Incidence of silent ovulation in dairy cows during post partum period

The present study was undertaken to show the incidence of silent ovulation in high producing dairy cows, by monitoring ovarian cyclicity based on practical milk progesterone assay which was established in this study. The direct milk progesterone enzyme linked immunosorbent assay (ELISA) was developed using anti-progesterone-3(E)-carboxymethyloxime-BSA antibody for the antibody and horse radish peroxidase labeled progesterone for tracer. High sensitivity (26 pg/mL, 0.65 pg/well), high recovery rates (83-97%), high reproducibility (CV of intra-assay 4.8-11.5%; CV of inter-assay 14.3-19.1%) and high correlation between milk progesterone concentrations measured by the direct ELISA and the values obtained by the ELISA after extraction proved the reliability of the assay. In second experiment the incidence of silent ovulation was investigated based on the milk progesterone concentrations in 32 dairy cows within 70 days post partum. The incidences of silent ovulation at the first, second, third and fourth ovulation post partum were 83, 46, 13 and 0%, respectively. Most commonly observed patterns of sequential occurrence of silent ovulation in cows ovulating 2, 3 or 4 times within 70 days post partum were silent-estrus (50%), silent-silent-estrus (60%) and silent-silent-estrus-estrus (67%), respectively. These results suggest that the present ELISA is a reliable and practically applicable method for determination of progesterone in milk and that high producing dairy cows show a high incidence of silent ovulation at the first post partum ovulation as well as the second ovulation, which then decreased with the increased frequency of ovulation.     

The diagnostic and prognostic significance of ketonuria in fertility disorders of cattle

The diagnostic and prognostic significance of ketonuria for the prognosis of reproductive disorders in high-performance dairy cows was examined in 3 herds of Holstein Friesian and Holstein Friesian x Hungarian Red Pied F1 that were either primiparae or were due to calve for the 2nd to 8th time during the study period from mid-February to late March, 1988. The course of uterine involution and status of the ovaries was followed up by regular rectal and vaginal examination. In the first experiment (n = 15) the return of cyclic ovarian activity was monitored by determination of progesterone in milk twice weekly over a period of 10 weeks post partum. In the second experiment (n = 121) urine and milk samples were collected at intervals of 5 to 8 days over a period of 9 weeks post partum and analysed for ketone bodies. The body condition of the cows was estimated by a scoring system at 5 and 9 weeks post partum. In the third experiment (n = 289) urine samples taken 1-4 days before as well as 3 days and 5 weeks after calving were analysed for ketone bodies. Biologic reproduction data were followed up for 150 days post partum in all experiments. One to two thirds of the cows in the examined herds showed ketonuria post partum, some animals also displayed ketonuria ante partum. Persistent postpartal ketonuria occurred mainly among the older cows with a high performance that at the same time showed a marked loss of body condition during the first weeks post partum. Primiparous heifers seldom developed ketonuria, despite a generally poor body condition.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of postpartum live weight loss on reproductive functions in dairy cows

Postpartum loss of live weight in dairy cows and its association with reproductive functions were studied in a total of 84 (42 Ayrshire and 42 Friesian) cows. The cows were divided according to type of feed into 2 groups of equal size: a hay-urea group and a silage group. The duration of the study was 3 years. All 84 cows were followed during their first postpartum period, 63 during 2 and 57 during 3 consecutive postpartum periods.The resumption of ovarian function was monitored by means of a thrice weekly milk progesterone assay between calving and the first insemination.Live weight changes during the first 30 and 60 days post partum were compared between the 2 breeds and the 2 feed groups.After the second parturition, the mean live weight loss within 30 and 60 days post partum was roughly twice as high (11%) as after the first (4%) and third (6%) carvings. Breed had no significant effect on weight change. The cows in the silage group lost slightly more weight after each parturition than those in the hay-urea group. Low, but statistically significant correlations were noted between weight loss post partum and reproductive functions. The interval from calving to onset of the first visible oestrus was 6 days longer, and to pregnancy 8 days longer in cows which lost more than 10% live weight within 60 days post partum than in those which lost less than 10% (p<0.05). The fertility rate at first insemination (53.1%) was lower in cows which lost more than 10% weight than in those (74.4%) which lost less than 10% (p<0.01). Heat detection rate was not affected by weight loss.     

