Lactating Dairy Cattle Research Articles

Effects of postpartum acetylsalicylic acid on metabolic status, health, and production in lactating dairy cattle

The transition period is one of the most challenging times for dairy cattle. Previous research suggests that treatment of postpartum cows with anti-inflammatory drugs may decrease pain and inflammation, enhancing cow welfare and performance during this challenging period. However, these strategies involve numerous time-consuming interventions, which require extra labor and do not fit modern farm logistics. The objective of this experiment was to assess the effects of acetylsalicylic acid (ASA) every 24 h for 2 d after calving on (1) daily milk yield, daily milk conductivity, and daily rumination during the first 60 days in milk (DIM), and 305-d mature-equivalent milk, milk fat, and milk protein yields, (2) body condition score, β-hydroxybutyrate (BHB), and haptoglobin, and (3) incidence of clinical diseases during the first 60 DIM. Dairy cows (n = 246) from a dairy farm located in Pennsylvania were enrolled in this experiment. Cows were blocked by parity and assigned randomly to 1 of 2 treatments: (1) ASA (n = 121), in which cows received 2 treatments with ASA (200 mg/kg; 4 boluses), the first within 12 h after parturition and the second 24 h later; or (2) untreated (UNT; n = 125), in which cows remained untreated. Blood samples were collected at 30 ± 6 h, 7 ± 3 d, and 14 ± 3 d after calving to measure BHB and haptoglobin concentrations. Body condition score was assessed at enrollment, 7 ± 3 DIM, 14 ± 3 DIM, and 50 ± 10 DIM. Furthermore, incidences of diseases, daily rumination, daily milk yield, and daily milk conductivity during the first 60 DIM and 305-d mature-equivalent milk, milk fat, and milk protein yields were collected from on-farm computer records. The data were analyzed using mixed multiple linear and logistic regression models as a randomized complete block design. Multiparous cows treated with ASA produced 1.64 kg/d more milk compared with multiparous cows that remained untreated (ASA = 41.66 ± 0.88 kg/d; UNT = 40.02 ± 0.81 kg/d) during the first 60 DIM. There was no difference in daily milk conductivity and rumination between treatments. Cows treated with ASA had lower concentration of BHB (ASA = 1.16 ± 0.64 mmol/L; UNT = 1.23 ± 0.80 mmol/L) during the first 14 ± 3 DIM and had higher body condition score within the first 50 ± 10 DIM compared with cows that remained UNT. There were no differences in circulating concentrations of haptoglobin between treatments. These results support previous findings showing that the use of anti-inflammatory drugs after calving may increase milk production and affect the metabolic status of dairy cows.

Short communication: Effect of glucose infusion dose and stage of lactation on glucose tolerance test kinetics in lactating dairy cows

The objective for this study was to determine the effect of glucose dose and days following peak milk yield on plasma glucose, serum insulin, and plasma nonesterified fatty acids (NEFA) kinetics during an intravenous glucose tolerance test (IVGTT) in lactating dairy cattle. Six lactating Holstein dairy cows (3 primiparous and 3 multiparous) were assigned to 2 squares and received 0.092, 0.15, or 0.3 g of glucose/kg of body weight (BW) during an IVGTT at 74 and 221 d in milk (DIM), representing early (post-peak) lactation and mid lactation, respectively. Treatments were applied in a replicated Latin square design using contiguous 7-d periods within each stage of lactation. Milk production and dry matter intake were determined daily during the first 6 d of each period. The IVGTT was performed on d 7. For the IVGTT, cows were prepared with indwelling catheters in each jugular vein, and blood samples were collected at -15, -10, 5, 10, 15, 20, 30, 45, 60, 90, and 120 min relative to the glucose infusion. Samples were analyzed for plasma glucose, serum insulin, and plasma NEFA concentrations. Increasing the glucose dose during the IVGTT increased plasma glucose area under the curve (AUC), decreased glucose half-life, and increased maximal plasma glucose concentrations in plasma during the IVGTT. Greater glucose dose during the IVGTT elevated serum insulin AUC and increased nadir NEFA concentrations. Maximal plasma glucose concentration during the IVGTT was lower, whereas maximum NEFA concentration, NEFA AUC, and NEFA clearance rate were greater at 74 than at 221 DIM. Only glucose half-life was responsive to stage of lactation × glucose dose effects during the IVGTT, and the decrease in glucose half-life with increasing glucose dose was greater at 74 than at 221 DIM. Glucose AUC was greater and NEFA AUC lower for cows at 74 than at 221 DIM. For the doses tested, a glucose dose greater than 0.092 g/kg of BW resulted in peak blood glucose concentration that exceeded the previously reported renal glucose excretion threshold of 8.3 mM. There is a need for accompanying data to determine if this is the case for the glucose doses evaluated in this experiment. Based on maximal peak glucose concentrations and effects on glucose half-life, we identify 0.092 g of glucose/kg of BW (0.46 g/kg of metabolic body weight) as the preferred dose for the IVGTT for cows at 74 and 221 DIM in this study.

