Performance Of Holstein Cows Research Articles

The Association of Delayed Milk Ejection with Milking Performance in Holstein Cows in a Large Dairy Herd with Suboptimal Premilking Teat Stimulation.

The primary objective was to investigate the association between delayed milk ejection (DME) and the average milk flow rate, milking unit-on time, and duration in a low milk flow rate in Holstein dairy cows in a large dairy herd with suboptimal premilking teat stimulation. Our second objective was to study the association between peak lactation milk yield and the occurrence of DME. This longitudinal field study was conducted at a 4300-cow dairy farm with a thrice-daily milking schedule over a 1-week period. We analyzed data from 61,677 cow milking observations from 2937 cows. Delayed milk ejection was defined as present if the 30-60 s milk flow rate was ≤3.1 kg/min. The mean average milk flow rate (MAMF, kg/min), mean milking unit-on time (MMUT, s), and mean duration of a low milk flow rate (MLMF, s) were calculated as the mean values from the 21 milking observations. General linear multivariable models revealed associations of DME with MAMF, MMUT, and MLMF. A multivariable ordinal logistic regression model revealed an association between peak lactation milk yield and DME. Cows with lower peak lactation milk yield had greater odds of exhibiting a higher frequency level of DME. The observed associations between DME and milking performance indices suggest that DME can negatively affect milking and parlor efficiency. Peak lactation milk yield may serve as a proxy to estimate cows' risk of recurrent DME. Future research is warranted to test if alleviating DME through, for example, a modified milking routine influences the milking performance indices described herein.

The Anti-Müllerian Hormone as Endocrine and Molecular Marker Associated with Reproductive Performance in Holstein Dairy Cows Exposed to Heat Stress.

Anti-Müllerian hormone (AMH) is proposed as a biomarker for fertility in cattle, yet this associative relationship appears to be influenced by heat stress (HS). The objective was to test serum AMH and AMH-related single nucleotide polymorphisms (SNPs) as markers potentially predictive of reproductive traits in dairy cows experiencing HS. The study included 300 Holstein cows that were genotyped using BovineSNP50 (54,000 SNP). A genome-wide association study was then executed. Nine intragenic SNPs within the pathways that influence the AMH gene were found important with multiple comparisons adjustment tests (p < 1.09 × 10-6). A further validation study was performed in an independent Holstein cattle population, which was divided into moderate (MH; n = 152) and severe heat-stressed (SH; n = 128) groups and then subjected to a summer reproductive management program. Serum AMH was confirmed as a predictor of fertility measures (p < 0.05) in MH but not in the SH group. Cows were genotyped, which revealed four SNPs as predictive markers for serum AMH (p < 0.01), reproductive traits (p < 0.01), and additional physiological variables (p < 0.05). These SNPs were in the genes AMH, IGFBP1, LGR5, and TLR4. In conclusion, serum AMH concentrations and AMH polymorphisms are proposed as predictive markers that can be used in conjunction with genomic breeding value approaches to improve reproductive performance in Holstein cows exposed to summer HS conditions.

Effect of interleukin -6 level on reproductive performance in Holstein cows

Abstract: &#x0D; The current study was conducted in private dairy cows station located in middle of Iraq by using 80 samples of blood during the period 2021 – 2022 in aim to determine the effect of IL-6 concentration on reproductive performance. Results showed a significant effect (P≤0.01) of IL-6 level on reproductive traits parameters. Days open differed significantly according this interleukin and the highest days open was recorded in cows with low IL-6 level namely, 187.37 pg/ml. Service per conception differed significantly according to IL-6 level in blood plasma, the highest number of service per conception was recorded in cows with low IL-6 interleukin about 3.77 service. calving interval differed significantly according to IL-6 concentration, the longest period was noticed in cows with low IL-6 level compared with the shortest period which noticed in cows with moderate IL-6 level namely, 482.48 and 400.25 day respectively. Ovulation weakness differ significantly (P≤0.01) according to IL-6, the highest rate of infection was recorded in cows with high IL-6 level (63.64%) from total number about 33 cases while the lowest rate of ovulation weakness was noticed in cows with low IL-6 level namely, 21.21%.

