Corrigendum to "Effects of feed additives on rumen function and bacterial and archaeal communities during a starch and fructose challenge" (J. Dairy Sci. 106:8787-8808)

Heifers (n = 40) were randomly allocated to 5 treatment groups: (1) control (no additives); (2) virginiamycin (VM; 200 mg/d); (3) monensin (MT; 200 mg/d) + tylosin (110 mg/d); (4) monensin (MLY; 220 mg/d) + live yeast (5.0 × 108 cfu/d); (5) sodium bicarbonate (BUF; 200 g/d) + magnesium oxide (30 g/d).

Effects of negative dietary cation-anion difference and calcidiol supplementation in transition diets fed to sows on piglet survival, piglet weight, and sow metabolism

Diets that provide a negative dietary anion cation difference (DCAD) and supplement with a vitamin D metabolite 25-OH-D3 (calcidiol) may increase calcium availability at parturition, and enhance piglet survival and performance. This factorial study assessed the effects of DCAD, calcidiol (50 µg/kg), and parity (parity 1 or >1) and their interactions. Large White and Landrace sows (n = 328), parity 1 to 8 were randomly allocated in blocks to treatment diets from day 103 of gestation until day 3 postfarrow: 1) negative DCAD without calcidiol (negative DCAD + no CA), n = 84, 2) negative DCAD with calcidiol (negative DCAD + CA) n = 84, 3) positive DCAD without calcidiol (negative DCAD + no CA), n = 81, and 4) positive DCAD with calcidiol (positive DCAD + CA), n = 79. Negative DCAD diets were acidified with an anionic feed (2 kg/t) and magnesium sulfate (2 kg/t). All treatment diets contained cholecalciferol at 1,000 IU/kg. Dry sow diets contained 14.8% crude protein (CP), 5.4% crude fiber (CF), 0.8% Ca, and 83 mEq/kg DCAD. Treatment diets 1 and 2 contained 17.5% CP, 7.3% CF, 0.8% Ca, and -2 mEq/kg DCAD. Treatment diets 3 and 4 contained 17.4% CP, 7.4% CF, 0.8% Ca, and 68 mEq/kg DCAD. Before farrowing, all negative DCAD sows had lower urine pH than all sows fed a positive DCAD (5.66 ± 0.05 and 6.29 ± 0.05, respectively; P < 0.01); urinary pH was acidified for both DCAD treatments indicating metabolic acidification. The percentage of sows with stillborn piglets was not affected by DCAD, calcidiol, or parity alone but sows fed the negative DCAD + CA diet had a 28% reduction in odds of stillbirth compared to the negative DCAD + no CA diet and even lesser odds to the positive DCAD + CA diet. At day 1 after farrowing, blood gas, and mineral and metabolite concentrations were consistent with feeding a negative DCAD diet and that negative DCAD diets influence energy metabolism, as indicated by increased glucose, cholesterol, and osteocalcin concentrations and reduced nonesterified free fatty acids and 3-hydroxybutyrate concentrations. In the subsequent litter, total piglets born and born alive (14.7 ± 0.3 and 13.8 ± 0.3 piglets, respectively; P = 0.029) was greater for positive DCAD diets compared to negative DCAD diets; and there was an interaction between DCAD, calcidiol, and parity (P = 0.002). Feeding a negative DCAD diet influenced stillbirth, subsequent litter size, and metabolic responses at farrowing. More studies are needed to define optimal diets prefarrowing for sows.

Milk as an indicator of dietary imbalance

BACKGROUND

Milk provides a readily available diagnostic fluid collected daily or more frequently on an individual animal or herd basis. Milk, as an aggregated sample in bulk tank milk (BTM) represents the status of a herd instead of a single animal. In this review, we examine the potential for milk to predict risks to efficient production, reproductive success, and health on the individual cow and herd level.

FINDINGS

For many conditions related to disorders of metabolism including hyperlipdaemia and ketonaemia, improved individual cow milk testing may allow a temporally useful detection of metabolic disorder that can target intervention. However, the extension of these tests to the BTM is made more difficult by the tight temporal clustering of disorder to early lactation and the consequent mixing of cows at even moderately different stages of lactation. Integrating herd recording demographic information with Fourier-transformed mid-infrared spectra (FT-MIR) can provide tests that are useful to identify cows with metabolic disorders. The interpretation of BTM urea and protein content provides useful indications of herd nutrition. These may provide indicators that encourage further investigations of nutritional influences on herd fertility but are unlikely to provide strong diagnostic value. The fat-to-protein ratio has a high specificity, but poor sensitivity for detection of fibre insufficiency and acidosis on an individual cow basis. Selenium, zinc, β-carotene, and vitamin E status of the herd can be determined using BTM.

CONCLUSIONS

There appears to be increasing potential for the use of milk as a diagnostic fluid as more in-parlour tests become available for individual cows. However, the BTM appears to have under-utilised potential for herd monitoring.

Effects of feed additives on rumen function and bacterial and archaeal communities during a starch and fructose challenge

