Level Of Milk Yield Research Articles

Intramammary antimicrobial treatment of subclinical mastitis and cow performance later in lactation

The aim of this study was to evaluate long-term therapeutic effects of antimicrobial treatment of recently acquired subclinical mastitis (RASCM) during lactation. Quarter-level clinical mastitis (CM) follow-up, composite somatic cell counts (SCC), and cow-level milk yield later in lactation were evaluated using follow-up data from 2 previously published linked randomized field trials. The first trial randomly assigned antimicrobial treatment with any intramammary product or negative control to culture-positive quarters of cows having a first elevated composite SCC after 2 consecutive low composite SCC measurements. Untreated cows that had a second elevated composite SCC at the next measurement and were staphylococci-positive (i.e., Staphylococcus aureus or non-aureus staphylococci) were randomly assigned to treatment or control. Quarter-level CM cases were reported by the participating herd personnel, and milk yield and composite SCC data were obtained from the regular test-day recording. Frailty survival models were used to evaluate the long-term therapeutic effects of antimicrobial treatment of RASCM on quarter-level CM follow-up. Mixed linear regression models were applied to quantify the effect on milk yield and composite SCC. Data of 638 quarters from 486 cows in 38 herds were available for statistical analyses, of which 229 quarters of 175 cows received antimicrobial treatment for RASCM. Antimicrobial treatment culminated in reduced composite SCC levels later in lactation but did not result in different milk yield levels or CM follow-up compared with control cows. Antimicrobial treatment of cows with RASCM should therefore only be considered in exceptional situations given the current focus on antimicrobial usage reduction in animal husbandry.

Sanitary aspects of the herd and milk quality in family farming properties in the Western Amazon

The aim of this study was to analyze 100 dairy farms under family farming regime from the mesoregion of the Acre Valley in the Western Amazon, regarding the sanitary and milk quality aspects, considering different levels of milk yield. The data were collected from March to June 2016, from a semi-structured form, containing 301 questions, through on-site observation, as well as the answers obtained with the owners; and recorded in SPSS® spreadsheets. The descriptive statistics was adopted and, with the aid of the cluster analysis methodology, the cowmen were divided into two clusters with different characteristics in terms of productivity (higher and lower). Some relevant differences among the properties were identified: those belonging to the higher productivity cluster had higher family income and showed greater use of technologies, such as expansion tank and milking machine. In addition, they showed higher vaccination rates against clostridial diseases and rabies. Regarding milk quality, there was higher pre-dipping indices. Milk analyses (somatic cell count, total bacteria count, temperature, protein, fat, bacterial inhibitors, reductase and milk solids-not-fat) were performed on any property. It was concluded that actions are needed to improve productivity and aspects related to milk quality.

Response profiles of dairy cows to a single 24-h milking interval in relation with milk proteolysis, udder expansion and immune traits

An extended milking interval of 24 h (24-h milking interval (24h-MI)) constitutes the acute phase of cow adaptation to once-daily milking (ODM). A recent trial including 724 24h-MI challenges demonstrated that milk yield responses to this acute phase of ODM are highly variable (from+22% to −52% of milk yield when switching to the 24h-MI, mean=−25.3%) and that factors such as stage of lactation parity and milk yield level influenced cows’ responses but did not account for all individual variability. Additional traits related to physiological, immune and behavioural adaptation were measured on a subset (96 observations) of this data set. This study aimed to determine (1) the relationship of these traits with cows’ milk yield responses, (2) their ability – combined with previously identified traits – to help predict milk yield responses to 24h-MI (adaptive profiles). The 24h-MI challenge consisted of three successive periods: one control week of twice-daily milking (cTDM), one single day of 24h-MI and then 13 days of TDM (pTDM). Milk yield responses to the 24h-MI (corrected for effects of stage of lactation, parity, milk yield level and milk yield) were related to physiological traits measured during cTDM (milk flow rate, presence or absence of interleukin-8) and to their changes during the 24h-MI (absolute increase in milk flow rate and relative udder distension). Analysis of associations between milk yield responses, stage of lactation, parity, milk yield level, proteolysis, udder expansion and immune traits found three adaptive cow profile clusters. Cows in cluster 1 had a less compliant udder than cows in cluster 2, and they lost more milk during the 24h-MI than cluster-2 and cluster-3 cows. After resuming twice daily-milking (TDM), cluster-2 cows fully recovered the milk they had lost during the 24h-MI. On the opposite, cluster-3 cows did not recover the milk they lost, likely due to udder inflammation during cTDM, as suggested by elevated concentrations of interleukin-8 in their milk. These results combining new traits with stage of lactation, parity and milk yield level constitute a first step towards predicting individual cow responses to a 24h-MI.

