Milk Yield Research Articles

Clinical Findings, Laboratory Results, Electrocardiography and Echocardiography Findings in Dairy Buffaloes with Theileriosis.

Tropical theileriosis is a tick-borne haemoprotozoan disease, and cardiac function assessment in buffaloes with theileriosis was poorly documented. The Present study was carried out from April 2022 to December 2022. Theileriosis was confirmed by microscopic examination of stained blood smears and lymphnode smearsfurther confirmed by PCR assay. Electrocardiography was performed byusing the base apex lead system, and echocardiography was performed byusing the right parasternal view. The incidence of theileriosis was 16.25% by examination of stained blood smears, and 30.42% by PCR examination in 240 buffaloes. Repeatedly noted clinical signs were the absence of rumination, anorexia, loss of milk yield, depressed demeanour, emaciation, hyperthermia, lymphadenopathy, tick infestation, tachycardia, cardiac arrhythmia, and increased intensity of heartbeat. Haematological findings disclosed decreased haemoglobin, packed cell volume, total erythrocyte count, and neutrophils; increased eosinophils and monocytes. Serum biochemical findings revealed decreased albumin, albumin/globulin ratio, glucose, calcium, phosphorous, sodium, potassium, and chloride; increased globulin, aspartate aminotransferase, bilirubin, blood urea nitrogen, creatinine, cholesterol, lactate dehydrogenase, gamma-glutamyl transferase, and creatine kinase myocardial band isoenzymes. Electrocardiography explorations were sinus tachycardia, broad T wave, and sinus arrhythmia. Echocardiography examination showed ventricular wall thickening, cardiac chamber dilatation, valvular defects/valvular regurgitation, and pericarditis/cardiac tamponade. The present research proposes the changes in the electrocardiography and echocardiography findings in buffaloes with theileriosis, which are essential in clinics to identify the secondary complications during theileriosis and formulate therapeutics.

Mechanism of collagen type IV regulation by focal adhesion kinase during retained fetal membranes in dairy cows

Retained fetal membranes (RFM) is an important reproductive disease in dairy cows, caused by maternal and fetal placental tissue adhesion. The main collagen in maternal and fetal placenta tissues is collagen type IV (COL-IV) and its breakdown is the key to placental expulsion. Focal adhesion kinase (FAK) has been shown to regulate the hydrolysis of Col-IV by affecting the activity of MMP-2 and MMP-9 activity, but the regulation of the mechanisms involved in placenta expulsion in dairy cows after postpartum are still unclear. The aim of this study was to investigate the pathogenic mechanism of RFM by studying the relationship between the FAK signaling pathway and COL-IV regulation. Maternal placental tissues were collected from six healthy and six cows with RFM of similar age, parity, body condition and milk yield at 12 h postpartum. In vitro experiments were performed on bovine endometrial epithelial cells from three groups including a FAK inhibitor group, a FAK activator group and a control group without FAK inhibitor and activator. The abundance of molecules involved in the FAK signaling pathway and COL-IV was detected by immunohistochemistry, quantitative real-time polymerase chain reaction (qRT-PCR) and western blot. The immunohistochemical results showed that the key molecules of FAK signaling pathway FAK, Src, MMP-2 and MMP-9 and Col-IV were expressed in placental tissues. The expression level of FAK, Src, MMP-2, and MMP-9 were significantly down-regulated (P < 0.05) and the abundances of COL-IV were significantly up-regulated (P < 0.05) in maternal placental tissues of RFM cows compared with healthy cows. In the FAK inhibitor treatment group, the relative expression levels of FAK and other related proteins were significantly down-regulated (P < 0.05) and the relative expression levels of COL-IV were significantly up-regulated (P < 0.05) with the results of the FAK activation group the opposite. These results indicated that FAK in maternal endometrial epithelial cells could regulate the hydrolysis process of Col-IV through the expression of key factors of signaling pathways and promote collagen hydrolysis, which in turn facilitated the process of postpartum placenta expulsion in dairy cows.