Effects of Capsicum and Propyl-Propane Thiosulfonate on Rumen Fermentation, Digestion, and Milk Production and Composition in Dairy Cows.

Simple SummaryEssential oils and their active compounds have been investigated as feed additives to improve performance in a wide range of farm animals. Most studies related to ruminants have been conducted in vitro and suggest that their effects may be beneficial for ruminant health and production performance. However, in vivo studies are limited. We investigated the effects of capsicum oleoresin (CAP) and propyl-propane thiosulfonate (PTSO) on rumen fermentation, total tract digestibility, and milk yield and composition in lactating dairy cattle. At the doses used, CAP and PTSO failed to demonstrate any effects on rumen fermentation or milk yield, but dry matter intake tended to increase in cows fed with CAP. Feeding PTSO increased milk efficiency compared with the control diet.Essential oils may affect rumen fermentation, nutrient digestion, and milk production and composition. The objective of this study was to test the effects of capsicum oleoresin (CAP) and propyl-propane thiosulfonate (PTSO) on rumen fermentation, total tract digestibility, and milk yield and composition in lactating dairy cattle. Six lactating Holstein cows (averaging (mean ± SD) 130 ± 40 days in milk and 723 ± 55 kg of body weight) fitted with rumen cannulae were used in a duplicated 3 × 3 Latin square design. Treatments were: a control diet (CTR), the CTR diet with the addition of 500 mg/d/cow of CAP, and the CTR diet with the addition of 250 mg/d/cow of PTSO. Dry matter intake (DMI) averaged 20.7 kg/d with a tendency towards higher intake in cows fed CAP and lower in those fed PTSO (p = 0.08). Milk yield averaged 31.8 kg/d with no difference among treatments. However, feed efficiency was higher in PTSO supplemented cows compared with CTR (1.65 and 1.41 kg of milk yield/kg of DMI, respectively; p < 0.01). At the doses used in this experiment, CAP and PTSO failed to demonstrate any effects on rumen fermentation, but PTSO increased the efficiency of feed utilization to produce milk.

Sampling strategy and measurement device affect vaginal temperature outcomes in lactating dairy cattle

Body temperature (BT) is widely used to evaluate health and heat load status in cattle. Despite its importance, studies vary in how BT is measured and in the biological interpretation of the results. Costs, practicality, labor, and welfare concerns can affect how BT is measured, including frequency of measurement and the type of device used. Inaccurate BT outcomes may have implications for cattle welfare; for example, animals may only receive treatment when fever is identified. Our objectives were (1) to compare measurement of vaginal temperature (VT) using relatively small, inexpensive, and low-accuracy loggers (±0.5 to ±1°C, iButton range; Embedded Data Systems, Lawrenceburg, KY) to a high-accuracy logger (±0.1°C; StarOddi, Gardabaer, Iceland), and (2) to evaluate how different BT sampling strategies correspond to 24-h VT in lactating dairy cows. To address the first objective, VT data from 54 cows were recorded every 45 min for 12 d/cow, on average, using 2 different types of temperature loggers (StarOddi DST centi-T and iButton DS1921H or DS1922L) attached to a shortened, hormone-free controlled internal drug release insert. Average VT obtained from both loggers were compared using mixed models and regression analyses. In addition, we tested the consistency of the low-accuracy loggers in detecting cows with elevated BT using the kappa coefficient of concordance. To address the second objective, VT data from 20 cows were recorded every min for 9 to 11 d/cow using StarOddi loggers. Using these data, we estimated average VT using 11 sampling strategies (every 5, 10, 15, 30, 45, 60, and 120 min, 1×/d recorded in the morning or afternoon, 2×/d, or 3×/d). Estimates and observed means were compared using linear regression. Compared with StarOddi loggers, the iButtons either underestimated (H model: 38.7 vs. 38.0 ± 0.06°C) or overestimated VT (L model: 38.7 vs. 39.2 ± 0.04°C). When considering elevated or fever VT thresholds, iButtons did not correctly classify animals; kappa coefficients of concordance were ≤0.35. Measuring VT as often as every 120 min resulted in more accurate estimates compared with strategies that recorded it once to thrice per day. These results indicate that the type of device (i.e., data logger) and sampling strategies affect BT outcomes and that these decisions affect the interpretation of BT data.

