Farm-level nutritional factors associated with milk production and milking behavior on Canadian farms with automated milking systems.

The objective of this study was to describe nutritional strategies utilized on Canadian dairy farms with automated milking systems (AMS), both at the feed bunk and the concentrate offered at the AMS, as well as to determine what dietary components and nutrients, as formulated, were associated with milk production and milking behaviors on those farms. Formulated diets, including ingredients and nutrient content, and AMS data were collected from April 1, 2019, until September 30, 2020, on 160 AMS farms (Eastern Canada [East] = 8, Ontario [ON] = 76, Quebec [QC] = 22, and Western Canada [West] = 54). Both partial mixed ration (PMR) and AMS concentrate samples were collected from May 1 to September 30, 2019, on 169 farms (East = 12, ON = 63, QC = 42, West = 52). AMS milking data were collected for 154 herds. For each farm (n = 160), milk recording data were collected and summarized by farm to calculate average milk yield and components. Multivariable regression models were used to associate herd-level formulated nutrient composition and feeding management practices with milk production and milking behavior. Milk yield (37.0 ± 0.3 kg/d) was positively associated with the PMR ether extract (EE) concentration (PMR % EE; +0.97 kg/d per percentage point (p.p.) increase) and with farms that fed barley silage as their major forage source on farm (n = 16; +2.18 kg/d) compared with haylage (n = 42), while farms that fed corn silage (n = 96; +1.23 kg/d) tended to produce more milk than farms that fed haylage. Greater milk fat content (4.09 ± 0.28%) was associated with greater PMR-to-AMS concentrate ratio (+0.02 p.p. per unit increase) and total diet net energy for lactation (+0.046 p.p. per 0.1 Mcal/kg increase), but lesser % non-fiber carbohydrates (NFC) of the PMR (-0.016 p.p. per p.p. increase of % NFC). Milk protein content (3.38 ± 0.14%) was positively associated with forage % of the PMR (+0.003 p.p. per p.p. increase of % forage) and total diet % starch (+0.009 p.p. per p.p. increase of % starch), but negatively associated with farms feeding corn silage (-0.1 p.p. compared with haylage) as their major forage. Greater milking frequency (2.77 ± 0.40 milkings/d) was observed on farms with free-flow cow traffic systems (+0.62 milkings/d) and positively associated with feed push-up frequency (+0.013 milkings/d per additional feed push-up), while being negatively associated with PMR NFC content and % forage of the total ration (-0.017 milkings/d per p.p. increase of % forage). Lastly, greater milking refusal frequency (1.49 ± 0.82 refusals/d) was observed on farms with free-flow cow traffic systems (+0.84 refusals/d) and farms feeding barley silage (+0.58 refusals/d) than guided flow and farms feeding either corn silage or haylage, respectively. These data give insight into the ingredients, nutrient formulations and type of diets fed on AMS dairy farms across Canada and the association of those factors with milk production and milking behaviors.

Effect of pre- and postpartum supplementation of a pure glycerol product to dairy cows on feeding behavior, lying behavior, and reticulorumen pH.

The objective of this study was to quantify the effects of supplementing a low level of dry glycerol product pre- and postpartum on the feeding behavior, lying behavior, and reticulorumen pH of dairy cows. Multiparous Holstein dairy cows (n = 60) were enrolled in a 2 × 2 factorial design study. Twenty-one days before expected parturition, cows individually received a dry cow diet with (1) 250 g/d glycerol supplementation (GLY; 66% pure glycerol, United States Pharmacopeia grade), or (2) no supplementation (CON). Following parturition, cows were individually assigned to either (1) 250 g/d glycerol product (GLY; 66% pure glycerol), or (2) no supplementation (CON) to their partial mixed ration (PMR) for the first 21 d in milk (DIM). All cows were milked by an automated milking system and offered a target of 5.4 kg/d pellet (23% of target total dry matter intake [DMI]). For both treatment periods, cows were individually assigned to automated feed bins to measure PMR feeding behavior. Rumination time and lying behavior were monitored with electronic sensors for the whole study (-21 to 21 DIM). Reticulorumen pH boluses were administered to a subset of cows (n = 40) where pH was recorded every 10 min from 21 d prepartum to 21 d postpartum. Prepartum, cows fed GLY had fewer, larger meals and spent 20.2% more time feeding than CON while consuming feed at a similar rate. Cows on the CON diet prepartum spent more time lying down in more frequent bouts in the 21 d before calving. Following parturition, cows that received GLY prepartum continued to devote more time to eating, while tending to spend less time ruminating per kilogram of DMI. Cows receiving CON postpartum had larger meals with longer intervals between meals. In the first 21 DIM, cows receiving CON prepartum tended to have shorter, but significantly more frequent, lying bouts than cows fed GLY prepartum. Glycerol supplementation pre- and postpartum resulted in less time spent lying down following parturition. Minimal differences between treatments were observed for pre- and postpartum sorting behavior or reticulorumen pH. Overall, supplementation of glycerol pre- and postpartum altered cow time budgets, with cows spending more time eating pre- and postpartum, less time lying pre- and postpartum, and having fewer, larger meals prepartum when receiving glycerol prepartum, and with cows having slower feeding rates and smaller meals following parturition with postpartum glycerol supplementation.

Effect of pre- and postpartum supplementation of a pure glycerol product to dairy cows on feed intake, metabolic markers, and milk yield and components.

