Effects of offering free-choice hay for the first 5 days postpartum on productivity, serum inflammatory markers, gut permeability, and colon gene expression in fresh dairy cows.

The objective of the present study was to evaluate the effects of offering free-choice hay to cows during the first 5 d immediately after calving on feed intake, milk yield, plasma metabolites, serum inflammatory markers, rumination, gut permeability, and colon gene expression. It was hypothesized that cows offered free-choice hay would have lower gut permeability, lower inflammation, and higher milk production, compared with cows not offered hay. Thirty-two multiparous cows were fed a closeup total mixed ration (TMR; 21.5% starch, 32.1% forage neutral detergent fiber [NDF] on a dry matter basis) until calving. In the postpartum period, all cows were fed a fresh cow TMR (26.8% starch and 23.4% forage NDF) from calving until 21 DIM, and were assigned randomly to receive 1 of 2 treatments as follows: (1) free-choice timothy hay (61.6% NDF; 9.6% crude protein), offered outside of the TMR in a separate manger, for the first 5 d postpartum (FCH; n = 20), or 2) no free-choice hay (NH; n = 12). The FCH cows tended to have lower serum haptoglobin concentration on d 3, compared with NH (0.95 vs. 1.52 mg/mL). Within the FCH group, cows with greater hay intake had a smaller increase in serum amyloid A from d 1 to 3 after calving (r = 0.37), and tended to have a smaller increase in serum haptoglobin concentration (r = 0.36). Cows in the FCH group had a lower ratio of starch intake (kg) to forage NDF intake (kg) on d 1 and 2, compared with NH (0.91 vs. 1.14 ± 0.03), and cows that had a lower starch:forage NDF ratio tended to have a smaller increase in serum haptoglobin concentration from d 1 to 3 after calving (r = 0.32). Cows in the FCH group had lower TMR dry matter intake (DMI; 15.0 vs. 17.1 ± 0.93 kg/d) and lower total DMI (TMR + hay DMI; 15.9 vs. 17.1 ± 0.87 kg/d), from d 1 to 5 when free-choice hay was offered, compared with NH. However, the hay treatment did not affect plasma energy metabolite concentration, gut permeability, colon gene expression, milk yield, rumination time, or change in body weight or body condition score. Overall, these findings suggest that offering free-choice hay for the first 5 d after calving may reduce serum inflammatory marker concentration, but milk yield may not increase, due to lower intake.

Symposium review: Effects of carbohydrate digestion on feed intake and fuel supply.

Carbohydrates are the primary energy source for lactating dairy cows, and dairy diets are usually formulated for certain concentrations of forage neutral detergent fiber (NDF) and starch due to their direct effects on dry matter intake and milk production. Forage NDF exerts greater filling effects in the rumen than other dietary components and can limit maximum voluntary feed intake of lactating dairy cows. Since an analytical method for NDF was developed more than a half century ago, it has been used widely to characterize forages and diets for dairy cows. However, because NDF is a chemical measurement varying in its digestibility, in vitro digestibility measurements were developed as a biological approach to assess forage quality. Research efforts over the last several decades led to the development of forage cultivars or hybrids with enhanced in vitro NDF digestibility, such as brown midrib, and management practices considering differences in NDF digestibility of forages. In addition, in vitro NDF digestibility and undigested NDF are commonly measured in commercial labs, and estimated rates of digestion are used in dynamic models in an effort to improve the accuracy and precision of diet formulation. Starch digestion in the rumen also varies among starch sources, being affected by grain type, extent of processing, and conservation method. The site and rate of starch digestion affect dry matter intake and nutrient partitioning in dairy cows by modifying temporal supply of fuel. In addition, dietary starch content and its fermentability can affect digestion rates of starch itself and NDF in the rumen. Previous research has increased our understanding of dietary carbohydrates, but its application for diet formulations requires integrated approaches accounting for factors affecting the filling effects of forage NDF, starch digestion, and temporal fuel supply.

Effects of dietary butyrate supplementation and oral nonsteroidal anti-inflammatory drug administration on serum inflammatory markers and productivity of dairy cows during the calving transition.

Dairy cattle experience inflammation during the calving transition period, and butyrate and nonsteroidal anti-inflammatory drugs (NSAID) are expected to reduce the inflammation. Our objective was to evaluate the effects of dietary butyrate supplementation and oral NSAID administration on feed intake, serum inflammatory markers, plasma metabolites, and milk production of dairy cows during the calving transition period. Eighty-three Holstein cows were used in the experiment with a 2 × 2 factorial arrangement of treatments. The cows were blocked by parity and calving date, and randomly assigned to a dietary butyrate or control supplement, and NSAID or a placebo oral administration. Experimental diets were iso-energetic containing calcium butyrate at 1.42% of diet dry matter (DM) or the control supplement (1.04% commercial fat supplement and 0.38% calcium carbonate of diet DM). The close-up diets contained 13.3% starch and 42.4% neutral detergent fiber on a DM basis, and were fed from 28 d before expected calving date until calving. The postpartum diets contained 22.1% starch and 34.1% neutral detergent fiber on a DM basis and were fed from calving to 24 d after calving. Oral NSAID (1 mg of meloxicam/kg of body weight) or placebo (food dye) was administered 12 to 24 h after calving. Dietary butyrate supplementation and oral NSAID administration did not affect milk yield or postpartum serum concentrations of amyloid A and haptoglobin. However, butyrate-fed cows increased plasma fatty acid concentration on d -4 relative to calving (501 vs. 340 µEq/L) and tended to increase serum haptoglobin concentration (0.23 vs. 0.10 mg/mL). There was a supplement by drug interaction effect on plasma glucose concentration on d 4; in cows administered the placebo drug, butyrate supplementation decreased plasma glucose concentration compared with control-fed cows (62.8 vs. 70.1 mg/dL). Butyrate-fed cows tended to have lower milk crude protein yield compared with cows fed the control diet (1.21 vs. 1.27 kg/d). Dietary butyrate supplementation and oral NSAID administration did not have overall positive effects on production performance of dairy cows during the calving transition period.

