Relationship of dietary crude protein to composition of uterine secretions and blood in high-producing postpartum dairy cows

The uterine secretory cycle: recurring physiology of endometrial outputs that setup the uterine luminal microenvironment

Conserved in female reproduction across all mammalian species is the estrous cycle and its regulation by the hypothalamic-pituitary-gonadal (HPG) axis, a collective of intersected hormonal events that are crucial for ensuring uterine fertility. Nonetheless, knowledge of the direct mediators that synchronously shape the uterine microenvironment for successive yet distinct events, such as the transit of sperm and support for progressive stages of preimplantation embryo development, remain principally deficient. Toward understanding the timed endometrial outputs that permit luminal events as directed by the estrous cycle, we used Bovidae as a model system to uniquely surface sample and study temporal shifts to in vivo endometrial transcripts that encode for proteins destined to be secreted. The results revealed the full quantitative profile of endometrial components that shape the uterine luminal microenvironment at distinct phases of the estrous cycle (estrus, metestrus, diestrus, and proestrus). In interpreting this comprehensive log of stage-specific endometrial secretions, we define the "uterine secretory cycle" and extract a predictive understanding of recurring physiological actions regulated within the uterine lumen in anticipation of sperm and preimplantation embryonic stages. This repetitive microenvironmental preparedness to sequentially provide operative support was a stable intrinsic framework, with only limited responses to sperm or embryos if encountered in the lumen within the cyclic time period. In uncovering the secretory cycle and unraveling realistic biological processes, we present novel foundational knowledge of terminal effectors controlled by the HPG axis to direct a recurring sequence of vital functions within the uterine lumen.NEW & NOTEWORTHY This study unravels the recurring sequence of changes within the uterus that supports vital functions (sperm transit and development of preimplantation embryonic stages) during the reproductive cycle in female Ruminantia. These data present new systems knowledge in uterine reproductive physiology crucial for setting up in vitro biomimicry and artificial environments for assisted reproduction technologies for a range of mammalian species.

The Impacts of Supplemental Protein during Development on Amino Acid Concentrations in the Uterus and Pregnancy Outcomes of Angus Heifers

Replacement heifer development is one of the most critical components in beef production. The composition of the ideal uterine environment could maximize fertility and reproductive efficiency. Our hypothesis was that protein supplementation would affect the uterine environment of beef heifers without inhibiting development or reproduction. To test the effects of dietary supplementation on these outcomes, a randomized complete block design with repeated measures was implemented. Angus heifers (n = 60) were blocked by body weight (BW) and randomly assigned to one of three supplemental protein treatment groups (10% (CON), 20% (P20), and 40% (P40)). Mixed model ANOVAs were used to determine whether protein supplementation treatments, time, and the interaction or protein supplementation, semen exposure, and the interaction influenced uterine luminal fluid (ULF) and pregnancy outcomes. Amino acids (AAs) were impacted (p < 0.001), specifically, the essential AAs: Arg, Iso, Leu, Val, His, Lys, Met, Phe, Trp. Protein supplementation influenced multiple AAs post-insemination: Arg (p = 0.03), CC (p = 0.05), 1-MH (p = 0.001), and Orn (p = 0.03). In conclusion, protein supplementation did not affect the reproductive development via puberty attainment or the timing of conception even with alterations in growth. However, uterine AA concentrations did change throughout development and protein supplementation influenced ULF d 14 post-insemination, which may affect the conception rates.

Elevated blood urea nitrogen alters the transcriptome of equine embryos

High blood urea nitrogen (BUN) in cows and ewes has a negative effect on embryo development; however, no comparable studies have been published in mares. The aims of the present study were to evaluate the effects of high BUN on blastocoele fluid, systemic progesterone and Day 14 equine embryos. When a follicle with a mean (±s.e.m.) diameter of 25±3mm was detected, mares were administered urea (0.4g kg-1) with sweet feed and molasses (n=9) or sweet feed and molasses alone (control; n=10). Blood samples were collected every other day. Mares were subjected to AI and the day ovulation was detected was designated as Day 0. Embryos were collected on Day 14 (urea-treated, n=5 embryos; control, n=7 embryos). There was an increase in systemic BUN in the urea-treated group compared with control (P<0.05), with no difference in progesterone concentrations. There were no differences between the two groups in embryo recovery or embryo size. Urea concentrations in the blastocoele fluid tended to be higher in the urea-treated mares, with a strong correlation with plasma BUN. However, there was no difference in the osmolality or pH of the blastocoele fluid between the two groups. Differentially expressed genes in Day 14 embryos from urea-treated mares analysed by RNA sequencing were involved in neurological development, urea transport, vascular remodelling and adhesion. In conclusion, oral urea treatment in mares increased BUN and induced transcriptome changes in Day 14 equine embryos of genes important in normal embryo development.

A low protein maternal diet during gestation has negative effects on male fertility markers in rats - A Systematic Review and Meta-analysis

Research indicates that some adult diseases including reproductive pathologies are programmed in utero during foetal development. In particular, maternal low dietary protein, during the most critical developmental periods of male foetal development, may have a detrimental impact on male fertility through direct and epigenetic mechanisms. The aim of our study was to evaluate the impact of a gestational low protein diet on fertility markers in male offspring in rats through a systematic review and meta-analysis. A systematic search using PubMed, and EMBASE databases was performed and two investigators independently screened the 1,703 prospective articles. Eleven articles met the eligibility criteria. Outcome measures were pooled using random-effects models and expressed as mean differences (MDs) at 95% CIs for each study. The results reveal significant reduction in testis weight (MD (mean difference) -0.08 g; -0.12, -0.42; p = .0001), epididymal sperm count (MD -35.34 × 10⁶ cells; -52.15, -18.53; p = .0001), number of Sertoli cells (MD -7.27 × 10⁶ (-13.92, -0.62; p = .03), testosterone (T) concentration (MD -0.29 ng/ml; -0.48, -0.09; p = .004) and luteinising hormone (LH) concentration (MD of -0.24 ng/ml; -0.45, 0.04; p = .02) in comparison with controls. In contrast, follicle-stimulating hormone (FSH) concentration (MD of 0.07 ng/ml; -0.16, 0.29; p = .56) was not significantly different from controls. We conclude that low gestational dietary protein maternal intake potentially negatively impacts fertility in male progeny later in life. The mechanisms of action responsible for these phenomena remain unclear.

Relationship between concentrations of macro and trace elements in serum and follicular, oviductal, and uterine fluids of the dromedary camel (Camelus dromedarius)

This study aimed at investigating the relationship between concentrations of macro and trace elements in blood serum, and fluids from small and large follicles (SFF and LFF, respectively), oviduct (OF), and uterus (UF) of female dromedary camels. Fluids from small (2-6 mm) and large follicles (7-20 mm), oviduct and uterus, and blood samples were collected from 19 camels. The results indicated that the concentrations of serum Mg, Fe, and Mn were significantly higher than their follicular fluid, OF, and UF concentrations. Levels of Zn, Fe, Cu, Cr, and Mn were significantly higher in SFF than in LFF. Se and Mo concentrations were higher in LFF. Co concentration was lower in serum than in reproductive tract fluids. Cr concentration was higher in UF and OF than in the serum, SFF, and LFF. High Ca concentration was observed for serum and SFF, followed by LFF. The concentration of Na was about 1.18-fold higher in SFF than in serum, OF, and LFF, and approximately 4.1-fold higher in serum than in UF. K was present in higher concentration in SFF than in serum and LFF; however, its concentration was low in UF and OF. In conclusion, this study shows the concentrations of certain elements in small and large follicular, uterine, and oviductal fluids, which may be low or high depending on their function in the development and growth of follicles. This information can support the development of new media for in vitro oocyte maturation and fertilization of female camels.

