Dietary fatty acids and oxidative stress in the heart mitochondria

The impacts of diet on cardiac performance under changing environments

Natural and anthropogenic stressors are dramatically altering environments, impacting key animal physiological traits, including cardiac performance. Animals require energy and nutrients from their diet to support cardiac performance and plasticity; however, the nutritional landscape is changing in response to environmental perturbations. Diet quantity, quality and options vary in space and time across heterogeneous environments, over the lifetime of an organism and in response to environmental stressors. Variation in dietary energy and nutrients (e.g. lipids, amino acids, vitamins, minerals) impact the heart's structure and performance, and thus whole-animal resilience to environmental change. Notably, many animals can alter their diet in response to environmental cues, depending on the context. Yet, most studies feed animals ad libitum using a fixed diet, thus underestimating the role of food in impacting cardiac performance and resilience. By applying an ecological lens to the study of cardiac plasticity, this Commentary aims to further our understanding of cardiac function in the context of environmental change.

Cardiac Involvement in Mitochondrial Disorders

PURPOSE OF REVIEW

We review pathophysiology and clinical features of mitochondrial disorders manifesting with cardiomyopathy.

RECENT FINDINGS

Mechanistic studies have shed light into the underpinnings of mitochondrial disorders, providing novel insights into mitochondrial physiology and identifying new therapeutic targets. Mitochondrial disorders are a group of rare genetic diseases that are caused by mutations in mitochondrial DNA (mtDNA) or in nuclear genes that are essential to mitochondrial function. The clinical picture is extremely heterogeneous, the onset can occur at any age, and virtually, any organ or tissue can be involved. Since the heart relies primarily on mitochondrial oxidative metabolism to fuel contraction and relaxation, cardiac involvement is common in mitochondrial disorders and often represents a major determinant of their prognosis.

Effect of Oils in Feed on the Production Performance and Egg Quality of Laying Hens

With the development of a large-scale and intensive production industry, the number of laying hens in China is rapidly increasing. Oils, as an important source of essential fatty acids, can be added to the diet to effectively improve the production performance and absorption of other nutrients. The present review discusses the practical application of different types and qualities of oils in poultry diets and studies the critical effects of these oils on production performance, such as the egg weight, feed intake, feed conversion ratio (FCR), and various egg quality parameters, including the albumen height, Haugh units, yolk color, and saturated/unsaturated fatty acids. This article reviews the effects of different dietary oil sources on the production performance and egg quality of laying hens and their potential functional mechanisms and provides a reference for the selection of different sources of oils to include in the diet with the aim of improving egg production. This review thus provides a reference for the application of oils to the diets of laying hens. Future studies are needed to determine how poultry products can be produced with the appropriate proper oils in the diet and without negative effects on production performance and egg quality.

Intestinal and Hepatic Uptake of Dietary Peroxidized Lipids and Their Decomposition Products, and Their Subsequent Effects on Apolipoprotein A1 and Paraoxonase1

Both pro- and antiatherosclerotic effects have been ascribed to dietary peroxidized lipids. Confusion on the role of peroxidized lipids in atherosclerotic cardiovascular disease is punctuated by a lack of understanding regarding the metabolic fate and potential physiological effects of dietary peroxidized lipids and their decomposition products. This study sought to determine the metabolic fate and physiological ramifications of 13-hydroperoxyoctadecadienoic acid (13-HPODE) and 13-HODE (13-hydroxyoctadecadienoic acid) supplementation in intestinal and hepatic cell lines, as well as any effects resulting from 13-HPODE or 13-HODE degradation products. In the presence of Caco-2 cells, 13-HPODE was rapidly reduced to 13-HODE. Upon entering the cell, 13-HODE appears to undergo decomposition, followed by esterification. Moreover, 13-HPODE undergoes autodecomposition to produce aldehydes such as 9-oxononanoic acid (9-ONA). Results indicate that 9-ONA was oxidized to azelaic acid (AzA) rapidly in cell culture media, but AzA was poorly absorbed by intestinal cells and remained detectable in cell culture media for up to 18 h. An increased apolipoprotein A1 (ApoA1) secretion was observed in Caco-2 cells in the presence of 13-HPODE, 9-ONA, and AzA, whereas such induction was not observed in HepG2 cells. However, 13-HPODE treatments suppressed paraoxonase 1 (PON1) activity, suggesting the induction of ApoA1 secretion by 13-HPODE may not represent functional high-density lipoprotein (HDL) capable of reducing oxidative stress. Alternatively, AzA induced both ApoA1 secretion and PON1 activity while suppressing ApoB secretion in differentiated Caco-2 cells but not in HepG2. These results suggest oxidation of 9-ONA to AzA might be an important phenomenon, resulting in the accumulation of potentially beneficial dietary peroxidized lipid-derived aldehydes.

