The evaluation of live yeast culture on the production of early lactation dairy cows
Creators: name: Woodward, Nicole
Publisher: name: University of British Columbia
Year: 2009

description: The effects of the inclusion of a live yeast culture (LYC) containing Saccharomyces cerevisiae to ruminant diets was examined in two experiments. The first experiment was an in vitro study designed to determine the optimal level of inclusion of LYC to barley grain and orchardgrass hay as assessed by production of gas from fermentation. Parameters of cummulative, potential, rate and lag of gas production were measured. Gas production was monitored by computer interfaced pressure sensors every ten minutes for an incubation period of 24 h. Levels of LYC investigated were 0.0, 0.05, 0.10, 0.15, 0.20, 0.25 and 0.30 % LYC on a dry matter (DM) basis of substrate. Rumen fluid inoculum was collected from two donor cows maintained on a 60:40 barley grain / orchardgrass hay diet. The barley grain portion of the ration was supplemented with 0.2 % LYC on a DM basis. The diet of the donor cows was then supplemented with 0.12 % LYC on a dry matter basis. Barley grain and orchardgrass hay samples were dried and ground through a 1 mm screen. Samples of either barley grain or orchardgrass hay, 150 mg, were incubated in quadruplicate, with 15 ml of rumen fluid and buffer solution in modified 50 ml Erlenmyer flasks. Gas production values were fitted to the following exponential growth model with lag (Y = b ( 1 – e-c(t-l)). Resulting gas production parameters indicated that for barley grain the 0.2 or 0.25 % LYC level would be the most suitable. These levels of LYC produced the highest potential gas production (15.80 and 16.89 ml/mg DM), the slowest rate of gas production (0.13 and 0.11 ml/h) and the shortest lag of fermentation (0.06 and 0.08 h), respectively. For barley grain the 0.10 % LYC inclusion level produced significantly (P&lt;0.05) higher (389.2 mol) total VFA production when compared to the control (264.6 mol). The acetate, propionate levels and the acetate:propionate ratio were not affected (P&gt;0.05) by the LYC inclusion. For orchardgrass hay, the 0.2 % LYC level produced a significantly (P&lt;0.05) higher level of potential gas production (16.0 ml/mg DM) and decreased lag of onset of fermentation (0.20 h). The inclusion of LYC had no affect (P&gt;0.05) on total VFA production. Supplementation of LYC decreased acetate production when compared to the control for all levels of LYC. Inclusion of LYC had no effect (P&gt;0.05) on propionate production and the acetate:propionate ratio. Based on the gas production experiment it was concluded that the 0.2 % level of LYC inclusion is optimal for a diet consisting of barley grain or orchardgrass hay. The second experiment was an in vivo lactation study designed to determine the effect of LYC supplementation on dry matter intake (DMT) and milk yield of dairy cows in early lactation. Twenty-four multiparous cows were paired, based on age, body weight, previous year's 305 d milk production and then randomly assigned to one of two treatment groups, control or a diet supplemented with LYC. Pre partum DMI was monitored for approximately 7 days prior to parturition. Lactation was divided into two distinct periods; period one and period two. Period one, 0 -14 days in milk (DIM), in which body condition score (BCS), body weight (BW), rumen pH, rumen volatile fatty acids, blood parameters, DMI, milk yield and milk composition were monitored. Period two lasted from 15-85 DIM in which milk yield and milk composition were recorded. Pre partum cows were fed a basal ration consisting of 85 % forage and 15 % concentrate on a DM basis. In addition to the basal ration all cows received 1 kg of concentrate, twice daily, fed separately from the basal ration. LYC was fed at a level of 0.2 % of the total diet on a DM basis and fed in two equal portions that were hand mixed into the separately fed concentrate. Post partum cows received the basal ration with separately fed incremental increases in concentrate of 0.5 kg/d until 14 DIM. Results indicated that LYC had no significant (P&gt;0.05) effect on pre partum or period one DMI, milk composition, ruminal pH, selected blood parameters, body weight (BW) or body condition score (BCS). During the first fourteen days of lactation there were no significant (P&lt;0.05) difference in milk yield between the control and the supplemented group except for day 14 (42.2 vs. 37.5 kg/d). Analysis of volatile fatty acids for period one indicated that the inclusion of LYC had no significant (P&gt;0.05) effect on total or individual volatile fatty acid production. During period two, in which there was no LYC supplementation cows, that previously received LYC showed a significant (P&lt;0.05) increase in milk yield and higher peak lactation when compared to the control group (44.1 vs. 40.4 kg/d). These studies demonstrate that the inclusion of LYC prior to parturition is beneficial for cows in early lactation.