A High Protein Model Alters the Endometrial Transcriptome of Mares

High blood urea nitrogen (BUN) decreases fertility of several mammals; however, the mechanisms have not been investigated in mares. We developed an experimental model to elevate BUN, with urea and control treatments (7 mares/treatment), in a crossover design. Urea-treatment consisted of a loading dose of urea (0.03 g/kg of body weight (BW)) and urea injections over 6 hours (0.03 g/kg of BW/h). Control mares received the same volume of saline solution. Blood samples were collected to measure BUN. Uterine and vaginal pH were evaluated after the last intravenous infusion, then endometrial biopsies were collected for RNA-sequencing with a HiSeq 4000. Cuffdiff (2.2.1) was used to identify the differentially expressed genes (DEG) between urea and control groups (false discovery rate-adjusted p-value < 0.1). There was a significant increase in BUN and a decrease of uterine pH in the urea group compared to the control group. A total of 193 genes were DEG between the urea and control groups, with five genes identified as upstream regulators (ETV4, EGF, EHF, IRS2, and SGK1). The DEG were predicted to be related to cell pH, ion homeostasis, changes in epithelial tissue, and solute carriers. Changes in gene expression reveal alterations in endometrial function that could be associated with adverse effects on fertility of mares.

Association of bulk tank milk urea nitrogen concentration with elevated individual cow values and investigation of sampling frequency for accurate assessment

Individual milk urea nitrogen (MUN) levels ≥ 19.63 mg/dL have been recently reported to significantly affect fertility. The objectives of the present study were to (a) predict the percentage of cows with elevated MUN within a herd using bulk tank (BTMUN) levels, in the absence of individual MUN records, and (b) establish a sampling frequency protocol for the assessment of actual BTMUN levels. A database of 17,687 monthly individual MUN and concurrent 229 monthly BTMUN records from 24 dairy herds was used. A ROC analysis was performed to determine the BTMUN threshold over which cows in the herd have elevated MUN concentrations that, based on literature, affect fertility. Moreover, a regression was run to predict the percentage of cows with elevated MUN within a herd from BTMUN values. A second database of 10,687 daily BTMUN records from 29 herds was used to identify an appropriate sampling frequency to assess the actual BTMUN levels. Eleven different sampling frequencies ranging from once to 8 times per month were assessed. A BTMUN value of 15.76 mg/dL was the optimum threshold over which cows with elevated MUN concentrations are included in a herd. The percentage of cows with elevated MUN values can be accurately predicted using BTMUN values (R² = 0.872; P < 0.001). A bulk tank sampling frequency of once per week seems appropriate for most herds in order to assess the actual BTMUN levels, in case daily BTMUN values are not available from milk processors.

Involvement of Quebracho tannins in diet alters productive and reproductive efficiency of postpartum buffalo cows

This study was conducted to investigate the effects of 10 weeks supplementation of Quebracho tannins (QT; 0 [control], 100 [QT100] or 200 g/[cow·d] [QT200]) to 30 multiparous postpartum buffalo cows (10 cows per group) on milk yield and composition, blood metabolites and reproductive performance. Supplementation of QT100 had no significant effect on milk yield, whereas QT200 decreased (P < 0.05) this trait. Compared with the control group, both QT levels decreased (P < 0.05) fat-corrected milk (FCM) yield, but no significant effects were found on percentages of milk fat and protein. Contrariwise, yields of milk fat, lactose and milk protein were decreased (P < 0.05) when QT200 was supplemented. The solids nonfat (SNF) percentage and yield were decreased (P < 0.05) with QT100 supplementation. Moreover, QT tended to numerically reduce total number of ovarian follicles, number of small follicles, peripheral progesterone concentration and conception rate. Supplementation of QT200 numerically increased number of large follicles, mean diameter of large follicle, number and diameters of corpora lutea. The inclusion of QT200 shortened days open (DO) and decreased number of services per conception. Contrariwise, QT did not show significant effects on serum total protein, albumin, globulin, glucose, cholesterol and triglycerides concentrations. Supplementation of QT100 caused an increase (P < 0.05) of serum urea compared with that in control and QT200 groups. Generally, QT decreased (P < 0.05) serum creatinine concentration. Therefore, the supplementation of a commercial QT to early lactating Egyptian buffalo cows displayed negative consequences on their productive and reproductive performances.

Silage review: Animal and human health risks from silage

Silage may contain several agents that are potentially hazardous to animal health, the safety of milk or other animal food products, or both. This paper reviews published literature about microbial hazards, plant toxins, and chemical hazards. Microbial hazards include Clostridium botulinum, Bacillus cereus, Listeria monocytogenes, Shiga toxin-producing Escherichia coli, Mycobacterium bovis, and various mold species. High concentrations of C. botulinum in silage have been associated with cattle botulism. A high initial concentration of C. botulinum spores in forage in combination with poor silage fermentation conditions can promote the growth of C. botulinum in silage. The elevated pH level that is generally associated with aerobic deterioration of silage is a major factor influencing concentrations of L. monocytogenes, Shiga toxin-producing E. coli, and molds in silage and may also encourage survival and growth of M. bovis, the bacterium that causes bovine tuberculosis. Soil is a major source of B. cereus spores in silage; growth of this bacterium in silage appears to be limited. Hazards from plant toxins include pyrrolizidine, tropane and tropolone alkaloids, phytoestrogens, prussic acid, and mimosine, compounds that exist naturally in certain plant species that may contaminate forages at harvesting. Another group of toxins belonging to this category are ergot alkaloids, which are produced by endophytic fungal species in forages such as tall fescue grass, sorghum, and ryegrass. Varying effects of ensiling on the degradation of these plant toxins have been reported. Chemical hazards include nitrate, nitrite, and toxic oxide gases of nitrogen produced from nitrate and high levels of butyric acid, biogenic amines, and ammonia. Chemical and microbiological hazards are associated with poorly fermented silages, which can be avoided by using proper silage-making practices and creating conditions that promote a rapid and sufficient reduction of the silage pH and prevent aerobic deterioration.

