Serum progesterone concentration in pyometritic and normal postpartum dairy cows

Two studies were conducted to evaluate the concentration of serum progesterone in pyometritic cows and relate it to palpation of ovarian structures per rectum . In Trial 1, serum samples from 34 pyometritic cows were assayed for progesterone. Mean serum progesterone concentrations were 6.8 +/- 0.7 ng/ml. In Trial 2, each of 54 pyometritic cows was paired with a control cow on the basis of days post partum (18-50 days). Mean concentration of progesterone was 9.7 +/- 1.0 ng/ml for the pyometritic cows and 5.7 +/- 0.8 ng/ml in control cows (P<0.005). Progesterone concentration was greater (P<0.005) in both groups of cows with palpable corpora lutea (CLs). Ninety-six percent of the pyometritic cows had palpable CLs compared to 57% of the control group. Comparing serum progesterone only in cows with a palpable CL, the mean concentration was still greater (P<0.005) in the pyometritic group (10.6 +/- 1.0 ng/ml) than the control group (6.6 +/- 1.0 ng/ml). Compatability of rectal palpation findings and concentrations of serum progesterone were 92.6% for the pyometritic group and 72.2% for the control group. Progesterone concentration increased (P<0.05) by increased days post partum in Trial 2 (n=54) but not in Trial 1 (n=23). In both Trials 1 and 2, uterine size due to pyometra increased (P<0.05) with increased days post partum. No other associations were found.     

Relationship between endogenous progesterone and follicular dynamics in lactating dairy cows with ovarian follicular cysts

Two experiments were conducted to examine circulating concentrations of progesterone (P4) in cows with ovarian follicular cysts (OFCs) and to relate differing levels of P4 to subsequent follicular events. In experiment 1, peripheral concentrations of P4 were determined in cows diagnosed with OFCs. Nonpregnant, lactating Holstein and Jersey cows (n = 32) were diagnosed as having OFCs by rectal palpation. Ovarian follicular cysts were then examined by transrectal ultrasonography to confirm the presence of OFCs (follicle diameter, >/=17 mm; absence of luteal tissue). At confirmation, a blood sample was collected for quantification of P4. The concentration of P4 at confirmation was classified as low (<0.1 ng/ml), intermediate (0.1-1.0 ng/ml), or high (1.0-2.0 ng/ml). More OFCs were associated with intermediate (66%) than with either low (28%) or high (6%) concentrations of P4. In experiment 2, the fate of follicles (diameter, >/=10 mm) that formed in the presence of an OFC was determined and related to circulating concentrations of P4 during follicular development. Follicles (n = 59) that formed in the presence of an OFC ovulated (n = 19), formed a cyst (n = 30), or underwent normal growth and regression (NGR; n = 10). Endogenous P4 in the 7-day period during follicular development was classified as low (if P4 dropped to <0.1 ng/ml for 1 day or longer), intermediate (if P4 averaged between 0.1 and 1.0 ng/ml and never dropped to <0.1 ng/ml), or high (if P4 averaged >1.0 ng/ml and never dropped to <0.1 ng/ml). In the presence of intermediate P4, 75% of observed follicles formed cysts, compared with 10% that ovulated and 15% that experienced NGR. In the presence of low P4, 53%, 41%, and 6% of follicles ovulated, formed a follicular cyst, or experienced NGR, respectively. Thus, an association between intermediate P4 and the formation of OFCs was established.     

The association between lameness,ovarian cysts and fertility in lactating dairy cows

The objective of this observational study was to evaluate the association between lameness, ovarian cysts, and fertility in lactating dairy cows. Data analysis of historical records from a 3000 Holstein farm was conducted. Sixty-five cows that became lame within 30 days postpartum were used as cases, and 130 nonlame cows served as controls. The outcome variables were incidence of ovarian cysts (OC, %), conception rate at first service (CRFS, %), overall pregnancy rate (PR, %), and calving to first service interval (CFSI, day), Incidence of OC and CRFS were analyzed by logistic regression, PR by survival analysis and CFSI by ANOVA. Lame cows had a lower CRFS (17.5% versus 42.6%) and higher incidence of OC (25.0% versus 11.1%) than controls (P0.05). There was a multicollinearity relationship between lameness and ovarian cysts. The results show that cows that became lame within the first 30 days postpartum were associated with a higher incidence of ovarian cysts, a lower likelihood of pregnancy, and lower fertility than control cows. Because this is an observational study it is not possible to conclude a cause-effect relationship.     

