Including 8 hours of access to alfalfa in 1 or 2 grazing sessions in dairy cows fed a partial mixed ration: Effects on intake, behavior, digestion, and milk production and composition

The aim of this study was to evaluate the inclusion of alfalfa grazing during 8 h continuous or partitioned in 2 separated sessions of 4 h after each milking, on nutrient intake, digestibility, ruminal fermentation, feeding behavior, milk production, milk composition, and milk fatty acid profile, in late-lactation cows fed a partial mixed ration (PMR). Twelve dairy cows (193 ± 83 d in milk, 584 ± 71 kg of body weight) were housed in individual outdoor pens and assigned to treatments according to a 3 × 3 Latin square design replicated 4 times. The treatments were as follows: (1) control (T0), cows were fed a total mixed ration (TMR) provided ad libitum 20.0% crude protein (CP), 32.2% neutral detergent fiber (NDF); (2) fed a diet combining a PMR which had the same ingredient composition as the TMR (60% of ad libitum intake) + 1 session of 8 h of pasture (T8), continuous grazing alfalfa (Medicago sativa; 20.6% CP, 35.8% NDF) after the p.m. milking; and (3) PMR (60% of ad libitum intake) + 2 daily sessions of 4 h of access to pasture after each milking (T4+4). The experiment lasted 57 d and was divided into 3 periods of 19 d each. The first 12 d of each period was used for diet adaptation, and the last 7 d was used for data collection. No differences among treatments were observed for any of the productive variables, feeding efficiency, or purine derivatives excretion. Cows in T0 had greater intake and apparent digestibility of dry matter, organic matter, and nonfibrous carbohydrates compared with T4+4 and T8. Compared with T0, alfalfa grazing increased the concentration of C18:1 trans-11 and decreased those of C16:0 and C17:0 in milk fat. Cows in T4+4 consumed 1.1 more kg DM/d of alfalfa and N provided by alfalfa in the diet was 3 percentage points higher compared with T8 cows (266 vs. 229 g/d, respectively). In addition, T4+4 cows had a greater daily range of ruminal pH than T8 (0.73 vs. 0.93), and the highest concentrations of NH3-N were recorded during the a.m. grazing session while in T8 cows it occurred during the night. In conclusion, including 8 h of alfalfa grazing in T8 and T4+4 treatments allowed the substitution between 35.8 and 38.7% of the total dry matter intake (DMI) of a PMR (with a similar CP concentration to alfalfa) for pasture, maintaining milk solids production and increasing the C18:1 trans-11 of milk fat compared with a TMR in mid late-lactation cows. In an herbage plus PMR diet, splitting the 1 continuous grazing session of 8 h into 2 sessions of 4 h increased the proportion of energy and N provided by alfalfa pasture and reduced PMR intake, without modifying the total nutrient intake or productive performance of cows.

Geographical and seasonal variation in iodine content of cow's milk in the UK and consequences for the consumer´s supply

BACKGROUND

Dairy products provide a crucial source of dietary iodine for the majority of the UK population, contributing approximately 30-40 % of daily intake. Fluctuations in the iodine content of purchased milk both seasonally and annually implies potential fragility of iodine supply likely through fluctuating supplementation practices in cow herds. We set out to establish the level of national variation in herds and identify factors which might impact milk iodine content.

METHODS

Milk samples were obtained from 98 herds across the UK via the National Milk Laboratories in August and December 2016. Iodine concentration of samples was measured using ICP-MS. Milk samples and feed intake data were additionally taken from 22 cows from the University of Nottingham (UON) dairy herd.

RESULTS

There was considerable variation in milk iodine content from < 0.012 (Limit of Detection) to 1558 μg L^-1, with a summer median of 197 μg L^-1 and winter median 297 μg L^-1. Overall, winter values were higher than summer counterparts (P < 0.001) and this held true for samples taken from the North West (P = 0.002) and South West (P = 0.006) but not for other regions studied. Data from the UON herd showed a negative relationship between iodine content and milk yield (P = 0.03) and we found that milk iodine content varied considerably despite apparently similar iodine intakes.

CONCLUSIONS

Regional differences in milk iodine concentration between summer and winter suggests that feeding practices are far from uniform across the country. The negative association observed between iodine concentration and milk yield in UON samples, suggests that reduced summer values may be influenced by dilution in addition to seasonal differences in concentrate feed provision.

