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Our objective was to evaluate the effect of metabolizable protein (MP) supply on milk production, blood metabolites, and health in dairy cows during early lactation. Three experimental diets were formulated to contain 114, 107, 101 g of MP/kg of dry matter (DM; 114MP, 107MP, and 101MP, respectively) with crude protein contents of 17.0, 16.2, and 15.3% of DM, respectively. One hundred multiparous Holstein cows were fed 1 of these 3 diets during wk 1 to 3 and wk 4 to 13 of lactation in one of the following sequences: (1) 114MP and 107MP (114MP/107MP), (2) 114MP and 101MP (114MP/101MP), or (3) 101MP and 101MP (101MP/101MP). During wk 1 to 3, the 114MP and 101MP treatments were 20 and 27% deficient in estimated MP, respectively. From wk 4 to 13, the 114MP/107MP, 114MP/101MP, and 101MP/101MP treatments were 8, 12, and 13% deficient in estimated MP, respectively. Data were analyzed separately for wk 1 to 3, 4 to 13, and 1 to 13. Dry matter intake and energy-corrected milk (ECM) yield were not affected by treatment during wk 4 to 13 or wk 1 to 13; however, ECM yield decreased for 101MP versus 114MP from wk 1 to 3. Similarly, feed efficiency was not affected by treatment from wk 4 to 13 or wk 1 to 13, and was reduced with 101MP versus 114MP during wk 1 to 3. Milk N efficiency tended to increase for 101MP versus 114MP for wk 1 to 3 and increased with 101MP/101MP and 114MP/101MP relative to 114MP/107MP during wk 4 to 13 and wk 1 to 13. Treatment had no influence on yields and concentrations of milk components from wk 4 to 13 or wk 1 to 13; however, compared with 114MP, feeding 101MP tended to decrease milk fat yield and decreased yields of milk true protein and lactose for wk 1 to 3. Both milk and blood urea N concentrations decreased for 101MP/101MP and 114MP/101MP relative to 114MP/107MP during wk 4 to 13 and wk 1 to 13, and were reduced with feeding 101MP versus 114MP from wk 1 to 3. Treatment had no effect on the incidence of diseases in cows throughout the study. Serum concentrations of total fatty acids, albumin, and aspartate aminotransferase did not differ between 101MP and 114MP; however, serum β-hydroxybutyrate concentration was lower in cows receiving 101MP during the first 3 wk of lactation. Compared with 114MP, feeding 101MP during wk 1 to 3 increased plasma concentrations of creatinine and 3-methylhistidine (3-MHis) but did not change the ratio of plasma 3-MHis to creatinine. We found no differences in plasma creatinine or the ratio of 3-MHis-to-creatinine among treatments from wk 4 to 13; however, 101MP/101MP and 114MP/101MP had elevated plasma 3-MHis compared with 114MP/107MP. Treatment had no effect on body weight and body condition score over the duration of the study. Collectively, despite reduced milk production for the first 3 wk of lactation, feeding the 101MP/101MP treatment sustained lactational performance and improved milk N efficiency without negatively affecting the frequency of diseases in dairy cows during the first 13 wk postpartum.

The effect of neutral detergent fiber (NDF) degradability of corn silage in diets containing lower and higher NDF concentrations on lactational performance, nutrient digestibility, and ruminal characteristics in lactating Holstein cows was measured. Eight ruminally cannulated Holstein cows averaging 91 ± 4 (standard error) days in milk were used in a replicated 4 × 4 Latin square design with 21-d periods (7-d collection periods). Dietary treatments were formulated to contain either conventional (CON; 48.6% 24-h NDF degradability; NDFD) or brown midrib-3 (BM3; 61.1% 24-h NDFD) corn silage and either lower NDF (LNDF) or higher NDF (HNDF) concentration (32.0 and 35.8% of ration dry matter, DM) by adjusting the dietary forage content (52 and 67% forage, DM basis). The dietary treatments were (1) CON-LNDF, (2) CON-HNDF, (3) BM3-LNDF, and (4) BM3-HNDF. Data were analyzed as a factorial arrangement of diets within a replicated Latin square design with the MIXED procedure of SAS (SAS Institute Inc., Cary, NC) with fixed effects of NDFD, NDF, NDFD × NDF, period(square), and square. Cow within square was the random effect. Time and its interactions with NDFD and NDF were included in the model when appropriate. An interaction between NDFD and NDF content resulted in the HNDF diet decreasing dry matter intake (DMI) with CON corn silage but not with BM3 silage. Cows fed the BM3 corn silage had higher DMI than cows fed the CON corn silage, whereas cows fed the HNDF diet consumed less DM than cows fed the LNDF diet. Cows fed the BM3 diets had greater energy-corrected milk yield, higher milk true protein content, and lower milk urea nitrogen concentration than cows fed CON diets. Additionally, cows fed the BM3 diets had greater total-tract digestibility of organic matter and NDF than cows fed the CON diets. Compared with CON diets, the BMR diets accelerated ruminal NDF turnover. When incorporated into higher NDF diets, corn silage with greater in vitro 24-h NDFD and lower undegradable NDF at 240 h of in vitro fermentation (uNDF240) allowed for greater DMI intake than CON. In contrast, for lower NDF diets, NDFD of corn silage did not affect DMI, which suggests that a threshold level of inclusion of higher NDFD corn silage is necessary to observe enhanced lactational performance. Results suggest that there is a maximum gut fill of dietary uNDF240 and that higher NDFD corn silage can be fed at greater dietary concentrations.

