Wheat

Nutritional Characteristics:

Wheat is commonly used in many countries as the major energy source in poultry diets. There is often confusion regarding the exact type of wheat being used, because wheats are described in a number of different ways. Traditionally wheats were described as being winter or spring varieties and these were usually grown in different regions because of prevailing climate and soil conditions. Wheats are sometimes also referred to as white or red, depending upon seed coat color, and finally there is the classification of hard vs soft. In the past, most winter wheats were white and soft, while spring wheats were hard and red. In terms of feeding value, the main criterion is whether wheat is soft or hard, because this will have an effect on composition, and especially on protein. Because of developments in plant breeding, the seed color and time of planting can now be more variable. Hard wheats have a greater proportion of protein associated with the starch and so contain more protein that is also higher in lysine. The proteins in hard wheat are useful in bread making, while the soft wheats are more useful in manufacture of cookies and cakes. Durum wheat used in manufacture of pasta is a very hard wheat. The physical hardness of these wheats is due to the strong binding between starch and the more abundant protein.

Varietal differences based on 'hard' vs 'soft' varieties seem to have inconsistent effects on AME and amino acid digestibility. A more consistent varietal effect is seen when genes from rye are translocated into wheat ostensibly to improve baking characteristics. These translocated wheat varieties (often termed 1B ^ 1R) have 10% lower amino acid digestibility and in the case of lysine, the differences may be as much as 18% in favor of the non-translocated varieties.

As with corn, the grading system for wheat relates to bulk density and the proportion of broken grains and foreign material. For #2 grade there is a maximum allowable inclusion of 5% foreign material and broken kernels. Feed grade wheat can have over 20% broken kernels and foreign material.

The composition of wheat is usually more variable than that of other cereals. Even within the hard wheats, protein level can vary from 10 to 18%, and this may relate to varietal differences and variance in growing conditions. Most hard wheats will not have to be dried after harvest, although drying conditions and moisture content of wheat at harvest appear to have little effect on feeding value. Environmental temperature during growing seems to have a major effect on wheat nitrogen content, and although high temperature can result in 100% increase in nitrogen level, the relative proportion of both lysine and starch tend to be decreased.

Depending upon the growing region, frost damaged or sprouted wheat is sometimes available to the feed industry. Frost damage effectively stops starch synthesis, and so kernels are small and shrunken. While 100 kernel weight should be around 27 g, with severe frost damage, this can be reduced to 14 - 16 g. As expected, the metabolizable energy level of this damaged wheat is reduced and under these conditions, there is a very good correlation between bulk density and metabolizable energy. For non-frosted wheat, however, there does not seem to be the same relationship between energy level and density.

Wheat will sometimes sprout in the field. Sprouted wheat would probably be rejected simply based on appearance, although research data suggests that metabolizable energy level is only reduced by 3 - 5%. There are no problems in feeding sprouted wheat, as long as it has been dried to □ 14% moisture, and can be economical if discounted accordingly. Wheat contaminated with 'rust' however seems to more seriously affect feeding value, and metabolizable energy value can be reduced by up to 25%.

While wheats are much higher in protein content compared to corn, and provide only slightly less energy, there are some potential problems from feeding much more than 30% in a diet, especially for young birds. Wheat contains about 5 - 8% of pentosans, which can cause problems with digesta viscosity, leading to reduced overall diet digestibility and also wet manure. The major pentosan components are arabinoxylans, which are linked to other cell wall constituents, and these are able to adsorb up to 10 times their weight in water. Unfortunately, birds do not produce adequate quantities of xylanase enzymes, and so these polymers increase the viscosity of the digesta. The 10 - 15% reduction in ME of wheats seen with most young birds (<10 d age) likely relates to their inability to handle these pentosans. Variability in pentosan content of wheats per se likely accounts for most of the variability of results seen in wheat feeding studies, together with our inability to predict feeding value based on simple proximate analyses. These adverse effects on digesta viscosity seem to decrease with increased storage time for wheats. Problems with digesta viscosity can be controlled to some extent by limiting the quantity of wheat used, especially for young birds, and/or by using exogenous xylanase enzymes (see Section 2.3 g).

