Effect of diet energy level and genomic residual feed intake on bred Holstein dairy heifer growth and feed efficiency.

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.

Effects of feedbunk restrictions and push-up frequency on the growth performance of Holstein dairy heifers offered a forage-based diet with a limit-feeding strategy.

Conceptually, there are 2 feeding strategies for avoiding over-conditioning, which can be problematic for gravid dairy heifers that have reduced dietary energy density requirements relative to younger animals: (1) diluting the ad libitum-fed diet with low-energy forages; or (2) offering a diet of greater nutrient density but intentionally restricting the DM available for consumption (limit-feeding). Our objectives for this study were to evaluate the effects of feedbunk restriction and feed push-up frequency on the growth performance of gravid Holstein dairy heifers. A total of 128 Holstein heifers (434 ± 46.7 kg) were enrolled in the trial. Heifers were blocked by weight, and assigned to 1 of 16 identical research pens (4 pens/weight block; 8 heifers/pen), where the mean initial body weight (BW; ± SD) for the 4 blocks were 491 ± 19.0, 450 ± 16.5, 419 ± 10.6, 374 ± 23.0 kg. Within each block, a 2 × 2 factorial arrangement of treatments was assigned; treatments consisted of feedbunk access [full (FUL) or restricted (RES] and feed push-up frequency [1.5- or 3.0-h intervals]. The RES treatment was applied by covering 2 of the 8 head-locking feed gates in assigned pens with plywood partitions, thereby creating a feedbunk-stocking rate of 133%. A total mixed ration diet composed of alfalfa haylage (60.5%), corn silage (38.0%), and mineral (1.5%) was offered once daily for 91 d; daily feed allotments (overall mean = 9.11 kg dry matter (DM)/d) were generally consumed entirely within 9 h of feeding. Nutrient intakes were not affected by push-up frequency or the interaction of main effects, but all intakes were affected by feedbunk access, except for DM and neutral detergent fiber expressed as a percentage of BW (overall means = 1.93 and 0.80%, respectively). In each case, intakes for FUL were greater than those observed for RES; for DM intake, this amounted to a difference of 0.20 kg/d between those main-effect treatments. After 91 d, heifers without feedbunk restriction exhibited greater final BW, but total gain and average daily gain differed only numerically between FUL and RES. Under the conditions of this trial, heifers were blocked by weight, such that BW were relatively uniform within each pen, and head-locking feed gates were used, which also provided some protection from adjacent aggressive heifers. These results suggest heifers can exhibit acceptable growth performance on high-forage diets in a limit-feeding program that includes moderate feedbunk restriction provided other forms of stress are minimized.

Effect of diet energy density and genomic residual feed intake on prebred dairy heifer feed efficiency, growth, and manure excretion.

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.

Efficacy of recycled sand or organic solids as bedding sources for lactating cows housed in freestalls.

Our objective was to compare the composition of bedding materials and manure, cow welfare and hygiene assessments, measures of milk production and quality, and incidence of mastitis during a 3-yr trial with lactating Holstein cows housed in a freestall barn containing 4 identical pens with 32 freestalls/pen. Bedding systems evaluated included deep-bedded organic manure solids (DBOS), shallow-bedded manure solids spread over mattresses (MAT), deep-bedded recycled sand (RSA), and deep-bedded new sand (NSA). The experiment was designed as a 4 × 4 Latin square with 4 bedding systems and 4 experimental periods, but was terminated after 3 yr following discussions with the consulting statistician; therefore, data were analyzed as an incomplete Latin square. A total of n = 734 mostly primiparous cows (n = 725 primiparous, n = 9 multiparous; 224 to 267 cows/yr) were enrolled in the trial. Before placement in freestalls, organic solids (OS) exhibited lower concentrations of dry matter (36.5 vs. 94.3%), and greater concentrations of volatile solids, C, N, NH4-N, P, water-extractable P, K, and S compared with RSA or NSA. Cow comfort index was greater for sand-bedded systems compared with those using OS (88.4 vs. 82.8%). Cows bedded in systems using OS (DBOS and MAT) exhibited greater mean hock scores (1 = no swelling, no hair loss; 2 = no swelling, bald area on hock) than those bedded in sand (1.25 vs. 1.04), but this effect was entirely associated with use of mattresses (MAT), which differed sharply from DBOS (1.42 vs. 1.07). Generally, hygiene scores for legs, flanks, and udders were numerically similar for DBOS, NSA, and RSA bedding systems, and differences between bedding systems were associated entirely with MAT, yielding detectable contrasts between MAT and DBOS for legs (2.94 vs. 2.20), flanks (2.34 vs. 1.68), and udders (1.83 vs. 1.38). No significant contrast comparing bedding systems was detected for measures of milk production or quality. Documented cases of clinical mastitis requiring treatment ranged from a low rate of 7.4 cases/yr for RSA to a high of 23.1 cases/yr for DBOS, based on a mean enrollment of 60.7 to 63.0 cows/treatment per yr. Cows bedded with OS exhibited a greater incidence of mastitis than those bedded with sand (19.0 vs. 8.4 cases/yr), but no differences were observed for comparisons within individual bedding-material types. Collectively, these results generally favored use of sand-bedding materials over systems using OS.