The objective of this study was to quantify the effects of supplementing transition dairy cows with a low inclusion dry glycerol product in the pre- and postpartum periods on feed intake, metabolic markers, and milk yield and components. Multiparous Holstein dairy cows (n = 60) were enrolled in a 2-by-2 factorial design study. Starting 21 d before expected parturition, cows individually received a dry cow diet with (1) 250 g/d glycerol product supplementation [66% pure glycerol (United States Pharmacopeia grade); GLY], or (2) no supplementation (CON) mixed to their total mixed ration. After parturition, cows, again, were individually assigned to either GLY, or (2) no supplementation (CON) to their partial mixed ration for the first 21 d in milk (DIM). Cows were milked by an automated milking system and offered a target of 5.4 kg DM/d pellet (23% of target total dry matter intake, DMI) in the automated milking system and followed for 42 d into lactation. Blood samples were collected 6.3 ± 3.47 d before calving for all blood measures and 3, 7, 10, and 14 DIM for analysis of glucose and ß-hydroxybutyrate, as well as 3 and 7 DIM for nonesterified fatty acids (NEFA) and haptoglobin. Initial dry cow body weight (BW), calf birth weight, previous 305-d milk, and month of parturition were used as covariates in the statistical model. Cows supplemented with GLY prepartum lost less BW and consumed more DMI pre- and postpartum, as well as had lower postpartum blood ß-hydroxybutyrate and NEFA concentrations compared with those fed the CON treatment prepartum. Cows supplemented with GLY postpartum had lesser DMI in the first 42 DIM than cows fed CON postpartum, but also had reduced blood NEFA concentrations, odds of a high haptoglobin test, odds of a low blood glucose test, and lesser preformed fatty acid concentrations and yields in their milk. Cows supplemented glycerol both pre- and postpartum lost the least total BW from -21 to 21 DIM. No treatment effects were detected for milk yield; however, cows receiving GLY postpartum had lower milk fat. Overall, glycerol supplementation during the transition period, particularly during the 21 d before calving, was associated with markers of improved metabolic status.

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 of parity with health disorders and blood metabolite concentrations in Holstein cows in different production systems.

Data were obtained from studies in Australia, Canada, and the United States using individual cow data from 28,230 Holstein cows to evaluate associations between parity and disease. Our goal was to develop understanding of disease risks for cows of differing parity. We hypothesized that there would be increased risks of disease and changes in metabolite concentrations with increased parity. Parity ≥5 represented 2,533 cows or 9.0%, parity 4 was 9.8% (2,778), parity 3 as 19.0% (5,355), parity 2 as 28.1% (7,925), and parity 1 was 34.1% (9,639) of the sample. Of these cows, 15.5% were in Australia, 14.7% in Canada, and 69.8% in the United States. Lactational incidence (LI) risk of clinical hypocalcemia increased with parity from 0.1% for parity 1 to 13% for parity ≥5 cows. The marked increase suggests profound differences in metabolism with increased parity. The LI of clinical mastitis was 17.4%. The odds of mastitis increased with parity to 2.5 times greater in parity ≥5 than in parity 1. The LI of lameness increased with parity; specifically, the odds of lameness was 5.6 times greater for parity ≥5 than parity 1. Dystocia incidence was 8.7% and greatest for parity 1 cows. The LI of retained placenta was 7.4% and increased with parity, with the odds for parity ≥5 2.3 times greater than for parity 1. The LI of metritis was 10% and of endometritis 14%, with the greatest odds in parity 1. The LI of clinical ketosis was 3.3% with a marked increase in odds with parity. The prevalence of subclinical ketosis was 26.8% with only cows in parity 1 having lower odds than other parities. Parity ≥5 cows had greater odds (odds ratio = 1.7) of respiratory disease than parity 1 cows, which were lesser than other parities. Metabolite concentrations were evaluated in 5,154 Holstein cows in the precalving, calving, and immediate postcalving data sets. Metabolic measures near peak lactation provided 1,906 observations. Concentrations of ß-hydroxybutyrate (BHB) and nonesterified fatty acids increased with parity on d 1 to 3 of lactation and at peak lactation. On d 1 to 3 after calving differences in glucose, nonesterified fatty acids, and BHB indicated a greater reliance on mobilized lipid to export energy to peripheral tissues as BHB for greater parity cows. Differences in concentrations among parity groups were marked at times, for example >0.20 mM in Ca for parity 1 and 2 to parity ≥5 and >0.33 mM for all older parities compared with parity 1 for P on the day of calving. The marked increase suggests profound differences in metabolism with increased parity are probably influenced, in part, by increased production. We found marked differences in concentrations of metabolites with parity that are consistent with reduced reproduction, health, and body condition for higher parity cows. These unfavorable differences in metabolism in Ca, P, glucose, and cholesterol concentrations for higher parity cows also complement the often-substantial differences in disease risk with parity and suggest a need to carefully consider the parity structure in study design. Managers and advisors will need to consider methods to reduce risk of health disorders tailored to cows of different ages.

Increased parity is negatively associated with survival and reproduction in different production systems.