The objective of this study was to improve understandings of the rumen microbial ecosystem during ruminal acidosis and responses to feed additives to improve prudent use strategies for ruminal acidosis control. Rumen bacterial and archaeal community composition (BCC) and its associations with rumen fermentation measures were examined in Holstein heifers fed feed additives and challenged with starch and fructose. Heifers (n = 40) were randomly allocated to 5 treatment groups: (1) control (no additives); (2) virginiamycin (VM; 200 mg/d); (3) monensin (MT; 200 mg/d) + tylosin (110 mg/d); (4) monensin (MLY; 220 mg/d) + live yeast (5.0 × 1012 cfu/d); (5) sodium bicarbonate (BUF; 200 g/d) + magnesium oxide (30 g/d). Heifers were fed twice daily a 62% forage:38% concentrate total mixed ration at 1.25% of body weight (BW) dry matter (DM)/d for a 20-d adaptation period with their additive(s). Fructose (0.1% of BW/d) was added to the ration for the last 10 d of adaptation. On d 21 heifers were challenged once with a ration consisting of 1.0% of BW DM wheat and 0.2% of BW fructose plus their additive(s). A rumen sample was collected from each heifer via stomach tube weekly (d 0, 7, 14) and 5 times over a 3.6 h period at 5, 65, 115, 165, and 215 min after consumption of the challenge ration (d 21) and analyzed for pH, and ammonia, d- and l-lactate, volatile fatty acids (VFA), and histamine concentrations and total bacteria and archaea. The 16S rRNA gene spanning the V4 region was PCR amplified and sequenced. Alpha and β diversity and associations of relative abundances of taxa with rumen fermentation measures were evaluated. Rumen BCC shifted among treatment groups in the adaptation period and across the challenge sampling period, indicating the feed additives had different modes of action. The monensin-containing treatment groups, MT and MLY often had similar relative abundances of rumen bacterial phyla and families. The MLY treatment group was characterized in the challenge period by increased relative abundances of the lactate utilizing genera Anaerovibrio and Megasphaera. The MLY treatment group also had increased diversity of ruminal bacteria which may provide resilience to changes in substrates. The control and BUF treatment groups were most similar in BCC. A redundancy analysis showed the MLY treatment group differed from all other treatment groups and concentrations of histamine and valerate in the rumen were associated with the most variation in the microbiota, 5.3% and 4.8%, respectively. It was evident from the taxa common to all treatment groups that cattle have a core microbiota. Functional redundancy of rumen bacteria which was reflected in the greater sensitivity for the rumen BCC than rumen fermentation measures likely provide resilience to changes in substrate. This functional redundancy of microbes in cattle suggests that there is no single optimal ruminal microbial population and no universally superior feed additive(s). In summary, differences in modes of action suggest the potential for more targeted and improved prudent use of feed additives with no single feed additive(s) providing an optimal BCC in all heifers.

Data on the effects of the anionic protein meal BioChlorⓇ on sows before and after farrowing

Three hundred and two parity 3 and 4 sows were allocated to one of three treatment groups: A (n=106): Control group fed the standard lactation diet; B (n=94): Lactation diet supplemented with 10 kg BioChlor/T; C (n=102): Lactation diet supplemented with 20 kg BioChlor/T. The sows were randomly allocated to treatment on entry to the farrowing shed at 100 d of gestation. The numbers allocated to each treatment were not equal with fewer sows allocated to treatment B at the start of treatment feeding than originally intended. Six allocated sows were not pregnant at their due farrowing date and two control group sows died after treatment feeding commenced prior to farrowing. All sows were individually housed in sow stalls and were fed 3 kg of their treatment diet once a day from d 105 of gestation. At d 110 of gestation, sows were moved into farrowing crates and continued to be fed 3 kg of their treatment diet once a day until the day of farrowing followed by ad libitum feeding of the treatment diet during a 27-d lactation. Approximately 50 litters from each treatment were randomly weighed to determine treatment effects on piglet average daily gain from birth to weaning. Litters were standardized within treatment to 10 piglets per litter at d 3 of lactation by allocating piglets from sows within treatment that had more than 12 piglets. After weaning, all sows were transported to a commercial module and mated on the first display of estrus. Sows were offered a common boar shed diet (13.8 MJ DE/kg; 170 g protein/kg; 9 g lysine/kg) ad libitum from weaning to mating. Following mating, all animals were fed 2.5 kg of a gestation diet (13.0 MJ DE/kg; 125 g protein/kg; 6 g lysine/kg) until farrowing. All sows were stalled individually during the gestation period following treatment feeding. Measures included: date of birth, number of piglets stillborn, number of piglets born alive, total number of piglets born, number of mummified feti, litter weight and number of piglets weighed at birth, litter weight and number of piglets at d 3, 14, and 26, number of piglets stillborn (gestation 2), number of piglets born alive (gestation 2), and total number of piglets born (gestation 2). The number of piglets born alive, number of total piglets born, and all weight measures were analyzed with mixed models with treatment as a fixed effect and sow within farrowing house as a random effect. A negative binomial model was used to estimate the incidence of still birth with sow within farrowing house as a random effect. For the odds of being re-mated a logistic regression mixed model was used to evaluate differences among treatment groups. These data provide information on an individual animal basis that can be used to inform pig producers, nutritionists, veterinarians, and researchers for further investigation on the use of anionic feeds in gestation diets of pigs and is suitable for future meta-analyses.

Characterizing ruminal acidosis risk: A multiherd, multicountry study

A multicenter observational study was conducted on early lactation Holstein cows (n = 261) from 32 herds from 3 regions (Australia, AU; California, CA; and Canada, CAN) to characterize their risk of acidosis into 3 groups (high, medium, or low) using a discriminant analysis model previously developed. Diets ranged from pasture supplemented with concentrates to total mixed ration (nonfiber carbohydrates = 17 to 47 and neutral detergent fiber = 27 to 58% of dry matter). Rumen fluid samples were collected <3 h after feeding and analyzed for pH, and ammonia, d- and l-lactate, and volatile fatty acid (VFA) concentrations. Eigenvectors were produced using cluster and discriminant analysis from a combination of rumen pH, and ammonia, d-lactate, and individual VFA concentrations and were used to calculate the probability of the risk of ruminal acidosis based on proximity to the centroid of 3 clusters. Bacterial 16S ribosomal DNA sequence data were analyzed to characterize bacteria. Individual cow milk volume, fat, protein, and somatic cell count values were obtained from the closest herd test to the rumen sampling date (median = 1 d before rumen sampling). Mixed model analyses were performed on the markers of rumen fermentation, production characteristics, and the probability of acidosis. A total of 26.1% of the cows were classified as high risk for acidosis, 26.8% as medium risk, and 47.1% as low risk. Acidosis risk differed among regions with AU (37.2%) and CA (39.2%) having similar prevalence of high-risk cows and CAN only 5.2%. The high-risk group had rumen phyla, fermentation, and production characteristics consistent with a model of acidosis that reflected a rapid rate of carbohydrate fermentation. Namely, acetate to propionate ratio (1.98 ± 0.11), concentrations of valerate (2.93 ± 0.14 mM), milk fat to protein ratio (1.11 ± 0.047), and a positive association with abundance of phylum Firmicutes. The medium-risk group contains cows that may be inappetant or that had not eaten recently or were in recovery from acidosis. The low-risk group may represent cattle that are well fed with a stable rumen and a slower rumen fermentation of carbohydrates. The high risk for acidosis group had lower diversity of bacteria than the other groups, whereas CAN had a greater diversity than AU and CA. Rumen fermentation profile, abundance of ruminal bacterial phyla, and production characteristics of early lactation dairy cattle from 3 regions were successfully categorized in 3 different acidosis risk states, with characteristics differing between acidosis risk groups. The prevalence of acidosis risk also differed between regions.

