Effects of substitution of different levels of steam-flaked corn for finely ground corn on lactation and digestion in early lactation dairy cows

Eight multiparous Holstein cows, 4 of them fitted with rumen cannulas, were used to test the effects of substitution of steam-flaked corn (SFC) for equal amounts of finely ground corn (FGC) in diets on feed intake and digestion, blood metabolites, and lactation performance in early lactation dairy cows. Cows were fed 4 diets in a replicated 4 × 4 Latin square design. The fistulated cows formed 1 replicate. Each experimental period lasted for 3 wk. The 4 diets contained 0, 10, 20, or 40% SFC and 40, 30, 20, or 0% FGC (dry matter basis), respectively. The milk protein content and yield, milk solid nonfat content and yield, plasma glucose concentration, and dry matter intake increased as the proportion of SFC increased in diets. Apparent total tract digestibilities of dry matter, organic matter, neutral detergent fiber, acid detergent fiber, and average ruminal fluid NH₃-N concentration decreased with increasing levels of SFC. The ruminal fluid pH was not affected by the substitution of SFC for FGC. The 20% SFC substitution improved digestion of crude protein, yield of fat-corrected milk, milk lactose content, fat, and fat yield. The 40% SFC substitution increased urea concentration in both plasma and milk. It was concluded that 20% of SFC substitution for FGC appeared to be an appropriate level in diet for early lactation dairy cows.     

NutriDense corn grain and corn silage for dairy cows

Twenty multiparous Holstein cows, 4 of them surgically fitted with ruminal cannulas, were used in a replicated 4 × 4 Latin square to compare the effects of whole-plant silage and grain produced from NutriDense (ND), leafy NutriDense (LND), or a conventional yellow dent (YD) hybrid on ruminal fermentation, total tract nutrient digestibility, and performance of lactating dairy cows. On a DM basis, diets contained 30.6% corn silage and 27.7% corn grain provided from the 3 hybrids according to the following combinations: 1) YD grain and YD silage, 2) YD grain and LND silage, 3) ND grain and YD silage, and 4) ND grain and LND silage. The average concentrations of crude protein, neutral and acid detergent fiber, and ether extract of LND silage and ND grain were higher, but the contents of nonfibrous carbohydrates and starch were lower than those of their YD counterparts. Although DM intake was similar among treatments, feeding ND grain, LND silage, or both reduced the intakes of nonfibrous carbohydrates and starch but increased the intake of ether extract. Apparent digestibility of starch in the total tract was highest for the diet that contained LND silage and YD grain, whereas the amount and percentage of ether extract that were apparently digested in the total tract was increased and tended to be increased, respectively, by the addition of ND grain, LND silage, or both to the diets. Ruminal fermentation parameters were unaffected by treatments except for the concentration of ammonia nitrogen in the ruminal fluid, which tended to be increased by the feeding of ND grain, LND silage, or both. Production of milk, crude and true protein, fat, lactose, and total solids did not differ among diets. Concentration of milk urea nitrogen increased when the ND grain, LND silage, or both were fed to the cows. Results indicate that ND grain and LND silage were similar to the conventional grain and silage for the feeding of lactating dairy cows.     

Corn bran versus corn grain at 2 levels of forage: Intake,apparent digestibility,and production responses by lactating dairy cows

The objective of this study was to determine the effect of substituting corn bran (CB) for dried ground corn grain (CG) in the nonforage portion of high-forage (HF) and low-forage (LF) diets. Twelve multiparous and 12 primiparous Holsteins were assigned to 4 diets using six 4 ×  Latin squares with 3-wk periods. Forage was 64 or 38% of the total mixed ration (% of dry matter). On a dry matter basis, the HFCG diet had 20% CG, the LFCG diet had 39% CG, the HFCB diet had 19% CB, and the LFCB diet had 38% CB. Digestible organic matter intake (OMI) and milk energy yield were lower for CB compared with CG within forage level. Digestible OMI was greater (1.9 kg/d) for the LFCG compared with the HFCG treatment. When CB replaced forage (LFCB vs. HFCB), digestible OMI was not different but milk energy yield was greater with the LFCB diet. The LFCG diet supported the greatest milk, milk protein, and milk energy yield. Decreased concentration of milk protein and increased concentration of milk urea nitrogen when feeding CB compared with CG suggests that lack of fermentable energy in the CB diets may have limited rumen microbial protein synthesis. Total substitution of CG with CB in the nonforage portion did not support maximum milk production, even when forage was reduced at the same time (HFCG vs. LFCB). Predicted neutral detergent fiber (NDF) digestibility at 1 times maintenance, based on chemical analysis of the individual feeds, was 22 percentage units greater for CB than for the forage mix (68.9 vs. 46.9%). In vitro NDF digestibility (30 h) was 19.4 percentage units greater for CB than for the forage mix (68.9 vs. 49.5%). However, in vivo NDF digestibility of the diet when CB replaced forage (HFCB vs. LFCB) was similar (44.1 vs. 44.5%). Similarly, predicted total digestible nutrients at the production level of intake, based on chemical analysis, were greater for the CB treatments and lower for the CG treatments than those observed in vivo.     

