Review: effect of protein nutrition on ovarian and uterine physiology in dairy cattle

Relationship of vaginal discharge characteristics evaluated by Metricheck device to metabolic status in postpartum dairy cows

The relationship between vaginal discharge characteristics and metabolic status has been studied in postpartum dairy cows. Vaginal discharges at 2-6 weeks postpartum were scored weekly on a 1 (clear) to 5 (purulent material with stench) scale using the Metricheck device and classified into three groups as follows: Endometritis group (n = 19), greater than or equal to score 4 until 3 weeks postpartum; Delayed involution group (n = 9), score 2 or 3 after having score 1; Healthy group (n = 23), cows except those belonging to the Delayed involution and Endometritis groups. The uterus and cervix were assessed using ultrasonography. Blood samples were collected twice weekly from 1 to 6 weeks postpartum from all cows and were additionally obtained for 13,14-dihydro-15-keto-prostaglandin F2α (PGFM) measurements from multiparous cows. Cows with delayed involution had delayed onset of luteal activity (p < 0.05) and higher serum urea nitrogen (BUN) concentrations (p < 0.01) than healthy animals. Cows with endometritis had more peripartum diseases (p < 0.05), lower milk yield (p < 0.05), longer cervix diameter (p < 0.05), and lower serum albumin (p < 0.01), total cholesterol (p < 0.01), and magnesium (p < 0.01) concentrations, and higher aspartate aminotransferase levels (p < 0.05) than healthy cows. Plasma PGFM concentrations tended to be higher in the Delayed involution group (p = 0.083) and lower in the Endometritis group (p = 0.085) than in the Healthy group. In summary, delayed involution was shown to be associated with higher BUN concentration, and endometritis may have been caused by peripartum diseases and hepatic dysfunction.

Exploring factors associated with bulk tank milk urea nitrogen in Central Thailand

Aim

The study was to determine seasonal fluctuations and non-nutritional factors associated with bulk tank milk urea nitrogen(BTMUN).

Materials and Methods

A total of 58,364 BTM testing records were collected from 2364 farms in Central Thailand during September 2014-August 2015. Using square root BTMUN as the outcome, other milk components, farm effect, and sampling time were analyzed by univariable repeated measures linear regression, and significant variables were included in multivariable repeated measures linear regression.

Results

The average BTMUN (standard deviation) was 4.71 (±1.16) mmol/L. In the final model, BTM fat and protein percentages were associated with BTMUN as quadratic and cubic polynomials, respectively. BTM lactose percentage and the natural logarithm of somatic cell counts were negatively linearly associated with BTMUN. At the farm level, the BTM lactose association was negatively linear; herd BTMUN decreased following an increase of herd lactose average, and BTM lactose slopes were quite different among farms as well. Sampling time had the highest potency for the estimation of BTMUN over time, with lows and highs occurring in August and October, respectively. The variation in test level BTMUN was decreased by 18.6% compared to the null model, and 6% of the variance could be explained at the farm level.

Conclusion

The results clarify seasonal variation in BTMUN and the relationships among other BTM constituents and BTMUN, which may be useful for understanding how to manage lactating dairy cattle better to keep BTM constituents within normal ranges.

Pasture Feeding Changes the Bovine Rumen and Milk Metabolome

The purpose of this study was to examine the effects of two pasture feeding systems-perennial ryegrass (GRS) and perennial ryegrass and white clover (CLV)-and an indoor total mixed ration (TMR) system on the (a) rumen microbiome; (b) rumen fluid and milk metabolome; and (c) to assess the potential to distinguish milk from different feeding systems by their respective metabolomes. Rumen fluid was collected from nine rumen cannulated cows under the different feeding systems in early, mid and late lactation, and raw milk samples were collected from ten non-cannulated cows in mid-lactation from each of the feeding systems. The microbiota present in rumen liquid and solid portions were analysed using 16S rRNA gene sequencing, while ¹H-NMR untargeted metabolomic analysis was performed on rumen fluid and raw milk samples. The rumen microbiota composition was not found to be significantly altered by any feeding system in this study, likely as a result of a shortened adaptation period (two weeks' exposure time). In contrast, feeding system had a significant effect on both the rumen and milk metabolome. Increased concentrations of volatile fatty acids including acetic acid, an important source of energy for the cow, were detected in the rumen of TMR and CLV-fed cows. Pasture feeding resulted in significantly higher concentrations of isoacids in the rumen. The ruminal fluids of both CLV and GRS-fed cows were found to have increased concentrations of p-cresol, a product of microbiome metabolism. CLV feeding resulted in increased rumen concentrations of formate, a substrate compound for methanogenesis. The TMR feeding resulted in significantly higher rumen choline content, which contributes to animal health and milk production, and succinate, a product of carbohydrate metabolism. Milk and rumen-fluids were shown to have varying levels of dimethyl sulfone in each feeding system, which was found to be an important compound for distinguishing between the diets. CLV feeding resulted in increased concentrations of milk urea. Milk from pasture-based feeding systems was shown to have significantly higher concentrations of hippuric acid, a potential biomarker of pasture-derived milk. This study has demonstrated that ¹H-NMR metabolomics coupled with multivariate analysis is capable of distinguishing both rumen-fluid and milk derived from cows on different feeding systems, specifically between indoor TMR and pasture-based diets used in this study.

Resumption of reproductive activity in the early postpartum period of cows

Following parturition, there is an early resumption of sequential but transient FSH increases of 2-3 days duration in dairy and beef cows. The first increase results in the emergence of the first postpartum follicle wave and the decline in FSH results in selection of a dominant follicle (DF). The ovulatory fate of this DF is dependent on LH pulse frequency and IGF-I concentrations. The energy status of the cows affects the degree of anoestrus. High yielding cows in prolonged negative energy balance (NEB) have a greater incidence of anoestrous, where the DF is smaller and fails to produce sufficient oestradiol to induce ovulation. Thus, there are sequential follicle waves in anoestrus prior to first ovulation. A small percent of DFs in dairy cows fail to ovulate and they continue to grow due to high LH pulse frequency and form follicular cysts. These cysts produce oestradiol for a variable period and then become physiologically defunct, despite their morphological presence for variable periods before final regression. During their physiological active state, new follicle wave emergence and ovulation are suppressed. A further problem in high yielding cows is the increased incidence of abnormal ovarian cycles after ovulation, and specifically, the high incidence of maintained corpora lutea (CL), probably related to uterine problems in the peri-parturient period. The ovulation of smaller DFs and the high liver metabolic rate may adversely affect oestradiol and progesterone concentrations. The long-term effects of prolonged NEB on oocyte competence, DF physiology and follicular and luteal steroidogenesis all may have detrimental effects on conception rates to AI. Hormonal methods to induce ovulation should be carried out in conjunction with corrective management problems, once diagnosed The pre-treatment of anoestrous cows with progesterone for 5-9 days is a prerequisite for the concomitant expression of oestrus at first ovulation, but whether or not further hormonal therapy is necessary to ensure the ovulation of the DF, is dependent on energy status, body condition score and postpartum interval, which regulate LH pulse frequency.

