Condensed molasses solubles (CMS) is the syrupy residue left after fermentation of molasses for ethanol production. Although it visually looks similar to molasses, it differs in nutrient composition. Condensed molasses solubles has less energy, a higher ash content especially in sulphur (S) and potassium, has a higher protein and lower dry matter content than molasses. When CMS was used as a replacement for molasses at an inclusion rate of above 5%-10% to ruminant diets, voluntary feed intake and weight gain decreased while feed conversion ratios increased. It was suggested that a possible reason for the poor performance of animals on CMS containing diets is the high level of S in CMS that could reduce (Se) and copper (Cu) absorption, or could lead to the excess production of H2S in the rumen. Another possibility was the lower energy value of CMS leading to inaccurate feed formulations. The goal of this paper was to investigate possible reasons why ruminants consuming diets containing CMS, perform poorly in comparison with ruminants on diets containing molasses. Two trials were conducted to identify reason for lower performance of CMS diets. Criteria associated with production performance of CMS diets were measured on an in vitro and in vivo basis while diets were balanced in protein, energy and moisture.
An in vitro trial was conducted to determine the fermentability of diets and gas composition of typical feedlot diets containing different levels of CMS. Four dietary treatments containing 0%, 5%, 10% or 15% CMS were formulated to be iso-nitrogenous and iso-energetic as well as to have similar dry matter values. Diets with different CMS inclusions were used to measure total gas production, using an automatic gas production meter that regulates gas pressure, temperature and simulates rumen motility. Gas production was measured automatically every five minutes over 42 hours. During this period gas production did not differ (P> 0.05) at any point of fermentation, and total gas production ranged from 138 mL to 155 mL. The composition of the gas produced supported an effective degradation and indicated no significant difference between treatments. Results indicated that there was no significant difference in hydrogen sulphide gas (H2S), methane or carbon dioxide concentrations in the gas. The similar H2S gas production between treatments indicates that, although S was higher in CMS containing diets, H2S production by sulphur-reducing bacteria was low when pH was regulated above a pH level of 6. Analysis of the four treatment diets indicated that the TMR s contain the same ash content, especially that of S, as in the feed formulation. The variation in composition highlighted the need to establish consistent nutrient parameters for CMS composition in order to formulate diets accurately. From the in vitro trial it was concluded that there was no difference in gas production, and therefore fermentability, between diets containing CMS or molasses.
An in vivo trial was conducted to determine the effect of CMS inclusion at 0%, 5%, 10% or 15% in feedlot diets of newly weaned bull calves from a mixture of beef breeds. The diets were formulated to be iso-energetic, iso-nitrogenous with a constant dry matter content. One hundred weaners were allocated to the four treatments, and each treatment consisted of five replicates with five bulls per replicate. The weaners were fed for a period of 112 days during which feed intake was measured every week and body weight every second week. Biweekly body weight and feed intake were measured to calculate feed conversion ratio (FCR).
There were no significant differences in the body weight, feed intake or FCR of the treatments at any point during the feeding period. The results indicated a high FCR compared to standard feedlot diets, suggesting that the experimental diets contained lower energy content than standard feedlot diets. The results indicated that when diets containing CMS were corrected and balanced for energy and protein, CMS have the potential to replace molasses in feedlot total mixed rations. However, high moisture content diluted nutrients, causing a higher FCR, thus reduced the efficiency of nutrient utilization in the diet.
Liver samples of all 100 bulls were collected to determine the effect of S of diets containing CMS on the hepatic Se and Cu concentrations in the cattle. The analysis of trial diets indicated that dietary S did not increase as expected, and therefore results were expected that there was no significant difference in liver Se and Cu concentrations between the treatments, and both Se and Cu concentrations indicated adequate intake of these elements.
The in vivo and in vitro trials indicated that CMS has potential to replace molasses, but more research is necessary, especially in composition variation and to decrease FCR in more practical feedlot conditions.
Dissertation (MSc Agric)--University of Pretoria, 2016.