Effect of crude glycerin on dry matter and nutrient digestibility of feed ingredients in dairy cows

Tuesday, July 22, 2014
Exhibit Hall AB (Kansas City Convention Center)
Flavia de Oliveira Scarpino van Cleef , CNPq, Brasilia, Brazil
Jane Maria Bertocco Ezequiel , UNESP, Jaboticabal, Brazil
Juliana Borsari Dourado Sancanari , UCB, Jaboticabal, Brazil
Eric H C B Van Cleef , UNESP, Jaboticabal, Brazil
Abstract Text: Rumen-cannulated Holstein cows (n = 6; 587 ± 39 kg BW; 114 ± 29 DIM; 20 ± 1.5 kg milk/d), were used to evaluate the effects of crude glycerin on in vitro digestibility of dry matter, and nutrients (CP and NDF) of feed ingredients. Cows were assigned to a replicated 3 × 3 Latin square. The three isoenergetic and isonitrogenous diets composed of corn silage, cracked corn grain, sunflower meal, corn gluten, urea, mineral premix, and 0 (G0), 15 (G15), or 30% (G30) crude glycerin. The experiment lasted 69 d, with three periods of 23 d each. For in vitro determinations, the Daisy II fermenter was used. The ingredients were ground (1 mm), and placed in F57 bags (0.5 g/bag; 25 bags/treatment). At d 20 of each experimental period, rumen content was manually collected and strained with cheesecloth. Then, 400 ml of strained rumen content were placed in each fermentation jar, with 1330 ml buffer A and 266 ml buffer B. The jars were purged with CO2, and incubated at 39oC for 72 h. When the incubation was completed 48 h, 8 g pepsin and 40 ml HCl 6N were added to each jar. The pH and ammonia-N (NH3-N) were determined at 0, 48, and 72 h of incubation. Data were analyzed as mixed model with fixed effects of diet and period, and random effects of cow (diet) and residuals. Crude glycerin inclusion did not affect pH and NH3-N concentration (pH = 6.5, 6.4, 3.4; NH3-N = 20.5, 8.3, and 8.5 mg/dl, respectively for 0, 48, and 72 h incubation). The addition of 15% crude glycerin decreased (P<0.05) IVDMD and IVCPD of sunflower meal, and corn grain. When 30% crude glycerin were added, a decrease in IVDMD was observed for corn gluten (P<0.05), and in vitro NDF digestibility for corn silage (P<0.01). No differences were observed on IVDMD and IVCPD of corn silage. The addition of up to 30% crude glycerin in lactating cows diets affected digestibility of feed ingredients. Caution should be taken when combining glycerin with roughages, due to the negative effect on NDF digestibility.

Keywords: dairy cow, digestion, glycerol.