Wheats also contain a-amylase inhibitors. Although these inhibitors have not been fully identified, they are thought to be albumin proteins found predominantly in the endosperm. These inhibitors can apparently be destroyed by the relatively mild temperatures employed during pelleting. Compared to corn, wheat is also very low in levels of available biotin. Whereas it is sometimes difficult to induce signs of biotin deficiency in birds fed corn diets devoid of synthetic biotin, problems soon develop if wheat is the major cereal. While newly hatched chicks have liver biotin levels of around 3,000 ng/g, this number declines to 600 ng/g within 14 d in the wheat fed bird. Adding just 50 |g biotin/kg diet almost doubles the liver biotin reserve, while adding 300 |g/kg brings levels back to that seen in the day-old chick. There is also concern that wheat causes a higher incidence of necrotic enteritis in broiler chicks. It seems as though wheat provides a more suitable medium for the proliferation of certain pathogenic bacteria. The problem is most severe when wheat is finely ground, and incidence of necrotic enteritis can be tempered by grinding wheat through a roller mill rather than a hammer mill. Fine grinding of wheat can also cause beak impaction in young birds. The proteins in wheat tend to be 'sticky', and so adhere to the beak and mouth lining of the bird. Severe beak impaction tends to reduce feeding activity, increase feed deposited in open bell drinkers, and provides a medium in the mouth region that is ideal for bacterial and fungal growth. These problems can be resolved by coarse grinding of wheat.

Using wheat in diets for meat birds does however improve pellet durability. The same proteins that enhance the baking characteristics of hard wheats, also help to bind ingredients during pelleting. Adding □ 25% wheat to a diet has the same effect as including a pellet binder in diets that are difficult to pellet.

One advantage of wheat, is that it can be fed as whole grain to birds after 10 - 14 d of age. Offering whole wheat and a balancer feed with adequate minerals and vitamins provides a very economical way for farmers to utilize home-grown wheat. In recent studies we offered broilers a conventional three diet program, or after 7 d of age, a choice between whole wheat and crumbled broiler starter through to 49 d. From 7 - 21 d, male broilers voluntarily consumed about 15% of their ration as wheat, while from 21 - 35 d and 35 - 49 d this increased to 34% and 41% respectively. Table 2.3 shows performance data of these birds. Body weight was only slightly depressed, although carcass weight was significantly reduced and breast yield was reduced by about 10%. The free-choice wheat system did however show a saving of 10% in feed cost per kg liveweight gain although feed cost per kg of breast meat was not different. Another advantage claimed for feeding whole wheat to broilers is greater control over coccidiosis. Whole wheat feeding stimulates gizzard and gastric motility and the enhanced activity within this acidic environment is thought to reduce oocyte viability.

Potential Problems:

Wheats contain variable quantities of xylan, which is poorly digested and results in wet viscous excreta together with poor digestibility. As detailed in section 2.3g, this problem can be overcome by using synthetic xylanase enzymes. Feeding much more than 30% wheat can lead to beak/mouth impaction that can reduce feeding activity. Such material building-up in the mouth can be a site for mold and mycotoxin development. This problem can be resolved by grinding wheat more coarsely. With wheat as the major cereal, there is need for greater levels of supplemental biotin, since biotin availability in wheat has been reported to be as low as 0 - 15%.

Table 2.3 Broiler performance with free-choice wheat

Diet

Body Wt

Feed:Gain

Protein

Energy

Carcass Wt

49d (g)

Intake

Intake

(g)

(g/kg Bwt)

(kcal/kg Bwt)

Control

3030

1.93

370

6044

2230b

Free-choice wheat

2920

1.99

364

6106

2135a

Adapted from Leeson and Caston, 1993

Adapted from Leeson and Caston, 1993

Pregnancy Diet Plan

Pregnancy Diet Plan

The first trimester is very important for the mother and the baby. For most women it is common to find out about their pregnancy after they have missed their menstrual cycle. Since, not all women note their menstrual cycle and dates of intercourse, it may cause slight confusion about the exact date of conception. That is why most women find out that they are pregnant only after one month of pregnancy.

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