Effect of recombinant bovine somatotropin (rBST) on follicular IGF-I contents and the ovarian response following superovulatory treatment in dairy cows: a preliminary study

Somatotropin and FSH act synergystically on insulin-like growth factor-I (IGF-I) synthesis in ovarian follicles; IGF-I regulates several granulosa cell specific functions and may thereby be beneficial in bovine superovulation. In a series of 3 experiments we investigated the effects of recombinant bovine somatotropin (rBST) on several parameters of the superovulatory response in dairy cows. A total of 81 Holstein Friesian crossbred dairy cows received either 640 mg rBST or the vehicle (controls) on Day 4 or 13 of the superovulation schedule. Superovulation was induced with 2500 IU PMSG on Day 9. The cows were artificially inseminated on Day 13. In Experiment 1, on Days 4, 8, 11, 13 and 17 4 to 5 animals each were slaughtered to obtain follicular fluid, endometrium and plasma. The rBST application increased IGF-I contents in plasma and follicular fluid on Days 8, 11 and 13 (P < 0.05) in the treated cows when compared with that of the controls. Plasma and follicular IGF-I contents were correlated closely (rBST: r = 0.90, n = 10; control: r = 0.94, n = 9). The number of antral follicles increased following rBST treatment, and on the day of artificial insemination (AI) twice as many follicles > 4 mm were counted in the rBST treated animals than in the control group. In Experiment 2, the flushing of 38 donors on Day 7 after AI resulted in more transferable embryos in the rBST group than in the control group (4.2 +/- 1.0 vs 2.5 +/- 0.7; P < 0.05). In contrast, in Experiment 3 involving 21 animals when rBST was administered at the time of AI the superovulation response was not altered. It is concluded that rBST increases follicular and plasma IGF-I contents and thereby has profound effects on follicular and early embryonic development.     

Effects of continuous milking during a field trial on productivity,milk protein yield and health in dairy cows

The objective of this field study with an automatic milking system was to evaluate the effects of omitting the dry period on health and productivity during the subsequent lactation in dairy cows. A total of 98 German Simmental cows of six Southern German farms were assigned randomly to two experimental groups: The first group was dried-off 56 days before calving (D for dried-off, n=49), and the second group was milked continuously during this period until calving (CM for continuous milking, n=49). From the latter a third group emerged, including cows that dried-off themselves spontaneously (DS for dried-off spontaneously, n=14). Blood serum values of glucose, β-hydroxybutyrate (BHBA), non-esterified fatty acids (NEFA) and IGF-1 showed most pronounced fluctuations in D cows. Over the entire study period, the concentrations of BHBA and NEFA were markedly lower in the CM and DS groups. Furthermore, IGF-1 concentration was lowest for D cows and also decrease in back fat thickness was more pronounced. Mean concentration of milk protein was markedly higher in CM and DS cows (3.70% and 3.71%) compared with D cows (3.38%). Owing to the lower 305-day milk yield (−15.6%) and the lower total milk yield (−3.1%), the total amount of produced protein in the subsequent lactation was 2.5% (6.8 kg) lower, although the additional protein amount in CM cows from week −8 to calving was 35.7 kg. The greatest benefit resulted from positive effects on fertility and the lower incidence of diseases: CM cows had their first oestrus 1 week earlier compared with D cows, they also conceived earlier and showed a significantly lower risk of developing hypocalcaemia, ketosis and puerperal disorders. The present study showed that the costs of medical treatment and milk losses were twice as high in D cows, compared with CM and DS cows, and thus the reduced costs because of the more stable health outweighed the financial losses of milk yield by +18.49 € per cow and lactation.     