Effects of straw processing and pen overstocking on the growth performance and sorting characteristics of diets offered to replacement Holstein dairy heifers.

Our objectives were to evaluate the effects of pen-stocking density and straw processing on the growth performance, feed-bunk sorting behaviors, and hygiene of Holstein dairy heifers. Two corn silage-alfalfa haylage diets diluted with wheat straw were offered; diet composition was identical, except that one diet contained short (well-processed) straw (SS; 46.0% neutral detergent fiber, 12.9% crude protein, 60.7% total digestible nutrients, TDN), and the other long (poorly processed) straw (LS; 46.5% neutral detergent fiber, 12.6% crude protein, 60.0% TDN; % of dry matter basis). A 2 × 3 factorial arrangement of straw-processing (SS or LS) and pen-stocking-density [100, 125, or 150% of capacity] treatments was evaluated with 240 Holstein dairy heifers (410 ± 56.3 kg) that were blocked by weight, and then assigned to 24 pens with 4 pens/interactive treatment. For 91 d, diets were dispersed at 1100 h daily, and bunks were sampled subsequently at 1300, 1600, 1900, 2200, 0100, and 0600 h during 3 evaluation periods throughout the trial. Diets were offered for ad libitum intake, but with minimal orts (<3%); as such, particle-size concentration factors were calculated as bunk concentration/initial concentration. For the LS diet, particle-size concentration factors for large (>19 mm) particles increased linearly from 1.26 to 2.82 across sampling times, differing from the SS diet at 2200, 0100, 0600, and 0900 h (orts). Similar factors calculated for the SS diet also increased linearly across sampling times, but these responses were less severe (1.27 to 1.97). Overall, particle-size concentration factors for physically effective fiber exhibited responses similar to those observed for large particles, except they were limited to narrower ranges for both the SS (1.04 to 1.14) and LS (1.03 to 1.26) diets. Despite these differences, daily dry matter intake was not affected by treatment (mean = 9.65 kg of dry matter/d), nor was daily intake of TDN (mean = 5.92 kg of TDN/d). For SS, heifers housed within overstocked pens exhibited reduced average daily gain (ADG) compared with the 100% stocking rate (0.93 vs. 0.99 kg/d). With LS processing, ADG differed between the 125 and 150% stocking rates (0.96 vs. 0.88 kg/d), as did the within-pen coefficient of variation for ADG (10.7 vs. 18.6%). Hygiene scores (1 = clean, 4 = caked-on manure) for legs (range = 2.1 to 2.3) and flanks (range = 1.6 to 1.9) indicated heifers stayed acceptably clean, but the within-pen coefficient of variation for legs (14.4 vs. 9.0%) and flanks (34.2 vs. 23.8%) was greater for overstocked pens compared with the 100% stocking density, thereby suggesting hygiene scores were more variable without a free stall for each heifer.

Effects of overstocking at the feedbunk on the growth performance and sorting characteristics of a forage-based diet offered for ad libitum intake to replacement Holstein dairy heifers.