The effects of source of corn silage and trace mineral on rumen fermentation, turnover, and particle passage rates were evaluated with 8 ruminally cannulated Holstein cows averaging 83 (standard error = 5) days in milk in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments and 28-d periods. The diets consisted (dry basis) of 55% conventional (CON) or brown midrib-3 (BM3) corn silage, 2% chopped wheat straw, and 43% grain mix with either sulfate (STM) or hydroxy (HTM) source of Cu, Zn, and Mn trace minerals. The targeted supplemental amount of Cu, Zn, and Mn was 194, 1,657, and 687 mg/d, respectively. The dietary treatments were (1) CON-STM, (2) CON-HTM, (3) BM3-STM, and (4) BM3-HTM. Dietary nutrient composition of BM3 diets averaged 32.1% amylase neutral detergent fiber on an organic matter basis (aNDFom) and 6.9% undigested neutral detergent fiber at 240 h of in vitro fermentation (uNDF240om; % of dry matter), and CON diets averaged 36.2% aNDFom and 8.6% uNDF240om (% of dry matter). Data were summarized by period and analyzed as a replicated Latin square design with fixed model effects for corn silage, trace mineral, corn silage and trace mineral interaction, period within replicated square, and replicated square using the MIXED procedure of SAS (version 9.4, SAS Institute Inc., Cary, NC). Cow within replicate was a random effect. Daily mean, standard deviation, minimum, and maximum for rumen pH were unaffected by corn silage or trace mineral source. Cows fed the CON diets had greater rumen acetate percentage than cows fed the BM3 diets (65.7 vs. 64.7 molar %). In contrast, cows fed the BM3 diets had greater rumen propionate percentage than cows fed the CON diets (21.4 vs. 20.4 molar %). Total volatile fatty acid concentration was lower for cows fed STM versus HTM in BM3 diets, but not for the cows fed the CON diets. Cows fed the BM3 diets had faster turnover rate and shorter turnover time for uNDF240om than cows fed the CON diets (3.12 vs. 2.86%/h and 33.3 vs. 36.5 h, respectively). Cows fed the BM3 diets had a faster passage rate of small and medium corn silage neutral detergent fiber particles than cows fed the CON diets (5.73 vs. 5.37%/h and 4.74 vs. 4.31%/h, respectively). We observed a corn silage by source of trace mineral interaction on organic matter and uNDF240om rumen pool size and organic matter turnover. Overall, source of corn silage had a pronounced influence on rumen dynamics presumably related to greater in vitro neutral detergent fiber digestibility and lower uNDF240om content of BM3 corn silage that allowed for faster turnover of indigestible neutral detergent fiber and greater passage rate of corn silage particles. In contrast, the source of trace mineral had much less significant effects on rumen fermentation, turnover, and particle passage rates. Corn silage-based diets intended to enhance rumen fiber fermentation, turnover, and passage are more affected by source and digestibility of neutral detergent fiber than source of dietary trace minerals.

The objectives of this study were to (1) describe the calving location of dairy cattle given access to a pasture and barn; (2) identify factors associated with calving location; and (3) compare the lying and exploratory behavior of cows in the 24 h before calving and a previous day. Seventy-two Holstein dairy heifers and cows (n = 36 nulliparous and n = 36 primiparous and multiparous combined) were housed in a covered bedded-pack barn (167.4 m2) with free access to 2.1 ha of pasture. The composition of the group was dynamic, because cows were moved in weekly at 19 ± 6 d [mean ± standard deviation (SD)] before their calving date, and were removed immediately after calving. To facilitate data collection, we divided the environment into 9 sections, including the barn (section 1; 167.4 m2), 7 sections of open pasture (sections 2 to 8; 2,402 ± 60 m2), and 1 section of pasture surrounded by natural forage cover (section 9; 3,593 m2). We then collapsed these 9 sections into 3 distinct areas for further analysis: the barn, open pasture, and natural forage cover. Animals were fitted with accelerometers to measure lying time, lying bout duration, lying bouts, and steps for the 24 h before calving (calving day) and a similar 24 h period 4 to 11 d (median = 7) before calving (baseline day). We included parity (nulliparous vs. primiparous and multiparous) and heat stress [no heat stress = temperature-humidity index (THI) ≤68 vs. heat stress = THI >68 and ≤79] in all analyses; we included time of day and group composition as additional factors that may have affected calving location. We determined exploratory behavior using 10 min instantaneous scan sampling collected from video. At each scan, we recorded the section (1 to 9) the cow or heifer was located in, and then calculated the minimum number of sections that could be crossed between successive scans. Of the total sample, 39% calved in the barn, 26% calved in the open pasture, and 35% calved in the area with natural forage cover. Nulliparous heifers and those calving when heat stress was low (THI ≤68) selected the area with natural forage cover more frequently than the barn. On the calving day, cows spent more time lying down with more short bouts of lying, and crossed more sections compared with the baseline day. Steps were affected by an interactive effect of day, parity, and heat stress; nulliparous heifers took more steps on the calving day during conditions of heat stress compared with no heat stress. Results indicate that cows and heifers had different preferences for their environment at calving, and when provided access to pasture, both changed their lying and exploratory behavior on the day of calving compared with a previous day.

We evaluated the effects of source of corn silage and trace minerals on lactational performance and total-tract digestibility (TTD) of nutrients in 16 Holstein cows averaging 82 (standard error = 3) days in milk in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments with 28-d periods. The diets consisted [dry matter (DM) basis] of 55% conventional (CON) or brown midrib-3 (BM3) corn silage, 2% chopped wheat straw, and 43% grain mix with either sulfate (STM) or hydroxy (HTM) sources of copper, manganese, and zinc trace minerals. The targeted supplemental concentrations of copper, zinc, and manganese were 194, 1,657, and 687 mg/d, respectively. The dietary treatments were CON-STM, CON-HTM, BM3-STM, and BM3-HTM. The dietary nutrient composition of the BM3 diets averaged 32.1% amylase neutral detergent fiber on an organic matter basis (aNDFom) and 6.9% undigested neutral detergent fiber at 240 h (uNDF240om; % of DM), and CON diets averaged 36.2% aNDFom and 8.6% uNDF240om (% of DM). The average supplemental concentrations of copper, zinc, and manganese for the STM diets were 10, 41, and 64 mg/kg, respectively, and the average supplemental concentrations of copper, zinc, and manganese for the HTM diets were 10, 40, and 62 mg/kg, respectively. The average total dietary concentrations of copper, zinc, and manganese for the STM diets were 17, 104, and 60 mg/kg, respectively, and the average total dietary concentrations of copper, zinc, and manganese for the HTM diets were 17, 91, and 66 mg/kg, respectively. Data were summarized by period and analyzed as a replicated Latin square design with fixed model effects for corn silage, trace minerals, corn silage × trace mineral interaction, period within replicated square, and replicated square using the MIXED procedure of SAS. Cow within replicated square was a random effect. Cows fed the BM3 diets had greater dry matter intake (DMI) and milk yield (28.1 and 47.0 kg/d) than cows fed the CON diets (27.5 and 44.7 kg/d). We found no significant interaction between corn silage and trace minerals for DMI and milk yield. Cows fed the HTM diets (28.1 kg/d) had a greater DMI than cows fed the STM diets (27.5 kg/d). Cows fed the BM3 diets had greater TTD of DM and OM (72.8 and 74.1% of DM) than cows fed the CON diets (71.1 and 72.3% of DM). Cows fed the HTM diets had a tendency for greater TTD of aNDFom than cows fed the STM diets (56.8 vs. 54.9% of DM). Cows fed the CON diets ruminated longer during the day than cows fed the BM3 diets (524 vs. 496 min/d). Corn silage with greater NDF digestibility and lower uNDF240om enhanced DMI, milk yield, and TTD of DM and OM, and hydroxy trace minerals improved DMI and tended to improve TTD of aNDFom. The source of corn silage and trace minerals should be taken into consideration when formulating diets for high-producing dairy cows.