Insulin sensitization causes accelerated sinus nodal dysfunction through autophagic dysregulation in hypertensive mice

Insulin sensitizers, while effective in glucose-lowering for diabetes control, are linked to an increased risk of heart disease through mechanisms that are not well understood. In this study, we investigated the molecular mechanisms underlying the effects of insulin sensitization on cardiac sinus node dysfunction. We used pharmacologic or genetic approaches to enhance insulin sensitivity, by treating with pioglitazone or rosiglitazone, or through phosphatase and tensin homolog (PTEN) deletion in cardiomyocytes respectively. We employed an angiotensin II (Ang II)-induced hypertensive animal model which causes sinus node dysfunction and accumulation of oxidized calcium/calmodulin-dependent protein kinase II (CaMKII), which also serves as a biomarker for this defect. While neither PTEN deficiency nor insulin sensitizers caused sinus node dysfunction in normotensive mice, both accelerated the onset of sinus node dysfunction and CaMKII oxidation in hypertensive mice. These abnormalities were accompanied by a significant defect in autophagy as revealed by unc-51 like autophagy activating kinase 1 (ULK1) signaling. Indeed, mice deficient in ulk1 in cardiomyocytes and the sinus node also showed early onset of slow atrial impulse conduction with frequent sinus pauses and upregulated CaMKII oxidation following Ang II infusion similar to that seen with PTEN deficiency, or treatment with insulin sensitizers. To further elucidate the role of autophagy in sinus node dysfunction, we treated mice with a peptide D-Tat-beclin1 that enhanced autophagy, which significantly abrogated the frequent sinus pauses and accumulation of oxidized CaMKII induced by insulin sensitizers treatment, or PTEN deficiency in hypertensive animals. Together, these findings provide clear evidence of the detrimental cardiac effects of insulin sensitization that occurs through failure of autophagy-mediated proteolytic clearance.

The effect of selenium source on the oxidative status and performance of broilers reared at standard and high ambient temperatures

1. This study investigated the oxidative status of broilers fed diets containing selenium (Se) from 14 to 35 d of age and reared at two different constant temperatures. Measurements of oxidative status included blood glutathione peroxidase (GSH-Px) and plasma total antioxidant status (TAS). Other variables included feed intake (FI), weight gain (WG), feed conversion ratio (FCR), Se levels in breast and liver tissue, jejunal villus morphometry, percentage weight of organs in relation to body weight; apparent metabolisable energy adjusted for nitrogen (AMEn); dry matter retention (DMR); fat retention (FR) and nitrogen retention (NR).2. The experiment started at 14 d of age, when 240 birds were randomly allocated to 48 pens (12 pens in four rooms). Treatments included a control diet 1 (SFC; 209.4 g/kg CP and 12.98 MJ/kg ME and no added Se containing saturated fat); diet 2 (SFSe) the control plus 12.605 mg/kg Se additive; diet 3 (USFC) was a second control diet (208.2 g/kg CP and 13.10 MJ/kg ME with no added Se containing unsaturated fat as rapeseed oil); diet 4 (USFSe) was the latter control plus 12.605 mg/kg Se additive. Two rooms were kept at a standard temperature of 20°C (ST) and two rooms were kept at high temperature of 35°C (HT).3. A temperature x Se interaction existed for GSH-Px in birds reared at ST (P < 0.05), and these birds had the highest levels of Se in liver tissue (P < 0.05). Fat x Se interactions were evident in breast tissue with highest levels in USFSe (P < 0.05). Adding Se improved jejunal VH: CD in USFSe fed birds (P < 0.001).4. Birds reared at ST had higher FI and WG than those reared at HT (P < 0.001), and had lower FCR than those reared at HT (P < 0.05). AMEn (MJ/kg DM) and FR were higher in birds fed USF diets, and lowest in birds fed SF (P < 0.50 and P < 0.001 respectively). NR was highest in birds raised at ST (P < 0.50).5. Broiler growth performance was reduced by HT. Oxidative status and Se in liver tissue was improved by adding Se in both diets.

