Bioacoustics is the study of the production, transmission and reception of sounds emitted by animals. Most animal welfare studies aim to reduce potential negative experiences from the farm environment that could threaten animal health by allowing improvements to be made to environmental factors such as light, noises, flock density, facilities, disease prevention, to define all those stress factors that could negatively affect animal welfare.

One of the most relevant and first stress factors to which newborn broilers are subjected is the prolonged fasting caused by the routine practices to which they are subjected in the hatcheries before reaching their destination in the farms. Prolonged deprivation of water and feed has long-term negative effects on the health and behavior of the chick, affecting its growth and the correct functional development of the gastrointestinal system.

The objective of this preliminary study is to simulate fasting during the first two days of life (48 hours) of newborn chicks in a control group without early feeding and a second group administered a complementary gel feed, Licuicel® Complex, to assess the improvement in the health and welfare of the birds in both groups. Acoustic measurements have been made analyzing and comparing the difference in acoustic patterns between the two groups using metrics to empirically detect the health status of the animals, relating it to the hematological results obtained.

Vocalization
After the first 46 hours of the study, the sound of each group was recorded in two separate and identical rooms from the hour 46 to 48 uninterrupted to study the variations of the vocalizations.

The Licuicel® (LIC) group in Figure 1 presents vocalizations with a lower range (about 250Hz) compared to the Control group (CON), the duration of the call is substantially longer, and it presents a more serious centroid of energy (3 .7 KHz) and greater than the CON group.

Figure 1. Comparison of spectral vocalizations at 48h, CON and LIC groups.

Acoustic indicators of well-being
The temporal repetition frequencies of chick calls can be an indicator of stress when there is a high number of repetitions of vocalizations. Previous studies have found a correlation between the maximum frequency of vocalization and feed intake (lower frequency when more feed is eaten). As well as the maximum frequencies of vocalization of the entire productive cycle are observed during the first three days of life on the farm, probably due to transport stress.

Obtaining lower values of temporal repetitions and maximum frequency or pitch are objective indicators of less stress and consequently improved animal welfare.

Figure 2. Vocalization frequency results and temporal repetition of vocalizations.

Licuicel® Complex

Figure 2 shows how the group that has been administered with Licuicel® Complex reduces the frequency of vocalization (on average –7.36%) and reduces the number of temporal repetitions even more significantly (on average –13, 88%).

Hematological analysis
In the results obtained from the hematological analysis, two statistically significant parameters stand out and may be correlated with the acoustic data obtained. These parameters are the hematocrit value and the monocyte count (See Figure 3).

The hematocrit values obtained in the LIC group are lower than those of the CON group.

Figure 3. Hematocrit value and monocyte count at 48 hours, CON and LIC groups.

These results suggest that water deprivation, which results in dehydration, causes changes in blood parameters, particularly hematocrit values, which increase abnormally when the animal is unable to maintain homeostasis.

In addition, several studies confirm that the stress caused by prolonged fasting causes a significant reduction in the number of monocytes compared to chicks that have access to a nutritional source immediately after hatching.

Conclusions
The analysis of the LIC group, birds fed with the complementary feed Licuicel® Complex, presents indicators that show a certain reduction in stress, both in correlation with the acoustic and hematological analysis. In both groups, the only difference is the application of a complementary feed, suggesting that the improvements in animal welfare and stress reduction detected in this study could be due to the administration of Licuicel® Complex.