Decreased Milk Yield Research Articles

Milk productivity of cows of different ages under the conditions of the dairy complex «Ryzhovo»

When production of milk in industrial volumes it is necessary to monitor all processes aff ecting its quantity and quality: animal feeding, breeding, mode and method of milking, herd reproduction, labour organization in the dairy complex, creating favorable conditions for cows that correspond to physiological characteristics. The dairy industry continues to impose higher and higher demands on milk, so in addition to improving the milk productivity of cows, we must not forget about the quality of the product. The issues of milk yield of cows, fat and protein, yield of milk fat and protein, somatic cells in milk of cows of Black-and-White breed for a number of lactations in terms of the dairy complex “Ryzhovo” have been considered in the article. It has been noted be researches that in the 1st and 2nd lactations milk yield of animals was 10 621 and 10 553 kg, respectively. The highest productivity of the cows has reached in the 3rd and 4th lactations 11 365 and 11 655 kg, respectively, after which, in the 5th lactation there was a decrease in milk yield to 10 592 kg. When considering fat content for diff erent lactations, positive dynamics up to the 4th lactation inclusive has been revealed. Thus, the fat content in milk for the 1st lactation was 3,61 %, for 2nd – 3,68 %, for 3rd – 3,93 % and 4th – 4,00 %. In the 5th lactation fat content decreased to 3,78 %. It has been found when calculating the yield of milk fat in experimental cows for lactation that up to the 4th lactation inclusive the indicator increases: for the 1st lactation received 383 kg of milk fat, 2nd – 388 kg, 3rd – 447 kg, 4th – 466 kg, and for the 5th lactation, the decrease in the index to 400 kg. At the same time the yield of milk fat for the 5th lactation exceeds the 1st and 2nd. The protein content in the milk of cows of diff erent ages during the fi rst four lactations increases from 3,18 to 3,43 %. Then, in the 5th lactation there is the decrease in protein content to 3,35 %, however, this fi gure is second only to the highest the 4th lactation. It has been established that before the 3rd lactation the number of somatic cells in milk increases, then in the 4th lactation this indicator decreases (151,25 thousand/cm3 ) and in the 5th lactation reaches a maximum (242,27 thousand/cm3).

In vivo model to study the impact of genetic variation on clinical outcome of mastitis in uniparous dairy\xa0cows

BackgroundIn dairy herds, mastitis causes detrimental economic losses. Genetic selection offers a sustainable tool to select animals with reduced susceptibility towards postpartum diseases. Studying underlying mechanisms is important to assess the physiological processes that cause differences between selected haplotypes. Therefore, the objective of this study was to establish an in vivo infection model to study the impact of selecting for alternative paternal haplotypes in a particular genomic region on cattle chromosome 18 for mastitis susceptibility under defined conditions in uniparous dairy cows.ResultsAt the start of pathogen challenge, no significant differences between the favorable (Q) and unfavorable (q) haplotypes were detected. Intramammary infection (IMI) with Staphylococcus aureus 1027 (S. aureus, n = 24, 96 h) or Escherichia coli 1303 (E. coli, n = 12, 24 h) was successfully induced in all uniparous cows. This finding was confirmed by clinical signs of mastitis and repeated recovery of the respective pathogen from milk samples of challenged quarters in each animal. After S. aureus challenge, Q-uniparous cows showed lower somatic cell counts 24 h and 36 h after challenge (P < 0.05), lower bacterial shedding in milk 12 h after challenge (P < 0.01) and a minor decrease in total milk yield 12 h and 24 h after challenge (P < 0.01) compared to q-uniparous cows.ConclusionAn in vivo infection model to study the impact of genetic selection for mastitis susceptibility under defined conditions in uniparous dairy cows was successfully established and revealed significant differences between the two genetically selected haplotype groups. This result might explain their differences in susceptibility towards IMI. These clinical findings form the basis for further in-depth molecular analysis to clarify the underlying genetic mechanisms for mastitis resistance.