Milk Production, Milk Composition, Milk Fatty Acid Profile and Nutrient Digestibility of Mehsana Goats Fed Sunflower (Helianthus annus) Oil

A study was conducted during the month of December, 2020 to January, 2021 at Livestock Research Station, Kamdhenu University, Sardarkrushinagar, Gujarat (385506), India to evaluate the effect of dietary sunflower oil supplementation on milk yield, milk fatty acid profile and nutrient digestibility of Mehsana goats. Eighteen lactating Mehsana goats were randomly divided into three treatment groups, viz. Basal diet (control), Basal diet+25 g animal-1 day-1 of sunflower oil and Basal diet+50 g animal-1 day-1 of sunflower oil for a period of 60 days. No significant differences (p&gt;0.05) were found in milk yield in terms of kg d-1, 4% fat corrected milk and energy corrected milk among the treatment groups. The milk constituents and their yields were not affected due to dietary inclusion of sunflower oil. Sunflower oil feeding at the dose of 50 g d-1 increased (p&lt;0.05) concentration of milk short chain fatty acids and polyunsaturated fatty acids in the milk of goats. The intake and digestibility of nitrogen free extract was increased in sunflower oil supplemented groups. The intake and digestibility of dry matter, organic matter, crude protein, ether extract and crude fibre were similar (p&gt;0.05) among the treatment groups. it may be concluded that supplementation of sunflower oil at the dose rate of 25 and 50 g d-1 did not affect feed intake, milk yield, milk constituents and nutrient digestibility in lactating Mehsana goats. However, dietary 50 g d-1 of sunflower oil significantly increased concentration of milk short chain fatty acids and polyunsaturated fatty acids in goats.

The effect of biochar supplementation on feed utilization, milk production and methane emission in lactating dairy cows

There is an increasing trend in agriculture to use biochar (BC) as a means for carbon storage and soil improvement, and it has been suggested, that feeding BC to livestock can improve animal health and performance, and reduce enteric methane emissions. The aim of this study was to investigate if adding BC to a balanced ration of a group of lactating Holstein dairy cows had an effect on their milk yield and quality, methane emission, nutrient digestibility and health. In a crossover experiment lasting for two 36-day periods, eight cows received their basal ration with and without 1 % DM BC. During the last week of each period, the cows were kept in tie stalls where milk yield and composition, feed intake and nutrient digestibility, as well as blood parameters were quantified. On the last two days, methane emissions were measured in respiration chambers. The results indicate that there was no significant effect of the addition of BC on any of the measured variables. Voluntary intake was not affected by the addition of BC (P=0.52) and none of the cows exhibited health problems in response to the treatment. There was no increase in milk yield (P>0.46) or composition (P>0.23) and methane emissions were not significantly affected (P>0.37). While the beneficial effects of feeding BC to animals suffering from health problems or receiving a poor diet cannot be excluded, the data of this experiment indicate that BC is not an effective feed additive to improve performance or reduce methane emission in dairy cows.

Interaction Effects of Somatic Cell Count and Milk Yield on Milk Composition in Lactating Dairy Cows: A Synergistic Analysis*

Interaction Effects of Somatic Cell Count and Milk Yield on Milk Composition in Lactating Dairy Cows: A Synergistic Analysis*

Effect of Bone Morphogenetic Protein Receptor-1B (BMPR-1B) Gene Variant on Litter Size in Akkaraman Sheep Breed

The BMPR-1B gene, a significant fertility gene, has been examined for its relationship with fertility characteristics in various sheep populations globally. This investigation explored the impact of the BMPR-1B gene on litter size within the Akkaraman sheep population residing in the Elâzığ Region. To locate the FecB gene in Akkaraman sheep, 104 milk samples were collected, and genetic material was isolated using the salting out technique. During the 2021–2022 period, no significant correlations were observed between the genetic make-up of Akkaraman sheep and factors including age, mastitis and disease history, milk yield, birthing type, and the number of births (p &gt; 0.05). However, there was a noteworthy relationship identified between the distribution of genetic make-up and live weight, indicating a potential influence of genetics on the live weight of Akkaraman sheep (p &lt; 0.05). In this study, the BMPR-1B gene determined multiple births and it was determined that Akkaraman sheep were monomorphic in terms of this gene. In light of this information, it was concluded that more comprehensive studies should be carried out regarding this gene determining multiple births in the Akkaraman sheep breed.

Detection of putative loci affecting milk yield in Turkish Awassi sheep using microsatellite markers.