Profiles of LH, FSH and progesterone in postpartum dairy cows and their relationship to the commencement of cyclic functions

In 25, 3-to-13 year old, dairy cows (Braunvieh and Hoehenfleckyieh) FSH, LH and progesterone plasma profiles were determined by RIA. Blood was sampled at 6-hour intervals from parturition to 40–78 days postpartum, and the results correlated with the commencement of cyclic functions. For FSH, generally basic values were recorded, without characteristic features associating any values with the onset of cyclic ovarian activities or the occurrence of the first heat. LH profiles varied greatly between individuals with regard to the onset of elevations, regularity of patterns and peak values. The first preovulatory LH peak was recorded 17.3±9.8 days (range 4–46) postpartum. The first heat occurred on day 28.4±16 (range 6–55) postpartum, indicating that 13/23 cows ovulated without behavioral estrus, as reproductive cycles were re-established. Peak LH values increased with progressive cycles (1st peak 5.7±4.8 ng/ml; 2nd peak 11.8±8.7 ng/ml; 3rd peak 13.5±9.9 ng/ml plasma). Progesterone values also showed great variations in the profile of their first postpartum elevation. In 13/25 cows the first cycle was shortened (13.1±2.9 days), prolonged in 3 animals (34±4 days) and normal in 7 cows (20.4±1.9 days). Heat, preovulatory LH peak and progesterone profile were normal in all animals on subsequent cycles. Two animals did not start cycling.     

Risk factors for resumption of postpartum estrous cycles and embryonic survival in lactating dairy cows

The objectives of this study were to evaluate factors associated with resumption of postpartum estrous cycles and embryonic survival in lactating dairy cows. Holstein cows, 6396 from four dairy farms were evaluated to determine the relationships among parity, body condition score (BCS) at calving and at AI, season of year when cows calved, and milk yield on resumption of postpartum estrous cycles by 65 days postpartum, and all the previous variables, estrual or anestrus and AI protocol on conception rates and embryonic survival at the first postpartum insemination. Cows had their estrous cycle pre-synchronized with two PGF_2α injections given 14 days apart and were inseminated between 69 and 82 days postpartum following either an estrous or ovulation synchronization protocol initiated 12–14 days after the presynchronization. Blood was sampled and analyzed for progesterone twice, 12–14 days apart, to determine whether cows had initiated onset of estrous cycles after calving. Cows were scored for body condition in the week after calving, and again at AI, between 69 and 82 days postpartum. Pregnancy was diagnosed at 30 ± 3 and 58 ± 3 days after AI. Farm influenced all reproductive outcomes evaluated. More (P < 0.0001) multiparous than primiparous cows had initiated estrous cycles. Onset of estrous cycles was also influenced (P < 0.01) by BCS at calving and at AI, BCS change, season, and milk yield. More (P < 0.001) cows that had initiated estrous cycles than anestrous cows were pregnant at 30 and 58 days after AI, but anestrus did not affect pregnancy loss. Conception rates were also influenced (P < 0.01) by parity, BCS at calving and AI, BCS change, and season; however, milk yield and insemination protocol were not associated with conception rates at 30 and 58 days after AI. Factors that reduced conception rate on day 30 after AI also increased pregnancy loss between 30 and 58 days of gestation. Improving BCS at calving and AI, minimizing losses of BCS after calving, and hastening onset of estrous cycles early postpartum are all expected to increase conception because of enhanced embryonic survival.     