Relationships between body weight and milk yield during the early postpartum period and bull and technician and the reproductive performance of high producing dairy cows

The aim of this study was to evaluate the effect of body weight (BW) change during the early postpartum period and BW on day 50 post partum on the subsequent expression of estrus and fertility at first insemination before day 90 post partum. The data were derived from 1036 postpartum cows reaching 90 days in milk. The following data were recorded for each animal: lactation number, daily milk production at day 50 post partum, calving date, days in milk at estrus and at AI, insemination date, insemination number, inseminating bull, AI technician and body weight at calving, at day 50 post partum and at AI. Of the 1036 cows registered, 817 (78.9%) showed first estrus before day 90 post partum and were inseminated. Using logistic regression procedures and based on the odds ratio a one unit (kg) increase in the daily milk production at day 50 post partum and a one unit (kg) decrease in the BW between calving and day 50 post partum were related to a 1.03-fold increase and a 0.97-fold decrease in the estrus expression rate before day 90 post partum, respectively. Of the 817 cows inseminated before day 90 post partum, 437 became pregnant (53.5%). A one unit increase in the BW at day 50 post partum produced a 1.003-fold increase in the early fertility rate. Pregnancy rate before day 90 was also influenced by the season at calving, bull providing semen and technician. In conclusion, the register of BW during the postpartum period may be a useful tool for evaluating the nutritional status and its relationship with the subsequent reproductive efficiency in dairy cows.     

Effects of pre‐partum milking of dairy cows on calcium metabolism at start of milking and at calving

This experiment studied the effect of pre‐partal milk removal on calcium metabolism at start of milking and at calving. Nine cows of the Swedish Red breed were milked for 1–7 days pre‐partum. The average milk yield at the first milking was 4.8 l, and the average yield the last day prior to calving was 13.4 l. Five cows were used as control cows and were only milked post‐partum. Samples of plasma and urine were taken to determine the effect of pre‐partum milking and calving on levels of calcium, magnesium, parathyroid hormone and plasma C‐terminal crosslinked telopeptide of type 1‐collagen (CTx), used as a marker of bone resorption. Pre‐partum milking resulted in a decrease in plasma calcium that was evident 2 days after the first milking. Parathyroid hormone increased at the same time, and CTx started to increase from 24 h after the first milking. There were no effects on plasma magnesium or urinary output of calcium or magnesium. The first week after calving, there were no differences between pre‐partum milked cows and control cows in plasma or urine variables, or in milk yield. In conclusion, pre‐partum milking activated the calcium‐restoring mechanisms but did not improve calcium status at calving.     

OC10A Negative Energy Balance but not Suckling Frequency (ad libitum,Twice or Once Daily) Modules Ovarian Resumption in Parda de Montaña Cattle Breed