Mineral supplementation (injectable) improved reproductive performance in Holstein cows managed in a warm summer environment.

Sustainability of dairy production depends largely on reproductive efficiency that is affected by heat stress due to high ambient temperature and humidity during summer. Supplementation of minerals has been proposed as a management strategy to minimize adverse impact of heat stress on fertility. The objective of this study was to determine the effects of an injectable mineral supplement (Fosfosan) containing selenium (Se), copper (Cu), potassium (K), magnesium (Mg) and phosphorus (P) on the ovarian structures, reproductive hormones and conception rate of heat-stressed Holstein cows. Sixteen cows were assigned during summer to one of two treatments, a control group (CON; n=8) and a mineral-supplemented group (SUP; n=8). Ambient temperature and relative humidity records were collected and processed to estimate the temperature-humidity index (THI), which confirmed a heat-stressed environment during the study (avg. THI=79.4). Cows were subjected to a fixed-time artificial insemination (FTAI) program using the CIDR-Synch synchronization protocol. Traits indicative of ovarian activity were recorded during and after this protocol, as well as serum concentrations of reproductive hormones. Pregnancy diagnosis was made 28 and 35 d after FTAI. A completely randomized block design with repeated measures over time was performed to study ovarian functional structures and its hormonal profiles. Correlations and regressions were estimated to study relationships between ovarian structures and related hormones. Mineral supplementation did not increase follicular diameter or follicular populations (p>.05), yet tended to increase corpus luteum diameter (p<.10), and it enhanced (p<.01) oestrogen and progesterone serum concentrations and improved (p<.05) cow's conception rate. Diameter of dominant follicles and corpus luteum was correlated (p<.05) with oestrogen and progesterone levels, respectively, but only in mineral-treated cows. Two additional dairy herds were evaluated to confirm that mineral supplementation improved conception rate during the heat stress period (objective 2). Cows from dairy 1 received FTAI during winter (n=401) and summer (n=240), whereas cows from dairy 2 were bred after natural detected oestrus during winter (n=558) and summer (n=314). Conception rates were higher (p<.05) in winter than summer and they improved (p<.05) with mineral supplementation, but only in cows managed during summer. In conclusion, supplementation of minerals enhanced hormonal secretion from ovarian structures and improved conception rate in Holstein cows exposed to summer heat stress.

Effect of Heat Stress During the Dry Period on Milk Yield and Reproductive Performance of Holstein Cows

Effect of Heat Stress During the Dry Period on Milk Yield and Reproductive Performance of Holstein Cows

Improving breeding and productivity qualifications of Holstein cow breeds (b. Taurus) in climate of Uzbekistan

This article accelerates the development of selection methods for selecting the best genotypes that are acceptable from the similarity genotypes of imported Holstein cattle typical of Chinese, German and Slovenian selection. The genetic potential of reproduction and productivity of breeding breeds in genotype-environment interactions has been demonstrated. The results of the same feeding, storage and performance of Holstein cows in summer and winter, the productivity characteristics of the cattle are presented.

Contribution of the mutation rs8193069 in TLR4 to mastitis resistance and performance in Holstein cows in southern China.

Bovine mastitis has become increasingly important issues for farmers and consumers, leading to large economic losses in the dairy industry worldwide. Because treatment of mastitis is difficult and costly, improved mastitis resistance through selective breeding would be advantageous. The toll‐like receptor 4 (TLR4) is an important player in recognising pathogens and activating immune responses. However, its roles in mastitis occurrence and the underlying molecular mechanisms are unclear. In this study, a single nucleotide polymorphism, rs8193069 (T → C) in TLR4 gene was detected in a Holstein cow resource population in southern China. Association analysis with 5‐year production traits, haematology, and biochemistry parameters revealed that individuals with genotype CC had significantly lower somatic cell counts (SCC), lower fat percentage, but higher 305‐day milk (p < 0.05) and total milk yield (p < 0.01). Both genotypes CC and CT had lower lymphocyte counts (#LYMPH) (p < 0.01) and basophil counts (#BASO) (p < 0.05) than TT. Genotype CC had a less level of triglyceride (p < 0.01) and creatine kinase (p < 0.05) than CT. Further analysis based on the production data revealed significant positive correlations between SCC and #LYMPH. Analysis of TLR4 protein structure and properties suggested that the missense mutation on the 674th amino acid from Thr to Ile reduced the flexibility and hydrophilicity of TIR domain, implying a weakened binding ability of TLR4 to its adaptors. In conclusion, allele C of rs8193069 was the major allele in Holstein cows that indicated a greater genetic potential to mastitis resistance and milk yields, probably via the LPS‐TLR4 inflammatory signalling. This study offers a marker to improve mastitis resistance in the dairy cow population in southern China.