Hay quality and intake by dairy cows. 2. Predicting feed intake with consumer-demand models

Daily food intake is the single most important factor affecting milk production by dairy cows. However, an animal’s choice of food depends not only on the nutritional characteristics of the food in question, but also on the nutritional characteristics of other available foods. Any prediction of intake should be based on the nutritional characteristics of all foods on offer. However, when the initial food-preference experiment possesses a control-specific design (i.e. experiments that include only a limited number of control foods for comparison) it is apparent that the prediction of future food choices must include the same controls as the initial experiment underpinning the prediction model. This requirement is clearly impractical. By drawing an analogy between animal food preference and economic choice, the total and relative dry matter intake of two oaten hays was modelled on their nutritive characteristics by estimating a consumer-demand model (here a generalised additive model representation of a direct bundle good model) from experimental data offering hays to lactating cows (adj-R2 > 80%; where adj-R2 is the value adjusted for the number of predictor terms in the model). To negate the problem of control-specificity, a simplex interpolation was developed to construct and test predictions of hay intake for a second food-preference experiment (adj-R2 > 53%; correlation between predictions and actual intakes = 76%). To improve prediction accuracy and avoid control-specificity, it is recommended that future preference experiments be designed to exclude control-specificity by mimicking fractional factorial designs, supported by a two-stage approach to select a cost-effective number of comparisons. Our approach to predicting food intake may be extended to a choice between more than two foods, and to combinations of foods other than oaten hays.

Effect of hyperketonaemia, feeding frequency and intake of concentrate and energy on milk yield in dairy cows

The effects of acetone concentration in milk, feeding frequency, and intake of concentrates and energy in total diet on milk yield were studied in 38624 lactations from 474 herds during 3 years. Herd-related data on feeding factors were collected once per indoor feeding period. Milk acetone concentrations higher than 0·40 mmol/l were deemed to denote hyperketonaemia, whether subclinical or clinical. The lactation curves of ketotic cows had an abnormal shape, with an inverted peak in early lactation. Most of the reduction in milk yield took place during the first 100 days of lactation with an estimated loss of proportionately 0·085 (acetone concentration ≤0·40 v. >2·00 mmol/l). The loss in 200-day milk yield was estimated to 328 kg 40 g/kg fat-corrected milk (FCM) at an overall mean of 5056 kg. If a herd's performance is monitored by lactation curves, a low peak — and hence an apparently high persistency – can indicate a ketosis problem. More frequent feeding of concentrates was correlated with a proportionately 0·033 to 0·074 higher milk yield in multiparous cows, but inconsistent between years. A more variable proportional response (−0·035 to 0·131) was observed in primiparous cows depending on interactions with, for example, breed. A greater total energy supply, including a larger amount of concentrate (maximum in lactation), was correlated with a higher milk yield, about 0·06 kg FCM per day per MJ metabolizable energy and 0·5 kg FCM per day per kg concentrate, respectively. However, increased feeding of concentrates at calving (parity 1) and 15 days after calving (multiparous cows) was correlated with decreased milk yield, by about −0–3 and −0–5 kg FCM per day per kg concentrate, respectively.

A herd health approach to dairy cow nutrition and production diseases of the transition cow

This paper presents a practical, on-farm approach for the monitoring and prevention of production disease in dairy cattle. This integrated approach, should be used in an interdisciplinary way by farmers, veterinarians, nutrition advisors and other relevant professionals for the improvement of animal health and welfare and producer profitability. The key areas that form the basis for this approach are body condition score management, negative energy balance, hypocalcaemia, rumen health and trace element status. Monitoring criteria are described for each of these key areas, which when considered collectively, will facilitate the assessment of dairy cow health with regard to clinical and subclinical disease. The criteria, which are informed by published scientific literature, are based on farm management and environmental factors, clinical data, milk production records, dietary analysis, and assessment of blood and liver concentrations of various metabolites or trace elements. The aim is to review the efficacy of production disease control measures currently in place, and if necessary to modify them or formulate new ones.

