The objective of this study was to determine growth, feed intake, and feed efficiency of postbred dairy heifers with different genomic residual feed intake (RFI) predicted as a lactating cow when offered diets differing in energy density. Postbred Holstein heifers (n = 128, ages 14-20 mo) were blocked by initial weight (high, medium-high, medium-low, and low) with 32 heifers per block. Each weight block was sorted by RFI (high or low) to obtain 2 pens of heifers with high and low genomically predicted RFI within each block (8 heifers per pen). Low RFI heifers were expected to have greater feed efficiency than high RFI heifers. Dietary treatments consisted of a higher energy control diet based on corn silage and alfalfa haylage [HE; 62.7% total digestible nutrients, 11.8% crude protein, and 45.6% neutral detergent fiber; dry matter (DM) basis], and a lower energy diet diluted with straw (LE; 57.0% total digestible nutrients, 11.7% crude protein, and 50.1% neutral detergent fiber; DM basis). Each pen within a block was randomly allocated a diet treatment to obtain a 2 × 2 factorial arrangement (2 RFI levels and 2 dietary energy levels). Diets were offered in a 120-d trial. Dry matter intake by heifers was affected by diet (11.0 vs. 10.0 kg/d for HE and LE, respectively) but not by RFI or the interaction of RFI and diet. Daily gain was affected by the interaction of RFI and diet, with low RFI heifers gaining more than high RFI heifers when fed LE (0.94 vs. 0.85 kg/d for low and high RFI, respectively), but no difference for RFI groups when fed HE (1.16 vs. 1.19 kg/d for low and high RFI, respectively). Respective feed efficiencies were improved for low RFI compared with high RFI heifers when fed LE (10.6 vs. 11.8 kg of feed DM/kg of gain), but no effect of RFI was found when fed HE (9.4 vs. 9.5 kg of DM/kg of gain for high and low RFI, respectively). No effect of RFI or diet on first-lactation performance through 150 DIM was observed. Based on these results, the feed efficiency of heifers having different genomic RFI may be dependent on diet energy level, whereby low RFI heifers utilized the LE diet more efficiently. The higher fiber straw (LE) diet controlled intake and maintained more desirable heifer weight gains. This suggests that selection for improved RFI in lactating cows may improve feed efficiency in growing heifers when fed to meet growth goals of 0.9 to 1.0 kg of gain/d.

The objective of this study was to determine the growth, feed efficiency, and manure excretion of prebred dairy heifers with differing predicted genomic residual feed intakes (RFI) when offered diets differing in energy density. Prebred Holstein heifers (n = 128, ages 4 to 8 mo) were blocked by weight (low, medium-low, medium-high, or high) with 32 heifers per block. Heifers in each weight block were grouped by RFI and randomly assigned to obtain 2 pens of high (HRFI) and 2 pens of low RFI (LRFI) heifers within each block (8 heifers/pen). Heifers with LRFI were hypothesized to have greater feed efficiency than HRFI heifers. Dietary treatments were a high-energy diet (HE; 66.6% total digestible nutrients, 14.0% crude protein, and 36.3% neutral detergent fiber, dry matter basis) and a low-energy diet (LE; 63.8% total digestible nutrients, 13.5% crude protein, and 41.2% neutral detergent fiber, dry matter basis). Each pen of heifers was randomly assigned to a treatment to obtain a 2 × 2 factorial arrangement (2 RFI levels × 2 diet energy densities). Diets were offered in a 120-d trial. Dry matter intake was not affected by diet, RFI, or their interaction. Average daily gain (ADG) was affected by diet, with heifers fed HE having greater ADG than heifers fed LE. In addition, RFI affected ADG, with LRFI heifers having greater ADG than HRFI heifers, whereas the interaction of RFI and diet was not significant. Feed efficiency was improved for heifers fed the HE diet, but it was not affected by RFI or the interaction of RFI and diet. Overall, feed efficiency of prebred heifers was not dependent on predicted genomic RFI, because the greater ADG of LRFI heifers was accompanied by slightly higher dry matter intake. Feed efficiency of heifers was reduced when heifers were fed the LE diet, but this resulted in more optimal ADG compared with the HE diet fed for ad libitum intake.

