Limestone particle size in layer diets

Abstract

English: A specific calcitic limestone source that is widely used in South African poultry diets was evaluated during two concurrent studies. During the first study, the effect of limestone particle size on bone quality, egg production and eggshell quality was determined. Limestone was classified according to particle sizes as small (0-1.0 mm), medium (1.0-2.0 mm) and large (2.0- 3.8 mm). During the second study, the effect of different distribution ratios of small and large particle sizes of limestone on bone quality, egg production and eggshell quality characteristics was determined. Small (0-1.0 mm) and large (2.0-3.8 mm) particles limestone from the first study were mixed to obtain the following five distribution ratios used in the second study namely; 0, 25, 50, 75, 100% small or large particles. The experimental protocol for both studies was the same. Initially one hundred and thirty eight, 17 weeks old Lohmann-Silver pullets, were obtained from a commercial egg producer and randomly allocated to six treatments (n=23/treatment). All birds were kept in individual metabolic cages for the duration of the study. The influence of limestone particle size and distribution ratios of particles on feed intake, body weight and egg production was determined for weeks 33 up to week 70 of age. During weeks 54, 58, 62 and 70 of age, the effect of limestone particle size and distribution ratios of particles on eggshell quality characteristics such as shell weight, percentage eggshell, eggshell calcium egg surface area, shell weight per unit surface area (SWUSA) and shell thickness was determined. At 70 weeks of age, the effect of limestone particle size and distribution ratios of limestone particles on bone dimensions (length, width and weight), bone mechanical properties (breaking strength and stress) and percentage bone ash was determined. The results of the limestone particle size study indicated that different limestone particle sizes did not have a significant influence on feed intake (P=0.6229), body weight (P=0.4189), egg production (P=0.3991), egg output (P=0.0599) and feed conversion ratio (P=0.5025). Accordingly different limestone particle sizes did not show any significant effect on mean eggshell characteristics such as shell weight (P=0.9396), percentage eggshell (P=0.3468), eggshell calcium (P=0.9367), egg surface area (P=0.3223), SWUSA (P=0.6111) and shell thickness (P=0.6663) during the entire experimental period. At 70 weeks of age large particles limestone resulted in a significant higher tibia bone breaking strength (P=0.0107) and stress (P=0.0391). No significant (P>0.05) influence of limestone particle size was found on bone length, width, weight, percentage ash and index at week 70 of age. The results of the second study illustrated that different ratios of small and large limestone particles had no significant effect on feed intake (P=0.4066), body weight (P=0.8908), egg production (P=0.2713), egg output (P=0.1457) and feed conversion ratio (P=0.2635) during the entire experimental period. No statistical differences were detected due to a mixture of different ratios of coarse and fine limestone particles on mean eggshell characteristics such as shell weight (P=0.6902), percentage egg shell (P=0.7297), eggshell calcium (P=0.6903), egg surface area (P=0.4474), SWUSA (P=0.7738) and eggshell thickness (P=0.7167) during the entire experimental period. It was concluded that the different limestone particle sizes and ratios of small and large particles limestone in the diets used during the present study, generally had no significant influence on bone and eggshell quality characteristics of Lohmann-Silver laying hens during the later stages of lay, except on bone mechanical properties.

Afrikaans: ‘n Spesifieke kalsitiese kalksteenbron wat algemeen in Suid-Afrika in pluimveerantsoene gebruik word, is tydens twee gelyklopende studies geëvalueer. Tydens die eerste studie is die invloed van partikelgrootte op beenkwaliteit, eierproduksie en eierdopkwaliteit bepaal. Die kalksteen is volgens partikelgrootte as fyn (0-1.0 mm), medium (1.0-2.0 mm) en grof (2.0-3.8 mm) geklassifiseer. Tydens die tweede studie is die invloed van partikelgrootte-verspreiding van fyn en growwe kalksteenpartikels op beenkwaliteit, eierproduksie en eierdopkwaliteit bepaal. Fyn (0-1.0 mm) en growwe (2.0-3.8 mm) kalksteenpartikels van die eerste studie is met mekaar gemeng om die volgende vyf partikelgrootte-verspreidings van 0, 25, 50, 75 en 100% fyn of growwe partikels te verkry. Die eksperimentele prosedure vir beide studies was dieselfde. Een honderd agt en dertig, Lohmann-Silver lêhenne (17 weke oud), is vanaf ‘n kommersiële eierprodusent verkry en ewekansig in ses behandelings ingedeel (n=23/behandeling). Die invloed van partikelgrootte en partikelgrootte-verspreiding op voerinname, liggaamsgewig en eierproduksie is vanaf week 33 tot 70 ouderdom bepaal. Gedurende die ouderdom van week 54, 58, 62 en 70 is die invloed van partikelgrootte en partikelgrootte-verspreiding op eierdopkwaliteit-eienskappe soos dopgewig, persentasie dop, kalsiuminhoud, eieroppervlakte, eierdopgewig per eenheid oppervlakte en eierdopdikte bepaal. Gedurende week 70 is die invloed van partikelgrootte en partikelgrootteverspreiding op been-metings (lengte, dikte en gewig), meganiese-eienskappe (sterkte en spanning) en persentasie been-as bepaal. Die resultate van die kalksteen partikelgrootte studie het geen betekenisvolle invloed op voerinname (P=0.6229), liggaamsgewig (P=0.4189), eierproduksie (P=0.3991), eieruitset (P=0.0599) en voeromset-verhouding (P=0.5025) getoon nie. Ooreenkomstig het verkillende kalksteen partikelgroottes geen betekenisvolle effek op gemiddelde eierdopeienskappe soos eierdopgewig (P=0.9396), persentasie eierdop (P=0.3468), eierdopkalsium (P=0.9367), eieroppervlakte (P=0.3223), dopgewig per eenheid oppervlakte (P=0.6111) en dopdikte (P=0.6663) gedurende die eksperimentele periode uitgeoefen nie. Op 70 weke ouderdom het growwe partikelgrootte kalksteen ‘n betekenisvolle hoër tibia breeksterkte (P=0.0107) en - spanning (P=0.0391) tot gevolg gehad. Geen betekenisvolle (P>0.05) invloed van partikelgrootte op beenlengte, -breedte, -gewig, -persentasie as en -indeks is op week 70 waargeneem nie. Die resultate van die partikelgrootte-verspreidingstudie het geïllustreer dat verskillende verhoudings van fyn en growwe kalksteen partikels geen betekenisvolle effek op voerinname (P=0.4066), liggaamsgewig (P=0.8908), eierproduksie (P=0.2713), eieruitset (P=0.1457), en voeromset-verhouding (P=0.2635), gedurende die eksperimentele periode uitgeoefen het nie. Geen betekenisvolle verskille as gevolg van ‘n mengsel van fyn en growwe kalksteen is op die gemiddelde eierdopeienskappe soos dopgewig (P=0.6902), persentasie eierdop (P=0.7297), eierdopkalsium (P=0.6903), eieroppervlakte (P=0.4474), dopgewig per eenheid oppervlakte (P=0.6111) en dopdikte (P=0.7167) gedurende die eksperimentele periode waargeneem nie. Daar is tot die slotsom gekom dat verskillende kalksteen partikelgrootte en partikelgrootteverspreiding van fyn en growwe kalksteen in die dieet wat tydens die huidige studie gebruik is, oor die algemeen been- en eierdopkwaliteit van Lohmann-Silver lêhenne gedurende die laat lêperiode, met die uitsondering van meganiese-beeneienskappe, nie betekenisvol beïnvloed het nie.