Disappearance of infused phytate from the large intestine of dairy heifers.

The objective of this study was to investigate the disappearance of phytate from the large intestine of dairy heifers. Uncertainty about the availability of phosphorus (P) in different feeds may limit implementation of dietary strategies to reduce fecal P excretion by dairy cows. Increased understanding of the dynamics of phytate degradation and disappearance of P in the large intestine may improve prediction of intestinal P digestion and absorption. Eight ruminally- and ileally-cannulated crossbred dairy heifers were used in two 4×4 Latin square designs with 9-d periods, including 3d of washout. All heifers were fed a high-forage diet containing 0.14% P throughout the study. Ytterbium-labeled corn silage and Co-EDTA were dosed to the rumen 4 times daily as particulate and liquid phase markers, respectively, to measure ileal digesta flow. Ond 4 to 7 of each period, each heifer was infused ileally with 0, 5, 15, or 25 g/d of phytate (phytic acid) in solution and total fecal collection was conducted. When infusion ceased (d 8 and 9) ileal digesta was sampled to measure P flow to the ileum from the basal diet. Feed, digesta, and feces were dried, ground, and analyzed for phytate P, inorganic P, and total P using high performance ion chromatography, inductively coupled plasma atomic emission spectroscopy, and the molybdovanadate yellow method, respectively. Phytate degradation in the large intestine was observed but was not complete, and the amount of infused phytate did not influence the degradability of phytate. Fecal excretion of total P increased with increasing total P infused. The slope coefficient for ileal P flow (dietary only) to feces was 0.56 ± 0.26 (mean ± SE), whereas the slope coefficient for infused P was 0.75 ± 0.13. These indicate net absorption of P from the large intestine and greater disappearance of P from dietary P flowing to the ileum than from the infused pure phytate (44 vs. 25%). This data will support mechanistic modeling efforts to improve prediction of P digestion, allowing more accurate estimation of P bioavailability in feeds.

Effect of exogenous somatotropin in Holstein calves on mammary gland composition and proliferation.

Pubertal mammary gland growth and development are hormonally regulated, but the details are poorly understood in calves. Our purpose was to evaluate the effects of exogenous growth hormone (GH) on the biochemical composition of the prepubertal mammary gland, mRNA expression of selected genes, and histological characteristics of the developing parenchyma (PAR). In this experiment, 19 calves (7 ± 4 d of age) were randomly assigned to 1 of 2 treatments: bovine somatotropin (bST, 500 mg; n = 10) or placebo (Sal; 0.9% saline; n = 9). Animals were treated every 3 wk beginning on d 23. Calves were assigned to an early (65 d; tissue harvested after 2 treatment injections) or late collection time (107 d; tissue harvested after 4 treatment injections). Calves were fed milk replacer and calf starter for 8 wk and starter and hay thereafter. Parenchyma and mammary fat pad (MFP) from one udder half were harvested for analysis of protein, lipid, and DNA. Additional tissues were preserved for histological analysis or snap-frozen for quantitative real-time PCR. Somatotropin treatment did not significantly alter the mass of PAR or MFP or the general pattern of development of epithelial structures. Significant increases were observed in protein/100 kg of body weight (BW), total protein, DNA concentration, DNA/100 kg of BW, and total DNA in 107-d calves, and a significant treatment by day interaction was observed for DNA and lipid concentrations in PAR. In MFP, a significant decrease was observed in protein/100 kg of BW in bST-treated calves and in total MFP protein in 65-d calves. A treatment by day interaction was found for total protein, DNA, and protein/100 kg of BW. In PAR, relative expression of ATPase-binding cassette 3 and growth hormone receptor were reduced by bST and both were lower in 107-d-harvest calves. Epithelial cell retention of bromodeoxyuridine (BrdU; possible indicator of stem-like cells) was greatest in 65-d bST-treated calves, and a significant time of sampling response and treatment × time interaction were observed. Expression of the proliferation marker protein Ki67 was numerically higher in bST-treated calves but the difference was nonsignificant. Retention of the BrdU label was reduced in 107-d calves. Exogenous growth hormone given to calves may affect mammary tissue composition and epithelial cell gene expression in subtle ways but exogenous supplementation with bST alone is not likely to alter overall development patterns or affect the mass of mammary parenchymal tissue. Whether such subtle changes have an effect on subsequent development or function is unknown.

Interaction of energy balance, feed efficiency, early lactation health events, and fertility in first-lactation Holstein, Jersey, and reciprocal F1 crossbred cows.

