attributed to the fact that some vitamins, such as A, D, and E, are added to diets on the assumption that the feed is deficient in these without prior analysis. Consequently, it is quite probable that some vitamins are occurring in the diet at excessive levels, hence leading to SDS.


Feed processing Pelleted feed is extensively used in the broiler industry and has many advantages. It reduces bulk, minimises waste and destroys toxins during the pelleting process and is more di- gestible compared with the mash form of feed. Pelleted feed, however, increases the growth rate and thus also the inci- dence of SDS. It has been suggested that one or more toxic factors are created when protein supplements are subjected to pelleting which may be involved in causing SDS. The toxin is produced when soybean meal is pelleted but not when meat meal is pelleted. Thus the inclusion of meat meal sup- plies a previously unidentified factor found in animal protein which provides some protection against SDS. In some reports, the etiology of SDS has been associated with thermal feed processing. Thermal processing increases the number of mutagenic heterocyclic amines which


30 ▶ POULTRY WORLD | No. 3, 2020


experimentally produce foci of chronic inflammation with myocyte necrosis, mitochondrial swelling and vacuolisation, along with a distortion of the banding pattern and DNA dam- age in the cardiomyocytes; all factors contributing to the incidence of SDS.


Feed restriction Feed restriction will reduce mortality due to SDS. A mortality level of 0% has been reported for feed-restricted birds com- pared with 3.3% under ad libitum feeding. Strategies to de- crease growth and metabolic rate to some extent and hence alleviate the incidence of SDS, as well as improve feed con- version in broiler chickens include: Skip-a-day feeding, inter- mittent lighting programmes and feed supplementation. The skip-a day feeding works best when used for three weeks starting at 1 day-old. This method can improve carcass quality and reduce SDS which is often associated with birds that are on ad libitum feed intake. The use of intermittent lighting pro- grammes (1 hour light: 3 hours dark from 8 to 49 days) has the advantage of reducing the incidence of SDS compared with the continuous lighting schedule (23 hours light: 1 hour dark), with no reduction of weight at market age. In the area of additives, one study noted that the use of 50g/ kg of calcium propionate as an appetite suppressor resulted in weight gains in birds close to those obtained under a rec- ommended programme of quantitative feed restriction be- tween 2 to 6 weeks of age. Glycolic acid has also been used as a chemical means of restricting the feed intake of broilers. The feed intake of birds fed on diets supplemented with 1.5% and 3% glycolic acid was depressed by 17% and 45%, respec- tively. The reduction in body weight gain resulting from the chemical restriction of feed intake was recovered at 49 days of age.


PHOTO: PETER J.E.ROEK PENTALUX PHOTOGRAPHY & VIDEO


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