Performance of dairy cows fed annual ryegrass silage and corn silage with steam-flaked or ground corn

Twenty-four lactating Holstein cows were used in a 6-wk randomized block design trial with a 2 × 2 factorial arrangement of treatments to determine the effects of feeding ground corn (GC) or steam-flaked corn (SFC) in diets based on either annual ryegrass silage (RS) or a 50:50 blend of annual ryegrass and corn silages (BLEND). Experimental diets contained 49.6% forage and were fed as a total mixed ration once daily for 4 wk after a 2-wk preliminary period. No interactions were observed among treatments. Cows fed BLEND consumed more dry matter (DM), organic matter (OM), neutral detergent fiber (NDF), and acid detergent fiber (ADF) than those fed RS, but total-tract digestibility of OM, NDF, and ADF was greater for RS than for BLEND. No differences in nutrient intake were observed among treatments during wk 4 when nutrient digestibility was measured, but digestibility of DM and OM was greater for SFC than for GC. Cows fed BLEND tended to produce more energy-corrected milk than those fed RS, resulting in improved efficiency (kg of milk per kg of DM intake). When diets were supplemented with SFC, cows consumed less DM and produced more milk that tended to have lower milk fat percentage. Yield of milk protein and efficiency was greatest with SFC compared with GC. Blood glucose and milk urea nitrogen concentrations were similar among treatments, but blood urea nitrogen was greater for cows fed GC compared with those fed SFC. Results of this trial indicate that feeding a blend of annual ryegrass and corn silage is more desirable than feeding diets based on RS as the sole forage. Supplementing diets with SFC improved performance and efficiency compared with GC across forage sources.     

Performance of lactating dairy cows fed ryegrass silage and corn silage with ground corn, steam-flaked corn, or hominy feed

Forty-eight mid-lactation Holstein cows were used in a 6-wk completely randomized block design trial with a 4 × 3 factorial arrangement of treatments to determine the effects of feeding different proportions of corn silage and ryegrass silage with supplemental ground corn (GC), steam-flaked corn (SFC), and hominy feed (HF) on the performance of lactating dairy cows. Forage provided 49% of the dietary dry matter in the experimental diets, which were formulated to meet National Research Council requirements. Ryegrass silage provided 100, 75, 50, or 25% of the total forage dry matter, with corn silage supplying the remainder. There were no interactions between the proportion of forage provided by ryegrass silage and energy supplement. Dry matter intake and milk protein percentage decreased linearly with increasing proportions of ryegrass silage, but milk protein yield was similar among forage treatments. There were no differences among forage treatments in milk yield, milk fat percentage and yield, and energy-corrected milk yield. Dry matter intake was higher and there was a tendency for increased milk fat percentage for GC compared with SFC or HF. No other differences were observed in milk yield or composition among energy supplements. Plasma urea nitrogen and glucose concentrations were similar among treatments. Under the conditions of this trial, our results indicate that feeding a combination of corn silage and ryegrass silage is more desirable than feeding ryegrass silage alone, whereas supplementation with GC, SFC, or HF supports similar levels of milk production.     

Chromium supplementation and substitution of barley grain with corn: Effects on performance and lactation in periparturient dairy cows

