Effects of bacterial direct-fed microbials on ruminal characteristics,methane emission,and milk fatty acid composition in cows fed high- or low-starch diets

This study investigated the effects of bacterial direct-fed microbials (DFM) on ruminal fermentation and microbial characteristics, methane (CH₄) emission, diet digestibility, and milk fatty acid (FA) composition in dairy cows fed diets formulated to induce different ruminal volatile fatty acid (VFA) profiles. Eight ruminally cannulated dairy cows were divided into 2 groups based on parity, days in milk, milk production, and body weight. Cows in each group were fed either a high-starch (38%, HS) or a low-starch (2%, LS) diet in a 55:45 forage-to-concentrate ratio on a dry matter (DM) basis. For each diet, cows were randomly assigned to 1 of 4 treatments in a Latin square design of (1) control (CON); (2) Propionibacterium P63 (P63); (3) P63 plus Lactobacillus plantarum 115 (P63+Lp); (4) P63 plus Lactobacillus rhamnosus 32 (P63+Lr). Strains of DFM were administered at 10¹⁰ cfu/d. Methane emission (using the sulfur hexafluoride tracer technique), total-tract digestibility, dry matter intake, and milk production and composition were quantified in wk 3. Ruminal fermentation and microbial characteristics were measured in wk 4. Data were analyzed using the mixed procedure of SAS (SAS Institute Inc., Cary, NC). The 2 diets induced different ruminal VFA profiles, with a greater proportion of propionate at the expense of acetate and butyrate for the HS diet. Greater concentrations of total bacteria and selected bacterial species of methanogenic Archaea were reported for the HS diet, whereas the protozoa concentration in HS decreased. For both diets, bacterial DFM supplementation raised ruminal pH (+0.18 pH units, on average) compared with CON. Irrespective of diet, P63+Lp and P63+Lr increased ruminal cellulase activity (3.8-fold, on average) compared with CON, but this effect was not associated with variations in ruminal microbial numbers. Irrespective of diet, no effect of bacterial DFM on ruminal VFA was observed. For the LS diet, supplementing cows with P63+Lr tended to decrease CH₄ emission (26.5%, on average, when expressed per kilogram of milk or 4% fat-corrected milk). Only P63 supplementation to cows fed the HS diet affected the concentration of some milk FA, such as cis isomers of 18:1 and intermediates of ruminal biohydrogenation of polyunsaturated FA. Overall, bacterial DFM could be useful to stabilize ruminal pH. Their effects on CH₄ production mitigation and milk FA profile depended on DFM strain and diet and should be confirmed under a greater variation of dietary conditions.     

Factors influencing dairy calf and replacement heifer mortality in France

Herd-level risk factors for dairy calf and heifer mortality in France were identified by calculating herd-level variables (including mortality risk or rate) using the National Bovine Identification Database (2005 and 2006). Eleven dairy production areas representing different livestock systems were also included. Statistical analyses were based on a probit model (mortality risk or rate = 0 or >0) and a linear model (mortality risk or rate >0) corrected by the sample bias Heckman method. The same associations were reported for 2005 and 2006. The mortality risks or rates for calves and heifers were positively associated with the proportion of purchased cows or being a Milk Control Program member and negatively associated with adhering to the Good Breeding Practices charter and having an autumn calving peak. The associations between mortality and the breeds or the production areas were positive or negative, depending on the classes of animal. Mortality and having a beef herd in addition to the dairy herd were negatively associated for noncrossed birth to 2-d-old calves, noncrossed 3-d- to 1-mo-old calves, and 3-d- to 1-mo-old heifers. Having a beef herd probably provides specific know-how related to newborn and young calf management that makes it easier to attain low mortality in pure-breed dairy calves. The proportion of males born was positively associated with mortality for the birth to 2-d-old calves (all classes) and for the 3-d- to 1-mo-old beef-crossed calves, but negatively for all classes of heifers. This indicates that heifer management was improved when the availability of newborn heifers decreased, resulting in low mortality. This lower mortality is apparent for all classes of heifers present on the farm during the year when the proportion of males was low, and demonstrates an anticipatory effect. In conclusion, this study shows that the presence of a beef herd in addition to the dairy herd within a farm is associated with decreased dairy calf mortality. It also shows that heifer mortality decreases when the proportion of heifers born decreased. These determinants of dairy calf and heifer mortality are of great importance for farmer advisors, the dairy industry, and the political decision makers.     