Various forms of overcrowding are common in heifer-rearing operations. Our objectives for this study were to evaluate the effects of overstocking at the feedbunk (100, 133, 160, or 200% of capacity) on the growth performance, feedbunk sorting behaviors, and hygiene of 128 gravid Holstein heifers (475 ± 55.3 kg) consuming an alfalfa haylage and corn silage diet diluted with processed wheat straw at an inclusion rate of 25.2% (DM basis). In this study, heifers were overstocked only at the feedbunk, and not with respect to available freestalls or pen area. Heifers were blocked by weight, and subsequently assigned to 1 of 16 identical research pens. A total mixed ration was distributed at 1000 h daily for 91 d via a drive-through feed alley, with heifers allowed access to the feedbunk through head-locking feeding gates. Mean weights for the 4 blocks (32 heifers/block) were 406 ± 14.9, 453 ± 15.3, 493 ± 17.6, and 548 ± 21.9 kg. Generally, nutrient intakes were not affected by stocking rate at the feedbunk; mean intakes of dry matter, neutral detergent fiber, and total digestible nutrients across all feedbunk stocking rates were 10.63, 5.19, and 6.29 kg/d, respectively. Overall, the effects of competition at the feedbunk on heifer growth performance were minor, with a collective average daily gain of 1.02 kg/d across all treatments. Only trends for linear increases in total weight gain and BCS were observed with overstocking at the feedbunk. Collectively, overstocked rates also exhibited a trend for better feed-to-gain ratio than pens stocked at 100% of feedbunk capacity (10.3 vs. 11.0 kg:kg). We observed solid evidence that heifers collectively sorted against large (>19 mm) particles, and also exhibited preference for short (>1.18 and <8 mm) and fine (<1.18 mm) feed particles; however, these responses were not affected by feedbunk stocking rate. Additionally, heifers sorted against neutral detergent fiber as the concentration of neutral detergent fiber remaining in the feedbunk increased during the 24-h period following feeding; conversely, they preferred crude protein, as indicated by a decreasing concentration of this nutrient over time. Heifer hygiene was not affected by competition at the feedbunk. Under the experimental conditions established for this trial, overstocking at the feedbunk did not affect heifer growth performance, but it should not be practiced blindly without attention to other critical components of animal welfare.

Effects of cultivar and grazing initiation date on fall-grown oat for replacement dairy heifers.

Fall-grown oat has shown promise for extending the grazing season in Wisconsin, but the optimum date for initiating grazing has not been evaluated. Our objectives for this project were (1) to assess the pasture productivity and nutritive value of 2 oat cultivars [Ogle and ForagePlus (OG and FP, respectively)] with late-September (EG) or mid-October (LG) grazing initiation dates; and (2) to evaluate growth performance by heifers grazing these oat forages compared with heifers reared in confinement (CON). A total of 160 gravid Holstein heifers (80 heifers/yr) were assigned to 10 research groups (8 heifers/group). Mean initial body weight was 509±40.5 kg in 2013 and 517±30.2 kg in 2014. Heifer groups were assigned to specific pastures arranged as a 2×2 factorial of oat cultivars and grazing initiation dates. Grazing heifer groups were allowed to strip-graze oat pastures for 6 h daily before returning to the barn, where they were offered a forage-based basal total mixed ration. Main effects of oat cultivar and sampling date interacted for forage characteristics in 2013, but not in 2014. During 2013, oat forage mass increased until early November before declining in response to freezing weather conditions, thereby exhibiting linear and quadratic effects of sampling date, regardless of oat cultivar. Similar trends over time were observed in 2014. For 2013, the maximum forage mass was 5,329 and 5,046 kg/ha for FP and OG, respectively, whereas the mean maximum forage mass for 2014 was 4,806 kg/ha. ForagePlus did not reach the boot stage of growth during either year of the trial; OG matured more rapidly, reaching the late-heading stage during 2013, but exhibited only minor maturity differences from FP in 2014. For 2013, average daily gain for CON did not differ from grazing heifer groups (overall mean=0.63 kg/d); however, average daily gain from FP was greater than OG (0.68 vs. 0.57 kg/d), and greater from EG compared with LG (0.82 vs. 0.43 kg/d). For 2013, advantages in average daily gain for heifers grazing FP pastures were likely related to the greater energy density of FP oat throughout the fall that reached a maximum of 68.8% total digestible nutrients on November 27 compared with only 63.7% for OG on October 10. During 2014, average daily gain from CON exceeded all grazing heifer groups (0.81 vs. 0.57 kg/d), and average daily gain from EG again exceeded LG (0.70 vs. 0.44 kg/d). These results suggest that delaying grazing until mid-October will consistently suppress heifer growth performance, particularly if rapidly maturing cultivars are used.

Growth performance and sorting characteristics of corn silage-alfalfa haylage diets with or without forage dilution offered to replacement Holstein dairy heifers.

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.

Fall-grown oat to extend the fall grazing season for replacement dairy heifers.

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.

Unique interrelationships between fiber composition, water-soluble carbohydrates, and in vitro gas production for fall-grown oat forages.

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.

Using eastern gamagrass to construct diets that limit intake and caloric density for dairy replacement heifers.

