Selenium supplementation of lactating dairy cows: effect on selenium concentration in blood, milk, urine, and feces

The objectives were to determine effects of graded levels of selenized yeast derived from a specific strain of Saccharomyces cerevisiae (CNCM I-3060) on animal performance and in selenium concentrations in the blood, milk, feces, and urine of dairy cows compared with sodium selenite; and to provide preliminary data on the proportion of selenium as selenomethionine in the milk and blood. Twenty Holstein cows were used in a 5 × 5 Latin square design study in which all cows received the same total mixed rations, which varied only in source or concentration of dietary selenium. There were 5 experimental treatments. Total dietary selenium of treatment 1, which received no added selenium, was 0.15 mg/kg of dry matter, whereas values for treatments 2, 3, and 4, derived from selenized yeast, were 0.27, 0.33, and 0.40 mg/kg of dry matter, respectively. Treatment 5 contained 0.25 mg of selenium obtained from sodium selenite/kg of dry matter. There were no significant treatment effects on animal performance, and blood chemistry and hematology showed few treatment effects. Regression analysis noted significant positive linear effects of increasing dietary selenium derived from selenized yeast on selenium concentrations in the milk, blood, urine, and feces. In addition, milk selenium results indicated improved bioavailability of selenium from selenized yeast, compared with sodium selenite. Preliminary analyses showed that compared with sodium selenite, the use of selenized yeast increased the concentration of selenomethionine in the milk and blood. There was no indication of adverse effects on cow health associated with the use of selenized yeast.     

Dietary energy regulation during gestation on subsequent lactational response to soybean meal or dried brewers grains

Forty-two Holstein cows were paired by body condition and mature equivalent milk production and fed either a high or low energy diet for the last 16 to 18 wk of lactation. Cows fed the high energy diet produced more milk (21.6 versus 17.6 kg/d), gained more body condition, and were heavier after calving (641 versus 591 kg) than cows fed the low energy diet. Beginning wk 3 postpartum, half the cows in each prepartum energy group were fed supplemental dried brewers grains or soybean meal. During wk 1 to 15 of lactation, cows from the high energy group produced more 3.5% fat-corrected milk (33.8 versus 31.3 kg/d), consumed less dry matter (23.2 versus 24.4 kg/d), and lost more body weight (-2.7 versus .9 kg/wk) compared with cows from the low energy group. Milk production, feed intake, and body weight change were not affected by protein source. The high amount of bound nitrogen in dried brewers grains resulting in decreased intestinal digestibility of escape protein may have been responsible for the lack of production response to this protein source.     

BREWERS GRAINS AS A SOURCE OF SELENIUM IN BEEF CATTLE RATIONS

Soils, and therefore crops, deficient in selenium in the Northeastern United States are well-known. Brewers grains containing barley grown on high-selenium western soils should serve as an efficient supplementary source of the element in cattle rations. In this study, beef cattle were fed a diet containing brewers grains for six months and their concentration of selenium in blood was compared to a control group of cattle fed a comparable diet but without brewers grains. The concentration of selenium in the blood of the cattle receiving brewers grains increased significantly (p < 0.01) from an initial level of 12.15 ± 2.74 (average ± standard deviation) micrograms/100 mL to 22.88 ± 3.54 at the end of the feeding period. The control group showed a nonsignificant increase from 15.35 ± 2.29 to 16.19 ± 2.08. There was no significant (p > 0.05) increase in average rate of weight gain between the two treatment groups.     

Milk production response to diets supplemented with dried brewers grains, wet brewers grains, or soybean meal

Forty four multiparous Holsteins, 114 +/- 28 days in milk (32 kg/day, 3.4% fat), were fed a basal diet of 12% crude protein and 20% acid detergent fiber for 10 days, then stratified by milk production into four groups. Cows were randomized to one of nine diets in a 3 X 3 factorial in which basal was supplemented with dried brewers grains, wet brewers grains, or soybean meal to supply in the diet 14.5, 16.0, and 17.5% crude protein. Eight cows remained on basal during the 50-day trial. Basal contained: 14% alfalfa silage, 27% ensiled ground-corn, 53% corn silage, and 6% vitamin-mineral mix. Milk production (kg/day) for cows fed dried brewers grains (29.4) and wet brewers grains (28.9) was higher than soybean meal (26.2) and basal (23.1). Milk production was different for diets with high (29.6) vs. low (27.8) and medium (27.2) protein. Dry matter intake (as percent of body weight) was 3.7, 3.5, 3.3, and 2.9 for dried brewers, wet brewers, soybean meal, and basal, respectively. Milk protein percent and milk fat percent differed for protein source. Rumen fluid ammonia nitrogen for combined 2, 4, and 6 h post-feeding, was (mg/100 ml) 10.4 for dried brewers, 14.9 for wet brewers, and 18.0 for soybean meal and increased from 13.2 to 15.4 with increased protein. Plasma urea tended to follow patterns of rumen ammonia. Dried brewers grains had lower apparent nitrogen digestibility but equal nitrogen balance, indicating more efficient metabolic use than soybean meal.     