The Association of Calcium Profiles at Calving with Health and Performance of Holstein Cows and Their Calves

The aim of this study was to assess the association of hypocalcemia at calving with health and performance of Holstein cows and their calves. Data were collected January 1st 2017 to December 31st 2020. A total of 431 lactating Holstein Friesian cows (118 primiparous and 313 multiparous) from a research of hypocalcemia was 2 groups (hypo and non-hypo). The overall prevalence of hypocalcemia was 3.4% for first-lactation cows and 18% for multiparous cows. Lactating dairy cows with hypocalcemia had greater proportion of cows with Retained Fetal Membranes (RFM) metritis and culling within 60 days in milk (DIM), compared with non-hypocalcemia respectively. For the first 2 official milk tests milk yield and components (% fat, % protein on SCC) did not differ between hypo and non-hypo cows. The days in milk at first service, mastitis, dystocia and pregnancy at first service were not different between hypo and non-hypo groups. The proportion of stillbirth, survival at 60 days of age in calves did not differ between calves born from hypo or non-hypo cows. Calves born from Hypo cows had greater incidence of diarrhea (38.3%) than calves born (22.3%) from non-hypo cows. The results of this study show that hypocalcemia in calving has significant health implications for both dams and their calves.&#x0D;

A two-step feeding of calcium salts of fish oil improves reproductive performance in Holstein cows

Aim of study: To examine the effects of a biphasic schedule of feeding n-3 fatty acids on dairy cows.Area of the study: Isfahan, Iran.Materials and methods: 140 lactating Holstein cows were allotted at calving into two groups of 70 animals and received one of two dietary treatments: 1) saturated fatty acids (SFA, containing 80% palmitic acid) or 2) calcium salt of fish oil (CSFO, containing 16% eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA)), with an n-6/n-3 FA ratio of approximately 7 for SFA and 5 for CSFO treatments. The dietary supplements were fed to the respective groups at 240 g/head.day from 0 to 21 days in milk, and 120 g/head.day from 22 to 150 days in milk. Milk yield was recorded biweekly and milk composition was evaluated monthly. The concentration of FA in the milk and blood was determined on d-90 of the experiment in 10 cows randomly selected from each group. Reproductive indices were recorded until d-150.Main results: The CSFO supplementation did not affect average milk yield, milk composition or milk somatic cell count (SCC); however, in some weeks it decreased milk SCC (p&lt;0.05). Plasma concentrations of palmitic acid and n-3 FA as well as milk fat concentration of EPA and DHA increased in the CSFO-fed cows (p&lt;0.05). Feeding the CSFO decreased open days (100 vs 119 days, p&lt;0.05), service per conception and all service conception rates (p&lt;0.05).Research highlights: The implementation of a two-stage feeding program of n-3 FA improved reproductive variables and reduced milk SCC in dairy cows.

Restricted Selection Index to Relieve the Negative Repercussion in Reproductive Performance of Holstein Cows