Economic Value of Dwarf Elephant Grass and Dried Distiller Grain with Soluble as Feed of Smallholder Dairy Farm in Tulungrejo Village, Ngantang District, Malang Regency

The average number of lactation dairy cattle ownership in community farms in Tulungrejo Village, Ngantang District, Malang Regency ranges from 5-6 cows per household. Farmers rely on grass as the main feed for dairy cows and concentrate from local Dairy Cooperative as additional feed. Average milk production was 10-11 liters/cow/day. Changes in the use of feed types have occurred in the last two years. The use of elephant grass (Pennisetum purpureum) by farmers has slowly changed to dwarf elephant grass (Pennisetum purpureum cv Mott) until now. The amount of concentrate given was reduced and replaced by DDGS by ratio (concentrate: DDGS) 1: 4. This study analyzed the economic value of the use of dwarf elephant grass and DDGS as feed especially its impact on farmers’ income. Data obtained through interview methods from 37 respondents of dairy farmers in Tulungrejo Village, Ngantang District, Malang Regency in July - September 2019. Data analysis was carried out in a descriptive quantitative manner. The results showed the average daily milk production increased by 18% or equivalent to 1.77 liters/cow/day and there was a 18.68% increase in farmer income or equivalent to IDR 7,397,160 within 2 years.

Comparison of milk production, intake, and total-tract nutrient digestion in lactating dairy cattle fed diets containing either wheat middlings and urea, commercial fermentation by-product, or rumen-protected soybean meal

The objective of this study was to evaluate the effects of a commercially available fermentation by-product in a diet containing adequate rumen-degradable protein (RDP) on milk performance, intake, and total-tract nutrient digestion in lactating dairy cattle. Primiparous (n = 48) and multiparous (n = 144) lactating dairy cattle were stratified by milk production and randomly allocated into 12 pens containing 4 primiparous and 12 multiparous animals each. Cattle averaged 118 d in milk and 712 kg of body weight at trial start. Treatment diets, on a dry matter (DM) basis, consisted of 42% corn silage, 13% alfalfa hay and silage, 20% grain corn, and 25% protein premix containing either soybean meal, wheat middlings, and urea (SBM+U), soybean meal and fermentation by-product (SBM+F), or soybean meal and rumen-protected soybean meal (RP-SBM). All 3 diets provided a similar level (DM basis) of neutral detergent fiber analyzed using α-amylase and sodium sulfite and corrected for ash content (31%), crude protein (CP, 14.9%), starch (26%), and metabolizable energy (2.7 Mcal/kg), and differed in sources of RDP. The trial consisted of a 2-wk adaptation and covariate period during which all cows were fed the RP-SBM diet and covariate measurements were taken. Pens were then randomly allocated to treatments, and weekly measurements of milk production, intake, body weight, and condition score were taken for 10 wk. All data were analyzed using the Proc Mixed procedure in SAS (SAS Institute Inc., Cary, NC). Increased DM intake was observed for cows fed SBM+F compared with cows fed SBM+U and RP-SBM (28.3 vs. 26.9 and 26.7 kg/d, respectively). Cows fed SBM+F produced more energy-corrected milk (45.3 kg/d) compared with cows fed SBM+U and RP-SBM (43.6 and 43.7 kg/d, respectively). Milk protein yield was also increased in cows fed SBM+F. No differences were observed with body weight or condition score gain throughout the trial. Apparent total-tract digestibility of fiber was decreased in cows fed SBM+F, likely as a result of increased intake. Responses are consistent with previous research in our laboratory that demonstrated a decrease in ruminal CP degradation, leading to an increase in metabolizable protein supply in the small intestine. The fermentation by-product might be useful in diets containing adequate amounts of RDP from soybean meal or alfalfa. The results from this experiment demonstrate beneficial milk performance responses to fermentation by-product when fed with a source of RDP.