On the basis of comparisons between bovine and ovine genome mapping information, the aim of the study was to analyze the genetic diversity of selected DNA microsatellites from the bovine genome and to investigate their correlation with the average daily milk yield in Awassi sheep. 18 informative microsatellite markers were selected from the significant QTL regions affecting milk yield identified in the bovine genome in previous studies. The selected microsatellite markers were then amplified by PCR as reciprocal amplifications on the genomic DNA of Awassi sheep, with standard daily milk yield records. Thus, in this study, 18 microsatellite markers associated with milk yield in the bovine genome were examined for both determination of genetic polymorphism within the flock and the effects of marker loci on average daily milk yield in Awassi sheep. Allele frequencies of markers were determined based on the results of fragment analysis. The analysis of variance showed that the 123bp allele at the marker locus BMS1341 on BTA2 significantly influenced the average daily milk yield of Ivesi sheep (P < 0.01). On the other hand, the BMS381 locus with a 115bp allele on BTA2, the MCM140 locus with a 185bp allele on BTA6, the BMS2721 locus with a 155bp allele, the BM1237 locus with 174 and 180bp alleles on BTA7, and finally, the BMS1967 locus with a 117bp allele, the BM4208 locus with 176 and 182bp alleles, and the INRA locus with a185 bp allele on BTA8 showed moderately significant effects on the average daily milk yield of Ivesi ewes (P < 0.05).

Patterns of variation and relationships among fat, protein, and milk yield of individual dairy cattle in a Thai multibreed population.

This study systematically examines the patterns of milk yield (MY, kg), fat (FAT, %), and protein (PROT, %) in a diverse population of Thai multibreed dairy cattle, considering the tropical environment's impact on lactating cows. Using a dataset of 47,205 monthly test-day records from 4,440 first-lactation cows across 446 farms, we analyze variations and interrelationships through mathematical averaging and introduce the fat-to-protein ratio (FPR) to assess acidosis (FPR < 1.1) and ketosis (FPR > 1.5) risks during lactation. Pearson correlation analysis elucidated trait associations. The findings, aligned with established lactation norms, indicate peak production at 297 days in milk (DIM) for FAT (4.08%; SD = 0.96%), PROT (3.43%; SD = 0.47%), and 52 DIM for MY (18.09kg; SD = 4.91kg). Nadirs are observed at 72 DIM for FAT (3.27%; SD = 0.74%), 47 DIM for PROT (2.86%; SD = 0.36%), and 299 DIM for MY (9.05kg; SD = 2.95kg). FPR variations highlight acidosis (46.48%), normal (43.66%), and ketosis (9.86%), especially during early lactation (100 DIM). Significant negative correlations emerge between MY, FAT, and PROT (P < 0.05), while a positive correlation is identified between FAT and PROT (P < 0.01), with robust correlations during early lactation. This study contributes to understanding tailored nutritional strategies for dairy cows' holistic health and sustainability in tropical environments, guiding efficient production practices and mitigating health-related productivity impediments.

Transforming the feeding regime towards low-input increases the environmental impact of organic milk production on a case study farm in central germany

Abstract Purpose Despite the direct effect of the feeding regime on the environmental impacts of dairy farming systems, its level of intensity, particularly in organic systems, has rarely been investigated. This study compares the environmental impact of a high-input feeding regime with a grassland-based, low-input feeding regime scenario within an organic milk production system conducted on Gladbacherhof, the research farm of Justus Liebig University Giessen, in Central Germany. Methods An integrated Life Cycle Assessment (LCA) analysis was performed from a cradle-to-farm gate perspective to quantify five environmental impacts, namely Global Warming (GW), Non-Renewable Energy Use (NREU), Land Use (LU), Terrestrial Acidification (TA), and Freshwater Eutrophication (FE). All agronomic data of the Gladbacherhof research farm, averaged over the years 2010–2017, were included. When not directly measured on the farm, ecoinvent data were included. Results and discussion Contrary to our hypothesis, the results suggest that a grassland-based low-input system has a higher environmental impact as compared to a high-input system for each of the five impact categories when using fat and protein-corrected milk (FPCM) as the functional unit. A 50% reduction in concentrates and exclusion of maize silage from the feed ration in the modelled low-input production system lead to a 20% drop in milk yield. To balance the energy content in low-input feeding ration, longer grazing period and higher amount of hay, alfalfa, and grass silage are required. This in turn results in higher emissions from enteric fermentation, manure management, and feed production and hence in higher environmental impact, particularly for GW, TA, and FE. Conclusions This study is one of the few that directly explores the environmental impact of feeding intensity in an organic milk production system. Nevertheless, there is a lack of research on consolidated emission factors for several greenhouse gas (GHG) sources in organic livestock and cropping systems to perform more robust carbon footprint calculations that comply with the Intergovernmental Panel on Climate Change (IPCC) Tier 3 GHG reporting guidelines. To generalize the results at the regional or national scale, direct comparisons with a larger number of organic farms representative of high-input and low-input intensities are still essential.