PERSPECTIVES FOR DEVELOPMENT OF UKRAINE DAIRY CATTLE BREEDING UNDER THE CONDITIONS OF AN ORGANIC PRODUCTION

PERSPECTIVES FOR DEVELOPMENT OF UKRAINE DAIRY CATTLE BREEDING UNDER THE CONDITIONS OF AN ORGANIC PRODUCTION

Carbon Footprint of Milk from Pasture-Based Dairy Farms in Azores, Portugal

The dairy sector is a major contributor to greenhouse gas emissions. Pasture-based dairy production is sometimes credited as environmentally friendlier but is less studied than more intensive production systems. Here we characterize and calculate the carbon footprint (CF), using life cycle assessment, of the “Vacas Felizes” pasture-based milk production system, in the Azores archipelago. Impacts were determined for multiple functional units: mass, energy and nutritional content, farm, area and animal. We performed multivariate analysis to assess the contribution of production parameters to the CF. Finally, we performed a literature review to compare these results with other production systems. Results show that emissions from enteric fermentation, concentrated feed production and (organic and mineral) fertilizer application are the three main sources of impact. Milk yield is a key production feature for the determination of emissions. The average CF is 0.83 kg CO2/kg raw milk. At each milk yield level, the farms are approximately homogeneous. Compared with other studies, “Vacas Felizes” milk has a lower CF than 80 (out of 84) published CFs and on average it is approximately 32% lower.

Diversity of dairy goat lactation curves in France

A high level of production at the peak of lactation may be associated with animal health disorders, high feeding costs, and reduced milk supply throughout the year. The objective of this study was to typologize the lactation curves in French dairy goats and analyze the influence of environmental and genetic factors on these curves. The data set consisted of 2,231,720 monthly test-day records of 213,534 French Saanen and Alpine goats recorded between September 2008 and June 2012. First, principal component analysis classified the shape of the lactation curves into 3 principal components: the first component accounted for milk yield level throughout lactation, the second component accounted for lactation persistency, and the third component accounted for milk yield in mid-lactation. Then, from the principal component scores, the lactations were clustered into 5 different groups. Most lactations had a similar shape to the mean curve, except 30% of the lactations that fell into 3 clusters that had a high production level at the peak and then a different persistency according to cluster. Estimated breeding value for milk yield and home region of breeding were the factors most related to lactation production level. Month of kidding, breed, and gestation stage had the biggest effect on persistency. Month of kidding was the factor most strongly linked to mid-lactation production. A herd effect was observed on all 3 principal components.

Electrical conductivity of milk as related to daily milk yield of udder quarters in automatically milked cows

The aim of the study was to determine the frequency of udders with specific levels of milk electrical conductivity and milk yield in primiparous and multiparous cows. Relationships between the health and milk yield of individual udder quarters in the primiparous and multiparous cows were also analysed. The left and right front quarters constituted, respectively, 67.39 and 67.90% of the quarters from which milk with electrical conductivity ≤5.50 mS/ cm was drawn. In the conductivity class >7.00 mS/cm, the right and left rear quarters showed the highest proportions (9.59 and 7.13%, respectively). Individual udder quarters from the cows most often produced either less than 7.00 kg or more than 10.00 kg milk per day. These differences concerned the front and rear udders. In the first two classes of milk electrical conductivity, the frequency of individual udder quarters in the primiparous and multiparous cows was similar. For milk with the lowest electrical conductivity, the values ranged from 50.38% (front left) to 52.62% (rear left) in primiparous cows, and from 47.38% (rear left) to 49.62% (front left) in multiparous cows. As the health of the mammary gland deteriorated, daily milk production of all its quarters was observed to decrease. A more marked reaction to this condition was observed in the front quarters, the yield of which decreased by 3.40 kg (left) and 3.02 kg (right). The rear left quarters decreased their yield by 2.85 kg/day, and the rear right ones by 2.18 kg/day. Higher production levels in all mammary quarters and in every milk electrical conductivity class were noted in the multiparous cows. The increasing milk electrical conductivity was paralleled by a lower daily milk yield of the udder quarters in both primiparous and multiparous cows. For the front left and right quarters, this decrease was 2.77 and 2.41 kg in the youngest cows, and 4.27 and 4.26 kg in the older cows. The decrease in milk production from the rear left quarters was 2.67 kg/day in primiparous and 3.76 kg/day in multiparous cows; the respective values for the rear right quarters were 2.01 and 3.86 kg milk/day.