Genetic merit for milk production and reproductive success in dairy cows

The effect of genetic merit for milk production traits - fat, protein and milk yield - in dairy cows on milk production, body condition, blood metabolites, reproductive hormones, feed intake and reproductive performance was studied over a period of 2 years. Cows were grouped into two categories, based on calculated pedigree indices using multiple-trait across country evaluation (MACE). Cows of high genetic merit (HGM, n = 48 in year 1 and n = 46 in year 2) had a mean predicted difference +/- standard deviation for milk production of 475 +/- 76kg. The cows of medium genetic merit (MGM, n = 48 in both years) had a mean predicted difference for milk production of 140 +/- 68kg.The cows calved between January and April, and were offered grass silage ad libitum plus 9kg concentrates per cow per day, irrespective genetic merit, from calving to turnout in March, when they were subjected to one of three grazing systems. Cows were available for rebreeding from late April until late July of each year.High genetic merit cows had higher milk production, incurred greater body condition loss between calving and first service and had lower plasma glucose and insulin-like growth factor-1 (IGF-1) concentrations than medium genetic merit cows. Furthermore, HGM cows had lower first and second service and overall conception rates, and required more services per conception than the MGM cows.Cows that did not conceive to first service were retrospectively compared to those that conceived to first service within each genetic merit group. There were no significant differences between the HGM cows that did not conceive to first service and those that conceived to this service in terms of milk production, body condition score change between calving and first service, feed intake at first service, or in plasma concentrations of glucose, non-esterified fatty acids (NEFA) or IGF-1. Medium genetic merit cows that did not conceive to first service lost more body condition between calving and first service than did those that conceived to this service.In the present study, HGM cows had higher milk production and reduced reproductive performance in comparison with MGM cows. However, reproductive performance was not associated with milk production, feed intake or plasma concentrations of glucose, NEFA or IGF-1 between calving and first service, since there were no significant differences in these variates between high or medium genetic merit cows that did not conceive to first service and those that conceived to this service. Therefore, these variates are unlikely to be useful predictors of reproductive performance, under the conditions of the present study.     

Use of cow-side progesterone tests to improve reproductive performance of high-producing dairy cows

This study evaluated the effectiveness of the cow-side ELISA milk progesterone test in improving postpartum reproductive performance in the Dordt College dairy herd. Cows that produced more than 18,500 lb of milk per lactation were assigned to the high production group (40 cows), while cows that produced less than 18,500 lb of milk (42 cows) were assigned to the low production group. Twenty-one cows in the high production group and 19 cows in the low production group received no ELISA testing (untreated controls), while the remaining cows in each group were evaluated by ELISA test every 7 d beginning on Day 27 post partum (treated cows). A sequence of 2 high progesterone tests and 1 low test indicated the cows were cycling normally. Cows that had low milk progesterone levels (<5 ng/ml) for 3 consecutive tests were assumed to have follicular cysts and were treated with 2 ml GnRH (Cystorelin, 50 mug/ml). Cows that had 3 consecutive high tests (>5 ng/ml) were assumed to have persistent corpora lutea (CL) and were treated with 5 ml PGF(2)alpha (Lutalyse, 5 mg/ml). In both the high and low production groups, treated cows had higher (P < 0.08) pregnancy rates by Day 210 than the untreated controls (63.2 vs 38.1% and 56.5 vs 42.1%, respectively). The days open were reduced (P < 0.05) for the treated animals by 41.6 d compared with the controls. The treated cows produced a net savings of $70.42 (US) per cow assuming a $3.00 savings/day open.     

Effect of treatment with recombinant bovine somatotropin on responses to superovulatory treatment in swamp buffalo (Bubalus bubalis)

The objective of this study was to determine the effect of treatment with recombinant bovine somatotropin (rBST) on the response to superovulatory treatment in swamp buffalo. Estrous cycles of 16 buffalo cows were synchronized by intravaginal administration of progesterone and estradiol benzoate, and the cows were then randomly divided into 2 groups. The rBST-treated group received 250 mg of a sustained-release formula of rBST on Day 4 after progesterone implantation, whereas the control group did not receive rBST. Both groups were then given a superovulatory regimen of twice daily injections of FSH for 3.5 d (total dose of 260 mg, i.m.), between Days 9 and 11 after administration of progesterone. The cows were bred naturally 1 d after the last FSH injection, then 6 d after breeding they were slaughtered, and their reproductive tracts were removed. The numbers of corpora lutea (CL) and follicles were recorded, and embryos were flushed out of the uterine horns. There were no significant differences between the rBST-treated and control cows for the mean numbers (+/- SEM) of CL (6.0 +/- 2.2 vs 4.3 +/- 1.1), follicles (15.9 +/- 4.1 vs 19.8 +/- 2.9), or total embryos recovered per collection (4.5 +/- 1.6 vs 2.3 +/- 1.0). However, there were significant differences between rBST-treated and control cows for the numbers of transferable embryos per collection (3.0 +/- 1.0 vs 0.8 +/- 0.3; P < or = 0.05) and the overall proportion of transferable embryos (75 vs 33%; P < or = 0.01). The results of this study show that pretreatment of swamp buffalo with rBST significantly increases the production of transferable embryos in response to superovulation.     