Chewing activity, saliva production, and ruminal pH of primiparous and multiparous lactating dairy cows

Four multiparous (MP) and four primiparous (PP) ruminally cannulated lactating Holstein cows were used in a double 4 x 4 Latin square design to study the chewing behavior, saliva production, and ruminal pH of cows in the first or subsequent lactation. Cows were fed one of four diets; three total mixed rations containing 40, 50, or 60% silage (DM basis), and a separate ingredient diet containing 50% concentrate. Dry matter intake was higher for MP cows than for PP cows (19.2 vs. 17.1 kg/d) but not as a percentage of body weight (2.97 +/- 0.06%). Multiparous cows spent more time eating than PP cows (260 vs. 213 min/d, respectively), even after adjustment for dry matter intake (13.8 vs. 12.4 min/kg DM). Multiparous cows also spent more time ruminating per day than PP cows (560 vs. 508 min/d, respectively). Eating salivation rate was not affected by parity, but resting salivation rate was higher for MP cows than for PP. Although MP cows spent more time chewing than PP cows, total daily saliva production was only numerically higher for MP cows because the increase in saliva produced during chewing was accompanied by a decrease in saliva produced during resting. Furthermore, pH profiles tended to be lower for MP cows than for PP cows. Multiparous cows may have a greater risk of incurring acidosis than PP cows because increased salivary secretion associated with increased chewing may not sufficiently compensate the increment of fermentation acids produced in the rumen due to high feed intake.

Diurnal variation in pH reduces digestion and synthesis of microbial protein when pasture is fermented in continuous culture

Many models of digestion assume steady-state conditions and do not account for diurnal variation in the rumen environment. This experiment examined the relationships between diurnal pH, pasture digestion, and microbial protein synthesis. Four dual-flow continuous culture fermenters were used to test the effect of increasing time at suboptimal pH on parameters of digestion. Fermentation of high quality pasture was controlled at pH 5.4 (suboptimal) for four intervals during each 24-h period (0, 4, 8, and 12 h) according to a 4 x 4 Latin square design. During the remainder of each day, pH was controlled at 6.3 (optimal). Samples were collected during the last 3 d of each of the four 9-d experimental periods. A negative quadratic relationship was observed between time at suboptimal pH and apparent digestibility of organic matter and dry matter. The largest reduction in digestibility of organic matter, dry matter, and neutral detergent fiber was exhibited after 4 h at suboptimal pH. A negative linear relationship was found between time at suboptimal pH and microbial N flow, with the greatest decline in microbial N flow occurring at 12 h at suboptimal pH. These results suggest that the period of time that pH is below optimal may be more critical for digestion than the relationship between mean daily pH and optimal pH. Modeling non-steady-state ruminal conditions to account for diurnal variation in the ruminal environment may improve the prediction of digestion, especially fiber.

Effects of extrusion of grain and feeding frequency on rumen fermentation, nutrient digestibility, and milk yield and composition in dairy cows

The effect of corn extrusion and feeding frequency on ruminal and postruminal digestibility and milk yield was studied in cows fed a high concentrate diet. Four Israeli Holstein cows fitted with rumen and abomasal cannulas were used. The experiment was arranged as a 2 x 2 factorial design, with two diets and two feeding frequencies (two or four meals per day). One diet contained 40% ground corn. In the second diet, half of the ground corn was replaced with extruded corn. Feeding cows the extruded versus ground corn diet decreased ruminal ammonia N and plasma urea N concentrations, increased postruminal digestibility of nonstructural carbohydrates, reduced dry matter intake, decreased yield of milk and milk components, and increased efficiency of milk energy and milk protein synthesis. The inclusion of extruded corn in the diet did not affect ruminal volatile fatty acid. Increasing the feeding frequency reduced the diurnal variation in ruminal pH, ruminal ammonia, and plasma urea, and increased dry matter intake--considerably more in the cows fed ground versus extruded corn--and improved postruminal organic matter, nonstructural carbohydrate, and crude protein digestibility. Total tract digestibility of organic matter and crude protein and milk yield and composition were also increased when cows were fed four versus two meals. Concurrent with the feeding frequency and grain processing effect, an increase in rumen-undegradable protein flow was related to increased digestion of nonstructural carbohydrate postruminally (r = 0.54). We concluded that for cows fed high-starch diets more frequent meals are useful for improving postruminal digestibility and milk yield and composition.