Ameliorative Effect of Infused Watercress on Rat Galactopoiesis following Maternal Separation

Galactopoiesis is the maintenance of milk production. The process that regulated primarily by prolactin hormone. The research was conducted to evaluate galactopoiesis activity by measuring prolactin level and milk production continuity of lactating rats after oral administration of infused watercress. Twenty lactating rats were randomly divided into five groups (two control groups and three variations of infused watercress dose groups). Serum prolactin was measured using enzyme-linked immunosorbent assay. Milk yield was measured using indirect milk measurement method by Sampson and Jansen. Milk protein level was measured using Kjedahl method. The treatment of infused watercress (10 g/kg body weight), started from postnatal day 3 until 12, indicated ameliorative effect on rat galactopoiesis by increasing milk yield and prolactin levels, but not milk total protein.

Application of pancreatic phospholipase A2 for treatment of bovine mastitis.

Recent findings have indicated that secreted phospholipases A2 (sPLA2s) have anti-inflammatory functions, including relief of symptoms in a mouse model of mastitis. This prompted us to investigate the therapeutic application of sPLA2, PLA2G1B, for bovine mastitis. Initial testing of PLA2G1B's effect on bovine mammary epithelial cell (bMEC) line PS revealed no changes in cell viability or cytokine-secretion pattern. However, when cells were first treated with lipopolysaccharide endotoxin (LPS) or live bacteria (Escherichia coli or Staphylococcus aureus), incubation with PLA2G1B significantly improved cell viability, suggesting involvement of sPLA2s in protecting membranes from lipid-peroxidation damage, rather than a bactericidal action. When PLA2G1B was applied simultaneously with LPS, a significant short-term reduction in interleukin-8 secretion was observed compared with bMECs treated only with LPS, supporting previous reports that PLA2G1B affects interleukin-8 signaling in similar cells. Following the favorable outcome of the in vitro experiments, we tested PLA2G1B in vivo by mammary infusion into infected glands. In one of a small sample (n = 4) of lactating cows chronically infected with Streptococcus dysgalactiae, a single PLA2G1B treatment completely cleared inflammation and bacteria, demonstrating its potential to cure subclinical mastitis. PLA2G1B treatment did not affect coagulase-negative staphylococci infection. These types of mastitis may involve formation of a resistant biofilm, and its elimination may relate to sPLA2s' characteristic ability to aggregate with cellular debris, facilitating their internalization by macrophages. In a bovine model of clinical mastitis based on introduction of E. coli via the streak canal, a single mammary infusion of PLA2G1B led to faster recovery to pre-infection milk-yield levels and decrease of somatic cell counts. In this case, all of sPLA2s' modes of resolving inflammation may apply, including competitive binding of the sPLA2s’ receptor, the inactivation of which confers resistance to endotoxic shock. Hence, this study strongly supports further research into PLA2G1B as a cure for bovine mastitis.