Kernel processing increases starch digestibility in whole-plant corn silage (WPCS). Corn silage processing score (CSPS), the percentage of starch passing through a 4.75-mm sieve, is widely used to assess degree of kernel breakage in WPCS. However, the geometric mean particle size (GMPS) of the kernel-fraction that passes through the 4.75-mm sieve has not been well described. Therefore, the objectives of this study were (1) to evaluate particle size distribution and digestibility of kernels cut in varied particle sizes; (2) to propose a method to measure GMPS in WPCS kernels; and (3) to evaluate the relationship between CSPS and GMPS of the kernel fraction in WPCS. Composite samples of unfermented, dried kernels from 110 corn hybrids commonly used for silage production were kept whole (WH) or manually cut in 2, 4, 8, 16, 32 or 64 pieces (2P, 4P, 8P, 16P, 32P, and 64P, respectively). Dry sieving to determine GMPS, surface area, and particle size distribution using 9 sieves with nominal square apertures of 9.50, 6.70, 4.75, 3.35, 2.36, 1.70, 1.18, and 0.59 mm and pan, as well as ruminal in situ dry matter (DM) digestibilities were performed for each kernel particle number treatment. Incubation times were 0, 3, 6, 12, and 24 h. The ruminal in situ DM disappearance of unfermented kernels increased with the reduction in particle size of corn kernels. Kernels kept whole had the lowest ruminal DM disappearance for all time points with maximum DM disappearance of 6.9% at 24 h and the greatest disappearance was observed for 64P, followed by 32P and 16P. Samples of WPCS (n=80) from 3 studies representing varied theoretical length of cut settings and processor types and settings were also evaluated. Each WPCS sample was divided in 2 and then dried at 60 °C for 48 h. The CSPS was determined in duplicate on 1 of the split samples, whereas on the other split sample the kernel and stover fractions were separated using a hydrodynamic separation procedure. After separation, the kernel fraction was redried at 60°C for 48 h in a forced-air oven and dry sieved to determine GMPS and surface area. Linear relationships between CSPS from WPCS (n=80) and kernel fraction GMPS, surface area, and proportion passing through the 4.75-mm screen were poor. Strong quadratic relationships between proportion of kernel fraction passing through the 4.75-mm screen and kernel fraction GMPS and surface area were observed. These findings suggest that hydrodynamic separation and dry sieving of the kernel fraction may provide a better assessment of kernel breakage in WPCS than CSPS.

The objective of this study was to determine growth, feed intake, and feed efficiency of dairy heifers with different genomic residual feed intake (RFI) predicted as a lactating cow and offered diets differing in energy density. Post-bred Holstein heifers (128, ages 14–20 mo), were blocked by initial weight (high, medium-high, medium-low, and low weight) with 32 heifers per block. Each weight block was sorted by RFI (high, low) to obtain 2 pens of high and 2 pens of low predicted RFI for each block (8 heifers per pen). Low RFI heifers were expected to have greater feed efficiency than high RFI heifers. Dietary treatments were (1) a control diet with corn silage and alfalfa haylage (CON; 62.7% TDN, 11.8% CP, and 45.6% NDF, DM basis), and (2) a similar diet diluted with straw to reduce energy density (STR; 55.9% TDN, 11.7% CP, and 50.1% NDF, DM basis). Each treatment was randomly allocated to blocks to obtain a 2x2 factorial treatment arrangement of 2 RFI levels and 2 dietary energy levels. Diets were offered in a 120-d trial. Statistical analyses were performed using a MIXED procedure in SAS 9.3 with pen as experimental unit. Dry matter intake was affected by diet (11.0 vs. 10.0 kg/d for CON and STR, respectively; P < 0.01) but not RFI or the interaction of main effects (P > 0.10). Average daily gain was affected by the interaction of RFI and diet with low RFI heifers having higher gains than high RFI when fed STR (0.94 vs. 0.84 kg/d for low and high RFI, respectively, P = 0.02), but no difference for RFI groups when fed CON (P = 0.25). Feed efficiency was better for low RFI than high RFI heifers when fed STR (10.6 vs. 11.8 kg feed/kg gain for high and low RFI, respectively; P < 0.01), but no effect of RFI found when fed CON (P > 0.10). Body condition score increased when fed CON (3.8 vs. 3.5 for CON and STR, respectively; P = 0.02). Diet digestibility was greater for CON (58.4 vs. 50.8% DM digestibility for CON and STR, respectively; P = 0.01), which likely caused greater intake and gains for heifers fed CON. Based on these results, feed efficiency of heifers having different RFI is dependent on diet energy level with heifers having low RFI using the moderate energy (STR) diet more efficiently. The straw diet reduced intake and also maintained more desirable heifer weight gains.

