Lactational performance effects of supplemental histidine in dairy cows: A meta-analysis.

The objective of this meta-analysis was to examine the effects of supplemental His on lactational performance, plasma His concentration and efficiency of utilization of digestible His (EffHis) in dairy cows. The meta-analysis was performed on data from 17 studies published in peer-reviewed journals between 1999 and 2022. Five publications reported data from 2 separate experiments, which were included in the analyses as separate studies, therefore resulting in a total of 22 studies. In 10 studies, His was supplemented as rumen-protected (RP) His; in 1 study, 2 basal diets with different dHis levels were fed; and in the remaining experiments, free His was infused into the abomasum (4 studies), the jugular vein (3 studies) or deleted from a mixture of postruminally infused AA (4 studies). The main forages in the diets were corn silage in 14 and grass silage in 8 studies. If not reported in the publications, the supplies of dietary CP, metabolizable protein (MP), net energy of lactation, and digestible His (dHis) were estimated using NRC (2001). An initial meta-analysis was performed to test the standard mean difference (SMD; raw mean difference of treatment and control means divided by the pooled standard deviation of the means), that is, effect size, and the corresponding 95% confidence interval (CI) in production parameters between His-supplemented groups versus control. Further, regression analyses were also conducted to examine and compare the relationships between several response variables and dHis supply. Across studies, His supplementation increased plasma His concentration (SMD = 1.39; 95% CI: 1.17-1.61), as well as DMI (SMD = 0.240; 95% CI: 0.051-0.429) and milk yield (MY; SMD = 0.667; 95% CI: 0.468-0.866), respectively. Further, milk true protein concentration (MTP; SMD = 0.236; 95% CI: 0.046-0.425) and milk true protein yield (MTPY; SMD = 0.581; 95% CI: 0.387-0.776) were increased by His supplementation. Notably, the increase in MTP concentration and MTPY were 3.9 and 1.3 times greater for studies with MP-deficient (according to NRC 2001) diets compared with studies with MP-adequate diets. The regression analyses revealed that production parameters (DMI, MY, and MTPY) responded in a nonlinear manner to increasing His supply. Further, we detected a difference in the magnitude of change in MTPY and plasma His concentration with the level of His supply and between His supplementation methods, being greater for infused His compared with RPHis. Lastly, a linear and negative relationship between EffHis and the ratio of total digestible His to net energy for lactation supply was observed, indicating an important interaction between dHis and energy supply and EffHis (i.e., utilization of dHis to support protein export). Overall, these analyses confirm His as an important AA in dairy cattle nutrition.

Artificial insemination of cattle: Description and assessment of a training program for veterinary students.

The objective was to assess the effectiveness of a comprehensive artificial insemination (AI) training program designed to facilitate an understanding of the breadth of the AI process, including AI skill acquisition, for preclinical veterinary students. Participants (n = 303) were enrolled at the Ross University School of Veterinary Medicine (Basseterre, St. Kitts, West Indies). The 2-d AI training program (n = 20) consisted of ∼8 h of instruction and ∼8 h of demonstration and hands-on activity. Oral presentations were used to deliver educational content, followed by video clips, discussion, demonstrations, and hands-on activity. Reproductive anatomy and physiology of the estrous cycle, AI sire acquisition, collection, evaluation, cryopreservation and distribution of conventional and sexed semen, storage and handling of frozen semen, use of synchronization protocols, accurate and efficient detection of estrus, and correct AI technique were discussed. True or false pre- and posttests were used to determine the level of knowledge gained by participants during the AI training program. Preclinical veterinary students were required to complete a semen handling and AI technique practical exam to achieve a certificate of completion. Participant program evaluations conducted at the conclusion of the program indicated that veterinary students found the content, structure, discussion, demonstrations, and hands-on activities to be appropriate and useful. No negative comments were offered about the training program, instructor, or activity coinstructors. The AI training program increased the posttest knowledge scores of veterinary students by 22 percentage points. Only 1 participant was unable to achieve a certificate of completion due to failure of the semen handling and AI technique practical exam. These results provide evidence that the AI training program was relevant and effective and that it offered information and skill acquisition with immediate field application.

Short communication: Reproduction outcomes in dairy heifers following a 14-d progesterone insert presynchronization protocol.