Nutritional effects on resumption of ovarian cyclicity and conception rate in postpartum dairy cows

Increased genetic potential for milk production has been associated with a decline in fertility of lactating cows. Following parturition the nutritional requirements increase rapidly with milk production and result in negative energy balance (NEBAL). NEBAL delays the time of first ovulation thereby affecting ovarian cycles before and during the subsequent breeding period The effects of NEBAL on reinitiation of ovulation are manifested through inhibition of LH pulse frequency and low levels of glucose, insulin and IGF-I in blood that collectively restrain oestrogen production by dominant follicles. Upregulation of LH pulses and peripheral IGF-I in association with the NEBAL nadir increases the likelihood that emerging dominant follicles will ovulate. The legacy of NEBAL is reduced fertility after insemination in conjunction with reduced serum progesterone concentrations. Diets high in crude protein support high milk yield, but may be detrimental to reproductive performance. Depending upon protein quantity and composition, serum concentrations of progesterone may be lower and the uterine luminal environment is altered. High protein intake is correlated with plasma urea concentrations that are inversely related to uterine pH and fertility. The direct effects of high dietary protein and plasma urea on embryo quality and development in cattle are inconsistent. In conclusion, the poor fertility of high producing dairy cows reflects the combined effects of a uterine environment that is dependent on progesterone, but has been rendered suboptimal for embryo development by antecedent effects of negative energy balance and may be further compromised by the effects of urea resultingfrom intake of high dietary protein.

Embryo survival rate in cattle: a major limitation to the achievement of high fertility

Over the past 30-40 years genetic improvement and better nutrition of dairy cows have led to a significant increase in milk production per cow but this is associated with an increase in cow reproductive wastage. Reproductive wastage in the dairy herd particularly in a seasonal calving system, results in a serious financial loss. Early embryo death accounts for a significant portion of cow reproductive wastage and information is becoming available on the extent and timing of early embryo loss and on aspects of embryo growth, development, metabolism and viability. Such information is necessary to facilitate objective investigation of factors that contribute to early embryo death. For heifers and moderate yielding dairy cows published estimates of fertilisation rate of about 90%, and of average calving rates of about 55% indicate an embryonic and foetal mortality rate of about 40%. Of this total loss, 70 to 80% is sustained between days 8 and 16 after insemination, a further 10% between days 16 and 42 and a further 5-8% between day 42 and term. In high yielding cows there is some evidence of a higher increment of late embryo loss. During the period of greatest embryo loss, between days 8 and 16 after fertilisation, there is a dramatic increase in the growth rate and protein content of embryos, particularly from day 13 to day 16 when the increase is exponential. There is evidence that from day 13 to 15 cattle embryos undergo time and developmental stage-dependent changes in the rate of de-novo protein synthesis and protein phosphorylation. It seems that by the time cattle embryos have elongated they have passed their maximal synthetic activity in terms of protein synthesis and phosphorylation, which seems to occur at day 13 or earlier. While there is little published information on the causes of embryo loss it is clear that even a short-term reduction in energy intake near the time of insemination can significantly reduce embryo survival rate. Abo and low post-ovulatory systemic progesterone has been associated with increased embryo loss. Recent evidence shows that elevated systemic concentrations of ammonia and urea per se do not reduce embryo survival rate but there may be other modifying factors, such as negative energy balance, operating in the high yielding dairy cow that lead to reduced fertility when the systemic concentrations of urea and or, ammonia are high.

Associations of periparturient plasma biochemical parameters, endometrial leukocyte esterase and myeloperoxidase, and bacterial detection with clinical and subclinical endometritis in postpartum dairy cows

This study was aimed at demonstrating associations between peripheral biochemical parameters, endometrial leukocyte esterase (LE) and myeloperoxidase (MPO), and bacterial detection with the degree of endometrial inflammation, and determining the best time postpartum for diagnosing endometritis to predict subsequent fertility in dairy cows. Plasma albumin, blood urea nitrogen (BUN), total cholesterol (T-cho), NEFA, and BHBA concentrations were analyzed in 43 Holstein cows at 3, 5 and 7 weeks postpartum (W3, W5 and W7). Endometrial samples were collected at W3, W5 and W7 to examine LE and MPO activities, bacterial detection rates, and PMN% profiles. The 43 cows were divided into healthy (HE), subclinical endometritis (SE), and clinical endometritis (CE) groups, classified differently at W3, W5 and W7 based on the definitions of SE and CE for each of the three weeks pp. LE level had an association with PMN% in all weeks pp (P<0.05). Albumin and BUN levels had weak negative associations with endometrial PMN% at W3. Pathogenic bacterial detection rates were higher in the cows with endometritis at W3 and W5. Conception rate at first artificial insemination tended to be lower (P=0.057) in the cows diagnosed with endometritis at W3 than in the healthy cows. In conclusion, associations were found between endometrial LE and endometritis, but not for MPO and endometritis. Diagnosing endometritis in W3 may be the best moment to predict subsequent fertility.

Effect of dried distiller's grains plus solubles in postpartum diets of beef cows on reproductive performance of dam and heifer progeny

