Bakery waste can be used to feed ruminants. It has been included at up to 30% in cattle rations without affecting palatability. Due to its high concentration of non-fibrous carbohydrates and its relatively low crude protein content, it can be used as an energy concentrate that has to be supplemented with a source of protein (Waldroup et al., 1982; Arosemena et al., 1995; DePeters et al., 1997). Bakery waste is also characterized by a high OM digestibility (96% in sheep) and a high ruminal degradability, with a measured rate of rumen degradability twice as high as that of barley (Afzalzadeh et al., 2007; Champe et al., 1980; DePeters et al., 1997).
Although dried bakery waste are reported to be included in feeds intended for dairy cows, feeding value of bakery waste has been mainly evaluated in growing lambs and steers (Arosemena et al., 1995; Champe et al., 1980). Inclusion of this by-product in the diet of these animals could be an interesting way to reduce feed costs (Hindiyeh et al., 2011; Obeidat et al., 2012). In most cases, bakery waste could be included at up to 30% in ruminant diets without affecting performance but this level depended on the amount of fibre included in the basal diet and on the specific composition of the source of bakery waste.
Lambs
In fattening lambs, bakery wastes have been used in substitution of maize (Oliveira et al., 2011; França et al., 2012; Santos et al., 2014; Mahmoud, 2017) or barley (Champe et al., 1980; Afzalzadeh et al., 2007; Hindiyeh et al., 2011).
In the experiments where bakery wastes were used to replace maize, the maximal proportion of bakery waste in the diet was 35% DM and the proportion of hay in the diet was generally high, between 40 and 60% DM. In those conditions, inclusion of bakery wastes in substitution of maize grain had no effects on nutrients intake, digestibility, and body weight or meat composition of fattening lambs (Mahmoud, 2017; Santos et al., 2014; Oliveira et al., 2011).
When bakery wastes were used to replace barley, results were more contrasted, most probably due to the variability of bakery waste and experimental conditions (Hindiyeh et al., 2011; Afzalzadeh et al., 2007; Champe et al., 1980). The replacement of barley by bakery waste (25% dietary DM) in a sheep diet based on 40% alfalfa had no impact on DM intake, final live weight, average daily gain and carcass weight of lambs (Afzalzadeh et al., 2007). Linolenic fatty acid content of meat was increased with increasing inclusion of bakery waste likely because of the high soluble sugar content of this feed (Afzalzadeh et al., 2007).
On the contrary, the inclusion of only 10% of bakery waste in the diet of lambs resulted in a slight decrease of intake, a much higher daily intake fluctuation and finally a slightly lower final body weight and growth rate. These results could be explained by the fact that the bakery waste used in this study was 80% highly fermentable wheat flour and that the forage included in the diet was only wheat straw, included at 20% DM, a possible cause of subacute acidosis (Hindiyeh et al., 2011).
A diet containing 40% dried bakery waste was not well accepted by sheep even in the context of a digestibility trial with limited amount of feed (Champe et al., 1980).
Suckler ewes and kids
It was reported that bakery waste could be included at up to 20% in suckler ewes diets containing 30% wheat hay, in substitution of barley, without affecting either performance of ewes (nutrient intake and digestibility, body weight changes, milk production and composition) or performance of lambs (initial and weaning body weight and average daily gain) (Obeidat et al., 2012).
In fattening kids, bakery waste could be included up to 20% to replace barley in a low forage (20% alfalfa) based diet without affecting dry matter intake. DM intake, average daily gain, final weight and total weight gain decreased when bakery waste increased to 30% DM (Haddad et al., 2004).
Steers
The inclusion of a relatively high percentage (55%) of bakery waste (DM basis) in fattening Angus crossbred steers diet containing less than 30% forage (maize silage and hay) had no effect on the average daily gain and on carcass and meat organoleptic characteristics, even though the DM intake decreased with bakery waste (Guiroy et al., 2000). In this experiment, the inclusion of bakery waste was high (more than 55% DM), with an amount of forage (maize silage and hay) below than 30% DM. Inclusion of bakery waste at up to 30% DM dietary level to replace maize and barley had a slight positive effect on weight gain of Sarabi crossbred steers (Seyedi et al., 2012). Bakery waste was also successfully used in mixture with broiler litter (36% bakery waste, 64% broiler litter), in substitution to a concentrate feed and rice straw, to feed Korean Hanwoo Steers (Kwak et al., 2003).