Non-Invasive Indicators Associated with Subacute Ruminal Acidosis in Dairy Cows

Influences of fat-protein-ratio and udder health parameters on the milk urea content of dairy cows

The milk urea content is influenced by a large variety of factors, including the quantity and quality of protein fed, its balance with energy, diurnal fluctuations, management, season, analysis method, and also individual cow factors which include the health status of the cow. Aim of this study was to investigate the effects of metabolic disorders (ketosis, ruminal acidosis; indicated by the fat-protein-content of the milk) as well as high somatic cell counts and udder diseases on the milk urea content of dairy cows from different regions and farms across Germany. For this purpose, 5 independent data sets which contain information derived from monthly milk recordings (data sets A (6,140,342 test-data in 2015), data set D (439,767 test-data in 2020-2023), data set E (399,279 test-data in 2019-2020)) in combination with the differential somatic cell count (DSCC) in data set D and E, or individual recordings of daily feed and energy intake and milk analysis (data set B (58,235 test-data in 2014-2017) and data set C (352,346 test-data in 2018-2021)), were analyzed. The group of cows with severe energy deficiency showed a 11.0 to 20 mg/l higher milk urea content than cows with a demand-orientated energy supply. The results for the effect of a very high energy supply are inconsistent across the 5 data sets. Furthermore, the milk urea content of cows with the highest somatic cell count are observed to be 9.0 to 13.0 mg/l lower in comparison to cows with a healthy udder. Moreover, the milk urea content is 14 mg/l lower in cows diagnosed with mastitis compared with those without a diagnosis. While this may have impact on judgements for the individual cow, in groups of cows, individual incidences of a disease will not have a significant impact on the average milk urea content. However, this should be taken into account for herds with a high prevalence of sick cows.

Predicting subacute ruminal acidosis from milk mid-infrared estimated fatty acids and machine learning on Canadian commercial dairy herds

Our objective was to validate the possibility of detecting SARA from milk Fourier transform mid-infrared spectroscopy estimated fatty acids (FA) and machine learning. Subacute ruminal acidosis is a common condition in modern commercial dairy herds for which diagnosis remains challenging due to its symptoms often being subtle, nonexclusive, and not immediately apparent. This observational study aimed at evaluating the possibility of predicting SARA by developing machine learning models to be applied to farm data and to provide an estimated portrait of SARA prevalence in commercial dairy herds. A first dataset, composed of 488 milk samples from 67 cows (initial DIM = 8.5 ± 6.18; mean ± SD) from 7 commercial dairy farms and their corresponding SARA classification (SARA+ if rumen pH <6.0 for 300 min, otherwise SARA-) was used for the development of machine learning models. Three sets of predictive variables (milk major components [MMC], milk FA [MFA], and MMC combined with MFA [MMCFA]) were submitted to 3 different algorithms, namely elastic net (EN), extreme gradient boosting, and partial least squares, and evaluated using 3 different scenarios of cross-validation. The accuracy, sensitivity, and specificity of the resulting 27 models were analyzed using a linear mixed model. Model performance was not significantly affected by the choice of algorithm. Model performance was improved by including FA estimations (MFA and MMCFA as opposed to MMC alone). Based on these results, 1 model was selected (algorithm: EN; predictive variables: MMCFA; 60.4%, 65.4%, and 55.3% of accuracy, sensitivity, and specificity, respectively) and applied to a large dataset comprising the first test-day record (milk major components and FA within the first 70 DIM of 211,972 Holstein cows [219,503 samples]) collected from 3,001 commercial dairy herds. Based on this analysis, the within-herd SARA prevalence of commercial farms was estimated at 6.6 ± 5.29% ranging from 0% to 38.3%. A subsequent linear mixed model was built to investigate the herd-level factors associated with higher within-herd SARA prevalence. Milking system, proportion of primiparous cows, herd size, and seasons were all herd-level factors affecting SARA prevalence. Furthermore, milk production was positively associated with SARA prevalence, and milk fat yield was negatively associated. Due to their moderate levels of accuracy, the SARA prediction models developed in our study, using data from continuous pH measurements on commercial farms, are not suitable for diagnostic purposes. However, these models can provide valuable information at the herd level.

