The effects of feeding a partial mixed ration plus a top-dress before feeding on milk production and the daily rhythm of feed intake and plasma hormones and metabolites in dairy cows

Total mixed rations (TMR) are commonly fed to dairy cows with a goal of reducing ruminal acidosis, but the daily pattern of feed intake has major implication for rumen fermentation and postabsorptive physiology. Generally there is low feed intake during the overnight period and high intake after feeding and during the afternoon. The objective of this study was to determine if feeding a partial mixed ration (PMR) plus a high starch top-dress before feeding of the PMR would improve production and modify key daily rhythms. The top-dress was fed before feeding as ruminal starch is at a nadir and amylolytic capacity is expected to be low. Ten Holstein cows were used in a crossover design with 14-d periods. Cows were housed in tie stalls with feed tubs and feed weight was recorded every 10 s for observation of feeding behavior. Treatments were a control TMR fed once per day at 0900 h or a partial mixed ration plus a top-dress (PMR+TD). The top-dress was fed at 9.5% of DMI offered at 0800 h and contained steamflaked corn, canola meal, and nonprotein nitrogen. No interaction was observed between treatment and milking time. Milk yield tended to be decreased 1.1 kg and milk fat yield was decreased 70 g/d by PMR+TD. Milk fat preformed fatty acids were decreased and no effect was observed of treatment on trans-10 C18:1 or other indicators of biohydrogenation-induced milk fat depression. No effect was observed of treatment on meal parameters including meal size and number. The PMR+TD increased total-tract neutral detergent fiber (NDF) digestibility by 1.2 percentage points. Treatment changed the daily pattern of fecal NDF and indigestible NDF, indicating changes in rumen function over the day. No effect was observed on plasma glucose, but the amplitude of the daily rhythm of insulin was increased by PMR+TD. The PMR+TD also increased plasma nonesterified fatty acids and decreased blood urea nitrogen across the day. Core body temperature is entrained by the central biological clock and its phase was advanced 42 min and its amplitude slightly increased by PMR+TD. In conclusion, the top-dress appears to have modified the central circadian rhythm and plasma insulin and blood urea nitrogen. This demonstrates that timing of feeding can be used to manage daily rhythms of the dairy cow, although the optimal timing requires further investigation.     

Dietary restriction improved feed efficiency of inefficient lactating cows

The aim of this study was to reduce voluntary dry matter intake (DMI) to increase feeding efficiency of preclassified inefficient (INE) dairy cows through restricted feeding. We studied the effects of dietary restriction on eating behavior, milk and energy-corrected milk (ECM) production, in vivo digestibility, energy balance, and measures of feed efficiency [residual feed intake (RFI) and ECM/DMI]. Before the experiment, 12 pairs of cows were classified as INE. The 2 dietary treatments consisted of ad libitum feeding versus restricted feeding of the same total mixed ration containing 36.5% roughage. Inefficient cows fed the restricted total mixed ration had a shorter eating time and lower meal and visit frequency, but a similar rate of eating, meal size, and meal duration compared with INE cows fed ad libitum. Compared with the INE cows fed ad libitum, restricted INE cows had 12.8% lower intake, their dry matter and neutral detergent fiber digestibility remained similar, and their ECM yield was 5.3% lower. Feed efficiency, measured as RFI, ECM/DMI, and net energy retained divided by digestible energy intake, was improved in the restricted INE cows as compared with the ad libitum cows. Our results show that moderate DMI restriction has the potential to improve feed efficiency of preclassified INE cows.     

Effect of feeding frequency of a total mixed ration on the performance of high-yielding dairy cows

Forty Finnish Ayrshire cows, 16 primiparous and 24 multiparous, were randomly assigned to 1 of 2 treatments (FF1 or FF5). Total mixed ration (TMR) was fed once a day on the FF1 treatment and 5 times a day on the FF5 treatment. The experiment began at calving and continued to wk 28 of lactation. The TMR consisted of a grass silage and concentrate mix. The amount of concentrate in the TMR was 51% on a DM basis. The feeding frequency had no effect on milk or energy-corrected milk yields or on milk composition. The average energy-corrected milk yield was 32.8 kg/d on the FF1 treatment and 32.5 kg/d on the FF5 treatment. The less frequent feeding increased the dry matter intake (DMI) of cows. The average DMI during the experiment was 20.9 kg/d on the FF1 treatment and 19.9 kg/d on the FF5 treatment. The difference in DMI was due to the differences in DMI of the mature cows. Energy and protein conversion tended to be lower with feeding once a day compared with feeding 5 times a day. The cows’ feeding behavior was also observed. Cows fed 5 times a day tended to eat quite evenly after each delivery, whereas on the FF1 treatment there were 2 clear feeding peaks in the evening after the feed delivery. The time spent eating during the observation period was longer on FF5 than on FF1. The cows fed once a day spent more time lying than the cows fed 5 times a day. Based on the observations of feeding behavior, feeding a TMR 5 times a day seemed to be too frequent based on the increased restlessness and decreased lying time of the cows.     