A comprehensive analysis of the effects of DGAT1 K232A polymorphism on milk production and fertility traits in Holstein Friesian and Jersey cows reared in Türkiye

Abstract. Research on the diacylglycerol acyltransferase 1 (DGAT1) K232A marker in cattle shows inconsistent results across regions, largely due to small sample sizes, limited genetic variation, and data restricted to few lactations, which complicates establishing a reliable genotype–phenotype correlation. This research aimed to determine the effect of the K232A polymorphism of the bovine DGAT1 gene on milk production and quality traits in dairy cattle. We used 1104 cattle, including 828 Holstein Friesian and 276 Jersey cows. The analysis utilized extensive data from six lactations of cows raised on four commercial dairy farms. We genotyped the population using the polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) technique and Sanger sequencing for verification. We then evaluated the 305 d and test-day milk yields as well as fat and protein yields and percentages. The number of inseminations per conception and calving ease were also assessed as reproduction indices. Genotype–phenotype associations were quantified using linear mixed models. The AA genotype was absent in Jersey cows, and the heterozygous genotype was predominant in both breeds. The K232A marker was significantly associated with test-day milk yield, fat, and protein content in Jersey cows. Further, it substantially affected the fat percentage of milk in Holstein Friesian cows (p&lt;0.001). We found that the KK genotype is highly desirable for milk quality and especially fat content. This comprehensive assessment demonstrated that the KK genotype of the DGAT1 K232A polymorphism significantly influenced fat and protein contents in dairy cattle.

Can Productive Aptitude and Age Affect Circulating Serotonin, Total Thyroid Hormones, and Cortisol Patterns in Cows?

Cattle productivity, whether in terms of meat yield or milk production, is intricately regulated by a multitude of factors. Among them, hormone concentrations play a significant role, reflecting the complex interplay between endocrine regulation and physiological processes that ultimately determine the efficiency and yield of production. High concentrations of 5-hydroxytriptamine (5-HT) are associated with a reduced metabolic load at the onset of lactation and a lower milk yield. Thyroid hormones (THs) and cortisol also affect several metabolic pathways, including carbohydrate, protein, and lipid metabolism. The aim of this study was to assess if milk or meat aptitudes and age influence circulating 5-HT, THs, and cortisol concentrations, investigating the possible interactions among these parameters. The research was performed on 46 healthy cows of three different breeds. Enzyme-linked immunosorbent assay (ELISA) methods were used to quantify circulating 5-HT and cortisol concentrations, and an immunochemiluminescent analyzer was used for THs. For parameters exhibiting non-normal distributions, an ANCOVA model using age, aptitude, and their interaction as fixed factors was applied. Significant lower T3 concentrations were recorded in dairy cows than in meat cows. Moreover, T4 significantly decreased with advancing age both in cows aimed at milk and meat production. Lastly, T4 was positively correlated with T3 and 5-HT in meat production-oriented cows.

Strong associations between the FGF-2 gene and productivity traits of Holstein-Friesian dairy cattle