Lactation response to soybean meal and rumen-protected methionine supplementation of corn silage-based diets

Corn silage, an important forage fed to dairy cows in the United States, is energy rich but protein poor. The objectives of this experiment were to investigate the effects on production of milk and milk components of feeding corn silage-based diets with 4 levels of dietary crude protein (CP) plus rumen-protected methionine (RPM). Thirty-six cows were blocked by days in milk into 9 squares and randomly assigned to 9 balanced 4 × 4 Latin squares with four 4-wk periods. All diets were formulated to contain, as a percent of dry matter (DM), 50% corn silage, 10% alfalfa silage, 4% soyhulls, 2.4% mineral-vitamin supplement, and 30% neutral detergent fiber. Supplemental RPM (Mepron, Evonik Corp., Kennesaw, GA) was added to all diets to maintain a Lys:Met ratio of 3.1 in digested AA. Ground high-moisture corn was reduced and soybean meal (SBM) plus RPM increased to give diets containing, on average, 11% CP (28% corn, 31% starch, 6% SBM, 4 g of RPM/d), 13% CP (23% corn, 29% starch, 10% SBM, 8 g of RPM/d), 15% CP (19% corn, 26% starch, 15% SBM, 10 g of RPM/d), and 17% CP (14% corn, 24% starch, 19% SBM, 12 g of RPM/d). Data from the last 14 d of each period were analyzed using the mixed procedures in SAS (SAS Institute Inc., Cary, NC). With the exception of milk fat and milk lactose content, we found no significant effects of diet on all production traits. We did note linear responses to dietary CP concentration for intake, production of milk and milk components, and MUN. Cows fed the 11% CP diet had reduced DM intake, lost weight, and yielded less milk and milk components. Mean separation indicated that only true protein yield was lower on 13% CP than on 17% dietary CP, but not different between 15 and 17% CP. This indicated no improvement in production of milk and milk components above 15% CP. Quadratic trends for yield of milk, energy-corrected milk, and true protein suggested that a dietary CP concentration greater than 15% may be necessary to maximize production or, alternately, that a plateau was reached and no further CP was required. Although diet influenced apparent digestibility of DM, organic matter, and neutral detergent fiber, digestibility did not increase linearly with dietary CP. However, we observed linear and quadratic effects of dietary CP on acid detergent fiber digestibility. As expected, we found a linear effect of dietary CP on apparent N digestibility and on fecal and urinary N excretion, but no effect of diet on estimated true N digestibility. Ruminal concentrations of ammonia, total AA, peptides, and branched-chain volatile fatty acids also increased linearly with dietary CP. Quadratic responses indicated that 14.0 to 14.8% CP was necessary to optimize digestion and energy utilization. Overall results indicated that, when RPM was added to increase Lys:Met to 3.1, 15% CP was adequate for lactating dairy cows fed corn silage diets supplemented with SBM and secreting about 40 kg of milk/d; N excretion was lower than at 17% CP but with no reduction in yield of milk and milk components.

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.

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).

The effects of dietary urea on embryo development in superovulated donor ewes and on early embryo survival and development in recipient ewes

The aim was to examine the effect of dietary urea on yield and quality of embryos in superovulated donor ewes, and on embryo survival in recipient ewes. Ewes (25 donors and 34 recipients) were offered 1·25 kg of grass meal containing 50 g urea per ewe per day on a group basis; the remaining ewes (30 donors and 32 recipients) received 1·25 kg untreated grass meal per day. After 5 days, ewes were synchronized using a progestagen pessary for 14 days and stimulated with pregnant mare serum gonadotropin. Donors were naturally mated; recipients were detected in oestrus using vasectomized rams. On day 4 following the onset of oestrus, embryos were recovered from donors, graded morphologically and cell number counted. Two embryos of acceptable morphological grade (≥ eight cells on day 4) were then surgically transferred to recipient ewes. Recipients were slaughtered between days 34 and 36 post oestrus. The mean number of embryos recovered per ewe [3·68 (s.e. 0·41) v. 3·83 (s.e. 0·45)] was not different between untreated and urea-treated ewes, respectively. However, urea treatment of donor ewes reduced the mean cell number per embryo (10·27 (s.e. 0·27) v. 8·17 (s.e. 0·29) for untreated and urea-treated donor ewes, respectively, P < 0·001). Similarly, the percentage of embryos recovered that had ≥ 10 cells and their mean cell number was reduced following urea treatment of donor ewes (82/113 (73%) v. 39/93 (42%), P < 0·01 and 11·61 (s.e. 0·20) v. 10·41 (s.e. 0·29), P < 0·001) for untreated and urea-treated ewes, respectively. The diet offered to recipient ewes had no effect on the number of ewes confirmed pregnant (24/32 (75%) v. 28/34 (82%)) or on embryo survival following transfer (45/64 (70%) v. 51/68 (75%) for untreated and urea-treated ewes, respectively, P > 0·05). Excess nonprotein nitrogen in the form of dietary urea reduced embryo quality. However, embryo survival in recipient ewes was not affected when good quality embryos were transferred. This suggests that the deleterious effects of excess dietary urea are due to alterations to the oocyte and (or) the oviductal environment rather than changes in the uterine environment.

Nutritional effects on ovulation, embryo development and the establishment of pregnancy in ruminants

The effects of high and low dietary dietary intake on reproduction in female cattle and sheep will be considered at the level of the pituitary gland, ovary and uterus. In sheep, increased dietary intake for a relatively short time will increase ovulation rate, by increasing gonadotropin secretion. Dietary intake can affect steroids such as progesterone and also intra-follicular concentrations of some growth factors such as IGF-1 and IGF-2. The effects of altered energy intake on gonadotropins and steroids in cattle are not as repeatable as those in sheep but follicular growth rates can be altered. High nutrition has a negative effect on oocyte quality, with animals onad-libitumhigh energy diets particularly at risk. Overfeeding can decrease embryo quality in both sheep and cattle and it appears that this results from changes primarily at the level of the follicle or oocyte. Restricted nutrition for a short time will enhance pregnancy rates in cattle; most of this benefit appears to occur if food is restricted before insemination. Thus feeding levels before mating are particularly important to subsequent reproductive success. High dietary crude protein may decrease pregnancy rate in lactating cows. In ewes and heifers supplementation with urea failed to have any effect on pregnancy rates when good quality embryos were transferred to recipient animals exposed to high dietary crude protein. In donor ewes there were adverse effects on early embryo development following urea treatment, suggesting that the mechanism affecting the reproductive process was primarily operating at the level of the oocyte. Collectively, these data identify the overall deleterious effects of high dietary intake and excess crude protein on fertility and highlight the importance of dietary intake before ovulation on the likelihood of establishing a viable pregnancy.

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.

Multiple-embryo transfer for studying very early maternal-embryo interactions in cattle

In the present paper, we highlight the need to study very early maternal-embryo interactions and discuss how these interactions can be addressed. Bovine species normally carry one or, less frequently, two embryos to term; there are very rare cases of triplets or higher-order multiple pregnancies in which all the offspring are born alive. Multiple-embryo transfer (MET) in cattle allows for the detection of endometrial responses in scenarios where single-embryo transfer would not. Although MET is non-physiological, the present study shows that at the very early embryonic stages, a uterus carrying zona-enclosed embryos does not exhibit non-physiological reactions. On the contrary, MET should be considered the sum of multiple individual effects triggered by developing embryos. We provide arguments to support our hypothesis that describe a rationale for current work with MET, and we discuss alternative hypotheses. Using cattle as a model, we describe how technical approaches to analyzing zona-enclosed early embryo-maternal interactions (i.e., transcriptomics, proteomics, and endometrial cell culture) can help identify molecular changes that may be difficult to observe when only a single embryo is present. We conclude that MET can be used for studying very early maternal-embryo interactions in vivo in monotocous species. Free Spanish abstract: A Spanish translation of this abstract is freely available at http://www.reproduction-online.org/content/150/2/R35/suppl/DC1.