First-lactation Holstein (HH), Jersey (JJ), and crossbred cows (HJ and JH, with sire breed listed first, followed by dam breed) were observed for cumulative energy intake (CEI15) and energy used for milk production (CEL15) at wk 15 of lactation in addition to recordings of health problems and pregnancy. Cumulative energy balance (CEB15) was calculated from CEI15 and estimates of expenditures at wk 15 of lactation. Feed efficiency (FE15) was calculated by dividing CEL15 by CEI15. Data included 140 cows with 43, 34, 41, and 22 in the HH, HJ, JH, and JJ groups, respectively. The first incidence of displaced abomasum (DA), ketosis (KET), mastitis (MAST), and metritis (MET) was recorded in the first 100 d of lactation with an incidence of the disease coded as 1 and no incidence coded as 0. Pregnancy (PREG) at d 150 was recorded as 1 if a cow had conceived by d 150 and 0 if she had not. Logistic regression was used to analyze health and fertility with fixed effects in the model including genetic group, linear and quadratic effects for age at calving, and year-season of freshening group. Pregnancy was analyzed with the same variables and the addition of CEB15. In other analyses, CEB15, CEI15, CEL15, and FE15 were response variables with the same explanatory variables plus health events (MAST, DA, MET, and KET), where each health event was a separate analysis. Genetic group effects were significant in the occurrence of MAST and a trend for MET, but were not significant for PREG, DA, and KET. Significant odds ratio for MAST was 19.6 for HJ cows when compared with that for HH cows. Thus, HJ cows were 19.6 times more likely than HH cows to have an incidence of MAST. The trend was for HJ and JH to have a lower odds ratio of MET than that of HH. No other genetic group effects were significant in any of the disease and PREG models. The linear and quadratic terms for age at calving were not significant. An occurrence of MAST decreased FE15 by 5.2±2.2%. Mastitis also decreased CEI15 and CEL15, but the compensatory reductions left the CEB15 unaffected. An occurrence of a DA decreased CEI15 and an incidence of KET decreased CEB15.

Expression pattern of apoptotic genes in vitrified-thawed bovine oocytes.

This study describes a method for quantification of transcripts from low numbers of bovine oocytes using real time RT-PCR. The objective was to evaluate the expression pattern of apoptotic genes (Fas, FasL, Bax and Bcl-2) in vitrified-thawed oocytes. Oocytes were evaluated at germinal vesicle stage; at 15 h of maturation; after vitrification and warming at 15 h of maturation and at 9 h of additional maturation. All transcripts showed an increase in at least 1.2-fold change post-vitrification warming, but the levels tended to decrease at 9 h of maturation post-vitrification warming. Transcript abundance for Fas mRNA was 1.4-fold for oocytes after vitrification and warming. The level of Fas mRNA upon maturation was 0.8-fold. The increase in the abundance of FasL mRNA was 2.1, while it was 0.5-fold relative to control. Vitrification resulted in 1.5-fold change in Bax mRNA expression in oocytes. After 9 h of maturation post-vitrification warming, the level for Bax mRNA was 0.6-fold. The mRNA for Bcl-2 was nearly the same after vitrification and warming. The abundance of mRNA for Bcl-2 was 1.2-fold in vitrified oocytes and fell (p = 0.05) to 0.5 at 9 h of maturation post-vitrification and warming. The up-regulation of apoptotic genes in vitrified oocytes may be an early indicator of reduced developmental competence following vitrification. Yet, results from terminal deoxynucleotidyl transferase dUTP nick end labelling and caspase assays did not support the evidence of apoptosis in embryos derived from large numbers of vitrified oocytes.

In vitro development of bovine embryos cultured with stem cell factor or insulin-like growth factor-I following IVF with semen of two bulls having different field fertility.

The usefulness of IVF as a potential tool to evaluate the field fertility of bulls is equivocal and growth factor addition to culture media research is needed to delineate components needed for providing defined environments for embryos. The overall aim was to evaluate the in vitro development of embryos derived using a serum supplemented and serum-free production systems and semen from two bulls of different field fertility. The study was conducted to determine the combinatorial effect of stem cell factor (SCF) and/or insulin-like growth factor-I (IGF-I) in culture on subsequent embryo development in cattle. Oocytes were aspirated separately from >or=3 to <3mm follicles to test different follicle size populations and were matured in TCM-199 supplemented with LH, FSH, estradiol and BSA (Fraction V). Matured oocytes were fertilized in BSA supplemented synthetic oviductal fluid (SOF)-IVF medium. Presumptive zygotes were cultured for 8d (in humidified 5% CO(2) at 38.5 degrees C) in BSA supplemented SOF-in vitro culture (IVC) medium. SOF-IVC medium was supplemented with fetal bovine serum (4%), IGF-I (100ng/mL), SCF (50ng/mL) or IGF-I (100ng/mL)+SCF (50ng/mL). The development competence of embryos did not differ between the bulls and among the culture environments. Nevertheless, there was an effect of follicle size on cleavage rate (P<0.05) and a greater cleavage rate resulted from oocytes aspirated from >or=3mm follicles (71.0+/-1.5%) compared to those collected from <3mm follicles (64.8+/-1.6%). The overall cleavage rate (%); blastocyst formation (%); and expanded/hatched blastocyst formation (%) were 68.2+/-1.5 and 67.7+/-1.7; 29.4+/-1.4 and 28.6+/-1.5; and 18.6+/-1.2 and 18.5+/-1.1, respectively, for the bull of above and below average field fertility. The results indicate that follicle size for oocyte aspiration is effective for determining IVC success and that IVF may not discriminate among bulls of different field fertility.