Inclusion of calcium hydroxide-treated corn stover as a partial forage replacement in diets for lactating dairy cows

Chemical treatment may improve the nutritional value of corn crop residues, commonly referred to as corn stover, and the potential use of this feed resource for ruminants, including lactating dairy cows. The objective of this study was to determine the effect of prestorage chopping, hydration, and treatment of corn stover with Ca(OH)₂ on the feeding value for milk production, milk composition, and dry matter intake (DMI). Multiparous mid-lactation Holstein cows (n = 30) were stratified by parity and milk production and randomly assigned to 1 of 3 diets. Corn stover was chopped, hydrated, and treated with 6% Ca(OH)₂ (as-fed basis) and stored in horizontal silo bags. Cows received a control (CON) total mixed ration (TMR) or a TMR in which a mixture of treated corn stover and distillers grains replaced either alfalfa haylage (AHsub) or alfalfa haylage and an additional portion of corn silage (AH+CSsub). Treated corn stover was fed in a TMR at 0, 15, and 30% of the diet DM for the CON, AHsub, and AH+CSsub diets, respectively. Cows were individually fed in tiestalls for 10 wk. Milk production was not altered by treatment. Compared with the CON diet, DMI was reduced when the AHsub diet was fed and tended to be reduced when cows were fed the AH+CSsub diet (25.9, 22.7, and 23.1 ± 0.88 kg/d for CON, AHsub, and AH+CSsub diets, respectively). Energy-corrected milk production per unit of DMI (kg/kg) tended to increase with treated corn stover feeding. Milk composition, energy-corrected milk production, and energy-corrected milk per unit of DMI (kg/kg) were not different among treatments for the 10-wk feeding period. Cows fed the AHsub and AH+CSsub diets had consistent DMI over the 10-wk treatment period, whereas DMI for cows fed the CON diet increased slightly over time. Milk production was not affected by the duration of feeding. These data indicate that corn stover processing, prestorage hydration, and treatment with calcium hydroxide can serve as an alternative to traditional haycrop and corn silage in diets fed to mid-lactation dairy cows.     

Impact of alfalfa maturity and preservation method on milk production by cows in early lactation.

Ninety-six cows in early lactation were used in two experiments to measure the impact of alfalfa maturity (early or midbud vs. early or midbloom) and method of forage preservation (silage vs. hay) on DMI and milk production. Silage diets were fed as TMR, and hay was fed separately from grain. All diets contained 60% alfalfa (dry basis) and were balanced for 19% CP. Maturity had little effect on milk production in either experiment. Adjusted milk production for early cut silage, late cut silage, early cut hay, and late cut hay were 33.6, 33.4, 30.7, and 32.1 kg/d for Experiment 1 and 38.1, 37.0, 35.0 and 35.0 kg/d for Experiment 2. Increased alfalfa maturity tended to reduce DMI. Cows fed the silage diets consumed 1.2 kg more DM and produced an average of 2.1 kg more milk daily in Experiment 1 than those fed the hay diets. All treatment groups consumed similar amounts of DM in Experiment 2; however, cows fed silage produced 2.6 kg/d more milk than those fed hay. Preserving alfalfa as silage and feeding in a TMR to cows in early lactation resulted in greater milk production via increased DMI or improved feed efficiency compared with preserving alfalfa as hay and feeding grain separately.     

Adding liquid feed to a total mixed ration reduces feed sorting behavior and improves productivity of lactating dairy cows

This study was designed to determine the effect of adding a molasses-based liquid feed (LF) supplement to a total mixed ration (TMR) on the feed sorting behavior and production of dairy cows. Twelve lactating Holstein cows (88.2±19.5 DIM) were exposed, in a crossover design with 21-d periods, to each of 2 treatment diets: 1) control TMR and 2) control TMR with 4.1% dietary dry matter LF added. Dry matter intake (DMI), sorting, and milk yield were recorded for the last 7 d of each treatment period. Milk samples were collected for composition analysis for the last 3 d of each treatment period; these data were used to calculate 4% fat-corrected milk and energy-corrected milk yield. Sorting was determined by subjecting fresh feed and orts samples to particle separation and expressing the actual intake of each particle fraction as a percentage of the predicted intake of that fraction. Addition of LF did not noticeably change the nutrient composition of the ration, with the exception of an expected increase in dietary sugar concentration (from 4.0 to 5.4%). Liquid feed supplementation affected the particle size distribution of the ration, resulting in a lesser amount of short and a greater amount of fine particles. Cows sorted against the longest ration particles on both treatment diets; the extent of this sorting was greater on the control diet (55.0 vs. 68.8%). Dry matter intake was 1.4 kg/d higher when cows were fed the LF diet as compared with the control diet, resulting in higher acid-detergent fiber, neutral-detergent fiber, and sugar intakes. As a result of the increased DMI, cows tended to produce 1.9 kg/d more milk and produced 3.1 and 3.2 kg/d more 4% fat-corrected milk and energy-corrected milk, respectively, on the LF diet. As a result, cows tended to produce more milk fat (0.13 kg/d) and produced more milk protein (0.09 kg/d) on the LF diet. No difference between treatments was observed in the efficiency of milk production. Overall, adding a molasses-based LF to TMR can be used to decrease feed sorting, enhance DMI, and improve milk yield.     