We determined the effect of prepartum plane of energy intake on liver function and metabolism pre- and postpartum by combining in vivo and in vitro data with mRNA expression data. A subset of multiparous prepartal Holsteins (n = 18) from a previously conducted experiment consumed 1 of 3 amounts of dietary energy intake, relative to their requirements. A diet formulated to allow consumption of ≥150% of net energy requirements during the far-off dry period and the close-up dry period was fed for ad libitum intake (150E) or in restricted amounts so that cows consumed 80% of requirements for energy (80E). A second diet was formulated to include wheat straw (26.1% of dry matter) to limit energy intake to 100% of NRC (2001) requirements for energy when fed ad libitum during the far-off period (100E). In the close-up period, 100E was fed the 150E diet for ad libitum intake. Expression of mRNA for genes related to fatty acid oxidation (PPARA, CPT1A, ACOX1) was greater for 100E cows than 150E cows on d 14 postpartum. These expression patterns were related to in vitro data for conversion of palmitate to CO

Dry matter intake, lactation performance, and chewing behavior of multiparous Holstein cows (n = 15) fed diets containing a novel bm3 corn silage hybrid with floury kernel genetics were compared with cows fed diets containing commercially available conventional and bm3 hybrids using a replicated 3 × 3 Latin square design with 28-d periods. Cows were housed in tiestalls, milked 3 times/d, and fed a total mixed ration containing 49.0% (dry matter basis) of (1) a conventional corn silage hybrid (CONV); (2) a brown midrib bm3 hybrid (BMR); or (3) a bm3 hybrid with floury kernel genetics (BMRFL). All diets contained 6.3% hay crop silage and 44.7% concentrate. Dietary nutrient composition averaged 32.7% neutral detergent fiber (NDF) and 26.3 starch (% of dry matter). Data were analyzed by ANOVA using the MIXED procedure in SAS (SAS Institute Inc., Cary, NC). The dry matter intake was greater for cows fed BMR (28.0 kg/d) compared with CONV (26.8 kg/d), whereas dry matter intake for cows fed BMRFL was intermediate (27.6 kg/d). Energy-corrected milk (ECM) yield was greater for cows fed BMR (50.3 kg/d) and BMRFL (51.8 kg/d) compared with CONV (47.2 kg/d). Milk fat yield was higher for cows fed BMRFL (1.87 kg/d) compared with CONV (1.74 kg/d) and BMR (1.80 kg/d). Milk protein yield was greater for cows fed BMR (1.49 kg/d) and BMRFL (1.54 kg/d) compared with CONV (1.36 kg/d). Milk urea-N was reduced for cows fed BMR (11.61 mg/dL) and BMRFL (11.16 mg/dL) compared with CONV (13.60 mg/dL). Feed efficiency (ECM/dry matter intake) was higher for cows fed BMRFL (1.87) compared with CONV (1.76) and BMR (1.79). Milk N efficiency was greatest for cows fed BMRFL (40.4%) followed by BMR (38.1%) and finally CONV (35.3%). Cows fed CONV chewed 5 min more per kilograms of NDF consumed than cows fed either of the BMR hybrids. No differences were observed among diets in apparent total-tract digestibility of NDF (58.1%) or starch (99.3%). Overall lactational performance was enhanced for cows fed diets containing both BMR and BMRFL hybrids versus CONV. In addition, feeding the BMRFL corn silage improved efficiency of component-corrected milk production and milk N efficiency compared with the CONV and BMR silages.

In natural settings, dairy cows separate from the herd to give birth. When kept indoors, seeking isolation before calving may be restricted and may depend on space and resources provided in maternity housing. The effect of group maternity pens on behavior around calving and labor progress is unknown. Therefore, the objective of this study was to determine the effects of stocking density and provision of a blind in group bedded pack maternity pens on lying and social behavior as well as length of labor of preparturient dairy animals. The study was conducted as a complete randomized block design with a 2 × 2 factorial arrangement of treatments including stocking density and presence or absence of a blind, resulting in a total of 4 treatments: (1) high stocking density (7.7-12.9 m2 lying space/cow) with a blind, (2) low stocking density (15.4-25.8 m2) with a blind, (3) high stocking density without a blind, and (4) low stocking density without a blind. A total of 127 primiparous heifers and 247 multiparous cows were housed in mixed-parity groups from approximately 3 wk before and immediately after calving. During the 4 h before calving, lying behavior (lying time and bouts) was collected automatically using accelerometers, and social behavior (agonistic interactions, allogrooming, and attention from other cows), stage II labor duration, and frequency of position change during stage II labor were collected using video. Lying behavior was collected with accelerometers. Regardless of treatment, lying time and bouts increased as calving approached. Cows and heifers performed more lying bouts in low stocking density pens compared with high stocking density pens. Agonistic interactions and allogrooming were not different between treatments. Other cows spent more time paying attention to focal animals regardless of stocking density as calving approached, but time spent paying attention was reduced by the presence of a blind during h -2 before calving. The hazard of calving unassisted was greater for cows and heifers in low stocking density pens with a blind compared with all other treatments. Further, animals in pens with a blind tended to change positions fewer times during stage II labor. These results suggest that providing a blind in group maternity pens may improve the calving environment for cows and heifers and, in combination with low stocking density, may reduce the amount of time spent in labor.