Holstein-Friesian calves selected for divergence in residual feed intake during growth exhibited significant but reduced residual feed intake divergence in their first lactation

Residual feed intake (RFI), as a measure of feed conversion during growth, was estimated for around 2,000 growing Holstein-Friesian heifer calves aged 6 to 9 mo in New Zealand and Australia, and individuals from the most and least efficient deciles (low and high RFI phenotypes) were retained. These animals (78 New Zealand cows, 105 Australian cows) were reevaluated during their first lactation to determine if divergence for RFI observed during growth was maintained during lactation. Mean daily body weight (BW) gain during assessment as calves had been 0.86 and 1.15 kg for the respective countries, and the divergence in RFI between most and least efficient deciles for growth was 21% (1.39 and 1.42 kg of dry matter, for New Zealand and Australia, respectively). At the commencement of evaluation during lactation, the cows were aged 26 to 29 mo. All were fed alfalfa and grass cubes; it was the sole diet in New Zealand, whereas 6 kg of crushed wheat/d was also fed in Australia. Measurements of RFI during lactation occurred for 34 to 37 d with measurements of milk production (daily), milk composition (2 to 3 times per week), BW and BW change (1 to 3 times per week), as well as body condition score (BCS). Daily milk production averaged 13.8 kg for New Zealand cows and 20.0 kg in Australia. No statistically significant differences were observed between calf RFI decile groups for dry matter intake, milk production, BW change, or BCS; however a significant difference was noted between groups for lactating RFI. Residual feed intake was about 3% lower for lactating cows identified as most efficient as growing calves, and no negative effects on production were observed. These results support the hypothesis that calves divergent for RFI during growth are also divergent for RFI when lactating. The causes for this reduced divergence need to be investigated to ensure that genetic selection programs based on low RFI (better efficiency) are robust.     

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

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

Induced lactation in heifers: Effects of dexamethasone and age at induction on milk yield and composition

Milk production in heifers induced into lactation is lower than that of postpartum primiparous cows. A method to improve milk production in induced lactations may provide opportunities for increased profitability as well as increase our understanding of the mechanisms that regulate mammary gland development and colostrum composition. The present study was conducted to determine if dexamethasone administration at the onset of milking or age at lactation induction would affect milk production in heifers induced into lactation. Holstein heifers at 14 [n = 20; 354 ± 38 kg of body weight (BW)] and 18 mo of age (n = 20; 456 ± 30 kg of BW) were assigned randomly to dexamethasone (DEX) or control (CON) treatment groups in a 2× 2 factorial arrangement with age and dexamethasone treatment as the 2 factors. Heifers were induced into lactation with daily subcutaneous injections of estradiol-17β and progesterone (0.075 and 0.25 mg/kg of BW per d, respectively) on experimental d 1 to 7. They also received bovine somatotropin (bST) every 14 d beginning on experimental d 1. Milking began on experiment d 18 (lactation d 1). Dexamethasone (10 mg) was administered on lactation d 1 and 2 following the morning milking; CON heifers did not receive dexamethasone. Milk yield from d2 to 15 of lactation of heifers receiving DEX (7.8 kg/d) was greater than that of CON heifers (6.0 kg/d) but was similar thereafter through 305 d of lactation (18.2 kg/d). Milk production to d 11 was similar for 14- and 18-mo-old heifers but was greater for 18- (18.9 kg/d) than for 14-mo-old animals (17.4 kg/d) through 305 d in milk. Milk fat percentage increased initially and was greater in DEX (4.51%) compared with CON (3.53%) heifers until 21 d in milk. Milk protein and lactose concentrations were not affected by DEX treatment. Age at induction did not affect milk fat, protein, or lactose percentages. Mean milk IgG concentration declined from 107.4 mg/mL on d 1 to 5.0 mg/mL on d 7 of lactation, tended to be greater for 18- compared with 14-mo-old heifers, and was not different due to DEX treatment. Administration of DEX to heifers induced into lactation increased initial milk production during the first 2 wk of lactation but this effect did not persist through 305 DIM. Treatment with DEX appeared to stimulate mammary cell differentiation but did not change the rate of decline of milk IgG concentrations. Higher milk yield in 18-mo-old heifers may be due to greater mammary epithelium, higher body mass, or both.     

A screening sampling plan to detect Mycobacterium avium subspecies paratuberculosis-positive dairy herds