Forty-eight primiparous and multiparous cows were fed a silage-based total mixed ration (TMR; CON), a TMR with 2.5 kg/d DM dried distiller's grains plus solubles (DDGS; MID), or a TMR with 4.7 kg/d DM DDGS (HIGH) from 8.5 ± 4 to 116 ± 4 d postpartum (DPP). All diets were formulated to be isocaloric for a postpartum ADG targeted at 0.22 kg, whereas CP exceeded requirements in both diets containing DDGS. Blood samples were collected from dams at 7- and 21-d intervals for progesterone concentration (resumption of cyclicity) and plasma urea nitrogen, respectively. A weigh-suckle-weigh procedure was used to measure milk production, and samples were collected for milk composition and fatty acid profile. A 5-d Co-Synch + controlled internal drug release (CIDR) protocol was used, and cows were bred (97 ± 4 DPP) by timed AI (TAI). Ultrasonography was used for measurement of the largest antral follicle at TAI and pregnancy diagnosis. Nineteen days after TAI, cow and calf pairs were managed as a single group until weaning and exposed to natural mating for a total of a 60-d breeding season. Starting at weaning, blood samples were collected from heifer offspring at 7-d intervals for progesterone concentration used as an indicator of puberty. A 5-d Co-Synch + CIDR protocol was used, and heifers were bred by TAI. Transrectal ultrasonography was used for measurement of the largest antral follicle at TAI and antral follicle count (AFC) at CIDR device insertion as well as pregnancy diagnosis. There were no differences in dam ADG ( = 0.364); however, DMI decreased with increasing DDGS ( < 0.0001), resulting in an increased feed efficiency ( = 0.042). Milk fat and lactose tended to increase with the addition of DDGS in the diet ( ≤ 0.055), and milk urea nitrogen increased ( < 0.001). There were no differences in resumption of cyclicity ( = 1.00) or diameter of the largest antral follicle ( ≥ 0.372). Timed AI pregnancy rates were not different with the addition of DDGS in the diet ( ≥ 0.174). Heifer ADG was reduced with DDGS during late lactation ( = 0.031). Heifer AFC had a tendency to increase with increasing DDGS ( = 0.081), with no impacts on dominant follicle diameter at TAI ( = 0.161). Heifer TAI pregnancy rate also was not different among treatments ( = 0.508). Overall, feeding 4.7 kg/d DM of DDGS to dams during early lactation increases feed efficiency of the dam, with minor statistically significant effects on dam or heifer offspring reproduction.

Evaluation of criteria for optimal time AI postulated by estrous signs in lactating dairy cows kept in tie-stalls

Relaxation of the intravaginal part of the uterus is obvious around 6 to 18 h before ovulation, and this is considered the optimal time for artificial insemination (AI), as demonstrated in recent studies. Estrous signs have been suggested as useful criteria for determining the optimal time for AI. Therefore, this study evaluated the usefulness of estrous signs, particularly the relaxation of the intravaginal part of the uterus, as criteria for determining the optimal time for AI. A Total of 100 lactating Holstein-Friesian cows kept in tie-stall barns were investigated. AI was carried out based on the criterion for the optimal time for AI (optimal group), and earlier (early group) and later (late group) than the optimal time for AI, determined on the basis of estrous signs. After AI, ovulation was assessed by rectal palpation and ultrasonographic observation at 6-h intervals. For 87.5% (35/40) of cows in the optimal group, AI was carried out 24-6 h before ovulation, which was previously accepted as the optimal time for AI. AI was carried out earlier (early group) and later (late group) than optimal time for AI in 62.1% (18/29) and 71.0% (22/31) of cows, respectively. The conception rate for the optimal group was 60.0%, and this conception rate was higher than that for the early group (44.8%) and late group (32.2%), without significance. Further, the conception rate of the optimal group was significantly higher than the sum of the conception rates of the early and late groups (38.3%; 23/60) (P < 0.05). These results indicate that the criteria postulated, relaxation of the intravaginal part of the uterus and other estrous signs are useful in determining the optimal time for AI. Furthermore, these estrous signs enable the estimations of stages in the periovulatory period.

Evaluation of a commercially available radioimmunoassay and enzyme immunoassay for the analysis of progesterone and estradiol and the comparison of two extraction efficiency methods

The measurement of progesterone (P4) and estradiol (E2) is essential for monitoring reproductive cycles and can aid in diagnosing the cause of poor reproductive performance in dairy cattle. Readily available, reproducible, accurate, non-radioactive assays are needed for the assessment of P4 and E2 in bovine serum. The gold standard for hormone assessment, radioimmunoassay (RIA), was compared with enzyme-linked immunoassay (EIA). Serum collected from various points in the estrous cycle was extracted with radiolabeled P4 (ie, ³H-P4; HE) and without ³H-P4 (CE) before being used in the assay. For the assessment of P4, there is a great degree of correlation between the RIA and EIA (adjusted R-square = 0.95; Pearson correlation coefficient (PCC) = 0.98, P < 0.001). A difference between the RIA and EIA methods was not detected for E2 concentrations (P = 0.16), but the correlation between techniques was poor (adjusted R-squared = 0.73; PCC = 0.87, P = 0.002). There was no difference in the serum extraction efficiency as measured with ³H-P4 as opposed to without (P = 0.94). The two methods for the measurement of serum extraction efficiency were highly correlated (adjusted R-square = 0.83; PCC = 0.92, P < 0.001). The concordance correlation coefficient (CCC) showed an excellent agreement between RIA and EIA for P4 determination (0.89) and between HE and CE methods (0.90). Although the 95% limits of agreement of the Bland-Altman plots encompassed 89% (8/9) and 92% (12/13) of the differences between methods for P4 quantification and extraction respectively, the CCC indicated an excellent agreement among them. The CCC between RIA and EIA for E2 quantification was 0.68 which corresponds with a fair agreement; however, the 95% limits of agreement of the Bland-Altman plot encompassed 100% (9/9) of differences between methods. The EIA and CE methods are comparable alternatives to the RIA and HE methods, respectively and can be used to quantify P4 and E2 for bovine serum.

Effects of feeding green microalgae on ovarian activity, reproductive hormones and metabolic parameters of Boer goats in arid subtropics

The present study aimed to improve ovarian follicle development and plasma metabolites and hormone concentrations upon supplementation of Boer goats with green microalga (Dunaliella salina; 10 g/head/day) (N = 20; MAT group) compared to control (N = 10; not receive microalgae) in subtropics. Estrus was synchronized in all animals by two intramuscular administration of 12.5 mg dinoprost 11 days a part. MAT group was supplemented with Dunaliella salina for 11 days (from the day of first injection of dinoprost till the second injection). Ovarian performance, steroids, LH, FSH and blood metabolites were assessed every three days during the estrous cycle. Numbers and sizes of ovarian follicles and corpora lutea were significantly (P < 0.05) increased in MAT group. Progesterone, estrogen, FSH and LH were higher in MAT group during estrous cycle. Blood metabolites including glucose, total cholesterol and blood urea nitrogen were significantly (P < 0.05) increased upon D. salina administration. On the other hand, supplementation of D. salina resulted in significant decrease of plasma total protein, albumin, aspartate aminotransferase and alanine aminotransferase. In conclusion, supplementation with D. salina could improve ovarian follicle development and concentrations of plasma metabolites and hormones which subsequently improves reproductive performance of Boer goats.