Effect of droplet vitrification on development competence, actin cytoskeletal integrity and gene expression in in vitro cultured mouse embryos.

The effect of modified droplet vitrification was assessed on cellular actin filament organization, apoptosis related gene expression and development competence in mouse embryos cultured in vitro. Mouse zygotes, 2-cell embryos and morulae were vitrified in ethylene glycol (VS-1) and ethylene glycol plus DMSO (VS-2) and thawed by directly placing the vitrified drop into 0.3M sucrose solution at 37 degrees C. High recovery (93-99%) of morphologically normal embryos was evident following vitrification and thawing. No detectable actin filament disruption was observed in the embryos at any development stage following vitrification and thawing and/or in vitro culture. The expression pattern of Bax, Bcl2 and p53 genes was altered (P<0.05) in vitrified zygotes and 2-cell embryos, but not in morulae. Although a large proportion of the vitrified zygotes (59.5+/-4.4% in VS-1 and 57.9+/-4.5% in VS-2; mean+/-S.E.M.) and 2-cell embryos (63.1+/-4.4% in VS-1 and 59.2+/-4.3% in VS-2) developed into blastocysts, development of control embryos (70.2+/-5.0% of zygotes and 75.5+/-4.4% of 2-cell embryos) into blastocysts was higher (P<0.05). In contrast, development of the control and vitrified morulae into blastocysts (more than 85%) was similar. We concluded that the modified droplet vitrification procedure supported better survival of morula stage compared to zygotes and 2-cell mouse embryos.

Lactation performance of mid-lactation dairy cows fed ruminally degradable protein at concentrations lower than national research council recommendations.

The aim of this study was to test whether feeding of diets containing lower proportions of ruminally degradable protein (RDP) but with a constant proportion of ruminally undegradable protein (RUP) alters feed intake, milk production and yield, and the apparent efficiency of N utilization by mid-lactation dairy cows. During the covariate period (d 1 to 28), 40 mid-lactation cows (36 Holstein and 4 Jersey x Holstein cross-breds) were fed a common diet formulated to contain 11.3% of diet dry matter (DM) as RDP. During the treatment period (d 29 to 47), cows were randomly assigned to 1 of 4 diets formulated to contain 11.3, 10.1, 8.8, or 7.6% RDP, whereas ruminally undegradable protein remained constant at 7.1% of DM. All diets contained 47.5% forage and 52.5% concentrate on a DM basis. Dry matter intake was significantly reduced for the 7.6% RDP diet. The lowest RDP content was associated with a trend for reduced milk yield. Dietary RDP had no effect on body weight or milk fat, protein, and lactose contents. Milk protein yield was not affected by RDP level; however, milk fat yield decreased linearly as dietary RDP was reduced. Concentrations of plasma essential amino acids were unaffected, whereas milk urea-N concentrations decreased linearly as dietary RDP content was reduced. The apparent efficiency of N utilization for milk N production increased from 27.7% on the 11.3% RDP diet to 38.6% on the 7.6% RDP diet. The dietary RDP requirement of cows in this study was apparently met between 15.9 and 14.7% dietary crude protein. Milk production was not significantly affected by the 8.8% RDP (15.9% crude protein) diet even though the NRC (2001) model predicted that RDP supply was 87% of that required, suggesting the current NRC recommendations for RDP may be overestimated for mid-lactation dairy cows in this study.

Effects of milk replacer composition on growth, body composition, and nutrient excretion in preweaned Holstein heifers.

