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)     

Hormonal interrelationships in postpartum suckled dairy cows.

Three cross-bred cows calved in March and April and were followed until day 62 after parturition. Each animal was suckled by 2 calves ad libitum. All calves were removed from the cows on day 55 after parturition. Blood was collected 3 times per day from the jugular vein by venipuncture. On 4 occasions after parturition--i.e. days 7-8, 21-22, 35-36 and 49-50, the cows were bled through a jugular venous catheter every 30 min during the 24 h. The plasma samples were analyzed for the content of 15-keto-13,14-dihydro-PGF2 alpha (main PGF2 alpha metabolite), LH, prolactin, cortisol and progesterone by radioimmunoassay methods. The concentration of PGF2 alpha increased from 280 to 730 pmol/l within the last 4 days before parturition. The highest geometric mean was 3106 pmol/l on the day of parturition. Thereafter a steady decrease of PGF2 alpha metabolite concentration was seen until day 21 when it reached plateau at 148 pmol/l. In all cows plasma LH concentrations increased significantly (P < 0.05) from about 1.6 micrograms/l on days 7-8 to 2.4 micrograms/l on days 21-22 post partum. The frequency of LH pulses showed no tendency to increase as the postpartum period progressed and averaged 6.5 pulses/24 h. Mean plasma LH concentrations increased from 2.1 micrograms/l 2 days before weaning to 3.2 micrograms/l 2 days after weaning (P < 0.05). LH peaks occurred less frequently in association with prolactin and cortisol peaks than in their absence. A partial positive correlation between PGF2 alpha metabolite and cortisol (r = 0.30) was found on days 7-8 post partum. Correlation between prolactin and cortisol on days 7-8 and 21-22 post partum was also positive (r = 0.20 and r = 0.27, respectively). There was a negative correlation between LH and cortisol on days 7-8 (r = -0.27) and days 49-50 (r = -0.21) post partum. The first and short progesterone increase observed after weaning was terminated in conjunction with PGF2 alpha metabolite peaks.     

Lack of LH response to oestradiol treatment in cows with cystic ovarian disease and effect of progesterone treatment or manual rupture.

The luteinising hormone (LH) surge in response to 1 mg oestradiol benzoate intramuscular injection was studied on 67 occasions in 45 cows with cystic ovarian disease 20 to 150 days post partum. Cows diagnosed as having luteal cysts were given 500 micrograms cloprostenol intramuscularly 24 hours before oestradiol, to induce luteolysis. Oestradiol benzoate was also given to eight post partum acyclic and eight cyclic cows and in all these cases a control LH response was characterised for comparison. Eight of 17 cows with luteal cysts (47 per cent), and 10 of 21 cows with follicular cysts (48 per cent), released LH in response to oestradiol. Some cows with cysts were given one of two treatments. Seven cows with follicular cysts were treated with a progesterone-releasing device (PRID) for seven days: all responded to a second oestradiol treatment given 24 hours after removal of the PRID. Luteal cysts in three cows and follicular cysts in nine cows were ruptured manually: only one cow (a luteal case) responded to the second oestradiol treatment given 24 hours after manual rupture. In eight cows initially diagnosed with luteal cysts, cloprostenol was not given and plasma progesterone concentration at the time of oestradiol treatment was high (over 0.9 ng ml-1): none released LH in response to oestradiol. As manual rupture did not improve the LH response to oestradiol, it is concluded that the defective LH response to oestradiol in cows with cystic ovarian disease was not influenced in the short-term by cyst fluid contents.(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.     

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.     

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)     

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.     

Body condition and frequency of ovarian cysts in Brown Swiss cows during the first 40 days of lactation

For this investigation 50 Brown Swiss cows from 21 different farms were used. Twenty-five peripartal overconditioned cows (back fat thickness > 38 mm) were compared with 25 peripartal not overconditioned animals (back fat thickness < 38 mm). On days 20, 30 and 40 post partum the ovaries were examined sonographically and 10, 15, 20, 30 and 40 days after calving plasma concentrations of progesterone and 17-beta estradiol were determined. In peripartal overconditioned animals 12 ovarian cysts were found while only one cyst was present in not overconditioned cows (P < 0.05). At first examination all ovarian cysts were classified by ultrasound as follicle theca cysts (progesterone < 0.5 ng/ml plasma). Follow examinations resulted in 3 cysts which persisted as theca cysts while 8 cysts became luteinized and 2 cysts completely regressed. There was no indication of increased plasma progesterone and/or estradiol concentrations in overconditioned cows with higher fat deposit before of ovarian cysts had occurred.     