In extensive systems, beef cows should be continuously with their calves to optimise pasture use but this practice can lengthen post‐partum interval (PPI). A study was conducted to determine the influence of suckling frequency on Parda de Montaña cow‐calf performance when cows are fed 70% energy requirements during lactation (outdoor winter conditions simulation). Thirty‐six autumn‐calving cows with similar body condition at calving (2.57) were assigned to three suckling systems [ad libitum (AL), twice (2D) or once daily (1D) for 30 min]. Blood samples were collected twice a week to analyse progesterone concentrations by RIA. Cows lost similar weight until start of mating period (day 52 post‐partum; ?0.583, –0.513, –0.520 kg/day in AL, 2D and 1D). Standard milk yield was higher in AL than the rest (8.9, 6.2, 7.0 kg; p < 0.05), which was reflected on greater calf gain (0.895, 0.752, 0.676 kg/day; p < 0.05) and larger cow weight loss within 90 days post‐partum in this treatment (–0.345, –0.188, –0.083 kg/day; p < 0.05). Suckling system did not affect either PPI (69.6, 89.1, 65.5 days) or cows cycling within 90 days post‐partum (55, 46, 58%), which may compromise the target calving interval. In Parda de Montaña breed fed moderately pre‐calving and undernourished during lactation, restricted suckling did not favour ovarian activity resumption, but post‐partum subnutrition delayed about 40 days PPI observed in similar body condition at calving and calf management (Sanz et al., 2003; Anim Reprod Sci 79: 57–69)     

Post-partum, ovarian function in dairy cows as revealed by concentrations of oestradiol-17 beta and progesterone in defatted milk

Concentrations of oestradiol-17 beta and progesterone in defatted milk have been used to study the post-partum restoration of ovarian function in 52 autumn-calved dairy cattle. In 32 cows the first preovulatory peaks in oestradiol-17 beta concentration (indicative of imminent ovulation) were less than or equal to 15 days and in 49 cows less than or equal to 49 days post partum. Delay to first ovulation was mainly due, not to failure of ovarian secretion of oestradiol-17 beta at preovulatory level, but to failure of oestradiol-17 beta at this level to exert its normal preovulatory function. Longer intervals to first ovulation were associated with longer intervals from calving to the clearance of placental oestradiol-17 beta, high peak milk yields and high body weight losses, suggesting that in high-yielding dairy cows these factors (themselves inter-related) may be associated with others, which are the immediate cause of the inhibition of the normal, preovulatory function of oestradiol-17 beta. Forty-eight per cent of cows had short, first ovulation cycles. Ovarian function, comprising oestradiol-17 beta secretion at preovulatory level, normal preovulatory function of oestradiol-17 beta and normal corpus luteum progesterone secretion were almost fully restored in this herd by the 49th day post partum.     

The relationships among palpator experience, milk progesterone concentration and estrus and fertility in cows with palpable corpora lutea treated with cloprostenol

Two hundred and fifty-one cows fresh at least 37 days with normal reproductive tracts and palpable ovarian structures which clinicians believed to be corpora lutea and which were presumed to be producing progesterone were treated with 500 micrograms of cloprostenol. The cows were stratified into three groups based on milk progesterone concentrations in whole milk samples taken at the time of examination. The low group had milk progesterone concentrations less than or equal to 1 ng/ml, the intermediate group had milk progesterone concentrations between 1 and 3 ng/ml, and the high group had milk progesterone concentrations greater than or equal to 3 ng/ml. The proportion of cows in each group inseminated within 5 days of treatment and the fertility at that breeding were compared. There were no significant differences among the groups with respect to the proportion of cows that came into estrus within 5 days. However, the conception rate of the high group (54%) was significantly greater than that of the intermediate group (26%). To study the relationship between practitioner experience and diagnostic accuracy the proportion of cows with low, intermediate and high concentrations of progesterone selected by clinicians with more than 3 years experience was compared to that for clinicians with 3 years of experience or less. Less experienced clinicians were significantly more likely to make a false positive diagnosis of functional luteal tissue in cows with palpable ovarian structures than were more experienced clinicians.     