Sustainability in dairy cattle farms depends on the efficiency of milk yield and reproductive traits. Thus, this study aimed to investigate the effect of the FGF-2/Csp6I gene and major environmental factors on these traits in Holstein-Friesian cattle. A total of 212 whole blood samples were collected from the Vena coccygea of cattle and the data obtained from these samples were used in all statistical analyses. Then, the restriction fragment length polymorphism (RFLP) method (determination of genotypes) was conducted and programs including PopGene (allele and genotype frequencies), Minitab (association analyses) and MTDFREML (variance components and genetic parameters) were used. Alleles A (0.4269) and G (0.5731) as well as genotypes AA (0.174), AG (0.505) and GG (0.321) were found, indicating that the population is polymorphic and in Hardy-Weinberg equilibrium (P > 0.05). The effect of the Csp6I polymorphism of FGF-2 gene on peak milk yield (PMY) (P < 0.01); lactation milk yield (LMY), milking time (MT), 305-day and 200-day lactation milk yield (LMY305 and LMY200), average daily milk yield (ADMY) (P < 0.05); 100-day lactation milk yield (LMY100), age of using in first breeding (AUFB) and number of inseminations per conception (NIPC) (P < 0.10) were significant. The heritability of milk yield traits and the correlation between direct and maternal heritability for reproductive traits were high. Furthermore, the breeding value of PMY was higher for the AA genotype (0.745 ± 0.292) than for the AG genotype (−0.268 ± 0.171) (P < 0.05). As a result, the A allele and AA genotype for the FGF-2/Csp6I gene had an increasing effect on milk yield without compromising reproductive performance in Holstein-Friesian dairy cattle.

Supplementation of isoacids to lactating dairy cows fed low or high forage diets: Effects on performance, digestibility, and milk fatty acid profile

Our objective was to determine the effects of isoacids (ISO) on the lactation performance, digestibility, and milk fatty acid (FA) profile of Holstein cows fed 2 forage NDF levels (FL). The study was 10-wk long (including 2-wk for covariate) utilizing a randomized complete block design. Sixty-four mid-lactating Holstein cows [662 ± 71 kg BW, 119 ± 51 DIM, 2 ± 0.9 parity] were blocked by parity, DIM, and prior milk yield (MY) for multiparous cows or genetic merit for primiparous cows, and randomly assigned to 1 of the 4 diets (n = 16). Diets were arranged as a 2 × 2 factorial, with 2 FL containing 21 (HF) and 17% forage NDF (LF) without (WIA) or with ISO supplementation (IA, 7.85 mmol/kg DM and 3.44 mmol/kg DM for isobutyrate and 2-methylbutyrate, respectively). Diets were balanced for similar NEL (1.58 Mcal/kg DM), CP (16.0%) and total NDF (27.2%). Feed intake and MY were recorded daily. Nutrient digestibility for each cow was determined using indigestible NDF as a marker, and fecal samples were collected at 8-time points (4 h intervals between samples). Individual cow milk samples composited over a 10-wk period were analyzed using gas chromatography for FA profile. The statistical model included FL, ISO, and FL × ISO as fixed effects and block as a random effect (lme4 in R). The ISO did not affect DMI (P = 0.13), while LF had greater DMI than HF diets (27.8 vs. 26.0 kg/d; P < 0.01). However, ISO increased MY (34.7 vs. 37.2 kg/d; P < 0.01) and ECM (41.9 vs. 39.0 kg/d; P < 0.01) by 7% in HF but not in the LF diet, suggesting FL × ISO interaction (P = 0.04). Interestingly, ISO increased ADG (0.4 kg/d) but decreased MUN by 9% only in LF diet as indicated by FL × ISO interaction (P < 0.01). Additionally, ISO increased DM, OM, NDF, and CP digestibility by 10-24% in HF (P < 0.01), but not in LF (FL × ISO; P > 0.05). As expected, ISO increased milk odd chain FA profiles in the IA groups irrespective of FL, e.g., the IA had greater C15:0 (1.87 vs. 1.54 g/100g FA; P = 0.03) and a tendency to be greater C17:0 levels (0.86 vs. 0.76 g/100g FA; P = 0.05) compared with WIA groups. Overall, ISO improved MY and nutrient digestibility in the HF whereas it increased ADG and decreased MUN in LF diet. Additionally, ISO increased milk odd chain FA (C15:0 and C17:0) regardless of FL.

A genomic analysis of twinning rate and its relationship with other reproductive traits in Holstein-Friesian cattle