In a more natural setting, dairy cows separate from herdmates and seek a secluded area to give birth. However, on many dairy facilities, cows calve in barren group pens with limited space, which may limit their ability to perform these behaviors. The objective of this study was to determine the effect of stocking density and provision of a blind (a single-sided solid partition) in group bedded pack maternity pens on the behavior of dairy cattle. The study included 4 experimental treatments: (1) high stocking density (7.7–12.9 m2 of lying space/cow) with a blind, (2) low stocking density (15.4–25.8 m2) with a blind, (3) high stocking density without a blind, and (4) low stocking density without a blind. We analyzed the effect of these treatments on locomotor and separation behavior as well as blind use during the 24 h before calving. A total of 127 primiparous heifers and 247 multiparous cows were housed in 16 mixed-parity groups (4 groups per treatment) from approximately 3 wk before to immediately after calving. Locomotor behavior increased from 24 to 2 h before calving regardless of treatment but increased the most in high stocking density pens without a blind. Additionally, heifers performed more locomotion than cows. Animals increased their distance from other cows beginning approximately 4 h before calving. Animals in low stocking density pens had a greater distance from other cows compared with those in high stocking density pens. Additionally, heifers had a greater distance from penmates during the 4 h before calving than cows. More animals calved in the area of the pen that contained a blind compared with the same respective areas of high and low stocking density pens that did not contain a blind. These results suggest that periparturient dairy cattle in group maternity pens are motivated to seek seclusion at calving, but increased stocking density may impede their ability to do so. Providing additional space and a blind may benefit periparturient dairy cows and heifers by facilitating natural calving behaviors.

The objective of this trial was to compare a powdered 0.5% chlorhexidine acetate-based postmilking teat dip with a foamed 1% iodine-based postmilk teat dip during winter on clinical mastitis, subclinical mastitis (somatic cell count ≥200,000 cells/mL), linear score, teat skin condition, teat end score for hyperkeratosis, and risk of developing a new intramammary infection (IMI). Holstein cows (n = 331) housed in freestall and tiestall barns on one farm were blocked by pen, parity, lactation stage, and lactation performance. They were assigned randomly to a powdered chlorhexidine postmilking teat dip (PD; Derma Soft n' Dry, IBA Inc., Millbury, MA) or a foamed iodine-based postmilking teat dip (ID; FS-103, IBA Inc.). Treatments were applied for 6 wk starting January 4, 2016, for 3 milkings per day. Milk samples were collected from each quarter at the beginning and end of the trial and analyzed for aerobic culture and somatic cell count. Cows that had a clinical mastitis event during the trial were quarter sampled for aerobic culture at the time of clinical event. Teat skin condition and teat end score for hyperkeratosis were evaluated at the beginning, middle, and end of the trial based on a 3- and 5-point scale, respectively. No treatment difference was observed for linear score or teat skin condition. Teat end score was greater for ID cows compared with PD cows (2.72 vs. 2.77) at the conclusion of the trial. At the beginning of trial 102 PD quarters and 129 ID quarters had an IMI identified on aerobic culture, 402 PD and 457 ID quarters cultured negative, and 109 PD and 125 ID samples were classified as “no significant growth.” At the conclusion of the trial, 129 PD and 101 ID quarters had an IMI. Use of PD resulted in a greater risk for developing a new IMI, based on bacteriological culture, at the conclusion of the trial as compared with ID (relative risk = 1.51; confidence interval: 1.10–2.07). Additionally, use of PD resulted in a greater risk as compared with ID of coagulase-negative staphylococci (relative risk = 1.5; confidence interval: 1.10–2.25) and Staphylococccus aureus (relative risk = 2.30; confidence interval: 1.04–5.07) to be present at the conclusion of the trial. In conclusion, use of PD led to a lower teat end score, an increase in new IMI, and an increased risk of coagulase-negative staphylococci and Staph. aureus compared with ID after 6 wk of product use.

Many dairy cows succumb to disease after calving. Disease risk may be affected by the cows' social environment and ability to perform maternal behaviors. In nature, cattle isolate from others and find seclusion to give birth; these behaviors may be limited in indoor group pens and could potentially affect the cows' ability to cope. The aim was to determine whether stocking density and a physical blind in prepartum bedded-pack group pens affected physiological biomarkers, disease risk, and hygiene of peripartum dairy cows. A randomized complete block designed with a 2 × 2 factorial arrangement of treatments was used. Approximately 3 wk before calving, 374 cows (primiparous = 127; multiparous = 247) were assigned randomly to 1 of 4 treatment pens with the following 2 factors: (1) high versus low stocking density (7.7 to 12.9 m2 vs. 15.4 to 25.8 m2 lying space per cow), and (2) presence or absence of a blind. The blind was created using plastic road barriers and plywood, a steel gate, and shade cloth. After calving, cows were moved into a freestall pen and milked 3 times per day. Blood was sampled on the day of enrollment (baseline; -24 d) and approximately -14, -7, 3, 7, 10, and 14 d relative to calving, to measure inflammatory (haptoglobin) and metabolic (nonesterified fatty acids and β-hydroxybutyrate) biomarkers. β-Hydroxybutyrate (≥1.2 mmol/L) was used to diagnose subclinical ketosis. Vaginal discharge was scored 3, 7, 10, and 14 d after calving, to diagnose metritis (none, mild, or severe). Hygiene was scored on -24, -14, and -7 d before calving. Before calving, haptoglobin was lower in pens with a blind. After calving, cows in pens with low stocking density before calving tended to be at greater odds of being diagnosed with metritis. Cows were more likely to have poorer hygiene scores in high stocking density pens. No treatment effects were detected for pre- and postpartum nonesterified fatty acids, β-hydroxybutyrate, postpartum haptoglobin, or subclinical ketosis. Results suggest that the provision of a blind and lower stocking density may be beneficial for reducing inflammation before calving. However, low prepartum stocking density might increase the odds of metritis after calving. Although the reason for this paradox is unclear, the effects of prepartum stocking density may require further exploration.