Age and sex as confounding factors in the relationship between cardiac mitochondrial function and type 2 diabetes in the Nile Grass rat

Our study revisits the role of cardiac mitochondrial adjustments during the progression of type 2 diabetes mellitus (T2DM), while considering age and sex as potential confounding factors. We used the Nile Grass rats (NRs) as the animal model. After weaning, animals were fed either a Standard Rodent Chow Diet (SRCD group) or a Mazuri Chinchilla Diet (MCD group) consisting of high-fiber and low-fat content. Both males and females in the SRCD group, exhibited increased body mass, body mass index, and plasma insulin compared to the MCD group animals. However, the females were able to preserve their fasting blood glucose throughout the age range on both diets, while the males showed significant hyperglycemia starting at 6 months in the SRCD group. In the males, a higher citrate synthase activity-a marker of mitochondrial content-was measured at 2 months in the SRCD compared to the MCD group, and this was followed by a decline with age in the SRCD group only. In contrast, females preserved their mitochondrial content throughout the age range. In the males exclusively, the complex IV capacity expressed independently of mitochondrial content varied with age in a diet-specific pattern; the capacity was elevated at 2 months in the SRCD group, and at 6 months in the MCD group. In addition, females, but not males, were able to adjust their capacity to oxidize long-chain fatty acid in accordance with the fat content of the diet. Our results show clear sexual dimorphism in the variation of mitochondrial content and oxidative phosphorylation capacity with diet and age. The SRCD not only leads to T2DM but also exacerbates age-related cardiac mitochondrial defects. These observations, specific to male NRs, might reflect deleterious dietary-induced changes on their metabolism making them more prone to the cardiovascular consequences of aging and T2DM.

Low-dose ethanol intake prevents high-fat diet-induced adverse cardiovascular events in mice

This study aimed to clarify whether low-dose ethanol intake could prevent high-fat diet-induced adverse effects on cardiomyocytes in mice.

Thermal tolerance and fish heart integrity: fatty acids profiles as predictors of species resilience

The cardiovascular system is a major limiting system in thermal adaptation, but the exact physiological mechanisms underlying responses to thermal stress are still not completely understood. Recent studies have uncovered the possible role of reactive oxygen species production rates of heart mitochondria in determining species' upper thermal limits. The present study examines the relationship between individual response to a thermal challenge test (CT_max), susceptibility to peroxidation of membrane lipids, heart fatty acid profiles and cardiac antioxidant enzyme activities in two salmonid species from different thermal habitats (Salvelinus alpinus, Salvelinus fontinalis) and their hybrids. The susceptibility to peroxidation of membranes in the heart was negatively correlated with individual thermal tolerance. The same relationship was found for arachidonic and eicosapentaenoic acid. Total H₂O₂ buffering activity of the heart muscle was higher for the group with high thermal resistance. These findings underline a potential general causative relationship between sensitivity to oxidative stress, specific fatty acids, antioxidant activity in the cardiac muscle and thermal tolerance in fish and likely other ectotherms. Heart fatty acid profile could be indicative of species resilience to global change, and more importantly the plasticity of this trait could predict the adaptability of fish species or populations to changes in environmental temperature.

Porcine bile powder supplementation of a high fat broiler diet in relation to growth performance and nutrient digestion