Twin birth in dairy cattle is generally unfavorably associated with reproductive performance and calf survival in dairy cows. Genetic selection to reduce twinning rate in dairy cattle may be desirable, provided there are no undesirable correlated responses in other traits. The current study was undertaken to characterize the genomic architecture of twinning rate in the Irish Holstein-Friesian population, and to quantify the genetic relationship of twinning with other reproductive traits and milk yield. Calving records from the years 1996 to 2022 were used together with pedigree information to generate breeding value estimates for twinning rate. Genome-wide association analyses of twinning rate, calving interval, cow survival and age at first calving were conducted using de-regressed breeding values estimates for 2,656 Holstein-Friesian sires. Full genome sequence data imputed from approximately 50,000 single nucleotide polymorphisms were available for all sires. The heritability of twinning rate was 0.0118 ± 0.0010. Twinning rate was very weakly genetically correlated with both milk yield (0.13) and the reproductive traits (-0.26 to 0.14). Genomic analyses detected an association with twinning rate at 31.1 Mb on BTA11 in close proximity to genes for follicle-stimulating hormone receptor and luteinizing hormone-chorionic gonadotropin receptor, supporting previous studies. The most significant SNP in this region was not associated with milk yield, indicating the potential for selection to reduce twinning rate without detrimentally affecting milk yield. Novel SNP associations with age at first calving on BTA27 and from a meta-analysis of calving interval and age at first calving on BTA29 were also identified and are candidates for future validation and study.

Exploring Longitudinal Associations between Farmer Health and Wellbeing, and Dairy Herd Subclinical Mastitis Prevalence and Productivity: The HUNT Study, Norway

The health and wellbeing of farmers is one aspect of the sustainability of agriculture, as is the health and productivity of livestock. Previous research suggests a possible association between the 2, but the complexity of the relationships between farmers and their livestock can hamper research efforts. This observational study utilizes high quality existing survey and register data from a cohort of Norwegian dairy enterprises to explore possible longitudinal associations between farmer health and wellbeing (general health, chronic disease or condition, chronic pain, anxiety or depression symptoms, or poor life satisfaction) and changes in dairy herd udder health (estimated by the proportion of milk tests with a high somatic cell count (SCC%)) or milk yield (kilograms per cow-year equivalent). We found evidence of a general trend toward increased SCC% with poor farmer health or wellbeing. If the farmer had poor self-reported general health, the odds ratio (OR) for a one-year increase in SCC% at the enterprise was 1.51 (95% CI: 0.76,2.99, OR 1.80 (0.71, 4.51) after adjustment for possible effect modifiers) compared with those with good health, and for poor life satisfaction the OR was 1.50 (0.71,3.15) (2.61 (0.92,7.39) after adjustment). We also find evidence that enterprises where a farmer was experiencing poor health or wellbeing tended to have lower odds of a decrease in milk yield than other enterprises. The OR for a one-year decrease in milk yield with any chronic disease or condition was 0.42 (0.24,0.76), and with symptoms of anxiety or depression the OR was 0.56 (0.23,1.34). Potential confounders and effect modifiers are discussed and explored. These results suggest that further longitudinal research to unravel the relationships between farmer health and wellbeing, and livestock health and productivity is needed.

Isoacid supplementation influences feed sorting, chewing behaviors, and enteric methane emissions differentially in mid-lactation dairy cows depending on dietary forage level

Past studies have shown that isoacids (ISO) improve dairy cow performance, with effects varying based on dietary forage levels, leading us to speculate that ISO supplementation may also differentially affect enteric methane (CH4) emissions depending on dietary forage levels. Therefore, our primary objective was to examine the effects of ISO supplementation on enteric CH4 emissions in lactating dairy cows fed 2 forage NDF levels (FL), along with monitoring feed particle sorting and chewing behaviors to assess any potential interactions. Sixty-four (64) mid-lactation Holstein cows were utilized in a 10-wk long randomized complete block design trial. Parity, DIM, and prior milk yield (MY) for multiparous cows or genetic merit for primiparous cows were used as blocking factors. Cows were randomly assigned to 1 of 4 diets (n = 16 per diet) with a 2 × 2 factorial arrangement of treatment combinations, including 2 FL, 17 (LF) and 21% forage NDF (HF), without or with ISO supplementation (7.85 mmol/kg DM for isobutyrate and 3.44 mmol/kg DM for 2-methylbutyrate, respectively). Enteric CH4 and chewing activity (rumination and eating time) were measured using the GreenFeed system and sensor-based ear tag system, respectively. The particle size of each diet and ort from individual cows was measured using the Penn State Particle Separator, and a sorting index was calculated. A sorting index of 100 indicates no sorting, while values above or below 100 indicate sorting for or against, respectively. Data were analyzed using a mixed model including FL, ISO, and FL × ISO as fixed effects and block as a random effect (lme4 in R). Our result shows that ISO increased sorting index for long particle in LF (96.1 vs. 109; P < 0.01) but decreased it in HF (100.8 vs. 92.5; P = 0.04). In contrast, ISO did not affect the physically effective particle sorting index (P = 0.51) or intake (P = 0.27) regardless of FL. In alignment with the long particle sorting index, ISO decreased eating and chewing time in the HF but increased them in the LF diet (P < 0.01). In contrast, rumination time was comparable between FL (P = 0.70) and ISO levels (P = 0.19). In the LF diet, ISO supplementation reduced daily CH4 production (g/d) by 9% and intensity (g/kg of MY) by 18% (P < 0.01). In the HF diet, ISO supplementation led to a 10% increase in daily CH4 (P < 0.01) but did not change CH4 intensity (P = 0.17; g/kg of MY) due to improved milk production. Overall, ISO altered feed sorting, feeding behaviors and enteric CH4 emissions depending on FL.

