Starter Diet Composition

Diet composition has a profound effect on how the poult makes the transition to its new metabolic state.[3] Traditional perception by the industry is that fat supplementation should be minimized for starting hatchlings. From a digestibility standpoint, research with feeding of animal fats and animal/vegetable fat blends demonstrates that young hatchlings do not digest saturated fatty acids efficiently. However, unsaturated fatty acids are highly digestible (80 to 85%) and may actually ease the metabolic shift after hatching. Caution should be used, however, as unsaturated fats typically are easily oxidized, rendering the fat rancid. Others may contend that a high proportion of energy from carbohydrate is needed to facilitate a shift in metabolism (from deriving energy from yolk lipid to assimilation of carbohydrate from an external diet). However, when diets containing a high proportion of energy from corn (carbohydrate) are fed, researchers from Ohio State University noted that 30 to 50% of poults fed the carbohydrate-based diet have plasma glucose concentrations above 500 mg/dL 2 days after feeding, which is more than twice the normal concentration.

Because the young poult has a very high crude protein requirement (28%), nutritionists may have a tendency to include much soybean meal in starting diets. However, soybean meal contains a high proportion of nonstarch polysaccharides and is very poorly digested. Therefore,

Year

Fig. 1 Average live body weight of turkey toms (18 weeks) and hens (14 weeks). (From Ref. [1].)

Year

Fig. 1 Average live body weight of turkey toms (18 weeks) and hens (14 weeks). (From Ref. [1].)

prestarter or starter diets containing a high proportion of soybean meal may not provide the required amount of calculated energy and may suppress early growth. In the case of the turkey poult, the initial diet should contain less than 40% of the diet from soybean meal. Typically, formulation will include approximately 5 to 10% fish and/ or meat and bone meal. Several companies are currently marketing specialized diets to be used as the first diet at placement, or in transport boxes before arrival at the farm. These specialized diets are formulated with more easily digested nutrients, such as egg albumin as a protein source, and may also contain mixtures of bacteria (termed competitive exclusion products) to establish a normal microflora and exclude possible pathogens.

NUTRIENT IMPACT ON MUSCLE GROWTH AND QUALITY

Breast meat has become the primary retail product for commercial turkey production, so much nutritional research has focused on maximizing muscle growth and meat quality. Proteins and their component amino acids are one of the primary cost components of turkey diets, but also one of the primary drivers of muscle growth. The turkey industry typically formulates diets based on a crude protein basis, which can supply amino acids in excess of what the animal can either digest or metabolize. As research in this area progresses, however, knowledge of the amino acid digestibility of typical feed ingredients and formulating with an ideal protein ratio (theoretical exact balance of digested amino acids for metabolic needs) will allow greater precision in formulation.[4] This added precision should considerably reduce the amount of nitrogen that is excreted by turkeys.

Additionally, recent nutritional advances have allowed the turkey industry to greatly improve the functional characteristics of turkey meat. For example, supplementation with vitamin E well above nutrient requirements for prevention of classical deficiency symptoms reduces lipid oxidation and improves the shelf life of both raw and ground turkey meat. Furthermore, vitamin E supplementation at higher concentrations in the diet reduces the incidence of pale, soft, and exudative (PSE) meat often encountered in heat-stressed birds.[5] Much of this effect can be related to alterations in glycolytic characteristics during the muscle rigor process. Other feed additives, such as betaine, show promise in aiding osmoregulation during coccidial challenges as well as providing a higher water-soluble methyl donor source, which has demonstrated effects on muscle growth in turkeys.

NUTRITION AND BONE INTEGRITY

Genetic improvements in the growth potential of commercial turkeys have not readily translated into proportional carcass growth and body conformation. For example, leg-associated disorders were a considerable issue for the industry during the late 1980s, until leg-shank width and conformation traits became selection criteria by breeding companies. Today, bone integrity is still a considerable economic issue as companies begin to market larger birds (over 40 pounds) at older ages. Nutritionally speaking, adequate dietary amino acid and protein levels have demonstrated effects on muscle growth, and they are associated with pronounced effects on the lower skeletal axis as well.[6] In fast -growing strains, spiral fractures of the femur occur in small percentages of toms between 16 and 19 weeks of age. Although it is unknown whether there is a nutritional cause, preliminary results suggest a problem in collagen fibril distribution/arrangement, along with areas of lower calcification. Other skeletal issues, such as osteomyelitis complex, are of considerable economic impact to the industry, because carcasses displaying the lesion are condemned due to a high incidence of Staphylococcus aureus. Supplementation with either 1,25 dihydroxy vitamin D3 or 25-hydroxy vitamin D3 improves skeletal integrity and reduces the incidence of osteomyelitis complex during an immune/bacterial challenge.[7]

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