The objective of this study was to evaluate the relationship of management practices and dietary factors with de novo fatty acid concentration in bulk tank milk from commercial dairy farms milking Holstein cows. Farms were selected based on de novo fatty acid concentration during the 6 mo before the farm visit and were categorized as high de novo (HDN; 24.61 ± 0.75 g/100 g of fatty acids, mean ± standard deviation; n = 19) or low de novo (LDN; 23.10 ± 0.88 g/100 g of fatty acids; n = 20). Farms were visited once in February, March, or April 2015 and evaluated based on management and facility design known to affect cow behavior, physical and chemical characteristics of the diet, and ration formulation and forage analyses obtained from the farm's nutritionist. We observed no differences between HDN and LDN farms in farm size, time away from the pen for milking, days in milk, or body condition score. We detected no differences between HDN and LDN farms in milk fat or true protein yield; however, milk fat and protein content and de novo fatty acid yield per day were higher for HDN farms, as was gross income per unit of milk sold. High de novo farms tended to be more likely to deliver fresh feed twice versus once per day, have a freestall stocking density ≤110%, and provide ≥46 cm of feed bunk space per cow. We observed no detectable differences in forage quality or ration dry matter, crude protein, or starch content. However, ether extract was lower and physically effective neutral detergent fiber was higher for HDN farms. Feeding management, stocking density, dietary ether extract content, and the physical characteristics of the diet are related to de novo fatty acid, fat, and protein concentration in bulk tank milk from high-producing Holstein dairy farms.

Overstocking can be a major issue in the dairy cattle industry, leading to negative changes in feeding and resting behavior. Additional stress imposed and alterations in feeding behavior may significantly impact the rumen microbiome. The rumen microbiome is responsible for the successful conversion of feed to usable energy for its host. Thus, understanding the effects of stocking density on the rumen microbiome is imperative for further elucidation of potentially negative consequences of overstocking in dairy cattle. This study implemented a Latin Square design accounting for four pens of cattle and four treatment periods so that all treatment combinations were assigned to every pen during one period of the study. Two treatment factors, including two levels of physically effective neutral detergent fiber, achieved with addition of chopped straw, and stocking density (100% vs. 142%) of freestalls and headlocks, were combined and tested within a factorial treatment design. Within each pen, three or four cannulated cows (n = 15 total) were sampled for rumen content on the final day of each treatment period. Each treatment was randomly assigned to a single pen for a 14-day period. The V1–V3 hypervariable regions of the 16S rRNA gene were targeted for bacterial analyses. Variables with approximately normally-distributed residuals and a Shapiro–Wilk statistic of ≥0.85 were analyzed using a mixed model analysis of variance with the GLIMMIX procedure with fixed effects of feed (straw vs. no straw), stocking density (100% vs. 142%), and the interaction of feed × stocking density, and random effects of pen, period, feed × stocking × pen × period. Pen was included as the experimental unit in a given period and the sampling unit as cow. Variables included Shannon’s Diversity Index, Faith’s phylogenetic diversity index, chao1, observed OTU, and Simpson’s evenness E as well as most individual taxa. Data were analyzed in SAS 9.4 utilizing the GLIMMIX procedure to perform mixed model analysis of variance. If data were not normally distributed, a ranked analysis was performed. No differences were observed in α-diversity metrics by fiber or stocking density (P > 0.05). Beta diversity was assessed using weighted and unweighted Unifrac distances in QIIME 1.9.1 and analyzed using ANOSIM. No differences were observed in weighted (P = 0.6660; R = −0.0121) nor unweighted (P = 0.9190; R = −0.0261) metrics and R values suggested similar bacterial communities among treatments. At the phylum level, Tenericutes differed among treatments with an interaction of stocking density by feed (P = 0.0066). At the genus level, several differences were observed by treatment, including Atopobium (P = 0.0129), unidentified members of order RF39 (P = 0.0139), and unidentified members of family Succinivibrionaceae (P = 0.0480). Although no diversity differences were observed, taxa differences may indicate that specific taxa are affected by the treatments, which may, in turn, affect animal production.

Increases in grain prices have led to renewed interest in feeding reduced-starch diets to lactating dairy cows. An experiment was conducted to determine the effects of altering carbohydrate sources and reducing dietary starch on lactational performance, feeding behavior, and ruminal measures of Holstein dairy cows. Fifteen multiparous cows (6 ruminally cannulated) were blocked and assigned to 1 of 5 squares and used in a replicated 3×3 Latin square design with 21-d periods. Cows were fed 1 of 3 experimental diets: a control diet containing 20% brown midrib corn silage, 20% conventional corn silage, and 10% hay crop silage (CON); a reduced-starch high-forage diet containing 53% brown midrib corn silage and 10% hay crop silage (HFOR); and a reduced-starch diet containing the same forages as CON with partial replacement of corn meal by nonforage fiber sources (HNFFS). The CON diet contained (% of dry matter) 26.0% starch and 34.7% neutral detergent fiber (NDF), whereas the HFOR and HNFFS diets contained 21.4 or 21.3% starch and 38.3 or 38.0% NDF, respectively. Dry matter intake tended to be greater for cows fed the CON diet (28.2 kg/d) compared with those fed the HFOR diet (27.2 kg/d). Dry matter intake for cows fed the HNFFS diet was intermediate (27.7 kg/d). Milk yield was greater for cows fed the CON diet (51.6 kg/d) compared with those fed the HFOR diet (48.4 kg/d), but milk fat content tended to increase for cows fed the HFOR diet (3.98%) compared with those fed the CON diet (3.66%). Consequently, fat-corrected and solids-corrected milk yields were unaffected by dietary treatments. Total chewing, eating, and rumination times were similar across all dietary treatments. Rumination time per kilogram of DM was greatest for the HFOR diet, intermediate for the HNFFS diet, and least for the CON diet, whereas rumination time per kilogram of NDF was greatest for the CON diet and least for the HNFFS diet. Mean ruminal pH, NH3-N (mg/dL), and total volatile fatty acid concentrations (mM) were similar across all dietary treatments. Molar proportion of ruminal acetate (mol/100 mol) was increased for cows fed the HFOR diet compared with cows fed the CON diet. Microbial N yield measured by urinary purine derivatives was unaffected by dietary treatment. Reduced-starch diets containing greater amounts of high quality, highly digestible forage or nonforage fiber sources in place of corn meal resulted in similar fat-corrected or solids-corrected milk yield for high-producing dairy cows in the short term.

