Glycerol use in dairy diets: A systemic review

Abstract

There is an increasing interest in the production of biodiesel as bio-renewable fuel source, with numerous biofuel byproducts becoming available. The annual productions of biodiesel and crude glycerol were 34.5 and 3.8 billion liters, respectively, in 2016 and that of biodiesel is expected to reach 41 billion liters in 2019. Glycerol is a sugar alcohol without a color or odor, but with a sweet taste and high solubility index in water. Experiments support the use of glycerol at low levels ranging from 5% to 8% of the diet dry matter as a transition cow therapy. Administration of glycerol increases serum glucose and decreases ketone bodies. Glycerol is very rapidly fermented in the rumen to propionate and butyrate, at the expense of acetate, resulting in a decreased milk fat. Because glycerol is highly fermented in the rumen, it requires an adaptation period at the beginning of feeding. Administration of glycerol in the diet of lactating animals was paralleled with a decreased or an unaffected feed intake in most experiments. Improved ruminal environment to enhance nutrient digestibility was observed in many experiments; however, others observed reduced digestion of dietary fiber with feeding glycerol. Enhanced, lowered, or unaffected milk production and composition were observed with the administration of glycerol in lactating animal diets; however, in most cases, glycerol decreased milk fat content. The inconsistencies between results of experiments are due to the level and the purity of glycerol, diets, production stage of the animals, and other factors. Therefore, further research should be conducted to establish the efficacy of different levels, purity and administration periods of glycerol, and production stage of dairy animals fed glycerol-based or supplemented diets.

Chlorella vulgaris Microalgae and Copper Mixture Supplementation Enhanced the Nutrient Digestibility and Milk Attributes in Lactating Boer Goats

“…Additionally, C. vulgaris enriched with Cu in the Alg10 treatment enhanced the concentration of lactose which is not consistent with the result of ruminal propionate in the present study. Ruminal propionate can be efficiently utilised to produce milk lactose and provide goats with energy (El-Zaiat et al, 2019;Kholif, 2019). The observed increase in serum glucose with C. vulgaris and Cu (i.e., Alg10 treatment) supports this assumption/speculation (Sallam et al, 2020).…”

“…The increased propionate concentration with Alg10 treatment may be a result of NSC digestibility. Increasing concentration of propionate is considered beneficial in ruminant nutrition and dairy production because propionate provides greater energy for milk production than acetate, as propionate is the primary gluconeogenic VFA that can be used for lactose biosynthesis (Kholif, 2019). Altered ruminal individual VFA might be related to the positive effects of components in the mixture of C. vulgaris microalgae and Cu on ruminal bacteria.…”

“…The profile of fatty acid in milk is very sensitive to dietary changes or feed additives (Morsy et al, 2015(Morsy et al, , 2018Kholif et al, 2019). Treatments decreased the concentrations of the linear odd-chain fatty acids (C15:0 and C17:0) suggesting a decreased de novo synthesis from ruminal propionate in mammary gland due to C. vulgaris microalgae and Cu mixture, as rumen bacteria are the major source of odd fatty acids in ruminant milk (Vlaeminck et al, 2006).…”

Metabolic alterations in dairy cows with subclinical ketosis after treatment with carboxymethyl chitosan‐loaded, reduced glutathione nanoparticles

“…Drugs used currently to treat simple ketosis include glucose (GLu), 8 propylene glycol, 9 and glycerin. 10 These drugs have played an important role in the treatment of ketosis either because of the direct supplementation of GLu or the stimulation of gluconeogenesis. 11,12 However, it is difficult to clinically treat secondary ketosis with fatty liver or abnormal liver function in dairy cows resulting from a high amount of NEFA and lipid oxidative stress.…”

Glycerol-based formulations increases ovulation rate in sheep similarly to eCG but red blood cell indices may be affected

“…Recently, there has been an increasing global demand for biofuels, resulting in an increased demand for the feedstuffs (corn, wheat, and oilseeds) used for fuel extraction. The main by-product during the production of biodiesel is glycerol, which can be used as livestock feed ingredient or feed supplement (2). The EU legislation approved glycerol and another biodiesel co-product, namely propylene glycol, as animal feed additives with no restrictions on animal species or quantity that may be fed, while recommending from the European Food Safety Authority the collection of data on the presence of impurities and contaminants in crude glycerine from biodiesel production (3,4).…”