Husbandry Factors and the Resumption of Luteal Activity in Open and Zero‐Grazed Dairy Cows in Urban and Peri‐Urban Kampala,Uganda

The study investigated the influence of selected husbandry factors on interval to resumption of post‐partum cyclicity among dairy cows in urban and peri‐urban Kampala. A prospective study of 85 day post‐partum period of 59 dairy cows in open (n = 38) and zero grazing (n = 21) systems was conducted on 24 farms. Cows of parity 1–6 were recruited starting 15–30 days post‐partum. Progesterone (P4) content in milk taken at 10–12 day intervals was analysed using ELISA. The cow P4 profiles were classified into ‘normal’ (< 56 days), ‘delayed’ (> 56 days), ‘ceased’ or ‘prolonged’ (if started < 56 days but with abnormal P4 displays) resumption of luteal activity and tested for association with husbandry and cow factors. Of the 59 cows, luteal activity in 81.4% resumed normally and in 18.6%, delayed. Only 23.7% maintained regular luteal activity, while the others had ceased (10.2%), prolonged (37.3%) or unclear luteal activity (20.3%). There were no differences between open and zero‐grazed cows. Milk production was higher (p < 0.05) in zero than open grazing, in urban than peri‐urban and in cows fed on brew waste (p < 0.001) compared with mill products and banana peels. Results suggest that luteal activity resumes normally in a majority of cows, although only a minority experienced continued normal cyclicity once ovulation had occurred, in the two farming systems irrespective of feed supplements or water, and that supplementing with brew waste is beneficial for milk production.     

Radioimmunoassay of milk progesterone as a tool for fertility control in smallholder dairy farms

This study focused on the use of radioimmunoassay of progesterone in milk for the diagnosis of post-partum ovarian cyclicity and accurate detection of oestrus and non-pregnancy in cows in the artificial insemination (AI) programme in Bangladesh. In Investigation 1, milk samples were collected on day 0 (day of AI), day 9–13 and day 21–24 from 444 milking cows of various breeds presented for the first post-partum insemination by 413 farmers living at 182 villages/regions in Mymensingh District from 6 AI centres and sub-centres. Each cow was then examined three times after each AI until it stopped returning to oestrus. Sixty to 90 days after the last AI, the cows were examined per rectum to confirm the pregnancy. Milk progesterone data on day 21–24 contributed to a clear diagnosis with respect to non-pregnancy in 100% cows, indicating a possible use of this progesterone assay for identifying non-pregnant cows in AI programmes. In Investigation 2, milk progesterone was monitored two times in a month with a 10-day interval in 88 cows. The samples were taken between 10 days after calving and the first detected oestrus, followed by two more samples 10 days apart. The proportion of cows accurately detected in oestrus was 30%. Another 30% were stated to be in oestrus when they were not (false positive) and 40% were not detected when they were in oestrus (false negative). The mean intervals between calving and oestrus and between calving luteal activity were 40 to 362 days (median = 120, n = 82) and 34 to 398 (median = 111, n = 64) days, respectively. The body condition scores at calving and at the initiation of luteal activity influenced the interval between calving and luteal activity (p < 0.05). Cows suckled twice daily initiated luteal activity earlier than their counterparts suckled several times daily (p < 0.05). Determination of progesterone in milk on day 21–24 is a good means for detecting non-pregnant cows.     

A survey of the postpartum reproductive performance of dairy cows with fertility problems in southern Iceland

The purpose of this survey was to evaluate the reproductive performance of dairy cows on problem farms in southern Iceland. In all 229 cows on 6 farms were studied. The animals were examined clinically by rectal palpation, once a month. Blood samples were taken 2–5 and 7–10 weeks after calving. The blood samples were analysed for the contents of glucose, urea, inorganic phosphate, calcium and magnesium. Milk samples for progesterone profiles were taken, by the farmer, every 4th day from day 10 postpartum until first oestrus. Because of this sampling method, 128 cows had no rise in progesterone levels, when milk sampling was stopped. These 128 animals were excluded from the study. The results are based on 101 animals.There was a large variation between cows in postpartum reproductive performance. In the total material 1st ovulation occurred later than reported in many other countries. Fifty percent of the cows had ovulated 35 days after calving and 90 percent 70 days after calving.The first luteal phase was short in about 60 % of the cows. The progesterone values assayed from those short cycles were lower than the values assayed from the following cycle. First artificial insemination (ai) was on the average 77 days postpartum (pp). The conception rate to first service was 49 %. Of 100 milk samples taken at the time of ai, 20 had high progesterone value. This indicates a high frequency of luteal phase inseminations.Clinical ketosis was diagnosed in 35 cows. Of these, 31 had a low glucose value. Cows with clinical ketosis ovulated, on the average, later than other animals and 24 ovulated later than 40 days pp. The results indicated that the fertility problems of these cows studied were late ovulations, low conception rate, probably in part, due to luteal phase inseminations, and a high frequency of ketosis which could be caused by low quality feedstuff.     