Repeatability of anogenital distance measurements from birth to maturity and at different physiological states in female Holstein cattle.

The inverse association between anogenital distance (AGD; the distance from the center of the anus to the base of the clitoris) and fertility, its moderate heritability, and high variability reported in dairy cattle make AGD a promising candidate for further exploration as a reproductive phenotype. In addition to heritability, repeatability (i.e., consistency in measurements taken at different time points) is important for a reproductive phenotype to be considered useful in genetic selection. Therefore, our primary objective was to determine the repeatability of AGD from birth to breeding age (≈16 mo) in Holstein heifer calves, and during different stages of the estrous cycle, gestation, and lactation in Holstein cows. We also determined the associations among AGD, height (at the hip), and body weight (BW) at birth. In calves (n = 48), we recorded BW (kg) and height (cm) at birth and measured AGD (mm) at approximately 0, 2, 6, 9, 12, and 16 mo of age. In cows, AGD was measured at different stages of the estrous cycle (proestrus, estrus, metestrus and diestrus; n = 20), gestation (30, 90, 180, and 270 d; n = 78), and lactation (30-300 d in milk in 30-d increments; n = 30). Calf height and BW at birth had a weak positive association with AGD at birth. The AGD increased linearly from birth to breeding age, but there was no association between the AGD at birth and at breeding age in heifers. Although any 2 consecutive AGD measurements were correlated, 6 mo was the earliest age at which AGD was moderately correlated (r = 0.41) with that of breeding-age heifers. The AGD was neither influenced by the different stages of estrous cycle nor lactation and remained highly repeatable (r ≥ 0.95). Although AGD measurements at 30, 90, and 180 d of gestation (126.9, 126.7, and 127.7 mm, respectively) were strongly correlated (r ≥ 0.97) with each other, AGD at 270 d of gestation (142.8 mm) differed from AGD at all earlier stages of gestation. In summary, AGD measured at birth did not reflect AGD at breeding age in heifers, but AGD measurements in cows had high repeatability at all stages of the estrous cycle, gestation, and lactation, except at 270 d of gestation. Therefore, AGD could be measured reliably at any of the aforesaid physiological states in cows due to its high repeatability, except during late gestation. The earliest gestational stage when pregnancy-associated increase in AGD occurred, however, could not be definitively established in the present study.

Effects of rumen-protected glutamate supplementation during the periparturient period on digestibility, inflammation, metabolic responses, and performance in dairy cows.

The objective of this study was to evaluate the effects of feeding rumen-protected glutamate during the periparturient period (d -21 ± 3 to d 21 ± 3 relative to calving) on apparent total-tract digestibility (ATTD), inflammation, metabolic responses, and production performance of dairy cows. Fifty-two multiparous Holstein cows were blocked by parity, body condition score, and expected calving date, and randomly assigned to one of the experimental diets with rumen-protected monosodium glutamate (RP-Glu; intestinally available Glu = 8.8%) or without RP-Glu (control) at d -21 ± 3 relative to expected calving date. The RP-Glu was fed at 4% and 3% of dietary dry matter, before and after calving, respectively. Prepartum diets contained 17.1% and 16.5% crude protein, and 13.1% and 13.3% starch, and postpartum diets contained 18.8% and 18.3% crude protein, and 22.5% and 22.7% starch on a dry matter basis, respectively for RP-Glu and control treatments. A subset of 19 cows was used to measure ATTD. Cows fed the RP-Glu had greater ATTD of dry matter (70.6 vs. 69.1%), crude protein (75.1 vs. 72.6%), and ether extract (66.0 vs 61.2%) on d 5 ± 1 after calving. Cows fed the RP-Glu also had greater dry matter intake (15.7 vs. 13.7 kg/d) on d 1 after calving. Cows fed the RP-Glu had greater plasma concentrations of Glu (4.60 vs. 3.89 µmol/dL) and insulin-like growth factor-1 (44.2 vs. 30.1 mg/mL), lower serum concentrations of free fatty acids (670 vs. 981 µEq/L) and total bilirubin (0.22 vs. 0.34 mg/dL), and lower plasma 3-methylhistidine concentration (1.28 vs. 1.50 µmol/dL) on d 4 after calving. However, these treatment effects observed between d 1 and d 5 ± 1 immediately after calving did not continue until d 21 after calving. Concentrations of serum amyloid A, serum haptoglobin, and plasma lipopolysaccharide binding protein were not affected by the treatment. In addition, no differences were observed for serum ß-hydroxybutyrate concentration and milk yield during the postpartum period between the 2 groups, and cows fed the RP-Glu had a decreased lactose yield. These findings suggest that feeding RP-Glu during the periparturient period can increase digestive capacity and feed intake, and decrease mobilization of body fat and protein immediately after calving without increasing milk production.