Calling Biomarkers in Milk Using a Protein Microarray on Your Smartphone

Here we present the concept of a protein microarray-based fluorescence immunoassay for multiple biomarker detection in milk extracts by an ordinary smartphone. A multiplex immunoassay was designed on a microarray chip, having built-in positive and negative quality controls. After the immunoassay procedure, the 48 microspots were labelled with Quantum Dots (QD) depending on the protein biomarker levels in the sample. QD-fluorescence was subsequently detected by the smartphone camera under UV light excitation from LEDs embedded in a simple 3D-printed opto-mechanical smartphone attachment. The somewhat aberrant images obtained under such conditions, were corrected by newly developed Android-based software on the same smartphone, and protein biomarker profiles were calculated. The indirect detection of recombinant bovine somatotropin (rbST) in milk extracts based on altered biomarker profile of anti-rbST antibodies was selected as a real-life challenge. RbST-treated and untreated cows clearly showed reproducible treatment-dependent biomarker profiles in milk, in excellent agreement with results from a flow cytometer reference method. In a pilot experiment, anti-rbST antibody detection was multiplexed with the detection of another rbST-dependent biomarker, insulin-like growth factor 1 (IGF-1). Milk extract IGF-1 levels were found to be increased after rbST treatment and correlated with the results obtained from the reference method. These data clearly demonstrate the potential of the portable protein microarray concept towards simultaneous detection of multiple biomarkers. We envisage broad application of this ‘protein microarray on a smartphone’-concept for on-site testing, e.g., in food safety, environment and health monitoring.     

Single nucleotide polymorphisms in the growth hormone and insulin-like growth factor-1 genes are associated with milk production, body condition score and fertility traits in dairy cows

The somatotrophic axis (GH-IGF) is a key regulator of animal growth and development, affecting performance traits that include milk production, growth rate, body composition, and fertility. The aim of this study was to quantify the association of previously identified SNPs in bovine growth hormone (GH1) and insulin-like growth factor 1 (IGF-1) genes with direct performance trait measurements of lactation and fertility in Holstein-Friesian lactating dairy cows. Sixteen SNPs in both IGF-1 and GH1 were genotyped across 610 cows and association analyses were carried out with traits of economic importance including calving interval, pregnancy rate to first service and 305-day milk production, using animal linear mixed models accounting for additive genetic effects. Two IGF-1 SNPs, IGF1i1 and IGF1i2, were significantly associated with body condition score at calving, while a single IGF-1 SNP, IGF1i3, was significantly associated with milk production, including milk yield (means ± SEM; 751.3 ± 262.0 kg), fat yield (21.3 ± 10.2 kg) and protein yield (16.5 ± 8.0 kg) per lactation. Only one GH1 SNP, GH33, was significantly associated with milk protein yield in the second lactation (allele substitution effect of 9.8 ± 5.0 kg). Several GH1 SNPs were significantly associated with fertility, including GH32, GH35 and GH38 with calving to third parity (22.4 ± 11.3 days) (GH32 and GH38 only), pregnancy rate to first service (0.1%) and overall pregnancy rate (0.05%). The results of this study demonstrate the effects of variants of the somatotrophic axis on milk production and fertility traits in commercial dairy cattle.     

Variations in serum levels of insulin-like growth factor-1, growth hormone and thyroid hormones during lactation in dairy cows.

1. Serum levels of insulin-like growth factor-1 (IGF-1) in dairy cows declined after parturition, remained low during the period of early lactation with peak milk production and rose gradually until the end of lactation thereafter. 2. Growth hormone (GH) levels in sera of cows changed in parallel with milk yields. 3. Serum thyroxine and triiodothyronine levels during lactation remained fairly constant.     