Identification of stable genes in the corpus luteum of lactating Holstein cows in pregnancy and luteolysis: Implications for selection of reverse-transcription quantitative PCR reference genes

In lactating dairy cattle, the corpus luteum (CL) is a dynamic endocrine tissue vital for pregnancy maintenance, fertility, and cyclicity. Understanding processes underlying luteal physiology is therefore necessary to increase reproductive efficiency in cattle. A common technique for investigating luteal physiology is reverse-transcription quantitative PCR (RT-qPCR), a valuable tool for quantifying gene expression. However, reference-gene-based RT-qPCR quantification methods require utilization of stably expressed genes to accurately assess mRNA expression. Historically, selection of reference genes in cattle has relied on subjective selection of a small pool of reference genes, many of which may have significant expression variation among different tissues or physiologic states. This is particularly concerning in dynamic tissues such as the CL, with its capacity for rapid physiologic changes during luteolysis, and likely in the less characterized period of CL maintenance during pregnancy. Thus, there is a clear need to identify reference genes well suited for the bovine CL over a wide range of physiological states. Whole-transcriptome RNA sequencing stands as an effective method to identify new reference genes by enabling the assessment of the expression profile of the entire pool of mRNA transcripts. We report the identification of 13 novel putative reference genes using RNA sequencing in the bovine CL throughout early pregnancy and luteolysis: RPL4, UQCRFS1, COX4I1, RPS4X, SSR3, CST3, ZNF266, CDC42, CD63, HIF1A, YWHAE, EIF3E, and PPIB. Independent RT-qPCR analyses were conducted confirming expression stability in another set of CL tissues from pregnancy and regression, with analyses performed for 3 groups of samples: (1) all samples, (2) samples from pregnancy alone, and (3) samples throughout the process of CL regression. Seven genes were found to be more stable in all states than 2 traditional reference genes (ACTB and GAPDH): RPS4X, COX4I1, PPIB, SSR3, RPL4, YWHAE, and CDC42. When CL tissues from pregnant animals alone were analyzed, CST3, HIF1A, and CD63 were also identified as more stable than ACTB and GAPDH. Identification of these new reference genes will aid in accurate normalization of RT-qPCR results, contributing to proper interpretation of gene expression relevant to luteal physiology. Furthermore, our analysis sheds light on the effects of luteolysis and pregnancy on the stability of gene expression in the bovine CL.

Evaluation of 4 different teat disinfection methods prior to collection of milk samples for bacterial culture in dairy cattle

The first objective of this study was to determine whether differences would occur among teat end preparation techniques with regard to potential contamination of milk samples collected for bacterial culture. The second objective was to determine whether differences would be detected in genus or species of bacteria isolated from samples collected using the various methods as well as from contaminated or uncontaminated samples. Mammary quarter foremilk samples were collected from lactating dairy cattle at the University of Missouri Foremost Research Dairy Farm (Columbia). Four different teat end preparation methods were used to compare contamination rates in milk samples. Sampling techniques used before milk collection included (1) no preparation, (2) pre-milking disinfection and single-use towel drying of teats only, (3) scrubbing of the teat end with alcohol only, and (4) pre-milking disinfection, single-use towel drying, and scrubbing of the teat end with alcohol. Milk was plated on Columbia blood agar. Cultures were read at 48 h, with the number of morphologically different bacterial colony types quantified and isolated. Isolates were identified using MALDI-TOF mass spectrometry. Median numbers of colony types were compared among groups using Kruskal-Wallis ANOVA with post-hoc pairwise comparisons, and proportional data were compared using the chi-squared test. A total of 168 cows, including 665 quarters, were sampled, and 1,614 isolates resulted. Analysis with MALDI-TOF identified 29 unique genera and 81 unique species among the samples. More contaminated samples occurred in groups 1 and 2 compared with groups 3 and 4. Group 3 had more contaminated samples than group 4. The majority of Pseudomonas spp. isolates were identified within group 2. When applying previously described niches to Staphylococcus spp., environmental species were more likely to be identified among contaminated samples, whereas host-adapted species were more likely to be identified among uncontaminated samples. These data confirm that scrubbing the teat end with alcohol after pre-milking disinfection with an iodine-based teat disinfectant and drying of the teat minimizes contamination of the milk sample.