We conducted a retrospective meta-analysis based on individual cow data to assess the associations of parity, level of production, and pasture-based or intensively fed systems with fertility. Our goal was to provide understandings of the role of parity in risks for removal and reproductive failure. Multilevel models were used to evaluate the fixed effects of parity, milk, milk solids, milk fat and protein percentage and yield, and production system [intensively fed (n = 28,675) or predominantly pasture fed (n = 4,108)] on reproductive outcomes. The outcomes were the hazard of not being bred (HNBRED), hazard of pregnancy (HPREG), pregnancy to first breeding (PREG1), and odds of becoming pregnant in a lactation (OPAL). The 32,783 cows were in 13 studies conducted in Australia (14.6% of cows), Canada (2.4% of cows), and the United States (83.0% of cows). There were 38.5% of cows in the sample in parity 1, 27.3% in parity 2, 16.7% in parity 3, 9.0% in parity 4, and 8.6% in parity ≥5. Compared with cows of parity 1, parity ≥5 cows had a greater HNBRED [hazard ratio (HR) = 2.45], lesser HPREG (HR = 0.73), and reduced OPAL (odds ratio = 0.36). However, the parity ≥5 cows had similar PREG1 to other parities except for parity 1. This suggests the possibility of a higher proportion of subfertile parity ≥5 cows than for other parities. Associations between parity and reproductive measures were influenced by the different milk production measures, indicating that milk yield and milk component percentages and yields modified the odds or hazards of successful reproduction. All milk production measures had quadratic associations with OPAL, indicating that either low or high production or concentration of solids within a cohort reduced OPAL. This reduced OPAL reflected a greater HNBRED for lower milk yield and milk protein and fat yielding cows. Both milk yield and milk protein percentage had quadratic associations with HPREG. When centered milk yield was categorized into quartiles, small differences in HPREG existed. A more marked association of milk protein percentage occurred with HPREG, with optimal HPREG at approximately 0.5% above group mean milk protein percentage. Milk fat percentage (HR = 0.901), fat yield (kg/d; HR = 0.78), protein yield (kg/d; HR = 0.71), and milk solids yield (kg/d; HR = 0.84) were all linearly associated with reduced HPREG. Difference in production systems did not have substantive effects on PREG1 but did for HNBRED, HPREG, and OPAL. Estimates of associations of parity with reproductive outcomes HNBRED, HPREG, and OPAL were influenced by milk and milk solids yield; older cows had markedly lower reproductive outcomes. Interestingly, for PREG1, there were few differences among parities and differences were less influenced by milk yield and constituent measures. The marked associations of parity with removal for all reasons, deaths and culling, and reductions in HNBRED, HPREG, and OPAL indicate a need to focus on the physiological changes with parity to produce better strategies to support optimal longevity of cows.

Holstein dairy cows lose body condition score and gain body weight with increasing parity in both pasture-based and total mixed ration herds.

Body condition scoring (BCS) and body weight (BW) are observations associated with labile tissue reserves, health, and reproduction efficiency of dairy cows. The effect of parity (1 through to ≥5) and feeding system (pasture-based and TMR) on BCS and BW were evaluated utilizing raw data sets from 16 retrospective studies that totaled 24,807 Holstein cows across 3 nations (Australia, Canada, and the United States). Linear regression models were used to investigate the 5 outcome variables of precalving BCS, peak milk BCS, change in BCS from precalving to peak milk, and peak milk BW and their respective associations with parity and feeding system. To help control for the influence of calendar time, study treatment protocols when applicable, and genetic change, all outcome variables were center-transformed around each study group mean. Including feeding system as a covariate improved model fit for most outcome variables; however, the relative effect size of parity was generally much greater than feeding system effect size. Parity 2 cows had the lowest precalving BCS of -0.087 [95% confidence interval (CI): -0.107, -0.065] less than the mean, whereas parity 1 cows had the greatest, 0.068 (95% CI: 0.043, 0.092) above mean, regardless of feeding system. Peak milk BCS overall decreased with increasing parity (parity 1 to parity ≥5: -0.13, 95% CI: -0.19, -0.08) and BCS change during the transition period monotonically decreased with increasing parity (parity 1 to parity ≥5: -0.22, 95% CI: -0.26, -0.17). Peak milk BW monotonically increased with increased parity (parity 1 to parity ≥5: 114 kg, 95% CI: 104, 125). A waffle plot was used to present the proportions of cows, by parity, that were partitioned into "low BCS and low BW," "low BCS and high BW," "high BCS and low BW," or "high BCS and high BW" groups. Cows were assigned either a high or low status by being above or below their specific centered study group means, respectively. Considering a null hypothesis of 25% per BCS-BW category, there was a striking change in category from parity 1 cows that were predominantly in the "high BCS and low BW" category (61.2%) to parity ≥5 cows that were predominantly in the "low BCS and high BW" category (55.5%). The study supports studies showing increased weight and change in BCS with increased parity. We highlight the associations among production system, BCS, BW, and parity.

Navel healing in male and female Holstein calves over the first 14 days of life: A longitudinal cohort study.