Associations between anogenital distance and measures of fertility in lactating North American Holstein cows: A validation study.

Anogenital distance (AGD) has been defined in dairy cows as the distance from the center of the anus to the base of the clitoris. Initial reports on nulliparous Holstein heifers and first- and second-parity Holstein cows have found inverse relationships between AGD and measures of fertility. Our primary objective was to determine the relationship between AGD and measures of fertility in a larger population of North American Holstein cows to validate our previous finding that AGD is inversely related to fertility. Secondary objectives were to determine the associations between AGD and parity, and milk yield. Using digital calipers, we measured AGD in 4,709 Holstein cows [mean ± standard deviation (SD); parity 2.3 ± 1.4; days in milk (DIM) 154 ± 94; 305-d mature equivalent (ME) milk yield 13,759 ± 2,188 kg] from 18 herds in Western Canada and 1 herd in the USA. Anogenital distance (mm) was normally distributed with a mean (±SD) of 132 ± 12, ranging from 95 to 177, and a median of 133. Anogenital distance was linearly but inversely associated with pregnancy to first artificial insemination (P/AI1). For every 1-mm increase in AGD, the estimated probability of P/AI1 decreased by 0.8%. The optimum AGD cut-point that predicted probability of P/AI1 with sensitivity and specificity of 45 and 55%, respectively, was 129 mm. Consequently, data were categorized into either short (≤129) or long (>129) AGD groups across parities, and associations between AGD, parity (first, second, and third+), and fertility measures were determined. Rates of P/AI1 were greater (36 vs. 30%) in short- than in long-AGD cows; short-AGD cows required fewer AI per conception (2.3 vs. 2.4) and had fewer days open (137 vs. 142), and a greater proportion of short-AGD cows (67 vs. 64%) was pregnant by 150 DIM compared with long-AGD cows. The rates of pregnancy up to 150 (hazard ratio of 0.91) and 250 DIM (hazard ratio of 0.93) were smaller in long- than in short-AGD cows. Anogenital distance had a weak positive association with both parity (r = 0.22) and 305-d ME milk yield (r = 0.04). Results indicate an inverse relationship between AGD and measures of fertility in lactating cows, validating our earlier report. We infer that although selecting cows for short AGD is expected to have an adverse effect on milk yield, the anticipated gain in fertility will outweigh the small decline in milk yield, strengthening the potential of AGD as a novel reproductive phenotype for use in future breeding programs to improve fertility.

Effects of pre- and postpartum dietary starch content on productivity, plasma energy metabolites, and serum inflammation indicators of dairy cows.

The objective of this study was to evaluate the effects of the starch content of pre- and postpartum diets on productivity, plasma energy metabolites, and serum markers of inflammation of dairy cows during the calving transition period. Eighty-eight primiparous and multiparous cows were randomly assigned to pre- and postpartum dietary treatments balanced for parity and pretrial body condition score at d 28 ± 3 before expected calving date. Cows were fed either a control [Control; 14.0% starch, dry matter (DM) basis] or high-starch (High; 26.1% starch, DM basis) prepartum diet commencing 28 ± 3 d before expected calving date. Following calving, cows were fed either a high-fiber (HF; 33.8% neutral detergent fiber, 25.1% starch, DM basis) or high-starch (HS; 27.2% neutral detergent fiber, 32.8% starch, DM basis) postpartum diet for the first 20 ± 2 d following calving. Cows fed the High prepartum diet had greater DM intake (12.4 vs. 10.2 kg/d), plasma concentrations of insulin (1.72 vs. 14.2 ng/mL), glucose (68.1 vs. 65.0 mg/dL), and glucagon-like peptide-2 (0.41 vs. 0.32 ng/mL) before parturition, but increased plasma free fatty acid concentration (452 vs. 363 µEq/L) and milk fat yield (1.64 vs. 1.48 kg/d) after parturition. Cows fed the HS postpartum diet had lower plasma free fatty acid (372 vs. 442 µEq/L) and serum haptoglobin (0.46 vs. 0.70 mg/mL) concentrations over a 3-wk period after calving. In addition, there was a tendency for interaction between prepartum and postpartum diets for milk yield, where feeding the HS postpartum diet increased milk yield compared with the HF diet for cows fed the Control prepartum diet (40.8 vs. 37.9 kg/d) but not for cows fed the High prepartum diet. These results suggest that management efforts to minimize the change in diet fermentability during the calving transition by feeding the High prepartum diet, the HF postpartum diet, or both did not increase productivity of dairy cows but increased fat mobilization after calving. Our findings also suggest that feeding high-starch postpartum diets can decrease fat mobilization and serum indicators of systemic inflammation and increase milk production even with the transition from a low-starch prepartum diet.

Relationship of anogenital distance with fertility in nulliparous Holstein heifers.

