A52-75-2007E.pdf - AgroMedia International Inc

Feeding11Milk from forage as affected by carbohydrate source anddegradability with alfalfa silage-based dietsCorresponding AuthorPellerin, D.Université LavalCollaboratorsCharbonneau, E.Université LavalChouinard, P.Y.Université LavalAllard, G.Université LavalLapierre, H.AAFC Dairy and Swine Researchand Development CentreJournal of Dairy Science (2006) Vol. 89 p. 283-293.Milk from forage (MF) is a theoretical estimate of the amount of milk producedfrom the forage portion of a complete ration. It is calculated by subtractingfrom total milk yield the production theoretically supported bythe concentrate portion of the diet, assuming that maintenance requirementsare covered by forage. Having been used in Québec for many yearsas an estimate of the efficiency of feed use, MF has been shown to haveeconomic value, since forages are generally the least costly part of the diet.However, the specific combination of forage and concentrates in the dietcan influence MF—when the nutrients provided by concentrates are morecomplementary to those in the forage, MF is likely to be higher. In thisstudy, 4 mixed concentrates containing non-fibre carbohydrate (NFC) withvarying rumen degradability were fed in alfalfa silage-based diets to evaluateeffects on MF. NFC sources in the 4 concentrates were cracked corn(control), ground corn (GC), GC plus wheat starch (GC+S) and GC plus driedwhey permeate (GC+W). Diets containing GC or GC+S increased both MFand dry matter intake when compared with the control. This was likely dueto the higher degradability of those NFC sources which complementedthe highly degradable protein in the alfalfa silage.12Impact of lowering dietary cation-anion difference in non-lactatingcows: A meta-analysisCorresponding AuthorOetzel, G.R.University of WisconsinCollaboratorsCharbonneau, E.Université LavalPellerin, D.Université LavalJournal of Dairy Science (2006) Vol. 89 p. 537-548.Reduction of dietary cation-anion difference (DCAD) in the late dry period isrecommended as a strategy to reduce the incidence of milk fever. Over thepast 30 years, a large number of studies have evaluated the efficacy of thisstrategy; several have suggested modifications to its application or to themethod of calculating DCAD. This article presents a review of 22 of thoseprevious studies. Trial data was combined and subjected to re-analysis tobuild a statistical model relating DCAD to indicators of metabolic status.Lower DCAD levels were associated with reductions in clinical milk fever,dry matter (DM) intake, urinary pH, blood bicarbonate, and blood carbondioxide concentrations; blood pH was also slightly reduced. Blood ionizedcalcium was increased before and at calving. Five different equations usedto calculate DCAD were compared for their ability to account for milk feverincidence and urinary pH reduction in trial groups. The equation (Na + K)– (Cl + 0.6 x S) was the most highly associated with both clinical milk feverand urinary pH. The model developed from this analysis predicted that areduction in DCAD from +300 to 0 ionic milliequivalents per kg of dietaryDM would reduce the risk for clinical milk fever from 16.4 to 3.2%, decreaseurinary pH from 8.1 to 7.0 and reduce DM intake by 11.3%.40 Highlights in Canadian Dairy Cattle Research - 2007