The aim of this investigation was to develop restricted selection index aiming to improve 305-day yields of milk (MY), fat (FY) and protein (PY), while keeping the deterioration in days open (DO), calving interval (CI) and number of services per conception (NSPC) at minimum levels in Holstein cows. The data represent 3682 records of 1122 cows, daughters of 95 sires and 712 dams. The data were analyzed by multi-trait animal model with repeated measures. Eight selection indexes (five unrestricted and three restricted) were derived using MY, FY, PY, CI, DO and NSPC in various combinations as sources of information in the indexes. However, the true breeding value included MY, FY and PY. The highest accuracy of selection (0.60) resulted from selection based on the full index. Milk yield and SPC appeared to be the most valuable traits in the full index. Combining the two traits into one index (the best reduced index) gave 0.57 accuracy of selection. The index based on MY alone (the most accurate single trait index) gave 0.53 accuracy. It seems possible to reduce the expected genetic deterioration in the reproductive traits by restricting the full index to result in zero genetic change in NSPC (rTI=0.48). This restriction will allow the breeder to mitigate the deterioration in DO and CI by 12 and 16 days respectively, by sacrificing with part of the expected genetic improvement in productive traits (29, 40 and 48% in MY, FY and PY, respectively).

Days in the prepartum group are associated with subsequent performance in Holstein cows

Our objective was to evaluate the association between days in the prepartum group (DPG) with performance and survival in Holstein cows. Data from 18,657 Holstein cow-lactations (6,993 nulliparous and 9,390 parous prepartum) were collected. Cows with a gestation length shorter than 256 d (n = 267) or longer than 296 d (n = 131) and cows that spent 0 DPG (n = 238) were removed, resulting in 18,021 cow-lactations. Data were collected for the first 300 d postpartum, and responses included milk yield, incidence of diseases by 90 d postpartum, reproduction, and survival. Days in the prepartum group were analyzed as a continuous variable, and regression coefficients were used to estimate the responses when cows spent 7, 28, or 42 DPG, representing cows with a short, moderate, or an extended time in the prepartum group, respectively. An interaction between DPG as a quadratic covariate and parity-diet was observed for milk yield by 300 d postpartum. Means were 9,331; 9,665; and 9,261 kg for 7, 28, or 42 DPG, respectively, in nulliparous cows, and 9,886; 10,939; and 10,117 kg for 7, 28, or 42 DPG, respectively, in parous cows. Also, the interaction between DPG and parity-diet affected retained placenta, metritis, mastitis, and morbidity. Morbidity affected 49.5, 52.9, and 59.5% of nulliparous and 49.7, 26.5, and 47.4% of parous cows that spent 7, 28, or 42 DPG, respectively. A linear association between DPG and pregnancy at first artificial insemination was observed with estimates of 37.0, 32.6, and 29.8% for 7, 28, and 42 DPG, respectively. On the other hand, a quadratic association was observed between DPG and the proportion of pregnant cows at 300 d postpartum, and estimates for 7, 28, and 42 DPG were, respectively, 71.7, 73.5, and 58.8%. A quadratic relationship was also observed for DPG and removal from the herd by 300 d postpartum, and estimates were 25.2, 22.9, and 34.4% for 7, 28, or 42 DPG, respectively. Associations between DPG with production, health, reproduction, and survival were detected, and they varied with parity-diet group. For several responses evaluated, a quadratic association was observed, which suggested that there was an optimal period for cows to spend in the prepartum group, and reduced or extended number of days were detrimental to performance.

Association between Fertility HCD Haplotype, Milk Production, and Reproductive Performance in Holstein Cows

The survey results of testing the Holstein cows for carriage of the fertility haplotype for cholesterol deficiency (HCD) associated with the fetal death detected at various stages of prenatal and early postnatal ontogenesis has been reported. Economically important traits of the animals tested as carrying the defect caused by HCD in their genotypes are examined. The survey sample consisted of the animals (n = 583) born in 2007–2017 on the breeding farm in Leningrad oblast. A comparative assessment of the HCD+-affected animals (tested carriers of a genetic defect caused by cholesterol deficiency) and the HCD–-unaffected animals (tested noncarriers of a genetic defect caused by cholesterol deficiency) was performed based on their milk production and reproductive performance parameters. DNA extracted from animal blood served as the testing material. The genotypes were determined based on the polymerase chain reaction with the use of allele-specific primers. It was found that 35 animals (6.0%) had a mutant allele at the ApoB gene locus present in their genotypes. These cows were not inferior to their genetic defect-free peers in breeding value for milk yields and milk protein and fat percentage. The HCD+-affected cows born in 2014 were characterized by higher values for the milk protein content (3.29 ± 0.05%) when compared to the HCD–-unaffected cows (3.17 ± 0.01%). A smaller number of sperm doses were used to reach effective insemination in the HCD carrier cows born in 2013 (n = 11) and 2014 (n = 11), which significantly affected the terms of the first effective-insemination. The cows born in 2014 carrying a mutant allele at the ApoB gene locus present in their genotypes had less service interval length when compared to their peers. The HCD+-affected cows used in production have no impact on overall herd performance and fertility. However, the animals with the HCD+ status should be identified and registered in a timely manner. The record-keeping system can allow us to reduce the number of carriers of this genetic defect in subsequent generations.