Effects of information technology on dairy farms in The Netherlands: an empirical analysis of milk production records

This study empirically quantified the effects of the adoption of an automated concentrate feeder, on-line measurement of milk production, and activity measurement on milk production and reproduction. The data comprised annual results of Dutch farms operating in a milk quota system from 1987 to 1996; data included both adopters and nonadopters as well as farm results before and after adoption. The use of an automated concentrate feeder improved the annual carrier production of milk, milk protein, and milk fat (102, 4.95, and 5.52 kg per cow, respectively). In contrast, on-line measurement of milk production did not significantly affect milk production records. Calving interval was shortened by 5.7 d after the adoption of an activity measurement system but was not affected by the adoption of an automated concentrate feeder or by the measurement of on-line milk production.

Effect of the synchronization of the degradation of dietary crude protein and organic matter and feeding frequency on ruminal fermentation and flow of digesta in the abomasum of dairy cows

Four Holstein cows in midlactation were equipped with ruminal and abomasal cannulas and used to study the effect of synchronized degradation of crude protein (CP) and organic matter (OM) and feeding frequency on digestion and outflow of nutrients. A 4 x 4 Latin square design was used. Diets were arranged in a 2 x 2 factorial design; the four diets contained high ruminally degradable OM and high ruminally degradable CP, high ruminally degradable OM and low ruminally degradable CP, low ruminally degradable OM and high ruminally degradable CP, and low ruminally degradable OM and low ruminally degradable CP. In each period, cows were fed four times daily from d 1 to 14 and two times daily from d 15 to 28. Mean daily ruminal ammonia N concentration was reduced by high ruminally degradable OM, low ruminally degradable CP, and twice daily feeding. Fluctuation in ruminal ammonia N was lower when cows were fed four times daily than when cows were fed twice daily. Plasma urea N concentrations were lower for cows fed diets that were high in ruminally degradable CP. Higher CP flow in the abomasum was found for cows fed the diet containing high ruminally degradable OM and low ruminally degradable CP. Microbial dry matter and CP flow to the abomasum were higher for cows fed twice daily than for cows fed four times daily. Flow of OM in the abomasum was not altered by concentrations of ruminally degradable OM or CP. These results suggest that the available energy in the rumen (ruminally degradable OM) is the most limiting factor for ruminal N utilization under our experimental conditions. Use of these data may improve the prediction of plasma urea N.

Evaluation of a mobile computerized grain feeder for lactating cows grazing grass pasture

The objective of this study was to evaluate a mobile computerized grain feeder for use to feed individually Holstein cows grazing grass pasture. Thirty-two Holstein cows averaging 95 d of lactation and 39.3 kg/d of milk were rotationally grazed on predominantly Dactylis glomerata pastures for 9 wk starting in early May. Cows were blocked according to parity, days of lactation, and milk yield. Cows were randomly assigned to a control group in which cows were individually fed grain twice daily at milking or to a group that was offered grain four times daily using a mobile grain feeder in the pasture. Cows in both groups were offered 1 kg of grain/3 kg of milk; pasture was the only source of forage. Cows fed using the mobile grain feeder consumed less grain than did control cows (9.3 vs. 11.3 kg/d) and tended to yield less milk, but with a higher fat content. A separate analysis was conducted using data from only those cows that were fed using the mobile grain feeder and that consumed, in four relatively equal amounts, at least 75% of the allotted grain of their respective pairmates (7 per group) in the control group. When cows that were using the mobile grain feeder consumed amounts of grain comparable with that of the controls, more frequent grain feeding did not alter milk yield or composition. Plasma samples (five per cow per treatment) were collected at 2-wk intervals to measure glucose, urea N, and nonesterified fatty acids (NEFA). Plasma glucose and urea N were not affected by treatment and averaged 54.9 and 19.9 mg/ dl for all cows, respectively. Cows fed grain using the mobile feeder had higher (212.4 vs. 170.5 meq/L) concentrations of NEFA than did control cows, but, when cows consumed greater than 75% of their allotted grain from the mobile feeder, concentrations of NEFA were similar. The mobile grain feeder can be used to feed cows individually on pasture; however, adaptation of the cows to the mobile grain feeder appears to be important.

