TY  - THES
T1  - Effects of a reduction of dietary levels of calcium and phosphorus on performance, bone minerals and mineral excretion of turkey breeder hens in the rearing and laying period
A1  - Gickel,Julia Maria
Y1  - 2023/03/07
N2  - Phosphorus (P) is an essential mineral in feed for livestock and has finite resources all over the world. The aim of this study was to obtain an idea about the reduction potential of P in the diets of turkey breeders. As the metabolism of P is interlinked with the metabolism of calcium (Ca), Ca was also examined. Therefore, the requirements of P and Ca were studied using a factorial approach. As data about the requirements of these minerals in turkey breeders is limited, the present study mostly used data from other poultry species. Thus, this study can be viewed as an approach to building new resilient data for turkey breeder hens.
The results of the factorial approach were embedded in a feeding program for turkey breeder hens during rearing and laying with two different treatments. One group was fed a standard feed (practical diet used before the trial), while the other group was fed a Ca/P reduced feed. In total, four trials were conducted: trials I and III focused on the rearing period while trials II and IV focused on the laying period. All trials were observed independently but the hens from trial I were used also in trial II afterwards for studying long-term effects. In each trial, body weight and feed intake were measured throughout the trial period. Bone mineralization was studied in trial I, including analyses of bone ash as well as Ca and P in the bone ash from the tibia of fallen and culled animals. The egg components were studied in eggs from trial II, including analyses of the percentages of albumen, egg yolk, and egg shell; Ca in albumen; P in albumen; Ca in egg yolk; P in egg yolk; water in egg shell; Ca in egg shell; and P in egg shell. In trials II and IV, laying performance, egg weights, number (and causes) of culled eggs, fertility, hatchability, as well as body weight and fitness of the hatchlings were additionally observed. At the end of each trial, the concentrations of dry matter, Ca, and P in manure were analyzed and a nutrient balance was calculated to classify the results.
Body weight development exhibited significant differences between the treatments in eight out of 30 weeks in trial I (five weeks had a higher mean weight in the group with standard feed; three weeks had a higher mean weight in the group with Ca/P reduced feed); three out of 28 weeks in trial II (two weeks had a higher mean weight in group with Ca/P reduced feed; one week had a higher mean weight in the group with standard feed); four out of 30 weeks in trial III (higher mean weight in the group with Ca/P reduced feed); and two weeks out of 28 in trial IV (higher mean weight in the group with Ca/P reduced feed).
The feed intake data also fluctuated, with three out of 30 weeks exhibiting a significant difference in trial I (higher mean feed intake in the group with Ca/P reduced feed) and one week with a significant difference in trial II (higher mean feed intake in the group with standard feed). The observations throughout all of the trials revealed the tendency for a higher mean feed intake in the groups with Ca/P reduced feed.
A significant difference concerning bone mineralization was not observed. Moreover, the results of laying performance, fertility, and hatchability exhibited no differences between the treatments.
Regarding the egg weight in trial II, there were eight weeks with a significant difference between the treatments (seven weeks with a higher mean egg weight in the group with standard feed; one week with a higher mean egg weight in the group with Ca/P reduced feed). In trial IV, only one week exhibited a significant difference between the treatments (higher mean egg weight in the group with Ca/P reduced feed).
Regarding the weight of hatchlings in trial II, three weeks had a significant difference between the groups (higher mean weight in the group with standard feed). In trial IV, no significant difference was observed for any week all throughout the trial period.
The analyses of egg components revealed significant differences between the treatments according to the percentages of albumen and egg yolk and the calculated value of total Ca in the egg (including the shell).
In trials I and III, significant differences existed between the treatments in the concentration of Ca in manure, with a lower level in the group with Ca/P reduced feed.
This study concluded that a reduction in the dietary levels of Ca from 1.00–1.10% to 0.56–0.80% and of P from 0.48–0.61% to 0.35–0.50% (av. P) or 0.70–0.80% to 0.50–0.60% (total P) in rearing and a reduction of the dietary levels of Ca from 2.90% to 2.80% or 2.60% and of P from 0.36% to 0.30% or 0.24% (av. P) or from 0.65% to 0.50% (total P) in laying in the feed of turkey breeder hens are possible and did not result in disadvantages. As the present study also compared the results with required recommendations and target levels from breeding companies, it was also able to conclude that these levels are obsolete and should be adjusted downwards.
KW  - Phosphor, Tierernährung
KW  - Elterntiere
CY  - Hohenheim
PB  - Kommunikations-, Informations- und Medienzentrum der Universität Hohenheim
AD  - Garbenstr. 15, 70593 Stuttgart
UR  - http://opus.uni-hohenheim.de/volltexte/2023/2132
ER  -