The objectives of this study were (1) to describe navel healing in male and female neonatal Holstein calves over a 14-d observation period, and (2) to determine the associations of dam parity, calving factors, and calf factors with navel measurements and time to healing. A total of 68 Holstein calves (43 female and 25 male) were enrolled. Navel healing outcomes (cessation of navel discharge, navel cord remnant drying, navel cord remnant drop-off) and navel stump measurement outcomes (proximal diameter, distal diameter, length) were recorded every 24 ± 1 h for a 14-d observation period. Data were also collected for dam parity, calving factors (time of birth, calving ease), and calf factors (calf sex, calf vitality at birth, birth weight, average daily gain, serum total protein, and medical treatment or treatments). The mean time to navel cord remnant drying was 2 d, and all calves had dry navels by d 5. A total of 56% of calves retained their navel cord remnant beyond the end of the observation period, and calves began to shed their navel cord remnants as early as d 2. In addition, at least once during the observation period, 85% of calves had a proximal navel diameter measurement over a 13-mm threshold recently proposed to identify navel infections. For distal navel diameter measurements, 72% of calves had a diameter over the 13-mm threshold at least once during the observation period. No associations were identified between navel healing outcomes and dam, calving, and calf factors. Navel measurement outcomes were associated with calving and calf factors. Specifically, proximal navel stump diameter was associated with the day of observation (decreased from d 5 to 14), calf sex (smaller in female calves), time of birth (larger in calves born overnight or unobserved, compared with the morning), and birth weight (larger in birth weights >44.1 kg compared with <38.5 kg). Distal navel stump diameter was associated with calf sex, medical treatment, and day of observation; however, we observed an interaction between sex and day of observation (larger in male calves on d 3 to 7, d 9, and d 12, compared with female calves), and sex and medical treatment (larger in untreated male calves, no difference between treated male and female calves). Navel stump length was associated with time of birth (longer in calves born overnight or unobserved compared with any other time) and the interaction of birth weight and day of observation (longer in birth weights >44.1 kg compared with 38.6-41.5 kg on d 3, 8-10, and 13, and 41.6-44.0 kg on d 3, 5, 7-8, and 13). The wide range in time to navel cord remnant drying and drop-off suggest that these measures may not be adequate indicators of calf age on their own. More research on navel healing is required to improve our understanding of factors that influence navel measurements and time to healing, as well as how this information could be used in an objective assessment of navel health.

An investigation of blood, milk, and urine test patterns for the diagnosis of ketosis in dairy cows in early lactation.

Ketosis in dairy cattle is primarily diagnosed based on the concentrations of ketone bodies in the blood, milk, or urine. Cow-side tests using these fluids are available for rapid detection of elevated concentrations of ketone bodies. Although these tests have been extensively validated, the performance of different tests has not been compared over time. Our objectives were to investigate the relationship between point-of-care diagnostic tests measuring the concentrations of ß-hydroxybutyrate (BHB) in blood (BT; Precision Xtra, Abbott Laboratories), BHB in milk (MT; Keto-Test, Elanco), and acetoacetate (AcAc) in urine (UT; Ketostix, Bayer Corporation) through cases of ketosis. Holstein cows (n = 148) were screened daily for hyperketonemia (HYK; blood BHB ≥1.2 mmol/L) from 3 to 16 d in milk (DIM); moreover, milk and urine samples were collected concomitantly and tested for ketones (ketosis thresholds: 100 µmol/L milk BHB and 5 mg/dL urine AcAc). Of the animals screened (n = 148), 74% were diagnosed with HYK. When diagnosed with HYK, cows were treated with propylene glycol orally once daily for 5 d. After the day of diagnosis (d 0), hyperketonemic cows were retested with BT, MT, and UT for 3 d (d 1, 2, and 3). We assessed the diagnostic test performance and time to ketosis (survival analyses and Cox proportional hazards models) of MT and UT compared with BT. Considering all paired samples (before and after diagnosis of HYK), MT had 61% sensitivity and 91% specificity, whereas the UT had 77% sensitivity and 94% specificity compared with BT. The specificity of MT and UT increased from d 0 to d 1, decreased on d 2, and increased on d 3. The median time to diagnosis of ketosis in blood was 5 DIM (95% CI 5 to 7 DIM); moreover, MT and UT had 2 d greater median time to diagnosis of ketosis compared with the BT [7 DIM (6 to 11 d); and 7 DIM (6 to 13 d), respectively]. We concluded that the UT is a more sensitive predictor of blood BHB concentration than the MT. The UT and MT tests diagnosed ketotic cows approximately 2 d later than the BT. The possible consequences of delay in detection of ketosis in milk and urine should be investigated.

A scoping review of the analytical literature concerning nonambulatory dairy cattle.