The aim of the study was to examine the effect of pig bile powder supplementation on the digestibility of nutrients, fat digestion and growth performance of starter broilers fed on a high fat diet. A total of 1110, day-old, male broiler chicks (Arbor Acres) were randomly allocated into six treatment groups with five replicates per treatment. The chicks were fed on a corn-soybean meal basal diet with a starter formulation until Day 14, followed by a grower formulation until Day 21. In group 1 (T1), the basal diet contained 30 g/kg crude palm oil whereas the diet used in group 2 (T2) had 60 g/kg crude palm oil. Chicks in group 3 (T3) were fed on T2 diet supplemented with 5.0 g/kg soy lecithin as the positive control. Chicks in groups 4–6 (T4–T6) received diets used in T2, supplemented with 1.25, 2.5 and 5.0 g/kg lyophilised pig bile powder, respectively. On Days 4, 7, 14 and 21, chicks were killed, portal blood was collected and analysed for fatty acids, pancreas collected for measurement of pancreatic lipase activity, bile and jejunal contents for bile acid determination and ileal content for determining digestibility of fat and protein. The results showed (1) there was no difference in bodyweight and feed intake among T2–T6, (2) pancreatic lipase activity of chicks in T4 and T5 was highest in all periods. Total bile acid concentrations in the gall bladder and jejunum in T4 was lower than those in T2 in all periods, and Days 4 and 7, respectively, (3) digestibility of protein and fat in T3 and T4 was higher in all the period than that of T2, T5 and T6, (4) increased fat content in the diet did not cause a significant increase in any fatty acids in the portal plasma when compared T1 and T2. In conclusion, 2.5 g/kg porcine bile powder supplemented in high fat diet increased pancreatic lipase activity and total bile acid concentrations in gall bladder, resulting in increased ileal digestibility of fat and protein.

Comparative Effect of Dietary Soybean Oil, Fish Oil, and Coconut Oil on Performance, Egg Quality and Some Blood Parameters in Laying Hens

Two hundred and sixteen 28-wk-old Hy-line laying hens were randomly distributed to three dietary treatments and fed 1of 3 diets containing 8% soybean oil, fish oil, or coconut oil from 28 to 47 wk of age to investigate comparative effect of dietary soybean oil, fish oil, and coconut oil on the performance, egg quality and blood malondialdehyde (MDA), aspartate transaminase (AST) and uric acid (UA). Hens fed fish oil showed poor performance compared with soybean oil or coconut oil, and especially egg weight throughout the trial was significantly and consistently decreased (P < 0.05) due to dietary fish oil. Unexpectedly, shell reflectivity throughout the majority of the trial was consistently and significantly higher (P < 0.05) when hens fed fish oil than that when fed soybean oil or coconut oil. Dietary treatments affected (P < 0.05) shell shape at 4 of 8 time points tested. Average shell shape in fish oil treatment was higher (P < 0.05) than that of coconut oil group. Albumen height, Haugh unit and yolk color were influenced by dietary treatments only at 1 or 2 time points. However, average albumen height and Haugh unit in fish oil treatment were higher (P < 0.05) than that of soybean oil or coconut oil treatments and average yolk color in coconut oil treatment was higher (P < 0.05) than that of soybean oil group. Serum MDA, AST and UA concentrations were increased (P < 0.05) by fish oil during the majority of the first 2 mo of the trial. These data suggested that the inclusion of fish oil into feed may reduce the performance of laying hens, especially the egg weight, decrease the intensity of egg brown color and increase blood MDA, AST and UA levels compared with soybean oil or coconut oil. As a result, hens fed fish oil may lay smaller, longer and lighter-brown eggs whereas those fed coconut oil produce blunter and darker-brown eggs relative to soybean oil.

Thermal tolerance and thermal sensitivity of heart mitochondria: Mitochondrial integrity and ROS production

Cardiac mitochondrial metabolism provides 90% of the ATP necessary for the contractile exertion of the heart muscle. Mitochondria are therefore assumed to play a pivotal role in heart failure (HF), cardiovascular disease and ageing. Heat stress increases energy metabolism and oxygen demand in tissues throughout the body and imposes a major challenge on the heart, which is suspected of being the first organ to fail during heat stress. The underlying mechanisms inducing heart failure are still unclear. To pinpoint the processes implicated in HF during heat stress, we measured mitochondrial respiration rates and hydrogen peroxide production of isolated Arctic char (Salvelinus alpinus) heart mitochondria at 4 temperatures: 10°C (acclimation), 15°C, 20°C and 25°C (just over critical maximum). We found that at temperature ranges causing the loss of an organism's general homeostasis (between 20°C and 25°C) and with a substrate combination close to physiological conditions, the heat-induced increase in mitochondrial oxygen consumption levels off. More importantly, at the same state, hydrogen peroxide efflux increased by almost 50%. In addition, we found that individuals with low mitochondrial respiration rates produced more hydrogen peroxide at 10°C, 15°C and 20°C. This could indicate that individuals with cardiac mitochondria having a low respiratory capacity, have a more fragile heart and will be more prone to oxidative stress and HF, and less tolerant to temperature changes and other stressors. Our results show that, at temperatures close to the thermal limit, mitochondrial capacity is compromised and ROS production rates increase. This could potentially alter the performance of the cardiac muscle and lead to heat-induced HF underlining the important role that mitochondria play in setting thermal tolerance limits.