Circulating progesterone dynamics after intravaginal instillation of prostaglandin-F2α to lactating dairy cows

Our objectives were to evaluate circulating progesterone (P4) concentration dynamics and test the feasibility of inducing luteal regression after intravaginal (IVG) instillation of the PGF2α analogue dinoprost (PGF) in lactating dairy cows. In two experiments, cows were synchronized using the Ovsynch protocol to induce the formation of a corpus luteum (CL). Cows with at least one functional (P4 ≥1 ng/mL) CL ≥15 mm 7.5 days after Ovsynch remained in the studies. In experiment 1, cows (n = 31) were stratified by parity group and received 5 mL of saline IVG (SAL-IVG, n = 6), 25 mg of PGF intramuscular (IM) (PGF25-IM, n = 7), 25 mg of PGF IVG (PGF25-IVG, n = 6), 50 mg of PGF IVG (PGF50-IVG, n = 6), and 125 mg of PGF IVG (PGF125-IVG, n = 6). Experiment 2 was conducted to test the hypothesis that IVG instillation of two 25 mg doses of PGF 12 hours apart would be more effective than a 25- or 50-mg dose in a single application. Cows (n = 32) were stratified by parity and received SAL-IVG (n = 7), PGF25-IM (n = 7), PGF25-IVG (n = 6), and PGF50-IVG (n = 6) as in experiment 1, whereas another group received two IVG instillations of 25 mg of PGF 12 hours apart (PGF25-2X-IVG, n = 6). Blood was collected at −1 hour, every 6 hours from 0 hour to 24 hours, and every 12 hours up to 96 hours after treatment (trt). In experiment 1, there was an effect of trt (P < 0.01), time (P < 0.001), and an interaction between trt and time on P4 concentrations (P < 0.001). All PGF-treated groups had lower (P < 0.05) concentrations of P4 than cows in the SAL-IVG group from 12 to 96 hours after trt. Although an initial decline in P4 concentrations was induced in all PGF-treated cows, some cows in the IVG-treated groups presented a rebound in plasma P4, indicating CL recovery. More cows in the PGF25-IVG and PGF125-IVG groups than in the PGF50-IVG and PGF25-IM groups presented CL recovery, suggesting that greater doses of PGF may not necessarily improve CL regression. In experiment 2, there was an effect of trt (P < 0.001), time (P < 0.001), and an interaction between trt and time on P4 concentrations (P < 0.001). All PGF-treated groups had lower (P < 0.05) P4 than the SAL-IVG group from 12 to 96 hours after trt. Cows in the PGF25-2X-IVG group had a P4 profile that was similar to that of cows in the PGF25-IM group and the lowest P4 concentrations after treatment among the IVG-treated groups, and all cows presented complete CL regression (defined as P4 <0.4 ng/mL). We conclude that CL regression can be induced through IVG instillation of PGF in lactating dairy cows and that instillation of two IVG doses of 25 mg of PGF 12 hours apart was the most effective strategy.     

Risk factors for postpartum ovarian cysts and their spontaneous recovery or persistence in lactating dairy cows

