Biofuel co-products as livestock feed - Opportunities and challenges

136Biofuel co-products as livestock feed – Opportunities and challengesin drenching studies (Goff and Horst, 2001). Treatmentswere top-dressed and hand-mixed into the upper one-thirdof the daily ration from 21 days pre-partum until 21 daysafter calving. Pre-partum DMI was greater for control cowscompared with those fed glycerol (13.3, 10.8 and 11.3 ±0.5 kg/day for 0, 0.43 and 0.86 kg of glycerol, respectively).Rumen fluid collected post-partum showed cows fed glycerolhad greater total VFA, greater molar proportions ofpropionate and a decreased ratio of acetate to propionate.Butyrate tended to be greater for cows fed glycerol postpartum.Glucose concentrations in plasma were actuallygreatest for cows fed the control diet compared with thosefed glycerol, discounting the perception of the glucogeniceffects of glycerol. DMI, body weight, body condition andliver lipid during the first 21 DIM were similar among treatments.There were no cows that exhibited signs of ketosisin any of the treatments. Yield of energy-corrected milkduring the first 70 DIM tended to be greatest for cowsfed the control diet. Cows fed glycerol had decreased milkurea nitrogen (MUN) concentrations. It was concluded thatincreased energy in glycerol supplemented diets may havebeen beneficial to the cows, but feeding glycerol did notprovide an increase in gluconeogenic precursors.In a transition cow experiment, a dry glycerol product(food grade, 65 percent glycerol) was fed from calving until21 DIM in an experiment with 39 multiparous Holsteincows (Chung et al., 2007) with 250 g of product, supplying163 g/day of glycerol. Researchers observed no differencesin feed intake or milk yield during the first 3 weeks of lactation.There was a tendency toward greater milk yield fordry glycerol-supplemented cows during week 6 of lactation(51.7 vs 45.8 kg/day) after the supplementation period hadended, suggesting a potential benefit of dry glycerin onenergy status and subsequent milk production.The effects of replacing high moisture maize withglycerol were determined in diets for transition dairy cowsfrom 28 days pre-partum to 56 days pot-partum (Carvalhoet al., 2011). Multiparous Holstein cows were fed dietscontaining either high-moisture maize or glycerol. Glycerolwas included at 11.5 and 10.8 percent of the diet DMfor pre- and post-partum diets, respectively. Feed intake,milk yield, milk composition and energy balance were notdifferent with glycerol feeding. Blood glucose contentwas decreased and BHBA concentration was increased incows fed glycerol during the pre-partum period. Cows fedglycerol had decreased acetate:propionate ratio at 56 DIM.These data indicate that glycerol is a suitable replacementfor maize grain in diets for transition dairy cows.Glycerol drenching as a treatment for ketosisGoff and Horst (2001) evaluated an oral glycerol drench asan aid in the treatment of ketosis in two experiments. Inthe first, cows were administered 1, 2 or 3 L of glycerol viaesophageal pump. Thirty minutes after dosing, concentrationsof blood glucose increased by 16, 20 and 25 percentfor cows treated with 1, 2 or 3 L, respectively. Similar toobservations by Schröder and Südekum (1999), Goff andHorst (2001) indicated that drenching with glycerol hadno effect on ruminal pH. In the second experiment, twocows diagnosed with clinical ketosis were treated with 1 Lof a glycerol drench. Both cows responded with higherconcentrations of glucose in blood, decreased urinaryketone body excretion, and an increased milk production.These data further support the potential role glycerolcould play as a glucose precursor in diets for transitiondairy cows.Researchers at Iowa State University have investigatedthe usefulness of drenching glycerol in combination withglucagon, a hormone to stimulate gluconeogenesis, inprevention of ketosis and fatty liver (Osman et al., 2008),administering 400 mL of glycerol diluted with 100 mL ofwater for 14 days post-partum to 12 cows with or withoutglucagon treatment. Glucagon plus glycerol treatmentincreased plasma glucose concentrations on days 1, 7 and13 post-partum by more than 40 mg/dL greater than thatof the control group, and maintained it at an elevated concentrationfor longer than other treatments. Glycerol aloneincreased blood glucose on days 7 and 13. Plasma NEFAconcentration was decreased by glucagon plus glyceroland glycerol treatments on all three sampling days. Glyceroltreatment alone maintained lower plasma NEFA for longerthan glucagon plus glycerol treatment on days 7 and 13post-partum. However, no significant effect was observedfor the glycerol-alone treatment in a later study using thesame doses of glycerol for 14 days after calving in 8 cowswith or without glucagon treatment (Osman et al., 2010).Glycerol alone did not significantly affect plasma insulin,glucose, NEFA or BHBA concentration at any point duringthe treatment, except for a significant decrease in plasmaBHBA concentration at day 9. However, co-administrationof glucagon and glycerol increased plasma glucose andinsulin and decreased plasma NEFA concentrations in bothtreatment weeks. Glycerol alone or in combination withglucagon did not significantly affect daily milk production,body condition score or liver composition. Researchers atIowa State University determined drenching glycerol wasan effective tool for prevention of fatty liver and ketosis,particularly when combined with hormonal therapy.To better explain discrepancies in results obtained fromfeeding and drenching studies, Linke et al. (2004) at SouthDakota State University used four high-producing Holsteindairy cows in a Latin square design with 1-week periods toevaluate the effect of methods of oral delivery versus feedingof glycerol on ruminal VFA and plasma concentrationsof glucose, BHBA, NEFA and insulin. Cows were 132 DIMand producing an average of 59.9 kg of milk per day. To