The objectives were to evaluate pregnancy per artificial insemination (AI), days to first AI, and proportion pregnant within 7 d of AI eligibility in dairy heifers subjected to presynchronization compared with dairy heifers not presynchronized. Thirty days before AI eligibility, Holstein heifers were assigned randomly to 1 of 3 groups: 14-d controlled internal drug release (CIDR; containing progesterone) presynchronization, PGF2α presynchronization, or control (no presynchronization). Heifers in the 14-d CIDR presynchronization treatment (n = 119) received a CIDR on d -30, which was removed on d -16, followed by an injection of PGF2α upon entry to the breeding program (d 0). Heifers in the PGF2α presynchronization treatment (n = 118) received an injection of PGF2α on d -11 and d 0. Control heifers (n = 121) were not presynchronized and received an injection of PGF2α on d 0. All heifers received tail paint on d 0 to facilitate once-daily detection of estrus (based on paint removal). Heifers detected in estrus received AI with conventional semen on the same morning as detected estrus. Generalized linear mixed models were used to assess mean treatment differences. Following PGF2α treatment on d 0, more heifers were detected in estrus in the first 7 d after eligibility in the 14-d CIDR group (95.8%) compared with the PGF2α (74.6%) and control (66.9%) groups. Days to first AI differed between treatments (14-d CIDR = 3.6 d vs. PGF2α = 5.0 d vs. control = 6.8 d). Pregnancy per AI for first AI within 7 d of eligibility was 71.9% (14-d CIDR), 58.0% (PGF2α), and 61.7% (control), and differed between 14-d CIDR and PGF2α heifers. Presynchronization with a 14-d CIDR increased the proportion of heifers pregnant in the first 7 d of eligibility (14-d CIDR = 68.9% vs. PGF2α = 43.2% vs. control = 41.3%). Projected days on feed (d 0 to projected calving date) were 295 (14-d CIDR), 302 (PGF2α), and 305 (control), and were different between the 14-d CIDR and control heifers. The potential economic benefit to the producer was $15.85 per heifer presynchronized with a 14-d CIDR protocol compared with the control group. Treatment of dairy heifers with a 14-d CIDR effectively presynchronized estrus, resulting in a greater proportion detected in estrus, reduced days to first AI, and an increased proportion of heifers pregnant within the first 7 d after breeding eligibility compared with heifers presynchronized with a single PGF2α injection and control heifers.

Pregnancy outcomes are not improved by administering gonadotropin-releasing hormone at initiation of a 5-day CIDR-Cosynch resynchronization protocol for lactating dairy cows.

Using a 5-d controlled internal drug-release (CIDR)-Cosynch resynchronization protocol, the objective of this study was to determine the effect of the initial GnRH injection on pregnancy per artificial insemination (P/AI) to the second artificial insemination in lactating Holstein dairy cows. On 37 ± 3 d (mean ± standard deviation) after the first artificial insemination, and upon nonpregnancy diagnosis (d 0 of the experiment), lactating cows eligible for a second artificial insemination (n = 429) were enrolled in a 5-d CIDR-Cosynch protocol. On d 0, all cows received a CIDR insert and were assigned randomly to receive the initial GnRH injection (GnRH; n = 226) of the protocol or no-GnRH (n = 203). Blood samples were collected from a sub-group of cows (n = 184) on d 0 and analyzed for progesterone (P4) concentration. On d 5, CIDR inserts were removed, and all cows received 1 injection of PGF2α. On d 6 and 7, cows were observed once daily by employees for tail-chalk removal, and cows detected in estrus on d 6 or 7 received artificial insemination that day (EDAI), and did not receive the final GnRH injection. The remaining cows not detected in estrus by d 8 received GnRH and timed artificial insemination (TAI). Pregnancy status was confirmed by transrectal palpation of uterine contents at 37 ± 3 d (mean ± standard deviation) after the second artificial insemination. Eliminating the initial GnRH injection had no effect on P/AI compared with cows receiving GnRH (27 vs. 21%), respectively. Similarly, method of insemination (EDAI vs. TAI) and its interaction with treatment had no effect on P/AI. Primiparous cows had greater P/AI than multiparous cows (31 vs. 21%). Mean P4 concentrations (n = 184) at the initiation of the protocol did not differ between treatments (4.51 ± 0.35 ng/mL no-GnRH vs. 3.96 ± 0.34 ng/mL of GnRH). When P4 concentrations were categorized as high (≥1 ng/mL) or low (<1 ng/mL), P/AI tended to be greater for high P4 concentrations (n = 136) compared with low (n = 48) P4 concentrations (26 vs. 16%, respectively). No differences were observed in the proportion of cows with high or low P4 between treatments. Collectively, these results provide evidence that eliminating the initial GnRH in a 5-d CIDR-Cosynch resynchronization protocol for lactating dairy cows did not reduce P/AI in this study.

