Poultry Flashcards
Outline the principles of feeding management of growing pullets
§ In most situations, variable management conditions influence energy needs so important to relate all other nutrients to energy level
§ Hot climates, pullet eats less so nutrients such as amino acids (AA) need to be increased accordingly
§ Pullets grown on floor, rather than in cages, eat more, so AA levels can be decreased
§ Strain-specific diets in growing white and brown egg pullets
o Induced by differential growth rates and/or different mature body weight
§ Significant differences in vitamin-mineral premixes suggested for various strains of commercial pullets
§ BW and perhaps body composition major factors influencing egg size at maturity and throughout remainder of laying period
o BW main factor controlling early egg size, but still insufficient evidence regarding
optimum body structure and composition
o Birds having some energy reserve as they approach peak egg production seem to be less prone to subsequent production problems
§ Important to schedule diets according to body weight (BW) and condition of the flock rather than according to age
o For smaller pullet there is a degree of compensatory growth up to time of first egg, although insufficient to allow for total catch-up growth
§ Because BW controls feed intake (FI) and egg size, easier way of manipulating life-cycle egg size is through manipulation of mature body size
o If maximum possible egg size desired, aim to realise largest possible mature weight
o Where smaller overall egg size economical than smaller pullet desirable - obtained by growing them more slowly (or most easily by light-stimulating them at an earlier age)
o Heaviest pullets likely first to mature and produce first egg
§ If these birds still being fed grower diet (1% Ca) they will only have sufficient Ca reserve to produce 2-3 eggs. At this time, they are likely to stop laying, or less frequently continue to lay and exhibit cage layer fatigue. If they do stop laying it will be for 4-5 d and then try to start process again
§ Prelay diets provide more Ca (2-2.5% Ca) than grower diets (1% Ca), but still not enough Ca for sustained production
o Should not be fed beyond 1% egg production
§ In terms of Ca metabolism, most effective management program is feeding layer diet as it allows sustained production of early maturing birds.
Why is an adequate medullary bone reserve of Ca important in egg production?
Adequate medullary bone reserve of Ca is important to maintain shell quality. The bird’s skeleton contains approximately 1 g of medullary Ca (highly unstable secondary bone in marrow cavities of bones) available for shell calcification on any one day. This Ca is continually replenished between successive ovulations, and in times of inadequate Ca repletion, the medullary reserve may be maintained at the expense of structural cortical bone.
Should daily intake be increased or decreased as the layer hen ages?
The daily intake of Ca should be gradually increased (and the daily intake of P deceased) as the bird ages. As the egg gets larger (as occurs as hens age), the shell gets thinner and becomes more prone to breakage, so to maintain egg shell quality, Ca intake needs to be increased. In addition, the proportion of large particle limestone should be gradually increased to ~70% of supplementary limestone.
Why is large particle form Ca important in layer hen nutrition?
This ensures that during the night when birds are depositing the egg shell, Ca is present in the gastro- intestinal (GI) tract and available for absorption and egg shell deposition. Small particle limestone travels through the GI tract in 2-3 h. If no Ca is available in the GI tract when the bird is forming eggshell, the Ca is instead taken from the skeletal system. Over time this leads to the loss of skeletal integrity, poor shell quality and increased rate of layer fatigue.
What are the potential benefits to poultry of feeding whole wheat grain
Whole wheat grain is suitable for feeding birds over 10-14 d of age. It provides greater control over coccidiosis, which can be major issue with broilers and also non-caged layers and pullets. Whole wheat feeding stimulates gizzard and gastric motility and the enhanced activity within this acidic environment is thought to decrease oocyte viability. Whole wheat feeding also overcomes the issues associated with the feeding of finely ground wheat, i.e., beak/mouth impaction leading to decreased FI.
What are the potential benefits to poultry of Inclusion of large particle form (2-3 mm) supplemental Ca in pre-lay diets
This ensures that during the night when birds are depositing the egg shell, Ca is present in the GI tract and available for absorption and egg shell deposition. Small particle limestone travels through the GI tract in 2-3 h. If no Ca is available in the GI tract when the bird is forming eggshell, the Ca is instead taken from the skeletal system. Over time this leads to the loss of skeletal integrity, poor shell quality and increased rate of layer fatigue. In the pre-lay diet, half of all supplementary dietary Ca should be supplied in large particle form (2-3 mm).
What are the potential benefits to poultry of direct substitution of fats (2%) for cereal grains (2%) in poultry rations during periods of heat stress
This not only increases energy intake but also reduces the specific dynamic effect of the diet, which helps birds to cope better with heat stress. High fat content of the diet helps to reduce heat production, since fat has a lower heat increment than carbohydrate (or protein).
How and why does particle size and feed form impact on the productivity of both layers and broilers?
The impact will vary depending on the feed ingredient, thus this question is best answered by providing examples.
The type of processing of wheat has implications on bird health. Feeding > 30% finely ground wheat (in the diet) can lead to beak/mouth impaction leading to decreased feeding activity. The build-up of feed in the mouth is a site for mould and mycotoxin development. These problems can be resolved by grinding wheat more coarsely. Wheat can also be fed as a whole grain, especially to birds after 10- 14 d of age. Another advantaged 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 decrease oocyte viability.