Japanese Black breeding herd exhibiting low blood urea nitrogen: a metabolic profile study examining the effect on reproductive performance

Ten reared cows of a Japanese Black cattle herd in Kagoshima prefecture, Japan, exhibited extremely low blood urea nitrogen (BUN) concentration (2.6 ± 0.6 mg/dL). Examination of dietary feed nutrition and relevant pastureland soil content suggested a correlation with crude protein (CP) deficiency or unbalanced nutritional dietary feeds. Thirteen months after the introduction of a dietary remedial measure (bean cake supplementation), BUN, total cholesterol and albumin concentration from five of the original 10 cows increased significantly compared with their values of before the dietary remedy. The postpartum day open period was significantly lower after the dietary remedial measure than that before it. The abnormally low BUN levels of the cattle herd may be due to inadequate dietary nutritional content, primarily from the imbalance of total digestible nutrient and CP of the feed and far lower han average CP value. In conclusion, routine examination of serum biochemical parameters in Japanese Black breeding cattle may be a useful strategy for determining subclinical metabolic failure of cattle herds, and consequently, its effect on reproductive performance of the herd.

Supplementation of dried distillers grains with solubles to beef cows consuming low-quality forage during late gestation and early lactation

Three experiments were conducted to evaluate supplementation of dried distillers grains with solubles (DGS) to spring-calving beef cows (n = 120; 541 kg of initial BW; 5.1 initial BCS) consuming low-quality forage during late gestation and early lactation. Supplemental treatments included (DM basis) 1) 0.77 kg/d DGS (DGSL); 2) 1.54 kg/d DGS (DGSI); 3) 2.31 kg/d DGS (DGSH); 4) 1.54 kg/d of a blend of 49% wheat middlings and 51% cottonseed meal (POS); and 5) 0.23 kg/d of a cottonseed hull-based pellet (NEG). Feeding rate and CP intake were similar for DGSI and POS. In Exp. 1, cows were individually fed 3 d/wk until calving and 4 d/wk during lactation; total supplementation period was 119 d, encompassing 106 d of gestation and 13 d of lactation. Tall-grass prairie hay (5.6% CP, 50% TDN, 73% NDF; DM basis) was fed for ad libitum intake throughout the supplementation period. Change in cow BW and BCS during gestation was similar for DGSI and POS (-5.0 kg, P = 0.61 and -0.13, P = 0.25, respectively) and linearly increased with increasing DGS level (P < 0.01). Likewise, during the 119-d supplementation period, BW and BCS change were similar for DGSI and POS (-72 kg, P = 0.22 and -0.60, P = 0.10) and increased linearly with respect to increasing DGS (P < 0.01). The percentage of cows exhibiting luteal activity at the beginning of breeding season (56%, P = 0.31), AI conception rate (57%, P = 0.62), or pregnancy rate at weaning (88%, P = 0.74) were not influenced by supplementation. In Exp. 2, 30 cows from a separate herd were used to evaluate the effect of DGS on hay intake and digestion. Supplementation improved all digestibility measures compared with NEG. Hay intake was not influenced by DGS (P > 0.10); digestibility of NDF, ADF, CP, and fat linearly increased with increasing DGS. In Exp. 3, milk production and composition were determined for cows (n = 16/treatment) of similar days postpartum from Exp. 1. Daily milk production was not influenced by supplementation (6.3 kg/d, P = 0.25). Milk fat (2.1%) and lactose (5.0%) were not different (P > 0.10). Milk protein linearly increased as DGS increased (P < 0.05) and was greater for DGSI compared with POS. Similar cow performance was achieved when cows were fed DGS at the same rate and level of CP as a traditional cottonseed meal-based supplement. Increasing amounts of DGS did not negatively influence forage intake or diet digestibility.

Efeito do nível nutricional antes e após a ovulação sobre a taxa de gestação e a prolificidade em ovelhas Santa Inês

Quarenta e três ovelhas foram distribuídas em quatro tratamentos em um delineamento de blocos casualizados. Os tratamentos consistiram no fornecimento de dietas de flushing, formuladas com farelo de soja (FFS) ou com glúten de milho e farelo de algodão (FGM+FA) por 28 dias antes da ovulação, seguido pelo fornecimento de dietas de flushing ou de uma dieta de mantença (DM) durante 28 dias após a ovulação: T1 - FFS antes e após a ovulação (n=12); T2 - FFS antes da ovulação e DM após (n=11); T3 - FGM+FA antes e após a ovulação (n=10); T4 - FGM+FA antes da ovulação e DM após (n=10). O ganho de peso e o peso final não diferiram (P>0,05) entre os animais dos tratamentos. O ECC final foi maior (P<0,05) nas ovelhas do tratamento T3 do que nas do tratamento T2. A concentração de N-ureico foi maior (P<0,05) nas ovelhas dos tratamentos T1 e T3 do que naquelas dos tratamentos T2 e T4. A taxa de gestação e a prolificidade não diferiram (P>0,05) entre os animais. As dietas de flushing antes da ovulação, seguidas pelo fornecimento destas mesmas dietas ou de uma dieta de mantença após a ovulação, não alteraram a taxa de gestação e a prolificidade.

Nutrition × reproduction interaction in pasture-based systems: is nutrition a factor in reproductive failure?

Dairy cow fertility has declined in recent decades, coincidental with large increases in milk production. Cows take longer to return to oestrus, display poorer signs of oestrus, have greater early embryo loss, and may have poorer conception rates. The problem is often considered to be nutritional, at least in part, and, therefore, can be corrected through dietary adjustment. Although acknowledged as highly digestible, high quality pastured forages tend to be low in non-structural carbohydrates (NSC), high in rumen degradable protein and the temporal supply may not be adequate for cow demand at key times; diet adjustment is often recommended to overcome these limitations. The interaction between nutrition and reproduction is poorly defined, however, and study results are often contradictory. Hypothesised limitations to pastured forages within a grazing system will be discussed, and the likely impact of nutritional adjustment on pre- and post-ovulatory reproductive processes examined. The effect of energy balance, carbohydrate type, protein and fat on reproductive outcomes will be considered. Nutrition is an important component of successful reproduction, but dietary adjustment to improve pregnancy rates is complicated, and merely offering pastured cows a supplement is unlikely to result in large effects. Conclusions indicate that care must be taken in interpreting associative analyses and in applying results from different farming systems.