High urea and pregnancy or conception in dairy cows: A meta-analysis to define the appropriate urea threshold

Dietary proteins play an important role in reproduction, and increased dietary crude proteins, increased degradability of dietary proteins, and elevated blood or milk urea have been associated with decreased conception and pregnancy in many studies. The aim of this work was to provide a meta-analysis on the relationship between high milk or blood urea and pregnancy or conception, with a focus on defining the appropriate urea threshold associated with this issue. The meta-analysis included 61 different models from 21 papers. The thresholds of urea tested in the various models were built by steps of 1 mM urea. This constructed variable reduced heterogeneity by 61% in the meta-regression. The meta-analysis showed 43% lower odds of pregnancy or conception (odds ratio = 0.57; 95% confidence interval = 0.45-0.73) in cases where urea was ≥7.0 mM in the blood (plasma urea nitrogen = 19.3 mg/dL) or where urea was ≥420 mg/L in the milk compared with where urea values were lower. This threshold is the most suitable with regard to pregnancy or conception success, even if a threshold of 6.5 mM cannot be excluded with certainty. The results also highlighted the possibility of a stronger association between high urea concentrations and pregnancy or conception when high nitrogen exposure occurs before artificial insemination compared with after artificial insemination, but this possibility needs to be further studied. Whether the present results also apply to extensively pasture-based countries remains to be determined.

Influence of excessive dietary protein intake during late gestation on drylot beef cow performance and progeny growth, carcass characteristics, and plasma glucose and insulin concentrations

Spring-calving cows ( = 49) were used to investigate the effects of excessive prepartum dietary protein intake on late gestation cow performance as well as subsequent progeny growth, carcass characteristics, and plasma glucose and insulin concentrations. Treatments were formulated to be isocaloric and provide 100% (REQ) or 129% (HP) of CP requirement. Treatments were limit-fed 78 ± 12 d prepartum to calving. All cows were fed a common diet postpartum. Cow BW and BCS were recorded at initiation of treatments and within 48 h post-calving. Milk production was estimated via the weigh-suckle-weigh technique 69 ± 11 d postpartum. Calf BW was measured at birth and at weaning (121 ± 11 d of age). Progeny ( = 42) were weaned as a group and placed into a feedlot and fed a common finishing diet. Glucose and insulin concentrations were analyzed on a subset of progeny (12 per treatment) 90, 120, 150, 180, 210, and 240 min post-feeding, 2 d before slaughter (342 ± 11 d of age). Treatment had no effect ( ≥ 0.22) on cow BW, BCS, milk production, and subsequent reproduction or progeny preweaning growth. Progeny finishing growth and marbling scores were not affected ( ≥ 0.24) by treatment, yet 12th rib fat thickness ( < 0.01), KPH ( = 0.04), and YG ( = 0.01) were greater for progeny born to HP dams. Progeny born to HP dams had decreased ( ≤ 0.01) glucose and insulin concentrations, and insulin to glucose ratios, indicating greater insulin sensitivity. Although feeding cows 129% of CP requirement during late gestation did not affect cow performance or progeny preweaning or finishing period growth; carcass adiposity was increased by maternal treatment.

Protein based flushing related blood urea nitrogen effects on ovarian response, embryo recovery and embryo quality in superovulated ewes

The present study is the first report that evaluates effects of nutritional effects of flushing with differing diet crude protein ratios on blood urea nitrogen (BUN) levels, related some reproductive parameters and embryo quality in ewe. During mating season, before synchronization protocol ewes were fed on alfalfa hay and additive concentrate feeding as flushing. Intra vaginal FGA containing sponges applied for 12 days for the purpose of synchronization and pFSH was administered by 8 declining doses for the purpose of superovulation. Uterus was flushed in the morning of the seventh day of mating and embryos were collected surgically. Collected embryos were qualified according to IETS criterion. There is no dependency found between BUN values measured at different days and at different diet crude protein concentrations. An increase in uterine pH levels due to increasing protein amounts was observed but this increase was not significant among groups. Ovarian function was evaluated by ovarian responses (CL + large follicle) showed difference between groups (p < 0.05) and the lowest protein intake group gave highest ovarian response. In addition, embryo recovery rates revealed difference between groups (p < 0.05) and it was observed that the lowest ovarian response group showed the highest rates of embryo recovery. It is concluded that, in some Anatolian native sheep breeds, the application of diet flushing with different crude protein concentrates influence ovarian responses and embryo recovery rates but has no effect on BUN levels; uterus physiology or embryonic quality.

Changes in milk urea around insemination are negatively associated with conception success in dairy cows

Dietary protein levels are a risk factor for poor reproductive performance. Conception is particularly impaired in cases of high blood or milk urea. The objective of this study was to investigate the association between conception and low milk urea or changes in milk urea around artificial insemination (AI). Data were obtained from the French Milk Control Program for a 4-yr period (2009-2012). Milk urea values between 250 and 450 mg/kg (4.3 and 7.7 mM) were considered intermediate (I), and values ≤150 mg/kg (2.6 mM) were considered low (L). Milk urea values before and after each AI were allocated into 4 classes representing the dynamics of milk urea (before-after; I-I, I-L, L-I, and L-L). Subclinical ketosis was defined using milk fat and protein contents before AI as proxies. A logistic regression with a Poisson correction and herd as a random variable was then performed on data from Holstein or all breeds of cows. The success of conception was decreased [relative risk (95% confidence interval) = 0.96 (0.94-0.99)] in low-urea cows compared with intermediate-urea cows after AI; no significant association was found for urea levels before AI. When combining data on urea before and after AI, I-L urea cows exhibited a 5 to 9% decrease in conception compared with I-I urea cows, and L-I urea cows showed no difference in conception success compared with I-I urea cows. A decreased conception success for L-L urea cows compared with I-I urea cows was observed for the analysis with cows of all breeds. This work revealed that a decrease in urea from intermediate (before AI) to low (after AI) is a risk factor for conception failure. Surveys of variation in milk urea in dairy cows close to breeding are highly recommended.

Challenges of feeding dairy cows in Australia and New Zealand

There is a continuing evolution of feeding systems in both Australian and New Zealand dairy industries and this presents challenges for the future. Since the turn of the century, the two countries have diverged in industry growth characteristics, with Australian dairying having contracted, with 10% less milk being produced because of 20% fewer cows producing 15% more per cow, whereas New Zealand dairying has expanded, producing 83% more milk driven by a 54% increase in cow numbers and a 31% increase in milk production per cow. Solutions to optimise feed efficiency included the common themes of (1) growing more forage on farm, (2) increasing its utilisation and (3) more efficient use of supplements resulting in increases in DM intake, and they remain relevant. In New Zealand, many of the recent research activities have aimed at improving feed supply while limiting environmental impacts driven by increasing societal concern surrounding the environmental footprint of a growing and intensifying agricultural sector. In Australia, many of the recent research activities have aimed at improving feed efficiency, with a focus on understanding situations where partial mixed ration feeding systems (Australian Farm Systems 3 and 4) are sustainable. Simply growing more feed on farm can no longer be a sole objective; farms must be operated with a view to reduce the environmental footprint, with New Zealand dairy farmers increasingly needing to farm within nitrogen limits. The present review revisits and reinforces many of the concepts developed in previous reviews, but also examines the evolution of feeding systems in both countries and opportunities to improve feed efficiency and profit, while satisfying public expectations around environmental stewardship. We also identify some of the gaps in the current knowledge that warrant further research.

