Effects of graded noise levels on behavior, physiology and production performance of intensively managed lambs

Abstract

The aim of the experiment was to assess the effects of graded noise levels on behavioral, immune and cortisol respons-  es, and on production performance of forty precocious Merino lambs. The experiment lasted 42 days and was preceded  by a two-week adjustment period. The animals were divided into 3 test groups and a control group of 10 each, which  were housed in 12 m2 sound-proof rooms. The lambs in the test groups were exposed to recordings of high-speed motor  vehicle traffic noise for 8 hours a day. The frequency range of the recordings was 100 to 6,300 Hz, while the loudness  levels were different in the three experimental rooms: group A = 95 dB, group B = 85 dB, and group C = 75 dB. During  the same 8 hours the control group was exposed to a background noise of 42-44 dB. For the rest of the day, the ambi-  ent noise level in the animal building was 35-40 dB. Behavioral traits of lambs were recorded at the end of the adjust-  ment period and then at 14d, 28d and 42d of the experiment. At the same intervals, the plasma levels of glucose, total  cholesterol, triglycerides, total proteins, albumins and cortisol were determined. Cell-mediated immune response to phy-  tohemagglutinin (PHA) was determined at the beginning and at days 21 and 42 of the trial. Live weights of lambs were  measured at the beginning of the trial and then at two-week intervals during the trial. After slaughtering, the carcass  weights and the dressing percentage were determined. The experimental treatment determined a significant increase in  the walking time (P   42 of the trial in groups A and B. The lambs in the test groups exhibited a slower growth rate (P   mals of the control group, whereas a deterioration of feed efficiency was observed only in group A (P   no differences amongst the groups in terms of cell-mediated immunity and blood metabolites. Results suggest that expo-  sure to noise has a detrimental effect on some biological functions in lambs but it does not severely impair animal well-  being, at least when there are no concomitant conditions of physical and social discomfort. 

Keywords

• Lambs, Noise, Behavior, Cortisol, Production performance