Soluble form of ICAM-1, VCAM-1, E- and L-selectin in human milk

In breast milk and paired serum from 70 lactating women and 40 of their term, infection-free neonates, on the 2nd and 5th day postpartum slCAM-1, sVCAM-1, sE- and sL-selectin were measured by ELISA and compared with those in 26 healthy adults (controls). Seven infant formulas and fresh milk from five cows were also analyzed. Human colostrum values of slCAM-1, sVCAM-1 (similar to those in maternal and control serum), sE-selectin and sL-selectin (-10 and -100 times lower than in maternal and control serum) were significantly higher than those in milk, while they varied widely. None of the adhesion molecules was detected in fresh cow's milk or infant formulas. Exclusively breast-fed infants showed significantly higher values of slCAM-1 and sL-selectin on the 2nd day of life than those supplemented also with formula. Only slCAM-1 values correlated positively between colostrum and time-matched maternal serum. These findings show in human milk important amounts of slCAM-1 and sVCAM-1 but minimal amounts of sE- and sL-selectin, which could affect the immune system of the neonate.     

Field evaluation of the MM3-SERO ELISA for detection of anti-Fasciola IgG antibodies in milk samples from individual cows and bulk milk tanks

We carried out a field evaluation of the MM3-SERO ELISA for the diagnosis of Fasciola hepatica infection, by analysing serum and milk samples from individual cows and samples from bulk milk tanks. The diagnostic performance of the assay was assessed with serum samples from all 257 cows in eight fluke-free herds, and 240 cows with natural fasciolosis (diagnosed in vivo and/or post-mortem). Assay performance for individual milk samples was determined by analysis of paired serum and milk samples from 947 lactating cows from 33 F. hepatica-infected farms. The diagnostic usefulness of the assay for bulk tank milk was evaluated by analysis of bulk milk from infected (33) and non-infected (35) farms. For serum samples, the sensitivity, specificity and diagnostic accuracy of the assay were respectively 99.2% (95% CI: 97.0%–99.9%), 100% (95% CI: 98.6%–100%) and 0.997 (95% CI: 0.987–1.000). The only two infected animals in which serum antibodies were not detected had very low parasitic burdens (with only 2 and 3 flukes observed). The performance of the MM3 SERO ELISA for individual milk samples was similar to that for serum samples, and the stepwise linear regression revealed a strong correlation between the results for the milk samples and the serum samples (R² = 0.84; p < 0.001). The agreement between results obtained with pairs of serum and milk samples was very high: there was matching classification in 96% (910/947) of paired samples (kappa = 0.92; p < 0.001). Individual milk samples may therefore be used, instead of serum samples, in the MM3-SERO ELISA, for reliable detection of seropositive cows. Testing bulk tank milk samples enabled detection of infected herds, even when the within-herd prevalence of infection was as low as 12%. We conclude that the MM3-SERO ELISA is a sensitive and highly specific test for serodiagnosis of bovine fasciolosis, and can be used with individual samples of either serum or milk. Use of the assay with bulk milk samples enables estimation of the within-herd prevalence of infection.     

Hierarchy of factors affecting behavioural signs used for oestrus detection of Holstein and Normande dairy cows in a seasonal calving system

As oestrous expression of dairy cows has decreased over the last decades oestrus detection has become more difficult. The objective of this study is to identify the main factors that affect oestrus detection in seasonal calving dairy cows, and to establish their relative importance. In each of 5 years 36 Normande and 36 Holstein cows were assigned to a Low or High winter-feeding level group. Half of each group was then assigned to a Low or High pasture-feeding group. The Low-Low strategy resulted in the lowest milk yield and the greatest body condition (BC) loss from calving to nadir BC score (6302 kg; -0.98 unit). The High-High strategy had the converse effect (7549 kg; -0.75 units). Low-High and High-Low strategies had intermediate values. The Normande cows had lower milk yield and BC loss than Holstein cows (6153 kg versus 7620 kg; -0.82 unit versus -1.20 unit). A database of 415 observed spontaneous oestruses was created. Oestruses were classified according to detection signs: (1) standing to be mounted, (2) mounting without standing, (3) other signs without standing or mounting (slight signs). Presence of another cow in oestrus, access to pasture, Normande breed and Low-Low strategy increased standing detection. In the Normande breed, 97% of oestruses were detected by standing while combining the presence of a herdmate in oestrus and access to pasture with a milk production of less than 6550 kg. Holstein cows had a higher frequency of slight signs oestruses than Normande ones, which was associated with a decreased subsequent calving rate (P<0.05). In multiparous Holstein cows, the odds of slight signs detection was multiplied by 7.8 for the High-High group in comparison with the Low-Low group (P<0.05). In our study milk yield had an effect on oestrus detection which was not explained by BC loss. As High-High cows produced more milk than others, we logically found that an increase in milk yield increased slight signs detection. Conversely, as they lost less BC than others, BC loss improved the chance of standing or mounting detection. These two results show that an increase in milk yield may reduce oestrous behaviour even if BC loss is moderate. Oestrus detection is crucial in seasonal compact calving systems. High phenotypic milk yields appear unsuitable with such systems in regard to depressed oestrous behaviour.     

