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effect of low level monensin supplementation on the production of dairy cows fed Alfalfa Silage

Effectiveness of low level monensin supplementation on N utilization in lactating dairy cows fed Alfalfa Silage was assessed using 48 multiparous Holsteins. Cows were fed a covariate diet [% of dry matter (DM): 56% Alfalfa Silage, 39% ground high moisture corn, 3% soybean meal, 1% ground corn, 1% vitamin-mineral supplements] for 2 wk, then grouped by days in milk into blocks of 4. Cows were randomly assigned within blocks to 1 of 4 diets that were fed for 10 wk: 1) control (covariate diet), 2) control plus 3% fish meal (replacing DM from high moisture corn), 3) monensin (10 mg/kg DM), and 4) monensin plus 3% fish meal. Diets 1 and 3 averaged 16.7% crude protein (25% from free AA in Alfalfa Silage); diets 2 and 4 averaged 18.5% crude protein. Monensin intake averaged 16 mg/d on diets 1 and 2 (due to contamination) and 248 mg/d on diets 3 and 4. There was no effect of fish meal or monensin on DM intake. However, weight gain and yield of milk, protein, and SNF increased with fish meal feeding, indicating metabolizable protein limited production. Feeding monensin increased blood glucose but reduced yield of 3.5% fat-corrected milk, milk fat content and yield, and milk protein content and yield. Apparent N efficiency was greatest on monensin (diet 3) but lowest on monensin plus fish meal (diet 4). Fish meal reduced blood glucose concentration and apparent N efficiency, and increased concentrations of milk and blood urea. Monensin increased ruminal propionate concentration and decreased concentration of acetate and butyrate and acetate:propionate in ruminally cannulated cows fed the experimental diets. However, these changes were small, suggesting that too little monensin was fed. Fish meal reduced ruminal total amino acid (AA) but monensin did not alter ruminal NH3 or total AA. Both fish meal and monensin increased NH3 formation from casein AA using ruminal inoculum from the cannulated cows. There was no evidence from this trial that feeding 250 mg of monensin per day to lactating cows improved N utilization by reducing ruminal catabolism of the large amounts of free AA in Alfalfa Silage.

Ryegrass or Alfalfa Silage as the Dietary Forage for Lactating Dairy Cows

Renewed interest exists in using grass forages to dilute the higher crude protein (CP) and lower digestible fiber present in legumes fed to lactating dairy cows. A 3 x 3 Latin square feeding study with 4-wk periods was conducted with 24 Holstein cows to compare ryegrass Silage, either untreated control or macerated (intensively conditioned) before ensiling, with Alfalfa Silage as the sole dietary forage. Ryegrass Silages averaged [dry matter (DM) basis] 18.4% CP, 50% neutral detergent fiber (NDF), and 10% indigestible acid detergent fiber (ADF) (control) and 16.6% CP, 51% NDF, and 12% indigestible ADF (macerated). Alfalfa Silage was higher in CP (21.6%) and lower in NDF (44%) but higher in indigestible ADF (26%). A lower proportion of the total N in macerated ryegrass Silage was present as nonprotein N than in control ryegrass and Alfalfa Silages. Diets were formulated to contain 41% DM from either ryegrass Silage, or 51% DM from Alfalfa Silage, plus high moisture corn, and protein concentrates. Diets averaged 17.5% CP and 28 to 29% NDF. The shortfall in CP on ryegrass was made up by feeding 7.6% more soybean meal. Intake and milk yields were similar on control and macerated ryegrass; however, DM intake was 8.3 kg/d greater on the Alfalfa diet. Moreover, feeding the Alfalfa diet increased BW gain (0.48 kg/d) and yield of milk (6.1 kg/d), FCM (6.8 kg/d), fat (0.26 kg/d), protein (0.25 kg/d), lactose (0.35 kg/d), and SNF (0.65 kg/d) versus the mean of the two ryegrass diets. Both DM efficiency (milk/DM intake) and N efficiency (milk-N/N-intake) were 27% greater, and apparent digestibility was 16% greater for DM and 53% greater for NDF and ADF, on the ryegrass diets. However, apparent digestibility of digestible ADF was greater on Alfalfa (96%) than on ryegrass (average = 91%). Also, dietary energy content (estimated as net energy of lactation required for maintenance, milk yield, and weight gain) per unit of digested DM was similar for all three diets. Results of this trial indicated that, relative to ryegrass Silage, feeding Alfalfa Silage stimulated much greater feed intake, which supported greater milk production.

Effect of replacing Alfalfa Silage with high moisture corn on nutrient utilization and milk production.