Mitigation of variability between competitively fed dairy cows through increased feed delivery frequency

The objective of this study was to determine whether increased frequency of total mixed ration (TMR) delivery could mitigate the effects of feed bunk competition on the behavior and productivity of individual lactating dairy cows within a group. We hypothesized that, for competitively fed cows, a greater frequency of TMR delivery would improve access to feed, and reduce individual variability in behavior, meal patterns, and production between cows. Sixteen lactating Holstein dairy cows (first lactation = 4, second lactation = 5, ≥ third lactation = 7) averaging 72 ± 35 d in milk and producing 42 ± 6 kg of milk/d at the start of the trial, were categorized as either young (≤ second lactation) or mature (≥ third lactation) and paired to maximize difference in parity. Pairs were housed 4 at a time and competitively fed a TMR at a ratio of 2 cows:1 feed bin. Cow pairs were exposed, in a crossover design, to each of 2 feed delivery frequency treatments: low (2×/d) and high (6×/d) frequency. Treatments were applied for 10 d, with dry matter intake (DMI), feeding behavior (feeding time, feeding rate, and meal patterns), and replacement frequency for each cow recorded using an automated feed intake system on d 6 to 10 of each period. Rumination time, feed sorting, lying behavior, and productivity were also measured for this period. Variability in behavior within pairs of cows was determined by averaging the absolute difference within each pair over the recording period to provide 1 value per pair. Frequency of TMR delivery did not affect feeding time, feeding rate, DMI, replacement frequency, feed sorting, or productivity. At the high delivery frequency, there was a tendency for rumination time to increase [low = 519.3; high = 544.3 min/d; standard error of the difference (SED) = 11.32], and to be more variable within pairs (low = 38.0, high = 50.0 min/d; SED = 5.57). Cows also had longer lying bouts at the high delivery frequency (low = 53.0; high = 55.5 min/bout; SED = 1.00). No differences in daily meal patterns were found between treatments; however, the average first meal following each feeding indicated that cows under the high delivery frequency spent less time, consuming smaller meals during peak feeding periods. Comparing the young and mature individuals within each treatment pair revealed that feeding rate (young = 0.16; mature = 0.19 kg/min; SED = 0.014) and DMI (young = 25.6; mature = 28.6 kg of DM/d; SED = 1.36) were lower for the young cows on both treatments. Meal frequency was greater in young cows (young = 9.0; mature = 7.5 meals/d; SED = 0.71) and meal size was greater in mature cows (young = 3.2; mature = 4.2 kg of DM/meal; SED = 0.32) across treatments. These results suggest that for cows fed at a high level of competition, increasing TMR delivery frequency from 2 to 6×/d led to consumption of shorter, smaller meals during peak periods of feed consumption. However, under these conditions, the relative parity of competitively fed cows had a greater effect on feeding behavior, meal patterns, and production than did the frequency of feed delivery.     

Supplementing additional cobalt as cobalt lactate in a high-forage total mixed ration fed to late-lactation dairy cows

Cobalt lactate is a highly soluble ruminal Co source. Prior research evaluating higher Co feeding rates demonstrated increased ruminal fiber digestion. Feeding high-forage (>70%) rations to late-lactation dairy cows to enhance income over feed cost could potentially benefit from higher ruminal-soluble Co inclusion rates to enhance ruminal fiber and nutrient digestibility. Twenty-four late-lactation [238 ± 68.8 d in milk (DIM) and 36.4 ± 5.4 kg/d milk] Holstein dairy cows (10 primiparous and 14 multiparous) were blocked by milk yield, DIM, and parity, and randomly assigned to 1 of 2 treatments. Treatments were (1) control, CoCO₃ total mixed ration (TMR) containing 12.5 mg/cow per day of cobalt (cobalt carbonate), and (2) cobalt lactate (Co-LAC), same CoCO₃ TMR but containing an additional 50 mg/cow per day of Co, via a 1% cobalt lactate product (CoMax, Ralco Inc.). The basal TMR was 70% forage [60% alfalfa baleage and 40% corn silage on a dry matter (DM) basis] and 30% of the respective experimental grain mix on a DM basis. Cows were fed the CoCO₃ TMR during the 7-d covariate period, followed by 4 wk of data collection when CoCO₃ and Co-LAC TMR were fed. Milk production (26.2 and 25.8 kg/d for CoCO₃ and Co-LAC, respectively) and dry matter intake (DMI; 22.9 and 23.1 kg/d) were similar for cows fed both Co treatments. Production of milk fat (1.02 and 1.09 kg/d), milk protein (0.87 and 0.91 kg/d), and lactose (1.17 and 1.26 kg/d) were similar for cows fed both treatments. Body weights (684 and 674 kg) were similar for cows fed both treatments. Rumen ammonia concentrations (15.8 and 12.3 mg/dL) were lower for cows fed Co-LAC compared with cows fed CoCO₃ (15.8 mg/dL). Ruminal molar acetate concentrations (59.5 and 61.1%) were greater for cows fed Co-LAC compared with cows fed CoCO₃. Feeding additional Co as cobalt lactate in the TMR did not enhance lactational performance (milk production, composition, DMI, or body weight changes) when fed a high-forage TMR but altered ruminal fermentation with decreased ruminal ammonia and increased ruminal acetate concentrations.     