Mycobacterium avium ssp. paratuberculosis (MAP) is the etiological agent of paratuberculosis, a chronic contagious bacterial disease primarily affecting dairy cattle. Paratuberculosis represents a dual problem for the milk production chain: in addition to economic losses to affected herds, MAP may have zoonotic potential. Infected herds must be identified in order to implement programs designed to reduce the incidence of disease within and between herds and to prevent MAP from entering the food chain. The objective of this study was to evaluate the sensitivity and specificity of a screening sampling plan (SSP) to detect MAP-positive dairy herds by repetitive analysis of bulk tank milk (BTM) samples by ELISA and in-line milk filter (ILMF) samples by PCR. Samples from BTM and ILMF were collected twice from 569 dairy herds in southern Italy. Additionally, 12,016 individual milk samples were collected: 9,509 from 102 SSP-positive herds (SSP MAP-positive) and 2,507 from 21 randomly selected SSP-negative herds (SSP MAP-negative). There was a total of 126 SSP MAP-positive herds (i.e., 21.3% SSP MAP-positive herds; 95% confidence interval = 18.0–24.9); the within-herd apparent prevalence (AP) ranged between 0.00 and 22.73% (mean 6.07%). A significant difference in within-herd AP was shown between SSP MAP-positive herds and SSP MAP-negative herds. A highly significant association was shown between the median AP herd status (>5%) and positivity to at least one ILMF or BTM sample. The SSP detected a minimum of 56.25% of low AP herds (AP ≤2.0%) up to a maximum of 100% of herds with a within-herd AP ≥8.0%. Overall, the SSP detected 85.57% of herds in which at least one individual milk sample was positive by ELISA. The proposed SSP was an inexpensive and useful tool to detect MAP-positive herds with a higher risk of infection diffusion and milk contamination. Although the SSP cannot be used for MAP-free certification of herds, it could be useful to prioritize appropriate control measures aimed at reducing the prevalence of infection in dairy herds and milk contamination.     

The effect of rearing substrate and space allowance on the behavior and physiology of dairy calves

The objective of this study was to investigate the effect of rearing substrate and space allowance on the behavior and physiology of dairy calves. At 1 wk of age, 72 calves were moved into 1 of 18 experimental pens (n = 4 calves/pen) where they remained until 6 wk of age. Half of the pens had floors covered with quarry stones (QS) and the other half were covered with sawdust (SW). For each substrate type, calves were reared at 1 of 3 space allowances: 1.0, 1.5, or 2.0 m²/calf. Behavior was video-recorded continuously for 24 h in the home pen at 2, 4, and 6 wk of age; the time calves spent lying, standing, walking, and running were estimated using 1-min instantaneous scan sampling. Body weight, cleanliness, fecal fluidity, and skin surface temperature were recorded at 1, 4, and 6 wk of age. Escherichia coli numbers were assessed on the skin surface of the shoulder and in feces of calves at 4 and 6 wk of age. Blood samples were taken at 1, 4, and 6 wk of age to measure cortisol, creatine kinase, immunoglobulin G, serum amyloid A, and total protein concentrations. Calves reared on QS spent less time lying and walking and more time standing at 4 and 6 wk of age compared with calves reared on SW. Furthermore, calves reared at a space allowance of 2.0 m²/calf spent less time lying and more time standing and walking compared with calves reared at a space allowance of 1.0 and 1.5 m²/calf. Calves reared on QS had lower skin surface temperatures compared with calves reared on SW. Fecal fluidity scores were lower in calves reared on QS than SW at 2 wk of age. Fewer E. coli were recovered from the shoulder of calves reared on QS than those of calves reared on SW, but fecal E. coli counts were similar between rearing substrates and space allowances. Serum amyloid A concentrations were lower in calves reared on QS than SW. We detected no effect of rearing substrate or space allowance on body weight, cleanliness, or concentrations of cortisol, creatine kinase, immunoglobulin G, and total protein. In conclusion, lower skin temperature in combination with reduced lying behavior may reflect reduced comfort of calves reared on QS. Furthermore, a space allowance of 2.0 m²/calf may provide calves with more opportunity to perform active behaviors.     

Comparison of selected animal observations and management practices used to assess welfare of calves and adult dairy cows on organic and conventional dairy farms

Differences in adoption of selected practices used in welfare assessment and audit programs were contrasted among organic (ORG; n = 192) herds and similarly sized conventional grazing herds (CON-GR; n = 36), and conventional nongrazing herds (CON-NG; n = 64). Criteria from 3 programs were assessed: American Humane Association Animal Welfare Standards for Dairy Cattle, Farmers Assuring Responsible Management (FARM), and the Canadian Codes of Practice (CCP). Data were collected by trained study personnel during a herd visit and included information about neonatal care, dehorning, pain relief, calf nutrition, weaning, record keeping, use of veterinarians, and animal observations. Associations of management type (ORG, CON-GR, or CON-NG) with adoption of selected practice were assessed. Almost all farms (97%) met criteria suggested for age at weaning but fewer CON-NG farmers weaned calves at ≥5 wk of age compared with ORG and CON-GR farmers. Only 23% of farms met program requirements for use of pain relief during dehorning, and fewer CON-NG farmers used pain relief for calves after dehorning compared with ORG and CON-GR farmers. Calves on ORG farms were fed a greater volume of milk and were weaned at an older age than calves on CON-GR and CON-NG farms. Calves on CON-GR farms were dehorned at a younger age compared with calves on ORG and CON-NG farms. The calving area was shared with lactating cows for a larger proportion of ORG herds compared with conventional herds. About 30% of herds met welfare program criteria for body condition score but only about 20% met criteria for animal hygiene scores. The least proportion of cows with hock lesions was observed on ORG farms. Regular use of veterinarians was infrequent for ORG herds. Results of this study indicate that most of the organic and conventional farms enrolled in this study would have been unlikely to achieve many criteria of audit and assessment programs currently used in the US dairy industry.     