Short communication: Comparison of the GreenFeed system with the sulfur hexafluoride tracer technique for measuring enteric methane emissions from dairy cows.

The objective of this study was to compare 2 commonly used techniques for measuring methane emissions from ruminant animals: the GreenFeed (GF) system and the sulfur hexafluoride (SF6) technique. The study was part of a larger experiment in which a methane inhibitor, 3-nitrooxypropanol, fed at 4 application rates (0, 40, 60, and 80 mg/kg of feed dry matter) decreased enteric methane emission by an average of 30% (measured by both GF and SF6) in a 12-wk experiment with 48 lactating Holstein cows fed a total mixed ration. The larger experiment used a randomized block design and was conducted in 2 phases (February to May, phase 1, and June to August, phase 2), with 2 sets of 24 cows in each phase. Using both GF and SF6 techniques, methane emission data were collected simultaneously during experimental wk 2, 6, and 12 (phase 1) and 2, 9, and 12 (phase 2), which corresponded to a total of 6 sampling periods. During each sampling period, 8 spot samples of gas emissions (staggered over a 3-d period) were collected from each cow using GF, as well as 3×24-h collections using the SF6 technique. Methane emission data were averaged per cow for the statistical analysis. The mean methane emission was 373 (standard deviation=96.3) and 405 (standard deviation=156) g/cow per day for GF and SF6, respectively. Coefficients of variation for the 2 methods were 25.8 and 38.6%, respectively; correlation and concordance between the 2 methods were 0.40 and 0.34, respectively. The difference in methane emission between the 2 methods (SF6 - GF) within treatment was from 46 to 144 and 24 to 27 g/d for phases 1 and 2, respectively. In the conditions of this experiment, the SF6 technique produced larger variability in methane emissions than the GF method. The overall difference between the 2 methods was on average about 8%, but was not consistent over time, likely influenced by barn ventilation and background methane and SF6 concentrations.

Relationships of feeding behaviors with average daily gain, dry matter intake, and residual feed intake in Red Angus-sired cattle.

Feeding behavior has the potential to enhance prediction of feed intake and to improve understanding of the relationships between behavior, DMI, ADG, and residual feed intake (RFI) in beef cattle. Two cohorts, born in 2009 and 2010, the progeny of Red Angus bulls (n = 58 heifers and n = 53 steers), were evaluated during the growing phase, and the latter group of steers was also evaluated during the finishing phase. All behavior analyses were based on 7 feeding behavior traits (bunk visit frequency, bunk visit duration [BVDUR], feed bout frequency, feed bout duration, meal frequency, meal duration, and average meal intake) and their relationships with ADG, DMI, and RFI. During the growing phase, feeding duration traits were most indicative of DMI with positive correlations between BVDUR and DMI for cohort 1 steers, growing phase (n = 28, r = 0.52, P = 0.00); cohort 2 steers, growing phase (n = 25, r = 0.44, P = 0.01); and cohort 2 heifers, growing phase (n = 29, r = 0.28 P = 0.05). There were similar trends toward correlation of BVDUR and RFI for both steer groups and cohort 1 heifers, growing phase (C1HG; n = 29; r = 0.27, P = 0.06; r = 0.30, P = 0.07; and r = 0.26, P = 0.08, respectively). Feed bout frequency was correlated with ADG in C1HG and in cohort 2 steers, finishing phase (r = -0.31, P = 0.04, and r = 0.43, P = 0.01, respectively). Feed bout duration was correlated with ADG in heifer groups (r = 0.29 and r = 0.28, P = 0.05 for both groups) and DMI for all growing phase animals (r = 0.29 to 0.55, P ≤ 0.05 for all groups). Evaluation of growing vs. finishing phase steer groups suggests that all behaviors, RFI, and DMI, but not ADG, are correlated through the growing and finishing phases (P ≤ 0.01 for all variables excluding ADG), implying that feeding behaviors determined during the growing phase are strong predictors of DMI in either life stage. Sire maintenance energy EPD effects (measured as high or low groups) on progeny feeding behaviors revealed a difference in meal duration with a tendency to differ in average meal intake (P = 0.01 and P = 0.07, respectively). Feeding behavior duration traits may be useful predictors of DMI in Red Angus cattle.

