The results of performance in the present experiment suggest that betaine cannot
replace methionine in a methionine de®cient diet. This is in agreement with reports from
Rostagno and Pack (1996) and Schutte et al. (1997) in the sense that the responses to
betaine are small and not signi®cant, and not comparable to those obtained with
methionine. The reason for the discrepancy between these results and those reported by
Virtanen and Rumsey (1996) is not clear since some of the studies reported by the latterinvestigators were done in the presence of coccidial challenge, which reportedly enhances
the response to betaine (Matthews et al., 1995). Zimmerman et al. (1996) did not ®nd any
bene®t of betaine supplementation in the event of a coccidial challenge. It is possible that
the osmoprotective effect of betaine directly in the gut cells could help reduce the damage
caused by coccidia, and the better integrity of the gut lining could lead to more ef®cient
nutrient utilisation and improved performance