LACTATION PERFORMANCE OF HIGH-YIELD FIRST-CALF COWS

The results are given from the studies on lactation performance of fi rst-calf cows belonging to different sire lines. The research was conducted in 2017 in Novosibirsk region into 42 fi rst-calf cows of black-andwhite Holstein breed, belonging to the sire lines of Wis Ideal and Refl ection Sovereign, during 150 days of lactation. The pipe-line milking of cows was performed by DeLaval milking machines with adjustable pumping. Monitoring of lactation performance, intensity of milk fl ow, content of fat and protein was carried out monthly. The largest daily milk yield of cows of both lines was noted in the second month of lactation. In the fourth and fi fth months of lactation an average daily milk yield of cows belonging to the Refl ection Sovereign line was higher than that of cows of Wis Ideal line. However, in general, there were no signifi cant differences in lactation performance of cows of these lines. In the second and third months of lactation, cows of both lines had a decrease in the content of fat, protein and intensity of milk fl ow with a gradual increase in these indices in the fourth and fi fth months of lactation. First-calf cows with an average daily yield of 22.9 kg of milk had a higher content of fat and protein (by 0.98 and 0.40% respectively) than cows with an average milk yield of 36.6 kg. It was also noted that with the increase in the level of milk yield there was a tendency for the decrease in the latent period of milk ejection refl ex.

Relationships among quarter milk leukocyte proportions and cow and quarter-level variables under different intramammary infection statuses.

The use of milk leukocyte differential (MLD) test has been proposed as a complement to somatic cell count (SCC) to assess the presence and the severity of intramammary infection. However, detailed information regarding the behavior of MLD under different physiological or pathological stages of the cow is nonexistent. The objective was to analyze the association between milk leukocyte proportions provided by a commercial automated MLD test and multiple cow and quarter-level variables. The study population consisted of 104 Holstein cows (32 primiparous and 72 multiparous) in one farm. Cows were categorized by days in milk as early (<50 DIM; n=29), middle (50–250 DIM; n=25), and late lactation (>250 DIM; n = 50). Milk from 416 quarters was collected and analyzed for lymphocytes (LYM), neutrophils (NEU), and macrophages (MAC) counts using an automated milk fluorescence microscopy system. Concurrently, a sterile composite milk sample was collected from each cow for pathogen identification through microbiological culture. Culture results were classified as no growth (NOG), gram-negative (GN), gram-positive (GP), or other (OTH). Milk leukocyte proportions varied depending on the level of total leukocyte counts (TLC; P < 0.001). Similarly, leukocyte ratios (NEU:LYM, NEU:MAC, and phagocyte:LYM) were different for multiple TLC categories (P < 0.05). There was no association between parity number and MLD; however, cows in early lactation had the greatest proportions of NEU and LYM. Leukocyte ratios varied depending on parity number and stage of lactation. Cows in the medium milk-yield category had the smallest proportions of NEU and LYM, and there was significant variation in leukocyte ratios, depending on the level of milk yield. In healthy quarters, MLD were not associated with quarter position; however, the NEU:MAC ratio was greater in rear quarters than in front quarters. In quarters with TLC >100,000, NEU% was greater in rear quarters than in front quarters (P = 0.03). For quarters with pathogen growth, TLC was greatest for GN followed by OTH and GP (P < 0.001). Milk LD depended on the isolated pathogen group, although the magnitudes of the differences were small. Although the changes in the proportions of leukocytes in milk were associated with categories of TLC, levels of milk yield, and mastitis-causing pathogen groups, the deviations were small in magnitude. Additional research is necessary to determine the potential applications for this methodology.

Effect of milk production on reproductive performance in dairy herds

The objective of the present study was to assess the relationship between individual cow milk yield and fertility, accounting for the contextual effect of the herd. A data set including 657,968 lactations from 677 dairy herds in Argentina from 2001 to 2012 was used. The odds of pregnancy by 100 d in milk (DIM) were assessed by a multilevel logistic model (with cow as the first and herd as the second hierarchical level), and time to pregnancy was assessed by a proportional hazards regression model. Multilevel logistic models included the fixed effects of milk yield by 80 DIM, parity, year, and calving season at cow level and quartiles of herd milk yield by 80 DIM as a contextual effect. The proportional hazards model included the effect of daily cow-level milk yield as time-dependent variable, with milk yield at herd level as the stratification variable. Cows producing 1 standard deviation over the mean milk yield of their herd had 1.3 percentage point lower pregnancy by 100 DIM (from 31.4 to 30.1%; odds ratio = 0.942) when in herds in the top quartile of milk yield, whereas they increased 0.5 percentage points (from 27.9 to 28.4%) when in herds in the lowest quartile of milk yield. Only 4% of the observed variation in pregnancy by 100 DIM was explained by the random effect of the herd. Similarly, cows producing 1 standard deviation (8 kg/d) greater than the herd mean daily milk had 1.3% lower hazard of pregnancy (hazard ratio = 0.987) at 63 DIM in herds in the top quartile of milk yield, whereas they had 14.8% higher hazard (hazard ratio = 1.148) in herds in the lowest quartile of milk yield. The magnitude of the negative association between the cow's daily milk yield and the hazard of pregnancy increased with DIM. In conclusion, the relationship between milk yield and reproductive performance is statistically significant, but the effect size is practically small and is modulated by herd production level.