Thirty-two multiparous Holstein cows were used to investigate the effects of chromium-l-methionine (Cr-Met) supplementation and dietary grain source on performance and lactation during the periparturient period. Cows were fed a total mixed ration consisting of either a barley-based diet (BBD) or a corn-based diet (CBD) from 21 d before anticipated calving through 28 d after calving. The Cr-Met was supplemented at dosages of 0 or 0.08 mg of Cr/kg of metabolic body weight. The study was designed as a randomized complete block design with 2 (Cr-Met levels) × 2 (grain sources) factorial arrangement. There was no Cr effect on prepartum dry matter intake (DMI) or postpartum DMI, body weight (BW), net energy balance, and whole tract apparent digestibility of nutrients. Prepartum DMI as a percentage of BW tended to increase with Cr-Met. Supplemental Cr-Met tended to increase milk yield whereas milk protein percentage decreased. Pre- and postpartum DMI, BW, net energy balance, milk yield, and milk composition were not affected by substituting ground barley with ground corn. The addition of Cr-Met increased prepartum DMI and tended to increase postpartum DMI of the BBD but not the CBD. The change in prepartum DMI was smaller when the BBD was supplemented with Cr-Met but remained unchanged when the CBD was supplemented with Cr-Met. Yields of crude protein and total solids in milk and prepartum digestibility of DM and organic matter tended to increase when Cr-Met was added to the BBD but remained unchanged when added to the CBD. Periparturient cows failed to respond to the grain source of the diet, whereas they showed greater response in milk yield to diets supplemented with Cr-Met. In conclusion, the present results demonstrate that the beneficial effect of Cr-Met supplementation during the periparturient period to improve feed intake may depend on the grain source of the diet.     

Milk production and nutrient digestibility by dairy cows when fed exogenous amylase with coarsely ground dry corn

The digestibility of starch provided by coarsely ground corn is often low, which reduces the digestible energy (DE) concentration of the diet. We hypothesized that adding exogenous amylase to diets based on coarsely ground dent corn would increase dietary DE resulting in greater milk production. Total-tract nutrient digestibility was measured in a partially replicated Latin square experiment (6 cows and 4 periods) with a 2 × 2 factorial arrangement of treatments. Diets had 26 or 31% starch with or without exogenous amylase (amylase was added to the concentrate mixes at the feed mill). In the low and high starch diets, coarsely ground dry corn (mean particle size = 1.42 mm) provided 43 and 62% of total dietary starch (corn silage provided most of the remaining starch). No treatment interactions were observed. High starch diets had greater dry matter (DM), organic matter, and energy digestibility than low starch diets, and diets with amylase had greater neutral detergent fiber digestibility than diets without amylase. Digestibility of starch averaged 88% and was not affected by treatment. A long-term (98-d) lactation study with 48 Holstein cows (74 d in milk) was conducted using 3 of the diets (low starch diets with and without amylase and the high starch diet without amylase). Addition of amylase to a diet with 26% starch did not affect intake, milk yield, milk composition, body weight, or body condition. Cows fed the diet with 31% starch had greater DM and DE intakes; yields of milk, fat, and protein; and feed efficiency than those fed diets with 26% starch. Milk composition was not affected by starch concentration. Adding exogenous amylase to a lower starch diet did not make the diet nutritionally equivalent to a higher starch diet.     

Effects of feeding increasing levels of wet corn gluten feed on production and ruminal fermentation in lactating dairy cows

An experiment was conducted to evaluate the effects of increasing dietary inclusion rates of wet corn gluten feed (WCGF; Sweet Bran; Cargill Inc., Blair, NE) on milk production and rumen parameters. Four primiparous and 4 multiparous ruminally cannulated Holstein cows averaging 90 ± 13 d in milk (mean ± SD) were randomly assigned to 1 of 4 sequences in a replicated 4 × 4 Latin square experiment with 28-d periods. Treatments were diets containing 0, 11, 23, and 34% WCGF on a dry matter basis; alfalfa hay, corn silage, corn grain, soybean meal, expeller soybean meal, and mineral supplements were varied to maintain similar nutrient concentrations across diets. Performance and measures of ruminal fermentation were monitored. Linear and quadratic effects of increasing WCGF inclusion rate were assessed using mixed-model analysis. Increasing dietary WCGF linearly increased dry matter intake (26.7, 25.9, 29.3, and 29.7 kg/d for 0, 11, 23, and 34% WCGF, respectively) and milk production (36.8, 37.0, 40.1, and 38.9 kg/d). Concentrations of milk components did not differ among treatments; however, protein and lactose yields increased linearly and fat yield tended to increase linearly when more WCGF was fed. This led to greater production of energy-corrected milk (38.2, 38.8, 41.7, and 40.4 kg/d) and solids-corrected milk (35.2, 35.7, 38.5, and 37.2 kg/d), but efficiency of production linearly decreased. Increased WCGF in the diet tended to linearly decrease ruminal pH (6.18, 6.12, 6.14, and 5.91), possibly because mean particle size was below typical recommendations for all diets, and diets with greater proportions of WCGF had a smaller mean particle size. Ruminal acetate concentration decreased linearly and propionate increased linearly as WCGF inclusion rate increased. Treatments had a quadratic effect on ammonia concentration, with greater concentrations for the 0 and 34% WCGF diets. In situ digestibility of soybean hulls showed a significant diet-by-time interaction, and increasing dietary levels of WCGF linearly decreased in situ neutral detergent fiber disappearance at 24 h. Change in body condition score increased linearly with increasing WCGF inclusion rate. Results indicate that adding WCGF to dairy rations can increase energy-corrected milk yield, and this increase appears to be driven, at least in part, by an increase in dry matter intake.     