Nonambulatory dairy cattle pose a complex problem due to the challenges associated with prevention, appropriate treatment and management, and arriving at an accurate prognosis. There is a breadth of literature regarding this topic, of which there is currently no formal synthesis. The objective of this scoping review was to describe and characterize the literature investigating risk factors, sequela, preventions, treatments, and prognostic factors for nonambulatory conditions in dairy cattle, with the intent of qualitatively synthesizing knowledge of the topic and identifying gaps in the literature. A literature search was conducted in 6 databases and 2 conference proceeding archives, which returned 7,568 unique articles. Initial screening of abstracts resulted in 1,544 articles reviewed at the full-text stage, of which 379 were included for data extraction. Over 75% of the included literature was published after 1980, and the most common countries in which these studies took place were the United States (n = 72), Canada (18), Sweden (17), and Germany (17). Common eligibility criteria used for inclusion were geographic region (97) and parity (92). Of the 379 studies included in this review, 144 were randomized controlled trials and 235 were observational studies. The majority of the controlled trials assessed prevention of nonambulatory conditions (116), most commonly through supplementation of vitamin D (27) and calcium (25) or the provision of anionic salts (22). Of the 28 studies focusing on treatment of nonambulatory conditions, 26 focused on calcium administration. Becoming nonambulatory was evaluated as an outcome in 165 of the observational studies. Frequently measured risk factors for becoming nonambulatory included hematological variables, such as blood calcium (73), phosphorus (53) and magnesium (42), and other factors such as parity (35) and breed (22). Recovery from a nonambulatory condition was the outcome in 31 of the observational studies, with commonly measured prognostic indicators being calcium (9), phosphorus (9), and duration of recumbency (7). Nonambulatory disorders were measured as risk factors in 53 of the observational studies, with the most commonly assessed outcomes including disorders of the transition period (11), and death or euthanasia (11). The most common terms used to describe nonambulatory conditions were "milk fever" (199) and "parturient paresis" (147). These terms were only further defined with explicit symptomatic criteria in 193 of the 379 studies in this review. Recumbency was the most commonly used of these criteria (144), followed by inability to rise (55). Potential gaps in the literature concerning nonambulatory dairy cattle that were identified in the present review included investigation of prognostic indicators for recovery from nonambulatory conditions that are applicable on farm, treatment alternatives to calcium administration, and guidance regarding the appropriate usage of terms meant to categorize nonambulatory dairy cattle.

Reducing milking frequency from twice to once daily as an adjunct treatment for ketosis in lactating dairy cows-A randomized controlled trial.

This randomized controlled trial investigated the effects of temporarily reducing milking frequency (MF) on the resolution of ketosis and milk production in dairy cows in early lactation. To detect ketosis [blood ß-hydroxybutyrate (BHB) ≥1.2 mmol/L], Holstein cows were screened daily from 3 to 16 d in milk using a cow-side meter. Cows diagnosed with ketosis (n = 104) were randomly assigned to twice-daily milking (TDM) or reduced to once-daily milking (ODM) for 2 wk, then returned to twice-daily milking. Both treatment groups received a 5-d treatment of an oral propylene glycol drench (PG; 300 g) beginning on the afternoon of the diagnosis; cows received additional 5-d PG treatments if they had a ketotic test result (blood BHB ≥1.2 mmol/L) at least 4 d after finishing the first PG treatment. Blood BHB tests were conducted for the first 3 d after ketosis diagnosis, and then once every 3 d for 21 d of trial (DOT). Milk and milk component data were collected weekly for 15 wk following trial enrollment. The ODM group showed rapidly and markedly decreased blood BHB concentrations (primiparous cows: 1 DOT, 0.92 ODM vs. 1.22 TDM, 15 DOT, 0.55 vs. 0.81 mmol/L; multiparous cows: 1 DOT, 1.01 vs. 1.40, 15 DOT, 0.78 vs. 1.65 mmol/L). In addition, a logistic regression model indicated that ODM cows were less likely to have blood BHB concentrations ≥1.2 mmol/L [primiparous cows: 3 DOT: ODM 1% (95% confidence interval: 0-10%) vs. TDM 43% (30-58%), 15 DOT ODM 0% (0-0.2%) vs. TDM 22% (13-36%); multiparous cows: 3 DOT: ODM 33% (24-44%) vs. TDM 59% (48-69%), 15 DOT ODM 20.9% (13-31%) vs. TDM 64% (53-74%)]. The proportion of ODM cows that required additional treatments of PG were substantially lower than the TDM group (ODM: 39%; TDM: 64%) than the TDM cows during the initial 21-d period. However, during the 2-wk treatment period, cows in the ODM group produced 26% less milk and 25% less energy-corrected milk than the TDM cows. During wk 3 to 15, when all cows were milked twice daily, ODM cows produced less milk (-14%) and energy-corrected milk (-12%) compared with the TDM group. Milk protein percentage was greater, and milk fat percentage and linear score tended to be greater in the ODM group over 15 wk. In conclusion, a 2-wk reduction of MF in ketotic cows from twice to once daily with treatment with PG resolved ketosis and decreased blood BHB concentrations more effectively than treating TDM cows with PG alone. However, the 2-wk MF reduction had immediate and long-term (up to 13 wk after cessation of MF reduction) negative effects on milk production.

Factors influencing how Canadian dairy producers respond to a downer cow scenario.

Understanding how downer cattle are managed allows for the evaluation of strengths and weaknesses in these practices, which is an important step toward improving the care these animals receive. The objective of this cross-sectional study was to analyze factors associated with the care and management of downer cattle by Canadian dairy producers. Data were obtained from the 2015 National Dairy Study, and analysis was limited to the 371 respondents completing the downer cow scenario. The scenario described a downer cow that the producer wanted to keep in their herd but must be moved, and was followed by questions addressing the cow's care and management. Using multivariable logistic regression models, associations between respondent demographics and farm characteristics, and the presence of downer cow protocols, we assessed decisions regarding euthanasia and use of behavioral prognostic indicators. Written downer cow protocols were reported by 18.2% of respondents, 67% indicated that they had a nonwritten protocol, and 14.8% reported that they did not have a protocol (either written or nonwritten). Respondents from western provinces were more likely to have a written protocol than those from Ontario. Nineteen percent of the respondents with a written or unwritten protocol reported veterinary involvement in developing their downer cow protocol, which occurred more commonly on farms with more frequent herd health visits and a good producer-veterinarian relationship. An area to move a downer cow to was present on 88% of farms, with respondents who were farm staff being less likely to report having knowledge of a designated area than respondents who were the farm owner. In addition, approximately half (45%) of respondents reported moving downer cattle with hip lifters as their most common method. Behavioral prognostic indicators chosen by respondents were associated with the respondent's geographic region, age, farm size, and education. Most notably, older respondents were more likely to use appetite, and less likely to use attitude, as a prognostic indicator compared with younger respondents. Using perceived pain as a prognostic indicator was more common among respondents from western and Atlantic provinces compared with respondents from Ontario, and more common among respondents with a college or university education. These results highlighted herd and farmer demographics that were associated with how Canadian dairy producers managed downer cattle in 2015 and could be used as a benchmark for evaluating how these management practices compare with those currently implemented.