Modeling ruminal pH fluctuations: interactions between meal frequency and digestion rate

A steady periodic analysis of ruminal carbohydrate digestion was developed to predict the effects of diet and frequency of eating on ruminal pH fluctuation. Tests of the model against previous data showed that pH fluctuations were too large when previously published rates of carbohydrate digestion were used but were improved using rates from an in vitro gas production system, which were lower. With the original digestion rates, the minimum meal frequency to maintain steady-state conditions in the rumen increased from 4 to 12 meals/d as dietary effective neutral detergent fiber (NDF) decreased from 34 to 6% of dry matter (DM); with the revised rates, the minimum frequency was 3 to 6 meals/d, respectively. The minimum effective NDF to maintain a pH value above 6.0 increased from 14 to 23% of DM as meal frequency decreased from steady state to 2 meals/d using the original rates; with the revised rates, the minimum effective NDF was slightly smaller, increasing from 13 to 21% of DM, respectively. Effects of DM intake and body weight on pH fluctuation were minor, and dietary buffers, when used at rates less than 1%, did not reduce fluctuation. Different methods of calculating mean ruminal pH yielded different results for the effect of meal frequency on mean pH.

Microbial and animal limitations to fiber digestion and utilization

The ruminal microbial populations attack, degrade and ferment structural carbohydrates in forage cell walls and thereby provide volatile fatty acids and protein to the host animal. Microbial colonization of fiber is quite rapid; however, the rate and extent to which fiber is degraded is determined to a considerable degree by factors such as microbial accessibility to substrate, physical and chemical nature of the forage and kinetics of ruminal digestion. The physical and chemical nature of forages can present a barrier to their complete digestion in the rumen, especially the association of lignin with polysaccharide constituents. Adhesin proteins allow bacteria with cell-bound enzymes to come into intimate contact with their substrates, ensuring that the degradation products are preferentially available. Research on various fibrolytic enzymes and cellulose binding domains may allow for the transfer of novel genetic material to bacteria for enhancing the hydrolysis of plant cell walls. Fungi may also play an important synergistic role in the ruminal digestion of forages by physically disrupting the lignified stem tissue. This allows the ruminal microbes greater access to the plant stem and the digestible portions of the plant. New developments in fiber utilization by ruminants are currently under investigation and include genetic manipulation of ruminal bacteria, chemical and biological treatments of forages, and manipulation of dietary inputs and feeding management.

Effect of the degradation of organic matter and crude protein on ruminal fermentation in dairy cows

The potential of the dacron bag technique to assess fluctuations in ruminal metabolites was studied using 40 Israeli-Friesian dairy cows assigned to an experiment with a 2 x 2 factorial design. Diets contained a low (62%) or high (65%) percentage of ruminally degradable CP and a low (55%) or high (59%) percentage of ruminally degradable OM. Metabolites were monitored before feeding and at 3 and 6 h postfeeding. Before feeding, total VFA and propionate were higher, and acetate and pH were lower, in diets containing a high percentage of ruminally degradable OM than in diets containing a low percentage of degradable OM. By 3 H postfeeding, acetate, butyrate and pH were lower, and propionate was higher, in the diets containing a high percentage or ruminally degradable OM than in the diets containing a low percentage of ruminally degradable OM. By 6 h postfeeding, propionate was higher, and acetate was lower, in diets containing a high percentage of ruminally degradable OM than in diets containing a low percentage of ruminally degradable OM. In the diets with a high percentage of ruminally degradable OM, before feeding and by 3 h postfeeding, ammonia concentrations were higher and lower, respectively, relative to the diets containing a low percentage of degradable OM. Milk yield and composition and DMI were similar among treatments. The correlation was good between the degradability data obtained by the dacron bag technique and the meal-induced variations in ruminal metabolites. The lack of a positive yield response to controlled fluctuations in ruminal metabolites may be related to surplus CP intake.

[Simulation of nutrient dynamics in the rumen of sheep and cattle considering the feed composition, level of feed intake and feeding frequency. 2. Model validation]

A mathematical model of rumen fermentation processes was validated with 65 sheep experiments and 45 cattle experiments, respectively. Further, it was shown how the model reacts when the feed composition, the level of feed intake and the feeding frequency was changed. The model predictions were satisfactory for the digestibility of organic matter and neutral detergent fibre (NDF) in rumen, the production of volatile fatty acids and the non-ammonia-N (NAN) flow to duodenum. The partition of NAN in microbial and feed N was estimated with lower reliability. The effects of variation of feeding level, feeding frequency and roughage quality (crude protein, lignin) on digestion processes have been simulated correctly. On the other hand, the effects of the proportion of roughage to concentrate have not been reproduced sufficiently with the mechanisms included in the model. To make correct predictions in this area too, it is necessary to integrate the rumen pH and its effects on rumen processes into the model. A mechanistic approach for estimation of the velocity constants for passage of substances out of the rumen would improve the model.