Relationships of feeding behaviors with efficiency in RFI-divergent Japanese Black cattle.

New approaches to limit expenses associated with input, without compromising profit, are needed in the beef industry. Residual feed intake (RFI) is an efficiency trait that measures variation in feed intake beyond maintenance, growth, and body composition. The addition of feeding behavior analysis to standard RFI tests may provide an approach to more readily identify feed-efficient cattle. The current study analyzes 7 feeding behaviors (BVFREQ: bunk visit frequency, BVDUR: bunk visit duration, FBFREQ: feed bout frequency, FBDUR: feed bout duration, MFREQ: meal frequency, MDUR: meal duration, and AMINT: average meal intake) and their relationships with RFI, ADG, and DMI in Japanese Black (Wagyu) cattle. Three cohorts of yearling Wagyu animals were studied using a standard 70-d RFI test, and data from divergent ( ± 0.5 SD from population RFI mean) subsets of animals were analyzed for feeding behaviors [n = 58, bulls on high-concentrate diet (C1); n = 36, bulls on a lower-concentrate diet (C2); n = 34, heifers on a lower-concentrate diet (C3)]. The following behaviors were correlated with ADG: BVFREQ (r = 0.32, P = 0.01; C1 bulls), BVDUR (r = 0.42, P = 0.01, C2 bulls), FBFREQ (r = 0.37, P < 0.01; C1 bulls), FBDUR (r = 0.46, P < 0.01, C1 bulls), and MFREQ (r = 0.42, P < 0.01, C2 bulls). Behaviors were trending or significantly correlated with DMI for all cases except for MFREQ for C3 and AMINT for C2. Residual feed intake was positively correlated with MDUR across all cohorts (r = 0.31, P = 0.02; r = 0.38, P = 0.02; r = 0.54, P ≥ 0.01, respectively). For C2 bulls and C3 heifers, RFI was positively correlated with behavior frequency categories (BVFREQ; r = 0.44, P = 0.01; r = 0.60, P ≤ 0.01, respectively, and FBFREQ r = 0.46, P ≤ 0.01; r = 0.60, P ≤ 0.01, respectively). Bunk visit frequency and FBFREQ were highly correlated with RFI status (high or low) in C2 bulls and C3 heifers. Behavior duration categories (BVDUR, FBDUR, and MDUR) were most correlated with efficiency status in C1 bulls. However, behavior frequency categories (BVFREQ and FBFREQ), as well as MDUR, were most correlated with efficiency status in C2 bulls and C3 heifers. Inclusion of meal duration measurements when evaluating RFI provides an additional tool in understanding the drivers of variation in this important trait in Wagyu cattle. The present study provides new insights into feed intake patterns of a beef breed for which there are few reports of feeding behavior.

An examination of the association of serum IGF-I concentration, potential candidate genes, and fiber type composition with variation in residual feed intake in progeny of Red Angus sires divergent for maintenance energy EPD.