Back fat thickness and fertility in Brown Swiss cows

In a total of 94 cows the mean back fat thickness (BFT) on Day 275 of pregnancy and 2 to 3 days after calving (peripartal) as well as between Days 42 and 44 post partum (postpuerperal) has been examined sonographically. Based on their BFT levels all examined cows have been divided into three groups: overconditioned, optimal conditioned and underconditioned cows. Cows which were peripartal overconditioned had more often ovarian cysts (p < 0.05) and were culled more frequently (p < 0.1) because of infertility than peripartal cows which were optimal or underconditioned. Nevertheless, the interval from calving to conception of peripartal cows being in different physical conditions was not significantly different. Postpuerperal cows which were overconditioned had more often ovarian cysts (p < 0.05) and were more frequently (p < 0.05) slaughtered because of infertility than postpuerperal cows which were optimal or underconditioned. Postpuerperal cows which were over- or underconditioned had a significantly longer interval from calving to conception than cows which were optimal conditioned 6 weeks after calving. The correlation coefficient between peripartal and postpuerperal BFT was 0.82 (p < 0.05). The decrease of BFT between the peripartal and postpuerperal timepoint had no significant influence on the frequency of ovarian cysts, the interval from calving to conception and the infertility caused culling rate.     

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)     

Energy balance,leptin, NEFA and IGF-I plasma concentrations and resumption of post partum ovarian activity in swedish red and white breed cows

In the purpose to provide further information in respect of the relationship between metabolism and post partum (PP) ovarian activity resumption in dairy cows, the aim of the present study was to characterize the energy balance (EB) and leptin, NEFA and IGF-I plasma levels in Swedish Red and White (SRW) cows with and without ovarian activity re-initiation within 7 weeks PP. The study was conducted on 12 primiparous SRW cows fed the same diet as total mixed ration for ad libitum intake. The EB was calculated weekly from parturition until seven weeks PP. Blood samples were collected weekly from one week before until 7 weeks after calving for leptin, NEFA and IGF-I analysis. For progesterone (P4) analysis, blood samples were collected two times per week from parturition until the end of the study. P4 profile was used in addition to the clinical examination to detect cows with and without ovarian activity resumption. The clinical and ultrasonographic examination, coupled with P4 profile analysis showed the resumption of ovarian activity within 7 weeks after calving in 8 (group A) and no ovarian resumption in 4 cows (group B). No significant differences were detected in the whole period of observation in the amount of milk production between the two groups, while the mean milk protein content was significantly lower in group B at the third week PP. The calculated EB was negative in both groups in the first three weeks after calving, but more marked in group B. NEFA and Leptin plasma levels did not show significant differences between the two groups. In conclusion, the results of the present study showed that, when low milk producing primiparous cows are concerned, no significant differences in BW loss, milk yield, EB and leptin and NEFA plasma levels between the cows with and without resumption of ovarian activity within 7 weeks post partum were seen. However, significantly higher IGF-I levels in the first two weeks after calving were found in cows with post partum ovarian activity resumption, highlighting the important role of IGF-I as sensitive signal between metabolism and reproduction.     

Pre‐ and Post‐Partum Mild Underfeeding Influences Gene Expression in the Reproductive Tract of Cyclic Dairy Cows

Undernutrition before and after calving has a detrimental effect on the fertility of dairy cows. The effect of nutritional stress was previously reported to influence gene expression in key tissues for metabolic health and reproduction such as the liver and the genital tract early after calving, but not at breeding, that is, between 70 and 90 days post‐partum. This study investigated the effects of pre‐ and post‐partum mild underfeeding on global gene expression in the oviduct, endometrium and corpus luteum of eight multiparous Holstein cows during the early and middle phases of an induced cycle 80 days post‐partum. Four control cows received 100% of energy and protein requirements during the dry period and after calving, while four underfed received 80% of control diet. Oestrous synchronization treatment was used to induce ovulation on D80 post‐partum. Oviducts, ovaries and the anterior part of each uterine horn were recovered surgically 4, 8, 12 and 15 days after ovulation. Corpora lutea were dissected from the ovaries, and the endometrium was separated from the stroma and myometrium in each uterine horn. The oviduct segments were comprised of ampulla and isthmus. RNAs from ipsi‐ and contralateral samples were pooled on an equal weight basis. In each tissue, gene expression was assessed on a custom bovine 10K array. No differentially expressed gene (DEG) in the corpus luteum was identified between underfed and control, conversely to 293 DEGs in the oviduct vs 1 in the endometrium under a false discovery rate (FDR) < 0.10 and 1370 DEGs vs 3, respectively, under FDR < 0.15. Additionally, we used dedicated statistics (regularized canonical correlation analysis) to correlate the post‐partum patterns of six plasma metabolites and hormones related to energy metabolism measured weekly between calving and D80 with gene expression. High correlations were observed between post‐partum patterns of IGF‐1, insulin, β‐hydroxybutyrate and the expression in the oviduct of genes related to reproductive system disease, connective tissue disorders and metabolic disease. Moreover, we found special interest in the literature to retinoic acid‐related genes (e.g. FABP5/CRABP2) that might indicate abnormalities in post‐partum tissue repair mechanisms. In conclusion, this experiment highlights relationships between underfeeding and gene expression in the oviduct and endometrium after ovulation in cyclic Holstein cows. This might help to explain the effect of mild undernutrition on fertilization failure and early embryonic mortality in post‐partum dairy cows.     