Gravid heifers consuming high-quality forage diets are susceptible to excessive weight gains and overconditioning. One approach for controlling this problem is to dilute diets with low-energy forages, such as straw, that reduce the caloric density and dry matter intake (DMI) of that diet by heifers. These diluting agents are often sortable by dairy heifers, but previous visual evidence has suggested that eastern gamagrass haylage may be a nonsortable alternative. Our objectives were (1) to compare the growth performance of dairy heifers offered a high-quality forage diet (control) with diets containing 1 of 3 diluting agents [eastern gamagrass haylage (EGH), chopped wheat straw (WS), or chopped corn fodder (CF)]; and (2) evaluate sorting behaviors of heifers offered these forage diets. Holstein heifers (n=128) were stratified (32 heifers/block) on the basis of initial body weight (heavy, 560 ± 27.7 kg; medium-heavy, 481 ± 17.7 kg; medium-light, 441 ± 22.0 kg; and light, 399 ± 14.4 kg), and then assigned to 1 of 16 identical research pens (4 pens/block; 8 heifers/pen), where each of the 4 research diets were assigned to 1 pen within each block. Diets were offered in a 118-d feeding trial with heifers crowded to 133% of capacity at the feed bunk. Inclusion of low-energy forages was effective in reducing both diet energy density and DMI. Concentrations of physically effective fiber (pef) particles did not change during the 24-h period following feeding for either the control or EGH diets; however, this response for pef particles masked the competing (and cancelling) responses for individual large and medium particles, which heifers sorted with discrimination and preference, respectively. Sorting against pef particles was detected for WS, and much more severely for the CF diet. Sorting of forage particles by heifers could not be related to heifer performance. Compared with control (1.16 kg/d), average daily gains (ADG) were reduced by dilution in all cases, but were virtually identical between EGH (0.98 kg/d) and CF (0.97 kg/d), which exhibited no sorting and extensive sorting of pef, respectively. Furthermore, ADG for WS was approximately 0.2 kg/d less than EGH or CF, despite exhibiting sorting characteristics intermediate between EGH and CF. Diets diluted with low-energy forages were formulated to be isonitrogenous and isocaloric; within that context, WS was most effective in reducing DMI and maintaining ADG within typical recommendations for Holstein heifers.

To test whether total-tract starch digestibility by lactating dairy cattle could be predicted accurately from concentration of starch in fecal dry matter (FS), data from 8 digestibility trials, 30 diets, and 564 individual starch measurements were compiled from trials conducted at the University of Wisconsin-Madison. Total-tract starch digestibility by individual cows was determined from the concentrations of starch in total mixed rations and feces (rectal grab samples) and concentrations of several external or intrinsic feed markers. Fecal starch concentration was closely and linearly related to total-tract starch digestibility (R(2) = 0.94). Differences in fecal sampling time for FS, such as day within week or week, did not influence determination of FS concentration. In contrast, time of day when fecal samples were taken influenced FS concentration, but the differences were minimal (mean ± standard error of the mean = 0.4 ± 0.1). These data suggest that on-farm collection of feces from individual cows or pens of cows may be sampled only once per day. Fecal pH was not related to FS when FS was only 1 to 3%, indicating that fecal pH was not a good index of FS and not practical as a tool to assess total-tract starch digestibility for lactating dairy cows when fecal starch excretion is low. An equation was developed to predict FS using near-infrared reflectance spectroscopy of dried ground fecal samples; the equation had moderate to good accuracy (R(2) = 0.83-0.94) and a low standard error of prediction. Fecal starch concentration can be used to monitor total-tract starch digestibility.

Our objective was to assess the pasture productivity and forage characteristics of 2 fall-grown oat (Avena sativa L.) cultivars, specifically for extending the grazing season and reducing reliance on harvested forages by replacement dairy heifers. A total of 160 gravid Holstein heifers (80 heifers/yr) were stratified by weight, and assigned to 1 of 10 identical research pens (8 heifers/pen). Initial body weights were 480 ± 43.5 kg in 2011 and 509 ± 39.4 kg in 2012. During both years of the trial, four 1.0-ha pasture replicates were seeded in August with Ogle oat (Schumitsch Seed Inc., Antigo, WI), and 4 separate, but similarly configured, pasture replicates were seeded with Forage Plus oat (Kratz Farms, Slinger, WI). Heifer groups were maintained as units, assigned to specific pastures, and then allowed to graze fall-oat pastures for 6h daily before returning to the barn, where they were offered a forage-based basal total mixed ration. Two heifer groups were retained in confinement (without grazing) as controls and offered the identical total mixed ration as pasture groups. During 2011, available forage mass increased with strong linear and quadratic effects for both cultivars, peaking at almost 9 Mg/ha on October 31. In contrast, forage mass was not affected by evaluation date in 2012, remaining ≤ 2,639 kg/ha across all dates because of droughty climatic conditions. During 2012, Ogle exhibited greater forage mass than Forage Plus across all sampling dates (2,678 vs. 1,856 kg/ha), largely because of its more rapid maturation rate and greater canopy height. Estimates of energy density for oat forage ranged from 59.6 to 69.1% during 2011, and ranged narrowly from 68.4 to 70.4% during 2012. For 2011, responses for both cultivars had strong quadratic character, in which the most energy-dense forages occurred in mid November, largely due to accumulation of water-soluble carbohydrates that reached maximum concentrations of 18.2 and 15.1% for Forage Plus and Ogle, respectively. Across the 2-yr trial, average daily gain for grazing heifer groups tended to be greater than heifers remaining in confinement (0.85 vs. 0.74 kg/d), but both management strategies produced weight gains within reasonable proximity to normal targets for heifers in this weight range. Fall-grown oat should be managed as stockpiled forage for deferred grazing, and good utilization of fall-oat forage can be accomplished by a one-time removal of standing forage, facilitated by a single lead wire advanced daily to prevent waste.

