Understanding the Role of the Skeleton in Egg Production - Hy-Line ...

Technical Update – UNDERSTANDING THE ROLE OF THE SKELETONfor up to 10 weeks after birds that meet orexceed ideal body weights. Therefore whilemost of the flock may be laying at 96%, the 5%of the flock that is underweight may be layingsporadically (or not at all) and will reduce thepeak production percentage. Stressors thatmay be avoided include moving, injectingwith inactivated vaccine, wide ranges ofenvironmental conditions inside the house,poor feed quality, crowding and any otherabrupt changes in routine.Crowding in the pullet house usually startsto affect birds at approximately 10-12 weekswhen the skeleton is near full size. Crowdedpullets will have issues with uniformity andbody weight gain until transfer. Refer to thePerformance Standards Manual for rearingspace recommendations.Measuring body weight gain and uniformityis an excellent method for tracking flockgrowth throughout pullet growing. Higherbody weights result in larger skeletons andmore muscle mass which leads to betterproduction. Waiting to light stimulate untiltarget weights are met is the most effectivesolution to ensure good persistency of layand avoid a post-peak dip in production.Monitoring body weights every week shouldnot stop at transfer. It is ideal to weigh everyweek up to 32 weeks of age and at least every2 to 4 weeks until the end of lay. This practicewill give an indication if nutrient intake issufficient to support production, growth, andmaintenance requirements of the bird.SEXUAL MATURITY IN THE LAYING HENAbout two weeks prior to egg production, thehen will undergo sexual maturity. An increaseof estrogen will stimulate development of theoviduct, reddening of the comb and wattlesand a complete transition from buildingskeletal bone to building medullary bone.To aid the growth of medullary bone beforethe first egg, it is recommended to introducemore calcium through the use of a Pre-LayDiet. Constantly improving genetics provideproducers with layers capable of very highpeaks of lay and good persistency. To ensurethat genetic potential is reached, buildingmedullary bone and formulating diets withsufficient nutrient density to meet the dailyrequirements of the bird is very important.However, there can be a negative impact onfeed consumption from the sudden increasein dietary calcium levels of 1% to above 4% atthe start of lay. Field experience indicates thatthe use of Pre-Lay Diets helps as a transitionbetween the Developer and the Peaking Diet.Correct feed formulation and matching dietdensity with consumption will minimize theimpact of reduced calcification of bone overthe laying cycle and extend the persistency ofshell quality.BONE QUALITY DURING PRODUCTIONThe length and width of the poultry skeletonis complete when the hen has started tolay. However, the bone mineral densityand content, as well as the ratio of cortical,trabecular and medullary bones can changedramatically. The laying hen skeleton isstrongly influenced by level of egg production,diet formulation in relation to consumptionand disease status. A well-grown laying henwill typically not face skeletal issues until afterpeak, even with mild to moderately deficientdiets. With an underweight laying hen, nutrientdeficiency will more quickly affect flock results.Mild to moderate nutrient deficiencies willusually cause skeletal and/or shell qualityissues first with production issues following.Severe nutrient deficiency will still causenoticeable and rapid drops in production.Many animals, including birds, experiencethinning of the cortical and trabecularbone thickness with age. Laying hens alsoexperience changes in overall bone strength.Although medullary bone is the most labilebone type, if a hen is calcium deficient, corticaland trabecular bone will also be mobilized asa calcium source. During the laying period,hens have been shown to have a net increasein bone mass as a result of medullary boneformation and the loss of structural bone.However, without a molt or cessation ofproduction due to nutrient deficiencies, theconstant high level of estrogen in a laying henwill prevent the repair of structural bone. Lossof cortical bone can result in crooked keel orbone fractures, both of which are detrimentalto hen welfare and production.As birds age, medullary bone content willincrease while structural bone integritytypically decreases. Birds that lose too muchcortical bone and gain medullary bone canhave good shell quality, but are at a higherrisk for keel curvature or bone fracture. The