Twenty-four newborn Holstein heifer calves were fed 1 of 4 milk replacers (MR): control (20% CP, 21% fat; MR fed at 441 g/d); high protein/low fat (HPLF; 28% CP, 20% fat; MR fed at 951 g/d); high protein/high fat (HPHF; 27% CP, 28% fat; MR fed at 951 g/d); and HPHF MR fed at a higher rate (HPHF+; 27% CP, 28% fat; MR fed at 1,431 g/d). Dry calf starter (20% CP, 1.43% fat) composed of ground corn (44.4%), 48% CP soybean meal (44.4%), cottonseed hulls (11.2%), and molasses (1.0%) was offered free choice. Heifers were obtained from a commercial dairy, blocked by groups of 8 in the order acquired, and randomly assigned to treatments within group. Upon arrival at the research farm, heifers were fed the control for 2 feedings. Treatments were imposed when heifers were 4 +/- 1 d of age. Heifers were on study for 61 +/- 1 d. Body weight and body size measures were taken weekly. Four-day total collection of feed refusals, feces, and urine was initiated at 57 +/- 1 d of age. Heifers were slaughtered at the end of the collection period to evaluate body composition. Preplanned contrasts were used to compare control to all, HPLF to HPHF, and HPHF to HPHF+. Heifers fed the control diet consumed more starter than those fed other treatment diets, but their total dry matter intake and apparent dry matter digestibility were lowest. Fecal output was highest in heifers fed the control diet, whereas urine output and urine N excretion were lowest. Nitrogen intake and urine N excretion were greater for heifers fed HPHF+ compared with HPHF but were not affected by MR fat content (HPLF vs. HPHF). Retention (g/d) of N and P was greater in heifers fed all nutrient-dense diets compared with those fed the control diet, but was not improved by increasing fat in the milk replacer (HPLF vs. HPHF) or by increasing the amount fed. Addition of fat to the milk replacer (HPLF vs. HPHF) increased empty body weight fat content without improving average daily gain or frame measures. Increasing the volume fed (HPHF vs. HPHF+) increased growth rate and empty body weight, but HPHF+ heifers were neither taller nor longer and their carcasses contained more fat. Clear improvements in growth and nutrient retention were observed with more nutrient-dense diets, but most of the improvements were seen with the increased protein intake relative to the control MR; adding fat to the high protein MR did not further improve lean tissue gain.

Nitrogen and phosphorus retention and excretion in late-gestation dairy heifers.

The objectives of this study were to evaluate the effects of limit feeding diets containing concentrates or by-products in place of forages on manure and nutrient excretion in growing, gravid heifers. Eighteen Holstein heifers confirmed pregnant were grouped by due date and fed 1 of 3 diets (n = 6 per treatment) for the last 14 wk of pregnancy. Diets were high forage, fed ad libitum (HF); by-product based (BP), fed at the same rate as HF-fed heifers; or low forage (LF), fed at 86% of the HF diet. Diets were designed to supply equal quantities of P, N, and metabolizable energy. Total collection of feces and urine was conducted in wk 14, 10, 6, and 2 prepartum. The HF ration was 90.7% forage, 13.7% crude protein (CP), and contained orchardgrass hay, corn silage, corn grain, soybean meal 44%, and a vitamin-mineral premix. The BP diet was 46.2% forage and 14.0% CP, with 70% of the grain mix space replaced with soybean hulls and cottonseed hulls in a 1:1 ratio, with intake limited to 93% of the dry matter intake (DMI) of HF. The LF ration was 45.3% forage and 17.8% CP, with intake limited to 86% of the DMI of HF. The effect of diet was analyzed with repeated measures, using preplanned contrasts to compare HF with BP and LF with HF and BP. As designed, heifers fed HF and BP had greater DMI than the heifers limit-fed LF, and there was no effect of diet on average daily gain or BW. Intake and digestibility of N were lower, and fecal N excretion was higher, in heifers fed HF and BP than heifers fed LF. Mean feces excretion on both a wet and dry basis was greater for HF heifers compared with BP heifers and less for LF heifers than for HF and BP heifers. Despite differences in urinary output, diet had no effect on urea N excretion, but there was a trend for heifers fed HF and BP rations to excrete less urinary N compared with those fed LF. Compared with HF and BP heifers, LF heifers tended to have lower fecal P excretion and had higher urinary P excretion. Measured manure and urine excretion from heifers fed LF was greater than current American Society of Agricultural and Biological Engineers values, whereas heifers fed HF excreted less manure and urine than predicted. Heifers achieving similar rates of gain from diets differing in forage, grain, and by-product content excreted widely varying quantities of manure.

Gene expression and development of mouse zygotes following droplet vitrification.

The concept of ultra-rapid vitrification has emerged in recent years; the accelerated cooling rate reduced injury attributed to cryopreservation and improved post-freezing developmental competence of vitrified oocytes and embryos. The objectives of the present study were to develop a simple and effective ultra-rapid vitrification method (droplet vitrification) and evaluate its effects on post-thaw development and apoptosis-related gene expression in mouse zygotes. Presumptive zygotes were equilibrated for 3 min in equilibration medium and washed 3 times in vitrification solution. A drop (5 microL) of vitrification solution containing 10-12 embryos was placed directly onto surface of liquid nitrogen, with additional liquid nitrogen poured over the drop. For thawing and cryoprotectant removal, vitrified drops were put into dilution medium for 3 min, followed by M2 medium for 5 min. Although cleavage rate did not differ significantly among the control (90.8+/-2.8%; mean+/-S.E.M.), toxicity control (83.5+/-3.2%), and vitrified (86.2+/-3.1%) zygotes, rates of blastocyst and hatched blastocyst formation were lower (P<0.01) in vitrified zygotes (49.7+/-4.7% and 36.0+/-4.7%) and toxicity controls (47.3+/-4.6% and 40.3+/-4.6%) compared with controls (65.5+/-4.1% and 54.2+/-4.3%). Exposure of zygotes to vitrification solution, as well as the vitrification process, down-regulated the expression of Bax, Bcl2, and p53 genes in blastocysts. Although droplet vitrification was efficient and easy, it altered the transcriptional activities of Bax, Bcl2, and p53 genes in vitrified embryos, indicating a strong relationship between reduced developmental competence and the altered transcriptional activities of these genes.