Effects of feeding practices on milk fat concentration for dairy cows

Thirty-seven dairy farms, using high producing (7500 kg/yr per cow on average) Montbéliarde cows that were fed hay-based rations, were included in a detailed survey involving the structure of the farm and the herd, the quality of forage, the feeding practices in winter and summer, and genetic characteristics of the cows (breeding values and herd effects). These data were used to analyze variation in milk fat concentration among farms, particularly variation linked to environmental factors, as assessed by the herd effect. When farms were ranked according to herd effect of fat concentration, farms with the highest herd effects fed concentrate to cows in rolled form, distributed forage before or with the concentrate, and provided hay in the trough in summer. The effects of such practices on digestive phenomena in the rumen are discussed. This study supported the use of herd effects to identify factors related to variation in dairy cow performance.

Nutrient requirements versus supply in the dairy cow: strategies to account for variability

Dairy producers must overcome substantial challenges to achieve milk outputs > 14,000 kg of milk/yr per cow within the next decade. To obtain high productivity, a more complete comprehension of the dynamics of metabolism, nutrient utilization, and nutrient absorption will enable better prediction of the efficiency of utilization of these nutrients. A better understanding of the dynamics of rumen function and a more accurate prediction of nutrient flow from the rumen are necessary. Grouping strategy and group feeding behavior influence cow productivity and farm profitability. Understanding of the variance of individual cow responses to management practice is critical. Feeding system design and management and diet formulation techniques need to be developed that recognize the dynamic nature of cow physiology and the variability in feedstuffs and cow requirements. These concepts need to be integrated into total farm management and require the use of new computer modeling technologies.

Feeding sequence and strategy effects on ruminal environment and production performance in first lactation cows

Three primiparous cows were assigned randomly to a 4 x 4 incomplete Latin square to evaluate ruminal characteristics (Experiment 1) with the following feeding strategies: strategy A, supplement (protein), forage plus high moisture ear corn (energy), protein; strategy B, energy plus protein, forage, energy plus protein; strategy C, forage plus energy, protein, forage plus energy, protein; and strategy D, forage, energy plus protein, forage, energy plus protein. In Experiment 2, 36 cows were fed diets similar to those in Experiment 1 from wk 4 through 19 postpartum. Cows fed diets according to strategy A had the highest and strategy D the lowest mean ruminal pH. Diurnal variation in ruminal pH was less with cows fed diets using strategies A and B than C and D. Other ruminal parameters were not significantly different. In Experiment 2, cows fed according to strategy B had higher DMI than those fed according to other strategies. Energy and protein fed together and separately from forage, regardless of sequence, increased milk fat percentage compared with protein fed separately. Milk production and protein yield tended to be highest when protein was fed separately, regardless of sequence to forage. Strategic feeding of protein and energy sources in relation to forage influenced some ruminal and production measurements in primiparous cows.

Effects of feeding frequency on ruminal parameters, plasma insulin, milk yield, and milk composition in Holstein cows

Two experiments were conducted to determine the effects of frequency of feeding on ruminal fermentation, blood parameters, milk yield, and milk composition in cows fed a 60% pelleted concentrate and 40% chopped alfalfa hay (DM basis) diet. In Experiment 1, four ruminally cannulated cows were fed concentrates in 12 equal portions at 2-h intervals or in two equal portions at 0500 and 1500 h in a crossover design. In Experiment 2, treatments were as in Experiment 1 plus an additional treatment consisting of a total mixed diet fed at 2-h intervals in a 3 x 3 Latin square design. All treatment periods were 2 wk. In Experiment 1, increased frequency of concentrate feeding tended to result in elevated ruminal pH and increased acetate to propionate ratio. Plasma insulin concentration tended to be higher (1.54 vs. 1.04 ng/ml) and milk fat percentage increased from 2.21 to 2.60% for 2 and 12 times daily feeding, respectively. In Experiment 2, frequency of feeding concentrate or total mixed diet did not affect ruminal and blood parameters or milk yield. In both experiments, milk protein and lactose concentrations were not influenced by feeding frequency. Results suggest that where intake is kept constant, increased feeding frequency will not influence milk yield but could result in elevated milk fat percent in animals fed fat-depressing diets.