Associations among the genome, rumen metabolome, ruminal bacteria, and milk production in early-lactation Holsteins

A multicenter observational study to evaluate genome-wide association was conducted in early-lactation Holstein cows (n = 293) from 36 herds in Canada, the USA, and Australia. Phenotypic observations included rumen metabolome, acidosis risk, ruminal bacterial taxa, and milk composition and yield measures. Diets ranged from pasture supplemented with concentrates to total mixed rations (nonfiber carbohydrates = 17 to 47, and neutral detergent fiber = 27 to 58% of dry matter). Rumen samples were collected <3 h after feeding and analyzed for pH, ammonia, d- and l-lactate, volatile fatty acid (VFA) concentrations, and abundance of bacterial phyla and families. Eigenvectors were produced using cluster and discriminant analyses from a combination of pH and ammonia, d-lactate, and VFA concentrations, and were used to estimate the probability of the risk of ruminal acidosis based on proximity to the centroid of 3 clusters, termed high (24.0% of cows), medium (24.2%), and low risk (51.8%) for acidosis. DNA of sufficient quality was successfully extracted from whole blood (218 cows) or hair (65 cows) collected simultaneously with the rumen samples and sequenced using the Geneseek Genomic Profiler Bovine 150K Illumina SNPchip. Genome-wide association used an additive model and linear regression with principal component analysis (PCA) population stratification and a Bonferroni correction for multiple comparisons. Population structure was visualized using PCA plots. Single genomic markers were associated with milk protein percent and the center logged ratio abundance of the phyla Chloroflexi, SR1, and Spirochaetes, and tended to be associated with milk fat yield, rumen acetate, butyrate, and isovalerate concentrations and with the probability of being in the low-risk acidosis group. More than one genomic marker was associated or tended to be associated with rumen isobutyrate and caproate concentrations, and the center log ratio of the phyla Bacteroidetes and Firmicutes and center log ratio of the families Prevotellaceae, BS11, S24-7, Acidaminococcaceae, Carnobacteriaceae, Lactobacillaceae, Leuconostocaceae, and Streptococcaceae. The provisional NTN4 gene, involved in several functions, had pleiotropy with 10 bacterial families, the phyla Bacteroidetes and Firmicutes, and butyrate. The ATP2CA1 gene, involved in the ATPase secretory pathway for Ca²⁺ transport, overlapped for the families Prevotellaceae, S24-7, and Streptococcaceae, the phylum Bacteroidetes, and isobutyrate. No genomic markers were associated with milk yield, fat percentage, protein yield, total solids, energy-corrected milk, somatic cell count, rumen pH, ammonia, propionate, valerate, total VFA, and d-, l-, or total lactate concentrations, or probability of being in the high- or medium-risk acidosis groups. Genome-wide associations with the rumen metabolome, microbial taxa, and milk composition were present across a wide geographical and management range of herds, suggesting the existence of markers for the rumen environment but not for acidosis susceptibility. The variation in pathogenesis of ruminal acidosis in the small population of cattle in the high risk for acidosis group and the dynamic nature of the rumen as cows cycle through a bout of acidosis may have precluded the identification of markers for acidosis susceptibility. Despite a limited sample size, this study provides evidence of interactions between the mammalian genome, the rumen metabolome, ruminal bacteria, and milk protein percentage.

Effects of mannan-oligosaccharide and Bacillus subtilis supplementation to preweaning Holstein dairy heifers on body weight gain, diarrhea, and shedding of fecal pathogens

The objective of this clinical trial was to evaluate the effectiveness of probiotic, prebiotic, and synbiotic supplementation on average daily weight gain (ADG), duration of diarrhea, age at incidence of diarrhea, fecal shedding of Cryptosporidium oocysts, enteric pathogens, and the odds of pneumonia in preweaning dairy heifer calves on a commercial dairy. Feeding prebiotics and probiotics may improve health and production of calves. Hence, healthy Holstein heifer calves (n = 1,801) from a large California dairy were enrolled at 4 to 12 h of age and remained in this study until weaning at 60 d of age. Calves were block randomized to 1 of 4 treatments: (1) control, (2) yeast culture enriched with mannan-oligosaccharide (prebiotic), (3) Bacillus subtilis (probiotic), and (4) combination of both products (synbiotic), which were fed in milk twice daily from enrollment until weaning. Serum total protein at enrollment and body weight at 7, 42, and 56 d of age were measured. Fecal consistency was assessed daily for the entire preweaning period. A subgroup of 200 calves had fecal samples collected at 7, 14, 21, and 42 d for microbial culture and enumeration of Cryptosporidium oocysts by direct fluorescent antibody staining. Synbiotic-treated calves had 19 g increased ADG compared with control calves for overall ADG, from 7 to 56 d. From 42 to 56 d, prebiotic-treated calves had 85 g greater ADG and synbiotic-treated calves had 78 g greater ADG than control calves. There was no difference in duration of the first diarrhea episode, hazard of diarrhea, or odds of pneumonia per calf with treatment. Probiotic-treated calves had 100 times lower fecal shedding of Cryptosporidium oocysts at 14 d and prebiotic-treated calves had fewer Escherichia coli and pathogenic E. coli at 42 d compared with control calves. Although there were no effects on duration of diarrhea or pneumonia incidence, greater ADG in the late preweaning period may reflect treatment effects on enteric pathogens during the rearing process. The decreased shedding of Cryptosporidium should reduce infectious pressure, environmental contamination, and public health risks from Cryptosporidium. Our findings suggest ADG and potential health benefits for calves fed prebiotics, probiotics, and synbiotics and can help the dairy industry make informed decisions on the use of these products in dairy production.