Effect of alfalfa silage storage structure and roasting corn on production and ruminal metabolism of lactating dairy cows

The objective of this study was to determine if feeding roasted corn would improve production and nutrient utilization when supplemented to lactating cows fed 1 of 3 different alfalfa silages (AS). Forty-two lactating Holstein cows (6 fitted with ruminal cannulas) averaging 77 d in milk and 43 kg of milk/d pretrial were assigned to 2 cyclic changeover designs. Treatments were AS ensiled in bag, bunker, or O₂-limiting tower silos and supplemented with ground shelled corn (GSC) or roasted GSC (RGSC). Silages were prepared from second-cutting alfalfa, field-wilted an average of 24 h, and ensiled over 2 d. Production and N utilization were evaluated in 36 cows during four 28-d periods, and ruminal fermentation was evaluated with 6 cows during five 21-d periods. Experimental diets contained 40% AS, 15% corn silage, and 35% of either GSC or RGSC on a dry matter basis. No significant interactions between AS and corn sources were detected for any production trait. Although the chemical composition of the 3 AS was similar, feeding AS from the O₂-limited tower silo elicited positive production responses. Yields of 3.5% fat-corrected milk and fat were increased 1.7 kg/d and 150 g/d, and milk fat content was increased 0.3% when cows were fed diets based on AS from the O₂-limiting silo compared with the other 2 silages. The responses in milk fat were paralleled by an average increase in acid detergent fiber digestibility of 270 g/d for cows fed AS from the O₂-limiting tower silo. However, ruminal concentrations of lipogenic volatile fatty acids were unchanged with AS source. Cows fed RGSC consumed 0.6 kg/d more dry matter and yielded 30 g/d more protein and 50 g/d more lactose than cows fed GSC diets. There was no evidence of increased total tract digestibility of organic matter or starch, or reduced ruminal NH₃ concentration, when feeding RGSC. Free amino acids increased, and isovalerate decreased in rumen fluid from cows fed RGSC diets. However, responses in production with roasted corn were mainly due to increased dry matter intake, which increased the supply of energy and nutrients available for synthesis of milk and milk components.     

Effects of corn silage hybrid and dietary concentration of forage NDF on digestibility and performance by dairy cows

Eight intact multiparous cows and four ruminally and duodenally cannulated primiparous cows were fed four diets in a replicated 4 x 4 Latin square design: 1) 17% forage neutral detergent fiber (NDF) with brown midrib corn silage (BMRCS), 2) 21% forage NDF with BMRCS, 3) 17% forage NDF with conventional corn silage (CCS), and 4) 21% forage NDF with CCS. Diets contained 17.4% crude protein and 38.5% NDF. Each period consisted of 4 wk for intact cows and 2 wk for cannulated cows. For intact cows, DM intake was higher for BMRCS than CCS, and milk urea N was higher for 21 than 17% forage NDF. Milk protein yield tended to be higher and milk urea N lower for cows fed BMRCS than those fed CCS. Milk yield and milk protein percentage were similar among treatments. For the cannulated cows, ruminal mat consistency was similar among treatments. Based on a 72 h in situ incubation, BMRCS was lower in indigestible NDF than CCS. The BMRCS resulted in a higher proportion of ruminal propionate than CCS. Cows fed 21% forage NDF had a higher proportion of acetate and a lower proportion of propionate than cows fed 17% forage NDF. The total tract digestibility of nutrients and efficiency of bacterial N synthesis were similar among treatments, except that BMRCS resulted in lower intestinal fatty acid digestibility than CCS, and 17% forage NDF tended to result in higher total tract fatty acid digestibility than 21% forage NDF. Ruminal NDF digestibility was similar among dietary treatments. The increased milk production observed from feeding BMRCS in some studies may be explained by higher DM intake rather than increased total tract digestibility of the diets.     