The objective of this experiment was to measure ruminal and lactational responses of Holstein dairy cows fed diets containing 3 different starch levels: 17.7 (low; LS), 21.0 (medium; MS), or 24.6% (high; HS). Twelve multiparous cows (118 ± 5 d in milk) were assigned randomly to dietary treatment sequence in a replicated 3 × 3 Latin square design with 3-wk periods. All diets were fed as total mixed rations and contained approximately 30.2% corn silage, 18.5% grass silage, and 5.0% chopped alfalfa hay. Dietary starch content was manipulated by increasing dry ground corn inclusion (% of dry matter) from 3.4 (LS) to 10.1 (MS) and 16.9 (HS) and decreasing inclusion of beet pulp and wheat middlings from 6.7 and 13.4 (LS) to 3.4 and 10.1 (MS) or 0 and 6.8 (HS). In vitro 6-h starch digestibility of the diet increased as nonforage sources of fiber replaced corn grain (% of dry matter; 73.6, HS; 77.3, MS; 82.5, LS) resulting in rumen-fermentable starch content by 14.6, 16.2, and 18.1% for the LS, MS, and HS diets, respectively. Diets had similar neutral detergent fiber from forage and particle size distributions. Dry matter intake, solids-corrected milk yield, and efficiency of solids-corrected milk production were unaffected by diet, averaging 26.5 ± 0.8, 40.8 ± 1.6, and 1.54 ± 0.05 kg/d, respectively. Reducing dietary starch did not affect chewing time (815 ± 23 min/d), mean ruminal pH over 24h (6.06 ± 0.12), acetate-to-propionate ratio (2.4 ± 0.3), or microbial N synthesized in the rumen (585 ± 24 g/d). Total tract organic matter digestibility was higher for HS compared with MS and LS diets (69.2, 67.3, and 67.0%, respectively), but crude protein, neutral detergent fiber, and starch digestibilities were unaffected. As dietary starch content decreased, in vitro ruminal starch fermentability increased and, consequently, the range between HS and LS in rumen-fermentable starch (3.5 percentage units) was less than the range in starch content (6.9 percentage units). Under these conditions, dietary starch content had no measurable effect on ruminal fermentation or short-term lactational performance of high-producing Holstein dairy cows.

The objective of this research was to measure the effects of increased stocking density of stalls and headlocks on the short-term behavioural responses of lactating Holstein cows. Multiparous ( n =92) and primiparous ( n =44) cows were assigned to four pens of 34 cows each and stocking densities (100, 113, 131, or 142%) were imposed in a 4×4 Latin square design with 7-d periods. Stocking density was adjusted by altering access to free stalls and headlocks. Activity of the cows was recorded continuously with digital video cameras for the last 2d at each stocking density and time spent as well as mean percentage of cows engaged in lying, standing, and feeding at each 10min scan sample was determined. Mean percentage of cows feeding over a 24-h period was approximately 20.5% and cows spent approximately 5h/d feeding, but the percentage of cows feeding during the first 60min following return from the milking parlour declined ( P P P

This study investigated the relationship of management practices, dietary characteristics, milk composition, and lactation performance with de novo fatty acid (FA) concentration in bulk tank milk from commercial dairy farms with Holstein, Jersey, and mixed-breed cows. It was hypothesized that farms with higher de novo milk FA concentrations would more commonly use management and nutrition practices known to optimize ruminal conditions that enhance de novo synthesis of milk FA. Farms (n=44) located in Vermont and northeastern New York were selected based on a history of high de novo (HDN; 26.18±0.94g/100g of FA; mean ± standard deviation) or low de novo (LDN; 24.19±1.22g/100g of FA) FA in bulk tank milk. Management practices were assessed during one visit to each farm in March or April, 2014. Total mixed ration samples were collected and analyzed for chemical composition using near infrared spectroscopy. We found no differences in days in milk at the farm level. Yield of milk fat, true protein, and de novo FA per cow per day were higher for HDN versus LDN farms. The HDN farms had lower freestall stocking density (cows/stall) than LDN farms. Additionally, tiestall feeding frequency was higher for HDN than LDN farms. No differences between HDN and LDN farms were detected for dietary dry matter, crude protein, neutral detergent fiber, starch, or percentage of forage in the diet. However, dietary ether extract was lower for HDN than LDN farms. This research indicates that overcrowded freestalls, reduced feeding frequency, and greater dietary ether extract content are associated with lower de novo FA synthesis and reduced milk fat and true protein yields on commercial dairy farms.

Two experiments were conducted to determine the effect of malic acid supplementation on: (1) nutrient digestibility and metabolism of ruminal microorganisms in continuous culture of rumen contents and (2) lactation performance of mid-lactation dairy cows and total tract nutrient digestibility. In experiment 1, digestibility of acid detergent fiber (ADF) and neutral detergent fiber (aNDF) was higher (P 0.05) the production of total volatile fatty acids, propionic acid, butyric acid, and isobutyric acid, the ratio of acetic to propionic acid, or pH. Microbial nitrogen (N) production and efficiency of organic matter (OM) and total carbohydrate use for microbial N production increased (P 0.05) of malic acid supplementation on content of fat, true protein, or lactose in milk. However, yield of true protein and lactose was higher (P 0.05) by malic acid supplementation. In conclusion, malic acid supplementation in lactating cow diets was effective at increasing microbial N production and microbial efficiency measured in vitro and milk yield.

Forty-three multiparous Holstein cows were used in a completely randomized design to evaluate the effects of protein supplementation and the use of bovine somatotropin (bST; Posilac, Monsanto Co., St. Louis, MO) in late gestation on animal metabolism and productivity in the periparturient period. Treatments were initiated 28 d prior to expected calving date and continued through parturition. Diets contained either 13.3 or 17.8% crude protein and were formulated to be similar in profile of protein fractions. Within each dietary treatment, cows were assigned to receive either 0 or 500 mg of sustained released bST once every 14 d until parturition. Following parturition, all cows were subjected to the same management and dietary treatments, and production measurements were followed until 42 d in milk. The use of bST increased plasma glucose and decreased plasma nonesterified fatty acids and beta-hydroxybutyrate prior to calving. Despite these changes in metabolism, bST did not affect concentrations of fat and triglyceride in the liver prepartum or postpartum. Feeding the 17.8% protein diet failed to stimulate glucose metabolism and tended to elevate plasma beta-hydroxybutyrate in late gestation. Cows treated with bST produced 3.3 kg/d more milk than did controls across the first 42 d of lactation; the difference was 4.6 kg/d in wk 6 of lactation. The use of bST in late gestation has considerable promise to alter cow metabolism positively. The results of these and other possible periparturient responses to somatotropin may increase milk production in early lactation.