The objectives of the study were (1) to determine relationships between high-moisture corn (HMC) dry matter (DM), ammonia-N [% of crude protein (CP)], and soluble CP concentrations, and pH, with 7-h ruminal in vitro starch digestibility (ivStarchD), and (2) to evaluate the effect of ensiling on pH, ammonia-N, soluble CP, and ivStarchD measurements in HMC. A data set comprising 6,131 HMC samples (55 to 80% DM) obtained from a commercial feed analysis laboratory was used for this study. Month of sample submittal was assumed to be associated with length of the ensiling period. Data for month of sample submittal were analyzed using Proc Mixed in SAS (SAS Institute Inc., Cary, NC) with month as a fixed effect. Regressions to determine linear and quadratic relationships between ivStarchD and ammonia-N, soluble CP, pH, and DM content were performed using Proc Mixed. The ivStarchD increased by 9 percentage units from October to August of the following year. Similar results were observed for ammonia-N and soluble CP with increases from 1.8 to 4.6% of CP and 31.3 to 46.4% of CP, respectively, from October to August of the following year. Ammonia-N was positively related to ivStarchD (R(2)=0.61). The DM content of HMC at silo removal was negatively related (R(2)=0.47) to ivStarchD with a decrease of 1.6 percentage units in ivStarchD per 1-percentage-unit increase in DM content. The pH of HMC was negatively related to ammonia-N (R(2)=0.53), soluble CP (R(2)=0.57), and ivStarchD (R(2)=0.51). Combined, ammonia-N, DM, soluble CP, and pH provided a good prediction of ivStarchD (adjusted R(2)=0.70). Increasing pH, ammonia-N, soluble CP, and ivStarchD values indicate that HMC may need up to 10 mo of ensiling to reach maximum starch digestibility. Ammonia-N, DM content, soluble CP concentration, and pH are good indicators of ruminal in vitro starch digestibility for high-moisture corn.

Numerous studies have evaluated laboratory methods to quantify prolamin proteins in dry corn; however, the utility of methods to quantify functional prolamins, which impede starch digestibility, in high-moisture corn (HMC) is less defined. As a result, a common rapid turbidimetric (rTM) laboratory procedure was modified (rapid Bradford method, rBM), extracting buffer-soluble proteins before prolamin solubilization in an effort to better quantify functional prolamins in HMC. Twenty samples of dry and HMC were evaluated by rTM and rBM procedures. Prolamin concentration in dry corn, as estimated by rTM or rBM methods, ranged from 6.12 to 2.20g/100 g of DM or 5.46 to 2.41g/100 g of DM, respectively. Dry corn mean prolamin concentrations, as estimated by rTM or rBM methods, were similar at 3.65 or 3.66g/100 g of DM. Prolamin concentration in HMC, as estimated by rTM, ranged from 4.99 to 3.24g/100 g of DM, with a mean prolamin concentration of 4.19g/100 g of DM, but estimation of prolamins in HMC by the rBM method resulted in lower mean (4.19 vs. 3.24g/100 g of DM) prolamin concentration. Prolamin concentration in dry and HMC measured by rTM was negatively related to peak absolute rates (PAR; mL/0.1 g of DM) of in vitro gas production. However, relationships between rTM prolamin concentration and PAR were not homogeneous and were different between dry and HMC. Prolamin proteins as determined by rBM were likewise negatively related to PAR, but corn type did not influence rBM prolamin concentration by PAR relationships. Data suggest that the rBM method defined more similar functional prolamin proteins, which impede starch degradability, in dry and HMC.