Periparturient stocking density affects lying and ruminating behavior and one-week-calf performance of Holstein cows

ObjectiveThis study aimed to investigate the effect of stocking density on the behavior, productivity, and metabolism of periparturient Holstein cows as well as calf performance.MethodsA total of 48 periparturient cows were randomly assigned into three groups at 28 days (±3 days) before their expected calving date. The stocking densities of the groups, relative to the standard cubicle and feed bunk number, were i) 80% (13 cows), ii) 100% (16 cows), and iii) 120% (19 cows). Lying and rumination behavior was recorded using electronic data loggers and HR-Tags from d −21 (“d-” means days before calving) until the calving date, d 0. Lying time was assessed to determine the diurnal total hours spent lying per day. Rumination time was averaged in 2 hours interval periods over 24 hours during the experimental period.ResultsCows in the 80% group spent more time lying and ruminating between d −21 and d −7 and tended to ruminate more between d −14 and d 0. Calcium levels tended to be higher for cows in the 80% group, no other observable differences were found in monitored blood parameters. Moreover, 3.5% fat corrected milk and energy corrected milk yields were higher in 80% group in the first month of lactation. No other observable differences were found in the yield and composition of colostrum and milk in the first 10 months of lactation. The growth and performance of calves in the first week of life was not affected by stocking density of the dams.ConclusionWe concluded that lower stocking density may increase lying and ruminating behavior of prepartum Holstein cows. However, this did not translate into improved productivity and metabolism.

Reductive acetogens isolated from ruminants and their effect on in vitro methane mitigation and milk performance in Holstein cows.

This study was designed to evaluate the in vitro and in vivo effects of reductive acetogens isolated from ruminants on methane mitigation, and milk performance, respectively. Four acetogens, Proteiniphilum acetatigenes DA02, P. acetatigenes GA01, Alkaliphilus crotonatoxidans GA02, and P. acetatigenes GA03 strains were isolated from ruminants and used in in vitro experiment. A control (without acetogen) and a positive group (with Eubacterium limosum ATCC 8486) were also included in in vitro experiment. Based on higher acetate as well as lower methane producing ability in in vitro trial, P. acetatigenes GA03 was used as inoculum for in vivo experiment. Holstein dairy cows (n = 14) were divided into two groups viz. control (without) and GA03 group (diet supplied with P. acetatigenes GA03 at a feed rate of 1% supplementation). Milk performance and blood parameters were checked for both groups. In in vitro, the total volatile fatty acids and acetate production were higher (p < 0.05) in all 4 isolated acetogens than the control and positive treatment. Also, all acetogens significantly lowered (p < 0.05) methane production in comparison to positive and control groups however, GA03 had the lowest (p < 0.05) methane production among 4 isolates. In in vivo, the rate of milk yield reduction was higher (p < 0.05) in the control than GA03 treated group (5.07 vs 2.4 kg). Similarly, the decrease in milk fat was also higher in control (0.14% vs 0.09%) than treatment. The somatic cell counts (SCC; ×103/mL) was decreased from 128.43 to 107.00 in acetogen treated group however, increased in control from 138.14 to 395.71. In addition, GA03 increased blood glucose and decreased non-esterified fatty acids. Our results suggest that the isolated acetogens have the potential for in vitro methane reduction and P. acetatigenes GA03 strain could be a candidate probiotic strain for improving milk yield and milk fat in lactating cows with lowering SCCs.

