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Result and Discussion

Body mass

Body mass did not differ between the CTRL and the SKIP in either 9 or 12 weeks of age which would mean that the SKIP animals grow in agreement with the CTRL. This was predicted as the SKIP group were managed to achieve the same growth curve as CTRL and got more food in total. 

Body mass (g) for 9 weeks old (A) and 12 weeks old (B) broiler breeder chickens subjected to daily feed restriction (CTRL), and chickens subjected to a 5:2 feed restriction regimen (SKIP)

Novel object (NO) and tonic immobility (TI) 

Fasting animals significantly approached the NO more, and seemingly stayed shorter times in TI although not statistically significant, meaning that SKIP animals are interpreted to be less fearful on fasting days.

These results have been reported in other studies, where the degree of feed restriction decreases fearfulness (Hocking et al., 2001; Savory et al., 1993)

In order to get statistical significances between the groups in TI, more animals needs to be tested in future research. 

Novel object (NO) differences over time for 9 weeks old (A) and 12 weeks old (B) broiler breeders between every-day feed restricted (CTRL) and 5:2 feed restricted chickens divided into days with feed (SKIP Feed) and days off-feed (SKIP Fast) with sampling during the morning (AM) and the afternoon (PM).
Kaplan-Meier Survival plot of tonic immobility (TI) first head movement for 9 weeks old (A) and 12 weeks old (B) and TI duration for 9 weeks old (C) and 12 weeks old (D) broiler breeder chickens subjected to every-day feed restriction (CTRL) and a 5:2 feed restriction regimen divided into days of feeding (SKIP Feeding) and days of fasting (SKIP Fasting).

Activity

The CTRL were more active than SKIP regardless of feeding or fasting day or age, and were especially active around feeding (7 AM).

Activity differences over time measured in average motion watch (MW) counts per 15 min between 9 weeks old broiler breeder chickens subjected to daily feed restriction (CTRL) and a 5:2 feed restriction regimen on days with feed (SKIP Feed; A) and days without feed (SKIP Fast; B) and 12 weeks old broiler breeder chickens on days with feed (SKIP Feed, C) and days without feed (SKIP Fast; D). * = P ≤ 0.05, ** = P ≤ 0.01, *** = P ≤ 0.001.

Could be explained by high food competition for the CTRL chickens as they were provided with less food than SKIP chickens and that SKIP chickens had habituated to their regimen. 

Glucose, liver mass and glycogen

Fasted animals had lower plasma glucose levels. The glucose concentration decreased for CTRL over the day but increased for the SKIP on feeding days.

Average glucose concentrations for broiler breeder chickens at 9 (A) and 12 (B) weeks of age subjected to daily feed restriction (CTRL) and a 5:2 feed restriction regimen divided into days with feed (SKIP Feed) and days without (SKIP Fast) with differences between morning samplings (AM) and afternoon samplings (PM). Different lettering in bars indicate significant difference.

On feeding days, the liver mass and total glycogen level for the SKIP group were significantly higher.

Liver mass (A) and total liver glycogen (B) differences between daily fed (CTRL) and 5:2 skip-a-day broiler breeder hens on days with feed (SKIP Feed) and on a fasting day (SKIP Fast). Different lettering in bars indicate significant difference.

These results indicate that SKIP animals store energy as glycogen in the liver to utilize later on, which would also explain the higher glucose level of SKIP in the afternoon on feeding days. 

H/L ratio

SKIP birds had higher H/L ratios at 12 weeks of age compared to CTRL birds. Both SKIP birds and CTRL birds had high H/L ratios when comparing with references of stress (0.5).

Mean ± SD for H/L ratios of 9 weeks and 12 weeks old broiler breeder chickens subjected to daily feed restriction (CTRL) and a 5:2 feed restriction regimen (SKIP)

This result means that both the CTRL and the SKIP were stressed in the study.


Responsible for this page: Agneta Johansson
Last updated: 05/17/16