Effects of rumen-protected methionine on lactation performance and physiological variables during a heat stress challenge in lactating Holstein cows

Milk yield, content, and composition are altered by heat stress. Thirty-two multiparous, lactating Holstein cows [balanced by days in milk (mean ± standard deviation; 184 ± 59); body surface area (5.84 ± 0.34 m2)] were randomly assigned to 1 of 2 dietary treatments [total mixed ration with rumen-protected Met (RPM; Smartamine M; Adisseo Inc., Antony, France; 1.05 g of RPM/kg of dry matter intake) or total mixed ration without RPM (CON)], and within each dietary treatment group cows were randomly assigned to 1 of 2 environmental treatment groups in a split-plot crossover design. The study was divided into 2 periods with 2 phases per period. In phase 1 (9 d), all cows were in thermoneutral conditions and fed ad libitum. In phase 2 (9 d), group 1 (n = 16) was exposed to a heat stress challenge (HSC) using electric heat blankets. Group 2 (n = 16) remained in thermoneutral conditions but was pair-fed (PFTN) to HSC counterparts. After a 21-d washout period, the study was repeated (period 2) and the environmental treatments were inverted relative to treatments from phase 2 of period 1, whereas dietary treatments (RPM or CON) remained the same for each cow. Cows were milked 3× per day and samples were taken on d 1, 5, and 9 of each phase. Vaginal temperature was measured every 10 min, rectal temperature and skin temperature were measured 3× per day, and respiration rate and heart rate were recorded once per day. Cow activity was measured using an accelerometer. Paired difference values were calculated for each cow for each period based on the difference between phase 1 baseline means and phase 2 values for each variable. Cows in HSC had a greater increase in vaginal temperature and respiration rate (+0.2°C and +13.7 breaths/min, respectively) compared with cows in PFTN (0.0°C and -1.6 breaths/min, respectively). Cows in PFTN had a greater decrease in dry matter intake and milk yield (-3.9 and -2.6 kg/d, respectively) compared with cows in HSC (-3.2 and -0.9 kg/d, respectively). Cows in CON had a greater decrease in milk protein concentration for PFTN (-0.10 percentage units) and HSC (-0.06 percentage units) compared with cows in RPM for PFTN (0.00 percentage units) and HSC (-0.02 percentage units). Cows in CON for HSC had greater decrease in milk fat concentration compared with cows in RPM for HSC (-0.10 and +0.12 percentage units, respectively). In conclusion, HSC altered physiological and production parameters of cows. Additionally, RPM helped maintain milk protein and fat concentration during HSC, whereas dry matter intake, milk yield, and feed efficiencies were not affected by RPM.

ЭФФЕКТИВНОСТЬ «ХУФ ПРОТЕКТ» ПРИ ГРУППОВОЙ ОБРАБОТКИ КОПЫТЕЦ У КОРОВ

Diseases of the distal part of the extremities of cattle under the conditions of intensive system of cattle breeding is a widespread phenomenon. The high density of animals on large industrial farms is usually accompanied by such phenomena as result of limited movement, identical feeding, increased con-tacts of animals with mechanized objects, and more frequent stressful situations lead-ing to a decrease in natural resistance. As a result, the incidences of hoof diseases in cows are increasing and lead to significant economic losses due to decrease in milk yield, live weight, and premature culling of animals. This problem exists in many coun-tries of the world including the CIS countries. It is necessary to notice that one of the causes of the diseases of the fingers is the deformation of the hooves, which develops in the absence of regular orthopedic clearing. An important role to prevent the develop-ment of diseases of the hooves belongs to the organization of preventive measures at live-stock holdings. To increase the resistance of the hooves to diseases and for treatment pur-poses, foot baths with hypertonic solution of copper sulfate, formalin and other drugs are offered by the pharmaceutical industry. The bath for hoofs will have the expected impact only if the cow put all four limbs into the solution. It can be ensured in case the bath has at least 3.5 - 4.0 m in length and 0.7 - 0.8 m in width. Moreover, the height of the entrance should be about 20 cm - then additional fingers will be handled. Following the regulations of hooves disinfection leads to high health status of herd.