Effect of 25-hydroxyvitamin D3 during prepartum transition and lactation on production, reproduction, and health of lactating dairy cows

We hypothesized that feeding 25-hydroxyvitamin D₃ [25-(OH)D₃] during lactation and prepartum in conjunction with negative dietary cation-anion difference diets would improve milk production, increase the probability of pregnancy, and reduce the incidence of postcalving diseases. Cows from 4 dairies with prepartum transition diets negative in dietary cation-anion difference were used in 2 randomized cohort experiments. In Experiment 1 (Exp. 1), cows were assigned to control [CON; n = 645; no 25-(OH)D₃] or treatment [TRT; n = 537; 2 mg/d of 25-(OH)D₃ from ∼21 d prepartum to parturition and 1 mg/d in lactation] groups at ∼21 d prepartum. Cows were monitored for weekly milk yield, milk composition every 60 d, and health and reproductive measures. In Experiment 2 (Exp. 2), cows (n = 2,064; median 147 d in milk) were assigned to 4 groups and monitored for the same measures as in Exp. 1 to the end of that lactation (L1), the subsequent transition (∼21 d prepartum to parturition), and the next lactation (L2). Groups were as follows, with the amount of 25-(OH)D₃ fed (mg/d) indicated in parentheses for L1, transition, and L2, respectively: (A) control-control (CON-CON; 0-0-0), (B) treatment-treatment (TRT-TRT; 1-2-1), (C) control-treatment (CON-TRT; 0-2-1), and (D) treatment-control (TRT-CON; 1-0-0). For L1, a total of 1,032 cows entered the control groups A or C and a total of 1,032 cows in groups B or D. The number of cows in groups A to D that entered L2 was 521, 523, 273, and 248, respectively. Blood calcium, phosphorus, and 25-(OH)D₃ concentrations were measured from 17 cows/group at 5 times. In Exp. 1, TRT cows had 0.2 lower log somatic cell count than CON cows (4.21 ± 0.045 vs. 4.01 ± 0.050, respectively) and multiparous TRT cows had 41 ± 23% higher probability of pregnancy/day than multiparous CON cows, resulting in a 22-d median decrease in time to pregnancy. Primiparous TRT cows had 1.67 ± 0.40 times greater odds of mastitis/day than primiparous CON cows. In Exp. 2 TRT-TRT cows had between 16 and 29% lower probability to be bred/day than other groups. Multiparous CON-CON and TRT-CON cows had 20 ± 8% and 30 ± 17% greater probability of pregnancy, respectively, than multiparous TRT-TRT cows. Serum calcium concentrations were not affected by group, but phosphorus and 25-(OH)D₃ concentrations were highest in the TRT-TRT cows. The study provides further insights into the use of 25(OH)D₃ in transition and lactation.

Effects of in-feed enzymes on milk production and components, reproduction, and health in dairy cows

Our objectives were to characterize responses in the field to a mix of fibrolytic enzymes using large commercial dairy herds and sufficient study power to evaluate milk production and reproductive responses to an enzyme treatment started during the precalving period. We hypothesized that the use of the enzyme treatment would increase milk production when provided to dairy cows precalving and for approximately 200 d of lactation. The study was conducted on 7,507 cows, in 8 replicates and 16 pens, at 3 dairies in the United States. Eight pens were randomly allocated as control pens and received no enzyme, and another 8 pens received enzyme treatment at a dose of 750 mL/t of dry matter feed. Milk production and energy-corrected milk yield were increased with the enzyme treatment by 0.70 and 0.80 kg/d, respectively, across a 5-month period. Milk fat percentage was not significantly increased by enzyme treatment, but milk fat yield was significantly increased by 0.040 kg/d, compared with controls. Milk protein yield increased 0.010 kg/d with enzyme treatment despite a small reduction of 0.020 percentage units in milk protein percentage. We found no evidence of an increase in the ln somatic cell count for the enzyme-treated cows. Body weight overall was not increased for enzyme-treated cows, but we did observe a numerical increase in dry matter intake (0.20 kg/head per day) for enzyme-treated cows. Most production responses to the enzyme treatment were influenced by dairy. Compared with controls, milk yield in enzyme-treated cows was significantly higher by 3.6 kg/d in dairy 2 and numerically higher by 0.60 and 0.20 kg/d in dairies 1 and 3, respectively. Reproduction, health, and risk of removal or death were not significantly influenced by treatment, apart from a reduced time to first breeding. Production responses to the enzyme treatment varied by dairy from substantial to minor increases, but variation among dairies was not evident in differences in dry matter intake or in partitioning of body weight among enzyme-treated and control pens and cows. It appears likely that the increase in production reflected increased digestibility of feed; however, further work is needed to identify factors influencing the variation in production responses to enzymes.

The effect of temperate or tropical pasture grazing state and grain-based concentrate allocation on dairy cattle production and behavior