Investigating the genetic and physiological drivers of postweaning residual feed intake (RFI) and finishing phase feed efficiency (FE) may identify underlying mechanisms that are responsible for the variation in these complex FE traits. The objectives were 1) to evaluate the relationship of serum IGF-I concentration and muscle gene expression with postweaning RFI and sire maintenance energy (MEM) EPD and 2) to determine fiber type composition as it relates to postweaning RFI and finishing phase FE. Results indicate that RFI and serum IGF-I concentration were not associated (P > 0.05); however, negative correlations (P < 0.05) between sire MEM EPD and serum IGF-I concentration were observed. Gene expression differences between high- and low-RFI animals were observed in cohort 1, where IGFBP5 expression was greater (P < 0.05) in high-RFI animals. When animals were grouped according to sire MEM EPD, the low MEM EPD group of cohort 1 showed greater muscle mRNA expression (P < 0.01) of fatty acid synthase (FASN) and marginally (P < 0.10) greater expression of IGFBP5 and C/EBP alpha (C/EBPα) whereas the high MEM EPD group of cohort 2 had greater muscle mRNA expression of IGFBP2 (P < 0.05) and C/EBPα (P ≤ 0.01) and marginally (P < 0.10) greater expression of IGFBP3. Biopsy tissue samples collected at harvest revealed that the percentage of type IIa fibers was lower (P ≤ 0.05) in high-RFI steers, with a similar trend (P < 0.10) being observed in high finishing phase FE steers. The percentage of type IIb fibers was higher (P < 0.05) in high-RFI (and finishing phase FE) steers than in low-RFI (and finishing phase FE) steers. There was a marginal, negative correlation between RFI and type I (r = -0.36, P = 0.08) and IIa (r = -0.37, P = 0.07) fiber percentages and a positive correlation (r = 0.48, P = 0.01) between RFI and type IIb fiber percentage whereas finishing phase FE was negatively correlated (r = -0.43, P = 0.03) with type I fiber percentage and positively correlated (r = 0.44, P = 0.03) with type IIb fiber percentage. Therefore, our data indicate that 1) serum IGF-I (collected at weaning) is not an indicator of postweaning RFI, 2) the GH-IGF axis appears to have some involvement with RFI at the molecular level; however, muscle gene expression results were not consistent across cohorts, and 3) low-RFI animals may have the ability to more efficiently maintain and accrete muscle mass due to their fiber type composition, specifically a greater proportion of type I fibers.

Relationships among performance, residual feed intake, and product quality of progeny from Red Angus sires divergent for maintenance energy EPD.

Energy expenditure is a physiological process that may be closely associated with residual feed intake (RFI). The maintenance energy (ME(M)) EPD was developed by the Red Angus Association of America (RAAA) and is used as an indicator of energy expenditure. The objectives of this study were to evaluate and quantify the following relationships using progeny of Red Angus (RA) sires divergent for ME(M) EPD: 1) postweaning RFI and finishing phase feed efficiency (FE), 2) postweaning RFI and end-product quality, and 3) postweaning RFI and sire ME(M) EPD. A total of 12 RA sires divergent for ME(M) EPD were chosen using the RAAA-generated ME(M) EPD values and were partitioned into 2 groups: high ME(M) EPD (≥4 Mcal/mo) and low ME(M) EPD (<4 Mcal/mo), based on the breed average of 4 Mcal/mo. Commercial crossbred cows were inseminated to produce 3 cohorts of progeny, which were tested for postweaning RFI (cohorts 1, 2, and 3) and finishing phase FE (cohorts 1 and 3). Results indicate that postweaning RFI and finishing phase FE of steer progeny tended to be positively correlated (r = 0.38; P = 0.06) in cohort 1 and were positively correlated (r = 0.50; P = 0.001) in cohort 3. In addition, postweaning RFI was not phenotypically correlated (P > 0.05) with any carcass traits or end-product quality measurements. Sire ME(M) EPD was phenotypically correlated (P < 0.05) with carcass traits in cohort 1 (HCW, LM area, KPH, fat thickness, and yield grade) and cohort 2 (KPH and fat thickness). Since variation in measured LM area was not explained by the genetic potential of rib eye area EPD, and therefore, the observed correlation between sire ME(M) EPD and measured LM area may suggest an association between ME(M) EPD and LM area. A correlation (r = 0.24; P = 0.02) was observed between postweaning RFI and ultrasound intramuscular fat percentage in cohort 2 but was not detected in cohorts 1 or 3. In addition, no phenotypic relationship was observed (P > 0.05) between progeny postweaning RFI and sire ME(M) EPD. Therefore, results suggest 1) RFI measured during the postweaning growth phase is indicative of FE status in the finishing phase, 2) neither RFI nor sire ME(M) EPD negatively affected carcass or end-product quality, and 3) RFI and sire ME(M) EPD are not phenotypically associated.

Variability in feed and total mixed ration neutral detergent fiber and crude protein analyses among commercial laboratories.