MicroRNAs expressed by human cytomegalovirus

The detection of antibodies against capripoxvirus has become easier with a commercially available ELISA validated for serum and plasma. In order to explore its suitability for immunological investigations on alternative samples, this study targeted milk as sample matrix available through non-invasive sampling. Samples for this study were collected from dairy cows vaccinated against LSD in an area without reported LSD virus circulation. Paired serum and milk (individual and bulk) samples were tested by ELISA without and with modifications of the sample incubation time for the milk samples. For the evaluation of the test specificity, 352 milk samples from a milk repository in Germany were used as negative control. Receiver operating characteristic analysis was performed for determination of the Youden index and determination of the most suitable cut-off value for maximum specificity. From 154 analyzed serum samples from Serbia, 75 were detected as positive in the ELISA. Sensitivity and specificity of the ELISA test for milk samples reached values of 88 to 91% using Youden criteria. A cut-off of 10 was determined aiming for maximum specificity. This cut-off value was used for further analysis. Using the protocol for serum, out of 154 milk samples, 38 were detected as positive, number of positive detected milk samples increase up to 48 with modified protocol. Milk samples from Germany reacted negative, except two samples that had borderline results using modified protocol. Significant statistical difference (p < 0.05) was observed between two incubation protocols. The detection of LSD-specific antibodies from bulk milk samples (pools of 2–10 individuals) came along with a reduced sensitivity over the sample of individual animals. Results show that the detection of capripoxvirus specific antibodies in milk samples using the commercially available ELISA from IDvet is feasible and can represent a helpful tool for LSDV monitoring programs.     

Ovarian structures and uterine environment are associated with phenotypic and genetic merit for performance in lactating dairy cows

The objective of this study was to estimate the association between detailed reproductive phenotypes for cows categorized as divergent for phenotypic and genetic performance. The hypothesis was that higher yielding animals, either phenotypically or genetically, would have compromised ovarian and uterine reproductive performance. Detailed reproductive traits including multiple ovulations, cystic ovarian structures, corpus luteum (CL) presence, and uterine environment were available on 9675 ultrasound records from 8174 dairy lactating cows, calved between 10 and 70 days. Cows were categorized, within parity, into low, average, or high for each of the performance traits. There was a greater likelihood of multiple ovulations in cows with greater phenotypic yields (odds ratio: 1.53–1.81) and greater genetic merit for yield (odds ratio: 1.31–1.59) relative to lower performing contemporaries. After adjustment for genetic merit, a similar trend of increased odds (odds ratio: 1.29–1.87) of multiple ovulations in higher yielding cows was observed compared with the lowest yielding category. There was no association between either phenotypic milk composition or genetic merit for milk composition with the likelihood of multiple ovulations. The likelihood of cystic ovarian structures was highest in cows with greatest phenotypic milk yields (odds ratio: 2.75–3.24), greater genetic merit for milk yield (odds ratio: 1.30–1.51), and even after adjustment for genetic merit there was a greater likelihood of cystic ovarian structures in cows with the highest milk yields (odds ratio: 2.71–2.95), compared with cows in the lowest category for each of the milk traits. Cows with average phenotypic milk yields were more likely to have a CL, compared with the lowest yielding category (odds ratio: 1.20–1.23), and these associations remained after adjustment for genetic merit of the trait. The likelihood of CL presence was highest in cows with the lowest genetic merit for milk. Lower fat:protein ratio was associated with an increased likelihood of CL presence compared with cows with greater fat:protein ratio and cows with the highest phenotypic milk composition were more likely to have a CL compared with cows in the lowest composition category. Genetic predisposition to higher somatic cell score was associated with a reduced risk of multiple ovulations (odds ratio: 0.69; 95% CI: 0.55–0.87) but an increased likelihood of CL presence (odds ratio: 2.66; 95% CI: 2.09–3.37) and poorer uterine health score (odds ratio: 1.36; 95% CI: 1.20–1.55). There was a lower likelihood of multiple ovulations, cystic ovarian structures, and poorer uterine health and an increased likelihood of CL presence in cows with superior genetic merit for reproductive performance and survival.     