Milk production of Norwegian Red dairy cows on silages presumed either low or optimal in dietary crude protein content

Dairy cow diets often exceed protein requirements for milk production. At the same time, dietary protein use efficiency for milk production is low leading to excretion of large amounts of nitrogen to the environment. We assessed the effects of feeding two grass/clover silages mainly differing in crude protein (CP) content on milk and component yields, nitrogen and gross feed utilization efficiency with Norwegian Red dairy (NRF) cows. Forty-eight early- to mid-lactation NRF dairy cows were randomly allocated to two dietary treatments (n = 24) after blocking by initial milk yield, stage of lactation, body weight and parity. Cows were fed silages either low in CP (late cut silage, LCPS; 112 g CP per kg dry matter (DM)) or optimal (mixture of 4 different silages, OCPS; 142 g per kg DM) ad libitum for a period of 54 days. These basal diets were augmented with a fixed level of concentrate feed (160 g CP per kg DM). This was estimated using the Nordic Feed Evaluation System (TINE Optfor KU optimization program) assuming OCPS as an available silage. We hypothesized that OCPS would support higher milk yield than LCPS, and the LCPS cows would consume more feed if they were to achieve similar level of milk yield as their OCPS counterparts. Contrary to our hypothesis, milk (23.7 vs. 24.5 kg per day), energy corrected milk (25.2 vs. 25.6 kg per day) yields and milk components were not significantly different between the groups (LCPS vs. OCPS). Furthermore, LCPS cows sufficiently matched DMI from the silage part of the diet to that of the OCPS cows (12.7 vs. 12.4 kg per day). However, OCPS decreased (P < 0.01) nitrogen use efficiency compared to the LCPS (30 vs. 33%). Our results confirm that reduction in dietary CP levels (ca 130 g per kg DM) can be achieved without loss of production, with reduced N excretion to the environment and reduced cost of milk production in moderately yielding cows. This would have a positive contribution to the current efforts being made to base our dairy production on locally available resources with minimal recourse to imported inputs.

The relationship between milk progesterone and milk traits during estrus in dairy Cows

The aim of this study was to evaluate relationship between milk progesterone concentration (P4) and milk traits at the start of estrus time and 12h after start of the estrus in dairy cows. The 96 milk samples of 48 Lithuanian dairy cows without reproduction disorders and 90–100 days after calving were evaluated. Cows were classified into two groups based on milk yield per day: less than 30 kg (n=20) and e”30 kg (n=28). Data were categorized by milk fat and protein content at the start estrus and 12h after start of estrus to evaluate relationship between P4 and milk traits examined. P4 at estrus time in dairy cows was significantly positively correlated with milk yield (P less than 0.001), whereas it was negatively correlated with milk protein (P less than 0.05-P less than 0.01) and fat at 12h after start of estrus. Dairy cows with F/P from 1.0 to 1.5 had the lowest P4 in milk. Results of the pregnancy in dairy cows were related with lower P4 and milk yield level (P less than 0.001), higher milk fat (P less than 0.05) and milk protein content (P less than 0.001). These cows had 1.90 times lower prevalence of the signs of subclinical ketosis (P less than 0.05) at estrus time when compared with non-pregnant cows. As a result, it was clearly demonstrated that P4 in dairy cows can help to evaluate and improve the reproductive properties of cows.