Selection of barley grain affects ruminal fermentation, starch digestibility, and productivity of lactating dairy cows

The objective of this study was to evaluate the effects of 2 lots of barley grain cultivars differing in expected ruminal starch degradation on dry matter (DM) intake, ruminal fermentation, ruminal and total tract digestibility, and milk production of dairy cows when provided at 2 concentrations in the diet. Four primiparous ruminally cannulated (123 ± 69 d in milk; mean ± SD) and 4 multiparous ruminally and duodenally cannulated (46 ± 14 d in milk) cows were used in a 4 × 4 Latin Square design with a 2 × 2 factorial arrangement of treatments with 16-d periods. Primiparous and multiparous cows were assigned to different squares. Treatments were 2 dietary starch concentrations (30 vs. 23% of dietary DM) and 2 lots of barley grain cultivars (Xena vs. Dillon) differing in expected ruminal starch degradation. Xena had higher starch concentration (58.7 vs. 50.0%) and greater in vitro 6-h starch digestibility (78.0 vs. 73.5%) compared with Dillon. All experimental diets were formulated to supply 18.3% crude protein and 20.0% forage neutral detergent fiber. Dry matter intake and milk yield were not affected by treatment. Milk fat concentration (3.55 vs. 3.29%) was greater for cows fed Dillon compared with Xena, but was not affected by dietary starch concentration. Ruminal starch digestion was greater for cows fed high-starch diets compared with those fed low-starch diets (4.55 vs. 2.49 kg/d), and tended to be greater for cows fed Xena compared with those fed Dillon (3.85 vs. 3.19 kg/d). Ruminal acetate concentration was lower, and propionate concentration was greater, for cows fed Xena or high-starch diets compared with cows fed Dillon or low-starch diets, respectively. Furthermore, cows fed Xena or high-starch diets had longer duration that ruminal pH was below 5.8 (6.6 vs. 4.0 and 6.4 vs. 4.2 h/d) and greater total tract starch digestibility (94.3 vs. 93.0 and 94.3 vs. 93.0%) compared with cows fed Dillon or low-starch diets, respectively. These results demonstrate that selection of barley grain can affect milk fat production and rumen fermentation to an extent at least as great as changes in dietary starch concentration.     

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.     

Effects of a combination of feed additives on methane production, diet digestibility, and animal performance in lactating dairy cows

Two experiments were conducted to assess the effects of a mixture of dietary additives on enteric methane production, rumen fermentation, diet digestibility, energy balance, and animal performance in lactating dairy cows. Identical diets were fed in both experiments. The mixture of feed additives investigated contained lauric acid, myristic acid, linseed oil, and calcium fumarate. These additives were included at 0.4, 1.2, 1.5, and 0.7% of dietary dry matter, respectively (treatment ADD). Experimental fat sources were exchanged for a rumen inert source of fat in the control diet (treatment CON) to maintain isolipidic rations. Cows (experiment 1, n = 20; experiment 2, n = 12) were fed restricted amounts of feed to avoid confounding effects of dry matter intake on methane production. In experiment 1, methane production and energy balance were studied using open-circuit indirect calorimetry. In experiment 2, 10 rumen-fistulated animals were used to measure rumen fermentation characteristics. In both experiments animal performance was monitored. The inclusion of dietary additives decreased methane emissions (g/d) by 10%. Milk yield and milk fat content tended to be lower for ADD in experiment 1. In experiment 2, milk production was not affected by ADD, but milk fat content was lower. Fat- and protein-corrected milk was lower for ADD in both experiments. Milk urea nitrogen content was lowered by ADD in experiment 1 and tended to be lower in experiment 2. Apparent total tract digestibility of fat, but not that of starch or neutral detergent fiber, was higher for ADD. Energy retention did not differ between treatments. The decrease in methane production (g/d) was not evident when methane emission was expressed per kilogram of milk produced. Feeding ADD resulted in increases of C12:0 and C14:0 and the intermediates of linseed oil biohydrogenation in milk in both experiments. In experiment 2, ADD-fed cows tended to have a decreased number of protozoa in rumen fluid when compared with that in control cows. Total volatile fatty acid concentrations were lower for ADD, whereas molar proportions of propionate increased at the expense of acetate and butyrate.     