Development of the dairy industry in the region

The article considers the modern situation of the dairy industry in Russia and its regions. The domestic dairy industry is one of the leading branches of agricultural products processing. It gives such an important product for human nutrition as milk. In recent years, this industry is in a situation of stagnation. The situation of the dairy industry can be judged as a whole about the situation of agriculture in the region. In the Siberian region, as well as in the whole country, there was a decrease in the number of cattle, and as a consequence there was a decrease in milk yield. Recently, despite new technologies and increased livestock productivity, milk production has not been sufficient to meet the needs of the population. The way out of this situation is proposed measures of state support in the dairy industry at the regional level.

Effect of changes in milk yield and inter-calving period on profitability of commercial dairy farm

The present study was conducted for crossbred commercial dairy farms in India to study the effect of various reproductive parameters, viz. milk yield and intercalving period on their profitability. The base parameters were identified under the field conditions and a base model was prepared. The milk yield and inter-caving period under field conditions were about 15 litres per day and 14 months respectively. The result indicated that profitability ratios were more sensitive to worsening ICP than decrease in milk yield. An average farm of 100 animals would continue to be profitable even if average milk yield dropped from 15 to 12 liters/day, but would not sustain if ICP increased from 14 to 18 months, thus emphasising the need to focus R&amp;D and extension efforts on improving both, productive and reproductive traits of animals.

Technology to improve milk productivity of female camels of the Arvana breed and Kazakh bactrian

It is proved that milk yield in winter is characterized by a decrease in the absolute indicator of the average daily milk yield with a simultaneous increase in the mass fraction of fat in milk in camels, regardless of the breed and the zone of their breeding. On average, the milk yield in December - February for camels of Arvan breed was from 4.8 kg to 6.4 kg, with a mass fraction of fat in milk of 4.6 - 4.7%. In winter, the milk yield of the Kazakh Bactrian camels in comparison with the peers of the Arvana breed of the “bestorrangyla” plant type is 2.5 times lower. The female camels of the Kazakh Bactrian in the first and second months of the winter period did not experience a sharp decrease in milk yield and on average December 2.5 - 3.0 kg and January 2.3 - 2.8 kg. At the end of the winter period - in February it drops sharply and reaches the level of 1.6-2.1 kg. At the same time, the fat content of milk in the winter period is in the redistribution of 5.9 – 6.2%.

ИННОВАЦИОННЫЙ МЕТОД ЛЕЧЕНИЯ КОРОВ ПРИ МАСТИТЕ

In the modern world of agriculture, which is directly related to the breeding of cattle, aimed in particular at milk production, the problem associated with inflammation of the udder lobes, namely mastitis, has become widespread. To a large extent, the culling of cows occurs due to the inability to completely and completely cure this disease without damaging the productivity in the herd, as well as due to complications caused as a result of the transferred inflammation (atrophy, induration, fibrosis of the udder lobes). Mostly young animals with a high genetic potential for milk production suffer from this pathology. According to statistical data, namely, in 20%-30% of cases, subclinical mastitis enters the clinical phase with a pronounced symptomatic form of lesion of the udder lobes, which in the future can lead to their atrophy and other irreversible complications. The main symptomatic signs of the general condition of an animal with a pronounced clinical form of mastitis are: the apathetic state of the animal and refusal to feed due to an increase in the general body temperature, depending on the nature of the course and the form of the disease. When considering the same pathology of its symptoms, on the basis of local signs of the course, I single out a complex of symptoms that is observed in almost all forms of udder lesions: an increase in the local temperature of the mammary gland, hyperemia and swelling of the affected lobes of the udder, or the entire organ with generalization of inflammation in all lobes, in a clinical study , namely, on palpation in the animal, a painful reaction is observed, a change in the consistency of the udder and nipples, as well as an increase and compaction of the supra-lymph nodes. When considering the economic damage on farms associated with the presence of mastitis in productive animals, there is not only a general decrease in the overall productivity of the dairy herd, which is associated with the loss of milk at production, but also with a decrease in milk yield in individual animals associated with dysfunction of the mammary gland due to the presence of impurities and inhibiting substances throughout the treatment and sometime after it. As a percentage of milk yield per lactation in cows that have undergone subclinical mastitis, there is a decrease in milk production by 10-15%, while a deterioration in the quality characteristics of products is also observed. Early diagnosis, timely treatment and prevention of subclinical mastitis is an urgent task. The main purpose of this article is the need to consider an increase in the effectiveness in the treatment of mastitis, according to the method of using the means of complex etiotropic therapy, by means of which the absence of inhibitory substances in milk will be ensured and will allow the sale of these products in the future without restrictions, as well as an increase in the economic well-being of farms, including treatment costs.