Our objectives were to describe and test refined procedures for quantifying excreta produced from whole pens of dairy heifers. Previous research efforts attempting to make whole-pen measurements of excreta output have been complicated by the use of organic bedding, which requires cumbersome analytical techniques to quantify excreta apart from the bedding. Research pens equipped with sand-bedded freestalls offer a unique opportunity for refinement of whole-pen fecal collection methods, primarily because sand-bedded freestall systems contain no organic bedding; therefore, concentrations of ash within the manure, sand, and feces can be used to correct for contamination of manure by sand bedding. This study was conducted on a subset of heifers from a larger production-scale feeding trial evaluating ensiled eastern gamagrass [Tripsacum dactyloides (L.) L.] haylage (EGG) that was incorporated into a corn silage/alfalfa haylage-based blended diet at rates of 0, 9.1, 18.3, or 27.4% of total DM. The diet without EGG also was offered on a limit-fed basis. Eighty Holstein dairy heifers were blocked (heavy weight, 424 ± 15.9 kg; light weight, 324 ± 22.4 kg) and then assigned to 10 individual pens containing 8 heifers/pen. One pen per block was assigned to each of the 5 research diets, and whole-pen fecal collections were conducted twice for each pen. Grab fecal samples also were gathered from individual heifers within each pen, and subsequent analysis of these whole-pen composites allowed reasonable estimates of OM and NDF excreta output. Under the conditions of our experimental design, pooled SEM for the excreta DM, OM, NDF, and NDF (ash corrected) output were 0.113, 0.085, 0.093, and 0.075 kg·heifer(-1)·d(-1), respectively. For DM excretion, this represented about one-third of the SEM reported for previous whole-pen collections from bedded-pack housing systems. Subsequent calculations of apparent DM and OM digestibilities indicated that the technique was sensitive, and linear trends (P ≤ 0.027) associated with the inclusion rates of EGG within the diet were detected. This technique allows estimation of apparent diet digestibilities on multiple animals simultaneously, thereby mitigating the need for isolating individual animals to obtain digestibility coefficients. The approach appears viable but requires hand labor for collections of multiple pens and thorough mixing of large volumes of manure as well as analytical corrections for sand ingested by lounging heifers.

Sixty samples of 'ForagePlus' oat were selected from a previous plot study for analysis of in vitro gas production (IVGP) on the basis of 2 factors: (1) high (n=29) or low (n=31) neutral detergent fiber (NDF; 62.7±2.61 and 45.1±3.91%, respectively); and (2) the range of water-soluble carbohydrates (WSC) within the high- and low-NDF groups. For the WSC selection factor, concentrations ranged from 4.7 to 13.4% (mean=7.9±2.06%) and from 3.5 to 19.4% (mean=9.7±4.57%) within high- and low-NDF forages, respectively. Our objectives were to assess the relationships between IVGP and various agronomic or nutritional characteristics for high- and low-NDF fall-oat forages. Cumulative IVGP was fitted to a single-pool nonlinear regression model: Y=MAX × (1 - e ([-)(K)(× (t - lag)])), where Y=cumulative gas produced (mL), MAX=maximum cumulative gas produced with infinite incubation time (mL), K=rate constant, t=incubation time (h), and lag=discrete lag time (h). Generally, cumulative IVGP after 12, 24, 36, or 48h within high-NDF fall-oat forages was negatively correlated with NDF, hemicellulose, lignin, and ash, but positively correlated with WSC, nonfiber carbohydrate (NFC), and total digestible nutrients (TDN). For low-NDF fall-grown oat forages, IVGP was positively correlated with growth stage, canopy height, WSC, NFC, and TDN; negative correlations were observed with ash and crude protein (CP) but not generally with fiber components. These responses were also reflected in multiple regression analysis for high- and low-NDF forages. After 12, 24, or 36h of incubation, cumulative IVGP within high-NDF fall-oat forages was explained by complex regression equations utilizing (lignin:NDF)(2), lignin:NDF, hemicellulose, lignin, and TDN(2) as independent variables (R(2)≥0.43). Within low-NDF fall-grown oat forages, cumulative IVGP at these incubation intervals was explained by positive linear relationships with NFC that also exhibited high coefficients of determination (R(2)≥0.75). Gas production was accelerated at early incubation times within low-NDF forages, specifically in response to large pools of WSC that were most likely to be present as forages approached boot stage by late-fall.

A 3-yr study evaluated the carryover effects of dairy heifer grazing experience on behavior and first-lactation performance as dairy cows. Forty-one Holstein and 23 Holstein-Jersey crossbred calves born between January and April 2008 were randomly assigned to 1 of 4 treatments (n = 8 per group, 2 groups per treatment) in a completely randomized design. Treatments were combi-nations of managing dairy heifers in confinement (CNF) or on pasture (PST): grazed yr 1 and 2 (PSTPST); grazed yr 1, but confined yr 2 (PSTCNF); confined yr 1 and grazed yr 2 (CNFPST); or confined yr 1 and 2 (CNFCNF). After calving, all heifers on all treatments were grazed as cows in yr 3. In yr 1, PSTPST and PSTCNF heifers were grazed for 41 d on Italian ryegrass pastures, whereas CNFPST and CNFCNF were housed in bedded-pack pens and fed a TMR. In yr 2, PSTPST and CNFPST heifers grazed Italian ryegrass pasture for 65 d, whereas PSTCNF and CNFCNF remained in confinement. In yr 2, a mid-trial assessment of heifer grazing behavior was made on PSTPST versus CNFPST heifers. Grazing activities were assessed by visual observation and heifer movement measured by portable global positioning system units. Heifers from all treatment groups subsequently calved between January and April in yr 3. All primiparous cows were then allocated to pastures by treatment group, grazed for 61 d, (May through July) in yr 3, with grazing behavior and milk production evaluated while grazing. In yr 2, heifers on the PSTPST treatment spent more time grazing than heifers on the CNFPST treatment (78 vs. 35% of the time) when first exposed to pasture (d 1). On d 1 to 3, PSTPST heifers walked a greater distance than CNFPST heifers; however, PSTPST and CNFPST heifers had similar daily grazing times and walking patterns after 3 d of pasture exposure in yr 2. As lactating cows (yr 3), cows with no (CNFCNF) grazing experience grazed less on d 1 compared with cows with (PSTPST, PSTCNF, or CNFPST) grazing experience. Day-1 grazing times in yr 3 were 62, 59, 76, and 13% of the times for cows with PSTPST, PSTCNF, CNFPST, and CNFCNF grazing experience, respectively. In yr 3, on d 1 to 3, cows with previous grazing experience as heifers (PSTPST, CNFPST, and PSTCNF) walked a greater distance than cows without previous grazing experience (CNFCNF). Milk production was lowest on d 1 to 3 for cows with no previous grazing experience (CNFCNF), but average daily milk production was not different overall over the 61 d of study in yr 3. Results indicate that grazing experiences as a heifer can affect behavior and milk production during a cow’s first days on pasture. After a short acclimation period, dairy cows without grazing experience as heifers developed similar grazing behaviors and performance as cows with grazing experience as heifers.