Evaluation of the physical structure of fodder beets, potatoes, pressed beet pulp, brewers grains, and corn cob silage

The physical structure of fodder beets, raw potatoes, ensiled pressed sugar beet pulp, ensiled brewers grains, and corn cob silage was evaluated in diets containing concentrates and either corn silage or grass silage as the roughage source. In one series of experiments, the chewing activity of eight cows was measured over 4 d. The beet pulp and fodder beets were added to the two roughage sources at two ratios [20:80 and 35:65, dry matter (DM) basis]. Potatoes, brewers grains, and corn cob silage were fed in a fixed amount (5 to 6 kg of DM) with corn silage. The chewing indexes (eating and ruminating time per kilogram of DM ingested) for fodder beets and beet pulp averaged 34.3 and 32.3 min/kg of DM, respectively, and were hardly affected by the nature of the roughage or by the inclusion ratio. The chewing indexes for potatoes, brewers grains, and corn cob silage were 23.7, 56.6, and 41.6 min/kg of DM, respectively. In another series of experiments using 8 to 11 cows, the ratio of roughage to concentrates was lowered weekly by 5 percentage units, and the critical rough-age portion of the diet was determined (i.e., the amount just before a lack of physical structure was observed). The roughage source was either fed alone or supplemented with about 4 kg of DM of the experimental feed. The critical roughage portion of the diet decreased when the experimental feeds were added; the decrease was greatest with ensiled pressed beet pulp and was lowest with corn cob silage.     

Managing diet quality for cheddar cheese manufacturing milk. 2. Pasture v. grain supplements.

The effects of supplementing a basal diet of silage and hay with increasing amounts of harvested spring pasture, or with lupin and wheat, on the composition of milk and the consequent effects on cheese composition and yield were investigated in an indoor feeding study. Milk was collected from five groups of eight cows in mid lactation offered different diets and manufactured into Cheddar cheese on a pilot scale. Milk from cows given the lupin-wheat (LW) and the high pasture level (HP) diets produced low moisture cheese. Cheese produced with milk from cows given the control diet was high in moisture content compared with that made with milk from cows offered the LW diet. Cheese yields from the milk of cows offered the HP and LW diets were greater than from the milk of cows on the control diet, and were associated with the higher casein concentrations of these milks. Casein number was higher in milk from diets supplemented with pasture but was not an indicator of the functional properties of milk that affected cheese moisture. The proportion of beta-casein in milk from cows offered the HP diet was higher and that of gamma-casein lower than in milk from cows given the LW supplement, although cheese moisture content was similar with both diets. Milk from cows offered the HP diet had a greater inorganic P concentration than that from cows given the LW diet, although the dietary intake of P was higher for the LW diet. The significance of the effect of dietary P intake on the concentration of inorganic P in milk and hence its suitability for cheesemaking was apparent when dietary P intake was low, as shown in milk produced by cows offered the control diet.     

Vitamin E supplementation of high fat diets for dairy cows

High fat diets +/- 1 g alpha-tocopheryl acetate per head per day were fed to 28 cows for 4 mo to determine whether dietary fat increases dietary requirement for vitamin E. Tocopherol supplementation did not affect milk production or composition. After 4 mo there was no difference between treatment groups for oxidative stability (thiobarbituric acid test) of milk stored for 5 days with .1 ppm added copper, but milk of supplemented cows was more stable when 1 ppm copper was added. Oxidative stability was normal in the unsupplemented group. Tocopherol concentration of blood plasma increased and selenium concentration decreased with tocopherol supplementation; activity of glutathione peroxidase was lower in plasma, whole blood, and erythrocytes of the supplemented group. Tissue integrity was unchanged by tocopherol supplementation, as estimated by erythrocyte hemolytic resistance and activities of lactic dehydrogenase and glutamic oxalacetic transaminase in blood serum. Clearance of bromosulphthalein from blood plasma was less for cows fed fat and supplemented with tocopherol than for control cows fed neither fat nor vitamin E. No indication of impaired vitamin E status was observed when 4% stabilized fat was added to the diet.     