Relationship between sire predicted transmitting ability for daughter pregnancy rate and daughter's reproductive performance and milk production in Japanese dairy herds.

Modern genetic improvement in dairy cattle is directed towards improvement of fertility; however, reproduction traits generally exhibit a genetic antagonism with milk yield. Herein, we aimed to clarify the effects of sire predicted transmitting ability (PTA) for daughter pregnancy rate (DPR) on the reproductive performance and milk yield of daughters in Japanese dairy herds. We conducted a retrospective cohort study on four dairy herds in eastern Hokkaido, Japan, using 1,612 records from 1,018 cows with first, second, or third calvings between March 2015 and September 2018. First, we classified sires into three groups based on the tertile value of their DPR estimate: ≤ −2.2 (low), −2.1 to −0.4 (intermediate), and ≥ −0.3 (high). Subsequently, we compared the sire PTA estimates, reproductive performance, and milk production among DPR groups for each parity of the daughters. In the first and second parity, the hazard of pregnancy by 200 days postpartum was highest in cows from the high-DPR group (P < 0.05); in the third parity, it was unaffected by DPR group. Although sire PTA for milk production in cows from the low-DPR group was highest, actual milk production was unaffected by DPR group regardless of parity. Our findings demonstrate that using sires with PTA for high fertility can enable farmers to improve reproductive performance without decreasing milk yield in Japanese dairy herds. However, it should be noted that sires with PTA for high fertility are at risk for reducing the genetic merit for milk production.

The effects of dietary supplementation with 3-nitrooxypropanol on enteric methane emissions, rumen fermentation, and production performance in ruminants: a meta-analysis

The aim of this study was to investigate the effects of 3-nitrooxypropanol (NOP) on gas production, rumen fermentation, and animal performances depending on animal type using a meta-analysis approach. A database consisted of data from 14 studies, 18 experiments and 55 treatments. The supplementation of NOP linearly decreased methane (CH4) emissions [g/kg dry matter intake (DMI)] regardless of animal type and length of experimental period (beef, p < 0.0001, R2 = 0.797; dairy, p = 0.0003, R2 = 0.916; and long term, p < 0.0001, R2 = 0.910). The total volatile fatty acids (VFA) concentration and the proportion of acetate, based on beef cattle database, were significantly decreased with increasing NOP supplementation (p = 0.0015, R2 = 0.804 and p = 0.0003, R2 = 0.918), whereas other individual VFAs was increased. Based on the dairy database, increasing levels of NOP supplementation linearly decreased proportion of acetate (p = 0.0284, R2 = 0.769) and increased that of valerate (p = 0.0340, R2 = 0.522), regardless of significant change on other individual VFAs. In animal performances, the DMI, from beef cattle database, tended to decrease when the levels of NOP supplementation increased (p = 0.0574, R2 = 0.170), whereas there was no significant change on DMI from dairy cattle database. The NOP supplementation tended to decrease milk yield (p = 0.0606, R2 = 0.381) and increase milk fat and milk protein (p = 0.0861, R2 = 0.321, p = 0.0838, R2 = 0.322). NOP is a viable candidate as a feed additive because of its CH4 mitigation effects, regardless of animal type and experiment period, without adverse effects on animal performances.

Molecular Epidemiological and Serological Studies of Bovine Leukemia Virus in Taiwan Dairy Cattle.