Cystic ovarian disease is a major cause of reproductive failure and economic loss for the dairy industry. Many cysts that develop during the early postpartum period regress spontaneously. However, it is difficult to decide at what point it would be more cost effective to treat ovarian cysts than to wait for spontaneous recovery. The objective of this study was to analyze risk factors for the development of the ovarian cystic condition during early and late postpartum, and for its persistence or recovery during the pre-service period in lactating dairy cows. Using multiple logistic regression, we analyzed data derived from 873 lactating dairy cows from a single herd. An ovarian cyst was diagnosed if it was possible to observe a single follicular structure with an antrum diameter > or = 25 mm in the absence of a corpus luteum in three sonograms performed at 7-day intervals. The cystic condition was denoted as early if the cyst was diagnosed 43-49 days postpartum, and late if detected 57-63-day postpartum. Spontaneous cyst regression before 60-day postpartum was regarded as early cystic recovery. For the early cystic group, there were no significant effects of lactation number, body condition score on prepartum Day 60, at parturition or on postpartum Day 30, or of body condition loss from parturition to 30-day postpartum. Cows calving in summer were 2.6 times more likely to develop ovarian cysts than those giving birth in winter. The risk of having a cyst was 1.9 times higher in cows with an abnormal puerperium. A 1-kg increase in milk yield raised the risk of cysts by a factor of 1.05. A 1-unit increase in body condition score (scale from 1 to 5) from prepartum Day 60 to parturition increased the risk of cyst development 8.4 times. Milk production and lactation number were negatively correlated with spontaneous early cyst recovery. A 1-kg decrease in milk production increased the probability of cyst recovery by a factor of 1.06, and a 1-unit drop in lactation number was associated with a 1.4-fold increased probability of cyst recovery. For the late cystic group, there were no significant effects of abnormal puerperium and body score data, except for a prepartum change in body score. Calving season (Odds ratio: 2.3), lactation number (Odds ratio: 1.36), increased milk production (Odds ratio: 1.05) and increased body condition score during the prepartum period (Odds ratio: 4.3) were all related to an increased risk of ovarian cysts. The probability of having a late cyst was 36.6 times greater in cows with early cysts. These findings suggest that it would be profitable to treat multiparous cows having cysts very early in the postpartum period, while treatment of primiparous cows should be delayed, at least until the end of the pre-service period, to provide the opportunity for spontaneous recovery.     

Effect of grass dry matter intake and fat supplementation on progesterone metabolism in lactating dairy cows

Progesterone (P4) metabolism in dairy cattle can be manipulated by alterations in dry matter intake and diet composition. Our objectives were to determine the effects of grazing allowance and fat supplementation on P4 metabolism in lactating dairy cows. Forty mid- to late-lactation Holstein-Friesian dairy cows were used in a completely randomized block design, with a 2 × 2 factorial arrangement of treatments. Cows were assigned to receive 1 of 2 pasture allowances (ad libitum allowance [AL], 9.5 kg dry matter per day, or restricted allowance [R] 7 kg dry matter per day) and 1 of 2 fat supplementation treatments (750 g per day saturated fat [F] or no fat supplement [NF]). All cows received an additional 4 kg per day of concentrate. Grass dry matter intake (GDMI) was measured 5 wk after the initiation of dietary treatment. Cows were treated with prostaglandin F_2α (PGF_2α) to eliminate the endogenous source of P4, and two intravaginal progesterone-releasing devices (CIDR) were inserted into each cow for a period of 8 days. Regular blood samples were taken before and after the removal of the intravaginal progesterone-releasing devices, and analyzed for P4 concentrations. The half-life (t½) and metabolic clearance rate (MCR) of P4 was calculated for each cow. There was no effect of GDMI or fat supplementation on the t½ or MCR of P4. There was a tendency for an interaction between GDMI and fat supplementation on the t½ of P4; cows on the restricted-F diet tended to have a longer P4 t½ than cows on the ad libitum-F diet. It was concluded that greater alterations in GDMI than achieved in the current study are required to change P4 metabolism. A combination of fat supplementation and restricted feeding slows P4 clearance, which may have beneficial implications for fertility.     

Low peripheral progesterone and late embryonic/early fetal loss in suckled beef and lactating dairy cows

Pregnancy failure during placentation in lactating dairy cows was associated with low concentrations of serum progesterone. Beef cows have greater serum progesterone and less pregnancy failure. Experiment 1 determined that reduction of serum progesterone affected late embryonic/early fetal loss in suckled beef cows. Cows (n = 40) received progesterone from two new or used controlled internal drug releasing devices, replaced every 5 d, beginning on Day 28 of gestation (mating = Day 0); CL were enucleated on Day 29. Retention of pregnancy was 77% in treated cows and 97% in 78 control cows (P < 0.05). Experiment 2 determined how pregnant, lactating dairy cows with high or low progesterone concentrations during Days 28-34 differed in luteal function or in serum progesterone during replacement therapy. Luteal tissue from such cows was assayed for progesterone and expression of mRNA for genes of endothelin and prostaglandin (PG) systems. Secretion of progesterone and prostaglandins by dispersed luteal cells was determined during incubation with LH, endothelin-1, or arachidonic acid. Neither luteal progesterone nor mRNAs for endothelin or prostaglandin systems differed. Endothelin-1 inhibited secretion of progesterone more (P < 0.05) in luteal cells from cows with low versus high serum progesterone, when incubated with arachidonic acid. Secretion of prostaglandin F₂α was increased and that of 6-keto-PGF₁α decreased by endothelin-1 in vitro. Serum progesterone during replacement was lower (P < 0.05) for cows with low than high serum progesterone at lutectomy. Thus, clearance, more than luteal production, determined peripheral progesterone in pregnant, lactating dairy cows.     