Effect of dietary sulfur and selenium concentrations on selenium balance of lactating Holstein cows

The effects of dietary sulfate and selenium concentrations on selenium balance in dairy cows were investigated. Midlactation Holstein cows (n = 30) were fed diets containing either 0.1 or 0.3 mg of supplemental Se (from sodium selenate)/kg of dry matter and 0, 0.2, or 0.4% added S from a mix of calcium and magnesium sulfate in a factorial arrangement. The experiment lasted 112 d. Dry matter intake was linearly reduced with increasing S, but the effect was greater when 0.3 mg/kg of Se was fed (significant interaction). Treatment effects for yields of milk, milk fat, and milk protein were similar to those for dry matter intake. Increased dietary S linearly reduced plasma Se concentrations. Increasing dietary S linearly reduced apparent (42.7, 33.1, and 30.1%) and estimated true (50.5, 46.0, and 42.3%) Se digestibility. Excretion of Se via feces (1.6 vs. 2.8 mg/d) and urine (0.5 vs. 1.3 mg/d) was higher and output in milk (0.4 vs. 0.3 mg/d) was lower for cows fed 0.3 mg/kg of Se compared with 0.1 mg/kg, but no Se effect was found for estimated true Se digestibility. Dietary S from sulfate reduced Se balance especially when cows were fed diets with less than 0.3 mg of Se/kg of diet dry matter.     

Dietary protein quality and quantity affect lactational responses to corn distillers grains: a meta-analysis

Diet fermentability influences lactational responses to feeding corn distillers grains (CDG) to dairy cows. However, some measures of diet fermentability are inherently related to the concentration and characteristics of corn-based ingredients in the ration. Corn-based feeds have poor protein quality, unable to meet the essential AA requirements of lactating cows. We conducted a meta-analysis of treatment means (n = 44) from the scientific literature to evaluate responses in milk yield (MY) and milk true protein concentration and yield to dietary CDG. The test variable was the difference in response between the CDG diet mean and the control diet mean (0% CDG) within experiment. Fixed variables were CDG concentration of the diet [% of dietary dry matter (DM)] and crude protein (CP) concentration and fractions of CP based on origin (corn-based versus non-corn-based feeds) of control and CDG diets. Diets with CDG ranged from 4 to 42% CDG, DM basis. Non-corn-based dietary CP averaged 6.3 ± 3.32% of total DM. Milk yield and milk true protein yield responses to added CDG were maximized when approximately 8.5% of the total dietary DM was non-corn-based CP. Milk yield response peaked for higher-producing cows (>30.0 kg MY/cow per day) at 4.3% dietary corn-based CP, but decreased linearly for lower-producing cows (<30.0 kg MY/cow per day) as corn-based dietary CP increased. Milk true protein yield response decreased as corn-based dietary CP concentration increased but milk true protein concentration response was not decreased when CDG diets had more than 6.5% dietary non-corn-based CP. Overall, 8.5% dietary non-corn-based CP was necessary in lactation diets to maximize lactational responses to dietary CDG. The necessity of dietary non-corn-based CP to maximize milk and milk protein yields limits the amount of dietary corn-based CP, including that from CDG, which can be included in rations without overfeeding N.     

Effects of sodium carbonate on milk yield, milk composition, and blood components of dairy cows in early lactation

Eighteen multiparous Friesian cows were paired according to lactation number and expected calving date and assigned randomly to one of two diets in a crossover design experiment to study effects of sodium carbonate on milk yield, milk composition, blood metabolites plus Na, and K in early lactation. Diets were concentrate containing either 0 or 1.2% sodium carbonate (as fed) for ad libitum intake plus 7.0 kg of wet brewers grains and 5.5 kg of long-stemmed alfalfa hay per cow daily. Dry matter intake, milk yield, milk protein percentage and yield, and percentages of milk lactose and milk SNF were not significantly affected. Compared with the control diet, the sodium carbonate treatment increased milk fat percentage (3.98 vs. 3.53%) and yield (1.23 vs. 1.07 kg/d), 4% FCM yield (30.9 vs. 28.2 kg/d) and milk total solids (12.47 vs. 12.04%). No significant differences were observed in blood plasma concentrations of glucose, CP, urea, acetate, beta-hydroxybutyrate, triglycerides, FFA, Na, or K when sodium carbonate was added to diets for early lactation cows.     