Bovine leukemia virus (BLV) infection results in a decrease in milk yield and quality, a compromise in immunity, and shortening in the longevity of cows. The current status of BLV infection of dairy cattle in Taiwan remains unclear. To evaluate BLV infection, anti-BLV gp51 antibody and proviral DNA were detected. Surprisingly, the seroprevalence of BLV at the animal and herd level was as high as 81.8% (540/660 cattle) and 99.1% (109/110 herds), respectively. Among 152 blood samples analyzed, 132 (86.8%) were detected as positive for BLV-proviral DNA. When the complete blood count (CBC) was taken into account, the white blood cell (WBC) number appears to be the factor with the highest predicted potential for BLV infection. Moreover, based on receiver operating characteristic (ROC) curve analysis, the sensitivity and specificity are 72.0 and 75.0%, respectively, when the cut-off value of the WBC was set at 10.215 K/μL. Despite the co-circulation of genotype 1 and 3 in Taiwan, genotype 1 was much more prevalent (29/30). Taken together, due to the high prevalence of BLV, the identification of risk factors for interrupting the routes of transmission of BLV are critical for the control and prevention of further BLV infection.

Investigation of myostatin and calpain 3 gene polymorphisms and their association with milk-production traits in Sfakia sheep

Context Genetic selection based on genetic markers for economically important traits in Sfakia sheep. Aims The aim of the present study was to investigate variation in the ovine myostatin gene (MSTN) and calpain 3 gene (CAPN3), and their association with milk-production traits. Methods Records for milk yield, milk fat content, protein content, lactose content, and non-fat solid content, pH and somatic-cell score (log), were obtained from 376 Sfakia ewes. Polymerase chain reaction–single-strand conformational polymorphism (PCR–SSCP) analyses were used to detect variation in intron 1 of MSTN and exon 10 of CAPN3. General linear models were then used to test for associations between the variation in MSTN and CAPN3, and milk-production traits. Key results The SSCP banding patterns for MSTN showed four variants (A1, A2, A3 and A4), which contained nine nucleotide sequence differences. Four SSCP banding patterns (C1, C2, C3 and C4) were observed for CAPN3 and these contained eight nucleotide-sequence differences. The MSTN variation was associated (P &amp;lt; 0.05) with variation in milk yield and non-fat milk solid content. Variation in CAPN3 was associated with milk yield (P &amp;lt; 0.001), fat content (P &amp;lt; 0.05) and lactose content (P &amp;lt; 0.05). Association analyses between the presence/absence of MSTN and CAPN3 variants and milk-production traits showed that a variant of MSTN that had previously between associated with muscle hypertrophy was associated with decreased milk yield (P &amp;lt; 0.05) and a lower non-fat milk solid content (P &amp;lt; 0.01). A CAPN3 variant that had previously been associated with increased sheep-carcass loin lean-meat yield was associated with a decreased milk yield (P &amp;lt; 0.01) and a decreased milk fat content (P &amp;lt; 0.05). Conclusions Our results have provided an insight into the effects of variation in ovine MSTN and CAPN3 on milk-production traits in sheep. Implications To preserve the dual-purpose characteristics of Sfakia sheep, breeding goals should take into account the possible antagonism between meat and milk traits.

Case-control study on factors associated with a decreased milk yield and a depressed health status of dairy herds in northern Germany

BackgroundIn the past years, it became apparent that health status and performance differ considerably within dairy farms in Northern Germany. In order to obtain clues with respect to possible causes of these differences, a case-control study was performed. Case farms, which showed signs of health and performance problems, and control farms, which had none of these signs, were compared. Risk factors from different areas such as health management, housing, hygiene and nutrition were investigated as these are known to be highly influential. The aim of this study was to identify major factors within these areas that have the strongest association with health and performance problems of dairy herds in Northern Germany.ResultsIn the final model, a lower energy density in the roughage fraction of the diet, more pens with dirty lying areas and a low ratio of cows per watering spaces were associated with a higher risk for herd health problems. Moreover, case farms were affected by infections with intestinal parasites, lungworms, liver flukes and Johne’s Disease numerically more often than control farms. Case farms more often had pens with raised cubicles compared to the deep bedded stalls or straw yards found in control farms. In general, the hygiene of the floors and beddings was worse in case farms. Concerning nutrition, the microbiological and sensory quality of the provided silages was often insufficient, even in control farms. Less roughage was provided to early lactating cows and the feed was pushed to the feeding fence less frequently in case farms than in control farms.ConclusionsThe results show that milk yield and health status were associated with various factors from different areas stressing the importance of all aspects of management for good animal health and performance. Moreover, this study confirmed well-known risk factors for health problems and performance losses. These should better be taken heed of in herd health management.

