Crude glycerol as glycogenic precursor in feed; effects on milk coagulation properties and metabolic profiles of dairy cows

Abstract

As grain prices rise, the search for alternative glycogenic precursors in animal feed becomes increasingly important, and this study was conducted to determine if the replacement of starch with glycerol, as an alternative glycogenic precursor, affects the milk metabolic profile and milk coagulation ability, and therefore the quality of the milk. Eight primiparous mid-lactation Holstein cows were fed during a replicated 4 × 4 Latin square trial with four different isoenergetic rations: (1) control (T0) fed a total mixed ration (TMR) with barley meal; (2) group T1, decreased barley content, replaced isoenergetically with 1 kg crude glycerol; (3) group T2, the barley meal was replaced with 2 kg of crude glycerol; and (4) group T3 the barley meal was replaced with 3 kg of crude glycerol. Rumen, blood and milk samples were collected at the end of every 21-d treatment period. Rumen samples were analysed for proportion of total volatile fatty acid (VFA), blood samples for insulin and glucose, and milk for metabolites (e.g. citric-acid cycle compounds). The change in glycogenic precursors had a positive effect on rumen VFA proportions; the proportion of propionic acid increased (P < 0.001). Milk protein (P < 0.001) and curd firmness (P < 0.001) both increased. The increase in milk protein concentration may have been due to an increase in microbial protein. Regarding the milk metabolic profiles, different signals were positively associated with coagulation ability and change in the diet. Based on this study, changing the glycogenic precursor in animal diet in this way is possible, and may have no immediate deleterious consequences on milk quality or cow health. Indeed, there is evidence for benefits from this substitution.

Effects of high concentrations of dietary crude glycerin on dairy cow productivity and milk quality

“…Authors have reported decreases in milk protein concentration with up to 3 kg/d of dietary glycerol (Harzia et al, 2013), whereas others have shown increases in milk protein (Kass et al, 2012;Wilbert et al, 2013). In the current study the milk protein concentration and the daily production of milk protein remained constant regardless of dietary treatment.…”

“…In fact, a lower concentration of dietary purified glycerin (3.1%) has been shown to increase milk yield and milk protein concentration (Bodarski et al, 2005). When crude glycerin (82.6% glycerol) was added up to 15.6% in diets for medium-yield cows, no changes were observed in milk production and quality (Harzia et al, 2013), evidencing no difference in results of studies using crude or purified glycerin, as reported by Omazic et al (2013). Altogether, these experiments indicate that purified or crude glycerin can be fed up to 15% of dietary DM to lactating cows without deleterious effects.…”

The comparison of propylene glycol and glycerol as feed additives in early lactation of high producing dairy cows

“…Various studies Farkašová et al, 2007;Wang et al, 2009a;Harzia et al, 2013) indicate that glycerol changes the concentration of individual volatile fatty acids in the rumen, increases the content of propionate and butyrate, and decreases the amount of acetate. In both experiments of our study, the propylene glycol groups showed a numerically higher concentration of acetate and lower concentration of propionate and butyrate as compared with animals that received glycerol; however the differences between groups were relatively small and insignificant.…”

Glicerina bruta como alimento energético para vacas de leite

“…The liver is responsible for converting propionate from starch fermentation in the rumen, glucogenic amino acids, and glycerol from adipose triglycerides into glucose (HIPPEN et al 2008). HARZIA et al (2013) evaluated the replacement of starch with crude glycerin. Eight primiparous mid-lactation dairy cows were used in a replicated 4 x 4 Latin Square experiment with 21-d periods, having one square of rumen cannulated cows.…”