The effects of added glycerol or unprotected free fatty acids or a combination of the two on silage intake, milk production, rumen fermentation and diet digestibility in cows given grass silage based diets

Abstract

The addition of glycerol or free fatty acids either alone or in combination to concentrate was studied for the effects on feed intake, milk production, rumen fermentation, blood metabolites and diet digestibility in dairy cows given grass silage ad libitum. The study was conducted on 12 mid-lactating cows, four of them ruminally cannulated. Barley-based concentrate (control diet, C) was given 7 kg/d as fed. In the other three diets, 36 g/kg of barley was replaced by glycerol (G) or a mixture of free fatty acids (FA) or by a combination of the two, making a total of 72 g/kg (GFA). The experimental design consisted of balanced 4 x 4 Latin squares with a 2 x 2 factorial arrangement of diets: the effects of G, FA and G*FA interaction. The FA diets significantly decreased silage intake, increased milk yield, decreased milk protein content, increased the concentrations of C18:0, C18:1, and C20:1 and decreased those of C8-16, and C18:3 fatty acids in milk fat. The FA diets also increased the concentration of nonesterified fatty acids in plasma, and decreased the digestibility of organic matter and neutral detergent fibre but increased that of fat. Glycerol decreased the molar proportion of acetate and increased the molar proportions of propionate and butyrate in the rumen, but the addition of glycerol did not have any effect on silage intake, milk yield or milk composition. Milk yield was highest when glycerol and free fatty acids were given together, showing a positive interaction.

High- and low-purity glycerine supplementation to dairy cows in early lactation: effects on silage intake, milk production and metabolism

“…The tendency for increased ECM yield in cows fed high-purity glycerine is in line with results reported by Bodarski et al (2005), who observed increased milk yield in cows fed a diet supplemented with glycerine at a rate of 300 or 400 ml/day during 10 weeks of lactation. In contrast, a number of studies have found no effect of glycerine on milk yield (Khalili et al, 1997;Wang et al, 2009;Carvalho et al, 2010), and DeFrain et al (2004) observed a tendency for decreased milk yield. However, in all these studies, concentrate was replaced by glycerine, whereas in the present study glycerine was provided in addition to concentrate.…”

“…Not only in north-western Europe but also in other regions, the rations fed to lactating dairy cows are generally based on grass silage supplemented with concentrates (Khalili et al, 1997). Glycerine is an energy-rich by-product; the energy content has been estimated to be 16.2 MJ metabolisable energy (ME)/kg (Mach et al, 2009) with glucogenic properties, produced when biodiesel is manufactured from rapeseed oil (Thompson and He, 2006).…”

“…Glycerine is an energy-rich by-product; the energy content has been estimated to be 16.2 MJ metabolisable energy (ME)/kg (Mach et al, 2009) with glucogenic properties, produced when biodiesel is manufactured from rapeseed oil (Thompson and He, 2006). It can be used as an energy supplement to dairy cows during early lactation (DeFrain et al, 2004;Wang et al, 2009;Carvalho et al, 2010) or mid-lactation (Khalili et al, 1997;Donkin et al, 2009). In general, glycogenic substrates support the supply of glucose and enhance the metabolic status of dairy cows in early lactation, as a substrate for gluconeogenesis (Leng, 1970;Ingvartsen, 2006).…”

“…Methanol is efficiently metabolised by the rumen microorganisms, mainly to methane (Pol and Demeyer, 1988;Neumann et al, 1999). Previous studies have examined different glycerine administration strategies, for example, top-dressed or mixed into the total mixed ration (TMR; DeFrain et al, 2004;Wang et al, 2009;Carvalho et al, 2010), or within the concentrate ration (Fisher et al, 1971;Khalili et al, 1997). Furthermore, glycerine products of different qualities have been used, for example, low-purity glycerine.…”

Crude glycerin in supplement to primiparous lactating cows grazing on tropical pasture: nutritional and productive characteristics

“…This lower result found for this variable can be explained by the lower digestibility for the diet without the coproduct. Khalili et al (1997) stated that the supply of glycerol along with plants that have a high content of fatty acids (lipids) increases the digestibility of lipids, leading to the argument that the interaction of glycerol and fatty acids results in an increase in the production of MPc (Khalili et al, 1997), being a consequence of increased digestibility of lipids. Donkin et al (2009), working with glycerol levels in the diet (0, 50, 100 and 150 g/kg) of Holstein cows, found increases in the digestibility of DM (DMD), organic matter (OMD) and crude protein (CPD).…”