Effect of a high-palmitic acid fat supplement on milk production and apparent total-tract digestibility in high- and low-milk yield dairy cows

The effect of a high-palmitic acid fat supplement was tested in 12 high-producing (mean = 42.1 kg/d) and 12 low-producing (mean = 28.9 kg/d) cows arranged in a replicated 3 × 3 Latin square design. Experimental periods were 21 d, with 18 d of diet adaptation and 3 d of sample collection. Treatments were (1) control (no supplemental fat), (2) high-palmitic acid (PA) supplement (84% C16:0), and (3) Ca salts of palm fatty acid (FA) supplement (Ca-FA). The PA supplement had no effect on milk production, but decreased dry matter intake by 7 and 9% relative to the control in high- and low-producing cows, respectively, and increased feed efficiency by 8.5% in high-producing cows compared with the control. Milk fat concentration and yield were not affected by PA relative to the control in high- or low-producing cows, although PA increased the yield of milk 16-C FA by more than 85 g/d relative to the control. The Ca-FA decreased milk fat concentration compared with PA in high-, but not in low-producing cows. In agreement, Ca-FA dramatically increased milk fat concentration of trans-10 C18:1 and trans-10, cis-12 conjugated linoleic acid (>300%) compared with PA in high-producing cows, but not in low-producing cows. No effect of treatment on milk protein concentration or yield was detected. The PA supplement also increased 16-C FA apparent digestibility by over 10% and increased total FA digestibility compared with the control in high- and low-producing cows. During short-term feeding, palmitic acid supplementation did not increase milk or milk fat yield; however, it was efficiently absorbed, increased feed efficiency, and increased milk 16-C FA yield, while minimizing alterations in ruminal biohydrogenation commonly observed for other unsaturated fat supplements. Longer-term experiments will be necessary to determine the effects on energy balance and changes in body reserves.     

Nitrogen supplementation of corn silages. 1. Effects on feed intake and milk production of dairy cows

Feed intake and milk production responses to N supplementation of corn silage-based diets were measured in three 3 x 3 Latin square experiments. In each experiment, 9 Holstein cows received total mixed rations (TMR), based on corn silage. In Exp. 1, midlactation cows were used to study effects of diets with different ratios of effective rumen-degradable protein (ERDP; g) to fermentable metabolizable energy (FME; MJ), providing a large deficiency (RL), a slight deficiency (RM), and a slight excess (RH) in relation to the target level of 11 g of ERDP/MJ of FME, respectively, for lactating cows. Diets were formulated to be isoenergetic, and to satisfy the metabolizable protein requirements. In Exp. 2, early-lactation cows were used to evaluate effects of different proportions of quickly and slowly rumen-degradable protein (RDP), achieved by replacing soybean meal with urea in the concentrates (0, 0.5, and 1% urea). Experiment 3 investigated effects of synchronizing the availability of FME and ERDP in the rumen. Midlactation cows received a diet containing, on a dry matter (DM) basis, 45% corn silage, 5% ryegrass hay, 35% energy-rich concentrate, and 15% protein-rich concentrate (crude protein: 38% of DM; urea: 2% of DM). The protein-rich concentrate was fed either once (D1) or twice (D2) per day before the meal, or included in the TMR (DU). Treatment RL led to lower DM intake and milk yield, but higher milk production efficiency; there were no significant differences between treatments RM and RH. There were no significant treatment effects on DM intake, milk yield, or milk composition in Exp. 2. Manipulating rumen synchrony by altering the timing of feeding affected milk yields, with D1 cows producing significantly less than D2 and DU cows, which were similar. The amount of ERDP in the diet should be matched to the amount of fermentable energy available to maximize intake, milk yields, and the conversion of feed N into milk protein. However, this study showed only small benefits to altering the diurnal pattern of supply of RDP and FME, and only with extreme feeding strategies that would not be used in practice. Urine volume increased in response to increased or unbalanced protein supply. Analysis of the allantoin:creatinine ratio in spot samples of urine was not useful in identifying predicted differences in microbial protein yield from the rumen.     