Effects of organic acids in total mixed ration and feeding frequency on productive performance of dairy cows

This study aimed to evaluate the effects of organic acid (OA; Mold-Zap, Alltech, Nicholasville, KY) inclusion in the total mixed ration (TMR) and feeding frequency of TMR for lactating dairy cows on intake, total-tract apparent digestibility, sorting index, feeding behavior, ruminal fermentation, milk yield and composition, nitrogen balance, and serum metabolites. Twenty-four lactating Holstein cows, 4 with rumen cannulas, with (mean ± standard error) 247 ± 22.2 d in milk, 672 ± 14.6 kg of body weight, and 31.1 ± 1.09 kg of milk yield at the beginning of the experiment were used. The cows were distributed in a balanced and contemporary 4 × 4 Latin square experimental design and randomly assigned in a 2 × 2 factorial arrangement to evaluate OA [0 (OA?) or 0.5 (OA+) L of Mold-Zap/tonne of TMR on a natural matter basis] and feeding frequency of TMR offered once a day (1×) or twice a day (2×). Each experimental period lasted 21 d, with 14 d for acclimation and 7 d for data collection. The treatments were tested for TMR, in which its temperature was recorded every 2 h through a 24-h period in each experimental period. Organic acid-treated TMR showed a lower temperature during the 24-h period compared with nontreated TMR. The OA and feeding frequency had no effect on intake and total-tract apparent digestibility of dry matter and nutrients, aside from a tendency to increase neutral detergent fiber digestibility in cows fed 2×. Also, cows fed 1× tended to select more particles between 19 and 8 mm and refused particles smaller than 4 mm, whereas cows fed OA tended to select more particles smaller than 4 mm. Cows fed OA had greater milk yield and milk protein and lactose yields, but tended to have higher 3.5% fat-corrected milk yield. Neither treatment influenced ruminal and serum variables nor milk fat yield and milk production efficiency. Cows fed OA spent less time idling and tended to have lower rumination time, and tended to have higher time spent drinking water and eating, whereas animals fed 1× spent more time drinking water. Under the conditions of this experiment, we conclude that it was possible to reduce the feeding frequency of TMR, without negative effects on dairy cow performance. However, the use of OA resulted in higher milk yield and mitigated TMR temperature rise regardless of feeding frequency. The effect of external factors such as collective stimulation of intake and stage of lactation on feeding frequency effect must be surveyed in further research.     

Effects of altering total mixed ration conservation method when feeding dry-rolled versus steam-flaked hulled rice on lactation and digestion in dairy cows

We evaluated the effects of different methods of conserving the total mixed ration (TMR) and processing hulled rice (Oryza sativa L.) on intake, digestion, ruminal fermentation, lactation performance, and nitrogen utilization in dairy cows. Eight multiparous Holstein cows (126 ± 19 d in milk) were used in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of dietary treatments. The experimental diets used fresh TMR and ensiled TMR containing either dry-rolled (DR) hulled rice or steam-flaked (SF) hulled rice. The fresh TMR was prepared every morning. The ensiled TMR was prepared by baling fresh TMR and then sealing it with a bale wrapper; this was stored outdoors at 10 to 30°C for >4 mo. The method of grain processing did not affect the dry matter (DM) intake. The DM intake tended to be greater for ensiled TMR than for fresh TMR. Apparent total-tract DM digestibility and milk yield were increased by feeding ensiled TMR instead of fresh TMR and by replacing DR with SF. An interaction effect between the TMR conservation method and the grain processing method was detected for DM digestibility and milk yield; replacing DR with SF increased the DM digestibility and milk yield in cows fed fresh TMR, but this did not affect the cows fed ensiled TMR. The milk fat and lactose contents did not differ among dietary treatments. The milk protein concentration was higher for the cows fed SF processed hulled rice than those fed DR, but it was not influenced by the TMR conservation method. The ruminal total volatile fatty acid concentration was higher for the cows fed ensiled TMR compared with those fed fresh TMR, but it was not affected by the grain processing method. The molar proportion of acetate was decreased and propionate was increased by feeding ensiled TMR instead of fresh TMR and by replacing DR with SF. The concentrations of rumen ammonia N and plasma urea N were higher for the cows fed ensiled TMR than fresh TMR and were lower for SF than DR. Feeding ensiled TMR instead of fresh TMR increased the cows' urinary N excretion and decreased the retention N. Replacing DR with SF decreased the urinary N excretion, increased the milk N secretion, and then improved the nitrogen efficiency. These results show that feeding ensiled TMR instead of fresh TMR has an adverse effect on N utilization, but it increases digestion and milk production. Replacing DR with SF also increases digestion, milk yield, and milk protein content, and the improvement of milk yield by replacing DR with SF was prominent in the cows fed fresh TMR.     