Effect of vaccination with a Mannheimia haemolyticasubunit vaccine on milk yield in lactating dairy cows

Vaccination of adult lactating dairy cattle can have a negative impact on milk production. Decreased milk production may occur from a combination of the cow’s immune response, endotoxin level in the vaccine, and the impact of cattle handling. A randomized clinical trial utilized 3 treatment groups to examine changes in milk production following vaccination with a Mannheimia haemolytica subunit vaccine (MHSV; Nuplura PH, Elanco Animal Health) using 972 lactating dairy cows on a single Midwestern dairy: a vaccinated group (MHSV, n=315); a placebo-treated control (saline, n=342); and a negative control group (no injections, n=315). The decline in milk across a 3 d post-treatment period for the saline group was 0.5 lb (0.2 kg) greater than the negative control cows, but the difference was not significant (P=0.57). The decline in milk during the same time period for cows in the MHSV group was 1.5 lb (0.7 kg) more than the negative control, (P=0.02). The declines between the saline group (0.5 lb; 0.2 kg) and the MHSV group (1.5 lb; 0.7 kg) were not significantly different (P=0.17).

Studies on early detection of sub clinical mastitis and its antibiogram in lactating dairy cattle

Studies on early detection of sub clinical mastitis and its antibiogram in lactating dairy cattle

Nutrient digestibility, nitrogen excretion, and milk production of mid-lactation Jersey × Friesian cows fed diets containing different proportions of rumen-undegradable protein.

The present study was planned to test the hypothesis that feeding lactating dairy cattle with varying levels of rumen-undegradable protein (RUP) can enhance protein utilization, milk production, milk protein, and nitrogen (N) excretion. Forty mid-lactating crossbred (Jersey × Friesian) cattle were randomly divided into four groups. Four treatment diets were formulated to contain 30%, 40%, 50%, and 60% RUP of crude protein. Dry matter (DM) and crude protein intakes were significantly reduced with increasing dietary RUP levels. Crude protein digestibility increased linearly with incremental increases in dietary RUP levels. Cattle fed 60% RUP showed a linear decrease in N intake compared to that in the other groups. A linear decrease in urinary N and linear increases in net N, milk N, and N-use efficiency were observed with increasing dietary RUP levels. Actual milk, energy-corrected milk, and 4% fat-corrected milk yields (kg/day) increased linearly with an increasing degradability of protein. However, milk protein, solids not fat and total solids, as well as the yields of protein, fat, and lactose, showed significant increases with increased RUP supplementation. Collectively, the results indicate that formulating dairy cow diets to contain 60% RUP results in better lactating performance and N-use efficiency and lower N excretion.

Intravaginal instillation of prostaglandin F2α was as effective as intramuscular injection for induction of luteal regression in lactating dairy cows

Our objectives were to test the efficacy of intravaginal (IVG) administration of PGF2α to induce corpus luteum (CL) regression, compare circulating progesterone (P4) profiles in cows receiving IVG versus intramuscular (IM) treatment with PGF2α, and evaluate reproductive outcomes. Lactating Holstein cows were synchronized using a Double-Ovsynch protocol [GnRH, 7 d later PGF2α, 3 d later GnRH, 7 d later GnRH, 7 d later PGF2α, 1 d later PGF2α, 32 h later GnRH, 16 to 20 h timed artificial insemination (TAI)] to receive TAI at 67 ± 3 d in milk. Seven days after the first GnRH treatment (time 0), cows with at least 1 visible CL ≥15 mm were blocked by parity and randomly assigned to a treatment that consisted of IM injection (IM-PGF; n = 201) or IVG instillation (IVG-PGF; n = 201) of PGF2α. Cows in IM-PGF received a single 25-mg dose of PGF2α (dinoprost tromethamine) intramuscularly. Cows in IVG-PGF received two 25-mg doses of PGF2α 12 h apart delivered through a catheter in the cranial portion of the vagina. Blood samples were collected at 0, 12, 48, and 72 h after treatment. Ovulation to the first GnRH of Double-Ovsynch was determined through transrectal ultrasonography. Only cows with P4 ≥1 ng/mL (functional CL) at time 0 (IM-PGF = 169; IVG-PGF = 179) were included in the analyses. Binary and quantitative data were analyzed by logistic regression and ANOVA with repeated measures, respectively. Results are presented as least squares means. Concentrations of P4 and the proportion of cows with a new CL at time 0 did not differ. Overall, the proportion of cows with CL regression using 1 ng of P4/mL (IM-PGF = 89.0%; IVG-PGF = 86.7%) or 0.5 ng of P4/mL (IM-PGF = 82.2%; IVG-PGF = 82.1%) as the cutoff did not differ. Concentrations of P4 were affected by treatment, time, and treatment × time interaction. Cows in IVG-PGF had greater mean P4 at 12 h than cows in IM-PGF. Mean P4 did not differ at 48 or 72 h after treatment. The proportion of cows with estrus recorded within 3 d of treatment (IM-PGF = 45.4%; IVG-PGF = 48.9%), ovulation risk after treatment (IM-PGF = 88.5%; IVG-PGF = 85.1%), and pregnancies per artificial insemination after TAI (IM-PGF = 51.5%; IVG-PGF = 57.8%) did not differ. We concluded that 2 IVG doses of 25 mg of PGF2α 12 h apart were as effective as a single 25-mg IM dose of PGF2α for inducing luteal regression in lactating dairy cattle.