Effect of training method and dairy cow personality traits on adaptation to an automated milking system

Training dairy cows on the automated milking system (AMS) can improve their performance, however, the ideal training method and how their individual personality relates to training is unknown. The objectives of this study were to determine: 1) the effect of AMS training method on adaptation of primiparous cows to an AMS, 2) whether the personality of a cow affects their adaptation to the AMS, and 3) whether certain personality types adapt better based on the type of training they receive. Forty-eight primiparous Holstein dairy cows, who had not previously been milked by an AMS, were enrolled in the study at ∼85 DIM and were assessed for personality traits using a combined arena test comprised of 3 parts: a novel arena test, a novel object test, and a novel human test. Cows were allocated into 1 of 4 AMS training treatments (n = 12): control (CON; no training), environment exposure only (ENV), environment and AMS concentrate provision (PEL), and environment and mechanics exposure (MEC). Cows in the ENV, PEL, and MEC treatments were subjected to training 4 × /d for 4 d, and then cows from all 4 treatments were milked on the AMS in the evening of the 4th training d. Milking activity and production were recorded for the first 14 d on the AMS. PEL cows had fewer visits to the AMS, fewer milkings, and fewer voluntary milkings compared with CON cows across the 14 d. Cows on all experimental treatments had more fetching events than CON cows, while MEC and ENV treatment cows had a higher milk yield compared with those on the CON treatment. Principal component analysis of the behaviors recorded during the personality assessment revealed 2 factors interpreted as personality traits, "explore-active" and "bold." Across all cows, more "explore-active" cows had greater milk yield. Only the performance of ENV cows was associated with personality; ENV cows who scored low for "explore-active" differed from CON cows, through increased visits and voluntary milkings. Overall, the results demonstrate that providing concentrate on its own during AMS training may not be motivating enough to improve adaptation and performance. However, exposing cows to the mechanics (e.g., the robotic arm and sounds of the AMS) before first milking may improve milk yield. Finally, cow personality may influence the performance of cows trained using less complicated training methods, such as only exposing them to the environment of the AMS.

Genetic parameters for methane production, intensity, and yield predicted from milk mid-infrared spectra throughout lactation in Holstein dairy cows

Genetic selection to reduce methane (CH4) emissions is a promising solution for reducing the environmental impact of dairy cattle production. Before such a selection program can be implemented, however, it is necessary to have a better understanding of the genetic determinism of CH4 emissions and how this might influence other traits of interest. In this study, we performed a genetic analysis of 6 CH4 traits predicted from milk mid-infrared spectra. We predicted 4 CH4 traits in g/d (MeP, calculated using different prediction equations), one in g/kg of fat- and protein-corrected milk (MeI), and one in g/kg of dry matter intake (MeY). Using an external data set, we determined these prediction equations to be applicable in the range of 70 to 200 DIM. We then estimated genetic parameters in this DIM range using random regression models on a large data set of 829,025 spectra collected between January 2013 and February 2023 from 167,514 first- and second-parity Holstein cows. The 6 CH4 traits were found to be genetically stable throughout and across lactations, with average genetic correlations within a lactation ranging from 0.93 to 0.98, and those between lactations ranging from 0.92 to 0.98. All 6 CH4 traits were also found to be heritable, with average heritability ranging from 0.24 to 0.45. The average pairwise genetic correlations between the 6 CH4 traits ranged from -0.15 to 0.77, revealing that they are genetically distinct, including the 4 measurements of MeP. Of the 6 traits, 2 measures of MeP and MeI did not present antagonistic genetic correlations with milk yield, fat and protein contents, and SCS, and can probably be included in breeding goals with limited impact on other traits of interest.