An enzyme-linked immunoassay of milk progesterone as a diagnostic aid in embryo transfer programs

The objective of this study was to use an enzyme-linked immunosorbent assay to measure progesterone (P(4)) in donor cows as an indicator of reproductive normality and response to superovulatory treatment. Forty-eight Holstein cows were superovulated, and blood and milk samples were collected four times: 1) at initial follicle stimulating hormone treatment, 2) just prior to administration of prostaglandin F(2)-alpha, 3) at estrus and 4) at the time of embryo recovery, 6 to 7 d after estrus. Cows were inseminated twice during estrus. The P(4) profiles (ng/ml) obtained at the four collections, were, respectively, as follows: blood plasma, 2.4, 2.7, 0.2 and 11.2; defatted milk analyzed by radioimmunoassay, 3.7, 3.8, 0.5 and 14.6; preserved whole milk analyzed by ELISA, 6.3, 7.8, 0.7 and 19.1; frozen whole milk analyzed by ELISA, 9.8, 10.0, 0.8 and 21.1. All four assays resulted in the expected pattern of P(4) values for most cows at the four stages sampled. Approximately 10% of the cows had P(4) concentrations outside of the expected range of values. A majority of these cows were aberrant, based upon behavior and palpation of the reproductive organs. The rapidly available P(4) results from the ELISA were useful in making appropriate decisions regarding management of donor cows.     

Concentrations of progesterone in milk as a monitor of early pregnancy diagnosis in dairy cows

The objectives of the experiment were to evaluate the efficacy of using progesterone concentrations in milk and palpation per rectum on days 21 or 22 postbreeding to estimate pregnancy and evaluate management practices; and to investigate physiological occurrences leading to incorrect diagnosis of pregnancy when serial samples of milk were collected. Of particular interest were indications of early embyronic death and insemination of cows not in estrus. Milk samples were collected at the afternoon milking of days 0 or 1 (day 0 = day of estrus), 9 or 10, 21 or 22 and 27 or 28 following breeding in 200 lactating dairy cows. Tentative diagnosis of pregnancy was made based on concentrations of progesterone in milk on days 21 and 22 alone and on days 21 or 22 and 27 or 28. In addition all cows were palpated per rectum on days 21 or 22 postbreeding and a tentative pregnancy diagnosis was made. Pregnancy was confirmed by examination of the genital tract per rectum between 35 and 50 days after breeding. Values of 4 ng/ml or greater and/or the presence of a mature corpus luteum were considered positive signs of pregnancy. Progesterone in milk ranged from 0.1 to 18 ng/ml. On days 0 or 1, 9 or 10, 21 or 22 and 27 or 28 concentrations of progesterone in milk averaged 1.5 +/- 0.3, 11.1 +/- 0.5, 12.0 +/- 0.4 12.5 +/- 0.5 ng/ml for pregnant cows. Corresponding samples from nonpregnant cows averaged 1.2 +/- 0.2, 10.3 +/- 0.4, 3.0 +/- 0.4, 6.8 +/- 0.6 ng/ml, respectively. Ninety-six and 104 cows were classified as pregnant and nonpregnant on days 21 or 22 as compared to 78 and 118 cows diagnosed as pregnant and nonpregnant on days 21 or 22 and 27 or 28 combined. Pregnancy detection by progesterone in milk on days 21 or 22 with pregnancy determined via rectal palpation 35 to 50 days postbreeding was 77 and 100% accurate for positive and negative diagnosis, respectively. The percent agreement using progesterone in milk on days 21 or 22 and 27 or 28 combined was 95 and 100%, respectively, for positive and negative diagnosis. Diagnosis based on rectal palpation 21 or 22 days postbreeding was 63 92 (69%) and 76 88 (87%) for pregnant and nonpregnant cows, respectively. Ten of the 200 cows had progesterone concentratins in milk of > 4 ng/ml at the time of breeding. Six of these cows were pregnant from a previous insemination. The other four cows were nonpregnant and were inseminated during the luteal phase of the cycle. In conclusion, measurement of progesterone in milk is a useful tool in early detection of pregnant and nonpregnant cows and may be useful in detecting reproductive problems in a dairy herd. It will probably be most useful when used in combination with later pregnancy diagnosis per rectum .     