The Effect of Silage and Concentrate Type on Intake Behavior, Rumen Function, and Milk Production in Dairy Cows in Early and Late Lactation

The objective of this experiment was to evaluate the effect of feeding total mixed rations (TMR) that differ in structural and nonstructural carbohydrates to dairy cows in early and late lactation on short-term feed intake, dry matter intake (DMI), rumen fermentation variables, and milk yield. A 5 × 5 Latin square experiment with 15 dairy cows was repeated during early and late lactation. The 5 treatments were a TMR with (all on dry matter basis) 55% roughage (a 50:50 mixture of corn silage and grass silage) and 45% concentrate (a 50:50 mixture of concentrate rich in structural carbohydrates and concentrate rich in nonstructural carbohydrates; treatment CON), a TMR with the concentrate mixture and 55% grass silage (RGS) or 55% corn silage (RCS), and a TMR with the roughage mixture and 45% of the concentrate rich in structural carbohydrates (CSC) or the concentrate rich in nonstructural carbohydrates (CNS). Meal criteria, determined using the Gaussian-Gaussian-Weibull method per animal per treatment, showed an interaction between lactation stage and treatment. Feed intake behavior variables were therefore calculated with meal criteria per treatment-lactation stage combination. Differences in feed intake behavior were more pronounced between treatments differing in roughage composition than between treatments differing in concentrate composition, probably related to larger differences in chemical composition and particle size between corn silage and grass silage than between the 2 concentrates. The number of meals was similar between treatments, but eating time was greater in RGS (227 min/d) and lesser in RCS (177 min/d) than the other treatments. Intake rate increased when the amount of grass silage decreased, whereas meal duration decreased simultaneously. These effects were in line with a decreased DMI of the RGS diet vs. the other treatments, probably related to the high neutral detergent fiber (NDF) content. However, this effect was not found in CSC, although NDF content of the TMR, fractional clearance rate of NDF, and fractional degradation rate of NDF was similar between CSC and RGS. Rumen fluid pH was lesser, and molar proportions of acetic acid and of propionic acid were lesser and greater, respectively, in RCS compared with all other diets. Milk production did not differ between treatments. There was no effect of type of concentrate on milk composition, but diet RCS resulted in a lesser milk fat content and greater milk protein content than diet RGS. Lactation stage did affect short-term feed intake behavior and DMI, although different grass silages were fed during early and late lactation. The results indicate that short-term feed intake behavior is related to DMI and therefore may be a helpful tool in optimizing DMI and milk production in high-production dairy cows.     

The effect of steam-flaked or dry ground corn and supplemental phytic acid on phosphorus partitioning and ruminal phytase activity in lactating cows

The effect of starch source and phytic acid (PA) supplementation on phosphorus (P) partitioning and ruminal phytase activity was evaluated in eight midlactation cows (four ruminally cannulated). Cows were randomly assigned to treatments in replicated 4 x 4 Latin squares with four 18-d periods. Diets included dry ground corn (DG) or steam-flaked corn (SF), with no supplemental P (L; 0.33% P) or supplemental purified PA (0.44% P) to provide additional P from a nonmineral source. Total collection of milk, urine, and feces was conducted on d 16 to 18 of each period. Ruminal fluid was sampled and ruminal pH measured every 8 h on d 17 and 18. Milk yield was unaffected by starch source, despite lower DMI by cows fed SF. Cows fed SF had increased DM digestibility compared with those fed DG, and tended to have higher efficiency of milk yield (1.40 vs. 1.35 kg of milk/kg of DMI). Intake and fecal excretion of P was lower in cows fed SF than in cows fed DG. In cows fed SF, milk P as a percentage of P intake increased compared with cows fed DG. Ruminal pH was unaffected by diet, but milk fat content was lower for cows fed SF. Milk yield, DMI, and feed to milk ratio were not affected by supplementation with PA. Although cows fed PA had increased P intake compared with cows fed low P diet, increased P excretion resulted in no differences in apparent P digestibility. Phosphorus balance tended to be higher in cows fed PA, but milk P as a percentage of intake was reduced. The interaction of starch source and PA affected ruminal phytase activity. Altering starch source to improve efficiency of milk yield in lactating dairy cows may help reduce P losses from dairy farms.     