Data from 69,145 Holstein cows that calved in 2005 were evaluated to determine the influence of age at first calving (AFC) on first lactation and lifetime production in commercial dairy herds. A DHI database was divided into 4 herd management criteria (HMC). The 4 HMC were 1) 3X milking and rolling herd average (RHA) = 12,750 kg (3X-H), 2) 3X milking and RHA = 11,250 kg (3X-M), 3) 2X milking and RHA = 11,250 kg (2X-M), and 4) 2X milking and RHA = 9,250 kg (2X-L). For all HMC, a universal loss in first-lactation milk, fat, and protein yield was observed when AFC was <23 mo. Compared with 24 mo, first-lactation milk yield was decreased, 166, 369, and 654 kg for heifers calving at 22, 21, and 20 mo, respectively. In contrast, AFC × HMC interactions were observed for all herd-life and lifetime production criteria. In 3X-H and 3X-M herds, herd-life and lifetime DIM increased with decreasing AFC. In 2X-M and 2X-L herds, herd-life and lifetime DIM increased when AFC was reduced from 30 to 24 mo, but herd-life and lifetime DIM were not increased when heifers calved <24 mo. In 2X-M and 2X-L herds, the combined effect of reduced first-lactation milk yield and with no corresponding benefit in lifetime DIM resulted in reduced lifetime milk, fat, and protein yields when AFC was <23 mo. In contrast, increased lifetime milk, fat, and protein yields were observed in 3X-H and 3X-M herds when AFC was <23 mo. Data suggest HMC alters the relationship between AFC and lifetime milk, fat, and protein production in commercial dairy herds.

Previous research has shown that eastern gamagrass (EGG; Tripsacum dactyloides L.) will survive winter climatic conditions common throughout central Wisconsin, and will produce yields of dry matter (DM) ranging approximately from 7,000 to 10,000 kg/ha annually when managed with a 1-cut harvest system. The objective of this research was to determine whether the fibrous nature of this perennial warm-season grass could be effective in reducing the caloric density and DMI of corn silage/alfalfa haylage diets for replacement dairy heifers. A total of 120 Holstein dairy heifers were blocked by body weight (heavy, 424 ± 15.9 kg; medium, 369 ± 11.8 kg; light, 324 ± 22.4 kg), and then assigned to 15 individual pens containing 8heifers each. Eastern gamagrass forage was harvested, ensiled, and subsequently incorporated into blended corn silage/alfalfa haylage diets at rates of 0, 9.1, 18.3, or 27.4% of the total dietary DM (EGG0, EGG9, EGG18, and EGG27, respectively). These diets were offered during a 105-d evaluation period for ad libitum intake; however, the EGG0 diet also was offered on a limit-fed basis (LF), which was set at 85% of the voluntary intake of EGG0. Serial additions of EGG increased concentrations of neutral detergent fiber in blended diets from 39.6 (EGG0) to 48.7% (EGG27), and simultaneously reduced corresponding estimates of total digestible nutrients (TDN) from 68.2 to 61.3%, and net energy for gain from 1.07 to 0.83 Mcal/kg. Dry matter intakes for all diets offered ad libitum were greater than observed for LF (9.06 vs. 8.07 kg/d); however, DM intakes for diets containing EGG were reduced relative to EGG0 (9.40 vs. 8.94 kg/d). Similarly, intakes of TDN were greater for diets offered for ad libitum intake than for LF (5.84 vs. 5.50 kg/d); however, inclusion of EGG reduced TDN intakes relative to EGG0 (6.41 vs. 5.65 kg/d). This reduction was explained by both linear and quadratic effects of the inclusion rate of EGG in the diet. Over the 105-d trial, total weight gains ranged from 89 kg (0.85 kg/d) for heifers offered EGG27 up to 114 kg (1.09 kg/d) for those offered EGG0. Performance was similar between heifers offered EGG27 and LF diets (0.85 vs. 0.88 kg/d). Eastern gamagrass haylage proved to be a completely nonsortable additive within corn silage/alfalfa haylage diets. It also was effective in limiting the caloric density and DM intake of these diets, as well as undesirable weight gains by dairy heifers.