Anogenital distance (AGD), defined as the distance from the center of the anus to the base of the clitoris, in lactating dairy cows of first and second parity, has been reported to be inversely related to fertility and moderately heritable. Thus, AGD may be a useful reproductive phenotype for future genetic selection to improve fertility. The objectives of this study were to (1) characterize AGD in nulliparous dairy heifers; and (2) determine if the inverse relationship between AGD and fertility, found in lactating dairy cows, is also evident in nulliparous heifers. We measured AGD in 1,692 Holstein heifers from 16 herds in Western Canada (Alberta and British Columbia) and one herd in the United States (Washington State). Data were analyzed using MEANS, UNIVARIATE, LOGISTIC, ROC, GLIMMIX, and LIFETEST procedures of SAS (SAS Institute Inc.). Mean (±standard deviation) age at AGD measurement was 13.9 ± 1.5 mo, and AGD was normally distributed with a mean of 107.3 ± 10.5 mm, ranging from 69 to 142 mm. With every 1-mm increase in AGD, the predicted probability of pregnancy was reduced by 1.9%. Receiver operating characteristic curve analysis was used to determine the optimum threshold AGD that predicted the probability of pregnancy. Based on the optimum threshold AGD, data from heifers were categorized into short (≤110 mm) and long (>110 mm) AGD groups, and associations between AGD groups and fertility measures were determined. Heifers with short AGD required fewer services per conception (1.5 vs. 1.7) than heifers with long AGD. Consequently, heifers with short AGD conceived earlier (448.4 vs. 454.3 d) and had greater pregnancy to first AI than those with long AGD (58.3 vs. 49.6%). Moreover, heifers with long AGD had reduced hazard (hazard ratio of 0.59) for pregnancy up to 450 d of life compared with those with short AGD. In summary, AGD was normally distributed and highly variable in the population. In addition, an inverse relationship between AGD and fertility measures in nulliparous heifers was evident, confirming an earlier report of a similar relationship in lactating dairy cows. These findings strengthen the potential for AGD to be used as a fertility trait and management tool in future selection programs.

Rumen microbiota and its relation to fermentation in lactose-fed calves.

In our previous studies, we revealed the effect of lactose inclusion in calf starters on the growth performance and gut development of calves. We conducted the present study as a follow-up study to identify the shift in rumen microbiota and its relation to rumen fermentation when calves are fed a lactose-containing starter. Thirty Holstein bull calves were divided into 2 calf starter treatment groups: texturized calf starter (i.e., control; n = 15) or calf starter in which starch was replaced with lactose at 10% (i.e., LAC10; n = 15) on a dry matter basis. All calves were fed their respective treatment calf starter ad libitum from d 7, and kleingrass hay from d 35. Rumen digesta were collected on d 80 (i.e., 3 wk after weaning) and used to analyze rumen microbiota and fermentation products. There was no apparent effect of lactose feeding on the α-diversity and overall composition of rumen microbiota. Amplicon sequencing and real-time PCR quantification of the 16S rRNA gene confirmed that the abundance of butyrate-producing bacteria (i.e., Butyrivibrio group and Megasphaera elsdenii) did not differ between the control and LAC10 groups. Conversely, the relative abundance of Mitsuokella spp., which produce lactate, succinate, and acetate, was significantly higher in the rumen of calves that were fed lactose, whereas the lactate concentration did not differ between the control and LAC10 groups. These findings suggest that the lactate production can be elevated by an increase of Mitsuokella spp. and then converted into butyrate, not propionate, since the proportion of propionate was lower in lactose-fed calves. In addition, we observed a higher abundance of Coriobacteriaceae and Pseudoramibacter-Eubacterium in the LAC10 group. Both these bacterial taxa include acetate-producing bacteria, and a positive correlation between the acetate-to-propionate ratio and the abundance of Pseudoramibacter-Eubacterium was observed. Therefore, the higher abundance of Coriobacteriaceae, Mitsuokella spp., and Pseudoramibacter-Eubacterium in the rumen of lactose-fed calves partially explains the increase in the proportion of rumen acetate that was observed in our previous study.

The effects of feeding a high-fiber or high-starch pellet at two daily allocations on feed intake patterns, rumen fermentation, and milk production of mid-lactation dairy cows.

The objective of this experiment was to determine the effect of pellet type and feeding amount on feeding behavior, dry matter intake, rumen fermentation, and milk production of lactating dairy cows. An experimental diet was formulated to provide an adequate amount of nutrients to a 650-kg cow producing 40 kg of milk per day, with a portion of the diet removed as a high-fiber (33.2% neutral detergent fiber; F) or high-starch (56.8% starch; S) pellet. Pellets were fed at a low (1 kg; L) or high (3 kg; H) amount twice per day alongside a partial mixed ration (PMR). Four complementary PMR were formulated for each pellet treatment such that the overall diet (pellet + PMR) offered to the cows was the same among all treatments. Eight ruminally cannulated cows were used in a 4 × 4 Latin square design with 14-d periods. Cows were fed PMR once daily at 1200 h, and pellet twice daily at 0600 and 1800 h. Data and samples were collected on d 11 to 14 of each period. By design there was a difference in pellet intake between the H and L treatments (5.31 vs. 1.81 kg/d), and PMR intake was reduced when H pellet was fed (22.9 vs. 25.3 kg/d); however, feeding H tended to increase total dry matter intake. Feed disappearance, which was measured as the amount of PMR consumed every 3 h following PMR delivery, was affected by the nutrient composition of the PMR as cows fed S (with high-fiber PMR) consumed 28.6% of their PMR intake within 3 h of delivery, whereas cows fed F (with high-starch PMR) consumed 33.5%. Duration that pH was below 5.8 tended to be lower when cows were fed the S pellet (270 vs. 125 min/d) compared with F. In addition, feeding the S pellet (with high-fiber PMR) decreased plasma concentrations of glucose (66.0 vs. 70.0 mg/dL) and insulin (1.90 vs. 2.25 ng/mL) compared with F. These results suggest that the composition of the PMR dictates rumen fermentation to a greater extent than composition of pellets. The S pellet was fed alongside a high-fiber PMR, which was more filling in the rumen, less fermentable, and contained more neutral detergent fiber. Although no difference was observed in milk production among treatments, the fact that feed intake pattern and rumen fermentation are better explained by nutrient composition of the PMR should be considered when formulating diets for lactating cows fed pellet and PMR, such as those milked with automated milking systems.