Enhanced Fluorescence of N-Acetyl-β-D-Glucosaminidase Activity by ZnO Quantum Dots for Early Stage Mastitis Evaluation.

Recurrent mastitis events are the major cause of annual revenue losses in the dairy sector resulting in decreased milk yield, escalading treatment costs and increased health risk of the entire herd. Upon udder inflammation, several biomarkers are proportionally secreted to its severity onto the blood circulation and consequently into milk (upon breached blood-milk barrier). N-acetyl-β-D-glucosaminidase activity is widely used mastitis indicator in milk, offering simple means of differentiation between healthy quarters from those with subclinical or clinical severity. Herein, we demonstrate fluorescence signal amplification concept for sensitive clinical status discrimination. Tetraethyl orthosilicate coated zinc oxide quantum dots were employed within the conventional N-acetyl-β-D-glucosaminidase activity assay. Under the experimental conditions, a profound non-radiative energy transfer occurred between quantum nanomaterials onto enzymatic fluorescent products resulting in intensified emission of the latter, over 11-folds, in comparison to nanoparticle-free assay. Overall, the fluorescence intensities were proportionally related to zinc oxide quantum dots surface coverage and concentration, SCC values and influenced by the causing bacteria (i.e., Streptococcus dysgalactiae and Coagulase-negative Staphylococci). Finally, the presented proof-of-concept offers an efficient, simple, cost-effective fluorescence signal amplification for early stage mastitis identification, offering means to diagnose the severity of the associated diseases and hence deducing on animals' clinical status.

The Effect of Breeding Region on Differences in Persistency of Heat Stress Effect in First Parity Simmentals

In order to determine the effect of breeding region on differences in persistency of heat stress effect in first parity Simmentals test-day records provided by the Croatian Agricultural Agency were analysed. Only cows with detected statistically significant decrease in daily milk yield at set temperature-humidity index (THI) threshold value (65, 70 and 75) were included in the further analyses. The persistency of heat stress effect regarding the daily milk traits was determined as a drop in the subsequent milk recordings (1st and 2nd). The research results indicate significant difference in animals’ response to heat stress effect due to breeding region and individual’s susceptibility to heat stress. The most pronounced and persistent negative effect of heat stress was determined in cows reared in Eastern region. Also, the negative effect of heat stress was more pronounced and more persistent in Simmentals that were heat stressed at the lower THI threshold values (cows that are more susceptible to heat stress).

Inbreeding depression due to recent and ancient inbreeding in Dutch Holstein\u2013Friesian dairy cattle

BackgroundInbreeding decreases animal performance (inbreeding depression), but not all inbreeding is expected to be equally harmful. Recent inbreeding is expected to be more harmful than ancient inbreeding, because selection decreases the frequency of deleterious alleles over time. Selection efficiency is increased by inbreeding, a process called purging. Our objective was to investigate effects of recent and ancient inbreeding on yield, fertility and udder health traits in Dutch Holstein–Friesian cows.MethodsIn total, 38,792 first-parity cows were included. Pedigree inbreeding (F_{PED}) was computed and 75 k genotype data were used to compute genomic inbreeding, among others based on regions of homozygosity (ROH) in the genome (F_{ROH}).ResultsInbreeding depression was observed, e.g. a 1% increase in F_{ROH} was associated with a 36.3 kg (SE = 2.4) decrease in 305-day milk yield, a 0.48 day (SE = 0.15) increase in calving interval and a 0.86 unit (SE = 0.28) increase in somatic cell score for day 150 through to 400. These effects equalled − 0.45, 0.12 and 0.05% of the trait means, respectively. When F_{PED} was split into generation-based components, inbreeding on recent generations was more harmful than inbreeding on more distant generations for yield traits. When F_{PED} was split into new and ancestral components, based on whether alleles were identical-by-descent for the first time or not, new inbreeding was more harmful than ancestral inbreeding, especially for yield traits. For example, a 1% increase in new inbreeding was associated with a 2.42 kg (SE = 0.41) decrease in 305-day fat yield, compared to a 0.03 kg (SE = 0.71) increase for ancestral inbreeding. There were no clear differences between effects of long ROH (recent inbreeding) and short ROH (ancient inbreeding).ConclusionsInbreeding depression was observed for yield, fertility and udder health traits. For yield traits and based on pedigree, inbreeding on recent generations was more harmful than inbreeding on distant generations and there was evidence of purging. Across all traits, long and short ROH contributed to inbreeding depression. In future work, inbreeding depression and purging should be assessed in more detail at the genomic level, using higher density information and genomic time series.