Plasma hormone changes in cows during induced or spontaneous calvings and the early post partum period

Plasma progesterone, oestradiol, 13,14-dihydro, 15-keto, prostaglandin F2 alpha (PGFM) and luteinising hormone were measured in daily samples from eight dairy cows for 15 days before and after spontaneous calving, and compared to patterns obtained from 15 cows during and after induction of parturition with dexamethasone +/- prostaglandin. The average (+/- sd) length of pregnancy in the control cows was 285 +/- 3.04 days compared to 264 +/- 7.4 days in the induced group. Only nine cows required prostaglandin on day 11 after dexamethasone, which resulted in all nine calving 1.7 +/- 0.3 days later. Eight of the 15 treated cows retained the fetal membranes; however, the calving to first heat interval for all treated cows was 46.7 +/- 10 days (range 30 to 66 days) and calving to conception 52.4 +/- 17 days (range 30 to 85 days) compared to 42.1 +/- 15 days (range 28 to 64 days) and 76.5 +/- 24 days (range 54 to 115 days) respectively for the eight cows which calved without induction. The pre-partum hormone profiles were similar in all cows. Hormone profiles in the post partum period were also similar in all cows, irrespective of previous history. Baseline values for progesterone and oestradiol were not reached until 4.6 +/- 1.7 days and 2.75 +/- 0.7 days post partum respectively, whereas PGFM values increased for two or three days, reaching baseline levels 8.87 +/- 2.10 days later. Five cows had secondary peaks of PGFM on days 5,6 and 7. Luteinising hormone values increased steadily after calving in all cows.(ABSTRACT TRUNCATED AT 250 WORDS)     

Postpartum reproductive function in Finnish Ayrshire and Friesian cows after three subsequent parturitions

The postpartum reproduction functions of 84 Finnish Ayrshire and Friesian cows were studied on an experimental farm. The cows were divided according to type of feed into 2 groups of equal size: a hay-urea group and a silage group. The duration of the study was 3 years. Eighty-four cows were followed during their first postpartum period, 63 during 2 and 57 during 3 consecutive post partum periods.The cows were examined clinically by rectal palpation, and milk samples for progesterone assay were taken 3 times a week between calving and first insemination. External signs of heat were checked 3 times a day by the herdsmen.Intervals from calving to completed uterine and cervical involution, appearance of first palpable follicle, onset of first luteal function and onset of regular ovarian function were recorded. Intervals from calving to the first observed heat and to pregnancy were measured and the rate of successful pregnancies at the first insemination was calculated.Least squares methods were used for evaluation of the effect of individual cow, breed, parity/year and type of feed on postpartum reproductive function.The cows in the herd seemed to have equal reproductive functions which were influenced by the conditions during each year/parity rather than by the breed or type of feed.Individual cow effect was significant for the rapidity of uterine involution. Breed had no significant effect on any of the parameters studied.The effect of type of feed alone was not significant for any parameter, but when studying the intervals from calving to uterine involution and initiation of luteal function differences between the feed groups were noted within parity/year.The percentage of cows showing heat before the first dioestrus (luteal phase) increased with parity/year, and the first dioestrus was shorter than the second. The percentage of cows showing postoestrous bleeding increased with number of oestrous cycles post partum.     

