Abstract
The objective of this study was to evaluate the nutritional and productive characteristics of primiparous lactating cows grazing on tropical pasture, using different levels of crude glycerin in the supplement. The experiment was conducted at Rancho Santana farm, located in Jequié city, Bahia, Brazil, in the period from December 21, 2010 to March 16, 2011. Ten ¾ Holstein × ¼ Dairy Gyr lactating primiparous cows, with 109±24 days of lactation and a mean age of 30±6 months and mean body weight of 426.2±68.29 kg were distributed into five treatments, using two simultaneous 5 × 5 latin squares. Treatments consisted of inclusion levels (0, 94, 191, 289, 389 g/kg dry matter basis) of crude glycerin in the supplement. Intake, digestibility, milk production and composition were measured. Results were statistically analyzed by analysis of variance and regression at 0.05 probability. For all consumption variables no significant differences were found between the levels of crude glycerin. Except for the digestibility of ether extract, all digestibility values were similar between treatments. The fat content and yield showed quadratic effect between treatments. No significant differences were observed for protein, lactose, total solids, nonfat dry extract, fat:protein ratio, milk urea nitrogen and somatic cell count between treatments. For primiparous lactating cows grazing on tropical pasture, up to 389 g of crude glycerin/kg of dietary supplement can be included without nutritional and productive interference.
Highlights
Brazil is the sixth largest milk producer worldwide and has great potential to meet the growing domestic consumption and increase participation as an exporter of dairy products
The objective of this study was to evaluate the nutritional and productive characteristics of primiparous lactating cows grazing on tropical pastures with different levels of crude glycerin in the supplement
The lack of effects of adding glycerol to the total dry matter intake (TDMI) is consistent with other findings of research conducted in feedlot (DeFrain et al, 2004; Chung et al, 2007; Donkin et al, 2007; Donkin et al, 2009; Wang et al, 2009)
Summary
Brazil is the sixth largest milk producer worldwide and has great potential to meet the growing domestic consumption and increase participation as an exporter of dairy products. With the introduction of vegetable oil in the biofuel production chain in Brazil, the supply of glycerol in the market is expected to increase, the demand is not proportional to the supply, causing an environmental barrier. The inclusion of glycerol in feed to replace corn is a possible alternative for formulating diets for lactating cows, in addition to the results of decreased production costs, considering the market prices. Additional information on the economic evaluation of its inclusion in diets is needed to determine the effects of glycerol on relevant characteristics such as consumption, milk production and digestibility, especially in diets where intake and digestibility of fiber may limit the performance (Donkin et al, 2009)
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