Metabolic profiles of cow's blood; a review

The term 'metabolic profile' refers to the analysis of blood biochemical parameters that are useful to assess and prevent metabolic and nutritional disorders in dairy herds. In the higher standards of milk production, the priority in modern breeding is keeping dairy cows in high lactation and healthy. The proper analysis, as well as control. of their feeding and metabolic status is immensely important for the health condition of the herd. The disproportion between the genetically determined ability for milk production and the limitations in improving the energy value of the ration may be the cause of metabolic disorders. Negative energy balance has a major impact on the body's hormonal balance and organ functions and mostly appears during transition periods: from 3 to 2 weeks prepartum until 2-3 weeks postpartum. The term 'transition' is used to underscore the important physiological, metabolic and nutritional changes occurring in this time. The manner in which these changes occur and how they are diagnosed and detected are extremely important, as they are closely related to clinical and subclinical postpartum diseases, lactation and reproductive performance - factors that significantly shape the profitability of production. Therefore the priority for intensive milk production is prevention of metabolic diseases and other disorders. It is the intent of this review to synthesize and summarize the information currently available on metabolic status and physiological changes in the cow's body that occur during lactation, as well as to discuss the interpretation of the results, which will be a useful diagnostic tool in nutritional evaluations of the dairy herd. © 2016 Society of Chemical Industry.

Effect of calcium salts of fatty acids and calcium salt of methionine hydroxy analogue on reproductive responses and milk production in Holstein-Friesian cows

The effects of a dietary supplement with calcium salts of fatty acids and methionine hydroxy analogue on reproductive performance, blood metabolites, milk production, milk composition, body weight and body condition score was studied in lactating dairy cows. Autumn-calving, Holstein-Friesian cows (no. = 162) were assigned 1 week post calving to one of two diets: (1) unsupplemented maize-silage-based complete diet while housed before turn-out to perennial ryegrass pasture and (2) the same diet with 400 g per cow per day of a supplement with calcium salts of long-chain fatty acids and methionine hydroxy analogue (Megalac Plus, Volac Ltd). Eleven cows were removed from the study following randomization for reasons not related to the experiment leaving 151 cows on dietary treatments. The diets were offered until the end of the 18-week breeding period. Cows receiving supplement had higher milk yield and milk lactose production and lower milk protein and milk fat proportion (P < 0·05). Body weight and body condition scores were not different between treatments in the first 20 weeks of lactation (P > 0·05). Overall reproductive performance was not different between dietary treatments (P > 0·05). However, first lactation animals (no. = 33) receiving the dietary lipid and methionine supplement tended to have increased conception rates to first and second service (P < 0·09) which resulted in a shorter calving-to-conception interval in those animals (P < 0·06). Services per conception (P < 0·08), services per cow served (P < 0·05) and services per conception for pregnant cows (P < 0·05) in first lactation animals was reduced in the supplemented group. Although plasma cholesterol concentrations were increased following lipid and methionine supplementation (P < 0·01), plasma progesterone concentrations on day 5 and day 8 after artificial insemination were not different between dietary treatments (P > 0·05). In conclusion, a dietary supplement of calcium salts of fatty acids and methionine hydroxy analogue increased milk yield, milk lactose production and blood cholesterol concentration but did not improve reproductive performance, except in first lactation cows.

Effect of rumen degradable protein with or without fermentable carbohydrate supplementation on blood metabolites and embryo survival in cattle

High intakes of dietary protein, particularly rumen degradable protein (RDP), lead to elevations in systemic concentrations of ammonia and (or) urea and these may be increased further if associated with inadequate fermentable energy intake. High systemic concentrations of ammonia and urea have been associated with reduced reproductive performance in cattle. The objective of this study was to examine the effect of RDP and fermentable energy intake on a range of blood metabolites and on embryo survival in heifers. Oestrous synchronized, nulliparous beef heifers (no. = 162) were randomly assigned in a 2 ✕ 2 factorial designed experiment to two levels of RDP and two levels of fermentable energy. Grass silage-based diets were supplemented with either 0 (0U) or 240 (240U) g dietary urea (460 g/kg N) and these in turn with either 0 (0P) or 3 (3P) kg dry matter of molassed sugar-beet pulp pellets (MSBP) per day. The four treatments were, therefore, (1) 0U + 0P (no. = 43), (2) 0U + 3P (no. = 44), (3) 240U + 0P (no. = 40) (4) 240U + 3P (no. = 35), respectively. Systemic concentrations of ammonia, urea, insulin, glucose and progesterone were measured. Heifers were given artificial insemination (AI) and embryo survival measured by ultrasonography at 30 and again at 40 days after AI. Systemic ammonia and urea were elevated (P < 0·001) in the animals given the high RDP diets. Supplementation with MSBP reduced systemic urea in the heifers on both high and low RDP diets. Plasma ammonia concentrations were not affected by MSBP supplementation (P > 0·05). Plasma glucose was not affected by urea or MSBP treatment (P > 0·05) but was affected by day and time of sampling (P > 0·05). Plasma concentration of insulin was not affected by urea or MSBP supplementation or by day or time of sampling (P > 0·05). Plasma concentration of progesterone was not affected by diet or time of sampling (P > 0·05). The overall embryo survival rate was 62% and was not affected by dietary urea or fermentable carbohydrate or by systemic concentrations of ammonia, urea, glucose, insulin or progesterone (P > 0·05).

Effect of pasture crude protein and fermentable energy supplementation on blood metabolite and progesterone concentrations and on embryo survival in heifers

Seasonal milk production systems rely on heavy inputs of nitrogenous fertilizer, which typically generate pastures with a high crude protein (CP) and low fermentable energy concentration. High intake of CP, particularly in association with low rumen fermentable energy, increases systemic ammonia and urea and has been associated with reduced fertility in cattle. The objective of this study was to examine the relationship between pasture protein intake and fermentable energy supplementation on a range of blood metabolites and on embryo survival and development in cattle.

