Heat Stress: How it impacts feeding behaviour in lactating sows
Heat stress can reduce a sows feed intake, which can result in reduced milk production and therefore have a negative knock-on effect on piglet growth. How can the climate affect the lactating sows feeding behaviour?
BY BRUNO A.N. SILVA, PROFESSOR IN SWINE NUTRITION AND ENVIRONMENTAL ADAPTATION
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uring the past decades, the production of pigs in tropical regions, such as Latin America and Asia, increased intensively. In these regions, production and performance generally remain below those
obtained in temperate countries, such as Europe. Climate is the first most limiting factor for reaching maximum produc- tion efficiency in hot climate regions. While heat stress is an occasional challenge in temperate regions via so-called “heat waves”, in the tropical and subtropical areas it is a constant challenge. In addition, in these regions the effects of high temperatures can be intensified by the relative humidity (RH) of the air. Under heat stress, sows reduce their appetite in order to reduce their heat production due to the thermal effect of feed digestion. This reduction in voluntary feed intake has negative consequences on body reserves, mobilisation, milk production, and future reproductive and productive longevity of the sow. When we consider modern genotypes,
Figure 1 - Daily feed intake during cool and hot season. Feed intake differed between seasons from d 9 to 18 and from d 20 to 24.
climatic effects are more intensified due to high growth rates, deposition of muscle tissue and reproductive potential.
Cool Season Hot Season 12 13 14 15 16 17 18 19 20 21 22 23 24
Understanding feeding behaviour Heat stress can also cause changes on the kinetics of volun- tary intake, feeding pattern and nursing ability of sows, re- ducing total daily intake of sows, reducing breast-feeding time and inducing higher agitation. Under naturally fluctuat- ing temperatures, two peaks of feeding activity occur during 24 h. One peak is observed early in the morning and the oth- er is observed before the beginning of the night. According to Silva et al. (2009a), these observations suggest that the feeding pattern activity of lactating sows is mainly driven by light and temperature intensity changes in the farrowing room. Still in agreement, Gourdine et al. (2006), showed that more than 50% of the total daily feed intake occurred during the nocturnal period during the hot season (64%), as for Silva et al. (2009a) around 44% of daily feed intake occurred during the nocturnal period and that this value was greater in the hot season than in the warm season (47%). Based on data from the previous studies, each degree increase in temperature corresponded to a reduction in daily feed intake of 462 g/d. These results suggest that the negative effect of elevated ambient temperature may be accentuated by the increased RH in a tropical climate. More recently (Silva et al. 2021; Submitted) studied the impacts of climate on modern sows’ voluntary intake and feeding patterns. The study indicated that the daily ingestion time was lower in the hot than in the cool season (36.8 vs. 72.3 min/ d, respectively) and the ingestion time per meal was also lower in the hot compared to the cool season (5.7 vs. 7.5 min/ meal, respectively). The hot season also showed a lower rate of daily intake when compared to the cool season (36.8 vs. 72.3 g/ min, respectively). The ratio between voluntary feed intake and the required daily feed intake based on the sows daily nutrient needs was also lower for the sows during the hot season (66 vs. 90% for hot and cool season). In addition, we also observed that irrespective of season, sows showed a higher diurnal feed intake (3.430 vs. 2.750 g/ d). On a daily comparison of feed intakes or variations from day to day, sows during cool season showed a higher voluntary feed intake from d 9 to d 24 compared to the hot season (Figure 1). The nycthemeral voluntary feed intake pattern peaked twice daily (within 24 h) irrespective of the season. The two peaks
▶ HEAT STRESS | MAY 2021
Voluntary Feed Intake, kg/d
PHOTO: AMANDA LELIS UFMG
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