Modeling extended lactations of Holsteins.

Modeling extended lactations for the US Holsteins is useful because a majority (>55%) of the cows in the present population produce lactations longer than 305 d. In this study, 9 empirical and mechanistic models were compared for their suitability for modeling 305-d and 999-d lactations of US Holsteins. A pooled data set of 4,266,597 test-day yields from 427,657 (305-d complete) lactation records from the AIPL-USDA database was used for model fitting. The empirical models included Wood (WD), Wilmink (WIL), Rook (RK), monophasic (MONO), diphasic (DIPH), and lactation persistency (LPM) functions; Dijkstra (DJ), Pollott (POL), and new-multiphasic (MULT) models comprised the mechanistic counterparts. Each model was separately tested on 305-d (>280 days in milk) and 999-d (>800 days in milk) lactations for cows in first parity and those in third and greater parities. All models were found to produce a significant fit for all 4 scenarios (2 parity groups and 2 lactation lengths). However, the resulting parameter estimates for the 4 scenarios were different. All models except MONO, DIPH, and LPM yielded residuals with absolute values smaller than 2 kg for the entire period of the 305-d lactations. For the extended lactations, the prediction errors were larger. However, the RK, DJ, POL, and MULT models were able to predict daily yield within a +/- 3 kg range for the entire 999-d period. The POL and MULT models (having 6 and 12 parameters, respectively) produced the lowest mean square error and Bayesian information criteria values, although the differences from the other models were small. Conversely, POL and MULT were often associated with poor convergence and highly correlated, unreliable, or biologically atypical parameter estimates. Considering the computational problems of large mechanistic models and the relative predictive ability of the other models, smaller models such as RK, DJ, and WD were recommended as sufficient for modeling extended lactations unless mechanistic details on the extended curves are needed. The recommended models were also satisfactory in describing fat and protein yields of 305-d and 999-d lactations of all parities.

Productive life including all lactations and longer lactations with diminishing credits.

Alternative measures of productive life (PL) were compared, and life expectancy factors were updated to replace estimates from 1993. Alternatives were proposed with extra credits for lactations longer than 10 mo and beyond 84 mo of age and for each calving so that an extremely long lactation would not receive more credits than multiple shorter lactations with dry periods between. Maximum credits per lactation of 10 mo (original PL), 12 mo, and unlimited were compared. The unlimited credits option either included or excluded a calf value equal to 2 mo of production and had credits given for all days either uniformly or based on lactation curves (diminishing credits). Standard lactation curves (first, second, and greater lactations) were estimated based on the test-day yields of Holstein cows remaining in lactation from a set of 903,579 lactation records. For the diminishing credits alternative, credit for a given day of a parity was derived using the predicted yield of the day proportional to the average daily yield of the first 305 d of second parity. Daily yields were deviations from a baseline of 13.62 kg. Heritabilities and genetic correlations were estimated by multitrait REML for alternative measures of PL, for longevity censored at various ages, and for yield traits and SCS in first parity. Data for REML analysis included records from 1,098,329 Holsteins born from 1994 through 1997 from 5,109 sires, and a relationship matrix among sires was included in the model. Lactations beyond 84 mo added little information. Heritability of PL was 0.073 with 10 mo, 0.069 with 12 mo, 0.068 and 0.067 with unlimited (uniform) lactation credits (with and without calf credits, respectively), and 0.070 with unlimited diminishing credits. Corresponding correlations among predicted transmitting abilities for PL and protein yield were 0.07, 0.06, 0.12, 0.23, and 0.09, all much lower than the 0.46 estimated in 1993. Heritability of PL with diminishing credits improved from 0.017 to 0.070 when censoring age increased from 36 to 96 mo. There was no further increase in heritability beyond 96 mo. Genetic correlation with the final PL was 0.87 when PL was censored at 36 mo, but the estimate increased steadily with the censoring age. The PL with diminishing credits, which was favorable in both economic and genetic aspects, was desirable in crediting cows for complete lactations.

Assessment of pronuclear formation following in vitro fertilization with bovine spermatozoa obtained after thermal insulation of the testis.