Effect of strategy for harvesting regrowth grass silage on performance in dairy cows

The objective of this study was to evaluate the effects of feeding lactating dairy cows with regrowth silages from different 2- and 3-cut harvesting systems on milk production, efficiency of N, and energy utilization. Thirty Nordic Red cows were offered 5 experimental diets containing regrowth silages, crimped barley, and canola meal in replicated incomplete 5 × 4 Latin squares with four 21-d periods consisting of 14 d of feed adaptation and 7 d of sampling. Four second-cut silage diets were examined in a 2 × 2 factorial arrangement, enabling evaluation of effect of harvest time of the early or late first cut on second-cut silages, short or long regrowth interval within second cut, and their interaction on dairy cow performance. The third-cut silage diet harvested from early first cut and short regrowth interval of second-cut ley was compared with the second-cut silage diets to evaluate the difference in dairy cow performance between second- and third-cut silages. Postponing the first cut and extending the regrowth interval decreased dry matter intake (DMI), energy-corrected milk (ECM) yield, nutrient digestibility, and urinary energy output, but improved N efficiency (milk N/N intake). Postponing the first cut also decreased the efficiency of metabolizable energy use for lactation, but increased CH₄ yield (CH₄/DMI). Extending the regrowth interval decreased feed efficiency (ECM/DMI) and increased CH₄ intensity (CH₄/ECM). Thus, feeding regrowth silages in 2- or 3-cut systems harvested after an early first cut and short regrowth interval promoted better dairy performance and feed intake, and higher efficiency of feed and energy utilization, but with poorer N efficiency. Feeding third-cut silage improve milk yield and feed efficiency compared with second-cut silages.     

Effect of wet or dry corn gluten feed on nutrient digestibility and milk yield and composition.

A 22-wk trial was conducted to determine variations in nutrient concentrations of wet and dry corn gluten feed and their effect on nutrient digestibility and milk yield and composition. Holstein cows (n = 48) were blocked at parturition by parity and assigned randomly within block to one of three diets. All cows were fed a control TMR containing corn silage, ground corn, and commercial concentrate plus 2.3 kg/d of alfalfa hay during the 2-wk adjustment period. Thereafter, control diet was fed as wet or dry corn gluten feed substituted for 27% of dietary DM supplied by the control diet. Each cow received TMR for ad libitum consumption. Variations in nutrient concentrations of corn gluten feed were observed throughout the trial. The coefficient of variation was highest for ADIN, and standard deviation was highest for NDF. Intake of CP and NDF and apparent digestibility of DM were greatest when wet or dry corn gluten feed was fed. No differences in DMI, milk yield, and percentages of milk protein, lactose, or SNF were observed, but milk fat percentage was lowest when dry corn gluten feed was fed. Results indicate that corn gluten feed can replace 27% of dietary DM without altering milk yield, but new deliveries should be sampled regularly and amounts fed adjusted to compensate for varying nutrient concentrations.     

Milk yield loss in response to feed restriction is associated with mammary epithelial cell exfoliation in dairy cows

In dairy cows, feed restriction is known to decrease milk yield by reducing the number of mammary epithelial cells (MEC) in the udder through a shift in the MEC proliferation–apoptosis balance, by reducing the metabolic activity of MEC, or both. The exfoliation of MEC from the mammary epithelium into milk is another process that may participate in regulating the number of MEC during feed restriction. The aim of the present study was to clarify the mechanisms that underlie the milk yield loss induced by feed restriction. Nineteen Holstein dairy cows producing 40.0 ± 0.7 kg/d at 77 ± 5 d in milk were divided into a control group (n = 9) and a feed-restricted group (n = 10). Ad libitum dry matter intake (DMI) was recorded during a pre-experimental period of 2 wk. For 29 d (period 1), cows were fed either 100 (control) or 80% (feed-restricted) of their ad libitum DMI measured during the pre-experimental period. Then, all cows were fed ad libitum for 35 d (period 2). Milk production and DMI were recorded daily. Blood and milk samples were collected once during the pre-experimental period; on d 5, 9, and 27 of period 1; and on d 5, 9, and 30 of period 2. Mammary epithelial cells were purified from milk using an immunomagnetic method to determine the rate of MEC exfoliation. Mammary tissue samples were collected by biopsy at the end of each period to analyze the rates of cell proliferation and apoptosis and the expression of genes involved in synthesizing constituents of milk. Feed restriction decreased milk yield by 3 kg/d but had no effect on rates of proliferation and apoptosis in the mammary tissue or on the expression of genes involved in milk synthesis. The daily MEC exfoliation rate was 65% greater in feed-restricted cows than in control cows. These effects in feed-restricted cows were associated with reduced insulin-like growth factor-1 and cortisol plasma concentrations. When all cows returned to ad libitum feeding, no significant difference on milk yield or MEC exfoliation rate was observed between feed-restricted and control cows, but refeeding increased prolactin release during milking. These results show that the exfoliation process may play a role in regulating the number of MEC in the udders of dairy cows during feed restriction without any carryover effect on their milk production.     