The objective of this study was to investigate whether prediction of fermentation potential (FP) of dry and high-moisture (HM) corns could be improved by using a concept of effective (e) mean particle size (MPS). A set of FP standards was created by processing a single lot of Reid Yellow Dent (RYD) corn to achieve MPS of 3,778, 2,786, 2,282, 1,808, 1,410, 806, 586, 378, 308, 226, and 105 μm. In vitro gas production of RYD standards was measured, and peak absolute rate (PAR) of gas production (mL/0.2 g of DM/h) was used to establish a standard relationship between PAR and MPS. To identify factors other than MPS affecting FP, the MPS and nutrient composition of 36 diverse samples of dry (n=18) and HM (n=18) corns were determined. Composition included dry matter (DM), crude protein, soluble crude protein, neutral detergent fiber, starch, NH₃-N, prolamin protein, and fat. In vitro gas production of undried, unground dry and HM corns was measured, and PAR, time of peak absolute rate (h), maximum cumulative gas production (mL/0.2 g of DM), gas production fractional rate (h⁻¹), and lag (h) were determined. Nonlinear relationships between MPS, defined as the dependent variable, and PAR, as an independent variable, were used to identify FP deviations unexplained by MPS. When no variation in nutritional composition was present (RYD standards), the relationship between PAR and MPS was described by an exponential decay model [RYD_MPS=9,006 × e((-0.452 × PAR)); R²=0.96]. For diverse dry and HM corn populations, the variation in MPS explained by PAR was diminished (R²=0.50). To investigate factors that diminish the relationship between MPS and PAR in diverse corns, relative residual (rr) MPS was determined [rrMPS = (MPS - RYD_MPS)/MPS], where RYD_MPS was predicted from the PAR of diverse dry and HM corn. The rrMPS was most highly related to prolamin protein [rrMPS(dry)=0.58-0.15 × (prolamin protein, % of DM); R²=0.43] and NH₃-N [rrMPS(HM)=0.21+0.08 × (NH₃-N, % of total N); R²=0.46] for dry and HM corns, respectively. An eMPS was calculated as eMPS = MPS - MPS × rrMPS, where rrMPS was predicted from prolamin protein or NH₃-N concentration in dry and HM corn, respectively. The natural logarithm of eMPS accounted for 84% of the variability in PAR and 53% of the variability in the fractional rate of gas production. Calculating eMPS by adjusting the MPS of dry corn for prolamin and HM corn for NH₃-N concentration improved the assessment of industry corn FP.

The objective of this study was to quantify the gains in genetic potential of replacement females that could be achieved by using genomic testing to facilitate selection and culling decisions on commercial dairy farms. Data were simulated for 100 commercial dairy herds, each with 1,850 cows, heifers, and calves. Parameters of the simulation were based on the US Holstein population, and assumed reliabilities of traditional and genomic predictions matched reliabilities of animals that have been genotyped to date. Selection of the top 10, 20, 30, …, 90% of animals within each age group was based on parent averages and predicted transmitting abilities with or without genomic testing of all animals or subsets of animals that had been presorted by traditional predictions. Average gains in lifetime net merit breeding value of selected females due to genomic testing, minus prorated costs of genotyping the animals and their unselected contemporaries, ranged from $28 (top 90% selected) to $259 (top 20% selected) for heifer calves with no pedigrees, $14 (top 90% selected) to $121 (top 10% selected) for heifer calves with known sires, and $7 (top 90% selected) to $87 (top 20% selected) for heifer calves with full pedigrees. In most cases, gains in genetic merit of selected heifer calves far exceeded prorated genotyping costs, and gains were greater for animals with missing or incomplete pedigree information. Gains in genetic merit due to genomic testing were smaller for lactating cows that had phenotypic records, and in many cases, these gains barely exceeded or failed to exceed genotyping costs. Strategies based on selective genotyping of the top, middle, or bottom 50% of animals after presorting by traditional parent averages or predicted transmitting abilities were cost effective, particularly when pedigrees or phenotypes were available and a relatively small proportion of animals were to be selected or culled. Based on these results, it appears that routine genotyping of heifer calves or yearling heifers can be a cost-effective strategy for enhancing the genetic level of replacement females on commercial dairy farms. Increasing the accuracy of predicted breeding values for young females with genomic testing might lead to synergies with other management tools and strategies, such as propagating genetically superior females using advanced reproductive technologies or selling excess females that were generated by the use of sex-enhanced semen.