Grain-based concentrate (GBC) supplement is of high cost to dairy farmers as a feed source as opposed to grazed pasture. Milk production response to GBC is affected by the composition and nutritive value of the remainder of the diet, animal factors, and interactions between forage type and level of GBC. In grazing systems, dairy cattle encounter contrasting pasture states, primarily because the social structure of the herd affects the timing of when each animal accesses a paddock after milking as a result of a relatively consistent cow milking order. However, the effect of feed management, namely pasture state and GBC allocation, on dairy cattle production and behavior is unknown. We examined the effect of varying GBC allocation for dairy cattle grazing differing states of kikuyu grass (Pennisetum clandestinum, a tropical pasture species; experiment 1) and annual ryegrass (Lolium multiflorum L., a temperate pasture species; experiment 2) on dry matter intake, milk production and composition, and grazing behavior. For each experiment, 90 lactating dairy cattle were randomly allocated to 2 consistent (fresh-fresh and depleted-depleted) and 2 inconsistent (fresh-depleted and depleted-fresh pasture state treatments (defined as sequences of pasture state allocation for the morning and afternoon grazing events) and 3 GBC treatments [2.7, 5.4, and 8.1 kg of dry matter (DM)/cow per day], giving 12 treatment combinations for each experiment. The duration of each experiment was 14 d, with the first 7 d used as adaptation to treatment. In each experiment, 3 cattle were selected from each of the 12 pasture type × GBC treatment groups within the experimental herd to determine herbage intake and total DM digestibility using the n-alkanes method (n = 36). There was no interaction between kikuyu grass or ryegrass pasture state and GBC level for intake, digestibility, or milk yield or components. Dairy cattle offered fresh-fresh and depleted-fresh ryegrass produced 9% more milk yield, in line with greater pasture intakes, compared with fresh-depleted and depleted-depleted pasture states. Dairy cattle offered fresh-fresh kikuyu grass had 8% more milk yield and 14% more milk protein yield than other pastures states, but there was no effect of pasture state on milk composition. Milk yield increased with GBC level for both pasture species (∼0.7-0.8 kg of milk/kg of DM GBC) as GBC level increased from 2.5 to 5.4 kg of DM/cow per day. There was a poor response (0.3 kg of milk/kg of DM GBC), and no response, when GBC levels increased from 5.4 to 8.1 kg of DM/cow per day for kikuyu grass and ryegrass, respectively, in line with pasture DMD. Time spent grazing, lying, and ruminating were not associated with kikuyu grass pasture state, GBC, or their interaction. Despite this, there was a linear increase in grazing time in the afternoon coinciding with a linear decrease in lying and rumination time for both kikuyu grass and ryegrass pasture. Together these findings reveal the effect of pasture state and GBC allocation on dairy cattle production and behavior. Tailoring GBC allocation to the state of pasture accessed by cattle appears unwarranted, but there is an opportunity to alter the timing of pasture access to increase herd-level milk production efficiency.

A meta-analysis of lasalocid effects on rumen measures, beef and dairy performance, and carcass traits in cattle

The effects of lasalocid on rumen measures, beef and dairy performance, and carcass traits were evaluated using meta-analysis. Meta-regression was used to investigate sources of heterogeneity. Ten studies (20 comparisons) were used in the meta-analysis on rumen measures. Lasalocid increased total VFA and ammonia concentrations by 6.46 and 1.44 m, respectively. Lasalocid increased propionate and decreased acetate and butyrate molar percentage (M%) by 4.62, 3.18, and 0.83%, respectively. Valerate M% and pH were not affected. Meta-regression found butyrate M% linearly increased with duration of lasalocid supplementation (DUR; = 0.017). When >200 mg/d was fed, propionate and valerate M% were higher and acetate M% was lower ( = 0.042, = 0.017, and = 0.005, respectively). Beef performance was assessed using 31 studies (67 comparisons). Lasalocid increased ADG by 40 g/d, improved feed-to-gain ratio (F:G) by 410 g/kg, and improved feed efficiency (FE; combined measure of G:F and the inverse of F:G). Lasalocid did not affect DMI, but heterogeneity in DMI was influenced by DUR ( = 0.004) and the linear effect of entry BW ( = 0.011). The combination of ≤100 vs. >100 d DUR and entry BW ≤275 vs. >275 kg showed that cattle ≤275 kg at entry fed lasalocid for >100 d had the lowest DMI. Heterogeneity of ADG was influenced by the linear effect of entry BW ( = 0.028) but not DUR. Combining entry BW ≤275 vs. >275 kg and DUR showed that cattle entering at >275 kg fed ≤100 d had the highest ADG. The FE ( = 0.025) and F:G ( = 0.015) linearly improved with dose, and entry BW >275 kg improved F:G ( = 0.038). Fourteen studies (25 comparisons) were used to assess carcass traits. Lasalocid increased HCW by 4.73 kg but not dressing percentage, mean fat cover, or marbling score. Heterogeneity of carcass traits was low and not affected by DUR or dose. Seven studies (11 comparisons) were used to assess dairy performance but the study power was relatively low and the evidence base is limited. Lasalocid decreased DMI in total mixed ration-fed cows by 0.89 kg/d but had no effect on milk yield, milk components, or component yields. Dose linearly decreased DMI ( = 0.049). The DUR did not affect heterogeneity of dairy measures. This work showed that lasalocid improved ADG, HCW, FE, and F:G for beef production. These findings may reflect improved energy efficiency from increased propionate M% and decreased acetate and butyrate M%. Large dairy studies are required for further evaluation of effects of lasalocid on dairy performance.

Acute photosensitisation and mortality in a herd of dairy cattle in Tasmania

CASE HISTORY

A herd of Holstein, Jersey, or Holstein-Jersey cross lactating cattle of mixed ages presented with a sudden drop in milk yield in 94/678 cows on 3 October 2014 (Day 0). The herd was located in Gretna in the Derwent Valley (Tasmania, Australia) and had been grazing dryland pasture.

CLINICAL FINDINGS

On Day 0 the cows variably showed recumbency, peracute photosensitisation, inflamed coronary bands, conjunctival erythema, periauricular oedema, distress indicated by kicking at the flank, bruxism, discomfort, weight shifting, vocalisation indicating pain and depression. Blood samples collected on Day 4 from five clinically affected cows showed high activities of aspartate aminotransferase, glutamate dehydrogenase and gamma-glutamyl transferase. Morbidity, based on the number of treated cases within 72 hours of clinical onset, was estimated at 165/678 cows (24.3%). Mortality over the first 30 days was 19/678 cows (2.8%).

PATHOLOGICAL FINDINGS

Necropsies of two cows on Day 4 showed marked distension of the gall bladder and extensive icterus. Necropsies of another two cows on Day 5 showed enlarged livers with severe damage and oedema of the distal abomasum. Severe ulcerative abomasal gastritis was present in both cows. Hepatic histopathology was consistent with chronic cholangiohepatitis.

MYCOTOXICOLOGY

Fifty-five different mycotoxins were detected from a barley grass (Hordeum murinum) sample from the presumably contaminated pasture. Concentrations of B-trichothecenes, fumonisins, and zearalenone metabolites from this sample were remarkably high. The leaf smut, Jamesdicksonia dactylidis, that has not been previously reported in Tasmania, was identified from the sample of barley grass, but it is not known whether the smut can produce toxins.