Adjuvant potential of virgin coconut oil extract on antiretroviral therapy-induced testicular toxicity: An ultrastructural study

The effects of Virgin coconut oil as an adjuvant to highly active antiretroviral therapy (HAART) were investigated on the testicular ultrastructure and biochemical markers in rats. Twenty male Sprague-Dawley rats, weighing 153-169 g were divided into four groups and treated as follows: control A (distilled water), B (HAART), C (HAART+Virgin coconut oil 10 ml/kg) and D (Virgin coconut oil [VCO] 10 ml/kg). Testicular segments were evaluated using transmission electron microscopy. Serum was assayed for testosterone, luteinising hormone, follicle stimulating hormone and testicular tissue for malondialdehyde and glutathione. Ultrastructure of basement membrane (Bm), mitochondria and spermatocytes was normal in the control group. HAART-treated group showed significant increase (p < .01) in Bm thickness with significant decrease in Leydig cell nuclear diameter (p < .05) and volume (p < .01) when compared with control group. Mitochondrial cristae appear collapsed, and Sertoli cells showed cytoplasmic vacuolations. HAART+VCO group showed improved ultrastructural details in Bm, and Sertoli cell and Leydig cells show abundant lipid droplets. Virgin coconut oil-treated group showed thinning of Bm with otherwise normal ultrastructural features of organelles. HAART-treated group showed significant increase (p < .01) in testosterone levels. There was no significant effect on malondialdehyde and glutathione levels. Virgin coconut oil improved testicular morphology and reversed HAART-induced ultrastructural alterations. Further studies on putative mechanism are required.

Mitochondria Associated MicroRNA Expression Profiling of Heart Failure

Heart failure (HF) is associated with mitochondrial dysfunction and energy metabolism impairment. MicroRNAs are implicated in the development of heart failure. However, the mitochondria enriched microRNA during heart failure remains elusive. Here, we generated a pressure overload-induced early and late stage heart failure model at 4 weeks and 8 weeks following transverse aortic constriction (TAC) in mice. We found that expression of mitochondrion protein COX4 was highly enriched in isolated mitochondria from cardiac tissues while GAPDH could hardly be detected. Furthermore, small RNA sequencing for mitochondria RNAs from failing hearts was performed. It was found that 69 microRNAs were upregulated and 2 were downregulated in early heart failure, while 16 microRNAs were upregulated and 6 were downregulated in late heart failure. 15 microRNA candidates were measured in both mitochondria and total cardiac tissues of heart failure by real-time PCR. MiR-696, miR-532, miR-690, and miR-345-3p were enriched in mitochondria from the failing heart at early stage. Bioinformatics analysis showed that mitochondria enriched microRNAs in HF were associated with energy metabolism and oxidative stress pathway. For the first time, we demonstrated microRNAs were enriched in mitochondria during heart failure, which established a link between microRNA and mitochondrion in heart failure.

The Impact of Virgin Coconut Oil and High-Oleic Safflower Oil on Body Composition, Lipids, and Inflammatory Markers in Postmenopausal Women

This randomized crossover study compared the impact of virgin coconut oil (VCO) to safflower oil (SO) on body composition and cardiovascular risk factors. Twelve postmenopausal women (58.8 ± 3.7 year) consumed 30 mL VCO or SO for 28 days, with a 28-day washout. Anthropometrics included body weight and hip and waist circumference. Fat percent for total body, android and gynoid, fat mass, and lean mass were measured using dual-energy X-ray absorptiometry. Women maintained their typical diet recording 28 days of food records during the study. Results were analyzed with SPSS v24 with significance at P ≤ .05. Comparisons are reported as paired t-test since no intervention sequence effect was observed. VCO significantly raised total cholesterol, TC (+18.2 ± 22.8 mg/dL), low-density lipoprotein (+13.5 ± 16.0 mg/dL), and high-density lipoprotein, HDL (+6.6 ± 7.5 mg/dL). SO did not significantly change lipid values. TC and HDL were significantly different between test oils. The TC/HDL ratio change showed a neutral effect of both VCO and SO. One person had adverse reactions to VCO and increased inflammation. VCO decreased IL-1β for each person who had a detected sample. The impact of VCO and SO on other cytokines varied on an individual basis. This was the first study evaluating the impact of VCO on body composition in Caucasian postmenopausal women living in the United States. Results are suggestive that individuals wishing to use coconut oil in their diets can do so safely, but more studies need to be conducted with larger sample sizes, diverse populations, and more specific clinical markers such as particle size.