For maize, there seems to be some benefits of using finer grind for birds up to 3 weeks of age, while coarse grind is better for birds > 21 d of age.
Sorghum is vulnerable to hydrothermal processes therefore any processing which involves heat and moisture, such as steam-pelleting, steam-flaking and wet-extrusion, may lead to undesirable physico- chemical changes. Dry-extrusion may enhance starch digestibility by gelatinising starch. Combining reducing agents with hydrothermal processes may enhance the solubility and digestibility of sorghum protein by either cleaving disulphide linkages or preventing their formation.
During heat stress, changing the texture of the diet may also assist in maintaining or stimulating feed intake. Crumbles or large particle size mash feeds tend to stimulate intake. A sudden change from large to small feed particles also has a transitory effect on stimulating intake; however, a sudden change from small to large crumbles seems to have negative effect on intake.
What are the potential adverse effects to poultry of including > 30% finely ground wheat in the diet.
Feeding > 30% finely ground wheat (in the diet) can lead to beak/mouth impaction leading to decreased feeding activity. The build-up of feed in the mouth is a site for mould and mycotoxin development.
What are the potential adverse effects to poultry of beta-glucans (found in barley).
Beta-glucans bind with water in the intestines, increasing the viscosity of the intestinal contents. An increase in viscosity of the digesta adversely affects the digestion and absorption of nutrients. It is suggested that the increased viscosity reduces the mixing of intestinal contents, alters the transport properties of nutrients at the mucosal surface, or both. The viscous nature of digesta can also result in wet manure
What are the potential adverse effects to poultry of inadequate dietary Ca in pre-lay rations.
To ensure optimal medullary bone development in early maturing birds, the pre-lay diet should contain 2.5-2.75% Ca. The bird’s skeleton contains approximately 1 g of medullary Ca (highly unstable secondary bone in marrow cavities of bones) available for shell calcification on any one day. This Ca is continually replenished between successive ovulations, and in times of inadequate Ca repletion, the medullary reserve may be maintained at the expense of structural cortical bone. Failure to achieve target Ca (and available P) intake at the onset of production results in cage layer fatigue and poor shell quality for the life of the flock.
What are the potential adverse effects to poultry of inadequate dietary Ca in layer rations.
Egg shell contains around 2 g Ca of feed origin, with a portion of this cycling through the medullary bone. The quantity of medullary Ca reserves is maximal when the bird is around 30 weeks, and the slight negative balance over time contributes to the decreased shell quality in older birds. If there is inadequate Ca, there is an almost immediate loss in shell integrity. If the deficit is large, ovulation often ceases and thus there is no excessive bone resorption. However, with marginal deficiencies ovulation often continues and birds rely more heavily on bone resorption. Total medullary bone Ca reserves are limited and so after the production of 3-4 eggs on marginally Ca deficient diet, cortical bone may be eroded with associated loss in locomotion. As the Ca content of the diet decreases there is a transient (1-2 d) increase in feed intake, followed by a decrease associated with decreased protein and energy needs for egg synthesis. Egg production and egg shell quality return to normal within 6-8 d after the birds receive a diet adequate in Ca. After 3 weeks on the Ca adequate diet, their legs bones are completely recalcified.
What are the potential adverse effects to poultry of phenolic compounds, such as condensed tannins (found in sorghum).
Diets containing < 5% CT typically result in decreased growth rates, low protein utilisation, damage to the mucosal lining of the digestive tract, alteration in the excretion of certain cations, and increased excretion of proteins and essential AA. In poultry, small quantities of CT in the diet cause adverse effects; 0.5-2.0% can cause decreased growth and egg production as well as intestinal damage whilst 3-7% CT in the diet normally results in death of birds. Tannins are most detrimental when fed to young birds, especially when the protein content of the diet is marginal. Tannins seem to increase the incidence of leg problems, especially in broiler chickens, although the exact mechanism is unknown.
What are the potential adverse effects to poultry of phytate
Phytate is the predominant form of P in cereal grains, oilseeds and legumes. Poultry utilise this form of P poorly. Phytates can chelate with di- and trivalent mineral ions such as Ca2+, Mg2+, Zn2+, Cu3+ and Fe3+ resulting in these ions becoming unavailable. The adverse effect on mineral availability depends on a number of factors including phytate concentration and the strength of its binding with different minerals.
Briefly discuss feeding strategies to reduce the impact of heat stress in both later hens and broilers.
Layers
Often during hot weather higher energy density diets are fed; however, the ability of birds to consume the appropriate amount of feed to meet their energy requirements is a mechanism that is less than perfect. At high temperature birds adjust their feed intake and “overconsumption” of energy occurs in response to the increased feed energy level. This ‘overconsumption’ may lead to increased heat increment. Using supplemental fat may be a better alternative as it will increase palatability of the feed and it has a lower heat increment produced during its utilisation.