Effects of feeding hay and calf starter as a mixture or as separate components to Holstein calves on intake, growth, and blood metabolite and hormone concentrations.

This study investigated how providing hay mixed with calf starter to dairy calves affected their solid feed intake, feed sorting, growth, and plasma metabolite and hormone concentrations. Forty Holstein heifer calves were fed a texturized calf starter (23.4% crude protein, 32.3% starch on a dry matter basis) and chopped Klein grass hay as separate components (CONT) or the same starter and hay mixed at a 90:10 ratio on an as-fed basis (MIX) ad libitum from the date transported to the research farm (4-7 d of life) to 90 d of life. Calves were provided milk replacer (28% crude protein, 15% fat) at up to 557 g/d before the study, 737 g/d from d 14 to 20, 1,105 g/d from d 21 to 41, 737 g/d from d 42 to 48, and 557 g/d from d 49 to 55 on a dry matter basis. calves were fully weaned on d 56. Feed sorting for the MIX calves was evaluated using the Penn State Particle Separator; the sorting index was calculated as the actual intake as a percentage of predicted intake, with values >100% indicating sorting for and values <100% indicating sorting against. Treatment did not affect solid feed intake, growth performance, or plasma metabolite or hormone concentration during the preweaning or weaning periods. However, calves in the MIX treatment had less neutral detergent fiber intake as a percentage of solid feed intake than CONT calves in the preweaning (23.3 vs. 37.0%) and weaning (23.5 vs. 25.8%) periods, although MIX calves sorted (107.2%) for long particles, which were primarily hay, during weaning. During the postweaning period, MIX calves had greater neutral detergent fiber intake as a percentage of solid feed intake compared with CONT calves (23.4 vs. 22.7%), although they sorted against long particles (84.4%), and decreased solid feed dry matter intake compared with CONT calves (3,292 vs. 3,536 g/d) and average daily gain (1.20 vs. 1.31 kg/d). Weaned calves in the MIX treatment also had lower plasma concentration of glucagon-like peptide 2 compared with CONT (0.46 vs. 0.77 ng/mg) but had higher plasma concentrations of ghrelin (0.05 vs. 0.03 ng/mg). These results suggest that feeding a mixture of texturized calf starter and chopped hay at the 90:10 ratio to postweaned calves may decrease solid feed intake and growth.

Effects of starch concentration of close-up diets on rumen pH and plasma metabolite responses of dairy cows to grain challenges after calving.

The objective of this study was to evaluate the effects of starch concentration of close-up diets on plasma concentrations of energy metabolites and rumen pH of dairy cows after calving. Eighteen multiparous Holstein dairy cows (mean parity = 2.78; mean body weight = 708 kg; mean body condition score = 3.08) fitted with ruminal cannulas were assigned to treatment balanced for parity, body condition score, and expected calving date. Cows were enrolled in the study at d 28 ± 3 before the expected calving date and fed either a low-starch (LS; 14.0% starch) or high-starch (HS; 26.1% starch) diet until parturition. All cows were fed a common diet after calving (25.1% starch). A grain challenge was performed on d 7 ± 2 and 21 ± 2 after calving by dosing 6.35 kg (dry matter basis) of finely ground barley and wheat grain (1:1) into the rumen via cannula. Feeding the HS diet before calving increased the duration (369 vs. 49 min/d) and area of pH below 5.8 (85.1 vs. 5.2 pH × min/d) during d -10 to -8. In addition, even though all cows were fed a common diet after calving, HS cows tended to have longer duration (177 vs. 76 min/6 h) and greater area of pH below 5.8 (67.8 vs. 20.3 pH × min/6 h) during a grain challenge on d 7. Plasma concentration of insulin tended to be greater in cows fed the HS diet (1.40 vs. 1.09 ng/mL), whereas plasma free fatty acid concentration was not different between treatments during the grain challenge on d 7. During the grain challenge on d 21, neither rumen pH nor blood metabolites were different between the HS and LS cows. These findings suggested that feeding an HS diet during the close-up period does not mitigate rumen pH depression but may exacerbate it after calving compared with feeding an LS diet.

Effects of butyrate supplementation on blood glucagon-like peptide-2 concentration and gastrointestinal functions of lactating dairy cows fed diets differing in starch content.