Influence of varying protein and starch degradabilities on performance of lactating cows

A milk production and digestibility trial with 32 cows (2 X 2 factorial with 8 cows per treatment) was conducted to test animal response to varying rumen degradation of dietary starch and protein. Four rations (barley-cottonseed, barley-brewers dried grains, milo-cottonseed, and milobrewers dried grains) were compared in early lactation cows fed 65% concentrate and 35% forage for 60 d. Digestibilities of starch were higher for barley than milo diets; whereas, those for organic matter were higher for cottonseed meal than brewers dried grains. Milk production was highest on barley-cottonseed with mean adjusted values of (kg/d): 37.4, 34.9, 34.2, and 34.6 for respective treatments. Dry matter intakes were not different among rations. Milk fat was higher on milo than barley with respective diets averaging (%): 3.1, 2.9, 3.4, and 3.6, and resulting in lowest FCM for the barley-brewers dried grains diet. Milk protein was not altered by treatment. These data suggest that responses to varying protein degradability can be altered by rate of starch breakdown in the rumen.     

Enhancing the selenium content of bovine milk through alteration of the form and concentration of selenium in the diet of the dairy cow

Since estimated dietary selenium intake in the UK has declined steadily from around 60 µg day^?1 in 1975 to 34 µg day^?1 in 1997, there is a need to increase selenium intake from staple foods such as milk and milk products. An experiment was therefore done to investigate the relationship between dietary source and concentration of selenium and the selenium content of bovine milk. In a 3 × 3 factorial design, 90 mid‐lactation Holstein dairy cows were supplemented over 8 weeks with either sodium selenite (S), a chelated selenium product (Selenium Metasolate?) (C) or a selenium yeast (Sel‐Plex?) (Y) at three different dietary inclusion levels of 0.38 (L), 0.76 (M) and 1.14 (H) mg kg^?1 dry matter (DM). Significant increases in milk selenium concentration were observed for all three sources with increasing inclusion level in the diet, but Y gave a much greater response (up to +65 µg l^?1) than the other two sources of selenium (S and C up to +4 and +6 µg l^?1 respectively). The Y source also resulted in a substantially higher apparent efficiency of transfer of selenium from diet to milk than S or C. Feeding Y at the lowest dietary concentration, and thus within the maximum level permitted under EU regulations, resulted in milk with a selenium concentration of 28 µg l^?1. If the selenium concentration of milk in the UK was increased to this value, it would, at current consumption rates, provide an extra 8.7 µg selenium day^?1, or 11 and 14% of daily recommended national intake for men and women respectively. Copyright © 2004 Society of Chemical Industry     

SELENIUM IN MILK OF DAIRY COWS FED THE NEWLY LEGALIZED 0.3 PPM SELENIUM-SUPPLEMENTED DIET

The permissible concentration of selenium which can legally be added to dairy cattle rations has recently been increased from 0.1 to 0.3 ppm. A feeding study with lactating dairy cows was conducted in which 0.3 or 0.6 ppm of selenium as sodium selenite was added to their diets for 23 and 26 days, respectively. Analysis of milk and blood throughout this period showed no consistent increase in the concentration of selenium in these fluids.     

Importance of considering body weight change in response to dietary protein deficiency in lactating dairy cows