IN EGG PRODUCTIONbest way to minimize the loss of cortical boneis to ensure that the correct levels of calcium,phosphorus and vitamin D 3 are fed throughoutthe lay cycle.#1 – Normal KeelPreventing loss of skeletal integrity starts withthe pullet, but continues through the life ofthe bird. It is also important to understand theclinical signs of osteomalacia, osteoporosisand osteopenia and make the appropriatechanges as soon as possible.MONITORING SKELETAL INTEGRITYThe best way to minimize the impact ofsoft bones in a flock is to monitor regularly.Handling birds while weighing is the ideal wayto collect this information. Select birds fromthe same cage, colony or section of the barn atleast every 4 weeks to ensure consistency ofdata and provide early notice if crooked keelsare observed.• Keels are scored by feel and observation.The Hy-Line method is to score on a fourpoint scale based on normal (#1), mild (#2),moderate (#3) or severe (#4) curvature.• At the beginning of calcium, phosphorusor vitamin D 3 deficiencies, keels may beflexible, but not yet curved. This is animportant clinical sign to note.• Hens with recalcified, curved keels wouldindicate a nutritional deficiency earlier inthe life of the flock.• It is ideal to handle a minimum of 10 birdsin at least 2 to 3 areas of a barn.#2 – Mild Curvature#3 – Moderate CurvatureOverall, it is ideal to have greater than 90%of birds handled in the Score 1 or Score 2category. More than 10% Score 3 or Score4 birds, or increasing numbers every week,indicate the possibility of an issue.#4 – Severe Curvature

Technical Update – UNDERSTANDING THE ROLE OF THE SKELETONNUTRITIONFeed consumption and nutrition always gohand in hand. All diet formulations must bebased on feed consumption to ensure properintake of the critical nutrients. As a result, allHy-Line diets are recommended on the basisof total daily feed intake. Focusing on calciumand available phosphorus, as examples, theHy-Line Brown and Hy-Line W-36 need toconsume the following amounts each day inher ration:above 3.5 mm (3500 micron), the solubilityrapidly decreases. If the hen is not effectivelyabsorbing the calcium in the diet, she can bedeficient (even with an accurate “calculatedvalue” of the ration).Additionally, the source of limestone shouldbe checked. Low calcium content limestone(less than 37%) may contain other mineralsthat reduce the solubility (and therefore thecalcium availability). Depending on geologicalPeaking Diet Lay Diet #2 Lay Diet #3 Lay Diet #4Hy-LineBrownHy-LineW-36Hy-LineBrownHy-LineW-36Hy-LineBrownHy-LineW-36Hy-LineBrownHy-LineW-36Calcium (g/day) 4.00 4.00 4.40 4.20 4.70 4.35 4.90 4.50Available Phosphorus (mg/day) 440 500 400 480 360 460 350 400Attaining the required levels for thesenutrients is significantly dependant on dailyfeed consumption. A sample calculation fora bird recommended to have 4.00 grams ofcalcium per day and with an observed feedconsumption of 95 grams is as follows:4.00 g calciumneeded x 10095 g feed consumedLimestone particle size is also important foroptimum shell quality. Pullets should have fineparticle calcium, ideally less than 1.1 mm (1100micron) average. It is best to use limestoneflour for pullets as the smaller particles aremore easily absorbed.Layers should ideally receive a 50:50 ratio oflarge and fine particle limestone at the start oflay and transition to a 70:30 ratio (large: fine)by the end of lay. Changing the particle sizeensures that more calcium will be available atnight from the diet instead of from the bone.Further measures to increase night calciumavailability include ensuring a last feeding1 – 2 hours before lights are turned off andadjusting the feeding regime to 40% in themorning and 60% in the afternoon.The large particle fed during lay shouldbe around 2 – 4 mm (2000 – 4000 micron)average size with an ideal 3 mm (3000micron) size. When calcium particle size is=4.21% calciumin the dietformation, different limestone structuresexist which may also affect solubility andavailability.Phosphorus intake is similarly calculated,although the requirement definition is morecomplex due to different systems used toexpress available and digestible phosphorus.Care needs to be taken that requirements andthe availability matrix are being expressedon the same system. There are ongoingprojects in the US and the EU to review thephosphorus nutritional systems and create amore universal standard.The use of phytase enzymes must beconsidered when formulating the diet. Phytaseis an important tool in reducing both thecost and environmental burden of animalfeeding; however care needs to be taken whenapplying matrix values. Matrix contributionsneed to be accurate for the phytase beingused, the diet in which it is being used and thedosage being applied. The matrix contributionmust not exceed the concentration of phytatephosphorus potentially available for release.This differs by phytase source, inclusion rateand the ingredient makeup of the diet.Vitamin D 3 (cholecalciferol) is a critical nutrientthat aids in calcium and phosphorus uptakein the small intestine, bone mineralization,inhibition of calcium excretion in the urineand immune system modulation. Vitamin Dis typically included in the feed as vitaminD 3 . It is absorbed in the small intestine and