DIAGNOSIS

Probably an undescribed peracute mycotoxicosis associated with the ingestion of contaminated dryland pasture.

CLINICAL RELEVANCE

A definitive diagnosis could not be reached in this case of acute photosensitisation and mortality in dairy cattle grazing possibly contaminated dryland pasture. The findings differed from both facial eczema and acute bovine liver disease, suggesting an undescribed mycotoxicosis.

Effects of partial mixed rations and supplement amounts on milk production and composition, ruminal fermentation, bacterial communities, and ruminal acidosis

Late-lactation Holstein cows (n=144) that were offered 15kg dry matter (DM)/cow per day of perennial ryegrass to graze were randomized into 24 groups of 6. Each group contained a fistulated cow and groups were allocated to 1 of 3 feeding strategies: (1) control (10 groups): cows were fed crushed wheat grain twice daily in the milking parlor and ryegrass silage at pasture; (2) partial mixed ration (PMR; 10 groups): PMR that was isoenergetic to the control diet and fed twice daily on a feed pad; (3) PMR+canola (4 groups): a proportion of wheat in the PMR was replaced with canola meal to produce more estimated metabolizable protein than other groups. Supplements were fed to the control and PMR cows at 8, 10, 12, 14, or 16kg of DM/d, and to the PMR+canola cows at 14 or 16kg of DM/d. The PMR-fed cows had a lower incidence of ruminal acidosis compared with controls, and ruminal acidosis increased linearly and quadratically with supplement fed. Yield of milk fat was highest in the PMR+canola cows fed 14 or 16kg of total supplement DM/d, followed by the PMR-fed cows, and was lowest in controls fed at these amounts; a similar trend was observed for milk fat percentage. Milk protein yield was higher in the PMR+canola cows fed 14 or 16kg of total supplement DM/d. Milk yield and milk protein percentage were not affected by feeding strategy. Milk, energy-corrected milk, and milk protein yields increased linearly with supplement fed, whereas milk fat percentage decreased. Ruminal butyrate and d-lactate concentrations, acetate-to-propionate ratio, (acetate + butyrate)/propionate, and pH increased in PMR-fed cows compared with controls for all supplement amounts, whereas propionate and valerate concentrations decreased. Ruminal acetate, butyrate, and ammonia concentrations, acetate-to-propionate ratio, (acetate + butyrate)/propionate, and pH linearly decreased with amounts of supplement fed. Ruminal propionate concentration linearly increased and valerate concentration linearly and quadratically increased with supplement feeding amount. The Bacteroidetes and Firmicutes were the dominant bacterial phyla identified. The Prevotellaceae, Ruminococcaceae, and Lachnospiraceae were the dominant bacterial families, regardless of feeding group, and were influenced by feeding strategy, supplement feeding amount, or both. The Veillonellaceae family decreased in relative abundance in PMR-fed cows compared with controls, and the Streptococcaeae and Lactobacillaceae families were present in only minor relative abundances, regardless of feeding group. Despite large among- and within-group variation in bacterial community composition, distinct bacterial communities occurred among feeding strategies, supplement amounts, and sample times and were associated with ruminal fermentation measures. Control cows fed 16kg of DM of total supplement per day had the most distinct ruminal bacterial community composition. Bacterial community composition was most significantly associated with supplement feeding amount and ammonia, butyrate, valerate, and propionate concentrations. Feeding supplements in a PMR reduced the incidence of ruminal acidosis and altered ruminal bacterial communities, regardless of supplement feeding amount, but did not result in increased milk measures compared with isoenergetic control diets component-fed to late-lactation cows.

Ruminal bacterial community shifts in grain-, sugar-, and histidine-challenged dairy heifers

Ruminal bacterial community composition (BCC) and its associations with ruminal fermentation measures were studied in dairy heifers challenged with combinations of grain, fructose, and histidine in a partial factorial study. Holstein-Friesian heifers (n=30) were randomly allocated to 5 triticale grain-based treatment groups: (1) control (no grain), (2) grain [fed at a dry matter intake (DMI) of 1.2% of body weight (BW)], (3) grain (0.8% of BW DMI) + fructose (0.4% of BW DMI), (4) grain (1.2% of BW DMI) + histidine (6g/head), and (5) grain (0.8% of BW DMI) + fructose (0.4% of BW DMI) + histidine (6g/head). Ruminal fluid was collected using a stomach tube 5, 115, and 215min after consumption of the rations and bacterial 16S ribosomal DNA sequence data was analyzed to characterize bacteria. Large variation among heifers and distinct BCC were evident in a between-group constrained principal components analysis. Bacterial composition in the fructose-fed heifers was positively related to total lactate and butyrate concentrations. Bacterial composition was positively associated with ruminal ammonia, valerate, and histamine concentrations in the grain-fed heifers. The predominant phyla were the Firmicutes (57.6% of total recovered sequences), Bacteroidetes (32.0%), and candidate phylum TM7 (4.0%). Prevotella was the dominant genus. In general, grain or histidine or their interactions with time had minimal effects on the relative abundance of bacterial phyla and families. Fructose increased and decreased the relative abundance of the Firmicutes and Proteobacteria phyla over time, respectively, and decreased the abundance of the Prevotellaceae family over time. The relative abundance of the Streptococcaceae and Veillonellaceae families was increased in the fructose-fed heifers and these heifers over time. A total of 31 operational taxonomic units differed among treatment groups in the 3.6h sampling period, Streptococcus bovis was observed in fructose fed animals. The TM7 candidate phylum had an increased abundance of sequence reads by over 2.5 fold due to the introduction of histidine into the diet. Rapid changes in BCC can occur in a short period after a single substrate challenge and the nature of these changes may influence ruminal acidosis risk and differ from those in cattle exposed to substrate challenges over a longer time period.