Farm-level factors associated with lameness prevalence, productivity, and milk quality in farms with automated milking systems.

Impaired locomotion (lameness) may negatively affect the ability and desire of cows to milk voluntarily, which is a key factor in success of automated milking systems (AMS). The objective of this study was to identify factors associated with herd-level lameness prevalence and associations of lameness and other farm-level factors with milking activity, milk yield, and milk quality in herds with AMS. From April to September 2019, 75 herds with AMS in Ontario, Canada, were visited, and data on barn design and farm management practices were collected. Data from AMS were collected, along with milk recording data, for the 6-mo period before farm visits. Farms averaged 98 ± 71 lactating cows, 2.3 ± 1.5 robot units/farm, 43.6 ± 9.4 cows/robot, 36.4 ± 4.9 kg/d of milk, a milking frequency of 3.01 ± 0.33 milkings/d, and a herd average geometric mean SCC of 179.3 ± 74.6 (× 1,000) cells/mL. Thirty percent of cows/farm (minimum of 30 cows/farm) were scored for body condition (1 = underconditioned to 5 = over conditioned) and locomotion (1 = sound to 5 = lame; clinically lame ≥3 out of 5 = 28.3 ± 11.7%, and severely lame ≥4 out of 5 = 3.0 ± 3.2%). Clinical lameness (locomotion score ≥3) was less prevalent on farms with sand bedding, with increased feed bunk space per cow, and on farms with non-Holstein breeds versus Holsteins, and tended to be less prevalent with lesser proportion of underconditioned cows (with body condition score ≤2.5). Severe lameness occurrence (farms with any cows with locomotion score ≥4) was associated with a greater proportion of underconditioned cows and in farms with stalls with greater curb heights. Herd average milk yield/cow per day increased with lesser prevalence of clinical lameness (each 10-percentage-point decrease in clinical lameness prevalence was associated with 2.0 kg/cow per day greater milk yield) and greater milking visit frequency per day, and tended to be greater with increased feed push-up frequency. Lesser herd average somatic cell count was associated with lesser clinical lameness prevalence, herd average days in milk, and proportion of overconditioned cows, and somatic cell count tended to be lesser for farms with sand bedding versus those with organic bedding substrates. The results highlight the importance of minimizing lameness prevalence, using of sand bedding, ensuring adequate feed access and feed bunk space, and maintaining proper cow body condition to optimize herd-level productivity and milk quality in AMS herds.

Genome-wide association study and functional analyses for clinical and subclinical ketosis in Holstein cattle.

Ketosis is one of the most frequent metabolic diseases in high-yielding dairy cows and is characterized by high concentrations of ketone bodies in blood, urine, and milk, causing high economic losses. The search for polymorphic genes, whose alleles have different effects on resistance to developing the disease, is of extreme importance to help select less susceptible animals. The aims of this study were to identify genomic regions associated with clinical and subclinical ketosis (ß-hydroxybutyrate concentration) in North American Holstein dairy cattle and to investigate these regions to identify candidate genes and metabolic pathways associated with these traits. To achieve this, a GWAS was performed for 4 traits: clinical ketosis lactation 1, clinical ketosis lactation 2 to 5, subclinical ketosis lactation 1, and subclinical ketosis lactation 2 to 5. The estimated breeding values from 77,277 cows and 7,704 bulls were deregressed and used as pseudophenotypes in the GWAS. The top-20 genomic regions explaining the largest proportion of the genetic variance were investigated for putative genes associated with the traits through functional analyses. Regions of interest were identified on chromosomes 2, 5, and 6 for clinical ketosis lactation 1; 3, 6, and 7 for clinical ketosis lactation 2 to 5; 1, 2, and 12 for subclinical ketosis lactation 1; and 20, 11, and 25 for subclinical ketosis lactation 2 to 5. The highlighted genes potentially related to clinical and subclinical ketosis included ACAT2 and IGF1. Enrichment analysis of the list of candidate genes for clinical and subclinical ketosis showed molecular functions and biological processes involved in fatty acid metabolism, lipid metabolism, and inflammatory response in dairy cattle. Several genomic regions and SNPs related to susceptibility to ketosis in dairy cattle that were previously described in other studies were confirmed. The novel genomic regions identified in this study aid to characterize the most important genes and pathways that explain the susceptibility to clinical and subclinical ketosis in dairy cattle.

Benchmarking of farms with automated milking systems in Canada and associations with milk production and quality.

