Influence of limestone particle size in layer diets on shell characteristics at peak production

[摘要] English: A study was conducted to investigate the influence of different particle sizes of aspecific amorphous limestone source (calcium carbonate) in a layer diet on eggproduction and egg quality at peak production (week 24).Ninety nine layer pullets, 17 weeks old, were obtained from a commercial layerbreeder. The pullets were randomly allocated to three groups. All the pullets receivedthe same layer diet. The only differences among the treatment groups were that thepullets in each group received one of the three different particle sizes in the dietnamely:-(a) Less than 1.0 millimetre(b) 1.0 and 2.0 millimetre(c) 2.0 and 3.8 millimetreThe influence of the three particle sizes on the feed intake, body weight and eggproduction as well as egg characteristics was recorded.The average weekly feed intake, body weight and egg production of layers from week18 up to 28 were not (P> 0.05) different among the layer diets with the differentparticle sizes. The particle size of limestone in the layer diets did not influence eggweight (P= 0.2159) and egg output (P=0.2388) significantly at peak production.Average egg weight tended (P= 0.2159) to be heavier when coarse particles were fed.No statistic al significant (P> 0.05) differences in egg volume, egg contents, eggsurface area, shell weight per unit surface area, shell percentage and shell thicknessoccurred. According to these results limestone particle size in layer diets has noinfluence on eggshell quality.In the second study the effect of particle size distribution of a specific limestonesource in layer diet on egg production and egg quality at peak production (week 24)was investigated. One hundred and sixty seven layer pullets , 17 weeks old, were obtained from acommercial layer breeder. The pullets were randomly allocated to five groups. All thepullets received the same layer diet. The only differences among the treatment groupswere that the pullets in each group received one of five different ratios of fine (lessthan 1.0 mm) and coarse (between 2.0 and 3.8 mm) limestone particle size namely100, 75, 50, 25 and 0 % fine or coarse. The influence of the five dietary limestoneparticle size distributions on the feed intake, body weight, and egg production oflayers as well as egg characteristics mentioned in the first study were investigated.No significant (P> 0.05) influence of dietary limestone particle size distribution wasfound on feed intake, body weight and egg production of layers. Accordingly nosignificant differences occurred in egg volume, (P= 0.1310) and egg surface area (P=0.1393). The highest (P< 0.001) egg contents were recorded where 100 and 75% finelimestone particles were included in the diet. Although significant differences forshell weight (P<0.0017) and shell percentage (P<0.0001) occurred, no clear influenceof particle size distribution on these characteristics could be detected.In accordance wit h shell weight per unit surface area no significant differences (P>0.05) in eggshell thickness occurred.It was concluded that different dietary limestone particle sizes and distributions haveno influence on eggshell quality at peak production (week 24). The influence ofdietary limestone particle size and distribution during the later stages of the layingperiod on bone formation and egg quality needs further investigation.

[发布机构] University of the Free State