Dairy cattle require fibrous feedstuffs in the diet. However, defining the fiber requirements requires knowledge of many interacting components within the diet as well as how the feed is allocated and processed. To meet the demands of high producing dairy cows for energy, diets consist of large quantities of concentrates and high quality forages containing relatively low amounts of fiber. However, to maintain normal rumen function and milk fat percentage, a large portion of the fiber needs to come from forage. Current National Research Council recommendations are a minimum of 25 to 28% dietary neutral detergent fiber, 75% of which is supplied from forage. Chemical measures of fiber alone are not adequate for ration balancing; fiber varies in its effectiveness at stimulating chewing. This variation is greater when feeds contain high amounts of by-products in place of forages. The effectiveness in stimulation of chewing of fiber is variable as the particle size and retention times of indigestible and digestible fiber vary. Currently, little information exists about the fiber requirements of the cow from immediately postcalving until peak lactation. Early lactation cows are clearly more limited by physical fill than are cows in mid and late lactation. Rations based on nonforage fiber sources (>45% neutral detergent fiber on a dry matter basis) are being evaluated for early lactation cows. Information is needed to determine the variation in the amount of fermentation acids produced, chewing activity, and amount of saliva secreted as these all contribute to the physical effectiveness of fiber.

This experiment evaluated the effect of feeding a lower starch diet (21% of dry matter) with different amounts of forage (52, 47, 43, and 39% of dry matter) on lactational performance, chewing activity, ruminal fermentation and turnover, microbial N yield, and total-tract nutrient digestibility. Dietary forage consisted of a mixture of corn and haycrop silages, and as dietary forage content was reduced, chopped wheat straw (0–10% of dry matter) was added in an effort to maintain chewing activity. Dietary concentrate was adjusted (corn meal, nonforage fiber sources, and protein sources) to maintain similar amounts of starch and other carbohydrate and protein fractions among the diets. Sixteen lactating Holstein cows were used in replicated 4×4 Latin squares with 21-d periods. Dry matter intake increased while physically effective neutral detergent fiber (peNDF 1.18 ) intake was reduced as forage content decreased from 52 to 39%. However, reducing dietary forage did not influence milk yield or composition, although we observed changes in dry matter intake. Time spent chewing, eating, and ruminating (expressed as minutes per day or as minutes per kilogram of NDF intake) were not affected by reducing dietary forage. However, addition of chopped wheat straw to the diets resulted in greater time spent chewing and eating per kilogram of peNDF 1.18 consumed. Reducing dietary forage from 52 to 39% did not affect ruminal pH, ruminal digesta volume and mass, ruminal pool size of NDF or starch, ruminal digesta mat consistency, or microbial N yield. Ruminal acetate-to-propionate ratio was reduced, ruminal turnover rates of NDF and starch were greater, and total-tract digestibility of fiber diminished as dietary forage content decreased. Reducing the dietary forage content from 52 to 39% of dry matter, while increasing wheat straw inclusion to maintain chewing and rumen function, resulted in similar milk yield and composition although feed intake increased. With the lower starch diets in this short-term study, the minimal forage content to maintain lactational performance was between 39 and 43%.

This study evaluated the effect of a blend of synthetic antioxidants on the yield of milk and milk components and milk fatty acid composition in dairy cows fed a diet designed to cause milk fat depression (MFD). We hypothesized that supplementing a synthetic antioxidant to diets with a high rumen unsaturated fatty acid load (RUFAL) would decrease the severity of MFD. Sixteen lactating Holstein cows (163 ± 47 d in milk), in a crossover design with two 21-d periods, were fed a corn silage and grass silage-based diet containing 15% distillers grains. The diet contained 34% neutral detergent fiber, 18% crude protein, 26% starch, and 4.3% total fatty acids (dry matter basis). Cows were fed the diet without supplementation (control; CON) or supplemented with 0.02% (dry matter basis) of a synthetic antioxidant (AOX; Agrado Plus, Novus International Inc., St. Charles, MO). Dry matter intake and milk yields were recorded daily. Milk samples were collected at the start of the study for baseline values and the end of each period (d 20–21) and analyzed for milk components and fatty acid composition. Dry matter intake and milk yield were unaffected by treatment and averaged 25.9 and 50.2 kg/d, respectively. Similarly, we observed no effect of treatment on yields of fat, protein, lactose, 3.5% fat-corrected milk, energy-corrected milk, feed efficiency, body weight, or body condition score. Milk fat concentration and yield were both reduced by the high RUFAL diets. We observed a tendency for AOX to increase the concentration of milk fat and decrease the concentration of milk protein. Yields of de novo and preformed fatty acids were not affected by treatment, although we detected a trend for a slight increase in the yield of 16-carbon fatty acid for AOX compared with CON. Treatment had only minor effects on individual milk fatty acids, except for the concentration and yield of linoleic acid, which were over 90% higher for AOX compared with CON. In conclusion, milk fat concentration and yield were reduced by a high RUFAL diet containing 15% distillers grains; however, supplementation with AOX did not overcome the MFD induced by this diet.