The objective of this study was to benchmark the herd-level housing and management strategies of automated milking system (AMS) farms across Canada and assess the associations of these herd-level housing factors and management practices with milk production and quality. Canadian AMS farms (n = 197; Western Canada: n = 50, Ontario: n = 77, Quebec: n = 59, Atlantic Canada: n = 11) were each visited once from April to September 2019, and details were collected related to barn design and herd management practices. Milk-recording data for the 6 mo before farm visits were collected. Farms averaged (± standard deviation) 110 ± 102 lactating cows, 2.4 ± 1.9 AMS units/farm, 47.5 ± 14.9 cows/AMS, 36.7 ± 5.0 kg/d of milk, 4.13 ± 0.34% fat, 3.40 ± 0.16% protein, and a herd-average somatic cell count of 186,400 ± 80,800 cells/mL. Farms mainly used freestall housing systems (92.5%), organic bedding substrates (73.6%), and free flow cow traffic systems (87.8%); farms predominantly milked Holsteins (90.4%). Multivariable regression models were used to associate herd-level housing factors and management practices with milk production and quality. At the herd level, feed push-up frequency (mean = 12.8 ± 8.3 times per day) and feed bunk space (mean = 64 ± 21.5 cm/cow) were positively associated with milk yield. Greater milk yield was associated with herds using inorganic (sand) versus organic bedding, milking Holsteins versus non-Holsteins, and using a form of mechanical ventilation versus natural ventilation alone. Milk fat and milk protein content were only associated with breed. Herds with lower somatic cell counts had more frequent alley cleaning (mean = 12.1 ± 7.5 times per day), wider lying alleys (mean = 304.5 ± 40.0 cm), and sand bedding. The results highlight the importance of using sand bedding, using mechanical ventilation, keeping feed pushed up, ensuring alleys are clean, and ensuring adequate space at the feed bunk for maintaining herd-level productivity and milk quality in farms with AMS.

Assessing the utility of leukocyte differential cell counts for predicting morbidity, mortality, and growth in a grain-fed veal facility: A prospective single cohort study.

Selective antimicrobial treatment strategies present a means to reduce antimicrobial use at the time of arrival at a veal or dairy beef operation. On-farm machine leukocyte differential cell counts (DCC) that can be acquired quickly may be useful to augment calf risk identification protocols. The objective of this study was to assess the utility of DCC taken at the time of arrival at a grain-fed veal facility and 72 h postarrival for determining morbidity risk, mortality risk, and growth during the production cycle. Data were collected between June and October 2018 from 240 calves upon arrival and from a subset of 160 calves 72 h postarrival at a commercial grain-fed veal facility in Ontario, Canada. Blood samples were evaluated using the QScout BLD test for leukocyte DCC (Advanced Animal Diagnostic, Morrisville, NC). All calves were screened using a standardized health examination, and a blood sample was collected to evaluate serum total protein and DCC. Cox proportional hazards models were constructed for both morbidity and mortality outcomes. Mixed linear regression models were constructed to evaluate average daily gain. Results from data collected at the time of arrival suggest that total protein values ≥5.2 g/dL reduced the hazard of mortality and that a rectal temperature >39.6°C was associated with an increased hazard of morbidity. Calves that were dehydrated gained less, whereas calves with an increased lymphocyte count had a higher rate of growth. Results from DCC collected 72 h postarrival suggest that lymphocyte counts between 4.8 and 5.8 × 109 cells/L decreased the hazard of mortality and counts >7.0 × 109 cells/L decreased the hazard of morbidity, whereas neutrophil counts >6.0 × 109 cells/L increased the hazard of mortality. This study demonstrates that machine DCC at the time of arrival and 72 h after arrival has potential for use in identifying high-risk calves that might require treatment, as part of selective antimicrobial therapy protocols, with the purpose of reducing antimicrobial use without sacrificing animal health in veal facilities.

Effects of molasses-based liquid feed supplementation to a high-straw dry cow diet on feed intake, health, and performance of dairy cows across the transition period.

The objective of this study was to determine the effects of adding molasses-based liquid feed to a high-straw dry cow diet on intake, behavior, health, and performance of dairy cows across the transition period. Holstein cows (n = 40) entering their second lactation or greater were enrolled at dry-off (∼45 d before expected calving) and assigned to 1 of 2 treatments: a high-straw dry cow total mixed ration (TMR) with either (1) no molasses [CON; n = 20; 10.7% crude protein (CP), 1.45 Mcal/kg of net energy for lactation (NEL)] or (2) supplemented with 1 kg/cow daily [dry matter (DM) basis] of molasses-based liquid feed (LF; n = 20; 11.2% CP, 1.49 Mcal/kg of NEL). At calving all cows were fed the same lactating TMR (14.9% CP, 1.68 Mcal/kg of NEL) and followed for 28 d. During the dry period, cows fed the LF diet had greater DM intake (15.3 ± 0.24 vs. 13.4 ± 0.24 kg/d) and tended to have a shorter interval between meals (192.8 ± 8.38 vs. 216.5 ± 7.97 min) and more frequent meals (6.3 ± 0.27 vs. 5.6 ± 0.27 meals/d), while consuming their feed faster (0.09 ± 0.001 vs. 0.08 ± 0.001 kg of DM/min) compared with cows fed the CON diet. Regardless of treatment, cows sorted [100% × (actual intake/predicted intake)] against the longest ration particles (>19 mm), with cows fed the CON diet sorting more against these (81.1 ± 2.6 vs. 93.9 ± 2.6%). Cows fed the CON diet did not sort for or against short particles (<8, >4 mm; 100.2 ± 0.31%), but cows fed the LF diet tended to sort against these (99.2 ± 0.31%). Post-calving, cows fed the LF diet did not sort for long particles (98.5 ± 1.1%), but cows fed the CON diet continued to sort against these (96.3 ± 1.1%). Cows fed the LF diet had higher mean reticulorumen pH in the dry period (6.4 ± 0.05 vs. 6.2 ± 0.06 pH), in the first week after calving (CON = 5.7 ± 0.06 pH, LF = 5.8 ± 0.06 pH), and tended to have higher mean reticulorumen pH in the second week after calving (CON = 5.7 ± 0.06 pH, LF = 5.9 ± 0.06 pH). The results suggest that supplementing a molasses-based liquid feed in high-straw dry cow diets may improve intake and consistency in nutrients consumed during the dry period and in early lactation, as well as possibly promoting better rumen health across the transition period.