Combined GnRH and PGF2α Application in Cows with Endometritis Puerperalis Treated with Antibiotics

The investigations were carried out on a total of 70 cows with puerperal endometritis. In addition to intrauterine antibiotic treatment, 30 experimental animals were administered 20 μg GnRH analogue, buserelin, between days 10 and 12 post‐partum followed by 500 μg PGF_2α analogue, cloprostenol, 10 days later. Forty control cows were treated only with intrauterine antibiotics. Blood samples for progesterone determination were collected from the tail vein twice weekly until day 70 post‐partum. The first rise in progesterone level above 3.18 nmol/l occurred significantly earlier in the experimental than in control cows (21.6 ± 9.2 versus 27.8 ± 12.3 days; p ≤ 0.05). The duration of the first cycle post‐partum was 15.0 ± 4.3 days in experimental and 19.7 ± 7.3 days in control animals (p ≤ 0.05). However, no significant differences were observed in the occurrence of first oestrus post‐partum. The involution of the uterus was improved after hormone treatment. At day 42 post‐partum, completion of uterine involution was found in 93.3% of hormone‐treated cows and in 82.5% of those treated with antibiotic only (p ≤ 0.05). Clinical recovery was 96.6% in the experimental and 82.5% in the control group (p ≤ 0.05). First service pregnancy rate was significantly better in hormone‐treated than control cows (51.7 versus 36.4%; p ≤ 0.05). Total pregnancy rate and insemination index values were not significantly improved following GnRH and PGF_2α treatment. The average service period was 89.8 ± 21.2 days in cows after hormone treatment, and 112.6 ± 24.5 days in control cows. The difference was statistically significant (p ≤ 0.05). These results indicate, that the sequential GnRH and PGF_2α application in cows with puerperal endometritis positively affected ovarian function and uterine involution, resulting in improved fertility performance.     

Pregnancy Loss in Dairy Cattle: Relationship of Ultrasound,Blood Pregnancy‐Specific Protein B,Progesterone and Production Variables

Objectives were to determine associations between percentage pregnancy loss (PPL) in dairy cattle and: (i) pregnancy diagnosis by ultrasonography; (ii) pregnancy diagnosis by serum pregnancy‐specific protein B (PSPB) concentrations, with or without serum progesterone concentrations; and (iii) production and environmental factors. This study included 149 822 pregnancy diagnoses conducted over 13 years in Holstein‐Friesian cows in Hungarian dairy herds. The following were determined: PPL in cows diagnosed pregnant by transrectal ultrasonography 29–42 days after artificial insemination (AI; n = 11 457); PPL in cows diagnosed pregnant by serum PSPB 29–35 days after AI (n = 138 365); and PPL and its association with serum progesterone concentrations, PSPB and production/environmental variables. The definition of PPL was percentage of cows initially diagnosed pregnant based on ultrasonography or PSPB, but not pregnant when examined by transrectal palpation 60 –70 days after AI. The PPL was lower (p < 0.001) in cows following ultrasonographic vs PSPB diagnosis of pregnancy at 29–35 days (8.1 vs 19.3%, respectively), but was higher in cows following ultrasonographic pregnancy diagnosis on 29–35 vs 36–42 days (8.1 vs 7.1%, respectively, P < 0.05). Furthermore, 72.9% of pregnancies with ultrasound‐detected morphological abnormalities resulted in pregnancy loss. As a subset of PSPB data, a fully quantitative PSPB assay was used for 20 430 samples; PPL in cows with a high PSPB concentration (>1.1 ng/ml) was lowest (15.0%), whereas cows with low concentrations of both PSPB and progesterone (0.6–1.1 and <2 ng/ml, respectively) had the highest PPL (76.3%; p < 0.0001). Furthermore, PPL was higher in cows with advanced parity and with high milk production, when ambient temperatures were high, although body condition score (BCS) had no effect on PPL. Finally, there were no significant associations between serum PSPB and environmental temperatures or number of post‐partum uterine treatments.     

