Effects of different amounts of crude glycerol supplementation on dry matter intake, milk yield, and milk quality of lactating dairy cows grazing on a Kikuyu grass pasture

Effect of Glycerol on Milk Yield, Its Quality and Blood Parameters of Holstein Cows

“…Moreover, the percentage of milk lactose increased (P≤0.01) in T2 and T3 cows at day 30 and 60 of the experiment compared with those of T1 cows (Table 2). The increasing in milk yield with glycerol supplementation may be attributed to the ability of ruminants, including dairy cows, to convert glycerol into glucose, whether through its direct transmission via the blood to the liver, which is used in the process of gluconeogenesis (30), or by increasing the synthesis of propionate when glycerol is digested by rumen bacteria into volatile fatty acids (37), The increase in glucose contributes to an increase in the energy needed for milk yield (16,23), and this is in line with a study conducted on Holstein cows by Valencia et al (46), whose observed an increase in the milk produced by 13.3% when 1500 g/glycerol /cow was added, the returned this increasing of milk produced of glucose-generating glycerol to increases the availability of energy for milk production. Glucose is one of the main components of milk, and more than 70% of the glucose synthesized inside the body of cows is used to produce milk (32,34,50).…”

“…This result is consistent with the study of Torres et al (45) who reported that glycerol increases blood glucose concentration by 2.5%, and also the study of Goff and Horst (21), who indicated that giving milk cows with an amount of 1, 2 or 3 liters of glycerol results in an increase in blood glucose by 16%, 20%, and 25%, respectively, as glycerol is one of the precursors that form glucose from the process of gluconeogenesis in the liver (21). In addition to other studies, which showed the positive effect of glycerol in increasing blood glucose concentration in dairy cows (11,46,47). The increase in the plasma concentration of TG of glycerol-treated cows was consistent with the increase in glucose synthesis, which enhanced the animal's energy, which positively affected the increase in liver activity in the synthesis of TG and its excretion outside the liver as VLDL (34), or it may be due to the inclusion of glycerol other reasor metabolism process that may result in TG synthesis, as glycerol is the backbone of triglycerides (4).…”

“…The increase in the percentage of milk lactose may due to the fact that glycerol increases the synthesis of glucose in the liver, which in turn increases the production of lactose in the mammary gland, as glucose in the blood is the main source for the synthesis of milk lactose (27). Also, the reason for this may be due to the increase the energy resulting from glycerol intake, and this enhances the synthesis of milk lactose consequently (46). This result is in agreement with the study of Zacaroni and Souto (50), whose reported that the glycerol supplementation in ruminants feeding enhances production on milk lactose.…”

“…Studies indicated that glycerol prevents metabolic problems in cows during the transition period (3 weeks pre-and 3 weeks post-partum) (38), as well as increases animal energy and reduces free fatty acids responsible for ketosis (25,30). Valencia et al (46) reported that adding glyce-rol to the diet of dairy cows (1500 g/day/cow), leads to an increase milk production by 14.2% and milk protein by 2.1%. Similar, Kupczynski et al (31) reported the importance of using glycerol in the diet of ruminants to reduce production costs by replacing it with feed grains or using it as a preventive agent against metabolic problems and ketosis.…”