Body temperature in early postpartum dairy cows

A strategy widely adopted in the modern dairy industry is the introduction of postpartum health monitoring programs by trained farm personnel. Within these fresh cow protocols, various parameters (e.g., rectal temperature, attitude, milk production, uterine discharge, ketones) are evaluated during the first 5 to 14 days in milk (DIMs) to diagnose relevant diseases. It is well documented that 14% to 66% of healthy cows exhibit at least one temperature of 39.5 °C or greater within the first 10 DIM. Although widely adopted, data on diagnostic performance of body temperature (BT) measurement to diagnose infectious diseases (e.g., metritis, mastitis) are lacking. Therefore, the objective of this study was to identify possible factors associated with BT in postpartum dairy cows. A study was conducted on a commercial dairy farm including 251 cows. In a total of 217 cows, a vaginal temperature logger was inserted from DIM 2 to 10, whereas 34 cows did not receive a temperature logger as control. Temperature loggers measured vaginal temperature every 10 minutes. Rectal temperature was measured twice daily in all cows. On DIM 2, 5, and 10, cows underwent a clinical examination. Body temperature was influenced by various parameters. Primiparous cows had 0.2 °C higher BT than multiparous cows. Multiparous cows that calved during June and July had higher BT than those that calved in May. In primiparous cows, this effect was only evident from DIM 7 to 10. Furthermore, abnormal calving conditions (i.e., assisted calving, dead calf, retained placenta, twins) affected BT in cows. This effect was more pronounced in multiparous cows. Abnormal vaginal discharge did increase BT in primiparous and multiparous cows. Primiparous cows suffering from hyperketonemia (beta-hydroxybutyrat ≥ 1.4 mmol/L) had higher BT than those not affected. In multiparous cows, there was no association between hyperketonemia and BT. The results of this study clearly demonstrate that BT is influenced by various parameters in dairy cows. Therefore, these parameters have to be considered when interpreting measurements of BT in dairy cows. This information helps to explain the high incidence of type I and II errors when measuring BT and clearly illustrates that measures of BT should not be used as a single criterion to decide whether or not to provide antibiotic treatment to dairy cows. However, research-based test characteristics of other parameters (e.g., vaginal discharge) alone or in combination with BT are still lacking.     

Reproductive performance of lactating dairy cows following estrus synchronization regimens with PGF2alpha and progesterone