Serum progesterone levels in post-partum dairy cows after repeated application of the prostaglandin F2 alpha analogue D (+) cloprostenol sodium

Reproductive management programmes based on strategic use of prostaglandin F2 alpha (PGF2 alpha) to induce and synchronize oestrus in post-partum dairy cows are widespread. Repeated shortening of the oestrous cycle during early lactation in high-yielding dairy cows, however, could impair corpus luteum function and thus decrease fertility. The objective of this study was to analyse the effect of repeated treatments with the prostaglandin F2 alpha analogue D (+) cloprostenol sodium on progesterone concentrations indicative of a functional corpus luteum in post-partum dairy cows. Furthermore, the influence of milk production, parity and endometritis on progesterone concentrations under these circumstances were studied. Eighty-four cows of a commercial dairy operation were treated three to four times with D (+) cloprostenol sodium (Preloban; Hoechst Roussel Vet, Wiesbaden, Germany) at 14-day intervals, starting 22-28 days post-partum. Blood samples were collected prior to treatment 1 (sample 1) and 14 days after treatments 1, 2 and 3 (samples 2-4) and serum progesterone (P4) levels were determined. The percentage of cows with P4 levels < 1 ng/ml decreased from 51% in sample 1 to 23% in samples 3 and 4. More primiparous cows had low P4 levels 14 days after the second treatment than older cows (P < 0.05). Cows with low progesterone levels in sample 3 or 4 had lower protein contents in milk on the second milk test day post-partum and in their cumulative milk yield of the first 100 days of lactation. Clinical endometritis at post-partum examination did not influence progesterone levels after treatment with PGF2 alpha. Repeated application of PGF2 alpha (more than twice) in the post-partum period does not influence serum progesterone levels 14 days after treatment. Failure to develop luteal tissue after treatment contributed to the conception failures after first service.     

Udder health and risk factors for subclinical mastitis in organic dairy farms in Switzerland

A study was performed in 1997 to estimate the prevalence and to investigate the etiology of subclinical mastitis in Swiss dairy herds managed under guidelines of controlled organic farming. It was planned as a longitudinal study over a period of 1 year and included a stratified random sample of 152 certified organic farms and 1907 cows. Two farm visits (the first from June to October when cows were on pasture, the second from January to March when cows were confined to barns) were performed on each farm. At each visit, farm management and individual-cow data (with emphasis on milking procedures and udder sanitation) were recorded. California mastitis tests (CMTs) were performed on each udder quarter of all cows in lactation. Milk samples with CMT >1+ were submitted for somatic cell counting (SCC), bacteriological examination and to test for antibiotic susceptibility. The SCC and germ-cell counts of monthly bulk-tank milk samples were available through Dairy Inspection and Advisory Services and milk production data of 567 herd-book cows were available from breeding associations. Possible individual and environmental predictors of subclinical mastitis were identified using logistic models adjusted for clustering of the data at herd and cow levels. Data were analyzed separately for cows from 7 to 100 and from 101 to 305 days post partum. Prevalences of subclinical mastitis at the quarter level were 21.2% for lactation period 7–100 days and 34.5% for 101–305 days post partum. The geometric mean SCC in bulk-tank milk samples was 85.6×10³ cells/ml. Samples at 7–100 and 101–305 days post partum were positive for Staphylococcus aureus in 16.0 and 7.4%, for coagulase-negative Staphylococci in 51.5 and 50.6%, for Streptococcus agalactiae in 0.0 and 0.8%, for other Streptococci in 19.4 and 15.6%, for E. coli in 1.0 and 0.4%, and for Corynebacterium bovis in 25.7 and 45.1%, respectively. Risks of subclinical mastitis increased significantly with increasing days post partum and advancing age of cow. Cows that were sampled when staying in alpine dairies had considerably higher risks of subclinical mastitis than cows staying in home barns. Significantly lower risks of subclinical mastitis were observed in farms where CMT was performed regularly as a control measure. Bacteria in milk from cows with mastitis exhibited antibiotic resistance at a comparable frequency as found previously in conventional farms.     