The objective of this study was to evaluate effects of butyrate supplementation on plasma concentration of glucagon-like peptide-2 (GLP-2), apparent total-tract digestibility, and responses to a grain challenge of lactating dairy cows fed diets differing in starch content. Eight Holstein cows averaging 58.6 ± 9.96 d in milk (4 primiparous cows fitted with rumen cannula and 4 multiparous intact cows) were blocked by parity and assigned to one of two 4 × 4 Latin squares balanced for carryover effects with a 2 × 2 factorial arrangement of treatments. Treatments were dietary starch content [20.6 vs. 27.5%, respectively, for low starch (LS) and high starch (HS)] and butyrate supplementation (butyrate vs. control) with 21-d periods. Butyrate was provided as Gustor BP70 WS (Norel, S.A., Madrid, Spain), containing 70% sodium butyrate and 30% fatty acid mixture, at 2% of dietary dry matter (providing butyrate at 1.1% of dietary dry matter), and control premix contained 70% wheat bran and 30% fatty acid mixture. Feeds, orts, and fecal samples were collected from d 17 to 19 to determine apparent total-tract nutrient digestibility. Blood and rumen fluid samples were collected on d 19. The baseline of dry matter intake (DMI) was determined as average DMI from d 17 to 19 for each cow, and cows were feed-restricted at 60% of the baseline DMI on d 20, and a grain challenge was conducted by providing steam-flaked corn grain at 0.6% of body weight, on an as-fed basis, in addition to each treatment diet on d 21, and blood and ruminal fluid samples were collected. The interaction of dietary starch content by butyrate supplementation was significant for plasma GLP-2 concentration, being greater for cows fed butyrate with the HS diet than those fed the other 3 diets. Cows fed butyrate increased n-butyrate concentration in the ruminal fluid and tended to increase dry matter and organic matter digestibility compared with the control. During the grain challenge, rumen endotoxin concentration increased over time and was higher for cows fed the HS diets compared with those fed LS diets. However, response variables related to inflammation were not affected by the grain challenge. However, serum haptoglobin, lipopolysaccharide-binding protein, and serum amyloid-A concentrations were greater for cows fed butyrate with the LS diet, but not for those fed the HS diet. These results indicate that butyrate supplementation may increase plasma GLP-2 concentration for cows fed HS diets, and total-tract digestibility regardless of dietary starch content. However, butyrate supplementation did not mitigate inflammation in this study.

Effects of supplementing a Saccharomyces cerevisiae fermentation product during the transition period on rumen fermentation of dairy cows fed fresh diets differing in starch content.

The objective of this study was to evaluate the effects of supplementing a Saccharomyces cerevisiae fermentation product (SCFP; NutriTek, Diamond V, Cedar Rapids, IA) during the transition period (d -28 ± 3 to 23 ± 3 relative to calving) on rumen fermentation and mRNA abundance of genes in the rumen epithelium of fresh cows (d 1 to 23 ± 3 after calving) fed diets differing in starch content. Eighteen ruminally cannulated multiparous Holstein cows were fed diets with SCFP (n = 9) or without (CON; n = 9) throughout the experiment. All cows were fed a common basal controlled-energy close-up diet (1.43 Mcal/kg, net energy for lactation; 13.8% starch) before calving. Cows within each treatment (CON or SCFP) were fed either a low-starch (LS; 22.1% starch) or high-starch (HS; 28.3% starch) diet during the fresh period. Cows were assigned to treatment after balancing for parity, body condition score, and expected calving date. Rumen pH was measured continuously for 72 h starting on d -10, -3, 1, 7, and 21 relative to calving date. Rumen papillae were collected on d -10 and 21 relative to calving. Supplementation of SCFP had no effect on rumen pH during d -10 to -8, but mean rumen pH tended to be higher (6.64 vs. 6.49) for SCFP cows than for CON cows during d -3 to -1. Feeding SCFP decreased the range of rumen pH variation compared with CON within the HS group during both d 7 to 9 (1.08 vs. 1.38) and d 21 to 23 (1.03 vs. 1.30) after calving. In addition, nadir rumen pH tended to be higher (5.64 vs. 5.44) and duration of pH below 5.8 tended to be shorter (116 vs. 323 min/d) for the SCFP group than for the CON group during d 21 to 23 after calving. Supplementation of SCFP increased the mRNA abundance of insulin-like growth factor-6 (1.10 vs. 0.69) before calving and decreased the mRNA abundance of putative anion transporter isoform 1 (1.12 vs. 2.27) after calving. Nadir rumen pH tended to be higher during d 1 to 3 (5.63 vs. 5.41) for LS cows than for HS cows, but rumen pH was not affected by dietary starch content during other time periods. Dietary starch content had no effect on mRNA abundance of genes in the rumen epithelium after calving. These results suggest that supplementation of SCFP may reduce the range of variation in rumen pH in fresh cows fed HS diets and the duration of subacute ruminal acidosis by the end of the fresh period regardless of dietary starch content and that decreasing dietary starch content during the fresh period may reduce the decrease in rumen pH immediately after parturition.

Short communication: Effects of butyrate supplementation on the productivity of lactating dairy cows fed diets differing in starch content.

The objective of this study was to evaluate the effects of butyrate supplementation on the dry matter intake (DMI), milk production, and blood metabolites of lactating dairy cows fed diets differing in starch content. Eight Holstein cows after peak lactation (58.6 ± 9.96 d in milk; mean ± SD) were blocked by parity and assigned to 1 of 2 Latin squares (4 × 4) balanced for carryover effects with a 2 × 2 factorial arrangement of treatments. Treatments differed by dietary starch content (20.6 vs. 27.5%) and butyrate supplementation (butyrate vs. control) with 21-d periods. Experimental diets contained 36 and 30% corn silage, 18 and 15% grass silage, and 46 and 55% concentrates, respectively, for low starch and high starch diets, on a dry matter (DM) basis. Butyrate was provided as Gustor BP70 WS (Norel S.A., Madrid, Spain), containing 70% sodium butyrate and 30% fatty acid mixture, at 2% of dietary DM (providing butyrate at 1.1% of dietary DM), and control premix contained 70% wheat bran and 30% fatty acid mixture. Interaction effects between dietary starch content and butyrate supplementation were not observed for primary response variables, and milk yield was not affected by treatment. Butyrate supplementation increased serum ß-hydroxybutyrate concentration compared with control (0.706 vs. 0.930 mM), but did not exceed 1.2 mM, a commonly accepted value for subclinical ketosis, and DMI was not affected. Cows fed butyrate had increased milk fat content (4.58 vs. 4.37%) and milk fat yield (1.51 vs. 1.42 kg/d), tended to have increased 4% fat-corrected milk yield (35.9 vs. 34.3 kg/d) and feed efficiency (1.56 vs. 1.50; 4% fat-corrected milk yield/DMI), and had decreased milk urea nitrogen (MUN) concentration (10.8 vs. 11.7 mg/dL) compared with control. Cows fed high starch diets tended to have increased DMI (23.3 vs. 22.5 kg/d), increased milk protein yield (1.13 vs. 1.05 kg/d), and decreased MUN concentration (10.3 vs. 12.2 mg/dL). Inclusion of butyrate at 1.1% of dietary DM increased milk fat production and decreased MUN concentration without affecting DMI or increasing the risk of subclinical ketosis, regardless of dietary starch content.