The objective of this study was to evaluate the reproductive performance of lactating cows in seasonal dairy herds after estrus synchronization with PGF2alpha (PG) with or without supplementation with progesterone (P4). In Trial 1, synchronized cows (S1; n = 521) were compared with untreated control cows (C; n = 518) in 5 herds. Estrus of cows in the S1 group was synchronized with 2 treatments of PG (Lutalyse) 13 d apart. The breeding season started 2 d after the second PG. Cows were first bred by AI for 7 wk and then herd sires were used. Compared with C cows, estrus synchronization in the treated cows reduced the conception rate to first AI (61.1 vs 70.5%; P < 0.01) and the intervals from start of the breeding season to conception for cows conceiving to AI (11.0 vs 14.6 d; P < 0.05) or to both AI and natural mating (16.5 vs 18.4 d; P < 0.05). There was no effect on conception rate to second AI (68.8%), on pregnancy rate by Day 24 (72.3%) or Day 49 (86.3%) of the breeding season, or on the percentage of cows not pregnant at end of the breeding season (5.0%). In Trial 2, effects of P4 supplementation before the second PG on reproductive performance were evaluated in 4 herds. Estrus of each cyclic cow was synchronized with PG as in Trial 1. Half of the cows in each herd were treated with an intravaginal P4 device (CIDR) for 5 d before the second PG (S2+P4, n = 608), whereas the remaining half received no CIDR treatment (S2, n = 593). Compared with S2 cows, P4 treatment increased the estrous response rate to the second PG (89.6 vs 82.9%; P < 0.01), the conception rate to first AI (65.1 vs 59.7%; P = 0.07), the pregnancy rate by Day 6 of the breeding season (59.3 vs 49.0%; P < 0.001), and reduced the intervals from start of the breeding season to conception for cows conceiving to AI (8.6 vs 10.4 d; P < 0.10) or to both AI and natural mating (12.7 vs 16.4 d; P < 0.01). Treatment with a used CIDR from Days 16 to 21 after start of breeding to re-synchronize returns to service had no effect on conception rate to first or second AI but may decrease the conception rate to second AI in cows previously treated with CIDR. In conclusion, estrus synchronization with the double PG system can reduce fertility, while P4 supplementation for 5 d before the second PG can improve estrous response and overall reproductive performance. Stage of the estrous cycle at the time of the second PG can affect fertility following synchronization.     

Is there a relationship between genetic merit and enteric methane emission rate of lactating Holstein-Friesian dairy cows?

The present study was undertaken to examine the effect of cow genetic merit on enteric methane (CH₄) emission rate. The study used a data set from 32 respiration calorimeter studies undertaken at this Institute between 1992 and 2010, with all studies involving lactating Holstein-Friesian dairy cows. Cow genetic merit was defined as either profit index (PIN) or profitable lifetime index (PLI), with these two United Kingdom genetic indexes expressing the expected improvement in profit associated with an individual cow, compared with the population average. While PIN is based solely on milk production, PLI includes milk production and a number of other functional traits including health, fertility and longevity. The data set had a large range in PIN (n=736 records, −£30 to +£63) and PLI (n=548 records, −£131 to +£184), days in milk (18 to 354), energy corrected milk yield (16.0 to 45.6 kg/day) and CH₄ emission (138 to 598 g/day). The effect of cow genetic merit (PIN or PLI) was evaluated using ANOVA and linear mixed modelling techniques after removing the effects of a number of animal and diet factors. The ANOVA was undertaken by dividing each data set of PIN and PLI into three sub-groups (PIN:<£3, £3 to £15 and >£15, PLI:<£23, £23 to £67 and >£67) with these being categorised as low, medium and high genetic merit. Within the PIN and PLI data sets there was no significant differences among the three sub-groups in terms of CH₄ emission per kg feed intake or per kg energy corrected milk yield, or CH₄ energy (CH₄-E) output as a proportion of energy intake. Linear regression using the whole PIN and PLI data sets also demonstrated that there was no significant relationship between either PIN or PLI, and CH₄ emission per kg of feed intake or CH₄-E output as a proportion of energy intake. These results indicate that cow genetic merit (PIN or PLI) has little effect on enteric CH₄ emissions as a proportion of feed intake. Instead enteric CH₄ production may mainly relate to total feed intake and dietary nutrient composition.     

Managing the dominant follicle in lactating dairy cows

Reproductive efficiency is not optimal in high-producing dairy cows. Although many aspects of ovarian follicular growth in cows are similar to those observed in heifers, there are numerous specific differences in follicular development that may be linked with changes in reproductive physiology in high-producing lactating dairy cows. These include: 1) reduced circulating estradiol (E2) concentrations near estrus, 2) ovulation of follicles that are larger than the optimal size, 3) increased double ovulation and twinning, and 4) increased incidence of anovulation with a distinctive pattern of follicle growth in anovular dairy cows. The first three changes become more dramatic as milk production increases, although anovulation has not generally been associated with level of milk production. To overcome reproductive inefficiencies in dairy cows, reproductive management programs have been developed to synchronize ovulation and enable the use of timed AI in lactating dairy cows. Effective regulation of the CL, follicles, and hormonal environment during each part of the protocol is critical for optimizing these programs. This review discusses the distinct aspects of follicular development in lactating dairy cows and the methodologies that have been utilized in the past two decades in order to manage the dominant follicle during synchronization of ovulation and timed AI programs.     