Oestrous synchronized, nulliparous beef heifers (no. = 175) were randomly assigned to one of four pasture-based dietary treatments in a 2✕2 factorial study carried out over 2 years. Animals were randomly allocated to either high (85 kg nitrogen (N) per ha; HN) or low (0·0 kg N per ha; LN) N fertilized pastures and within pasture treatment were randomly allocated to receive either zero or three (+3P) kg dry matter (DM) of molassed sugar-beet pulp (MSBP) per head per day as follows: (1) HN (no. = 44), (2) HN + 3P, (no. = 43), (3) LN (no. = 44), (4) LN + 3P (no. = 44). Blood samples were collected to measure systemic concentrations of ammonia, urea, insulin, glucose and progesterone. Heifers were artificially inseminated (AI) and pregnancy diagnosis was carried out by ultrasonography 30 days after AI. Subgroups of pregnant animals across treatments were slaughtered 40 days after AI to estimate conceptus development.

The HN pasture had a higher CP (P< 0·001) and lower water-soluble carbohydrate (P< 0·01) concentration. Plasma concentrations of ammonia (P< 0·05) and urea (P< 0·001) were higher in the animals on the HN pastures and were reduced (P< 0·05) by MSBP supplementation, but only in animals on the HN pastures. Embryo survival rate across treatments was high overall (71%) and not related to pasture CP concentration, fermentable energy supplementation or systemic concentrations of ammonia, urea, glucose or insulin. There was no relationship between dietary treatment or systemic metabolites and any of the estimates of conceptus development. Systemic insulin was not affected by pasture N treatment or MSBP supplementation (P> 0·05). Systemic concentrations of glucose were not affected by pasture N treatment (P> 0·05) but were increased by MSBP supplementation (P< 0·05). Systemic progesterone was not affected by pasture CP or MSBP supplementation (P> 0·05) but at day 7 after AI was positively related (P< 0·05) to embryo survival. Intake of high CP herbage elevated systemic ammonia and urea but there was no association with embryo survival rate or embryo development in heifers.

Milk production responses to different strategies for feeding supplements to grazing dairy cows

Milk production responses of grazing cows offered supplements in different ways were measured. Holstein-Friesian cows, averaging 45 d in milk, were allocated into 8 groups of 24, with 2 groups randomly assigned to each of 4 feeding strategies. These were control: cows grazed a restricted allowance of perennial ryegrass pasture supplemented with milled wheat grain fed in the milking parlor and alfalfa hay offered in the paddock; FGM: same pasture and allowance as the control supplemented with a formulated grain mix containing wheat grain, corn grain, and canola meal fed in the parlor and alfalfa hay fed in the paddock; PMRL: same pasture and allowance as the control, supplemented with a PMR consisting of the same FGM but mixed with alfalfa hay and presented on a feed pad after each milking; and PMRH: same PMR fed in the same way as PMRL but with a higher pasture allowance. For all strategies, supplements provided the same metabolizable energy and grain:forage ratio [75:25, dry matter (DM) basis]. Each group of 24 cows was further allocated into 4 groups of 6, which were randomly assigned to receive 8, 12, 14, or 16 kg of DM supplement/cow per d. Thus, 2 replicated groups per supplement amount per dietary strategy were used. The experiment had a 14-d adaptation period and a 14-d measurement period. Pasture allowance, measured to ground level, was approximately 14 kg of DM/d for control, FGM, and PMRL cows, and 28 kg of DM/d for the PMRH cows, and was offered in addition to the supplement. Positive linear responses to increasing amounts of supplement were observed for yield of milk, energy-corrected milk, fat, and protein for cows on all 4 supplement feeding strategies. Production of energy-corrected milk was greatest for PMRH cows, intermediate for FGM and PMRL cows, and lowest for control cows. Some of these differences in milk production related to differences in intake of pasture and supplement. Milk fat concentration decreased with increasing amount of supplement for all feeding strategies, but the decline was most marked for the control cows. Milk protein concentration increased for all groups as the amount of supplement increased, but was greater for FGM, PMRL, and PMRH cows than control cows. It is concluded that when supplements are fed to grazing dairy cows, inclusion of corn grain and canola meal can increase milk production even at similar metabolizable energy intakes, and that it does not matter whether these supplements are fed as a PMR or in the parlor and paddock.

Relationships between Circulating Urea Concentrations and Endometrial Function in Postpartum Dairy Cows

Simple Summary

Dairy cows fed high levels of protein to increase milk yield tend to have reduced fertility but the reasons behind this are unclear. Differing dietary protein levels are reflected in altered urea concentrations in both blood and other tissues including the uterus. We showed that the circulating urea concentration was highly correlated to changed expression levels of many genes in the endometrium shortly after calving. These were predominantly associated with tissue repair, innate immunity and lipid metabolism. A subsequent study found no effect of altered urea concentration on endometrial gene expression in vitro implying that the dietary influence is indirect.

Abstract

Both high and low circulating urea concentrations, a product of protein metabolism, are associated with decreased fertility in dairy cows through poorly defined mechanisms. The rate of involution and the endometrial ability to mount an adequate innate immune response after calving are both critical for subsequent fertility. Study 1 used microarray analysis to identify genes whose endometrial expression 2 weeks postpartum correlated significantly with the mean plasma urea per cow, ranging from 3.2 to 6.6 mmol/L. The biological functions of 781 mapped genes were analysed using Ingenuity Pathway Analysis. These were predominantly associated with tissue turnover (e.g., BRINP1, FOXG1), immune function (e.g., IL17RB, CRISPLD2), inflammation (e.g., C3, SERPINF1, SERPINF2) and lipid metabolism (e.g., SCAP, ACBD5, SLC10A). Study 2 investigated the relationship between urea concentration and expression of 6 candidate genes (S100A8, HSP5A, IGF1R, IL17RB, BRINP1, CRISPLD2) in bovine endometrial cell culture. These were treated with 0, 2.5, 5.0 or 7.5 mmol/L urea, equivalent to low, medium and high circulating values with or without challenge by bacterial lipopolysaccharide (LPS). LPS increased S100A8 expression as expected but urea treatment had no effect on expression of any tested gene. Examination of the genes/pathways involved suggests that plasma urea levels may reflect variations in lipid metabolism. Our results suggest that it is the effects of lipid metabolism rather than the urea concentration which probably alter the rate of involution and innate immune response, in turn influencing subsequent fertility.

Effect of nutritional status on the ovarian follicular population, yield and quality of oocytes in the Ngaoundere Gudali zebu (Bos indicus)

Aim:

The aim of this study was to investigate the effect of nutritional status of the Gudali cows slaughtered at the Ngaoundere abattoir on follicular population, quality, and oocytes yield.

Materials and Methods:

Blood and ovaries were collected from 81 cows aged 6.35±0.24 years (3-12 years old), with a body condition score (BCS) of 2.93±0.09 (1-5). In each ovary, the follicle were counted and classified as small (<3 mm), medium (3-8 mm) and large (>8 mm) using an electronic caliper. Oocytes were collected by slicing technique and classified according to the homogeneity of the cytoplasm and layers of granulosa into four groups: I, II, III, and IV. The nutritional status of the animals was determined by quantification of serum glucose, total cholesterol, total protein, albumin, globulins, urea, and phosphorus level.