This study was conducted to follow the chronology of pronuclear formation in bovine zygotes after in vitro insemination with a population of spermatozoa having abnormal morphology. Semen samples were obtained and cryopreserved from four Holstein bulls before and after a scrotal insulation period of 48 h (Day 0). A pre-insult (Day 5) and a Day 20 post-insult semen sample were evaluated for morphology and used for IVF after standard swim-up sperm separation protocols. Pronuclear formation was scored on subpopulations of presumptive zygotes after they were fixed and stained at 3-h time intervals from 6 to 18 h post in vitro insemination (hpi). Post-thaw morphological evaluation of semen samples revealed a decrease in the percentages of normal spermatozoa in the post-insult samples compared with the pre-insult samples for Bull I (74-22%) and Bull III (68-1%). The sperm penetration rate decreased (P<0.05) between the pre- and post-insult samples for Bulls I (90-76%) and III (92-70%), but was not different for Bulls II (92-90%) and IV (78-85%). The pronuclear formation rates for post-insult zygotes for Bulls II and IV had comparable increases in development over time, whereas there was no increase in the pronuclear development for the zygotes from the post-insult samples for Bulls I and III, and generally a condensed sperm head was observed in the oolemma. At 18 hpi the fertilization rate between the pre- and post-insult samples for Bulls I (51-4%), II (88-75%) and III (94-2%) decreased (P<0.01), but there was no change for Bull IV (66%). In conclusion, we inferred that the failure in normal pronuclear formation was associated with an absence of normal decondensation of the penetrating spermatozoon; this suggested that the effect of morphologically abnormal spermatozoa occurred prior to cleavage, thus limiting early development.

Effects of inbreeding in the dam on dystocia and stillbirths in US Holsteins.

Dystocia scores were recorded by producers on 120,434 Holsteins (218,213 records) from 1985 through 1996; dystocia scores 3 to 5 were coded as difficult births. Stillbirths were recorded for deaths within the first 48 h after birth. Data were restricted to registered cows for pedigree completeness, and inbreeding coefficients were calculated using 5-generation pedigrees. Computational restrictions required that subsets of the data be created by choosing herds at random but using all records from selected herds. Effects of inbreeding in the dam were estimated in a sire-maternal grandsire (of the calf) threshold model using Gibbs sampling. The model included fixed effects of calf sex and inbreeding of the dam and random effects of herd-year-season of birth, additive genetic, and residual effects. First, second, and third parities were analyzed separately. Solutions for sex of calf and inbreeding from different parities were converted to expected change in probability of dystocia or stillbirth per 1% increase in inbreeding. Inbreeding effects were largest for first-parity cows giving birth to male calves at a 0.42% increase in probability of dystocia/1% increase in inbreeding. Effects of inbreeding for first-parity dams giving birth to female calves were smaller, 0.30%/1% increase in inbreeding. Incidence of stillbirths increased 0.25 and 0.20% for male and female calves/1% increase in inbreeding for first parity births. Effects of inbreeding on dystocia and stillbirths declined with parity. Effects of inbreeding were small, especially in later parities, but were consistently unfavorable.

The incidence of apoptosis after IVF with morphologically abnormal bovine spermatozoa.

Normal embryonic development depends on the maintenance of a population of normal healthy cells within each embryo. The aim of this study was to use a combination of apoptotic measures to assess differences in embryo quality after IVF with semen samples with high percentages of abnormal spermatozoa. Semen samples were obtained and cryopreserved from four Holstein bulls before (5 day prior) and after (2 week-post-insult; 2 week-PI and day 20; 3 week-PI) a scrotal insulation period of 48 h (day 0). The swim-up sperm separation method was used. The post-thaw morphology revealed a decrease (P < 0.01) in the percentages of normal spermatozoa in the 3 week-PI samples in comparison with the pre-insult samples for Bulls I and III (74-22.3 and 67.7-0.5%, respectively). The percentage of vacuolated spermatozoa increased significantly for Bull II. After 18 h of sperm-oocyte co-incubation, zygotes were cultured and subpopulations were removed from culture at day 8 and subjected to either the TUNEL or caspase assay. On day 8, caspase intensity increased significantly for both Bull I (217+/-147) and Bull III (229+/-98) for the 3 week-PI embryo groups compared to the equivalent embryo groups for Bull II (98+/-115) and Bull IV (90+/-111). In conclusion, the inability to consistently measure apoptosis with TUNEL alone complicated the assessment of differences in embryo quality. Thus, it is uncertain exactly when during early pre-implantation development the differences in embryo quality are first manifest. Despite discrepancies, our results clearly indicated a difference in the embryo quality between embryos obtained after IVF with semen samples from bulls that had an intense response to scrotal insulation.

Comparison of three estrus detection systems during summer in a large commercial dairy herd.

