Mexican sunflower foliage is a valuable fodder for ruminants, due to its high protein content and relatively high digestibility and degradability (Gallego-Castro et al., 2014; Mahecha et al., 2005). However, the expression of this potential requires supplementation with fermentable carbohydrates to improve rumen microbial growth, and/or to increase the supply of bypass protein (Pathoummalangsy et al., 2008). Most studies of Mexican sunflower foliage have involved sheep and goats.
In Venezuela, a series of comparisons of the palatability for cattle, sheep and goats of 11 tropical fodders showed that Tithonia diversifolia had a moderate palatability, much lower than that of Chlorophora tinctoria and white mulberry (Morus alba) for all three livestock species. It was less palatable than Leucaena leucocephala but as palatable as Gliricidia sepium for cattle and sheep, though Leucaena and Gliricidia were more palatable to goats. These differences may be explained by the presence of secondary metabolites such as polyphenols, terpens and saponins (Garcia et al., 2008a; Garcia et al., 2008b; Garcia et al., 2008c; Garcia et al., 2009a; Garcia et al., 2009b).
Digestibility and degradability
Tithonia diversifolia foliage was found to have a high in sacco DM degradability with values well above 75% when harvested after 70 days of growth (Rosales, 1996; Mahecha et al., 2005; La O León et al., 2008; Naranjo et al., 2011). The highest DM degradability was recorded between 70 and 90 days (La O León et al., 2008). A lower value for effective DM degradability was reported from Nigeria (63%), but this value was still comparable to that reported in the same paper for Gliricidia and higher than those of tropical grasses (Osuga et al., 2006). In vitro DM digestibility was also high (71-75%), with only a slight decrease between 60 and 120 days of growth (Verdecia et al., 2011). In vivo DM digestibility was variable, with reported values ranging from 57 to 74% (Nguyen Van Sao et al., 2010; Nguyen Thi Thu Hong et al., 2013; Pathoummalangsy et al., 2008). Methane production from a mixture of Tithonia diversifolia foliage with Cynodon nlemfuensis was lower than that of the grass alone (Delgado et al., 2012). The association of Tithonia diversifolia with Brachiaria brizantha at different levels had little effect on methane emissions, either at booting or pre-flowering stage (Mauricio et al., 2014).
The protein of Mexican sunflower foliage is both highly digestible and highly degradable. In vitro protein digestibility was found to be 77-79% (Verdecia et al., 2011). In vivo protein digestibility ranged from 68 to 84% (Nguyen Van Sao et al., 2010; Nguyen Thi Thu Hong et al., 2013; Pathoummalangsy et al., 2008). In sacco protein degradability of Mexican sunflower foliage was high (more than 80%, Mahecha et al., 2005; Naranjo et al., 2011). As a consequence, N excretion was higher and N retention was lower in growing goats fed withTithonia fed alone compared to Stylosanthes or jackfruit foliage fed alone (Nguyen Van Sao et al., 2010), or with Tithonia supplemented with cassava roots and/or mulberry foliage (Pathoummalangsy et al., 2008).
Mexican sunflower could be a potentially valuable forage for dairy cows though only one trial had been reported at the time of writing (December 2014). In Colombia, Tithonia diversifolia foliage replaced up to 35% (5.6 kg/d/head of fresh foliage) of the concentrate supplementation for grazing dairy cattle with no effect on milk production and quality (Mahecha et al., 2007).
In Sri Lanka, in growing sheep fed rice straw supplemented with sun-dried Leucaena, Gliricidia or Tithonia diversifolia foliage (13 g DM/kg W0.75), Tithonia gave the best DM intake and OM diet digestibility but the lowest daily weight gain, though the gain was higher than that obtained with cassava foliage (Premaratne et al., 1997; Premaratne et al., 1998). In growing sheep fed a basal diet of rice straw and cassava, the inclusion of 30% Tithonia diversifolia increased DM intake, digestibilities of DM and OM, microbial protein efficiency and daily weight gain (Premaratne et al., 1998; Premaratne et al., 1997). In Nigeria, in pre-weaned lambs fed a basal diet of Guinea grass (Megathyrsus maximus), Tithonia diversifolia foliage was included at 30% of the concentrate diet, partially replacing wheat bran (Ekeocha, 2012b).
In Nigeria, Tithonia diversifolia foliage was included at 30% of the diet to replace part of the wheat bran for pregnant ewes (Ekeocha et al., 2012b; Ekeocha et al., 2013), and lactating ewes (Ekeocha, 2012f; Ekeocha et al., 2012c) fed a basal diet of Guinea grass. In Cameroon, Mexican sunflower leaves replaced part or all of wheat bran in multinutrient blocks used to supplement Brachiaria ruziziensis straw. There was no effect of diet DM digestibility but there were negative effects on palatability, N digestibility and N retention (Zogang et al., 2012; Zogang et al., 2013).
In Vietnam, several trials have assessed the potential of Tithonia diversifolia forage as a basal diet for growing goats. In one experiment, Tithonia fed alone led to a higher DM intake than when it was supplemented with Guinea grass, jackfruit foliage, banana leaves or Calliandra calothyrsus foliage, but N retention was lowest and N excretion was highest, indicating that supplementation is necessary (Nguyen Van Sao et al., 2010). In a later trial, jackfruit foliage and cassava foliage were found to give better DM intake and daily gain than Guinea grass and banana leaves when used to supplement Tithonia foliage (1% body weight, DM basis) (Ngo Hong Chin et al., 2012). Another trial found that supplementation of Tithonia with Sesbania sesban and/or Mimosa pigra increased DM intake and N retention when compared to Tithonia fed alone (Nguyen Thi Thu Hong et al., 2013). In Sri Lanka, DM intake and OM digestiblity were higher with fresh Tithonia diversifolia fed alone than with Tithonia hay. Supplementation of Tithonia hay with mulberry leaves and/or cassava chips increased N retention without affecting DM intake. Mulberry leaves were a better supplement than banana leaves, jackfruit leaves or Erythrina poeppigiana leaves (Pathoummalangsy et al., 2008).
In Kenya, two experiments assessed the potential of Tithonia diversifolia as a protein supplement for growing goats fed a basal diet of urea-treated maize stover. In the first experiment, Tithonia was found to be a good alternative to Calliandra calothyrsus and Sesbania sesban as a protein supplement, as it resulted in significantly higher daily gain than the other supplements (Wambui et al., 2006b). A second trial showed that Tithonia diversifolia could be included up to a level of 30% (DM basis) in the diet for optimal performance (Wambui et al., 2006b).
In Nigeria, Tithonia diversifolia leaf meal was included at up to 30% (fully replacing soybean meal) in the concentrate, fed to growing goats receiving a basal diet of Guinea grass, with no adverse effect on average daily gain and FCR, though protein digestibility and nitrogen retention were reduced when Tithonia leaf meal was included at more than 10% (Odedire et al., 2014).