An automated method for the detection of staphylococcal heat stable deoxyribonuclease in dairy products

An automated sandwich immunoassay with specific polyclonal antibodies for the detection of Staphylococcus aureus thermostable nuclease (DNase) is described. To evaluate this assay, different quantities of purified S. aureus nuclease were added to dairy products. Additionally, staphylococcal counts and nuclease activity of milk samples inoculated with S. aureus were determined. Different extraction procedures were performed and compared. The results indicated that the automated test was a reliable method for detecting DNase activity in milk products. The procedure was completed in 2 h and detected 1 ng of DNase ml-1. Detection of the DNase was especially useful in cheeses and could be used to confirm positive enterotoxin results.     

Non-specific adsorption of fish immunoglobulin M (IgM) to blocking reagents on ELISA plate wells

Enzyme-linked immunosorbent assay (ELISA) is a popular technique for quantifiable detection of specific antibodies in warm-blooded animals, but it has not been accepted for detection of fish antibodies because of its low reproducibility, which is due in part to high background optical density (OD) measurements. In the present study, we report that the high background of a fish antibody-detection ELISA resulted from non-specific adsorption of fish immunoglobulin M (IgM) to blocking reagents on the ELISA plate wells. Four fish sera (from rainbow trout Oncorhynchus mykiss, masu salmon O. masou, Japanese flounder Paralichthys olivaceus and koi Cyprinus carpio) were poured into ELISA plate wells pre-blocked with several blocking reagents (skim milk, soybean milk, bovine serum albumin, fetal bovine serum, gelatin and Roche BlockingReagent) and then washed out in order to measure the remaining fish IgM on the ELISA plate wells. Significant amounts of fish IgMs (OD absorbance at 492 nm: 0.3 to 1.1) remained on the ELISA plate wells with no antigenic protein except blocking reagents. The amount of remaining fish IgMs on the ELISA plate wells decreased significantly following treatment of fish sera with skim milk. However, the specific immuno-reactivity of fish IgM was not reduced by such treatment. Thus, we conclude that treatment of fish sera with skim milk is useful in reducing the high background OD often observed in fish IgM detection ELISA.     

The effect of in vitro treatment of bovine embryos with IGF-1 on subsequent development in utero to Day 14 of gestation

Culture of bovine embryos with insulin-like growth factor-1 (IGF-1) can improve development to the blastocyst stage and embryo survival following transfer to heat-stressed, lactating dairy cows. Two experiments were conducted to determine whether IGF-1 could improve embryo survival and development at Day 14 after ovulation. In Experiment 1, non-lactating Holstein cows (n=58) were selected as recipients following synchronization for timed-embryo transfer. Embryos were produced in vitro and cultured with or without 100ng/mL IGF-1. At Day 7 after expected ovulation (Day 0), groups of 7-12 embryos were randomly transferred to each recipient. Embryos were recovered at Day 14. Embryo length and the presence or absence of an embryonic disc was recorded. Recovered embryos were cultured individually for 24h to determine interferon-tau (IFN-tau) secretion. There was no effect of IGF-1 on embryo recovery rate, embryo length or IFN-tau secretion. In Experiment 2, non-lactating (n=56) and lactating (n=35) Holstein cows were selected as recipients following synchronization for timed-embryo transfer. Embryos were produced as described in Experiment 1. At Day 7 after expected ovulation (Day 0), a single embryo was randomly transferred to each recipient. Embryos were recovered at Day 14. Embryo length and IFN-tau secretion were determined as in Experiment 1. Recovery rate at Day 14 tended (P=0.1) to be higher for recipients that received IGF-1 treated embryos compared to control embryos (43.2% versus 26.1%, respectively). There was no effect of IGF-1 on embryo length or IFN-tau secretion. In conclusion, results suggest that exposure to IGF-1 through Days 7-8 of development does not enhance capacity of embryos to prevent luteolysis. Results of the single embryo-transfer experiment suggested that IGF-1 treatment might affect embryo survival post-transfer as early as Day 14 after ovulation. Further experimentation is warranted to verify this finding.     

