Evaluation of feed additives Nutrifen® and NutrifenPLUS® on broiler performance
Thesis (MScAgric)--Stellenbosch University, 2018.
ENGLISH ABSTRACT: The main aim of this study was to determine the effects of feed additives Nutrifen® and NutrifenPLUS® on broiler performance over a period of 32 days. Two separate experiments were conducted; one to determine toxicity/safety of the additives, and another to measure a number of performance parameters relevant to the industry that may be affected by different concentrations of additive. In the case of the toxicity trial, a total of 60 Cobb500 mixed gender broilers were fed treatment diets containing 0% additive, 0.4% Nutrifen®, 0.4% NutrifenPLUS®, 0.2% Nutrifen®, 0.2% NutrifenPLUS® and 0.015% Zinc Bacitracin as the positive control. Birds were subsequently slaughtered at 14 days of age and analysed for gizzard erosion using a four point scoring system. No significant differences between treatments were reported in terms of gizzard erosion, implicating that both additives are non-toxic in this regard and safe to use at the specified levels. The main study was conducted using 360 mixed gender Cobb500 broilers with four treatment diets and a positive and negative control. Each treatment consisted of six replications and diets contained the following concentrations of additives: 0.2% Nutrifen®, 0.2% NutrifenPLUS®, 0.1% Nutrifen®, 0.1% NutrifenPLUS®, 150g/ton zinc bacitracin, and a negative control. All diets during both trials were maize and soya based, and formulated according to commercial specifications. Similarly, all birds were housed in the same facility and under the same environmental conditions according to Cobb500 guidelines, which were monitored closely throughout the house. Performance was determined as a function of three main areas of commercial significance, namely production parameters (live weight, feed intake, feed conversion ratio, European production efficiency factor, protein efficiency ratio, average daily gain and mortality), organ and tibia bone characteristics (absolute and relative organ weights, liver colour CIE-Lab colour meter, intestinal pH, tibia bone breaking strength), as well as meat quality and carcass characteristics (carcass weight, dressing percentage, commercial cut proportions, proportions of breast components, muscle colour using a CIE-Lab colour meter, and pH and chemical composition of breast muscle). No significant differences were observed with regard to any production parameters and in terms of meat quality and carcass characteristics, very few parameters differed significantly between treatments. Only redness (a*) of the breast muscle and meat fat percentage showed any statistical differences, with supplementation of 0.2% NutrifenPLUS® and 0.2% Nutrifen® reducing the values of each parameter respectively, relative to the negative control. Similarly, no significant differences were reported in terms of organ weights or liver colour, and tibia bone characteristics showed few statistically significant differences. Only one tibia bone parameter was affected significantly by treatment; this being the calcium:phosphorus ratio measured from the bone ash. Supplementation with 0.1% NutrifenPLUS® differed significantly from both control diets, and 0.2% NutrifenPLUS® produced a significantly lower ratio relative to all other treatments.
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