Effects of supplementation with digestible undegradable protein in late pregnancy on ewe colostrums production and lamb output to weaning

The aim of this study was to investigate the effects of supplementation with digestible undegradable protein (DUP) in diet during late pregnancy on colostrum production, lamb survival and growth. For 3 weeks prior to lambing, 41 Afshari ewes were assigned at random to three dietary treatments, namely a control (CDUP), moderate (MDUP) and high (HDUP) DUP group. The ewes (n = 14) in CDUP group were fed a protein maintenance level for pregnant ewes [83 g metabolizable protein (MP)/kg dry matter (DM)], while ewes in the MDUP (n = 13) and HDUP (n = 14) groups were fed diets provided 14% (94.7 g MP/kg DM) and 24% (104.3 g MP/kg DM) MP in excess of these requirements respectively, which this increment was coming from DUP (DUP/MP ratio 43.8; 51.0% and 57.6% respectively). All diets were isoenergetic (12 MJ ME/kg DM). All ewes received the same lactation diet after lambing. Ewes in HDUP tend to produce more colostrums (p < 0.1) and had higher protein, fat, and solids non-fat content (p < 0.05) in colostrums during the first 24 h after lambing. MDUP group had higher colostrum yield compared to CDUP (p < 0.1). The changes in body weight and body condition score of ewes were similar for all diets but placenta weight was higher in MDUP group (p < 0.05) than for HDUP and CDUP ewes. Lamb body weight at weaning was higher for males compared to females (p < 0.05), but was not different between treatments. HDUP ewes had higher blood glucose concentration in the pre-lambing period than other treatments (p < 0.05). In this period, increasing the level of DUP in diet increased the content of blood urea nitrogen (p < 0.05). It was concluded that increasing the DUP content of diet for 3 weeks prior to lambing above the standard requirements resulted in an increase in colostrums production but had no effect on lamb outcome to weaning.

The effects of levels of concentrate offered and inclusion of maize gluten or fish meal in the concentrate on reproductive performance and blood parameters of dairy cows

Five randomized-block experiments were carried out over 2 years using British Friesian cows managed as three separate herds. The effects of offering cows different levels of concentrates, ranging from 0·8 to 7·2 kg/day, in addition to grass silagead libitumduring the winter period on reproductive performance was investigated. The effects of substituting 4 kg/day maize gluten, or 0·8 kg/day fish meal, for part or all of the standard concentrate were also examined.

Neither level of concentrates nor the inclusion of maize-gluten meal significantly affected reproductive performance even where milk production and quality was considerably influenced. The inclusion of fish meal improved conception rates to all services (0·64v.0·44;P< 0·05) and reduced the number of services required per conception (1·62v.2·31;P< 0·01).

Plasma urea levels were raised consistently by the feeding of fish meal and, with the exception of weeks 2 and 6 of lactation, by the feeding of higher levels of concentrates. From the 6th week of lactation levels of beta-hydroxybutyrate (BHB) in the blood were significantly higher in the group of cows receiving the highest level of concentrates. The BHB level at week 6 was correlated with the number of services required per conception.

A number of relationships between production factors and fertility are also presented.

Increasing prepartum dietary crude protein using poultry by-product meal dose not influence performance of multiparous Holstein dairy cows

The aim of this study was to compare the effects of two levels of Crude Protein (CP) using Poultry by-Product Meal (PBPM) fed during late gestation on the performance, blood metabolites and colostrum composition of Holstein cows. Twenty multiparous cows 26 +/- 6 days before expected calving were assigned randomly to two treatments containing 1) 140 g kg(-1) DM CP (34 g kg(-1) DM PBPM) 2) 160 g kg(-1) DM CP (75 g kg(-1) DM PBPM). The cow's BCS was 3.56 +/- 0.5 on average, at the beginning of the trial. Yields of milk, protein, lactose and fat were not affected by prepartum dietary CP level. Colostrum composition (fat, CP and total solids percents), blood metabolites (Ca, glucose, total protein, albumin, globulin, urea N and cholesterol) and metabolic diseases incidence were not influenced by prepartum dietary CP level. There was no significant difference between treatments in body weight and BCS changes. As expected, blood urea N before calving was higher in the cows fed 160 g kg(-1) DM CP diets (p < 0.002). Serum cholesterol during prepartum (p < 0.03) and postpartum (p < 0.01) periods was significantly lower in 160 g kg(-1) DM CP treatment. In general, although postpartum glucose level increased in cows which received 160 g kg(-1) DM CP in the diet, it seems that there is no other obvious advantages over feeding the 140 g kg(-1) DM CP diet. So feeding this level of CP diet to close up cows is recommended.

Effects of plasma urea nitrogen levels on the bovine oocyte ability to develop after in vitro fertilization

The overall aim of the present study was to evaluate in vitro development ability of oocytes recovered from 56 Holstein Frisian heifers with low [group 1 (G1): <13 mg /dl], moderate [group 2 (G2): 13-16 mg /dl] and high [group 3 (G3): >16 mg /dl] plasma urea nitrogen (PUN) concentrations, to determine whether PUN concentrations affect the competence of oocytes to progress to blastocysts after in vitro fertilization. In vitro oocyte and embryo development was assessed by blastocyst rates, embryo total cell numbers and apoptosis. Blood samples for the determination of PUN were collected 24 h prior to collection of the ovaries at the slaughter. A total of 112 ovaries were collected at a local abattoir and oocytes (n = 697) were aspirated, in vitro matured and fertilized. On day 8, blastocysts were assigned to the terminal dUTP nick end labelling assay. Cleavage rates were significantly higher (p < 0.001) for groups 1 and 2 than for group 3 (i.e. 72.5% and 72.2% vs 61.7%, respectively). The proportion of fertilized oocytes that developed into blastocysts was higher (p < 0.05) for group 1 than for group 3 (34.0% vs 23.0%, respectively). Day 8 blastocysts showed higher total cell counts (p < 0.05) for group 1 than for group 3 (123.7 vs 76.3), and a higher (p < 0.05) total apoptotic cell rate was found in group 3 (25.9 and 19.0 vs 43.2 for G1, G2 and G3, respectively). In conclusion, the ability of oocytes from heifers with increased levels of PUN to develop to the blastocyst stage was significantly reduced when standard routines for in vitro maturation, fertilization and culture were followed. These detrimental effects can be mediated in part through direct effect of urea and/or by the metabolic products on the process of follicle-enclosed oocyte nuclear and cytoplasmic development.

