Effects of Different Hay Feeders, Availability of Roughage on Abnormal Behaviors and Cortisol Circadian Rhythm in Horses Kept in Dry Lots

Free choice forage could be the best option regarding horses' welfare but can lead to increased body weight (BW), and waste of hay. Automatic box feeders (BF) and slow feeders (SF) decrease food waste, but it is unknown how these affect the horses' time -budget (TB). This study compared the effects of feeding free choice hay (FC), to a SF and an automated BF on the horses' cortisol circadian rhythm (CCR) and behavior by 24-hours continuous behavioral sampling (CBS). The study was designed as a 3 x 3 Latin square design with 15 polo horses divided into 3 groups, for 15 days on each treatment. Every 15 days, BW was assessed, blood collected for CCR analysis, the behavior recorded during the last 24 hours of the last day of each treatment and the video analyzed with CBS. Time spent on all behaviors was evaluated and used for the determination of the animals' TB. The effects of the different feeders were analyzed with ANOVA. FC horses consumed and wasted more hay daily (16.6 +/- 0.5kg) ( P < .001), compared with BF (10.4 +/- 0.5 kg), and SF (9.30 +/- 0.45 kg). FC horses had higher weight gain ( P < .001, 23.5 +/- 4.6kg), compared to BF (1.2 +/- 5.7 kg) and SF (0.37 +/- 4.6) kg. FC and SF horses spent more than 50% of the TB foraging, generating a TB similar to grazing horses. BF horses spent less time eating ( P < .001), increasing time spent standing, sniffing the ground, and practicing coprophagy ( P < .050). BF horses showed the highest aggression ( P < .043). CCR was not different among treatments. (c) 2023 Elsevier Inc. All rights reserved.