Reduced access to resources because of increased stocking density may have a detrimental effect on the behavior of the lactating dairy cow. The objective of this study was to determine the short-term responses in behavior, productivity, fecal cortisol metabolites, and udder and leg hygiene of lactating Holstein dairy cows housed at stocking densities of 100 (1 cow per freestall and headlock), 113, 131, and 142%. Multiparous cows (n=92) and primiparous cows (n=44) were assigned to 1 of 4 pens (34 cows per pen) in a 4-row freestall barn. Pens were balanced for parity, milk production, and days in milk. Stocking densities were imposed for 14 d using a 4 × 4 Latin square design. Time spent feeding and time spent ruminating were quantified by 24 h of direct observation of focal cows (n=12 per pen) beginning at 0800 h on d 11 of each period. Data loggers recorded lying behavior (time and bouts) from the same focal cows per pen at 1-min intervals during the final 5 d of each period. Fecal cortisol metabolites were quantified from samples collected on d 13 and 14 of each period from the same focal cows. Displacements from the feed barrier were recorded on a pen basis after 9 milkings over the last 4 d of each period. Productivity was assessed on a pen basis from milk yield (recorded from d 10 to 14 of each period) and milk components (quantified from composite samples collected on d 12 of each period). Milk composition was further analyzed for milk fatty acid profiles, which were determined from a subset (n=6 per pen) of the focal cows. Data were analyzed using the MIXED procedure of SAS, with the pen (n=4 per treatment, except displacements where n=3 per treatment) as the experimental unit. Feeding and ruminating (h/d) did not differ among treatments. Lying time was reduced at stocking densities of 131 and 142%, relative to 100 or 113%. Lying bouts were not affected by treatment. Stocking densities of 131 and 142% reduced the percentage of time cows spent ruminating within a freestall relative to 100%. Displacements from the feed bunk increased linearly across treatments. Fecal cortisol metabolites, udder hygiene score, milk yields, milk composition, and milk fatty acids did not differ among treatments. Decreased lying time and increased aggression at the feed bunk suggest that an alteration of the time budgets of lactating dairy cows may occur at higher stocking densities, but it is unclear at what point these changes might have further biological consequences.

The objective of this study was to evaluate the effects of increasing stocking density on indices of cow comfort measured over a 24-h period, during peak lying time (0000 to 0400 h), and 1 h after the afternoon milking. Holstein cows (n = 136) were assigned to 1 of 4 pens, and stocking densities of 100, 113, 131, and 142% were applied in a 4 x 4 Latin square. Video data were recorded continuously for 2 d after 5 d of acclimation to stocking density and analyzed with 10-min scan samples for the percentage of cows lying in a stall, standing in a stall, standing in the alley, and eating at the manger. Percentage of cows standing idly in the alley increased as stocking density increased above 113% (10.9, 12.0, 14.4, and 16.5% for 100, 113, 131, and 142% stocking density, respectively). Cow comfort index (CCI; cows lying down/cows contacting stalls) and stall standing index (SSI; cows standing in stall/cows contacting stalls) differed little as stocking density increased, but stall use index (SUI; cows lying in stall/cows in pen not eating) decreased beyond 113% stocking density (70.1, 70.2, 68.6, and 66.3 for 100, 113, 131, and 142% stocking density, respectively). During peak lying time, SUI decreased with increasing (80.3, 79.5, 74.8, and 69.6 for 100, 113, 131, and 142% stocking density, respectively) stocking density above 113%, whereas CCI and SSI showed little response. None of the indices varied by stocking density when they were assessed at 1 h after milking. These results suggest that more than 1 index of cow comfort may be needed at higher stocking densities to assess both stall usage and cows standing idly in an alley. At higher stocking densities, SUI was reduced, because it reflected not only stall usage but the number of cows standing idly in an alley and not actively feeding and unable to access a stall. The CCI and SSI appear to assess actual stall usage (% cows lying or standing) across the range of stocking densities evaluated in this study.

Total mixed rations containing brown midrib sorghum-sudangrass silage (bmrSS) or corn silage (CS) at either 35 or 45% of dietary dry matter were fed to Holstein dairy cows to determine the effect on lactational performance and nutrient digestibility. Twelve cows were assigned to 1 of 4 diets in replicated 4 x 4 Latin squares with 21-d periods. In vitro 30-h neutral detergent fiber digestion, measured before the start of the trial, was 46.0% for CS and 58.3% for bmrSS. Dry matter intake was greatest when cows were fed the 35% CS (23.4 kg/d) and 45% CS (23.2 kg/d) diets, was least when cows were fed the 45% bmrSS diet (17.6 kg/d), and was intermediate when cows were fed the 35% bmrSS diet (20.1 kg/d). The bmrSS diets resulted in greater body weight gain per 21-d period but similar body condition scores compared with the CS diets. Yield of solids-corrected milk (SCM) was similar among the diets. Efficiency (SCM:dry matter intake) was 28% greater for cows fed the bmrSS than those fed the CS diets. In vivo digestibilities of organic matter and crude protein were greater for the CS diets than the bmrSS diets, but total tract digestibilities of neutral detergent fiber and starch were similar among diets. Ruminal pH was greater when cows were fed the 45% bmrSS diet (6.58), was least when cows were fed the 35% CS (6.10) and 45% CS diets (6.13), and was intermediate when cows were fed the 35% bmrSS diet (6.42). The ratio of acetate to propionate was greater for the bmrSS diets (2.77) than for the CS diets (2.41), with no difference among diets in total volatile fatty acid concentrations (122 mM). In conclusion, cows fed bmrSS had greater efficiency of SCM production, higher ruminal pH, and greater acetate to propionate ratios than cows fed CS. With these diets fed in a short-term study, bmrSS appeared to be an effective alternative to the CS hybrid when fed at either 35 or 45% of dietary dry matter.

Sixty-five multiparous Holstein cows were used to test the effects of feeding diets of varied ruminal carbohydrate availability during the transition period on dry matter intake, blood metabolites, and lactational performance. Cows received total mixed rations containing either cracked corn or steam-flaked corn beginning 28 d prior to expected calving date. At parturition, cows were assigned to a postpartum total mixed ration that contained either cracked corn or steam-flaked corn. Diets were fed until 63 d in milk. No treatment effects on prepartum or postpartum dry matter intake, body weight, and body condition score were observed. Cows fed steam-flaked corn had lower blood urea N concentrations during the prepartum period and lower plasma nonesterified fatty acid concentrations during the prepartum and postpartum periods. Cows fed steam-flaked corn postpartum produced 2.3kg/d more milk than cows fed cracked corn during the first 63 d in milk. Fat corrected milk showed no treatment effect. Seven cows were used to evaluate treatment effects on ruminal fermentation and digesta kinetics. Prepartum and postpartum treatments had minimal effects on ruminal fermentation. Feeding steam-flaked corn prepartum decreased apparent fiber digestibility and ruminal NH 3 N. Feeding steam-flaked corn postpartum decreased the acetate to propionate ratio. Prepartum and postpartum treatments did not affect digesta kinetics. An increase in ruminal carbohydrate availability during the postpartum period enhanced milk production, but had variable results on ruminal fermentation.