Our objective was to quantify the contribution of body weight (BW) change to the overall response of lactating dairy cows to a shortage of dietary protein. Lactating Holstein cows (n = 166; 92 primiparous, 74 multiparous) with initial milk yield of 41 ± 10 kg/d were fed high and low-protein diets in 7 blocks. Blocks were repeated in the same crossover design with periods of 28 to 35 d. Production of 69 of the 166 cows (42 primiparous, 27 multiparous) was also measured in late lactation. Low-protein diets were 14% crude protein (CP) in peak lactation and 13% CP in late lactation and were formulated to contain adequate rumen-degradable protein to maintain rumen function but inadequate rumen undegradable protein for the average cow in this study. High-protein diets were 18% CP in peak lactation and 16% CP in late lactation and contained extra expeller soybean meal to meet metabolizable protein requirements. Body weight changes were used to predict body energy and protein changes, which were added to milk components to calculate total captured energy and protein. Fixed effects of diet, parity, treatment sequence nested in each block, treatment period nested in block, interaction of diet and parity, and the random effects of block and cow nested within block were included in the model to compare cow responses to diets within each lactation stage. In peak lactation, reducing protein from 18 to 14% resulted in estimated daily losses of 2.9 Mcal of milk energy, 2.2 Mcal of body energy, 127 g of milk protein, and 16 g of body protein. Therefore, BW loss accounted for 43% of the decrease in captured energy and 11% of the decrease in captured protein when cows were fed deficient protein. In late lactation, BW loss accounted for 51% of the decrease in captured energy and 14% of the decrease in captured protein when cows were fed deficient protein. We suggest that BW change should be considered when assessing cow responses to changes in dietary protein.     

Effect of distillers dried grains with solubles diet supplemented with rumen‐protected lysine and methionine on milk production and milk amino acids in the lactating cow

This study was to quantify the milk protein and amino acids (AA) in response to rumen‐protected lysine (Lys) and methionine (Met) supplementation in dairy cows fed distillers dried grains with solubles (DDGS) diet. Forty cows were divided into five dietary treatments: soybean meal diet (SM), DDGS diet and DDGS diets with 40 g/day Lys (DL), 20 g/ day Met dry matter (DM) and 20 g/ day Met plus 40 g/ day Lys (DLM), separately. Compared with SM, DL and DM groups, DLM group increased milk yield, 4% fat‐corrected milk, energy‐corrected milk yield and protein in milk. DDGS treatments increased total AA and the essential AA in milk. Results indicated that dietary DDGS increased intestinal supplies of Lys and Met.     

Isolipidic additions of fat from corn germ, corn distillers grains, or corn oil in dairy cow diets

Eight multiparous and 8 primiparous Holstein cows were used in a replicated 4 × 4 Latin square design with 4-wk periods to determine the effects on dairy cow performance of feeding corn germ (CG) compared with dried distillers grains with solubles (DDGS) or corn oil (CO). Four isolipidic dietary treatments were formulated: a control diet, a 14% corn germ diet (CGD), a 30% dry distillers grains with solubles diet (DGD), and a 2.5% corn oil diet (COD). All diets were formulated to contain 6.0% fat, with the fat in the control diet provided by a ruminally inert fat source. Dry matter intake was decreased by feeding the COD compared with the CGD; however, no difference in dry matter intake was observed among the control diet, the DGD, and the COD. Dietary treatments had no effect on milk yield, energy-corrected milk, or 4% fat-corrected milk. Feeding CG had no effect on milk fat percentage when compared with the control diet; however, milk fat percentage tended to decrease with DDGS and decreased with CO when compared with the CGD. Milk protein percentage decreased when cows were fed the COD compared with the control diet. Feeding CO tended to decrease milk fat yield compared with CG; however, dietary treatments had no effect on milk protein and lactose yield. Feed efficiency was not affected by dietary treatments and averaged 1.55 kg of energy-corrected milk/kg of dry matter intake. Feeding DDGS and CO increased the concentration of vaccenic and conjugated linoleic acid in milk fat. Concentrations of monounsaturated and polyunsaturated fatty acids in milk were increased in response to feeding the 3 corn coproducts. Fat from CG appears to be relatively protected in the rumen when compared with that from DDGS and CO and therefore will not affect the production of milk fat to the degree of the more available fat in DDGS and CO.     

Effects of dietary amino acid balance on the response of dairy cows to an increase of milking frequency from twice to three times daily

An experiment was conducted to examine how the response of dairy cows to a change from twice to three times-daily milking is affected by deficiencies in the dietary supplies of three amino acids, His, Met, and Lys. Six cows were used in a 6 x 6 Latin square with 14-d periods. The three dietary treatments were: grass silage and a cereal-based supplement containing feather meal as the sole protein supplement; the same silage-cereal diet supplying similar amounts of metabolizable and rumen-undegradable protein but with additional amounts of His, Met, and Lys in the form of fish meal; and the fish meal diet with additional metabolizable energy in the form of an additional 2 kg/d of sugar beet pulp. Within each of these dietary treatments, the cows were milked twice and three times daily, making a total of six treatments. When cows were given the feather meal diet, even though dietary metabolizable energy was in considerable excess, a deficiency of specific amino acids prevented any increase in milk yield in response to increasing the frequency of milking from twice to three times daily. In contrast, when cows consumed a similar level of excess metabolizable energy and a similar level of rumen-undegradable protein for which the protein was of better amino acid balance (fish meal), the increased frequency of milking led to increased yield of milk and milk protein.     