Lyophilized rumen fluid as a ruminal fermentation modifier in high grain-fed acidotic goats

Rumen cud transfaunation re-establishes rumen micro environment and improves fermentation in recipient animals affected with digestive disorders. Preserving rumen cud or fluid will increase its availability for the treatment of rumen fermentation disorders, without having to maintain donor animals. Rumen fluid collected from healthy goats, fed standard ration having roughage 70% and concentrate 30%, was lyophilized (prefreezing -80 °C, 48 h; lyophilization -45 °C, 32 h) using 5% glycerol as cryoprotectant. The 16 S metagenome analysis of the lyophilized rumen fluid (LRF) revealed an abundance of Prevotella (33.2%). Selenomonas ruminantium (1.87%) and Megasphaera elsdenii (0.23%) were also present. Twenty-four goats having history of high grain feeding and exhibiting clinical symptoms of rumen fermentation disorders were randomly distributed into either one of the two treatment groups viz., T1 = oral administration of LRF 31 g/animal/day and T2 = oral administration of sodium bicarbonate (SB) 15 g/animal/day. Post intervention LRF and SB, improved animal body condition, feed intake, fecal consistency, elevated the ruminal pH at 48 h, reduced propionate and lactate at 48 h, reduced total volatile fatty acids (TVFA) and ammonia nitrogen at 24 h. Significant reduction in serum blood urea nitrogen (BUN) and urea levels were observed even from 24 h post intervention irrespective of the treatments. LRF significantly improved acetate and decreased propionate production compared to SB. LRF at 7.5% (v/v) can thus be used to counteract ruminal fermentation disorders in goats sequel to high grain ration.

The Most Important Metabolic Diseases in Dairy Cattle during the Transition Period

This review paper provides an in-depth analysis of three critical metabolic diseases affecting dairy cattle such as subacute ruminal acidosis (SARA), ketosis, and hypocalcemia. SARA represents a disorder of ruminal fermentation that is characterized by extended periods of depressed ruminal pH below 5.5-5.6. In the long term, dairy herds experiencing SARA usually exhibit secondary signs of the disease, such as episodes of laminitis, weight loss and poor body condition despite adequate energy intake, and unexplained abscesses usually 3-6 months after an episode of SARA. Depressed milk-fat content is commonly used as a diagnostic tool for SARA. A normal milk-fat test in Holstein dairy cows is >4%, so a milk-fat test of <3% can indicate SARA. However, bulk tank testing of milk fat is inappropriate to diagnose SARA at the herd level, so when >4 cows out of 12 and <60 days in milk are suspected to have SARA it can be considered that the herd has a problem. The rapid or abrupt introduction of fresh cows to high-concentrate diets is the most common cause of SARA. Changes in ruminal bacterial populations when exposed to higher concentrate rations require at least about 3 weeks, and it is recommended that concentrate levels increase by no more than 400 g/day during this period to avoid SARA. Ketosis, a prevalent metabolic disorder in dairy cattle, is scrutinized with a focus on its etiological factors and the physiological changes leading to elevated ketone bodies. In total mix ration-fed herds, an increased risk of mastitis and reduced fertility are usually the first clinical signs of ketosis. All dairy cows in early lactation are at risk of ketosis, with most cases occurring in the first 2-4 weeks of lactation. Cows with a body condition score ≥3.75 on a 5-point scale at calving are at a greater risk of ketosis than those with lower body condition scores. The determination of serum or whole blood acetone, acetoacetate, beta-hydroxybutyrate (BHB) concentration, non-esterified fatty acids (NEFA), and liver biopsies is considered the best way to detect and monitor subclinical ketosis, while urine or milk cowside tests can also be used in on-farm monitoring programs. Concentrations >1.0 mmol/L or 1.4 mmol/L blood or serum BHB are considered diagnostic of subclinical ketosis. The standard threshold used for blood is 1.2 mmol/L, which corresponds to thresholds of 100 mcmol/L for milk and 15 mg/dL for urine. Oral administration of propylene glycol (250-400 g, every 24 h for 3-5 days) is the standard and most efficacious treatment, as well as additional therapy with bolus glucose treatment. Hypocalcemia is a disease of adult dairy cows in which acute hypocalcemia causes acute to peracute, afebrile, flaccid paralysis that occurs most commonly at or soon after parturition. Dairy cows are at considerable risk for hypocalcemia at the onset of lactation, when daily calcium excretion suddenly increases from about 10 g to 30 g per day. Cows with hypocalcemia have a more profound decrease in blood calcium concentration-typically below 5.5 mg/dL. The prevention of parturient paresis has been historically approached by feeding cows low-calcium diets during the dry period. Negative calcium balance triggers calcium mobilization before calving and better equips the cow to respond to the massive calcium needs at the onset of lactation. Calcium intake must be limited to <20 g per day for calcium restriction to be effective. The most practical and proven method for monitoring hypocalcemia is by feeding cows an acidogenic diet for ~3 weeks before calving. Throughout the review, emphasis is placed on the importance of early diagnosis and proactive management strategies to mitigate the impact of these metabolic diseases on dairy cattle health and productivity. The comprehensive nature of this paper aims to serve as a valuable resource for veterinarians, researchers, and dairy farmers seeking a deeper understanding of these prevalent metabolic disorders in dairy cattle.