Whole linted cottonseed as a forage substitute fed with ground or steam-flaked corn: digestibility and performance

Six ruminally and duodenally cannulated Holstein cows were used in a 6 x 6 Latin square design. The objective was to evaluate any potential interactions in site of nutrient digestion when neutral detergent fiber (NDF) from cottonseed was incrementally substituted for forage NDF (FNDF) from alfalfa silage and when starch availability was varied by feeding ground (G) or steam-flaked (SF) corn. Iso-NDF diets were forage control with G corn (21% FNDF), 5% whole cottonseed (WCS) with G or SF corn (18% FNDF), 10% WCS with G or SF corn (15% FNDF), and 15% WCS with G corn (12% FNDF). Ruminal or total tract digestibilities of organic matter (OM) or nonstructural carbohydrate (NSC) were unaffected, but efficiency of microbial protein synthesis decreased as WCS increased. Ruminal NDF digestibility was not affected despite a linear decrease in pH, but postruminal NDF digestibility decreased with increasing WCS. Ruminal digestibilities of OM and NSC were higher for SF than G corn but did not affect efficiency of microbial N synthesis. Dry matter intake increased quadratically with increasing level of WCS but decreased when SF replaced G corn. Milk yield did not differ across treatments. Milk fat percentage was affected quadratically and milk protein increased linearly with increasing WCS. Milk fat percentage decreased but milk protein was not affected when SF replaced G corn. Lack of an interaction between corn source and level of WCS substitution suggests that WCS was equally effective in maintaining ruminal fermentation and digestibility in diets varying in ruminal starch availability.     

The effects of feeding time on milk production,total-tract digestibility,and daily rhythms of feeding behavior and plasma metabolites and hormones in dairy cows

The timing of feed intake entrains circadian rhythms regulated by internal clocks in many mammals. The objective of this study was to determine if the timing of feeding entrains daily rhythms in dairy cows. Nine Holstein cows were used in a replicated 3 × 3 Latin square design with 14-d periods. An automated system recorded the timing of feed intake over the last 7 d of each period. Treatments were feeding 1×/d at 0830 h (AM) or 2030 h (PM) and feeding 2×/d in equal amounts at 0830 and 2030 h. All treatments were fed at 110% of daily intake. Cows were milked 2×/d at 0500 and 1700 h. Milk yield and composition were not changed by treatment. Daily intake did not differ, but twice-daily feeding tended to decrease total-tract digestibility of organic matter and neutral detergent fiber (NDF). A treatment by time of day interaction was observed for feeding behavior. The amount of feed consumed in the first 2 h after feeding was 70% greater for PM compared with AM feeding. A low rate of intake overnight (2400 to 0500 h; 2.2 ± 0.74% daily intake/h, mean ± SD) and a moderate rate of intake in the afternoon (1200 to 1700 h; 4.8 ± 1.1% daily intake/h) was noted for all treatments, although PM slightly reduced the rate during the afternoon period compared with AM. A treatment by time of day interaction was seen for fecal NDF and indigestible NDF (iNDF) concentration, blood urea nitrogen, plasma glucose and insulin concentrations, body temperature, and lying behavior. Specifically, insulin increased and glucose decreased more after evening feeding than after morning feeding. A cosine function within a 24-h period was used to characterize daily rhythms using a random regression. Rate of feed intake during spontaneous feeding, fecal NDF and iNDF concentration, plasma glucose, insulin, NEFA, body temperature, and lying behavior fit a cosine function within a 24-h period that was modified by treatment. In conclusion, feeding time can reset the daily rhythms of feeding and lying behavior, core body temperature, fecal NDF and iNDF concentration, and plasma blood urea nitrogen, glucose, and insulin concentration of dairy cows, but has no effect on daily DMI and milk production.     

Effects of feeding ground or steam-flaked broom sorghum and ground barley on performance of dairy cows in midlactation

Ten Holstein cows in midlactation were used in a 5 x 5 replicated Latin square design with 21-d periods to determine the effects of feeding ground or steam-flaked broom sorghum (Sorghum bicolor) and ground barley (Hordeum vulgare L.) on lactation performance and nutrient digestibility. Diets were fed as total mixed ration and consisted of 46% forage and 54% concentrate (DM basis). Treatment diets included ground barley, ground barley plus ground broom sorghum, ground broom sorghum, ground barley plus steam-flaked broom sorghum, and steam-flaked broom sorghum. Yield of fat-corrected milk was 2.3 kg greater for cows fed diets containing steam-flaked broom sorghum than for cows fed its ground form (24.4 vs 22.1 kg) and was 2.8 kg greater for cows fed diets containing a blend of steam-flaked broom sorghum plus ground barley than for cows fed ground sorghum (24.9 vs 22.1 kg). Yields and percentages of milk fat, protein, SNF, total solids, and apparent digestibility of crude protein were greater for cows fed steam-flaked broom sorghum and ground barley vs. ground broom sorghum. Including steam-flaked rather than ground broom sorghum in diets significantly increased fecal pH (7.10 vs 6.87) and improved efficiency of feed conversion (1.26 vs 1.15). Feeding steam-flaked broom sorghum alone or with ground barley compared with ground sorghum or the blend of ground barley and ground broom sorghum decreased plasma urea nitrogen increased glucose in plasma. Results of this study showed that feeding steam-flaked broom sorghum compared with ground broom sorghum could supply a more efficient source of energy for lactating cows.     