Effects of supplementing a Saccharomyces cerevisiae fermentation product during the periparturient period on the immune response of dairy cows fed fresh diets differing in starch content.

The objective of this study was to evaluate the effects of supplementing a Saccharomyces cerevisiae fermentation product (SCFP; NutriTek, Diamond V, Cedar Rapids, IA) during the periparturient period (d -28 ± 3 to 44 ± 3 relative to calving) on mRNA abundance of genes in the rumen epithelium, inflammation indicators, oxidative status, and adaptive immunity of dairy cows fed diets with different starch content after calving. From d 28 ± 3 (± standard deviation) before the expected calving date to calving, Holstein cows (n = 38) received a common basal controlled-energy close-up diet (1.43 Mcal/kg, net energy for lactation; 13.8% starch) with (SCFP; n = 19) or without (CON; n = 19) SCFP, and cows within each treatment (CON or SCFP) were fed either a low- (LS; 22.1% starch) or high-starch (HS; 28.3% starch) diet from d 1 to 23 ± 3 after calving (fresh period). There were 4 treatment groups: LS + CON (n = 9), LS + SCFP (n = 10), HS + CON (n = 10), and HS + SCFP (n = 9). From d 24 ± 3 to 44 ± 3 after calving, all cows were fed the HS diets (post-fresh period). Animal assignment to treatments was balanced for parity, body condition score, and expected calving date. An interaction was observed between dietary starch content and SCFP on indices of oxidative stress; plasma concentrations of total antioxidant capacity tended to be reduced on d 21 after calving for SCFP compared with CON cows when a LS fresh diet was fed, but did not differ for cows fed HS fresh diets. Regardless of starch content, SCFP supplementation increased plasma concentrations of malondialdehyde at d 21 after calving compared with CON. Supplementing with SCFP reduced serum concentrations of haptoglobin on d 7 after calving, indicating reduced inflammation, and feeding LS fresh diets reduced mRNA abundance of IL receptor associated kinase-1 in rumen tissue at d 21 after calving, suggesting reduced immune activation in rumen tissue. Other than the anti-inflammatory effects indicated by lower serum haptoglobin concentration, no other effects of treatment on adaptive immunity were detectable. These results indicate that supplementing SCFP through the transition period and feeding low-starch diets during the fresh period may reduce inflammation.

Effects of feeding a high- or moderate-starch prepartum diet to cows on newborn dairy heifer calf responses to intravenous glucose tolerance tests early in life.

The objective of this study was to evaluate the effect of feeding a prepartum diet with a high or moderate starch content on growth and insulin sensitivity of female offspring early in life. Thirty-eight Holstein heifer calves were born to dams fed either a high-starch (26% starch on a DM basis, HI; n = 20) or moderate-starch (14% starch on a DM basis, MOD; n = 18) prepartum diet commencing at 28 ± 3 d before expected parturition date. Following birth, all calves were housed individually and fed three 2-L meals of colostrum within the first 24 h of life and offered 10 L/d of milk replacer (26% CP, 18% fat, mixed to 130 g/L). Body weight of calves was measured at birth and on d 2 (after colostrum feeding but before milk feeding), 10 ± 2, and 20 ± 2. A glucose tolerance test was performed at a minimum of 6 h after their last colostrum or milk meal to evaluate insulin sensitivity on d 2, 10 ± 2 and 20 ± 2. Body weight did not differ throughout between HI and MOD calves; however, calves born to primiparous dams were smaller compared with those born to multiparous dams. Glucose or insulin concentrations were not different before the glucose tolerance test. Following the glucose tolerance test, maximum glucose concentrations were not different between treatments at any time point. However, HI calves had greater insulin area under the curve, and HI calves had greater maximum insulin concentrations on d 2. Glucose or insulin clearance rates were not different nor was the calculated insulin sensitivity index between treatments. These findings suggest that feeding a HI prepartum diet may reduce some insulin sensitivity indicators of female offspring early in life.

Effects of supplementing a Saccharomyces cerevisiae fermentation product during the periparturient period on performance of dairy cows fed fresh diets differing in starch content.