Effects of mechanical processing on the nutritive value of barley silage for lactating dairy cows

Mechanical processing of whole crop barley before ensiling may be useful for improving nutrient use by dairy cattle. The objective of this study was to assess the effects of feeding mechanically processed barley silage as the main forage source on lactational performance. Twenty-four Holstein cows, 16 primiparous (187 +/- 52 days in milk) and 8 multiparous (87 +/- 69 days in milk) cows, were used in a completely randomized design with a 2-wk covariate period and a 6-wk treatment period. The 2 treatments were: 1) total mixed ration (TMR) containing regular barley silage (RBS-TMR), and 2) TMR containing mechanically processed barley silage (MPBS-TMR). Barley silage and alfalfa hay supplied 41 and 5% of the dietary dry matter (DM), respectively. Intake, body weight, and milk production were measured during the covariate and treatment periods. In addition, 2 multiparous cows were used for in situ measurements of the ruminal DM and fiber degradation kinetics of the barley silages and TMR. Data were analyzed with repeated measurements using a mixed model that included the covariate adjustment. Feeding MPBS-TMR had no significant effects on DM intake (DMI; 21.7 kg/d), milk yield (33.9 kg/d), or milk composition, with only 4% FCM (fat-corrected milk) yield (29.7 vs. 31.7 kg/d) and milk fat concentration (3.30 vs. 3.57%) showing a numerical improvement. Apparent digestibilities of DM and nutrients were not affected by feeding MPBS-TMR, with the exception of starch digestibility, which tended to increase. Dairy efficiencies calculated as milk yield/DMI or FCM/DMI were not different between treatments. Body weight and body condition score were not affected by treatments. Effective ruminal degradability of DM was similar for both barley silages, indicating that when the silages were ground to remove the effects of mechanical processing, the potential digestion was similar. Mechanical processing of barley silage harvested at a mid-dough stage of maturity resulted in small improvements in its nutritive value for lactating dairy cows and had minor impact on digestibility and milk production.     

A 100-Year Review: Total mixed ration feeding of dairy cows

Total mixed rations (TMR) as we know them today did not exist in 1917. In fact, TMR are an invention of primarily the last half of the past 100 yr. Prior to that time many dairy herds were fed only forages, but dairy producers started moving toward TMR feeding as milk production per cow increased, herds became larger, freestall and large-group handling of cows became more common, and milking parlors became more prevalent. The earliest known reports in the Journal of Dairy Science of feeding “complete rations” or TMR may have appeared in the 1950s, but those studies were often reported only as abstracts at annual meetings of the American Dairy Science Association or in extension-type publications. The earliest full-length article on TMR in the journal was published in 1966. An advantage of feeding TMR as opposed to feeding forages supplemented with concentrates is the opportunity to make every bite of feed essentially a complete, nutritionally balanced diet for all cows. Nutritionally related off-feed (e.g., ingredient separation due to poor mixing, feed sorting by the animal, and so on), milk fat depression, and other digestive upsets were less likely to occur with TMR feeding. Feed mixer wagons, feed particle sizes, moisture content of diets, and other factors were not concerns before TMR feeding but are concerns today. Today, most dairy herds, especially larger herds in the United States and elsewhere, feed TMR.     

Productive performance and digestive response of dairy cows fed different diets combining a total mixed ration and fresh forage

The purpose of this experiment was to determine the effects of feeding increasing levels of fresh forage (FF) as a proportion of total dry matter intake (DMI) on nutrient intake, rumen digestion, nutrient utilization, and productive performance of total mixed ration (TMR)-fed cows. Twelve dairy cows (90 ± 22 d in milk, 523 ± 88 kg of body weight, 7,908 ± 719 kg of milk production in the previous lactation) were housed in individual tiestalls and assigned to treatments according to a 3 × 3 Latin square design replicated 4 times. Treatments were 100% TMR (T100), 75% TMR plus 25% FF (T75), and 50% TMR plus 50% FF (T50). The experiment lasted 60 d, divided into 3 periods of 20 d each; the first 12 d of each period were used for diet adaptation and the last 8 d for data collection. The TMR (18.1% crude protein, 24.6% acid detergent fiber) and FF (Lolium multiflorum; 15.1% crude protein, 24.1% acid detergent fiber) were prepared and cut daily and offered to each cow individually. The highest DMI was reached in T100 and T75, which was reflected in greater intake of the different nutrients than T50. No differences were detected in the apparent total digestibility of the nutrients, mean ruminal pH, and total volatile fatty acid concentrations among treatments. Cows in T50 resulted in the lowest ruminal N-NH₃ concentration and the lowest microbial N flow to the duodenum. Milk yield was 8.5% higher from cows in T100 and T75 compared with T50, but we observed no differences for milk fat or milk protein yield among treatments. Milk fat of cows fed T50 had 8% more unsaturated fatty acids (FA) than that of cows fed T100, mostly because of a higher content of monounsaturated FA. Additionally, cows in T50 had a higher concentration of linoleic acid, vaccenic acid, and rumenic acid than T100. Meanwhile, the concentration of linoleic acid and vaccenic acid in cows fed T75 was higher than T100. The milk fat of the cows fed T50 and T75 had a lower n-6:n-3 ratio than T100. We concluded that including up to 29% of FF in the total DMI in combination with a TMR did not affect the intake or digestion of nutrients or the productive response in dairy cows and resulted in a higher concentration of desirable FA from a consumer's perspective.     