Concentrations of ketones in milk in early lactation, and reproductive performance of dairy cows

Samples of blood and milk were taken from clinically ketotic cows at 12-hour intervals before and after treatment The concentration of beta-hydroxybutyrate was determined in plasma and milk, and the concentration of acetone was determined in milk. Measurement of milk acetone had the optimal combination of sensitivity, specificity and positive predictive value to identify ketotic cows and was subsequently used in a comparison of the fertility of ketotic and normal cows. Two samples of milk were taken approximately two weeks apart, between 12 and 60 days after calving, from 410 cows on three farms and the concentration of acetone in the milk was measured. Thirty cows with milk acetone concentrations of at least 0.4 mmol/litre were compared with paired control cows with milk acetone concentrations less than 0.3 mmol/litre. The ketotic cows had a significantly longer calving-to-conception interval and a significantly higher culling rate due to a failure to conceive (P<0.05).     

Changes in some blood parameters,milk composition and yield of buffaloes (Bubalus bubalis) during the transition period

In this study changes in hematochemical parameters, milk composition and yield were investigated in buffaloes during the transition period. A total of 93 buffaloes 113.9 ± 8.03 months old and 535 ± 50 kg average body weight were used. Parity was recorded, blood samples were collected from 80 days pre‐partum until 70 days post‐partum; milk samples were collected from 5 days to 70 days post‐partum. On serum samples, the values of non‐esterified fatty acids, β‐hydroxybutyrate, glucose, cholesterol, triglycerides, aspartate aminotransferase, alanine aminotransferase, gamma‐glutamyltransferase, urea, total proteins were evaluated. On milk, percentage of fat, protein and lactose, along with the somatic cell count (SCC), milk yield and daily milk production (DMP) were assessed. The peripartum period significantly (P ≤ 0.01) influenced all studied parameters with the exception of glucose. Milk fat percentage showed decreasing trend from 10 until 40 days post‐partum; DMP significantly (P ≤ 0.01) increased from 1 day post‐partum until 40 days post‐partum. Milk yield significantly (P ≤ 0.01) decreased in animals over the sixth lactation. Our results confirmed the importance of transit period in buffaloes. Blood parameters and milk composition alterations are crucial to predict the energy balance status of buffaloes in order to improve their management and feed intake during the transition period.     

Milk Progesterone Profile at and after Artificial Insemination in Repeat-Breeding Cows: Effects on Conception Rate and Embryonic Death

The aim of this study was to investigate whether the skim milk progesterone concentrations at artificial insemination (AI) and day of rise of post-ovulatory progesterone concentration thereafter affect the conception and embryonic death rates in repeat-breeding cows. Milk samples were obtained from 96 repeat-breeding cows that failed to conceive to three or more AIs. The samples were taken from the cows at the day of AI and three times/week until day 45 post-AI. Skim milk was obtained after centrifugation and used for progesterone assay. The cows with a progesterone concentration more than 0.5 ng/ml at AI showed a significantly higher incidence of late embryonic death than those having a progesterone concentration<0.5 ng/ml at AI (p<0.01). As the progesterone level at insemination rose, conception rate declined. A negative correlation was shown between conception rate and skim milk progesterone level at AI. Of 56 cows showing a rise of progesterone to 1 ng/ml or more within 6 days after AI, 28 cows (50%) conceived. On the contrary, only eight of 39 cows (20.5%) conceived when the progesterone rose up to 1 ng/ml after day 6 post-AI. We concluded that increased progesterone concentration at the time of AI and delayed rise of progesterone post-AI might lead to decrease in fertility in repeat-breeding cows.