300 Efficacy of the measurements of the vaginal electrical resistance to determine the phase of the estrous cycle in lactating dairy cattle

Abstract Estrus detection in dairy cattle is an important factor that contributes to the reproductive efficiency. Lack and inaccuracy of heat detection are associated with increased days open, calving interval, economic loss and culling due to infertility. Efforts have been made to identify methods to assist in estrus detection. The objective of this study was to examine if vaginal electrical resistance (VER) measured by a commercial probe throughout the estrous cycle in lactating dairy cows aids to determine the onset of estrus. A total of 9 lactating Holstein cows were monitored for 2 – 3 estrous cycles, ultrasonography of the ovary, blood sample for progesterone and VER was assessed every other day during the luteal phase (LUT) and every day during the follicular phase (FOL). A total of 339 VER measurements were collected, 66 during the FOL phase and 273 corresponded to the LUT phase. Mean VER differed (P &amp;lt; 0.001) between FOL (294.5 ± 51.3) and LUT (316.4 ± 46.2), similarly the progesterone concentration was different between the LUT and FOL phases (0.38 ± 0.24 ng/mL vs. 3.41 ± 2.08 ng/mL, respectively) (P &amp;lt; 0.001). No differences were observed between the vaginal temperature of cows in LUT (38.2 ± 0.4 C°) or FOL phase (38.3 ± 0.3 C°). Cervix diameter differed (P &amp;lt; 0.01) between FOL (35.9 ± 3.8 mm) and LUT (34.5 ± 3.4mm), VER has a significant relation (P &amp;lt; 0.001) with the diameter of the Corpus luteum (279.8 + 1.54 x Cervix diameter). Similarly, VER had a significant relationship (P = 0.03) with diameter of the dominant follicle at estrus (355.2 + -3.9 x follicle diameter). These findings suggest that VER changes according to the phase of the estrous cycle, VER decreased during sexual receptivity and increased during the luteal phase. VER may improve the accuracy to diagnose heat in dairy cows.

Automated detection of health disorders in lactating dairy cattle on pasture: a preliminary study.

Since previous health monitoring systems have shown themselves to be unsuccessful in predicting health disorders in dairy cows managed on pasture, the aim of this study was to evaluate the performance of automated health monitoring integrated in an accelerometer-based oestrus detection system (ODS) for dairy cows on pasture. Mixed-breed lactating dairy cows (n=109) in a seasonal-calving herd managed at pasture were fitted with an ODS that provided automated health monitoring. The ODS performed multimetric analysis of behavioural patterns to generate health alerts. Data were collected during the artificial insemination period of 66 days. Clinical examinations and farmer's observations were used to evaluate the performance of automated health monitoring. During the insemination period, the farmer generated two health alerts, which were classified false positives (2/2; 100%). The ODS generated 31 automated health alerts. Of all automated health alerts, 3/31 (9.7%) were confirmed as true health disorders and 28/31 (90.3%) alerts were classified as false positives. The positive predictive value (PPV) of automated health monitoring was 9.7 (95% CI=2-25.8) %. The ODS was able to alert lactating dairy cows on pasture suffering from health disorders. True health disorders were alerted by the ODS before the farmer noticed them, which could provide early and successful treatment when using the system on-farm for automated health monitoring. The evaluated accuracy of automated health monitoring is opposed to a targeted use of the system for on-farm health monitoring. For further validation, testing on other farms and during the transition period would be of interest.

Comparative efficacy of antimicrobials for treatment of clinical mastitis in lactating dairy cattle: a systematic review and network meta-analysis.