Comparison of three devices for the automated detection of estrus in dairy cows

Considerable technological advances have been made in the automated detection of estrus in dairy cattle, but few studies have evaluated their relative performance on the same animals or assessed cow-related factors that affect their performance. Our objective was to assess the performance and reliability of three devices commercially available in France for cow estrus detection. The devices were a pedometer (PM; Afitag) and two activity meters (AM1; Heatime-RuminAct, and AM2; HeatPhone). Two algorithms were tested for AM2. We fitted 63 lactating Holstein cows with the three detectors from calving to 90 days after calving. The onset and pattern of cyclicity were monitored from 7 to 90 days postpartum measuring progesterone concentration in milk twice weekly. A total of 211 ovulations were identified. Cyclicity was classified as normal in 60% of cows (38/63). Calculated over the operating period of all the devices (179 periods of estrus), the sensitivities and positive predictive values were, respectively, 71% and 71% for PM, 62% and 84% for AM1, 61% and 67% for the first algorithm of AM2, and 62% and 87% for the second algorithm of AM2. Both activity meters had a lower sensitivity but a higher positive predictive value than the PM (P < 0.05). For all devices, the performance in estrus detection was much poorer at the first postpartum ovulation than at subsequent ovulations (P < 0.05). Lactation rank and milk production affected some devices (P < 0.05). These devices could be used to reinforce visual observations, especially after 50 days postpartum, the minimum recommended delay to insemination. However, their full benefit remains to be verified in different farming systems and taking into account the specific objectives of the dairy farmer.     

Metabolic hormones,grazing behaviour,offspring physical distance and productive response of beef cow grazing at two herbage allowances

Herbage allowance (HA) management during gestation–lactation cycle of cows grazing native grasslands improves pregnancy rates and calves’ weaning weight records. Those improvements were associated with greater herbage mass, and better body condition score (BCS) and metabolic status of the cows, which could affect grazing and maternal behaviour, particularly when temporary suckling restriction (TSR) and flushing (FL) is applied. The objective of this study was to evaluate the effect of HA during the gestation–lactation period on cows’ and calves’ liveweight (LW), BCS, milk yield, insulin, IGF-1 and leptin concentrations, as well as the proportion of diurnal grazing activities (grazing, ruminating, walking and idling), and maternal behaviour from −10 to 70 days relative to TSR (day 0 = initiation of TSR at 86 ± 10 days relative to calving). Thirty-three primiparous Hereford cows were allocated to HA treatments during gestation and lactation, which annually averaged 2.5 (low = LHA) and 4 kg DM/kg LW (high = HHA). The LW and BCS of cows did not differ during −10 to 50 days but were greater in HHA than LHA at the end of the study (P < 0.05). Concentrations of IGF-1 were greater in HHA compared to LHA, while insulin and leptin did not differ. Grazing was lower in HHA than LHA, and the opposite occurred with ruminating and idling (P < 0.05). Cow–calf physical distance was greater in LHA cows compared to HHA (P < 0.05) and increased greatly in the former group after FL, while this increase was lower and later in HHA cows. Milk yield was greater in HHA (P < 0.05), and calves’ weight did not differ between treatments from day −10 to 35, but was greater in HHA compared to LHA from 45 days until the end of the study. Thus, the HHA in a low herbage height and mass condition resulted in greater IGF-1 concentrations and milk yield, and induced changes in grazing and maternal behaviour that were associated with increased cows’ LW, BCS and calves’ weight at the end of the study.