Liquid feeding does not suppress drinking motivation in heavy pigs

The experiment aimed to obtain information on the water requirements, drinking behavior and drinking motivation of liquid-fed pigs and was conducted during the hot season. Eighty castrated male pigs (initial body weight: 36 kg) fed a liquid diet (water:feed ratio of 3:1), capable of guaranteeing the fulfilment of the theoretical water requirements, were assigned to two experimental groups either receiving drinking water via nipple drinkers (CON, Control) or having non-functioning drinkers available (RW, Restricted Water). The availability of extra water did not affect the pigs' growth parameters (ADG - average daily gain, DMI -dry matter intake and FCR -feed conversion ratio) nor the quality of the carcasses and meat, including the sensory properties of hams cured over 18 months. Similarly, no significant differences were found in the lesions detected in the body and stomach surfaces and the neutrophils to lymphocytes ratio. Also, general behavior was not modified by the treatment except for the percentage of observed time spent drinking, which was significantly higher in the CON pigs (0.42 vs 0.21%; P<0.01) and resulted in a greater water consumption (13.54 vs. 7.39 l/day; P<0.01) that increased sharply as animal age and environmental temperature increased. Additionally, even though their drinkers did not dispense water, the animals in the RW group maintained some motivation to use the drinkers throughout the trial. The apparent lack of effect of prolonged water rationing on most of the parameters observed and, on the other hand, the evident impact of fresh water supply on drinking behaviour warrant more specific measurements applicable to farm conditions that may help identify animals suffering from prolonged thirst.