Performance of lactating dairy cows fed corn as whole plant silage and grain produced from a glyphosate-tolerant hybrid (event NK603)

Sixteen multiparous Holstein cows averaging 74 d in milk were used in a replicated 4 x 4 Latin square to compare the effects on animal performance of feeding whole plant silage and grain from a glyphosate-tolerant corn hybrid (event NK603), a nontransgenic control hybrid, and two commercial nontransgenic hybrids (DK647 and RX740). The grain and silage from the four corn hybrids were produced using the same procedures and under similar agronomic conditions at the University of Illinois. On a dry matter (DM) basis, diets contained 30% corn silage and 27.34% corn grain produced either from event NK603, a nontransgenic control, or commercial hybrids. Apart from the DM content of silages, the chemical composition of both grain and silage produced from the four corn hybrids were substantially equivalent. Feeding diets that contained event NK603 and DK647 hybrids tended to decrease DM intake (DMI) compared with the control nontransgenic and RX740. The intakes of crude protein (CP), acid and neutral detergent fiber, and nonfiber carbohydrates were not different for cows fed event NK603 and control diets. The RX740 diet resulted in the highest intakes of fiber and CP, whereas the DK647 diet resulted in the lowest intake of CP. These differences in nutrient intake arose from small variations in both the DMI and the chemical composition of feed ingredients and experimental diets. Production of milk and 3.5% fat-corrected milk; milk fat, CP, and true protein percentage and yield; milk urea N; milk total solids percentage and yield; and somatic cell count were not affected by treatments. These data indicate that the stable insertion of the gene that confers tolerance to glyphosate (event NK603) in the corn line used in this experiment does not affect its chemical composition and nutritional value for lactating dairy cows when compared with conventional corn.     

Milk production of dairy cows fed wet corn gluten feed during the dry period and lactation

An experiment was conducted with 36 primiparous and 40 multiparous Holstein cows to examine the effects of feeding wet corn gluten feed (WCGF) on 305-d milk production, dry matter (DM) intake, body condition score (BCS), and health. The experimental treatments included: 1) control—WCGF not fed (n = 27); 2) WCGF-L—cows received diets containing WCGF (38% DM basis) during lactation (n = 23); and 3) WCGF-DL—cows received diets containing WCGF (38% DM basis) during the dry period and lactation (n = 26). During the dry period, cows consuming WCGF were observed to have a significant gain in BCS (0.07 ± 0.06) compared with a loss in BCS in cows fed the control diet (control = −0.11 ± 0.06 and WCGF-L = −0.04 ± 0.06). During lactation, there were no differences by treatment on BCS. Cows consuming WCGF during lactation consumed more feed compared with the control: 25.4, 23.8, and 21.2 ± 0.76 kg/d for WCGF-L, WCGF-DL, and the control, respectively. Milk production was higher for cows consuming WCGF: 35.0, 34.7, and 31.1 ± 2.1 kg/d for WCGF-L, WCGF-DL, and the control, respectively. No differences were found in either DM intake or actual milk yield between the WCGF-L and WCGF-DL treatments, indicating that prepartum diets did not influence lactational performance. The WCGF diets resulted in significant reductions in the concentration of milk fat (3.94, 3.74, and 4.15 ± 0.08% for WCGF-L, WCGF-DL, and the control, respectively), but because total milk yield was increased, there were no differences in total milk fat yield. In addition, 3.5% of fat-corrected milk tended to be affected by diet: 38.9, 36.3, and 34.7 ± 1.93 kg/d for WCGF-L, WCGF-DL, and the control, respectively. The increasing effect of DM intake and milk yield in cows consuming WCGF resulted in a similar efficiency of 3.5% fat-corrected milk production for all treatments, averaging 1.5 ± 0.09. Total protein yields were significantly higher for cows consuming WCGF diets during lactation: 1.15, 1.10, 1.00 ± 0.06 kg/d for WCGF-L, WCGF-DL, and the control, respectively. These results indicate that diets may be formulated to contain as much as 37.5% WCGF (DM basis).