Results:

Of the total 162 ovaries harvested, 2916 follicles were counted on the ovarian surface with an average population of 36.00±2.17 follicles/cow. According to a size distribution, 16.67±1.54 (46.3%), 18.83±1.27 (52.3%), and 0.51±0.07 (1.4%), respectively for small (<3 mm), medium (3-8 mm), and large (>8 mm) were recorded. About 1,929 oocytes were obtained, with an average recovered of 23.81±1.53 oocytes/cow. Depending on the quality, 7.79±0.55 (32.7%), 6.04±0.41 (25.3%), 4.89±0.44 (20.6%), and 5.10±0.54 (21.4%) oocytes qualities I, II, III, and IV were obtained respectively; with an average cultivable oocyte recovered of 13.83±0.89 (58%). Cows with BCS > 3 and a high albumin and phosphorus level showed a highest number of follicles and oocytes able for in vitro maturation.

Conclusion:

These results indicated that nutrition remains an important factor for the in vitro production of the good embryo and the BCS is a useful tool for the selection of females’ oocytes donors.

Non-enzymatic detection of urea using unmodified gold nanoparticles based aptasensor

Biosensing nitrogenous compounds like urea is required to control the incidents of Economically Motivated Adulteration (EMA). In this study, we report the FluMag Systematic Evolution of Ligands by Exponential Enrichment (FluMag-SELEX) method to isolate a urea specific DNA aptamer with a dissociation constant (Kd) of 232 nM. The interaction of DNA aptamer with urea has been confirmed by affinity assay, CD analysis, melting curve analysis and truncation studies. Unlike other urea sensing methods reported so far, using this urea aptamer, we demonstrate a simple, 'non-enzymatic' easy-to-use, dual readout aptasensor that exploits unmodified gold nanoparticles (AuNPs) to transduce the signals of aptamer binding to urea in terms of intrinsic fluorescence differences and color changes simultaneously. This method is free from complicated sample processing and labeling steps. The urea aptasensor displays high selectivity for urea and is free from interference from common milk adulterants. The developed aptasensor reliably detects urea adulteration in milk. The response signals linearly correlate with the increasing concentrations of urea in milk ranging from 20mM to 150 mM with detection limit of 20mM. We also show that this aptasensor can also be used as a simple fluorescence based "turn-on" sensor. The results obtained in this study are comparable to the commercial urease based detection methods.

Efeito da adição de teores crescentes de ureia na cana-de-açúcar em dietas de vacas em lactação sobre a produção e composição do leite e viabilidade econômica

Avaliou-se o efeito da adição de teores crescentes de ureia (0,0; 0,5 e 1,0%) na matéria natural da cana-de-açúcar sobre a produção e composição do leite, eficiência alimentar e viabilidade econômica. Foram utilizadas 18 vacas em lactação, com produção média inicial de 21,3±0,8kg/dia de leite e com 83±7 dias em lactação, distribuídas em delineamento ensaio de reversão do tipo switch-back, 3x3. As dietas experimentais foram constituídas de cana-de-açúcar como volumoso único e concentrado, na relação de 50:50 (base MS). Não houve efeito da suplementação dos diferentes teores de ureia sobre a produção e composição do leite. Contudo, a eficiência alimentar (produção de leite/consumo de matéria seca) foi melhor nas dietas em que se utilizou ureia, sendo 1,14; 1,17 e 1,17, respectivamente, para as dietas com 0,0; 0,5 e 1,0% de ureia (P<0,05). Considerando-se apenas o custo alimentar, todas as dietas apresentaram saldo positivo, sendo que a dieta com 1,0% de ureia apresentou o melhor saldo.

Invited review: An evaluation of the likely effects of individualized feeding of concentrate supplements to pasture-based dairy cows

In pasture-based dairy systems, supplementary feeds are used to increase dry matter intake and milk production. Historically, supplementation involved the provision of the same amount of feed (usually a grain-based concentrate feed) to each cow in the herd during milking (i.e., flat-rate feeding). The increasing availability of computerized feeding and milk monitoring technology in milking parlors, however, has led to increased interest in the potential benefits of feeding individual cows (i.e., individualized or differential feeding) different amounts and types of supplements according to one or more parameters (e.g., breeding value for milk yield, current milk yield, days in milk, body condition score, reproduction status, parity). In this review, we consider the likely benefits of individualized supplementary feeding strategies for pasture-based dairy cows fed supplements in the bail during milking. A unique feature of our review compared with earlier publications is the focus on individualized feeding strategies under practical grazing management. Previous reviews focused primarily on research undertaken in situations where cows were offered ad libitum forage, whereas we consider the likely benefits of individualized supplementary feeding strategies under rotational grazing management, wherein pasture is often restricted to all or part of a herd. The review provides compelling evidence that between-cow differences in response to concentrate supplements support the concept of individualized supplementary feeding.

Effects of protein supplementation frequency on physiological responses associated with reproduction in beef cows

The objective of this experiment was to determine if frequency of protein supplementation impacts physiological responses associated with reproduction in beef cows. Fourteen nonpregnant, nonlactating beef cows were ranked by age and BW and allocated to 3 groups. Groups were assigned to a 3 × 3 Latin square design, containing 3 periods of 21 d and the following treatments: 1) soybean meal supplementation daily (D), 2) soybean meal supplementation 3 times/week (3WK), and 3) soybean meal supplementation once/week (1WK). Within each period, cows were assigned to an estrus synchronization protocol: 100 μg of GnRH + controlled internal drug release device (CIDR) containing 1.38 g of progesterone (P4) on d 1, 25 mg of PGF2α on d 8, and CIDR removal + 100 μg of GnRH on d 11. Grass-seed straw was offered for ad libitum consumption. Soybean meal was individually supplemented at a daily rate of 1 kg/cow (as-fed basis). Moreover, 3WK was supplemented on d 0, 2, 4, 7, 9, 11, 14, 16, and 18 whereas 1WK was supplemented on d 4, 11, and 18. Blood samples were collected from 0 (before) to 72 h after supplementation on d 11 and 18 and analyzed for plasma urea-N (PUN). Samples collected from 0 to 12 h were also analyzed for plasma glucose, insulin, and P4 (d 18 only). Uterine flushing fluid was collected concurrently with blood sampling at 28 h for pH evaluation. Liver biopsies were performed concurrently with blood sampling at 0, 4, and 28 h and analyzed for mRNA expression of carbamoyl phosphate synthetase I (CPS-I; h 28) and CYP2C19 and CYP3A4 (h 0 and 4 on d 18). Plasma urea-N concentrations were greater (P < 0.01) for 1WK vs. 3WK from 20 to 72 h and greater (P < 0.01) for 1WK vs. D from 16 to 48 h and at 72 h after supplementation (treatment × hour interaction, P < 0.01). Moreover, PUN concentrations peaked at 28 h after supplementation for 3WK and 1WK (P < 0.01) and were greater (P < 0.01) at this time for 1WK vs. 3WK and D and for 3WK vs. D. Expression of CPS-I was greater (P < 0.01) for 1WK vs. D and 3WK. Uterine flushing pH tended (P ≤ 0.10) to be greater for 1WK vs. 3WK and D. No treatment effects were detected (P ≥ 0.15) on expression of CYP2C19 and CYP3A4, plasma glucose, and P4 concentrations, whereas plasma insulin concentrations were greater (P ≤ 0.03) in D and 3WK vs. 1WK. Hence, decreasing frequency of protein supplementation did not reduce uterine flushing pH or plasma P4 concentrations, which are known to impact reproduction in beef cows.