Effects of feed additives on rumen and blood profiles during a starch and fructose challenge

We evaluated the effect of feed additives on the risk of ruminal acidosis in Holstein heifers (n = 40) fed starch and fructose in a challenge study. Heifers were randomly allocated to feed additive groups (n = 8 heifers/group): (1) control (no additives); (2) virginiamycin (VM); (3) monensin + tylosin (MT); (4) monensin + live yeast (MLY); and (5) sodium bicarbonate + magnesium oxide (BUF). Heifers were fed 2.5% of body weight (BW) dry matter intake (DMI) per day of a total mixed ration (62:38 forage:concentrate) and feed additives for a 20-d adaptation period. Fructose (0.1% of BW/d) was included for the last 10d of the adaptation period. On d 21, heifers were fed to target a DMI of 1.0% of BW of wheat, fructose at 0.2% of BW, and their feed additives. Rumen fluid samples obtained by stomach tube and blood samples were collected weekly as well as during a 3.6-h period on challenge day (d 21). Virginiamycin and BUF groups maintained a consistently high DMI across the 20-d adaptation period. The MLY heifers had low DMI of the challenge ration. Average daily gain and feed conversion ratio were not affected by feed additives. All rumen and plasma measures changed weekly over adaptation and over the challenge sampling period with the exception of rumen total lactate and histamine concentrations, plasma oxidative stress index, and ceruloplasmin. Substantial within- and between-group variation was observed in rumen and plasma profiles at challenge sampling. No significant group changes were observed in rumen total volatile fatty acids, propionate, acetate-to-propionate ratio, isobutyrate, caproate, isovalerate, total lactate, d- and l-lactate, and pH measures on challenge day. Acetate concentration was increased in the BUF and control groups on challenge day. Butyrate concentration was lower in the MLY and MT groups compared with other groups at challenge. Valerate concentrations were lowest in the control, VM, and BUF groups and lactate concentrations were numerically lower in the MLY, VM, and BUF groups. Total lactate concentrations were >10mM for each group throughout the challenge. Ammonia concentrations were lower in the MLY and MT groups. Histamine concentrations were decreased in MLY and increased in the VM and BUF groups. Plasma oxidative stress measures were not influenced by feed additives weekly or on challenge day, except for an increase in biological antioxidant potential in the control, VM, and MT groups on challenge day. Despite the large within-animal variation, all feed additives modified rumen function and may influence the risk of acidosis by different mechanisms; however, none stabilized the rumen in all heifers.

Effects of grain, fructose, and histidine feeding on endotoxin and oxidative stress measures in dairy heifers

Ruminal endotoxin and plasma oxidative stress biomarker concentrations were studied in dairy heifers challenged with grain, fructose, and histidine in a partial factorial study. Holstein-Friesian heifers [n=30; average body weight (BW) of 359.3±47.3 kg] were randomly allocated to 5 treatment groups: (1) control (no grain); (2) grain [crushed triticale at 1.2% of BW dry matter intake (DMI)]; (3) grain (0.8% of BW DMI) + fructose (0.4% of BW DMI); (4) grain (1.2% of BW DMI) + histidine (6g/head); and (5) grain (0.8% of BW DMI) + fructose (0.4% of BW DMI) + histidine (6 g/head). Rumen samples were collected by stomach tube 5, 65, 115, 165, and 215 min after diet consumption and blood samples at 5 and 215 min after consumption. Rumen fluid was analyzed for endotoxin concentrations. Plasma was analyzed for concentrations of the following oxidative stress biomarkers: reactive oxygen metabolites (dROM), biological antioxidant potential (BAP), advanced oxidation protein products, and ceruloplasmin, and activity of glutathione peroxidase. Dietary treatment had no effect on concentrations of endotoxin or oxidative stress biomarkers. We observed no interactions of treatment by time. Ruminal concentrations of endotoxin decreased during the sampling period from 1.12×10(5) ± 0.06 to 0.92×10(5) endotoxin units/mL ± 0.05 (5 and 215 min after diet consumption, respectively). Concentrations of dROM and the oxidative stress index (dROM/BAP × 100) increased over the sampling period, from 108.7 to 123.5 Carratelli units (Carr U), and from 4.1 to 4.8, respectively. Ceruloplasmin concentrations markedly declined 5 min after the consumption of diets, from 190 to 90 mg/L over the 215-min sampling period. Overall, a single feeding challenge for dairy cattle with grain, fructose, and histidine, and combinations thereof, may not be sufficient to induce marked changes in endotoxin or oxidative stress biomarker concentrations.

In vivo indices for predicting acidosis risk of grains in cattle: Comparison with in vitro methods

Our objective was to evaluate a near-infrared reflectance spectroscopy (NIRS) used in the feed industry to estimate the potential for grains to increase the risk of ruminal acidosis. The existing NIRS calibration was developed from in sacco and in vitro measures in cattle and grain chemical composition measurements. To evaluate the existing model, 20 cultivars of 5 grain types were fed to 40 Holstein heifers using a grain challenge protocol and changes in rumen VFA, ammonia, lactic acids, and pH that are associated with acidosis were measured. A method development study was performed to determine a grain feeding rate sufficient to induce non-life threatening but substantial ruminal changes during grain challenge. Feeding grain at a rate of 1.2% of BW met these criteria, lowering rumen pH (P = 0.01) and increasing valerate (P < 0.01) and propionate concentrations (P = 0.01). Valerate was the most discriminatory measure indicating ruminal change during challenge. Heifers were assigned using a row by column design in an in vivo study to 1 of 20 grain cultivars and were reassigned after a 9 d period (n = 4 cattle/treatment). The test grains were dry rolled oats (n = 3), wheat (n = 6), barley (n = 4), triticale (n = 4), and sorghum (n = 3) cultivars. Cattle were adapted to the test grain and had ad libitum access to grass silage 11 d before the challenge. Feed was withheld for 14 h before challenge feeding with 0.3 kg DM of silage followed by the respective test grain fed at 1.2% of BW. A rumen sample was taken by stomach tube 5, 65, 110, 155, and 200 min after grain consumption. The rumen is not homogenous and samples of rumen fluid obtained by stomach tube will differ from those gained by other methods. Rumen pH was measured immediately; individual VFA, ammonia, and D- and L-lactate concentrations were analyzed later. Rumen pH (P = 0.002) and all concentrations of fermentation products differed among grains (P = 0.001). A previously defined discriminant score calculated at 200 min after challenge was used to rank grains for acidosis risk. A significant correlation between the discriminant score and the NIRS ranking (r = 0.731, P = 0.003) demonstrated the potential for using NIRS calibrations for predicting acidosis risk of grains in cattle. The overall rankings of grains for acidosis risk were wheat > triticale > barley > oats > sorghum.