Effect of Dry Period Length on the Subsequent Lactation Performance in Holstein Cows under Subtropical Conditions

Effect of Dry Period Length on the Subsequent Lactation Performance in Holstein Cows under Subtropical Conditions

PSXIII-40 Monitoring in-line milk progesterone profiles prior to first breeding to predict reproductive performance in Holstein cows.

We investigated if milk progesterone (P4) profiles determined by an in-line milk P4 analysis system (Herd NavigatorTM, DeLaval Inc.) could be used to predict subsequent reproductive performance. Specifically, we evaluated associations of (1) commencement of luteal activity (C-LA), (2) first luteal phase length, (3) first P4 peak, and (4) number of luteal phases prior to first breeding, with pregnancy at first AI (P/1stAI) and cumulative pregnancy by 150 (P/150) d in milk (DIM). Milk P4 concentrations (ng/mL) were measured approximately every 2 d from ~21 DIM until pregnancy in 1,354 lactations (1,190 cows). Variations in P4 were used to define luteal function, such as C-LA, first luteal phase length, and pregnancy. All AI occurred within 5 d of P4 declining below 5 ng/mL. Variables were categorized into quartiles and data analyzed using GLIMMIX and PHREG procedures of SAS. First AI occurred at 70 ± 17 DIM. Overall P/1stAI and P/150 were 25.6 and 62.3%, respectively. Parameters associated with decreased probability of P/1stAI were first luteal phase length ≥ 17 vs. < 17 d (Odds Ratio [OR]: 0.13; P < 0.01), first P4 peak ≤ 17 vs. > 17 ng/mL (OR: 0.13; P < 0.01), and having one vs. two luteal phases prior to first AI (OR: 0.53; P < 0.01). The likelihood of P/150 was increased in cows that had C-LA before 50 than after 50 DIM (Hazard ratio: 0.64; P < 0.01), and in cows that had a first luteal phase ≥ 17 vs. < 17 d long (Hazard ratio: 0.58; P < 0.01). In summary, prolonged first luteal phase (≥ 17 d), low first P4 peak (≤ 17 ng/mL) and having only one luteal phase prior to first breeding reduced P/1stAI. Furthermore, a delayed C-LA (> 50 DIM) and a prolonged first luteal phase reduced likelihood of P/150.

Association between body condition score change during the dry period and postpartum health and performance

The objectives of the current study were to determine the association between body condition score change during the dry period (ΔBCS) and postpartum health and reproductive and productive performance of Holstein cows. Data from 16,104 lactations from 9,950 parous cows from 2 dairies located in the San Joaquin Valley of California were used. Within dairy, cows were scored for body condition at dry off and parturition by the same herd workers, who were trained by veterinarians from the Veterinary Medicine Teaching and Research Center of the University of California Davis. Cows were classified as having excessive loss of BCS (ΔBCS ≤-0.75; n = 1,604), moderate loss of BCS (ΔBCS = -0.5 to -0.25; n = 6,430), no change in BCS (ΔBCS = 0; n = 4,819), and gained BCS (ΔBCS ≥0.25; n = 3,251). Data regarding morbidity, mortality, and reproductive and productive performance were recorded until 305 d postpartum or until cows were dried off or left the herd. Loss of BCS during the dry period was associated with greater incidence of uterine disease and indigestion. Additionally, loss of BCS during the dry period was associated with greater likelihood of treatment with antimicrobials, anti-inflammatories, and supportive therapy. Loss of BCS during the dry period was associated with reduced likelihood of pregnancy after the first and second postpartum inseminations. Cows that gained BCS during the dry period had greater yield of milk, fat, and protein and had reduced somatic cell linear score in the subsequent lactation. In the current study, loss of BCS during the dry period was a predisposing factor associated with health disorders and reduced productive and reproductive performance in Holstein cows.