Twenty-four multiparous lactating Holstein cows were blocked by days in milk and assigned to treatment sequences in a replicated 4 × 4 Latin square with 21-d periods. The four diets, formulated from Alfalfa Silage plus a concentrate mix based on ground high moisture ear corn, contained [dry matter (DM) basis]: 1) 20% concentrate, 80% Alfalfa Silage (24% nonfiber carbohydrates; NFC), 2) 35% concentrate, 65% Alfalfa Silage (30% NFC), 3) 50% concentrate, 50% Alfalfa Silage (37% NFC), or 4) 65% concentrate, 35% Alfalfa Silage (43% NFC). Soybean meal and urea were added to make diets isonitrogenous with equal nonprotein N (43% of total N). Intake of DM and milk yield indicated that adaptation was complete within 7 d of changing the diets within the Latin square. There were linear increases in apparent digestibility of DM and organic matter, and a linear decrease in neutral detergent fiber (NDF) digestibility with increasing dietary NFC. Solutions of significant quadratic equations yielded estimated maxima for intake of DM, organic matter, digestible organic matter, and NDF at, respectively, 37, 38, 43, and 27% dietary NFC. There were linear increases in yields of milk, protein, lactose, and solids not fat with increasing dietary NFC. Feed efficiency (milk/DM intake) yielded a quadratic response with a minimum at 27% dietary NFC. Maxima for milk fat content, fat yield, and fat-corrected milk yield were estimated to occur at, respectively, 30, 34 and 38% dietary NFC. In this short-term trial, maximal DM intake and fat-corrected milk yield indicated that the optimum concentrate for cows fed high moisture ear corn plus Alfalfa Silage as the only forage was equivalent to 37 to 38% dietary NFC; however, yields of milk, protein and solids not fat were still increasing at 65% dietary concentrate (43% NFC).

Yield response of dairy cows fed different proportions of Alfalfa Silage and corn Silage

Forty-five multiparous and 29 primiparous cows were used in a complete lactation study to determine milk yield and the potential for improving N utilization by cows fed diets containing different proportions of Alfalfa and corn Silages. Cows were fed diets with a 50:50 forage to grain ratio. The forage portion of the diet was either all Alfalfa Silage, two-thirds Alfalfa Silage and one-third corn Silage, or one-third Alfalfa Silage and two-thirds corn Silage (dry matter basis). Treatment diets were fed to 6 ruminally cannulated cows to study dietary effects on ruminal fermentation. Diets were fed as a total mixed ration. Dry matter intake as a percentage of body weight was higher for cows fed the diet containing one-third corn Silage. Mean 3.5% fat-corrected milk yield from wk 1 to 36 of lactation was 31.0, 32.9, and 31.8 kg/d for cows fed the Alfalfa, one-third corn Silage, and two-thirds corn Silage treatment diets, respectively. For 305 d of lactation, milk yield for multiparous cows was 9593, 10,170, and 10,024 kg and for primiparous cows was 8124, 8412, and 8168 kg for cows consuming the Alfalfa, one-third corn Silage, and two-thirds corn Silage treatment diets, respectively. Diets containing two-thirds corn Silage decreased milk fat content of multiparous cows during early lactation. Ruminal NH3 concentration was lower and N excretion in the environment was reduced by 6 to 15% with the diets containing corn Silage. Results suggested that corn Silage should constitute one-third to two-thirds of dietary forage dry matter when fed with Alfalfa Silage to derive maximal benefit.

Digestion and energy balance in lactating dairy cows fed varying ratios of Alfalfa Silage and grain.

Forty-four multiparous and 43 primiparous Holstein cows were used to study the effect of dietary Alfalfa Silage: grain ratio on digestion, passage of digesta, and energy balance in a complete lactation experiment. Cows were placed on one of five treatments with forage contents from 38.2 to 98.2% (DM basis) during the first 12 wk of lactation. Forage content was increased during wk 13 to 26 of lactation to give diets containing 48.2 to 98.2% forage and again during wk 27 to 44 to give diets containing 68.2 to 98.2% forage. Both DMI and DM digestibilities decreased as proportion of dietary forage increased. The DM digestibilities for multiparous and primiparous cows ranged between 69.3 and 57.3% during early lactation and 64.9 and 55.5% during late lactation. Increased percentage of forage in the diet decreased and then increased (quadratic relationship) the ruminal retention time of La, a marker applied to the Alfalfa Silage in early and late lactation. Time cows spent eating and ruminating per kilogram of DMI increased as proportion of forage in the diet increased. Cows fed diets with a high proportion of Alfalfa Silage remained in negative energy balance longer than cows fed high grain diets. Intake of NEL (calculated by either of two methods) minus NEL output (milk, maintenance, and BW change) resulted in net balances of NEL after 36 wk of lactation within 5% of NEL intake and indicated that estimates of the NEL value of feedstuffs used in this experiment were reasonably accurate.