COMPARATIVE ASSESSMENT OF SEXED AND TRADITIONAL SEMEN OF HOLSTEIN BULLS

Holstein dairy cattle are characterized by many outstanding qualities such as exterior constitutive type, level of milk yield per lactation and during the period of economic use, well developed udder in size and shape, adapted to machine milking and others. However, there are some negative aspects at the breeding of animals of this breed. This is a short period of practical use (2-2,5 lactation) and decreased fertility of breeding stock (67-72% – in the farms with intensive-industrial technologies). At high intensity of herd selection – 30-33%, it is practically impossible to obtain the expanded reproduction of a herd from its own resources. Therefore, it always has to depend on the import of heifers and feeder heifers. These circumstances may necessitate the development of special breeding activities which eliminate these problems.&#x0D; The science developed technology and laboratory equipment for sexed bull sperm and use of frozen-thawed sexed sperm relatively recently. Production test confirmed high efficiency of separation of spermiums by sex (bulls: heifers) – up to 92%. However, the high cost of sexed sperm and reasonable doubts of scientists and geneticists on the biological "harmlessness" of the proposed technology require further research in the future.&#x0D; The aim of our work was to conduct a comparative assessment of sexed and traditional sperm quality of the same Holstein bulls, which comes in straws and proposed for using in farms of Ukraine.&#x0D; Sexed and traditional (not sexed) sperm of Holstein sires of Canadian selection from "Simex Alliance Ukraine" LTD was used for research. The sperm of 4 sires: Benjamin CANM 7866444, Ardent HOUSAM 137922325, Mathys CANM 103439288, Vioris Sleeman HOCANM7817774 was taken for the analysis; each of the bulls had 3 sexed sperm doses and 3 traditional sperm doses. Total 24 sperm doses were studied.&#x0D; Thaw-frozen bull sperm was studied in the cryopreservation laboratory SPC "Zahіdplemresursy" Ltd., Lviv region using the technological equipment of the German company «Minitube» according to the software package CASA (Computer Assisted Semen Analysis) – Sperm Vision. Assessment of semen quality was conducted on indicators: concentration of sperms in 1ml, motility after thawing, number of sperms with rectilinear reciprocating movement (RRM), circular motion and stationary, and after incubation at 37 ° C after 60, 120, 180 minutes; acrosome intactness, level of microbial contamination.&#x0D; It has been established that motility and survivability of the sexed sperms were15-20% lower compared with these indicators of traditional sperm. Irrespective of the division of sperm by sex, we had the highest activity of the sperms of bull Vioris Sleeman HOCANM7817774. This indicates the possibility of bull selection by this indicator of quality sperm.&#x0D; The experimental results should not be assessed pessimistically. The similar problems occurred at the early stages of development and adopting of freezing and thawing technology of native bull sperm. We know that these issues have been successfully resolved.&#x0D; Therefore, the experimental results indicate necessity of improving the technology of freezing and thawing sexed bull sperm and preparing specialists of required qualification for the breeding centres laboratories and breeding enterprises in Ukraine.&#x0D; The genotype of a number of generations of progeny, obtained using sexed sperm should be systematically studied in the future.

Effect of milk cessation method at dry-off on behavioral activity of dairy cows

Drying cows off at the end of lactation is a routine management practice in dairy operations. Most dairies in the United States and many other countries dry cows off abruptly (e.g., stop milking cows on a set day), which has been shown to affect cow comfort. Gradually reducing milk production is another approach to dry cows off, routinely used in some countries and herds. The objective of the study was to evaluate the effects of abrupt and gradual milk cessation and milk yield at the time on cow activity after dry-off. Daily lying time, number of lying bouts per day, average lying bout length, and steps taken per day by abruptly and gradually dried-off cows were monitored by data loggers for 2 wk before and after the final milking at the end of lactation. Gradual cows were milked once daily for the last week of lactation, and abrupt cows were milked as usual (3×/d) until the end of lactation. Gradual cessation of milking significantly reduced milk yield by the day of dry-off. After dry-off, gradual cows tended to have longer lying bouts than abrupt cows, but no other differences in cow activity between the 2 treatments were observed. Regardless of the dry-off method, the average length of a lying bout decreased by 4 min and total daily lying time decreased by 19 min after dry-off for each 5-kg increase in milk yield before dry-off. Lying behavior of primiparous cows was more affected by the level of milk yield at dry-off than that of older cows. A reduction in lying times with increasing milk yield may indicate discomfort due to the accumulating milk in the udder. Using a method that lowers milk production before dry-off and managing primiparous and multiparous cows separately around dry-off are beneficial for cow comfort after dry-off.