The objective of this study was to assess the variability in amylase-treated neutral detergent fiber (aNDF) and crude protein (CP) analyses of feed and total mixed ration (TMR) samples among feed analysis laboratories. Two TMR were prepared that varied in the dry matter proportion of forage and concentrates: 45% forage (LF-TMR) versus 60% forage (HF-TMR). Replicated TMR and individual feed samples were dried, ground through a 4-mm screen, and sent to 10 commercial and 4 research or development laboratories for aNDF and CP analyses. Laboratories were asked to complete a detailed questionnaire regarding the aNDF procedure used. Variability in aNDF and CP analyses was assessed using univariate statistics and mixed modeling procedures. Significant variability in the aNDF analysis of individual feeds was found among the participating laboratories. The variability was particularly large for low-aNDF feeds such as distillers and barley grains. The variability among laboratories in the aNDF analysis of low-fiber TMR was greater than of high-fiber TMR, with the most likely reason being their greater proportions of grains and protein concentrates and the effect of variation in the aNDF protocols, particularly α-amylase use, on the analysis of these types of feeds. Variability due to the technique used for aNDF analysis was not statistically significant when outlier labs using the filter bag technique were removed; however, laboratories using the filter bag technique tended to produce more variable results than did laboratories using variation of the crucible technique (SE=2.542 vs. 0.930, respectively). Calculated aNDF values for TMR, based on proportions and aNDF analysis of individual feeds, were slightly greater than analyzed aNDF values for TMR. Results from this ringtest emphasize the need for feed analysis laboratories to follow the official aNDF method exactly. Variation within and among laboratories can be reduced by replicating analysis and including reference materials in each analytical run. Results of CP analysis were more consistent among laboratories, and variability in CP analysis of individual feeds or TMR was marginally acceptable.

Effect of clinical mastitis and other diseases on reproductive performance of Holstein cows.

The objective of this study was to evaluate the effect of clinical mastitis and (or) other diseases on reproductive performance in lactating Holstein cows. Cows (n=967) from a commercial dairy farm were divided into four groups retrospectively: cows with clinical mastitis and other diseases (MD, n=54), clinical mastitis only (M, n=154), other diseases only (D, n=187), and cows with no record of clinical mastitis or other diseases (H, n=572). Days in milk at first service (DIMFS), services per conception (S/C), days not pregnant (DNP), the rate at which animals became pregnant over time and the proportion of cows that remained non-pregnant during 224 days of lactation were evaluated. Groups MD and M had greater (P<0.05) DNP compared with H (155+/-15 and 140+/-5 vs. 88+/-2, respectively). Moreover, MD and M had greater (P<0.05) S/C compared with H (3.0+/-0.4 and 2.1+/-0.1 vs. 1.6+/-0.1, respectively). The rate at which animals became pregnant over time was less (P<0.05) for MD and M and tended (P=0.1) to be less for D when compared with H. In addition, proportion of cows that remained non-pregnant by 224 days of lactation was greater (P<0.05) in MD, M, and D compared with H. Cows with mastitis were also divided into three groups according to the day of occurrence of the first case of clinical mastitis: (1) clinical mastitis occurred before 56 days postpartum (MP1); (2) clinical mastitis occurred between 56 and 105 days after parturition (MP2); and (3) clinical mastitis occurred after 105 days postpartum (MP3) Regardless of the time of occurrence, DNP was greater (P<0.05) for cows with mastitis compared with H. Time of mastitis occurrence affected S/C in that cows in MP2 and MP3 had a greater S/C compared with H cows (P<0.05). Reproductive efficiency was decreased by the presence of clinical mastitis alone because a greater proportion of cows with mastitis remained non-pregnant over time. Moreover, a greater proportion of cows with mastitis or diseases remained non-pregnant by 224 postpartum. Furthermore, the negative effects on reproduction were exacerbated when cows experienced both clinical mastitis and other diseases.

Effect of barley and its amylopectin content on ruminal fermentation and nitrogen utilization in lactating dairy cows.

