Trends to decrease the age of sexual maturity and point of lay without concurrent increases in dietary Ca may reduce the potential for full skeletal mineralization in pullets. During lay, the henâs increased genetic capacity to produce more eggs with less feed without respective increases in dietary Ca may further predispose hens to bone weakness leading to welfare and livability issues. Objectives of this research were to evaluate the effect of feeding increased calcium during rearing and the lay cycle as well as strain and density on laying hen performance and bone mineralization status. Pullets were grown to 16 wks in a grow house with 52 pullets/replicate and 28 replicates/treatment (5,824hens total) which were then moved to a lay house from 18-66 wks with either 24 or 36 hens/replicate (at 48 or 64 sq in) so that there was a total of 26 replicates/treatment (5,728 hens total). The 2 x 2 factorial arrangement of treatments during rearing were Leghorns strain: Hy-Line W-36 (H) and Babcock B-300 (B) and Ca:P ratios: elevated (RC+) Ca:P 2.14, 3.14, 4.14 and control (RC) Ca:P 2.14, 2.14, 2.42 ratio of starter (0-6 weeks), grower (6-12 weeks), and developer (12-17 weeks), respectively. In the lay cycle, the 2 x 2 x 2 x 2 factorial consisted of strain, rearing diet, layer dietary regimens: increasing Ca and P (LC+) and constant (LC) and cage densities: low, 64in2/bird (LD) and high, 48in2/bird (HD). All diets were isocaloric and fed ad libitum. Feed consumption (FC) and BW were monitored bi-weekly (by period) beginning at 2 weeks of age during the rearing and every 4 weeks during the layer phase. Mortality and egg production was recorded daily. During rearing, 5 femurs/trt and during laying, 3 femurs/trt were measured for dry fat-extracted bone weight (DFEW), % ash, volume, and bone breaking strength (BBS) from week 6-16 and from weeks 51-61, respectively. From week 0-17, FC was higher (Pâ¤0.01) when feeding RC+ (5.11 kg) than RC (4.81 kg) otherwise there was no effect on Gain (1,017 and 1,029 g, respectively, P=0.53) or FE (0.199 and 0.214, respectively, P=0.08). Strain had no effect on FC, Gain, or FE. Mortality increased (Pâ¤0.03) by period in the B compared to H strain. Layer performance was not affected by feeding the increased calcium during rearing or lay. Strain effected (Pâ¤0.05) feed consumption, feed efficiency, egg production, and mortality. Feeding more Ca during rearing increased DFEW (RC+=0.94 g vs. RC=0.82 g, P=0.04) while strain effected bone volume (H=2.99 and B=2.37 cc, Pâ¤0.01) and femoral BBS (B=8.55 vs. H=7.80 kg, P=0.01) of pullets. Feeding more Ca during lay did not effect bone status, but feeding it during rearing increased BBS (RC+=14.15 vs. RC=12.37 kg, Pâ¤0.01) in older layers. Strain effected (Pâ¤0.001) both BBS (H=14.26 vs. B=12.26 kg) and volume (H=5.90 vs. B=6.27 cc). These findings indicate that feeding increased Ca during rearing and laying impacts bone mineralization and may be a useful strategy to mitigate bone weakness and such related conditions as cage layer osteoporosis.
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-03272009-155748 |
| Date | 01 May 2009 |
| Creators | Fosnaught, Mary Helen |
| Contributors | Donna Carver, Jesse Grimes, James Petitte, Ken Anderson |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-03272009-155748/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dis sertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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