Nonparametric and Semi-parametric Survival methods for Assessing days Open and Conception rates of Lactating cows

Evaluation of conception rates in dairy livestock requires specific statistical methods because of the followings: (i) some cows are still alive after the follow up period and their fate is not known, which means that records of these animals should be censored, (ii) the risk factors connected with fertility are not perform linearly and may vary with time, (iii) not all lactation records are normally distributed. Therefore, this study was undertaken to assess factors influencing days open (DO) and conception rates of dairy cattle, using nonparametric and semi-parametric survival functions. Parity, season of calving, milk yield levels (MYL), age at calving (AAC), days to first estrus (DFE), days to first insemination (DFI), number of inseminations per conception (NIPC) were significantly associated with days open for a number of 1980 lactation cows, of which 12.73 % were censored. The overall median of DO was 123 days (95 % CI = 119.55-126.44). For the first five parities studied, medians of DO were 111, 121, 128, 123 and 152 days, respectively. The Kaplan-Meier survivor functions and log-rank tests denoted highly significant differences (p < 0.001) among parities, seasons of calving and levels of milk yield in terms of time to conception. Proportions of pregnant cows were estimated at every postpartum time point alongside their cumulative probabilities. The overall percentages of pregnant cows were 0.5, 34.7, 67.2, 92.07 and 99.34 % at days 50, 100, 150, 200 and 250 postpartum. Cox PH models reveled significant contribution of all studied factors as hazards for conception. The hazard ratios (varied from 0.632 to 1.393) were used to quantify the exact differences between all categories. The present study has provided important survival functions that were used to identify and quantify the economic risk factors associated with days open length and conception rates of dairy cattle in Egypt.

Биохимический профиль коров в ранний период лактации, его особенности у коров с разной степенью сократимости матки и удоем

Биохимический профиль коров в ранний период лактации, его особенности у коров с разной степенью сократимости матки и удоем