Effects of body condition and estradiol on luteinizing hormone secretion in post-partum beef cows

An experiment was conducted to test the hypothesis that the effect of body fatness on LH pulsatility in post-partum cows is entirely independent of the negative feedback effects of ovarian steroids. Forty beef cows were fed in the last 100 d of gestation so that they achieved either a thin (mean score 1.97) or fat (mean score 2.79) body condition (0 to 5 scale) at calving and were fed after calving to maintain live weight and body condition. At 15 (sd 3.7) d post partum all cows were ovariectomised and half from each body condition score treatment group received a subcutaneous estradiol implant (+EST) while the remainder received no implant (−EST). At weeks 5 and 9 post-partum blood samples were collected via jugular catheter every 20 minutes for 10 hr on two consecutive d and on the third d cows were injected via the jugular vein with 2.5 μg GnRH. Blood samples were collected every 15 minutes for 1 hr before and 2 hr after GnRH injection. At 5 and 9 weeks the fatter cows had significantly higher mean LH concentrations, baseline LH concentrations, LH pulse amplitudes and pulse frequencies (P<0.01). Implantation with estradiol in both fat and thin cows reduced mean LH concentrations, baseline LH concentrations, LH pulse amplitudes and pulse frequencies (P<0.001). The lack of interaction between body condition and the presence or absence of estradiol implies that the effect of body condition on LH release is independent of ovarian steroid feedback mechanisms. Fat cows showed a greater release of LH in response to exogenous GnRH (P<0.01) than thin cows while implantation with estradiol in both fat and thin cows decreased (P<0.01) LH release. The pituitary responsiveness to GnRH with the −EST cows was greater at 9 compared to 5 weeks, but there was no difference with time in the +EST cows. However, there was no such interaction in endogenous LH pulse amplitude suggesting that in the absence of estradiol the magnitude of GnRH pulses declined with time post-partum.     

Relationship between milk somatic cell count and postpartum ovarian cyclicity and fertility in dairy cows

The main objective of the study was to describe the relationship of high somatic cell count (SCC) with the incidence of abnormal postpartum resumption of ovarian cyclicity and reproductive performance in dairy cows. The factors influencing SCC were also investigated. Four hundred and forty-seven cows from six dairy herds in Japan were monitored for SCC and postpartum resumption of ovarian cyclicity. Cows with high SCC (200,000 to 500,000) had a higher incidence of prolonged luteal phase (P < 0.01) than cows with an SCC of 50,000 to 100,000. The high SCC cows (> 500,000) also showed a higher incidence of delayed first ovulation post partum than cows with an SCC ≤500,000 (P < 0.05) during the first month post partum. Cows with an SCC of 200,000 to 500,000 showed lower conception and pregnancy rates, and more days from calving to conception than cows with an SCC of less than 200,000 (P < 0.05). Cows in parity 5 or more had a higher incidence of high SCC than cows in the first and second parities (P < 0.05). It is concluded that cows with a high SCC have a higher incidence of abnormal postpartum resumption of ovarian cyclicity, leading to reduced reproductive performance.     

Increased conception rate in dairy cows after early post partum administration of prostaglandin F2 alpha THAM

Commercial dairy cows were given a routine injection of dinoprost tromethamine (prostaglandin F2 alpha THAM) in the early post partum period. The first service conception rate of 64 cows given a single 25 mg injection of dinoprost during the period 14 to 28 days after calving was 68 per cent, that of 64 untreated controls was 43 per cent. The difference was highly significant at the level P = 0.007. In cows with no blood progesterone and with basal progesterone concentrations at the time of treatment, indicating absence of an active corpus luteum, the mean conception rates for 30 treated and 38 control cows were 70 and 44 per cent, respectively, demonstrating that this is not a luteolytic effect. Although that implies a positive myometrial effect, the interval from calving to first service was not shortened in treated cows.     