Protein and Energy Supplementation of High Alfalfa Silage Diets During Early Lactation

Abstract Protein versus energy as a first-limiting nutrient for milk yield and milk protein content was studied in cows fed high Alfalfa Silage diets. In Experiment 1, 12 cows during wk 3 to 12 of lactation were fed diets containing 48.2% Alfalfa Silage or 98.2% Silage with or without infusion of 1 kg/d of casein into the abomasum. Infusion of casein resulted in a 22% increase in milk yield, 180-g/d increase in milk protein yield, and no change in DMI. In Experiment 2, 20 cows during wk 3 to 6 of lactation were fed 98.2% Alfalfa Silage diets and received no infusion, 1 kg/d of glucose infused into the abomasum, 1.2 kg/d of soy protein into the abomasum, or a mixture of the glucose and protein infusion into the abomasum. Infusion of glucose had no effect on milk yield but decreased DMI, milk fat, and milk protein. Infusion of protein increased daily milk yield by 17% and protein yield by 144 g/d. In Experiment 3, 20 cows during wk 9 to 12 of lactation were fed 98.2% Alfalfa Silage and received no infusion, .75 kg/d of propionate infused into the rumen, 1.2 kg/d of soy protein infused into the abomasum, and the propionate and soy protein infusions combined. In Experiment 4, 20 cows were fed 78.2% Alfalfa Silage diets with or without 5% propylene glycol. Infusion of propionate or supplementation of propylene glycol in Experiments 3 and 4 reduced DMI and milk yield. Milk yield response to protein infused into the abomasum and lack of response to energy infused into the abomasum or included in the diet in a nonfermentable form suggest that protein, not energy, is the first-limiting nutrient for milk yield in cows fed high Alfalfa Silage diets.

in vitro ruminal fermentation of treated Alfalfa Silage using ruminal inocula from high and low feed efficient lactating cows

Aims
To assess the effect of two additives on Alfalfa Silage and on in vitro ruminal fermentation when using ruminal inocula from high feed-efficient (HE) and low feed-efficient (LE) lactating cows.

Methods and Results
First and second cut Alfalfa was harvested at 40% bloom stage, treated with control (no additive), Lactobacillus plantarum (LP), or formic acid (Formic), ensiled in 1.0 L minisilos, and fermented for 60 d. Fermented Alfalfa was incubated in vitro for 24 h using ruminal inoculum from HE and LE lactating cows. The pH was lower in Alfalfa Silage treated with LP and Formic and produced lower ammonia-N than did the control. In vitro true dry matter digestibility (IVTDMD) was higher with ruminal inoculum from HE than LE cows, but there was no consistent effect of treated Alfalfa on microbial biomass yield and in vitro volatile fatty acids.

Conclusions
The IVTDMD was numerically greater with ruminal inoculum from higher feed-efficient cows although statistical significance was only demonstrated with the first-cut Alfalfa. However, treated Alfalfa Silage did not show the effect expected on in vitro microbial biomass yield.

Significance and Impact of the Study
The feed efficiency of cows used as a source of ruminal inocula may affect IVTDMD and be a source of variation across in vitro runs. Differences in ruminal fermentation between cows of different feed efficiency could help to explain differences in milk yield and other parameters of dairy cattle performance.

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Use of real time PCR to determine population profiles of individual species of lactic acid bacteria in Alfalfa Silage and stored corn stover

Real-time polymerase chain reaction (RT-PCR) was used to quantify seven species of lactic acid bacteria (LAB) in Alfalfa Silage prepared in the presence or absence of four commercial inoculants and in uninoculated corn stover harvested and stored under a variety of field conditions. Species-specific PCR primers were designed based on recA gene sequences. Commercial inoculants improved the quality of Alfalfa Silage, but species corresponding to those in the inoculants displayed variations in persistence over the next 96 h. Lactobacillus brevis was the most abundant LAB (12 to 32% of total sample DNA) in all of the Alfalfa Silages by 96 h. Modest populations (up to 10%) of Lactobacillus plantarum were also observed in inoculated Silages. Pediococcus pentosaceus populations increased over time but did not exceed 2% of the total. Small populations (0.1 to 1%) of Lactobacillus buchneri and Lactococcus lactis were observed in all Silages, while Lactobacillus pentosus and Enterococcus faecium were near or below detection limits. Corn stover generally displayed higher populations of L. plantarum and L. brevis and lower populations of other LAB species. The data illustrate the utility of RT-PCR for quantifying individual species of LAB in conserved forages prepared under a wide variety of conditions.