Effects of supplemental progesterone after artificial insemination on expression of interferon-stimulated genes and fertility in dairy cows

The objectives of the current study were to evaluate the effects of supplemental progesterone after artificial insemination (AI) on expression of IFN-stimulated genes (ISG) in blood leukocytes and fertility in lactating dairy cows. Weekly cohorts of Holstein cows were blocked by parity (575 primiparous and 923 multiparous) and method of insemination (timed AI or AI on estrus) and allocated randomly within each block to untreated controls, a controlled internal drug release (CIDR) containing 1.38 g of progesterone from d 4 to 18 after AI (CIDR4), or a CIDR on d 4 and another on d 7 after AI and both removed on d 18 (CIDR4+7). Blood was sampled to quantify progesterone concentrations in plasma and mRNA expression in leukocytes for the ubiquitin-like IFN-stimulated gene 15-kDa protein (ISG15) and receptor transporter protein-4 (RTP4) genes. Pregnancy was diagnosed on d 34 ± 3 and 62 ± 3 after AI. Treatment increased progesterone concentrations between d 5 and 18 after AI in a dose-dependent manner (control = 3.42, CIDR4 = 4.97, and CIDR4+7 = 5.46 ng/mL). Cows supplemented with progesterone tended to have increased luteolysis by d 19 after AI (control = 17.2; CIDR4 = 29.1; CIDR4+7 = 30.2%), which resulted in a shorter AI interval for those reinseminated after study d 18. Pregnancy upregulated expression of ISG in leukocytes on d 19 of gestation, but supplementing progesterone did not increase mRNA abundance for ISG15 and RTP4 on d 16 after insemination and tended to reduce mRNA expression on d 19 after AI. For RTP4 on d 19, the negative effect of supplemental progesterone was observed only in the nonpregnant cows. No overall effect of treatment was observed on pregnancy per AI on d 62 after insemination and averaged 28.6, 32.7, and 29.5% for control, CIDR4, and CIDR4+7, respectively. Interestingly, an interaction between level of supplemental progesterone and method of AI was observed for pregnancy per AI. For cows receiving exogenous progesterone, the lower supplementation with CIDR4 increased pregnancy per AI on d 62 in cows inseminated following timed AI (CIDR4 = 39.2; CIDR4+7 = 27.5%); in those inseminated following detection of estrus, however, the use of a second insert on d 7 resulted in greater pregnancy per AI (CIDR4 = 26.9; CIDR4+7 = 31.5%). Pregnancy loss did not differ among treatments. Supplemental progesterone post-AI using a single intravaginal insert on d 4 was beneficial to pregnancy in cows inseminated following timed AI, but incremental progesterone with a second insert on d 7 did not improve fertility of dairy cows.     

Study of progesterone and cortisol concentrations in the Italian Friesian claw

The present research was conducted to study progesterone and cortisol concentrations in the claw of cattle and to verify whether the cattle claw could be considered an efficient matrix to provide retrospective information regarding progesterone and cortisol concentrations related to pregnancy and peripartum periods. These 2 steroids are involved in hoof growth. The study was performed on 32 calves and 24 pregnant milking cows of the Holstein breed, which were clinically healthy and lacking any claw disorders. Samples of at least 0.5 cm in thickness were taken from the sole. Progesterone and cortisol concentrations were determined by RIA. The cortisol concentration in the horny shoe of calves from 0 to 30 d of age was significantly higher than the concentration at 31 to 60 and 61 to 120 d of age. Conversely, the progesterone concentration showed no statistically significant difference in relation to age. The horn progesterone concentrations recorded in the milking dairy cows at 7 mo of pregnancy showed high variability in the horizontal sections of the sole (the individual coefficient of variation ranged between 0.09 and 1.11). In 6 cows, genuine extreme values (genuine outliers) of the progesterone level were found. Moreover, significant differences existed among the progesterone concentrations of the sole's transverse sections. We detected a significant positive correlation between the weight of the horn samples after freeze-drying and their weight after hydration. The cortisol and progesterone levels in soaked horn samples were found to be significantly lower than in the same dry samples. These results show that cortisol and progesterone can be measured in the cattle claw horn. The claws of mature dairy cows could not be used as a matrix to provide a retrospective measure of cumulative hormone secretion, whereas the analysis of the calves’ claw horns showed retrospective hormonal information similar to hair samples.