Effect of supplementation of vitamin E,copper and zinc on the in vitro phagocytic activity and lymphocyte proliferation index of peripartum Sahiwal (Bos indicus) cows

To study the effect of vitamin E (VE), copper (Cu) and zinc (Zn) supplementation on the in vitro phagocytic activity (PA) and lymphocyte proliferation response (LPR) of blood neutrophils and lymphocytes, thirty Sahiwal pregnant cows (six in each group) in their late gestation at 30 days before the expected date of calving were selected from the NDRI experimental herd and supplemented with various micronutrients from 30 days before calving to 45 days after calving. Cows were supplemented individually with VE (1000 IU/cow/day), Cu (20 ppm/cow/day) and Zn (80 ppm/cow/day) and also with a combination of VE, Cu and Zn to study cumulative effect of all micronutrients. One group without any supplementation acted as a control. Blood neutrophils and lymphocytes were isolated and studied for their PA and LPR. Supplementation of micronutrients like VE, Cu, Zn and a combination of all these nutrients significantly (p < 0.01) increased the PA of experimental cows as compared to control (unsupplemented) cows during the pre‐partum period. During post‐partum, all the micronutrients (VE, Cu, Zn and their combination) showed a significant (p < 0.01) increase in the PA of experimental cows as compared to control cows. Of all the groups, significant (p < 0.01) and maximum PA was observed in the combination group followed by Zn‐supplemented group during both the pre‐ and post‐partum period. A significant (p < 0.01) increase in LPR of B lymphocytes was observed in combination‐supplemented group during the pre‐partum period and during both the pre‐ and post‐partum period in the Cu‐supplemented group.     

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.     

Cortisol and luteinizing hormone after adrenocorticotropic hormone administration to postpartum beef cows

Cortisol and luteinizing hormone (LH) were measured in serum after the administration of adrenocorticotropic hormone (ACTH) to suckled (S) and nonsuckled (NS) beef cows. Blood was sampled on 2 consecutive days every 2 weeks for four bleeding periods starting 14 days after calving. Cows were injected with 200 IU ACTH or saline in a 2-day switchback design. Serum was collected before ACTH or saline injection and at 30-min intervals thereafter for 8 hours. Average cortisol concentrations in serum were similar in S and NS cows (6.4 +/- .6 and 6.1 +/- .8 ng/ml, respectively) after saline. Average cortisol concentrations in serum collected during an 8-hr period after ACTH on days 14, 28, 42 and 56 postpartum were 24.7 +/- 2.4, 31.8 +/- 3.5, 36.4 +/- 4.2 and 40.7 +/- .5 ng/ml, respectively, for S cows, and 31.1 +/- 2.9, 44.7 +/- 5.2, 45.0 +/- 5.7 and 46.0 +/- 5.4 ng/ml, respectively, for NS cows. Cortisol response to ACTH, measured as area under the response curve, was greater (P less than .05) in NS than in S cows. Amount of cortisol released by 200 IU ACTH was maximal by days 28 to 29 postpartum in NS cows, but the response increased gradually between days 14 to 15 and days 56 to 57 in S cows. overall, LH in serum averaged .55 +/- .08 ng/ml for S cows and .92 +/- .06 ng/ml for NS cows after saline, and .49 +/- .07 ng/ml for S cows and .94 +/- .06 ng/ml for NS cows after ACth. Although mean and peak serum LH concentrations did not differ between cows given ACTH and those given saline, the number of LH peaks and the number of cows having LH after saline. Mean serum LH concentrations were lower (P less than. 05) in S than in NS cows at 28 days postpartum. The number of LH peaks was lower (P less than .05) and the magnitude of the largest LH peak tended to be lower (P less than .06) in S cows at all sampling periods.     

Ketosis treatment and milk yield in dairy cows related to milk acetoacetate levels

Milk yield and milk acetoacetate (M-acac) were measured weekly for the first 6 weeks of lactation in 5 herds with a ketosis problem. Ketosis treatments and the corresponding ketotest score, were also recorded. The treatment rate was highest 7-16 days after calving. Most of these early cases were associated with low ketone levels in milk, whereas the treatment rate for cows with high ketone levels was highest 17-31 days after calving. Nearly half of the treated cows were low-ketone animals. They were classified as ketosis cases in the cow health card records, although probably suffering from other post partum disturbances in many instances. About 40% of the cows with high ketone levels recovered spontaneously. Reduction in milk yield associated with peak M-acac levels was transient and moderate. It was concluded that health card statistics overestimates the severity of the ketosis problem in Norway.     

The effects of a post partum injection of prostaglandin F2 alpha on return to oestrus and pregnancy rates in dairy cows

The interval from calving to conception is unnecessarily long in dairy cows. Post partum administration of prostaglandin F2 alpha can reduce the calving to conception interval, but it is not known whether this is due to advanced return to oestrus, increased oestrus intensity and/or increased pregnancy rates. In two experiments, the treatment of dairy cows with prostaglandin F2 alpha 21 days post partum reduced the interval to first oestrus and first service by about 10 days. The intensity of oestrus was not affected. Pregnancy rates to first service were increased from (on average) 60 to 80%, and the number of services/conception was reduced from 2.0 to 1.3.