Efeito do nível de uréia na dieta sobre o desempenho, a qualidade e o estádio de desenvolvimento embrionário em cabras Alpinas

Utilizaram-se 22 cabras da raça Alpina, distribuídas aleatoriamente em quatro tratamentos (T): as cabras do T1 (n=5) formaram o grupo-controle; as do T2 (n=7) receberam 0,73% de uréia na matéria seca da dieta; as do T3 (n=4) receberam 1,46% de uréia; e as do T4 (n=6), 2,24% de uréia. As cabras foram superovuladas e os embriões, coletados entre sete e oito dias após a primeira monta, foram avaliados quanto à qualidade e ao estádio de desenvolvimento. Amostras de sangue para dosagem dos teores de uréia e glicose foram coletadas nos dias do estro e da coleta de embriões. Houve efeito linear crescente do nível de uréia nas dietas sobre o consumo de MS (kg/dia) e de proteína bruta (kg/dia). O peso das cabras não diferiu (P>0,05) entre os tratamentos nem entre as semanas experimentais. Dezoito cabras (81,8%) manifestaram estro após a sincronização. A duração do estro e o intervalo da remoção da esponja ao início do estro não foram influenciados (P>0,05) pelos tratamentos. Quatorze cabras (77,8%) responderam à superovulação. O número de estruturas e de embriões coletados não diferiu (P>0,05) entre os tratamentos. O número (Y= 10,90 - 11,64NS U + 4,93<FONT FACE=Symbol>§</FONT>U²; R² = 0,67; P<0,10) e a percentagem (Y= 94,08 - 39,59NS U + 18,16<FONT FACE=Symbol>ª</FONT>U²; R² = 0,94; P<0,07) de embriões viáveis, e o número (Y= 10,83- 12,18NS U + 5,02mU²; R² = 0,78; P<0,08) e a percentagem (Y= 94,83- 52,31NS U + 21,56*U²; R² = 0,90; P<0,05) de embriões excelentes e bons apresentaram comportamento quadrático em função do nível de uréia nas dietas. Os teores de uréia e glicose no plasma não foram influenciados (P>0,05) pelos tratamentos. A uréia pode ser fornecida no nível de 2,24% na MS da dieta de cabras não lactantes.

Ion concentrations in oviduct and uterine fluid and blood serum during the estrous cycle in the bovine

In the bovine up to 40% of embryos die before implantation but despite the importance of ions in oviduct and uterine fluid formation and in gamete, zygote and early embryo development there is very little published information on the ion concentrations of oviduct or uterine fluid. The free anions chloride, phosphate and sulphate and the free cations sodium, calcium, magnesium and potassium were measured in oviduct fluid on days 0, 2, 4 and 6 and in uterine fluid on days 6, 8 and 14 and in corresponding blood samples. Oviduct and uterine fluids were collected in situ. Sodium was 25-fold higher than potassium and 80-fold higher than the other ions and chloride was 10-fold higher than potassium and 40-fold higher than the other ions in oviduct and uterine fluid. Phosphate, sulphate, magnesium, potassium and calcium were at lower concentrations in all fluids. Oviduct calcium and sodium were higher on day 0 than other days. The most striking uterine differences were the higher potassium and lower chloride, sodium and magnesium on day 14 than other days. There were significant positive associations between oviduct and blood chloride, sulphate, magnesium and calcium while only uterine sulphate was positively related to its blood concentration. There was no relationship between fluid secretion rate and no association between the concentrations of systemic progesterone or oestradiol and any ion in oviduct or uterine fluid. The different concentrations and associations between ions in the oviduct, uterus and blood suggest a differential regulation of ion secretion by the oviduct and uterine epithelia.

Effects of application in spring of urea fertiliser on aspects of reproductive performance of pasture-fed dairy cows

AIMS

To assess if raising concentrations of crude protein (CP) in pasture in spring by the frequent application of urea fertiliser would affect ovarian follicular dynamics, luteal function, onset of oestrus and reproductive performance of dairy cows under farming conditions in New Zealand.

METHODS

Spring-calved dairy cows were grazed for 101 days in paddocks that were either not fertilised (Control; n=20) during the course of the study, or were fertilised with 40-50 kg nitrogen (N)/ha every 4-6 weeks (High-N; n=20). Similar generous pasture allowances were offered to both groups. Concentrations of CP in pasture, urea in serum and progesterone in milk were measured. Ovarian follicular and luteal dynamics were determined using ultrasonography. Oestrous behaviour and the number, time and outcome of inseminations were also recorded.

RESULTS

Mean concentrations of CP in pasture and urea in serum was higher in the High-N than the Control group (25.2 vs 21.6 and 8.3 vs 5.4 mmol/L for CP and urea, respectively; p<0.001). Intervals between calving and first oestrus, first insemination and conception, the time of first emergence of a dominant follicle, milk progesterone concentration, and the diameter of the corpus luteum (CL) in the first luteal phase did not differ significantly between groups. The interval from calving to first ovulation tended (p=0.10) to be lower and the diameter of the dominant follicle of the oestrous cycle at which cows conceived was greater (p=0.02) in Control than High-N cows.

CONCLUSIONS

The use of large amounts of urea fertiliser during spring and the consequent increases in concentrations of CP in pasture and urea in serum did not negatively affect any of the parameters of reproductive performance of pasture-fed dairy cows that were assessed in this study.

Interactions between metabolic status, pre-breeding protein supplementation, uterine pH, and embrionic mortality in ewes: preliminary observations

The effect of prebreeding short-term protein supplementation level (PL) and body condition (BC) on fertility rate (FERT,%), uterine pH and embryonic mortality (EMORT,%) in sheep, was evaluated. Multiparous Rambouillet ewes at low BC (LC; n = 6, 62.7+/-1.7 kg) or high BC (HC; n = 6, 71.9 +/-1.7 kg), received, within BC, one of two levels of ruminally undegradable protein: low (LP, 14 g/ewe per day) and high (HP, 30 g/ewe per day). Once the animals were euthanized, corpus luteum number (CLN), as an indicator of ovulation rate, was registered and uterine horns were irrigated to recover embryonic tissue plus associated membranes as well as to measure uterine pH (UpH). While EMORT- 1 considered a nonadjusted relationship between the number of embryos and CLN, EMORT-2 considered an analysis of covariance using CLN as the covariate. The HP-supplemented ewes had the lowest FERT (p = 0.06; 100% vs 50%) and the highest EMORT (EMORT-1, 16.6% vs 53.8%, p = 0.08; EMORT-2, 52.0% vs 14.5%, p = 0.07) when compared to the LP-supplemented ewes. Neither BC nor PL affected CLN, CL weight or P4 release (p > 0.10). While the lowest UpH (p = 0.04) was observed in the HP-supplemented ewes, this group also showed the lowest fertility and the highest embryonic mortality.

Detrimental effects of high plasma urea nitrogen levels on viability of embryos from lactating dairy cows

High plasma urea nitrogen (PUN) concentrations are associated with decreased fertility in lactating dairy cows. Our objective was to evaluate the quality of embryos flushed from superovulated lactating cows having moderate or high PUN concentrations. Subsequent embryo survival was determined after transfer to recipient heifers with either low or high PUN. Lactating Holstein dairy cows (n = 23; 50-120 days in milk) were randomly assigned to one of two diets designed to result in moderate or high PUN concentrations (15.5 +/- 0.7 and 24.4 +/- 1.0 mg/dl, respectively; P < 0.001) and were fed for 30 days before embryo flushing and recovery. Embryos (n = 94) were evaluated morphologically, frozen and subsequently transferred into synchronized virgin heifers that were fed one of two diets designed to result in either low or high PUN concentrations (7.7 +/- 0.9 and 25.2 +/- 1.5 mg/dl, respectively; P < 0.001; 2 x 2 factorial design). The number, quality and stage of development of recovered embryos were similar for cows with moderate or high PUN. Transfer of embryos from moderate PUN donor cows resulted in a higher pregnancy rate (35%; P < 0.02) than the transfer of embryos from high PUN donor cows (11%). Pregnancy rate was not affected by either recipient diet or the interaction of donor and recipient diets (P > 0.05). These results indicate that high PUN concentrations in lactating dairy cows decrease embryo viability through effects exerted on the oocyte or embryo before recovery from the uterus 7 days after insemination.