Management practices associated with reproductive performance in Holstein cows on large commercial dairy farms

As a result of the increase in herd size and the intensification of production, the complexity of reproductive management has been growing in dairy herds. The aim of our study was to examine the associations of management practices and reproductive performance in Holstein cows on large commercial dairy farms. Management practices applied to cows were surveyed between 22 May and 6 November 2015 in 34 large Holstein-Friesian dairy herds in Hungary. Individual data of 23 784 cows that calved between 1 January 2014 and 31 December 2014 in the surveyed herds were gathered. Associations between the management practices and the reproductive parameters were analyzed by mixed effects models. Regarding heat abatement we found that ventilation with sprinklers was associated with the shortest breeding interval (P<0.01), the shortest calving to conception interval (P<0.01), and the highest odds of being pregnant by 200 days in milk (P<0.01). Solely ventilation showed similar (P>0.05) results to lack of heat stress protection. It was also revealed, that lack of a well-established voluntary waiting period (VWP) or a VWP shorter than 50 days was associated with less days to first service (P<0.01), shorter breeding interval (P<0.01) and calving to conception interval (P<0.05), as well as higher odds of carrying a calf by 200 days in milk (P<0.01) compared with those using a VWP of at least 50 days. Those farms that applied transrectal ultrasonography were more likely to use ventilation with sprinklers (P<0.05), hormonal synchronization (P<0.01) and to perform early pregnancy diagnosis followed by pregnancy recheck (P<0.05). The application of transrectal ultrasonography with one of the aforementioned practices was associated with reduced days to first service (P<0.05), shorter breeding interval (P<0.05) and higher odds of pregnancy at 200 days in milk (P<0.05). Our study highlights the management practices most closely related to improved reproductive performance, which are, therefore, suggested to be applied on dairy farms, considering the local circumstances of the individual farms.

Production, Forage Quality, and Performance of Holstein Cows under Intermittent Grazing on Tifton 85

Tropical forage grasses compose the base diet of the Brazilian cattle herd due to their low production cost, high production potential, and good adaptation to various Brazilian ecosystems. In recent years, the search has intensified for alternatives that increase the yield in pasture milk production systems. Thus, the present study evaluated the production and quality of Tifton 85 grass in relation to the production parameters (e.g. greater leaf: stem ratio), and milk quality of Holstein cows in an intermittent grazing system during different seasons of the year. The experiment was conducted at the Córrego da Ponte Farm in Santa Helena de Goias, Goias, Brazil, from April 2014 to March 2015. The experiment used a completely randomized design with nine replicates and the four seasons (fall, winter, spring, and summer) as treatments. The Holstein cows had a live weight of 560±36.8 kg and averages four years of age. The grazing method used was a mob-stocking, with one day of grazing and 19 days of rest. The results showed that Tifton 85 was efficient regarding production parameters (total dry mass) and forage quality (IVDMD, NDF, ADF). The milk production was satisfactory during the fall, spring, and summer. The forage showed limited production during the winter, due the highest NDF, ADF levels and lower IVDMD (P &lt; 0.05), which was directly reflected in the milk yield, fat, protein and lactose (P &lt; 0.05). A reduction in the stocking rate or an increase in the number of paddocks is advisable during the winter to maximize milk production without compromising forage development. The correlation data showed the importance of consuming better-quality forage to increase milk production without compromising the levels of milk solids.

Effects of calving season on the voluntary waiting period and reproductive performance of Holstein cows in the tropical savannah.

The effects of calving season [rainy (RS) and dry (DS)] on the voluntary waiting period (VWP) of 58 Holstein cows raised in the tropical savannah were investigated using data of temperature humidity index (THI), total antioxidant status (TAS), respiratory rate (RR), rectal temperature (RT), glucose, total cholesterol (TC), triglycerides (TG), velocity of uterine regression, and subsequent reproductive performance. Blood samples and clinical data were taken once every week, from calving until the sixth postpartum week. Reproductive data were collected until 180days postpartum. THI differed between seasons (P<0.05], as well as TAS (P<0.001), RR (P<0.001), RT (P<0.01), glucose (P<0.001), TC, and TG (P<0.05), with higher values in RS. Although the velocity of uterine regression showed to be slower (P<0.001) during RS, no differences were present regarding uterine health. Days open increased in RS (P<0.001), but the number of services/conception was similar (P=0.33). The results suggested cows under heat stress during the rainy season in the tropical savannah are more susceptible to a decline in the reproductive performance due to oxidative, metabolic, and uterine health problems.