The fates of hydrophobic zein proteins, which encapsulate corn starch to create vitreous endosperm, have not been investigated in high-moisture corn (HMC). To assess influences of ensiling time and inoculation on zein proteins in HMC, quadruplicate samples of 2 random corn hybrids (A and B), containing 25.7 and 29.3% moisture, were ground, inoculated with (I) or without 600,000 cfu/g of Lactobacillus buchneri 40788 (Lallemand Animal Nutrition, Milwaukee, WI), and ensiled for 0, 15, 30, 60, 120, and 240 d. Nutrient composition [crude protein (CP), starch, acid detergent fiber, and neutral detergent fiber], fermentation (pH, lactate, and acetate), and protein degradation markers (buffer-soluble CP, isopropanol-soluble CP, and NH3-N) were evaluated. At 0 and 240 d, α, γ, δ, and β zein subunits were profiled using HPLC. Data were evaluated as a split-split plot using the PROC MIXED procedures of SAS. Ensiling time and inoculation decreased pH, and altered lactate and acetate contents of HMC. Lactate and acetate contents of A, AI, B, and BI at 240 d were 0.40, 0.32, 1.11, 0.73, and 0, 0.35, 0.30, and 0.87% of DM, respectively. Buffer-soluble CP in HMC increased from 1.5 to 2.0% of DM at 0 d to >4.0% of DM at 240 d. Inoculation had no effect on buffer-soluble CP but increased NH3-N content of HMC. Corn A contained more isopropanol-soluble CP than did corn B and peak areas for 6 α, and all γ and δ zein regions were greater for corn A. Ensiling (0 vs. 240 d) decreased all zein subunits with the exception of 2 α and 1 δ subunit. Ensiling decreased (42.2–73.2%) γ zeins, which are primarily responsible for cross-linking in the starch-protein matrix. Despite altering lactate and acetate contents, inoculation had no effect on degrading hydrophobic zein proteins in HMC. Data suggest that hydrophobic zein proteins in the starch-protein matrix of HMC are degraded by proteolytic activity over an extended ensiling time.

The phosphorus requirements for dairy heifers (0.20–0.35%) and endogenous concentrations (0.20–35%) of P in feeds fed to dairy heifers are similar, suggesting that the need for supplemental P in dairy heifer diets may be minimal. Because long-term P feeding studies on dairy heifers are unavailable, 183 Holstein heifers and 182 backcross Holstein × Jersey heifers were offered diets with (SP=0.40% of dry matter) and without (NP=0.30% of dry matter) supplemental P from 4 to 22 mo of age in a replicated pen design. Forty-eight pens of 8 heifers each were split evenly by breed and treatment group. Heifers were evaluated for body weight (BW), external bone/frame growth, dystocia, calf BW, reproductive efficiency, and first-lactation performance. Growth phase data were analyzed using pen-based statistical models, and lactation data were analyzed using mixed linear models with effects of season of birth, age of dam, heifer pen, sire, sire birth year, and days in milk. Heifers fed NP had similar average daily gain from 170 to 410 and from 410 to 650 d of age compared with heifers fed SP. At 22 mo of age, heifers fed NP did not differ in BW, hip height, hip width, body length, heart girth, cannon bone circumference, or pelvic area compared with heifers fed SP. Blood P concentrations between heifers fed SP or NP did not differ at 8 or 18 mo of age, and heifers fed SP excreted more P (29.2 vs. 24.2g/d) than heifers fed NP. As heifers, services per conception and age at pregnancy were not different between heifers fed NP or SP. At parturition, heifers fed NP or SP had similar dystocia scores and calves were similar in BW. Complete first-lactation data (305 d) were available for 333 primiparous cows, and cows fed NP as heifers produced similar milk, fat, and protein compared with cows fed SP as heifers. Days open, days in milk at first breeding, and services per conception also were similar for primiparous cows fed NP or SP as heifers. No growth, reproductive, or lactation benefit was found by feeding dairy heifers diets containing 0.40% P compared with 0.30% P. Furthermore, P supplemented to SP heifers was simply excreted in the feces and not retained.

When fed to lactating dairy cows, management practices such as grinding corn, (Remond et al., 2004), steam flaking corn (Callison et al., 2001), feeding high moisture corn (Oba and Allen, 2003), or feeding floury corn (Allen et al., 2008), have been demonstrated to improve starch digestion and milk production of lactating dairy cows. The aforementioned management practices are common in the dairy industry and are deemed necessary to improve the feeding characteristic of corn grain. The use of these management practices brings to light a broader question—why is corn starch within the native corn kernel only partially digestible by dairy cows? This paper will review the nutritional chemistries of corn which are potentially related to starch digestibility in dairy cows.