Managing the dominant follicle in lactating dairy cows

Reproductive efficiency is not optimal in high-producing dairy cows. Although many aspects of ovarian follicular growth in cows are similar to those observed in heifers, there are numerous specific differences in follicular development that may be linked with changes in reproductive physiology in high-producing lactating dairy cows. These include: 1) reduced circulating estradiol (E2) concentrations near estrus, 2) ovulation of follicles that are larger than the optimal size, 3) increased double ovulation and twinning, and 4) increased incidence of anovulation with a distinctive pattern of follicle growth in anovular dairy cows. The first three changes become more dramatic as milk production increases, although anovulation has not generally been associated with level of milk production. To overcome reproductive inefficiencies in dairy cows, reproductive management programs have been developed to synchronize ovulation and enable the use of timed AI in lactating dairy cows. Effective regulation of the CL, follicles, and hormonal environment during each part of the protocol is critical for optimizing these programs. This review discusses the distinct aspects of follicular development in lactating dairy cows and the methodologies that have been utilized in the past two decades in order to manage the dominant follicle during synchronization of ovulation and timed AI programs.     

The utilization of canola and its constituents by lactating dairy cows

Three feeding trials and one nylon bag trial were conducted to determine the effect of supplementing a barley-based control diet with 3.5% canola oil (CO), 22% presscake (CPC) or 9% whole seed (WCS) on feed intake, digestibility, milk yield and composition of lactating dairy cows. Ruminal utilization of canola meal (CM), CPC and WCS was also determined. Increasing the level of fat in the diet had no significant effect on intake of concentrate or digestible energy, or on total tract digestibility of dry matter (DM), crude protein (CP) and acid detergent fibre. Addition of canola in the form of CPC and WCS gave greater energy and ether extract digestibility than C and CO (P < 0.05). Diet had no significant effect on milk production, yield of milk CP, milk lactose + ash, gross energetic efficiency of milk production, milk urea or minerals. Milk fat and 4% fat corrected milk (FCM) yield were similar with the C and CPC diets, and with the CO and WCS diets. But the CO and WCS diets gave less milk fat and FCM than the C diet (P < 0.05). Milk crude protein was higher (P < 0.05) on the WCS diet than on the C, CO and CPC diets, which were similar. Diets WCS, C and CO promoted similar levels of blood urea (BU) but BU levels with CPC and CO were lower than with the C diet (P < 0.05). Ruminal DM and CP disappearance of CM was lower than for WCS and CPC at all incubation times (P < 0.05).     

Relationships between transition period diet,metabolic parameters and fertility in lactating dairy cows

Cows in severe negative energy balance after calving have reduced fertility, mediated by metabolic signals influencing the reproductive system. We hypothesised that transition diet could alter metabolic status after calving, and thus influence fertility. Multiparous dairy cows were assigned to four transition groups 6 weeks pre-calving and fed: (a) basal control diet (n = 10); (b) basal diet plus barley (STARCH, n = 10); (c) basal diet plus Soypass (high protein, HiPROT, n = 11); or (d) no transition management (NoTRANS, n = 9). All cows received the same lactational diet. Blood samples, body weights and condition scores (BCS) were collected weekly. Fertility parameters were monitored using milk progesterone profiles and were not affected by transition diet. Data from all cows were then combined and analysed according to the pattern of post-partum ovarian activity. Cows with low progesterone profiles had significantly lower insulin-like growth factor-I (IGF-I) and insulin concentrations accompanied by reduced dry matter intakes (DMIs), BCS and body weight. Cows with prolonged luteal activity (PLA) were older and tended to have lower IGF-I. Analysis based on the calving to conception interval revealed that cows which failed to conceive (9/40) also had reduced IGF-I, BCS and body weight. Fertility was, therefore, decreased in cows which were in poor metabolic status following calving. This was reflected in reduced circulating IGF-I concentrations and compromised both ovarian activity and conception. There was little effect of the transition diets on these parameters.     