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 effect of feeding dairy heifers diets with and without supplemental phosphorus on growth, reproductive efficiency, health, and lactation performance.

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.

Production, reproduction, health, and growth traits in backcross Holstein × Jersey cows and their Holstein contemporaries.

A total of 648 purebred Holstein and 319 backcross Holstein × Jersey dairy cattle were compared for production, reproduction, health, linear type, and growth traits. Animals were born between 2003 and 2009 and were housed in the University of Wisconsin-Madison Integrated Dairy Facility. All animals had Holstein dams; lactating dams were mated to unproven Holstein sires to produce purebred (control) Holsteins or to unproven F(1) Jersey × Holstein crossbred sires to produce backcross animals, whereas nulliparous dams were mated to proven Holstein sires to produce purebred (other) Holsteins. Traits were analyzed using mixed linear models with effects of season of birth, age of dam, sire, birth year of sire, days in milk, lactation, and linear type score evaluator. Control Holsteins had greater 305-d milk yield (12,645 vs. 11,456 kg), 305-d mature equivalent milk yield (13,420 vs. 12,180 kg), peak daily milk yield (49.5 vs. 46.4 kg), total lactation milk yield (11,556 vs. 10,796 kg), and daily fat-corrected milk yield (43 vs. 40 kg) compared with backcrosses. Days open and services per conception as a heifer or cow did not differ between control Holsteins, other Holsteins, or backcrosses. The proportion of first-parity births that required assistance was less in control Holsteins than in backcross cows (3.7 vs. 11.2%). The incidence of scours or respiratory problems in calves did not differ between control Holsteins, other Holsteins, and backcrosses, nor did the incidence of mastitis, injury, or feet problems. Control Holstein heifers were heavier (629 vs. 557 kg), with greater hip height (145 vs. 139 cm), body length (167 vs. 163 cm), heart girth (205 vs. 198 cm), and hip width (54 vs. 53 cm) at 22 mo of age. On a 50-point scale for linear type traits, Holsteins were larger in stature compared with backcrosses (41 vs. 28), had wider rumps (37 vs. 33), and wider rear udders (34 vs. 32). Results of this study suggest that backcross Holstein × Jersey cattle have decreased production but fail to demonstrate an advantage in health and reproduction compared with purebred Holsteins.

Influence of ensiling time and inoculation on alteration of the starch-protein matrix in high-moisture corn.

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 NH(3)-N) were evaluated. At 0 and 240 d, α, γ, δ, and ß 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 NH(3)-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.

Evaluation of potential carryover effects associated with limit feeding of gravid Holstein heifers.

Ninety-six Holstein heifers (400±6kg, 15.2±0.1 mo), including 9 with ruminal cannulas, were offered 1 of 3 diets for 180±8 d in a randomized replicated pen design. Dietary treatments included a control diet (C100) and 2 independent limit-fed (LF) diets. The LF diets included one offered at 85% of C100 intake (L85) without an ionophore, and a second containing an ionophore (325 mg/head per day of lasalocid) that was offered at 80% of C100 intake (L80+I). Heifers were evaluated for growth, rumen digesta volume, nutrient excretion, and subsequent lactation performance. Limit-fed heifers consumed less dry matter and neutral detergent fiber, and had greater respective average daily gains (0.96 or 0.89 vs. 0.81 kg/d), and lower feed:gain ratios (9.1 or 9.3 vs. 13.0 kg/kg) compared with heifers offered the C100 diet. No differences in rumen pH, NH(3)-N, or volatile fatty acid concentrations were observed between C100 and LF heifers. Rumen digesta volume, density, and weight were unaffected by LF, and feeding L85 or L80+I did not result in carryover effects for rumen digesta volume when these heifers were offered a common high-fiber diet immediately after the 180-d growth trial. At parturition, no differences were observed for dystocia index, calf body weight, or 7-d postpartum body weight between cows offered LF or C100 diets as heifers. Lactation body weight, dry matter intake, and feed efficiency of cows did not differ between treatments at 45 or 90 d in milk. Milk yield and milk components also were not different between cows that were offered C100 or LF diets as gravid heifers. At 45 d in milk, rumen digesta volume was greater (99.1 vs. 66.1L) for cows offered L85 compared with cows offered L80+I as gravid heifers, but this effect was not observed at 90 d in milk. Limit feeding of gravid Holstein heifers for 180 d did not result in any carryover effects during their first lactation for rumen digesta volume, dry matter intake, or milk yield.

The effect of dietary phosphorus on bone development in dairy heifers.