The objective of the study was to compare three systems for estrus detection and combinations of these systems on a large commercial dairy (1075 lactating cows) during stress of summer heat. At 37-45 days in milk (DIM), 255 cows were fitted with a HeatWatch device (HW; DDx Inc., Denver, CO), an activity sensor ALPRO (ALPRO; DeLaval Inc., Kansas City, MO), and visually observed (VO) three times daily. Pregnancy status was determined by uterine palpation per rectum 35-49 days following artificial insemination (AI). Effects of DIM, parity, standing events, inseminator, and interval between onset of estrus and AI on conception rates were determined using logistic regression. Efficiencies for detection of estrus, determined by comparing detected periods of estrus with a theoretical total of 570 periods, were 49.3% (VO), 37.2% (ALPRO), 48.0% (HW), and 80.2% for all three systems simultaneously. Conception rates (LSM+/-S.E.) for cows detected by one or more of the three systems were 6.2+/-3.9 for VO, 19.8+/-5.6 for ALPRO, 17.3+/-5.0 for HW, 22.8+/-7.0 for VO+ALPRO, 26.9+/-4.6 for VO+HW, 23.2+/-5.2 for ALPRO+HW, and 18.4+/-4.7 for VO+ALPRO+HW. Inseminations performed during no and mild heat stress (temperature-humidity index; THI< or =76) had greater conception rate (P<0.05; 38.8%) compared to AI performed during moderated heat stress conditions (THI>76; 17.6%). Number of mounts were higher for primiparous versus multiparous cows (P<0.05). Cows over 80 DIM during estrus exhibited fewer (P<0.05) standing events. The highest conception rate occurred with the combination of VO+HW, which confirms the premise that combination of multiple systems enhances both the efficiency and accuracy of estrus detection.

Bovine embryo development after IVF with spermatozoa having abnormal morphology.

The study was conducted to evaluate the effects of scrotal insulation on semen samples collected from bulls on embryonic development after IVF. Semen samples were obtained and cryopreserved from four Holstein bulls before and after a scrotal insulation period of 48 h (Day 0). Three types of samples were used for IVF: (1) semen from the test bulls collected 5 d prior to scrotal insulation (pre-insult); (2) semen from Day 13 (2-week post-insult; 2-week PI); and (3) semen from Day 20 (3-week PI). After 18 h of sperm-oocyte co-incubation, the zygotes were cultured for 8 d when a developmental score (0=degenerate, 1=2-cell embryo through 5=blastocyst) was assigned to each embryo. The post-thaw morphological evaluation of sperm samples revealed a decrease (P<0.01) in the percentages of normal spermatozoa in the 3-week PI samples in comparison with the pre-insult samples for Bulls I and III (74-22.3% and 67.7-0.5 %, respectively). The percentage of vacuolated spermatozoa increased significantly for Bull II. The cleavage and blastocyst formation rates and embryo development scores were affected (P<0.01) by the interaction of bull by sample collection time. For Bulls I and III (severe responders) the scrotal insulation effects persisted from the time of cleavage through blastocyst formation. In contrast, the cleavage and blastocyst formation rates for Bulls II and IV were unaffected, despite high percentages of vacuolated spermatozoa present in the post-insult samples for Bull II. In conclusion, the use of scrotal insulation to elevate scrotal temperature was an effective method to obtain semen samples with high percentages of abnormal spermatozoa. The decrease in embryonic development after IVF when using spermatozoa with morphological abnormalities seemed to be multifaceted and related to changes in head morphology.

Effect of increasing energy and protein intake on mammary development in heifer calves.

The objective of this study was to determine if increased energy and protein intake from 2 to 14 wk of age would affect mammary development in heifer calves. At 2 wk of age, Holstein heifer calves were assigned to 1 of 4 treatments in a 2 x 2 factorial arrangement with 2 levels of protein and energy intake (moderate, M; high, H) in period 1 (2 to 8 wk of age) and 2 levels of protein and energy intake (low, L; high, H) in period 2 (8 to 14 wk of age), so that mean initial body weights were approximately equal for all 4 treatments (ML, MH, HL, and HH). The M diet in period 1 consisted of a standard milk replacer (21.3% CP, 21.3% fat) fed at 1.1% of BW on a DM basis and a 16.5% CP grain mix fed at restricted intake to promote 400 g of daily gain, whereas the L diet in period 2 consisted only of the grain mix. The H diet in period 1 consisted of a high-protein milk replacer (30.3% CP, 15.9% fat) fed at 2.0% of body weight on a DM basis and a 21.3% CP grain mix available ad libitum. In period 2, the H diet consisted of just the 21.3% grain mix. Calves were gradually weaned from milk replacer by 7 wk and slaughtered at 8 (n = 11) or 14 wk of age (n = 41). Parenchyma from the distal region, midgland, and proximal region relative to the teat from one half of the udder was collected, fixed, and embedded in paraffin. The other half of the gland was used to determine parenchymal mass, protein, fat, DNA, RNA, and extraparenchymal mass. Total parenchymal tissue, parenchymal DNA, parenchymal RNA, and concentrations of DNA and RNA were higher for calves on the H diet during period 1, but were not affected by diet during period 2. Parenchymal fat percentage was increased by the H diet during period 2. The H diet increased extraparenchymal fat during both periods. The area of parenchyma occupied by epithelium was not affected by treatment, but at the end of period 2, the percentage of proliferating epithelial cells as indicated by Ki67, an marker of cell proliferation, expression was greater for calves on the M diet in period 1 compared with calves on the H diet in period 1. Diets did not influence parenchymal protein percentage or the ratio of RNA to DNA. Higher energy and protein intake from 2 to 8 wk of age increased parenchymal mass and parenchymal DNA and RNA in mammary glands of heifer calves without increasing deposition of parenchymal fat. Diet also influenced histological development of mammary parenchyma and subsequent proliferation of ductal epithelial cells. Implications of these effects for future milk production potential are unknown.