Influence of various selection options on economic and useful signs of the red-and-white cattle

It has been established that the spontaneous use of closely related mating in utility herds in most cases does not give the desired results. The use of close and close inbreeding leads to a decrease in milk yield, live weight of cows and prolongs the service period. When breeding record-keeping cows, moderate and distant inbreeding makes it possible to get along with crosses of large, highly productive lines, distinguished by good health and good reproductive abilities of animals. The degree of heritability of breeding traits with homogeneous selection turned out to be higher than with heterogeneous selection. An increase in the degree of heritability with homogeneous selection can be explained by a clearer manifestation of the additive effect of genetic factors.

Prevalence of ‘Mycoplasma wenyonii’ and Candidatus Mycoplasma haemobos in Wisconsin and Michigan dairy cattle herds

Mycoplasma wenyonii (fmr. Eperythrozoon wenyonii) is a hemotrophic, epicellular bacterial parasite of cattle and is associated with clinical disorders including hemolytic anemia, decreased milk yield, and scrotal, teat, and hindlimb edema. M. wenyonii and related organism, Candidatus Mycoplasma haemobos have been found in apparently healthy cattle in other countries, but little is known about their prevalence in the U.S. The objective of this prospective, cross-sectional study was to determine herd-level prevalence of M. wenyonii and C.M. haemobos in dairy cattle located in WI and MI.

Association between hyperketonemia in early lactation and culling and hyperketonemia in subsequent lactation in Holstein dairy cows

Hyperketonemia (HYK) is an early lactation metabolic disease frequently observed in high-producing dairy cattle and it has been associated with suboptimal reproductive performance, decreased milk yield, increase occurrence of other diseases, and increase in culling. The majority of the reports so far focused on the association of HYK and these outcomes during early lactation, however, the effect of HYK in the whole lactation and following lactations has not been as extensively characterized. Therefore, our primary objective was to evaluate the association of HYK occurring during the first 10 days after calving and culling in Holstein dairy cows throughout an entire lactation. Our secondary objective was to determine the likelihood of the occurrence of HYK in subsequent lactations in Holstein dairy cows.

Effect of bi-modal milk letdown on milk production

The dairy industry is relying more on hired labor to milk cows and many dairy operations are increasing pressure on employees to maintain high levels of milking parlor throughput. This management emphasis negatively impacts milking protocols that are aligned with milk quality. Parlor efficiency is often defined in terms of cows milked per hour. However, we need to consider milking efficiency to include milk quality, milk flow, and employee performance (Moore-Foster et al., 2019; Erskine et al., 2019). The purpose of this study was to determine the impact of poor pre-milking preparation (as evidenced by bi-modal milk letdown) on subsequent milk production.&#x0D; Erskine, RJ, B Norby, LM Neuder, et al. 2019. Decreased milk yield is associated with delayed milk ejection. J. Dairy Sci. (in press)&#x0D; Moore-Foster R, B Norby, RL Schewe, et al. 2019. Herd-level variables associated with delayed milk ejection in Michigan dairy herds. J. Dairy Sci. 102:696-705.