Effect of prepartum energy intake and postpartum protein source on plasma somatotropin and insulin in lactating cows

Forty-two Holstein cows were fed a high or low energy diet during the last third of lactation, then fed soybean meal or dried brewers grains in the subsequent lactation. Responses of plasma somatotropin and insulin to arginine were measured at 6 and 15 wk postpartum. Basal somatotropin, response area, and peak value were greater at 6 versus 15 wk of lactation. Insulation responses were greater at 15 wk of lactation. At 6 wk, basal somatotropin was higher (6.1 versus 4.1 ng/ml) in cows fed the low energy diet prepartum. Shape of somatotropin response curves at 6 wk differed between prepartum energy intakes, but response areas were similar. Plasma insulin at 6 wk tended to be higher (1.0 versus .7 ng/ml) in cows fed dried brewers grains. At 15 wk, both insulin and somatotropin response areas tended to be smaller for cows fed dried brewers grains, and shape of insulin response curves differed between protein sources. Of the observed hormonal responses to diet, only 6-wk plasma somatotropin was associated with differences in production parameters. Somatotropin secretion during early lactation appears to respond to prepartum changes in the energy status.     

Effect of dietary cobalt supplementation on cobalt metabolism and performance of dairy cattle

Three studies were conducted with dairy cattle fed diets with added Co. The first study examined cow age and added dietary Co on Co in liver and blood. Nonpregnant, nonlactating Holstein cows were blocked by age (2.5 or 6.5 yr) and assigned to either a control diet or a diet supplemented with 9 mg Co per day. The Co concentration of liver, taken on d 60, was not affected by dietary Co but was higher in the younger cows. The cytosolic fraction of liver contained the most Co, and the subcellular distribution of Co was not affected by total Co in liver. In a second study, Holstein cows were assigned to one of three treatments of dietary Co from 21 d prepartum until 120 d postpartum. There was an interaction of time x treatment x parity such that milk yield response to Co supplementation differed between multiparous cows and primiparous cows. Supplemental Co did not increase Co in serum, colostrum, milk, or liver. Primiparous cows secreted colostrum and milk with higher Co concentrations than did multiparous cows. Likewise, serum B12 levels were higher in primiparous than multiparous cows and declined with increasing days in milk (DIM). Serum Co also decreased from 7 to 120 DIM. In a final study, a Co supplement in the starter diet did not affect Co in serum or liver of young calves. In conclusion, supplemental dietary Co did not affect secretion of Co in milk, tissue retention, or subcellular distribution of Co within the liver. Primiparous and multiparous cows differed in their milk yield response to dietary Co supplementation.     

Lactation performance by dairy cows fed wet brewers grains or whole cottonseed to replace forage

Holstein cows starting at wk 8 of lactation were used to evaluate lactation performance when wet brewers grains, whole linted cottonseed, or starch-coated whole linted cottonseed (Easiflo) were substituted for forage. The wet brewers grains were added to diets to decrease forage neutral detergent fiber from 21% incrementally down to 15% while simultaneously decreasing nonfiber carbohydrate concentration from 40.3% down to about 33.8%. The cottonseed treatments all had similar concentrations of forage neutral detergent fiber (15%) and nonfiber carbohydrates (33.1 and 36.0%). Dry matter intake and milk production were similar across treatments. Milk fat percentage was decreased for Easiflo versus whole linted cottonseeds, but no other responses were detected. The current National Research Council (NRC) energy model was evaluated using individual cow data that were averaged over the entire 16-wk treatment period. For treatment means, the output of energy averaged 99% of the net energy of lactation intake, indicating very good corroboration of the model to account for energy usage for a group of cows. However, the ability to predict energy usage for individual cows was less accurate based on the comparison of residuals of observed and predicted body weight change regressed against predicted body weight change, apparently because of compounding of random errors in this prediction, which was alleviated over a larger number of observations. These results also corroborate current NRC guidelines for minimum forage neutral detergent fiber concentrations for lactating cows past the calving transition period.