IN EGG PRODUCTIONconverted to 25-hydroxycholecalciferol in theliver. This metabolite is then converted to theactive form of 1, 25-hydroxycholecalciferolin the kidneys. In addition to vitamin D 3 ,there are commercial products that contain25-hydroxycholecalciferol which cut down ona conversion step in the hen and have a higherbiological value.Other dietary factors are also important toconsider in the efficiency of bone calcificationand eggshell formation. This includes the acidbase balance of the diet (or dietary electrolytebalance - DEB), vitamin K, zinc, copper, iron,manganese and magnesium. Some essentialamino acids which are often limiting in layingdiets (valine and arginine) may be importantdue to their role in calcium transportation andformation of the bone matrix.FEED CONSUMPTIONConsumption volumes at the start of laychange quickly; for example, the Hy-LineBrown eats 80 – 90 g/day at the start of lay andsoon eats 110 – 115 g/day in about 4 – 6 weeksat peak production. Often, feed mills may onlyhave one Peaking Diet that is formulated for110 – 115 g/day intake for brown birds and100 – 105 g/day for white birds. When intakeat the start of lay is only 80 – 90 g/day, therewill be deficiencies of 20 – 25% in calcium,phosphorus, essential amino acids and othernutrients. Creating a diet matrix can helpensure that the correct dietary formulationis used. Not all diets will be used, but it willsimplify ordering feed for a farm.The bird is still growing until about 32 weeksand is adding muscle mass and bone density.If there are deficiencies in the diet, the impactmay not be immediate, but can be felt latein lay when hen body reserves have beendepleted.DISEASENutritional issues are usually the primarycause for decreased skeletal integrity andresulting shell quality problems. However,many subclinical respiratory and entericdiseases may have the same effect. A decreasein feed consumption or nutrient absorptioncan have a dramatic impact on shell and bonequality as described previously. Bacterial, viralor protozoal pathogens may cause temporaryor permanent damage to the intestine andreduce the absorption of key nutrients. Theduodenum in particular is the location in theintestine where calcium is actively absorbedin response to increased demand underhormonal influence involving vitamin D 3 .Diseases such as focal duodenal necrosis candamage the duodenum and may decrease theefficiency of absorption. Additionally, there aremany diseases that cause shell quality issuesby affecting the oviduct, including infectiousbronchitis, Newcastle disease, Mycoplasmasynoviae, egg drop syndrome (EDS) and avianinfluenza.PeakingDietLayDiet #2LayDiet #3LayDiet #4Daily Feed Consumption90 g/day x95 g/day100 g/day x105 g/day110 g/day x x x x

ACTIONS WHEN SKELETAL ISSUES AREIDENTIFIEDDuring routine handling, if soft bones orcrooked keels are detected during lay, thereare steps that can be taken to correct the issue.General – should only be used until specificmeasures can be taken• Add water-soluble vitamin D 3 or25-hydroxycholecalciferol to the drinkingwater 1 – 2 times a week to increasecalcium and phosphorus metabolism• Add 2 – 4 mm large particle limestone oroyster shell to increase the level of calciumin the gizzard overnight and providecalcium for egg shell and strengtheningbones.• Review, and if necessary, increase the levelof available phosphorus in the diet to helpwith bone strength and metabolismSpecific• Verify or determine feed consumption ofthe flock• Check the feed formula to ensure thecorrect amounts of calcium, phosphorusand vitamin D are specified• Ensure that the daily levels of consumptionmeet the dietary needs of the hen• Send feed samples for analysis todetermine if calcium and total phosphoruslevels are consistent with formulatedvalues. When sampling, it is important toobtain a representative sample of the feedto minimize sampling error. A standardprocedure for collecting accurate feedsamples is to collect multiple sub-samplesand mix them together. Use a portion ofthis mixed sample to send in for analysis.• If a deficiency is found, work with the feedmill to prepare the correct formulationbased on daily consumption• Check the flock to see if there are anydisease issues that are minimizingabsorption or reducing feed consumptionEnsuring good skeletal development fromrear into lay through best management andnutritional practices is essential to reachthe genetic potential of the Hy-Line layer.Understanding the importance of the skeletonin laying hen production will help producersimplement best practices. Formulating the dietto consumption and monitoring the skeletalquality will create the environment to attainthe best and most economical production.Hy-Line International| www.hyline.com© 2013 Hy-Line International