Effect of dietary protein on embryo recovery rate and quality in superovulated heifers

For almost 3 decades, superovulation and embryo transfer have been used in cattle breeding to increase the number of offspring from genetically superior female animals. Several factors including nutrition affect the number of transferable embryos recovered. We compared the effects of two different dietary protein levels easily achieved in practical conditions on embryo number and quality in superovulated heifers. Finnish Ayrshire heifers (n = 37) were allocated to isoenergic diets containing either 14% (D14) or 18% (D18) crude protein (CP). Estruses were synchronized, and the heifers were subsequently superovulated and inseminated using a standard FSH-protocol. Embryos were collected 7 days after inseminations (71-72 days after the beginning of the treatment period) by uterine flushing. The number of corpora lutea, and the number and quality of embryos were determined. Protein feeding did not affect superovulatory response, the number of embryos or the number of transferable embryos recovered. Proportionally more poor-quality embryos were found in group D14 than in group D18 (20.2% versus 13.2%, respectively, P = 0.053). It is concluded that a long-term moderate increase in the content of crude protein fed to energy-adequate heifers does not seem to affect superovulatory response and the number of embryos recovered, but it may be advantageous to the quality of embryos.

Association between blood plasma urea nitrogen levels and reproductive fluid urea nitrogen and ammonia concentrations in early lactation dairy cows

Two experiments were conducted to study the relationship of blood plasma urea nitrogen (PUN) concentrations with NH3, urea nitrogen, K, Mg, P, Ca, and Na concentrations in fluid of preovulatory follicles (experiment 1) and the relationships of PUN concentration and stage of estrus cycle with ammonia and urea nitrogen concentrations in uterine fluids (experiment 2) in early lactation dairy cows. Mean PUN levels were used to distribute cows into two groups: cows with PUN>or=20 mg/dl (HPUN), and cows with PUN<20 mg/dl (LPUN). In experiment 1, blood and follicular fluids from preovulatory follicles of 38 early lactation dairy cows were collected on the day of estrus (day 0) 4h after feed was offered. Follicular fluid NH3 was higher (P<0.01) in HPUN cows (339.0 micromol/L+/-72.2) compared to LPUN cows (93.9 micromol/L+/-13.1). Follicular fluid urea N was higher (P<0.001) in HPUN cows (22.4 mg/dl+/-0.4) compared to LPUN cows (17.0 mg/dl+/-0.3). PUN and follicular fluid urea N were correlated (r2=0.86) within cows. In experiment 2, blood and uterine fluids were collected from 30 cows on day 0 and on day 7. Uterine fluid NH3 was higher (P=0.05) in HPUN cows (1562 micromol/L+/-202) than in LPUN cows (1082 micromol/L+/-202) on day 7, but not on day 0. Uterine fluid urea N was higher (P<0.001) in HPUN cows than in LPUN cows on day 0 (26.9 mg/dl+/-1.3 and 20.4 mg/dl+/-0.7) and day 7 (26.5 mg/dl+/-1.1 and 21.4 mg/dl+/-1.1). There was a correlation (r2=0.17) between PUN and uterine fluid urea N within cows. The results of this study indicate that high PUN concentrations were associated with elevated NH3 and urea N concentrations in the preovulatory follicular fluids on the day of estrus and in the uterine fluid during the luteal phase of the estrous cycle in early lactation dairy cows. Elevated NH3 or urea N concentrations in the reproductive fluids may contribute to reproductive inefficiency in dairy cows with elevated plasma urea nitrogen due to embryo toxicity.

Effects of Urea Infusion on the Uterine Luminal Environment of Dairy Cows

Previous research indicates that high plasma urea nitrogen (PUN) concentrations are associated with decreased fertility in lactating dairy cows. The objective of this study was to monitor changes in the uterine environment during acute elevation of PUN. Lactating dairy cows (n = 8) were infused with saline or urea (0.01 g of urea/h per kg of body weight) through jugular vein catheters on d 7 after estrus. After 24 h, cows were switched to the opposite treatment for a second 24-h infusion period. Blood samples were collected every 2 h, and the pH within the lumen of the uterine horn ipsilateral to the corpus luteum was recorded every 6 h. At the end of each 24-h infusion period, 30 mL of sterile saline was flushed into the uterine lumen and immediately retrieved. Mean PUN concentration increased from 16.6 +/- 1.3 mg/dL during saline infusion to 22.6 +/- 1.3 mg/dL during urea infusion. Uterine pH decreased during urea infusion from 7.08 +/- 0.07 at 6 h to 6.88 +/- 0.08 at 18 h, but was unchanged during saline infusion (7.01 +/- 0.08 at 6 h to 7.06 +/- 0.07 at 18 h). Protein concentration, PGF(2alpha), and prostaglandin E(2) concentrations in uterine lavage samples were not different between treatments. The results of this study indicate that a short-term increase in PUN can exert direct effects on the uterine environment by decreasing uterine pH.

Effect of ammonium chloride on the growth and metabolism of bovine ovarian granulosa cells and the development of ovine oocytes matured in the presence of bovine granulosa cells previously exposed to ammonium chloride

Three experiments determined first, the effect of increasing ammonium chloride (NH(4)Cl) concentrations on the growth and metabolism of bovine granulosa cells isolated from small and medium-sized bovine ovarian follicles; secondly, whether the changes in granulosa cell growth and metabolism induced by NH(4)Cl were reversible; and thirdly, whether granulosa cells, previously conditioned with NH(4)Cl, were able to support maturation of oocytes in vitro. In Experiment 1, using a 2 (follicle size class) x 5 (NH(4)Cl concentration) factorial design, granulosa cells from small or medium-sized ovarian follicles were incubated for 96 h with 0, 0.2, 0.4, 0.8 or 1.6 micromol NH(4)Cl/ml. Experiment 2 used a split plot factorial design where granulosa cells were incubated for 96 h in the presence or absence of 1 micromol/ml NH(4)Cl and then incubated in the absence or presence of 1 micromol/ml NH(4)Cl for a further 48 h. Finally in Experiment 3, ovine oocytes were matured on layers of bovine granulosa cells which had not been conditioned with NH(4)Cl or conditioned with 0.5 or 1.0 micromol/ml NH(4)Cl and development of embryos to the blastocyst stage followed and blastocyst quality assessed. In Experiment 1, incubation of granulosa cells in increasing concentrations of NH(4)Cl reduced cell growth, increased cell protein concentrations and increased the amounts of MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) oxidised and oestradiol and progesterone produced per 10(5) cells. Cells from medium-sized follicles were more sensitive to NH(4)Cl concentration and oxidised more MTT and produced less progesterone at high NH(4)Cl concentrations than cells from small-sized follicles. When, in Experiment 2, NH(4)Cl was removed from cell culture after 96 h incubation, cells previously exposed to NH(4)Cl grew at a slower rate during the subsequent 48 h, contained more cellular protein, oxidised more MTT and produced more oestradiol and progesterone than cells not previously exposed to NH(4)Cl. Maturation of ovine oocytes in coculture with bovine granulosa cells not exposed to NH(4)Cl (Experiment 3) increased egg cleavage rate and the proportion of cleaved eggs which developed to the blastocyst stage. Conditioning of granulosa cells with NH(4)Cl supported egg cleavage and development to the blastocyst stage at rates similar to those observed in the absence of granulosa cells. In conclusion, these experiments showed that the in vitro growth and metabolism of granulosa cells were altered by concentrations of NH(4)Cl similar to ammonium ion concentrations measured in follicular fluid and that these effects were not immediately reversible. Furthermore, the ability of granulosa cells conditioned with NH(4)Cl to support in vitro maturation of oocytes was impaired.