Relationship between level of milk production and estrous behavior of lactating dairy cows

The objective of this study was to determine if there is an association between level of milk production and duration of estrus as determined by standing activity recorded by a radiotelemetry system. Holstein cows (n = 267; 50 DIM) were fitted with a transmitter that allowed continuous recording of standing activity. Cows were housed in a free-stall barn and milked twice daily. Ovulation was confirmed for all estruses (n = 380). Average milk production for the 10 days before the day of estrus was used to classify cows as lower (< 39.5 kg/day) or higher (>/= 39.5 kg/day) producers at the time of estrous expression. Follicle size and serum estradiol (E(2)) concentrations were determined in a subset of cows (n = 71) on the day of estrus. Duration (6.2 +/- 0.5 h versus 10.9 +/- 0.7 h; P < 0.0001), standing events (6.3 +/- 0.4 versus 8.8 +/- 0.6; P = 0.001), and standing time (21.7 +/- 1.3 s versus 28.2 +/- 1.9 s; P = 0.007) were shorter for estruses from higher (46.4 +/- 0.4 kg/day; n = 146) than lower producers (33.5 +/- 0.3 kg/day; n = 177). Milk production was correlated with the duration of estrus (r = -0.51; P < 0.0001; n = 323). Higher producers had lower E(2) concentrations than lower producers (6.8 +/- 0.5; n = 31 versus 8.6 +/- 0.5 pg/ml; n = 40; P = 0.01) in spite of larger pre-ovulatory follicle diameter (18.6 +/- 0.3; n = 31 versus 17.4 +/- 0.2 mm; n = 40; P 0.004). Interestingly, E(2) concentrations were not correlated with diameter of the pre-ovulatory follicle (r = -0.17; P = 0.15) but milk production was correlated with both E(2) concentrations (r = -0.57; P < 0.0001) and diameter of the pre-ovulatory follicle (r = 0.45; P < 0.0001). Thus, high milk production decreases duration of estrus probably due to decreased circulating concentrations of E(2).     

Reproductive tract defense and disease in postpartum dairy cows

This paper briefly reviews recent data and concepts on the development and mitigation of infection and inflammation in the reproductive tract of dairy cows during the first 2 mo after calving. The incidence of metritis is typically between 10 and 20%, of clinical endometritis or purulent vaginal discharge (PVD) approximately 15%, and of subclinical or cytological endometritis a further 15%. Worse postpartum negative energy balance is associated with more severe or prolonged uterine inflammation. Changes in feed intake, expression of genes for pro-inflammatory cytokines, notably interleukin (IL) 1, IL6 and IL8, circulating concentrations of beta-hydroxybutyrate (BHBA) or nonesterified fatty acids (NEFA), and innate immune function precede both metritis and endometritis by several weeks. Infections with Escherichia coli and Arcanobacterium pyogenes are associated with both metritis and PVD. There are new data to suggest that specific virulence factors in E. coli associated with adherence may be important in metritis and PVD. Cytological endometritis and PVD are overlapping but largely distinct conditions, and there are emerging data that cervicitis exists both concurrent with and separate from endometritis. Much remains to be learned about what initiates and sustains harmful inflammation of the reproductive tract. Such information is necessary to develop effective treatments for the various forms of disease and, more importantly, to develop means to prevent endometritis and cervicitis. In particular, vaccination against specific uterine pathogens and interventions to modulate innate immune response appear to be important avenues for investigation. Presently, commonly recommended best management practices for cows in the transition period are likely to be helpful to mitigate the risk of reproductive disease.