Comparisons of Holsteins with Brown Swiss and Jersey cows on the same farm for age at first calving and first calving interval.

Our objective was to evaluate breed differences for heat-stress resistance as reflected by age at first calving and first calving interval. We examined the effect of geographic location and birth season on age at first calving, and geographic location and first calving season on first calving interval on Holsteins and Jerseys, and Holsteins and Brown Swiss located on the same farm. We defined 7 regions within the United States: Northwest, Central north, Northeast, Central, Central south, Southwest, and Southeast, and analyzed 7 individual states: Ohio, Wisconsin, Oregon, California, Arizona, Texas, and Florida. Brown Swiss were older than Holsteins at first calving (833 +/- 2.4 vs. 806 +/- 2.0 d in regions, and 830 +/- 3.1 vs. 803 +/- 2.4 d in states), but Holsteins and Brown Swiss did not differ for first calving interval. Jerseys were younger than Holsteins at first calving and had shorter first calving intervals. In data from individual states, Holsteins housed with Brown Swiss were older at first calving than were Holsteins housed with Jerseys (800 +/- 2.7 vs. 780 +/- 2.5 d). Holsteins housed with one breed or the other were analyzed as a separate data set, and referred to as "type of Holstein." The interaction of "type of Holstein" with first calving season was highly significant for first calving interval. Geographic location and season effects were smaller for Jerseys than for Holsteins; thus, Jerseys showed evidence of heat-stress resistance with respect to Holsteins. Management modified age at first calving in Holsteins to more nearly match that of the other breed. Longer calving intervals might be partly due to voluntary waiting period to breed the cows.

Pregnancy rates after timed AI of heifers following removal of intravaginal progesterone inserts.

Reproductive performance of dairy heifers was compared for each of 2 synchronization protocols: The first group of 54 heifers was synchronized using intravaginal progesterone inserts (CIDR) plus estradiol cypionate (ECP) on d 0, PGF(2alpha) on d 7, and ECP again on d 8 (CIDR-ECP); a second group of 56 heifers was synchronized using CIDR and ECP on d 0, PGF(2alpha) on d 7, and GnRH on d 9 (CIDR-GnRH). All heifers received timed artificial insemination (TAI) at 48, 56, or 72 h after CIDR removal on d 7. Pregnancy diagnosis was conducted by ultrasonography 32 +/- 1 d post AI to confirm pregnancy and at 60 +/- 1 d post AI to determine embryo survival. Ovaries were monitored by ultrasonography daily from d 0 to 7 and twice daily from d 8 to ovulation to examine emergence of a new wave of follicles, size of the ovulatory follicle, and timing of ovulation on 15 heifers per protocol. New follicular development was detected 3.7 +/- 0.2 d after CIDR insertion. Heifers receiving CIDR-ECP had a shorter interval from CIDR removal to ovulation than heifers receiving CIDR-GnRH (63.8 +/- 3.0 vs. 71.6 +/- 2.3 h, respectively); however, ovulation occurred 39.8 +/- 3.0 h after ECP or 23.6 +/- 2.3 h after GnRH. Diameters of ovulatory follicles did not differ between treatments. Overall pregnancy rate for synchronized heifers was 60.1%, and embryo survival was 98%. Pregnancy rate for heifers synchronized with CIDR-ECP was 63.0% and similar to that in heifers synchronized with CIDR-GnRH (57.1%). Pregnancy rate was affected by time of AI for heifers synchronized using CIDR-ECP but not for those synchronized with CIDR-GnRH. Heifers in the CIDR-ECP group that were inseminated 56 h after CIDR removal had a higher pregnancy rate (81.0%) compared with heifers inseminated 48 (66.7%) or 72 h (50.0%) after CIDR removal. Either ECP or GnRH used in a CIDR-based TAI program in dairy heifers can achieve acceptable reproductive performance.