Relationships of metabolic profiles to milk production and feeding in dairy cows

The aim of this study was to assess the practicality of the metabolic profile test (MPT) for feeding evaluation in dairy cattle. Stepwise regression analysis was used to evaluate the relationships of MPT to feeding and milk production of 4,679 cows in 343 commercial dairy herds. Significant explanatory variables were determined by forward set-up selection, among the deviated values from the reference values of 10 blood metabolites and body condition score, to predict dependent variables, i.e., milk production and the rate of feeding to nutrient requirements, in each or all lactation stages and the dry period. The milk production model of the all-lactation stage showed the greatest goodness-of-fit (adjusted R(2)=0.214, p<0.0001) with high positive regression coefficients for serum cholesterol, magnesium, urea nitrogen and albumin, and negative for glucose and calcium. In the feeding models, goodness-of-fit of crude protein was relatively high (R(2)=0.072, p<0.0001) with a positive relationship to blood urea nitrogen. Although the other feeding models were low in goodness-of-fit, several significant explanatory variables to feeding were found. All feeding models in the late lactation stage and the dry period, in which the feeding was stable, had greater goodness-of-fit than those in the early lactation stage in which milk production varied. It was concluded that the values which deviated from the reference values for the MPT components could assess milk production and feeding, and the MPT is a practical tool for auxiliary feeding evaluation.

Disruption of bovine oocytes and preimplantation embryos by urea and acidic pH

Feeding cattle diets high in degradable crude protein (CP) or in excess of requirements can reduce fertility and lower uterine pH. Objectives were to determine direct effects of urea and acidic pH during oocyte maturation and embryonic development. For experiment 1, oocytes were matured in medium containing 0, 5, 7.5, or 10 mM urea (0, 14, 21, or 28 mg/dl urea nitrogen, respectively). Cleavage rate was not reduced by any concentration of urea. However, the proportion of oocytes developing to the blastocyst stage at d 8 after insemination was reduced by 7.5 mM urea. In addition, the proportion of cleaved oocytes becoming blastocysts was decreased by 5 and 7.5 mM urea. For experiment 2, putative zygotes were collected -9 h after insemination and cultured in modified Potassium Simplex Optimized Medium (KSOM). Urea did not reduce the proportion of oocytes developing to the blastocyst stage, although 10 mM urea reduced cleavage rate slightly. For experiment 3, dimethadione (DMD), a weak nonmetabolizable acid, was used to decrease culture medium pH. Putative zygotes were cultured in modified KSOM containing 0, 10, 15, or 20 mM DMD for 8 d. DMD reduced cleavage rate at 15 and 20 mM and development to the blastocyst stage at all concentrations. Results support the idea that feeding diets rich in highly degradable CP compromises fertility through direct actions of urea on the oocyte and through diet-induced alterations in uterine pH.

Effect of timing of urea feeding on the yield and quality of embryos in lactating dairy cows

High protein diets, which lead to excess production of nonprotein nitrogen such as ammonia and urea, have been associated with reduced fertility in dairy cows. In this study we test the hypothesis that diets containing high levels of quickly degradable urea nitrogen (QDN) compromise embryo development. Lactating dairy cows were fed mixed silage and concentrates twice daily. At 60 days postpartum, a synchronized estrus was induced and the cows were subsequently superovulated and inseminated using a standard protocol. On Day 7 after insemination, the uteri were flushed and embryos retrieved. At the start of treatment, cows were randomly allocated into three nutritional groups: control (CONT, n = 8), long (L-) QDN (n = 8) and short (S-) QDN (n = 9). The L-QDN cows were fed a supplement of urea from 10 days before insemination, and the S-QDN cows were fed the supplement from insemination until embryo collection. Both L- and S-QDN diets produced significant increases in plasma ammonia and urea 3 h post-feeding. The S-QDN but not the L-QDN diet was associated with a significant reduction in embryo yield. Embryo quality was also significantly reduced in the S-QDN cows. This study indicates that there is no deleterious effect on the yield and quality of embryos recovered 7 days after breeding when QDN feeding is initiated during the previous midluteal phase. However, introduction of a similar diet 10 days later, at the time of insemination, was deleterious. We suggest that QDN is toxic to embryos but cows can adjust within 10 days.

Effect of elevated systemic concentrations of ammonia and urea on the metabolite and ionic composition of oviductal fluid in cattle

High dietary protein leads to elevated systemic concentrations of ammonia and urea, and these, in turn, have been associated with reduced fertility in cattle. The effect of elevating systemic concentrations of ammonia and urea on the concentrations of electrolytes and nonelectrolytes in bovine oviductal fluid were studied using estrus-synchronized, nulliparous heifers (n = 25). Heifers were randomly assigned to 1 of 3 treatments consisting of jugular vein infusion with either ammonium chloride (n = 8), urea (n = 8), or saline (n = 9). Oviducts were catheterized, and fluid was recovered over a 3-h period on either Day 2 or 8 of the estrous cycle. No difference (P > 0.05) was found in the concentrations of any electrolyte or nonelectrolyte between oviducts ipsi- or contralateral to the corpus luteum. Plasma and oviductal concentrations of urea were increased by infusion with urea (P < 0.001) and ammonium chloride (P < 0.05) but not by saline (P > 0.05). Plasma and oviductal concentrations of ammonia were elevated by infusion with ammonium chloride (P < 0.001) but not by infusion with urea or saline (P > 0.05). No effect (P > 0.05) of treatment was found on oviductal or plasma concentrations of glucose, lactate, magnesium, potassium, or sodium or on plasma concentrations of insulin or progesterone. The concentration of calcium in oviductal fluid was reduced by urea infusion and was negatively associated with systemic and oviductal concentrations of urea. Oviductal concentrations of sodium were higher on Day 8 than on Day 2 (P < 0.05). No effect of sample day was found on any of the other electrolytes or nonelectrolytes measured (P > 0.05). Elevated systemic concentrations of ammonia and urea are unlikely to reduce embryo survival through disruptions in the oviductal environment.