Assessment of skeletal muscle dynamics and milk production across a 300-day lactation in multiparous dairy cattle

The objective of this study was to evaluate changes in longissimus dorsi muscle depth (LDD) across lactation (0 to 300 DIM) and identify the impact of low versus high muscle reserves immediately after parturition on body weight and body reserve changes as well as production variables across a 300-d lactation. Forty multiparous cows were classified as high muscle (HM; LDD > 5.0 cm; n = 18) or low muscle (LM; LDD ≤ 5.0 cm; n = 22) based on LDD measurements collected within 24 h of parturition. Body weights (BW) and ultrasound scans to assess LDD and back fat depth (BFD) were collected monthly from parturition until 300 DIM. Ultrasound scans captured and measured using available software. Blood samples were taken at 7, 150 and 300 DIM, and plasma was analyzed for markers of metabolic status by measuring insulin, nonesterified fatty acids (NEFA), creatinine, and 3-methylhistidine (3-MH). Milk yield was recorded daily and milk components were analyzed monthly. Data analysis was performed and the statistical models included the fixed effect of muscle group, time, their interaction, and the random effect of cow nested within muscle group with repeated measures using a first-order autoregressive covariance structure. Muscle group was not related with BW or BFD for any of the time points measured. Cows lost BW from 0 to 60 DIM and gained weight from 60 to 300 DIM. Similarly, BFD decreased between 0 to 90 DIM and increased BFD after 90 DIM until 300 DIM. A muscle group by time interaction was observed for LDD. The HM cows had more muscle at 0 DIM, indicative of treatment assignment (1.34 cm more), and 300 DIM (0.78 cm more) and tended to have more muscle at 60 DIM (0.66 cm more) compared with LM. After 240 DIM, both muscle groups began net accretion of muscle reserves until 300 DIM. No differences were observed for blood metabolites measured based on muscle group. However, there were significant time effects for creatinine, 3-MH, and NEFA concentrations, which reflected the observed changes in BFD and LDD measured in ultrasound scans. For statistical analysis of daily milk production, observations were grouped into 3 stages of lactation, early (0-60 DIM), mid (60-240 DIM), and late lactation (240-300 DIM). There was a muscle group by stage of lactation interaction, where in early and mid-lactation, HM cows produced, on average, 1.9 kg more milk/d; however, in late lactation, LM cows produced 1.8 kg more milk/d. Our results indicate that muscle reserves are depleted in early lactation, and accreted in late lactation, whereas BW and BFD started to increase by 90 DIM. Data also supports that cows with more extensive muscle depletion in early lactation had greater milk production, however, substantial muscle accretion in late lactation may result in reduced milk production.

Impact of Management and Nutrition on HSP70 Gene Expression in Heat-stressed Dairy Cows

Background: This research investigated the effects of management and nutrition strategies on dairy cows under heat stress. Objectives: We aimed to evaluate the effects of zinc mineral supplementation and mist spray, alone and in combination, on yield, milk production and composition, blood parameters and HSP70 gene expression in dairy cows. Methods: Sixteen Holstein lactating cows were used for our experiment in four treatment groups: Basal diet without heat stress alleviation methods (control), zinc supplementation in diet, basal diet and application of mist spray method and supplementation of zinc in basal diet with mist spray. We measured milk production and composition, blood parameters and HSP70 gene expression in all cows. Results: The results showed that the cows in the mist and zinc+mist treatments had significantly better performance and temperature-humidity index than the control group. The milk yield and its compounds were significantly affected by experimental treatments, with the best results seen in the treatment with both spray and zinc. The cows exposed to dry and lactation periods showed a significant increase in the concentration of blood biochemical factors and antioxidant indices in response to heat stress. HSP70 gene expression was significantly decreased in all treatments compared to the control. Conclusion: This experiment suggests that applying nutritional and management strategies can effectively mitigate the effects of heat stress on dairy cows. The study recommends using zinc supplementation and mist spray to alleviate heat stress effectively. Overall, this study highlights the importance of implementing management and nutrition strategies to improve the welfare and productivity of dairy cows under heat stress.