A systematic review and network meta-analysis were conducted to assess the relative efficacy of antimicrobial therapy for clinical mastitis in lactating dairy cattle. Controlled trials in lactating dairy cattle with natural disease exposure were eligible if they compared an antimicrobial treatment to a non-treated control, placebo, or a different antimicrobial, for the treatment of clinical mastitis, and assessed clinical or bacteriologic cure. Potential for bias was assessed using a modified Cochrane Risk of Bias 2.0 tool. From 14775 initially identified records, 54 trials were assessed as eligible. Networks were established for bacteriologic cure by bacterial species group, and clinical cure. Disparate networks among bacteriologic cures precluded meta-analysis. Network meta-analysis was conducted for trials assessing clinical cure, but lack of precision of point estimates resulted in wide credibility intervals for all treatments, with no definitive conclusions regarding relative efficacy. Consideration of network geometry can inform future research to increase the utility of current and previous work. Replication of intervention arms and consideration of connection to existing networks would improve the future ability to determine relative efficacy. Challenges in the evaluation of bias in primary research stemmed from a lack of reporting. Consideration of reporting guidelines would also improve the utility of future research.

Do dairy cattle use a woodchip bedded area to rest on when managed on pasture in summer?

Previous studies have demonstrated that dairy cattle prefer pasture over indoor conditions especially at nighttime, which suggests they perceive pasture as an attractive place to rest. Indeed, cows avoid and spend less time lying on hard surfaces, such as concrete or mattresses, compared to softer surfaces. This study aimed to investigate how much time cows spend lying on pasture at the end of summer when the ground can be hard, compared to a softer surface. Four groups of lactating dairy cattle (5 cows/group) had access to either pasture alone or a pasture containing two deep bedded woodchip areas for 9 consecutive days in a cross-over design. Woodchip usage and posture (upright or lying) were recorded using data loggers and video cameras. We also recorded weather conditions, surface characteristics (hardness, dry matter content, temperature) and milk production. There were no consistent significant differences in lying times of cows with or without woodchip bedded areas. Average lying times for groups with access to pasture only and the woodchip were 8.9 h/24 h (range: 7.8–10.1 h) and 8.5 h/24 h (range: 7.6–9.7 h), respectively, excluding milking times. Average number of hours per day on the woodchip was 2.1 h (range: 0–5.9 h), however, there was considerable animal variation in the use of the woodchip bedded areas. When cows were on the woodchip, they spent on average 51 % of their time lying (SEM: 7 %) and when they were on pasture they spent 36 % of the time lying (SEM: 1 %). Most of the lying, however, was on the grass. Both surfaces likely provided cows with a comfortable lying surface despite pasture being harder than the woodchip. Rainfall prior to data collection may have contributed to pasture being unusually soft for the time of year. Overall, lying times decreased with increasing heat load (air temperature, temperature-humidity index, heat load index, P < 0.001) and rainfall (P = 0.002). Cows spent less time on the grass and more time on the woodchip as the daily average air temperature increased; for each 1 °C increase in air temperature, the time spent on grass decreased by 1.0 ± 0.46 (SE) percentage points per day (P = 0.047). We speculate that this was due to woodchip being a cooler surface or attracting fewer flies than the grass. In conclusion, cows varied in their use of deep bedded woodchip areas when provided in the pasture, however, most of the time spent lying was on the grass.

Exploring seasonal variations in the mineral profile of rotationally grazed tropical pastures on commercial beef and dairy farms in Jamaica

This study explored seasonal variation in the mineral profile of rotationally grazed pastures supporting beef and dairy cattle on commercial farms in Jamaica. While beef and dairy cattle are primarily reared on pasture in Jamaica with minimal supplementary feeding, the mineral profile of Jamaican pastures is largely unknown. Grass samples were collected by hand plucking from three (3) dairy and two (2) beef representative farms during the dry (January - March), intermediate (May - July) and wet seasons (September - November) following a stratified random sampling scheme. Laboratory analyses were conducted to determine concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), Zinc (Zn), iron (Fe) and manganese (Mn). Nitrogen concentration was significantly impacted by season (p < 0.05) and was highest in the wet season (18.4 – 27.6 g/kg DM) and lowest in the dry season (10 - 25.2 g/kg DM), as expected, since soil moisture directly influences the availability and uptake of N by grasses. Generally, P concentration ranged from 2.63 - 4.26 g/kg DM and was significantly affected by season on all farms, with the exception of one dairy farm (P=0.034). The high level of P found in the present study could be as a result of P accumulation in the soil because of the immobile nature of P making it resistant to leaching. The range obtained indicated that P levels were adequate to satisfy the nutritional requirements of both beef and dairy cattle. The potassium concentration ranged from 4.16 - 12.3 g/kg DM and was influenced by season only in areas when the dry season was severe combined with locations where soil water retention capacity was low. Calcium ranged from 2.05 - 4.19 g/kg DM and was generally highest in the dry season and lowest in the wet season, suggesting the accumulation of Ca under drier conditions in response to drought and heat tolerance mechanisms in grasses. Only on the dairy farms did season significantly affect Mg concentration. Season had no influence on the concentrations of Na, Zn, Fe and Mn. Calcium/phosphorus ratio was significantly affected by season on all farms (p < 0.05) and was higher in the dry season. It was concluded that the macro-mineral profile of Jamaican pastures supporting beef and dairy cattle is generally superior in the wet season while micro-minerals seem to be less sensitive to seasonal variations. The concentrations of Ca, Na and Cu in these pastures were below the dietary requirement for lactating dairy cattle and would therefore require supplementation.