RELATIONSHIP OF MILK PRODUCTIVITY OF COWS WITH LIVE WEIGHT AND AGE AT THE FIRST INSEMINATION

The efficiency of the use of cattle of one or another breed is determined both by the level of milk productivity and the ability of the cattle to reproduce. At the same time, the future reproductive capacity, milk yield and duration of economic use to a large extent depends on the live weight and age when heifers insemination.&#x0D; The purpose of research. Study the effect of live weight and age at the first insemination on the milk productivity cows of Ukrainian red dairy breed.&#x0D; Methods. The research was carried out in the breeding plant of the state enterprise "Elite" of the Kirovograd state agricultural research station of NAAS on 697 cows of Ukrainian red dairy breeds, which were found during 2004–2014. Milk productivity of cows and their live weight and age at the first insemination were investigated according to the materials of the primary zootechnical and pedigree records. The degree of connection of live weight and age at the first insemination with milk productivity was estimated by correlation analysis. One-factor dispersion analysis determined the level of influence of the age of the first insemination and live weight on the productivity of cows. The calculations were made using methods of mathematical statistics using the software package "STATISTICA-6.1".&#x0D; Results of research. By the analysis of milk production on experimental cows, determined, that its level depends on the live weight of animals at the first insemination. Therefore, cows with live weight at the first insemination was 420–439 kg, dominated by mercy unique live weight of 380 kg in the first lactation at 244 kg (6242 vs 5998 kg), td = 1,96 for the third – 1069 kg (7465 vs 6396 kg), td = 2,37 by best lactation 498 kg (7916 vs 7418 kg), td = 2,03, significance level for all lactation (P &lt; 0,05). To the milk fat, accordingly, the predominance was 13.2 kg (260,2 vs 247,0 kg), 22,9 (309,5 vs 286,6 kg) and 21,0 kg (325,1 vs 304,1 kg), the difference is close to the true values. The peers with a live weight of 400–419 kg and 440 kg and more also yielded in the first milk yield. The difference the milk I, III and the best lactation was 72 kg, 219 kg and 91 161 kg, 674, 589 kg for milk fat yield 5 kg, 10.3, 6.1 kg and 11.5 kg, 28.8, 19.5 kg, respectively. Due to the lesser number of animals, the vast majority of values did not reach a reliable level.&#x0D; Studies of milk productivity of cows, depending on the age of the first insemination, showed that its cow was the highest, which were counted at the age of 455 days. The lowest rates of dairy productivity were the animals that were fertilized at the age of 606 or more days.&#x0D; Correlation analysis found the highly reliable of feedback age insemination of cows milk yield in the first three lactation (-0,25 ... -0,37). Similar patterns of feedback for somewhat lower correlation coefficients are noted with the release of milk fat (-0,23 ... -0,33). Coherence of live weight at the I insemination and follow-on milk production was significantly lower (compared with age insemination) in absolute value, for only a certain level of first lactation milk yield and milk fat yield (P &lt; 0,05).&#x0D; The significant influence of the investigated factors on milk yield of cows is established. Thus, by milk yield and milk fat and protein for 305 days of lactation cows power of influence age of first insemination exceeded 50%, the fat and protein in milk index of potency is 32 and 30% by high-confidence values for milk yield and yield of milk protein and fat . Somewhat lower than 20 to 33%, the effect of live weight on the first insemination was shown on the performance of cows.&#x0D; Сonclusion. The heifers of the Ukrainian Red dairy breed in conditions of the Central region of Ukraine advisable to fertilize at the age of 455 days, or 14,5–15 months, when they reach the living weight of 420–439 kg.&#x0D; The revealed feedback of the inseminative age and milk productivity can be explained by more intensive growth, better development and economic rapidity of the previously diced heifers and its should lead to intensive rearing of young animals.&#x0D; Determined, that the force of age-old influence of the first insemination on the lactic productivity of the cows exceeds 50%, the live weight reaches from 20 to 33%. Discovered tendency also confirms the expediency of intensive growth of repair heifers.

Effects of abortion and other risk factors on conception rate in Iranian dairy herds

Abstract In order to estimate costs of abortion, influencing factors on conception rate (CR) need to be identified. Data from 6 commercial herds were used to determine influencing factors on CR in Iranian dairy herds. Insemination observations were assigned to 3-weeks in milk (3-WIM) records from 21 to 294 days after calving (2nd – 14th estrus cycle (3-WIM period)). After eliminating outliers and periods with missing records, the dataset included 200,580 insemination records of 31,830 cows observed between 2004 and 2014. A logistic regression model was developed to evaluate the effects of herd, parity, calving season, cumulative fat corrected milk yield level (CFCML), mastitis in current 3-weeks in milk period (MAS), experience of mastitis in previous 3-WIM periods (EMAS), days in milk for insemination (IDIM) and all significant 2-way interactions on CR. Overall, the CR (total cows pregnant/total number of inseminations) until 294 days in milk was 35.1% ranging from 31.7% to 40.1% across studied herds. The results of logistic regression analysis showed that the CR differs at the herd level. Furthermore, the herd effect significantly interacted with other factors, except EMAS, illustrating that the effects of the investigated factors on CR also differed between herds. The odds of conception decreased with higher parity, MAS incidence, and calving during warm seasons. The CFCML significantly interacted with other factors. Therefore the odds of conception for high or low yielding cows will depend on the herd, parity, IDIM, abortion and EMAS history. There was a general decrease in CR with abortion incidence. However, the probability of conception for aborted cow depended on other parameters in the model. The trend of CR during the lactation was season dependent. For example, for cows calving in winter the CR decreased with lactation stage, while for cows calving in summer the CR increased with lactation stage. Moreover, the predicted probability of conception for different parities, calving seasons, CFCML and EMAS varied across the lactation stages. An experience of mastitis was just an indirect influencing factor because of a significant interaction with IDIM and milk yield level. In conclusion, this study revealed that difference in CR between as well as within studied herds was remarkable. Moreover, calving season (due to for example heat stress in the warmer season) is a more important factor influencing CR than milk production.