Free Fatty Acid Effects on the Atrial Myocardium: Membrane Ionic Currents Are Remodeled by the Disruption of T-Tubular Architecture

BACKGROUND

Epicardial adiposity and plasma levels of free fatty acids (FFAs) are elevated in atrial fibrillation, heart failure and obesity, with potentially detrimental effects on myocardial function. As major components of epicardial fat, FFAs may be abnormally regulated, with a potential to detrimentally modulate electro-mechanical function. The cellular mechanisms underlying such effects of FFAs are unknown.

OBJECTIVE

To determine the mechanisms underlying electrophysiological effects of palmitic (PA), stearic (SA) and oleic (OA) FFAs on sheep atrial myocytes.

METHODS

We used electrophysiological techniques, numerical simulations, biochemistry and optical imaging to examine the effects of acutely (≤ 15 min), short-term (4-6 hour) or 24-hour application of individual FFAs (10 μM) on isolated ovine left atrial myocytes (LAMs).

RESULTS

Acute and short-term incubation in FFAs resulted in no differences in passive or active properties of isolated left atrial myocytes (LAMs). 24-hour application had differential effects depending on the FFA. PA did not affect cellular passive properties but shortened (p<0.05) action potential duration at 30% repolarization (APD30). APD50 and APD80 were unchanged. SA had no effect on resting membrane potential but reduced membrane capacitance by 15% (p<0.05), and abbreviated APD at all values measured (p≤0.001). OA did not significantly affect passive or active properties of LAMs. Measurement of the major voltage-gated ion channels in SA treated LAMs showed a ~60% reduction (p<0.01) of the L-type calcium current (ICa-L) and ~30% reduction (p<0.05) in the transient outward potassium current (ITO). A human atrial cell model recapitulated SA effects on APD. Optical imaging showed that SA incubated for 24 hours altered t-tubular structure in isolated cells (p<0.0001).

CONCLUSIONS

SA disrupts t-tubular architecture and remodels properties of membrane ionic currents in sheep atrial myocytes, with potential implications in arrhythmogenesis.

Oral supplementation of medium-chain fatty acids during the dry period supports the neutrophil viability of peripartum dairy cows

A randomised clinical trial was conducted to explore the effect of orally supplemented medium-chain fatty acids (MCFA) to heifers and cows starting 6-8 weeks prior to expected calving date on blood and milk polymorphonuclear neutrophilic leucocyte (PMNL) apoptosis between 1 and 3 d in milk (DIM). The effects of MCFA-supplementation on the likelihood of intramammary infections (IMI) in early lactation, and test-day somatic cell count (SCC) and average daily milk yield (MY) during the first 4 months of lactation were evaluated as well. Twenty-two animals were included of which half were orally supplemented with MCFA starting 6-8 weeks prior to calving and half served as non-supplemented controls. The PMNL viability in both blood and milk was quantified using dual-colour flow cytometry with fluorescein-labelled annexin and propidium iodide. In non-supplemented animals, % blood PMNL apoptosis significantly increased between start of supplementation and early lactation, reflecting a potential reduction in innate immune capacity, whereas this was not true in the MCFA-supplemented animals. Similar results were seen in milk PMNL apoptosis. Overall, the % apoptotic milk PMNL between 1 and 3 DIM was significantly lower in the MCFA-supplemented group compared with the non-supplemented group. There was no substantial effect of oral MCFA-supplementation on the likelihood of quarter IMI nor on the composite test-day milk SCC or average daily MY. In conclusion, oral MCFA-supplementation starting 6-8 weeks before expected calving date supported the blood and milk neutrophil viability in early lactating dairy cows. Still, this was not reflected in an improvement of udder health nor MY in early and later lactation. The results should trigger research to further unravel the mechanisms behind the observed immunomodulating effect, and the potential relevance for the cows' performances throughout lactation.