Effects of rumen-degradable protein:rumen-undegradable protein ratio and corn processing on production performance,nitrogen efficiency,and feeding behavior of Holstein dairy cows

This study was conducted to investigate the effects of the ratio of rumen-degradable protein (RDP) to rumen-undegradable protein (RUP) and corn processing method on production performance, nitrogen (N) efficiency, and feeding behavior of high-producing Holstein dairy cows. Twelve multiparous Holstein cows (second parity; milk yield = 48 ± 3 kg/d) were assigned to a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments. Factor 1 was corn processing method [ground corn (GC) or steam flaked corn (SFC) with a flake density of about 390 g/L], and factor 2 was RDP:RUP ratio [low ratio (LR) = 60:40; high ratio (HR) = 65:35] based on crude protein (%). The crude protein concentrations were kept constant across the treatments (16.7% of DM). No significant interactions of main treatment effects occurred for lactation performance data. Cows fed 2 different RDP:RUP ratios exhibited similar dry matter intake (DMI), but those fed SFC showed decreased feed intake compared with those receiving GC (25.1 ± 0.48 vs. 26.2 ± 0.47 kg/d, respectively). Cows fed HR diets produced more milk than did those fed LR diets (44.4 ± 1.05 vs. 43.2 ± 1.05 kg/d, respectively). Milk fat content decreased but milk protein content increased in cows fed SFC compared with those fed GC. Feed efficiency (i.e., milk yield/DMI) was enhanced with increasing ratio of RDP:RUP (1.68 ± 0.04 vs. 1.74 ± 0.04 for LR and HR, respectively). Apparent N efficiency was higher in cows fed HR than in those fed LR (30.4 ± 0.61 vs. 29.2 ± 0.62, respectively). Compared with cows fed the GC-based diet, those receiving SFC exhibited lower values of N intake, N-NH₃ concentration, and fecal N excretion. Cows receiving SFC-based diets spent more time ruminating (min/kg of DMI) than did those fed GC. Although these results showed no interaction effects of RDP:RUP ratio and corn processing method on performance, higher RDP:RUP ratios and ground corn can be effective feeding strategies for feed to lactating cows receiving high-concentrate diets.     

Effect of frequency of feed delivery on the behavior and productivity of lactating dairy cows

The objective of this study was to determine the effect of feed delivery frequency on the behavioral patterns and productivity of lactating dairy cows. Twelve freestall-housed, lactating Holstein dairy cows, including 6 primiparous (PP) and 6 multiparous (MP), milked 3×/d (at 1400, 2200, and 0600h), were exposed to each of 3 treatments (over 21-d periods) in a replicated Latin square design. Treatments included feed delivery frequency of (1) 1×/d (at 1400 h), (2) 2×/d (at 1400 and 2200 h), and (3) 3×/d (at 1400, 2200, and 0600 h). Milk production as well as feeding, lying, and rumination behaviors were electronically monitored for each animal for the last 7 d of each treatment period. Milk samples were collected for the last 3 d of each period for milk component analysis. Dry matter intake (DMI) varied with feed delivery frequency, with greatest DMI observed in cows fed 3×/d (27.8 kg/d) compared with those fed 2×/d (27.0 kg/d) or 1×/d (27.4 kg/d). Treatment had no effect on milk yield (41.3 kg/d) or efficiency of production (1.54 kg of milk/kg of DMI). Cows that did not receive delivery of feed following the 2200 h milking (treatment 1) and 0600 h milking (treatments 1 and 2) had lower DMI during the first hour after milking than those that received feed at all milkings (treatment 3). Total feeding time and meal frequency, size, and duration did not vary by treatment, but PP cows consumed smaller meals at a slower rate, resulting in lower DMI compared with MP cows. Primiparous cows consumed 50.1% and 26.1% less dry matter than MP cows during the first meal following the first and second milkings, respectively. Lying time did not vary by treatment, but PP cows spent more time lying (10.3 vs. 8.3 h/d) than MP cows. Under 3×/d milking schedules, greater feed delivery frequency resulted in greater DMI as a function of increased DMI following the return from milking and the delivery of feed.