Effect of Heat Stress on Bacterial Composition and Metabolism in the Rumen of Lactating Dairy Cows.

Heat stress negatively impacts the health and milk production of dairy cows, and ruminal microbial populations play an important role in dairy cattle's milk production. Currently there are no available studies that investigate heat stress-associated changes in the rumen microbiome of lactating dairy cattle. Improved understanding of the link between heat stress and the ruminal microbiome may be beneficial in developing strategies for relieving the influence of heat stress on ruminants by manipulating ruminal microbial composition. In this study, we investigated the ruminal bacterial composition and metabolites in heat stressed and non-heat stressed dairy cows. Eighteen lactating dairy cows were divided into two treatment groups, one with heat stress and one without heat stress. Dry matter intake was measured and rumen fluid from all cows in both groups was collected. The bacterial 16S rRNA genes in the ruminal fluid were sequenced, and the rumen pH and the lactate and acetate of the bacterial metabolites were quantified. Heat stress was associated with significantly decreased dry matter intake and milk production. Rumen pH and rumen acetate concentrations were significantly decreased in the heat stressed group, while ruminal lactate concentration increased. The influence of heat stress on the microbial bacterial community structure was minor. However, heat stress was associated with an increase in lactate producing bacteria (e.g., Streptococcus and unclassified Enterobacteriaceae), and with an increase in Ruminobacter, Treponema, and unclassified Bacteroidaceae, all of which utilize soluble carbohydrates as an energy source. The relative abundance of acetate-producing bacterium Acetobacter decreased during heat stress. We concluded that heat stress is associated with changes in ruminal bacterial composition and metabolites, with more lactate and less acetate-producing species in the population, which potentially negatively affects milk production.

Short communication: Determination of the milk pharmacokinetics and depletion of milk residues of flunixin following transdermal administration to lactating Holstein cows

Flunixin is a nonsteroidal anti-inflammatory drug and the most commonly prescribed analgesic in cattle in the United States. Recently, the US Food and Drug Administration (FDA) approved a transdermal formulation of flunixin for control of pyrexia associated with bovine respiratory disease and the control of pain associated with foot rot. The transdermal formulation is not currently approved for use in lactating dairy cattle in the United States, but extra-label use in dairy cattle is permissible under US regulations. The objectives of this study were to determine the pharmacokinetics in milk of dairy cows treated with transdermal flunixin and determine an appropriate withdrawal time for milk. Ten lactating Holstein cows were enrolled into the study in mid lactation. Following treatment, cows were milked 3 times per day through 144 h. Milk samples were collected for drug analysis using ultra-high-pressure liquid chromatography coupled with a triple quadrupole mass spectrometer. The geometric mean maximum concentration for flunixin in milk was 0.010 μg/mL and was 0.061 μg/mL for the active metabolite, 5-hydroxyflunixin. The geometric mean terminal half-life was 20.71 h for flunixin and 22.62 h for 5-hydroxyflunixin. Calculations to approximate a withdrawal time in milk following transdermal flunixin administration were accomplished using a statistical tolerance limit procedure. This analysis indicated that it would be prudent to observe a withdrawal period of 96 h following the last treatment. This is more than twice as long as the labeled withdrawal period of 36 h following use of the injectable formulation. The withdrawal period suggested by this work should be applied carefully, as this study was not conducted under the full quality control practices required by the US FDA for a full drug approval study. Caution should be taken when applying this withdrawal time to diseased animals, animals that are milked with different milking frequencies, and those in different stages of production as these have all been shown to affect drug depletion from milk.

Data-driven approach to using individual cattle weights to estimate mean adult dairy cattle weight

BackgroundKnowledge of accurate weights of cattle is crucial for effective dosing of individual animals and for reporting antimicrobial usage. For the first time, we provide an evidence-based estimate of the...