High-Dose Vitamin E Supplementation Can Alleviate the Negative Effect of Subacute Ruminal Acidosis in Dairy Cows

The aim of this trial was to assess whether the supplementation of vitamin E (VE) in high-concentrate diets could improve the fermentation and blood metabolism in the rumen of dairy cows, thereby modulating the degree of the subacute ruminal acidosis (SARA) response and improving the performance. Seven Holstein cows (four fitted with ruminal cannulas) were fed three diets (total mixed rations) during three successive periods (each lasted for 18 d): (1) the control diet (CON); (2) a high-grain (HG) diet, which was the control diet supplied with a 15% finely ground wheat diet (FGW); and (3) a high-VE diet (HGE), which was the control diet provided with a 15% FGW and 12,000 IU of VE/head per day. The results indicated that VE was able to alleviate the reduction in the dry matter intake (DMI) and milk fat yield in cows caused by HG diets. The supplementation of VE significantly reduced the levels of lipopolysaccharide (LPS), histamine (HIS), and the total volatile fatty acid (TVFA) in the rumen. The supplementation of VE observably increased the antioxidant capacity of the milk and plasma. In addition, VE markedly reduced the plasma levels of endotoxin, HIS, and pro-inflammatory factors. The supplementation of VE significantly enriched the differential metabolites of the purine metabolism, cysteine, methionine metabolism, and ABC transporter synthesis pathway in the serum. The supplementation of VE also significantly increased the relative abundance of Succiniclasticum and decreased the relative abundance of Treponema, thus reducing the production of TVFA in the rumen. In conclusion, considering that the cows in this trial had high ketone levels (BHBA > 2.3 mmol/L), we found that VE could improve the rumen fermentation and blood metabolism by modulating the relative abundance of rumen microorganisms, thereby mitigating a range of adverse effects caused by SARA.

The effect of ruminal fluid pH on milk fatty acids composition in cattle

The present study aimed to evaluate the effects of ruminal fluid pH on the fatty acids (FA) profile of bovine milk. The experiment was performed on 250 Polish Holstein-Friesian cows reared in 11 commercial high-yielding dairy farms. Ruminal fluid samples were collected by rumenocentesis, and fat and FA concentrations in milk were analyzed by Fourier transform infrared spectroscopy. According to ruminal fluid pH, cows were categorized into three pH groups: high pH (pH > 5.8), moderate pH (pH 5.8–5.6), and low pH (pH < 5.6). Milk produced by low-rumen pH cows had a decreased fat content as compared to milk from moderate- and high-rumen pH cows (P ≤ 0.05). Moreover, milk from low-rumen pH cows was characterized by the lowest level of short-chain FA (SCFA; P ≤ 0.05), and consequently, the highest medium-chain FA to SCFA ratio (P ≤ 0.01). The regression analysis showed that these traits explained a small proportion of rumen pH variance, which makes them unreliable indicators of subacute ruminal acidosis (SARA) in dairy cows. However, despite the extensive variability in milk fat composition observed in this study, the effect of ruminal pH on SCFA in all the analyzed herds showed the same trend. Future research aimed to identify SARA biomarkers should therefore be conducted using techniques that allow detection of more individual FA in milk, including SCFA.

Impact of Nutrients on the Hoof Health in Cattle

Lameness is currently one of the most important and economically demanding diseases in cattle. It is manifested in a change in locomotion that is associated with lesions, especially the pelvic limbs. The disease of the hoof is painful, affecting the welfare of dairy cows. Important factors that influence the health of the limbs include nutrition, animal hygiene, stable technology, and genetic and breeding predispositions. Nutrition is one of the basic preventive factors affecting the quality and growth of the hoof horn, and the associated prevalence of hoof disease. The strength and structure of the hoof horn are affected by the composition of the feed ration (amino acids, minerals, vitamins, and toxic substances contaminating the feed ration, or arising in the feed ration as metabolites of fungi).