Background last update:6 Aug 2012

Role of betaine in preventing heat stress

Experiments show that the addition of betaine to poultry feed may help to reduce coccidiosis infect ion and heat stress, conditions that both involve cell osmolarity. Nutreco Poultry and Rabbit Research Centre put this theory to the test.

By Henk Enting and Jaco Eissen

Betaine, which is a trimethyl derivate of the amino acid glycine, is found in many cells and has two main physiological functions. First, betaine can serve as a donor of methyl groups. For this reason, the substitution of methionine and choline as a methyl donor by betaine has been subject of many studies. Experiments showed consistently that choline can be

replaced by betaine, but not always indicated that methionine can be replaced by betaine. The latter might be due to the fact that this substitution also depends on the level of cystine in the feed (Eklund et al., 2005). More evidence is coming to light that betaine is a valuable nutrient in itself. A part of this is related to the fact that betaine helps to maintain cellular osmolarity, which is the second main physiological function of betaine.

Stress conditions

A number of experiments show that the addition of betaine to the feeds in particular improves performance under stress conditions that affect cell osmolarity. A coccidiosis infection (Tiihonen et al. 1997; Waldenstedt et al., 1999; Klasing et al., 2001) and heat stress (Zulfiki et al., 2004) are examples of this. It seems that betaine helps to maintain metabolic functions of cells under different types of osmolaric pressure. Furthermore, studies with pigs also indicate an effect of betaine in energy metabolism. Schrama et al. (2003) found a reduction in maintenance requirements when betaine was included in the feed and Huang et al. (2007) demonstrated that betaine increases growth hormone levels significantly. These findings might also stress the importance of betaine as a nutrient itself, rather than possibly replacing part of methionine and choline in feeds.

Due to an increased body weight gain of broiler chickens through the years, temperatures that optimise performance tend to decrease (Gous and Morris, 2005). Earlier performed research indicates that modern broiler chickens are more sensitive to high temperatures and suffer more frequently from heat stress (Lin et al., 2006). Alongside adverse effects of increased

temperatures on feed intake, growth rate and feed conversion ratio, higher temperatures also result in a decreased body protein deposition and in an increased body fat deposition (Geraert et al., 1996). Since betaine can have a positive effect on carcass yield and quality in both poultry (McDevitt et al., 1999; Esteve-Garcia and Mack, 2000; Noll et al., 2002; YiZhen, 2000) and pigs (Campbell et al., 1997; Fernandez-Figares et al. 2002) and due to its effect on cell osmolarity, the addition of betaine to feed or drinking water might help to overcome the negative effects of heat stress on performance and carcass quality (Kidd et al., 1997).

Broiler experiment

In order to test the hypothesis that betaine can improve performance and carcass quality of broiler chickens during heat stress, an experiment was carried out at the Nutreco Poultry and Rabbit Research Centre. The experiment included 300 male and 300 female Ross 308 broiler chickens and was performed from 0-40 days of age. Broilers were housed in floor pens with 25 male or female chickens per pen. Feed and water were provided ad libitum. Heat stress was introduced by increasing the temperature to 35°C for 10 hours a day from 2 days of age on. During the other hours, a standard temperature schedule was followed. The experiment included 3 treatments, in which the same basal feeds with betaine (TNIbetain, Trouw Nutrition International) were provided at 0 (control), 1 or 2 g/kg. Starter feeds were provided from day 0-14 as 2 mm pellets and grower (day 15-31) and finisher (day 32-40) feeds as 3 mm pellets. Amino acid levels in the experimental diets were according to CVB (1996). This indicates that the diets were not limiting in methionine and methionine+cystine. The total analysed choline content in the diets amounted to 2.4 g/kg, which is above requirements (Whitehead and Portsmouth, 1989; NRC, 1994). Effects of the addition of betaine to the feeds would therefore be due to an effect of betaine itself and not to the replacement of methionine or choline. At the end of the experiment, carcass and meat quality was measured for 10 birds per pen.


The addition of betaine to feeds sufficient in methionine, methionine+cystine and choline resulted in significant improvement of the feed conversion ratio in the period from day 0-14 (Table 1). During the entire experimental period, betaine provided an increase in body weight, which was significantly different from the control group for the highest inclusion rate. Feed conversion ratio improved significantly with the highest amount of betaine. No differences in mortality were observed among treatments. The addition of betaine did not affect carcass percentage and abdominal fat percentage significantly. In male broiler chickens, both inclusion levels of betaine provided a significant increase in the percentage of breast meat (Figure 1).

Why it works

The results of this experiment demonstrate that betaine has a positive effect on the performance of broiler chickens and carcass quality. This positive effect of betaine may be related to the osmolyte function of betaine that prevents dehydration. Moreover, a lower maintenance requirement, as was found in pigs when betaine was added to the feed (Schrama et al., 2003), might contribute to a lower heat production, which helps to maintain feed intake and hence weight gain during heat stress as observed in the present experiment. Zulfiki et al. (2004) observed a reduction in body temperature of broiler chickens when betaine was added to the feed under heat stress conditions. Therefore, both the osmolyte effect and the effect of

betaine on maintenance requirements may explain the more pronounced positive effects of betaine on performance and carcass quality during heat stress conditions.

Betaine has been reported to reduce fat composition in non-challenged broiler chickens (Saunderson and MacKinlay, 1990; Hassan et al., 2005). However, this does not seem to be the case in heat-stressed birds as was found by Zulfiki et al. (2004) and in the present experiment. With heat stress, body protein deposition decreases and fat deposition increases due to hormonal changes (Geraert et al., 1996). Results reported by Zulfiki et al. (2004) indicated that betaine may reduce stress hormone levels, which would favour protein deposition over fat deposition. However, these changes are probably not big enough to counteract the negative effects of heat stress on fat deposition. In the present experiment, no clear reduction in mortality was observed when betaine was added to the feed. Zulfiki et al. (2004) reported a reduction in mortality with the addition of betaine to the feed. Mortality in that experiment was clearly higher than in the current experiment (26.5 % in the control group vs. 10.5 % in the present experiment).

Therefore, effects might become more pronounced with higher mortality levels.


Although betaine did not provide a clear reduction in abdominal fat and mortality in the present experiment, it is clear that betaine has a positive effect on broiler performance and carcass quality under heat stress conditions, even when feeds are adequate in methionine,

methionine+cystine and choline. This indicates that betaine is an essential nutrient by itself and is a valuable component in poultry feeds

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