Effect of fat additions to diets of dairy cattle on milk production and components: a meta-analysis and meta-regression

The objectives of this study were to critically review randomized controlled trials, and quantify, using meta-analysis and meta-regression, the effects of supplementation with fats on milk production and components by dairy cows. We reviewed 59 papers, of which 38 (containing 86 comparisons) met eligibility criteria. Five groups of fats were evaluated: tallows, calcium salts of palm fat (Megalac, Church and Dwight Co. Inc., Princeton, NJ), oilseeds, prilled fat, and other calcium salts. Milk production responses to fats were significant, and the estimated mean difference was 1.05 kg/cow per day, but results were heterogeneous. Milk yield increased with increased difference in dry matter intake (DMI) between treatment and control groups, decreased with predicted metabolizable energy (ME) balance between these groups, and decreased with increased difference in soluble protein percentage of the diet between groups. Decreases in DMI were significant for Megalac, oilseeds, and other Ca salts, and approached significance for tallow. Feeding fat for a longer period increased DMI, as did greater differences in the amount of soluble protein percentage of the diet between control and treatment diets. Tallow, oilseeds, and other Ca salts reduced, whereas Megalac increased, milk fat percentage. Milk fat percentage effects were heterogeneous for fat source. Differences between treatment and control groups in duodenal concentrations of C18:2 and C 18:0 fatty acids and Mg percentage reduced the milk fat percentage standardized mean difference. Milk fat yield responses to fat treatments were very variable. The other Ca salts substantially decrease, and the Megalac and oilseeds increased, fat yield. Fat yield increased with increased DMI difference between groups and was lower with an increased estimated ME balance between treatment and control groups, indicating increased partitioning of fat to body tissue reserves. Feeding fats decreased milk protein percentage, but results were heterogeneous. An increased number of milkings increased the milk protein percentage, whereas the difference between the treatment and control groups in duodenal concentrations of 18:2 fatty acids and dietary Mg concentration reduced the milk protein percentage. None of the fat treatments influenced milk protein production. The range of responses to different fats fed approached or exceeded 5 standard deviations from the mean and differed in point direction for all variables studied, indicating the varied and profound biological effects of fats. Responses to fat feeding were highly heterogeneous for all variables studied and heterogeneity was present within responses to individual fat groups. The lower DMI combined with higher milk and milk fat production showed that fats could improve the efficiency of milk production. More studies are required to more completely characterize sources of variation in responses to fats.

Effects of grain, fructose, and histidine on ruminal pH and fermentation products during an induced subacute acidosis protocol

The effects of grain, fructose, and histidine on ruminal pH and fermentation products were studied in dairy cattle during an induced subacute acidosis protocol. Thirty Holstein heifers were randomly allocated to 5 treatment groups: (1) control (no grain); (2) grain [fed at a crushed triticale dry matter intake (DMI) of 1.2% of body weight (BW)]; (3) grain (0.8% of BW DMI)+fructose (0.4% of BW DMI); (4) grain (1.2% of BW DMI)+histidine (6 g/head); and (5) grain (0.8% of BW DMI)+fructose (0.4% of BW DMI)+histidine (6 g/head) in a partial factorial arrangement. Heifers were fed 1 kg of grain daily with ad libitum access to ryegrass silage and alfalfa hay for 10 d. Feed was withheld for 14 h before challenge day, on which heifers were fed 200 g of alfalfa hay and then the treatment diets immediately thereafter. Rumen samples were collected 5 min after diet ingestion, 60 min later, and at 3 subsequent 50-min intervals. Grain decreased ruminal pH and increased ammonia, total volatile fatty acid (VFA), acetate, butyrate, propionate, and valerate concentrations compared with controls. The addition of grain had no effect on ruminal D- and L-lactate concentrations. Fructose markedly decreased ruminal pH and markedly increased D- and L-lactate concentrations. Fructose increased total VFA and butyrate and decreased valerate concentrations. Although histidine did not have a marked effect on ruminal fermentation, increased concentrations of histamine were observed following feeding. This study demonstrates that the substitution of some grain for fructose can lower ruminal pH and increase VFA and lactate concentrations, warranting further investigation into the role of sugars on the risk of acidosis in dairy cattle.

Effects of necrotic enteritis challenge on intestinal micro-architecture and mucin profile

1. This study investigated the effect of Eimeria spp./Clostridium perfringens induced necrotic enteritis and traditional antibiotic preventatives on intestinal micro-architecture and mucin profile. 2. A total of 600 Cobb 500 broiler chickens were randomly assigned to the following three groups: (i) unchallenged, (ii) challenged, and (iii) zinc bacitracin/monensin (ZnB/monensin) (n = 25 chickens/pen, 8 pens/group). The challenged and ZnB/monensin chickens were individually inoculated with Eimeria acervulina, E. maxima and E. tenella and C. perfringens type A (EHE-NE18) at 9 and 15 d post-hatch respectively, to induce necrotic enteritis. 3. The challenge procedure significantly decreased villus height, increased villus width and increased crypt depth in the challenged compared to the unchallenged chickens. Zinc bacitracin and monensin maintained villus-crypt structure similar to that of the unchallenged chickens. 4. Mucin profile was not affected by Eimeria spp./C. perfringens challenge as demonstrated by periodic acid-Schiff and high iron diamine-alcian blue pH 2 x 5 staining. Zinc bacitracin and monensin decreased the number of intestinal mucin-containing goblet cells. 5. Lectin histochemistry showed a trend towards greater Arachis hypogea (PNA) reactivity in unchallenged chickens. 6. In summary, Eimeria spp./C. perfringens challenge disrupted intestinal micro-architecture; however, challenge did not appear to affect intestinal mucin profile. Traditional antibiotics, zinc bacitracin and monensin maintained micro-architecture.