The objective of this study was to evaluate the effects of supplementing a Saccharomyces cerevisiae fermentation product (SCFP; NutriTek, Diamond V, Cedar Rapids, IA) during the periparturient period (d -28 ± 3 to 44 ± 3 relative to calving) on dry matter intake (DMI), milk production, apparent total-tract nutrient digestibility, and postpartum ovarian activity of dairy cows fed fresh diets varying in starch content. From d 28 ± 3 before the expected calving date until d 44 ± 3 after calving, 117 Holstein cows were fed diets with SCFP (SCFP; n = 59) or without (control, CON; n = 58). A common, basal, controlled-energy close-up diet (net energy for lactation: 1.43 Mcal/kg; 13.8% starch) was fed before calving. Cows within each treatment (CON or SCFP) were fed either a low- (LS; 22.1% starch) or high-starch (HS; 28.3% starch) diet from d 1 to 23 ± 3 after calving (fresh period), resulting in 4 treatment groups: LS-CON (n = 30), LS-SCFP (n = 29), HS-CON (n = 28), and HS-SCFP (n = 30). All cows were fed the HS diets from d 24 ± 3 to 44 ± 3 after calving (post-fresh period). Cows were assigned to treatment balanced for parity, body condition score, body weight, and expected calving date. Milk yield was higher for cows fed the LS diets compared with those fed the HS diets during the fresh period (34.1 vs. 32.1 kg/d), whereas DMI and 3.5% fat-corrected milk yield (FCM) were not affected by dietary starch content, and LS cows tended to lose more body condition than HS cows (-0.42 vs. -0.35 per 21 d) during the fresh period. Overall DMI during the close-up and fresh periods did not differ between SCFP and CON cows. However, SCFP supplementation transiently increased DMI on d 1 (13.0 vs. 11.9 kg/d) and 5 (15.5 vs. 14.1 kg/d) after calving compared with CON. During the post-fresh period, SCFP cows tended to eat less than CON cows (19.8 vs. 20.6 kg/d) but had similar 3.5% FCM (44.9 vs. 43.6 kg/d), resulting in greater feed efficiency for SCFP cows (FCM/DMI; 2.27 vs. 2.13). Neither starch content of fresh diets nor SCFP supplementation affected the interval from calving to first ovulation or the incidence of double ovulation. These findings suggest that feeding low-starch diets during the fresh period can increase milk production of dairy cows during the fresh period, and that supplementation of SCFP may increase feed intake around calving and feed efficiency in the post-fresh period.

Short communication: Effects of feeding purple corn (Zea mays L.) silage on productivity and blood superoxide dismutase concentration in lactating cows.

The objective of this study was to evaluate the effects of feeding purple corn (Zea mays L.) silage on productivity and blood superoxide dismutase concentration in lactating cows. We hypothesized that feeding purple corn silage (AX-152; Nagano Animal Industry Experiment Station, Nagano, Japan, and Takii and Co. Ltd., Tokyo, Japan), which is high in anthocyanin content, would increase milk production and blood concentration of superoxide dismutase. We assigned 16 Holstein cows (8 primiparous and 8 multiparous) in mid lactation to 1 of 2 treatments in a randomized block design, with efforts to balance parity, body weight, and days in milk between treatments. Experimental diets contained either purple corn silage [PCS; 31.2% dry matter (DM), 8.4% crude protein, 40.2% neutral detergent fiber, and 26.6% starch] or conventional corn silage (CONT; 30.5% dry matter, 8.7% crude protein, 42.1% neutral detergent fiber, and 26.5% starch) at approximately 32% of diet DM. Both PCS and CONT were ensiled for 5 mo before the study. Treatment diets were fed as total mixed rations ad libitum for 12 wk from February 1 to April 25, 2016. Cows fed the PCS had increased milk yield (31.7 vs. 29.2 kg/d) and blood superoxide dismutase concentrations (9,333 vs. 8,467 U/mL) compared with those fed CONT. However, anthocyanin concentration in the PCS decreased over the 12-wk experiment: 70 mg/kg of DM for the first 4 wk, 20 mg/kg of DM for the second 4 wk, and undetectable for the last 4 wk. We did not detect anthocyanins in the CONT group at any time point. Feeding PCS may increase antioxidant capacity and milk production in dairy cows, but anthocyanin in PCS may be degraded during storage.

The effects of feeding more milk on periprandial plasma glucagon-like peptide-2 concentrations in preweaning dairy calves.

The objective of this study was to evaluate periprandial plasma concentrations of glucagon-like peptide-2 (GLP-2), glucose, and ß-hydroxybutyrate (BHB) in response to a milk meal in preweaning dairy calves. Nineteen Holstein heifer calves were fed either a high (10 L/d; n = 9) or low (5 L/d; n = 10) amount of pasteurized whole milk from d 2 to 50 of life. Calves were housed in individual pens for the first 19 ± 3 d and fed only milk before being moved to a group pen, where they remained on their respective milk treatment and offered calf starter ad libitum. Blood samples were collected sequentially for 240 min following their milk meal at wk 3, 5, and 7 of life to characterize the periprandial response in plasma concentrations of GLP-2, glucose, and BHB. Baseline plasma glucose concentrations were increased, when a high amount was fed; however, we found no difference in area under the curve. Feeding a high amount of whole milk had no effect on baseline or periprandial plasma BHB concentrations. Baseline plasma GLP-2 concentrations decreased as calves aged. Feeding a high amount of whole milk tended to significantly increase baseline GLP-2 concentrations throughout compared with calves fed a low amount. The periprandial response of GLP-2 was not biphasic until calves were 7 wk old. In conclusion, feeding a high amount of milk may increase GLP-2 concentrations in preweaning calves, although its exact mechanism is unknown.