Electronic monitoring of rumination activity as an indicator of health status and production traits in high-yielding dairy cows

In view of the demonstrated relationship between rumination time and health status, the general welfare and metabolic condition of ruminants are often assessed by the examination of rumen function. The main goal of this study was to monitor the daily rumination activity (RA) and its connection with actual liveweight (LW), milk yield (MY) and with two diseases (subclinical hyperketonaemia - SHK, uterine disease - UD) in 96 cows on the basis of a total of 1638 observations in Israel. The studied sample gave a highly significant response, showing that the selected diseases had a diminishing impact on RA and LW and no influence on MY. It can be concluded that the change of RA as determined by electronic monitoring, complemented by the change of LW, is a useful general indicator of health status and subclinical disease before the appearance of clinical signs.

A field study to unravel factors that are significantly associated with the secretory activity of the corpus luteum during the first three postpartum cycles in high yielding dairy cows, based on the amount of steroidogenic and endothelial cells present in the luteal tissue

Fourteen multi- and eight primiparous high-yielding dairy cows were followed from the first till the fourth ovulation postpartum. Cows were randomly divided into two groups and supplemented with soybean (group I; n = 11) or rapeseed meal (group II; n = 11). Both groups were subjected to a biopsy sampling of the corpus luteum (CL) at cycle day 9. The luteal capillary network (visualized by Bandeiraea simplicifolia) was denser in cycles 2 and 3 (p = 0.0005). The same was seen for the surface occupied by steroidogenic cells (visualized by 3β-hydroxysteroiddehydrogenase) (p = 0.0001). The peripheral blood progesterone concentration showed an increasing trend with increasing cycle number and was higher in primiparous cows (p = 0.013), which had also larger glands on cycle day 9. The area occupied by endothelial cells was positively correlated with the area occupied by steroidogenic cells (r = 0.59; p < 0.0001). Both the areas occupied by endothelial and by steroidogenic cells were negatively correlated with the blood concentration of nonesterified fatty acids (NEFAs) (respectively, r = -0.377; p = 0.004 and r = -0.355; p = 0.007). We can conclude that primiparous cows generally have higher peripheral progesterone levels during the first three cycles after calving which is associated with a larger CL. In comparison with those of the first post-partum cycle, corpora lutea of cycles 2 and 3 have a denser capillary network and a larger area of steroidogenic cells, while these are only associated with a trend of higher peripheral progesterone concentrations.

Cell proliferation and progesterone synthesis depend on lipid metabolism in bovine granulosa cells

In dairy cows, lipids are essential to support energy supplies for all biological functions, especially during early lactation. Lipid metabolism is crucial for sustaining proper reproductive function. Alteration of lipid metabolism impacts follicular development and affects oocyte developmental competence. Indeed, nonesterified fatty acids are able to decrease granulosa cell (GC) proliferation and affect estradiol synthesis, thus potentially affecting follicular growth and viability. The objective of this study was to assess the impact of lipid metabolism on bovine GCs, through the use of the lipid metabolism inhibitors etomoxir, an inhibitor of fatty acid (FA) oxidation through inhibition of carnitine palmitoyl transferase 1 (CPT1), and C75, an inhibitor of FA synthesis through inhibition of fatty acid synthase. We showed that etomoxir and C75 significantly inhibited DNA synthesis in vitro; C75 also significantly decreased progesterone synthesis. Both inhibitors significantly reduced AMPK (5' adenosine monophosphate-activated protein kinase) and acetyl-CoA carboxylase phosphorylation. Etomoxir also affected the AKT (protein kinase B) signaling pathway. Combined, these data suggest that both FA oxidation and synthesis are important for the bovine GCs to express a proliferative and steroidogenic phenotype and, thus, for sustaining follicular growth. Despite these findings, it is important to note that the changes caused by the inhibitors of FA metabolism on GCs in vitro are globally mild, suggesting that lipid metabolism is not as critical in GCs as was observed in the oocyte-cumulus complex. Further studies are needed to investigate the detailed mechanisms by which lipid metabolism interacts with GC functions.

Effects of propylene glycol supplementation on blood indicators of hepatic function, body condition score, milk fat-protein concentration and reproductive performance of dairy cows

The aim of the present study was to determine the effects of propylene glycol on metabolic variables of hepatic function, body condition score, milk fat-protein concentration and reproductive performance of dairy cows after ending administration. Postparturient dairy cows (n = 200) of Holstein Friesian breed were divided into two groups of 100 individuals. The experimental group received during days 0-7 post partum an oral daily dose of 600 ml of propylene glycol; the control group was without any supplement. The hepatic enzymes, glucose, cholesterol and serum albumin were measured on days 10-15, 45-50 and 70 post partum. Reproduction indicators of dairy cows were calculated from the farm recording data and the milk data record from a regular dairy control (days 10, 20, 30, and 50 post partum). Animals that received propylene glycol in the first 7 days post partum had reduced activities of aspartate transaminase and gamma-glutamyl transferase, elevated cholesterol concentration (P < 0.05) and low milk fat percentage (P < 0.05) compared to control animals. Direct influence of propylene glycol drenching on the calving to first oestrus interval was observed, the smallest values being detected for the cows in the experimental group compared to the control group (P < 0.05). Our results suggest that some blood indicators of hepatic function, milk fat concentration and calving to first oestrus interval can be improved for 70 days post partum by the use of propylene glycol drenching in the first 7 days post partum. The beneficial effect of this treatment could be evaluated by easily available data, which can be used by practitioners in the field to analyze fertility problems in dairy herds and more exactly to examine whether metabolic stress, among other factors, is involved in the fertility problem.