Phosphorus requirements, as percent of dietary dry matter for heifers (0.20-0.35%) and endogenous levels of P in feeds (0.20-0.35% of dry matter) are similar, suggesting that supplementation of P in heifer diets may be infrequently required. Because long-term studies are unavailable, 183 Holstein heifers and 182 Holstein x Jersey crossbred heifers were fed diets with (0.39%) and without (0.29%) supplemental P from 4 to 21 mo of age in a replicated pen design. Two subpopulations of heifers were selected mid-trial for intensive measurement of bone development and metabolism. Thirty-two heifers at 628 d (+/-10.0 d) of age, balanced by breed and diet, were evaluated for bone development. External frame measurements included hip height, length, heart girth, hip width, cannon bone circumference, pelvic length, pelvic height, and pelvic width. Tails of heifers were surgically amputated with the 13 and 14th coccygeal vertebrae retained. After tissue removal, the 13th coccygeal vertebrae were scanned using peripheral quantitative computed tomography with cortical, trabecular, and total bone densities determined. A second subpopulation (n = 64) of heifers (375 d +/- 33 d), balanced for breed and diet, were evaluated for serum pyridinoline and osteocalcin to assess systemic bone metabolism. Data were analyzed as a completely randomized design with breed, treatment, and their interaction in the model. External skeletal measurements revealed significant differences in hip height, hip width, heart girth, cannon bone circumference, and pelvic length between Holstein and crossbred heifers. Supplementing P had no effect on external frame measurements, bone density, or bone metabolism markers. Bone P content was lower (18.1 vs. 18.6%) in heifers fed no supplemental P. Data suggest P supplementation to heifers modestly increased bone P content but increased bone P was not reflected in frame growth, bone density, or bone metabolism.

Technical note: whole-pen assessments of nutrient excretion and digestibility from dairy replacement heifers housed in sand-bedded freestalls.

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.

A qualitative assessment of children's farm safety day camp programs.

In order to increase farm safety awareness and teach children good safety habits, farm safety day camp programs have been initiated in many communities. For the most part, the effectiveness of the programs is unknown because few evaluations have been performed. The purpose of this project was to qualitatively assess the overall strengths and weaknesses of farm safety day camp programs and to generate recommendations for future programs. Interviews, a literature search, and observations were used to identify strengths and weaknesses of the farm safety day camp programs. Major strengths of the programs are that: 1) positive attention is given to agriculture and agricultural safety; 2) programs are hands-on, interactive, and fun; 3) children gain knowledge about farm safety; 4) programs bring a community together to work toward a common goal; and 5) children talk to parents about safety. Key weaknesses of farm safety day camp programs are that: 1) there is a lack of parental involvement in many of the programs; 2) it is hard to change patterns of behavior in one day; 3) programs are expensive and time consuming; 4) curricula may include content that is inaccurate or inappropriate for the age of participants; and 5) evaluation is difficult. When done well, farm safety day camp programs can teach children about safety and influence safety practices affecting children on the farm. Recommendations for future farm safety day camp programs are: 1) ensure that child-development principles are applied to all aspects of program activities and curricula; 2) provide session leaders with accurate and relevant content; 3) increase parental involvement; and 4) address safety issues throughout the year.

Short communication: Effect of dietary protein on growth and nitrogen balance of Holstein heifers.

A growth study and a companion N balance study were conducted to evaluate the effect of dietary protein on growth and N utilization of postpubertal Holstein heifers. Forty heifers (398 +/- 9.4 kg) were fed one of four diets containing 8, 11, 13, or 15% crude protein (CP) for 121 d. Body measurements were taken at the beginning and end of the experimental period. Blood was collected via jugular vein every 28 d and evaluated for serum protein, albumin, and urea nitrogen. Curvilinear relationships were observed between dietary CP and gains in wither height and hip width, with maximal gains occurring at 13% CP. Feeding heifers higher amounts of dietary CP resulted in linear increases in heart girth gain, serum protein, albumin, and blood urea nitrogen. In the companion N balance study, feeding increasing amounts of dietary CP to heifers resulted in linear increases in N intake, fecal-N, urinary-N, and absorbed-N. There was a numerical trend towards maximal N retention in heifers fed diets containing 13% CP. Curvilinear relationships also were observed between dietary CP and dry matter, organic matter, and CP digestibility with maximal nutrient digestibilities occurring when heifers were fed diets containing 13% CP. Data suggest 13% dietary CP was optimal for postpubertal (400 kg) Holstein heifers.