Feed intake may be maintained during hot weather by manipulation of feeding programs such as feeding more times each day or feeding at cooler times of the day. Under extreme environmental conditions it is worth considering ‘midnight’ feeding. Making the diet more palatable may also assist in maintaining feed intake. Vegetable oil, molasses or even water encourages intake.
Changing the texture of the diet may also assist in maintaining or stimulating feed intake. Crumbles or large particle size mash feeds tend to stimulate intake. A sudden change from large to small feed particles also has a transitory effect on stimulating intake; however, a sudden change from small to large crumbles seems to have negative effect on intake.
Options for broilers § changing the levels of nutrients § change in ingredient composition § change in time of feeding; and § in extreme situations, removal of feed.
Decreasing CP by 2-3% whilst maintaining levels of methionine + cysteine, lysine and threonine may be beneficial. Decreasing CP decreases the heat increment related to transamination, deamination and excretion of N.
It is common practice to increase dietary energy by direct substitution of 2% fat for 2% of major cereal. This practice not only increases energy intake but also reduces the specific dynamic effect of the diet, which helps birds to cope better with heat stress. High fat content of the diet helps to reduce heat production, since fat has a lower heat increment than carbohydrate (or protein).
Although vitamin C is not an essential nutrient for chickens, the addition of 1 g ascorbic acid/L drinking water for 3-5 d during a heat wave has been shown to be effective.
Several acid-base imbalances occur in heat-stressed broilers. The addition of ammonium chloride, potassium chloride and/or sodium bicarbonate has been shown to improve broiler performance by improving water and feed intake.
Feed management options include withdrawing feed from 10 am to 5 pm, thus stimulating feed intake during the cooler parts of the day. It is important to ensure there is adequate feeder space and drinkers. Adding 0.5% salt to drinking water may stimulate water intake (and effect cooling) and it is also important to keep drinking water as cool as possible.
What treatment regime would be appropriate when decreased shell quality is associated with increased cage layer fatigue mortality?
When decreased shell quality is associated with increased cage layer fatigue (consequence of loss of structural bone in the vertebrae that leads to spinal bone collapse and paralysis) mortality the following cage layer fatigue treatment should be implemented
- Week 1: increase dietary Ca level by 0.60% and available P by 0.14%
- Week 2: increase dietary Ca level by 0.30% and available P by 0.07%
- Week 3: normal diets or 0.15% increase in dietary Ca level and 0.035% increase in available P.
What treatment regime would be appropriate when decreased shell quality is not associated with an increase in cage layer fatigue mortality?
When the decrease in shell quality is not associated with an increase in cage layer fatigue mortality the recommendation is to increase dietary Ca by 0.30%, and add additional vitamin D3 in the feed and water (2500 IU/L drinking water for 7 consecutive days and two separate days per week thereafter).
Discuss nutritional factors associated with lameness in poultry.
The modern broiler has been selected for its rapid growth, increased muscle and heavier breast weight. These characteristics may also be associated with poor leg health and lameness, being attributed to decreased bone quality, with cortical bones having lower mineralisation. Lameness is negatively related to final weight at slaughter and may be associated with high flock mortality. The highest incidences of lameness consistently occur in the fastest-growing broiler flocks. In broiler diets, Ca is commonly provided by limestone; when included at high concentrations it can decrease P digestibility and this may lead to decreased skeletal integrity.
Lameness may also be linked with keel bone fractures in laying hens. The incidence of keel bone fractures in layers has increased in the past decade, and is now reported at high levels in all housing systems. The high vulnerability of the keel bone to fracture during the laying period may be due to the demands of high egg production interfering with skeletal strength and integrity. The incidence and severity of keel bone fractures are generally low or non-existent at the start of lay, but increase rapidly as birds reach peak production. Dietary alpha-linolenic acid has been shown to markedly reduce the occurrence of keel bone fracture in laying hens.
List the major nutritional factors (dietary factors) and feeding practices that can result in the production of wet litter in poultry enterprises/Discuss appropriate nutritional strategies (ingredient selection and inclusion levels, feed processing and feeding practices) to minimise the incidence of wet litter in poultry enterprises.
Soybean meal contains high concentrations of K and α-galactosides that have been associated with increased water intake and wet litter and an increase in the prevalence of FPD.
Nutraceuticals such as probiotics, prebiotics, or enzymes improve intestinal integrity and improve faecal consistency and litter quality.
Dietary electrolyte (Na, K and Cl) balance is an important factor influencing excreta moisture. In particular, high dietary levels of Na and K as well as high dietary electrolyte balance increase water intake and litter moisture.
High dietary Na concentration (0.30%) can enhance water consumption and litter moisture.
Dietary protein is an important dietary factor influencing litter quality, as excessive protein in a bird’s organism is metabolised to uric acid and in this form excreted. For this reason, water consumption and litter moisture in birds increase with an increasing content of protein in the diet.
Low energy diet increased litter moisture due to a higher feed intake.
Addition of Mg to the diet of broilers, irrespective of the Mg source, linearly increased the excreta moisture content.