Risk factors associated with failed transfer of passive immunity in male and female dairy calves: A 2008 retrospective cross-sectional study.

This retrospective cross-sectional study was designed to identify risk factors associated with failed transfer of passive immunity (FTPI) and to determine differences in colostrum management between male and female dairy calves. Research technicians visited a total of 16 commercial dairy farms weekly. For each calf born on these farms, the farm personnel completed a birth record to document the colostrum management practices provided, level of calving assistance, calf sex, and time of birth. On the weekly visits to the farms, the technicians collected blood from calves that were 1 to 7 d of age. Serum was separated via centrifugation and the concentration of serum total protein (STP) was determined using a digital refractometer. Failed transfer of passive immunity was defined as calves having an STP of <5.2 g/dL. Data were available for 1,778 calves aged 1 to 7 d. Several differences were observed with respect to how male and female calves were managed. Male calves were more likely to receive a lower volume of colostrum, have colostrum delivered using a nipple bottle followed by an esophageal tube feeder, be fed pooled colostrum, and receive fresh colostrum rather than frozen colostrum relative to female calves. Serum total protein (STP) ranged from 3.6 to 9.7 g/dL with a mean of 5.7 g/dL (standard deviation, 0.7 g/dL) and 21.1% of the calves had FTPI. Using a mixed linear regression model, we identified that a calf being male (-0.14 g/dL), being delivered by a hard pull (-0.23 g/dL), and receiving the first feeding colostrum from a combination of a nipple bottle followed by an esophageal tube feeder (-0.12 g/dL) were associated with a lower concentration of STP. Feeding 6 L or more of colostrum in the first 24 h of life was associated with a 0.14 g/dL higher concentration of STP compared with feeding <3.9 L of colostrum. For FTPI, being delivered by a hard pull [odds ratio (OR) 2.21] and receiving the first feeding colostrum from a nipple bottle followed by an esophageal tube feeder (OR 1.83) were associated with higher odds of FTPI. Feeding >6 L of colostrum in the first 24 h of life was associated with a reduced odds (OR 0.65) of FTPI compared with feeding <3.9 L of colostrum. This study highlights the importance of certain management practices in reducing FTPI incidence and identifies discrepancies in colostrum management between male and female dairy calves.

Management of cull dairy cows: Culling decisions, duration of transport, and effect on cow condition.

Many cows culled from dairy farms arrive at livestock markets or abattoirs in compromised condition, but it is unknown whether cows are compromised at the time of culling or deteriorate during the marketing process. This study followed cull cows from farm to abattoir, monitored any deterioration, and tested the effect of providing such information on subsequent culling. For 11 mo, data were collected from 20 dairy farms, livestock markets, and abattoirs. Cows' body condition, lameness, and udder condition (as binary outcomes) were assessed at 4 points: when placed on the culling list, before leaving the farm, at auction, and at the abattoir. Based on the first 5 mo of data (baseline period), information materials were provided to 10 randomly selected farms (Informed treatment), and the other 10 served as a Control. Logistic mixed models were used to test differences in cows' condition at the 4 points of assessment, using the assessment before leaving the farm as a reference value and cow-within-farm as a random effect. The effects of providing information on outcome measures (proportion thin, severely lame, with udder edema, poor fitness for transport, euthanized, and died) were tested with a general linear model. As demand for milk increased during the baseline period, additional linear mixed models were fitted to test whether the same outcome measures were affected by time (baseline or treatment period) and treatment (Informed or Control) using farm as a random effect. While cows were on the culling list (before shipping) the odds of being thin or having poor fitness for transport increased. After leaving the farms, cows spent (mean ± standard deviation) 82 ± 46 h in the marketing system before being slaughtered. Shipping from farm to abattoir increased the odds of being thin, having udder edema, or showing poor fitness for transport [odds ratio (OR) 5.8, 95% confidence interval 4.2 to 8.1; OR 14.7, 10.7 to 20.2; and OR 7.3, 5.7 to 9.5, respectively]. Providing this information to farmers (Informed treatment) did not affect the outcome measures. Compared with the baseline, during the treatment period fewer cows were shipped when thin (4.9 versus 9.0%) and with poor fitness for transport (15.7 versus 25.8%), and fewer cows died (5.4 versus 11.9%) or were euthanized (13.3 versus 20.5%). Increased demand for milk appeared to lead to delayed culling, such that more compromised cows were sent to slaughter. The results of this study show a need for clear and specific guidelines to assess fitness for transport of cull dairy cows.