The effect of type of grain (corn vs. barley) and amylopectin content of barley grain (normal vs. waxy) on ruminal fermentation, digestibility, and utilization of ruminal ammonia nitrogen for milk protein synthesis was studied in a replicated 3 x 3 Latin square design trial with 6 lactating dairy cows. The experimental treatments were (proportion of dietary dry matter): CORN, 40% corn grain, NBAR, 30% normal Baronesse barley:10% corn grain, and WBAR, 30% high-amylopectin (waxy) Baronesse barley:10% corn grain. All grains were steam-rolled and fed as part of a total mixed ration. The NBAR and WBAR diets resulted in increased ruminal ammonia concentrations compared with CORN (8.2, 7.4, and 5.6 mM, respectively), but other ruminal fermentation parameters were not affected. Ruminal digestibility of dietary nutrients and microbial protein synthesis in the rumen were also not affected by diet. Corn grain had greater in situ effective ruminal dry matter degradability (62.8%) than the barley grains (58.2 and 50.7%, respectively), and degradability of the normal barley starch was greater than that of the waxy barley (69.3 and 58.9%, respectively). A greater percentage of relative starch crystallinity was observed for the waxy compared with the normal barley grain. Total tract apparent digestibility of dry matter and organic matter were decreased by WBAR compared with CORN and NBAR. Total tract starch digestibility was greater and milk urea nitrogen content was lower for CORN compared with the 2 barley diets. In this study, the extent of processing of the grain component of the diet was most likely the factor that determined the diet responses. Minimal processing of barley grain (processing indexes of 79.2 to 87.9%) reduced its total tract digestibility of starch compared with steam-rolled corn (processing index of 58.8%). As a result of the increased ammonia concentration and reduced degradability of barley dry matter in the rumen, the utilization of ruminal ammonia nitrogen for microbial protein synthesis was decreased with the barley diets compared with the corn-based diet. In this study, waxy Baronesse barley was less degradable in the rumen and the total digestive tract than its normal counterpart. The most likely reasons for these effects were the differences in starch characteristics and chemical composition, and perhaps the different response to processing between the 2 barleys.

Short communication: Conception rates following detection of estrus and timed AI in dairy cows synchronized using GnRH and PGF2alpha.

The objective of this study was to compare conception rates of cows exhibiting spontaneous estrus and receiving artificial insemination (AI) before completion of a timed AI protocol with cows that did not display estrus spontaneously, but were inseminated after 1 of 3 GnRH-PGF2alpha protocols. Cows (n = 432) in 2 herds were administered GnRH on d -7 and were tail-chalked daily. Cows detected in estrus before d 0 were inseminated immediately. Cows not detected in estrus by d 0 were administered PGF2alpha and were tail-chalked daily until 48 h after PGF2alpha. Cows detected in estrus from d -7 to 48 h after PGF2alpha were inseminated and designated as treatment A (n = 46). Cows not detected in estrus and not inseminated by 48 h after PGF2alpha were assigned randomly to receive either GnRH 48 h after PGF2alpha and timed AI 16 h later (treatment B; n = 132), or GnRH and timed AI 64 h after PGF2alpha (treatment C; n = 127), or timed AI 64 h after PGF2alpha (treatment D; n = 127). Pregnancy was diagnosed 38 to 45 d after AI by palpation per rectum of uterine contents. Nearly 11% of all cattle exhibited spontaneous estrus and received immediate AI. Herd did not influence the percentage of cows detected in estrus and inseminated. Conception rates did not differ among treatments. Conception rates differed between herds, but no interaction of herd x treatment was detected. No differences were detected between herds for days in milk, milk production, AI service number, or parity.

Probing the local structure and mechanical response of nanostructures using force modulation and nanofabrication.

Nanostructures of self-assembled monolayers (SAMs) are designed and produced using coadsorption and nanografting techniques. Because the structures of these artificially engineered domains are predesigned and well-characterized, a systematic investigation is possible to study the mechanical responses to force modulation under atomic force microscope tips. Force modulation imaging reveals characteristic contrast sensitivity to changes in molecular-level packing, molecule chain lengths, domain boundaries, and surface chemical functionalities in SAMs. By means of actively tuning the driving frequency, the resonances at the tip-surface contact are selectively activated. Therefore, specific surface features, such as the edges of the domains and nanostructures or desired chemical functionalities, can be selectively enhanced in the amplitude images. These observations provide a new and active approach in materials characterization and the study of nanotribology using atomic force microscopy.

A meta-analysis on the relationship between intake of nutrients and body weight with milk volume and milk protein yield in dairy cows.

Previously observed strong relationships between dry matter (DM) intake and milk yield in dairy cows were the basis for this meta-analysis aimed to determine the influence of intake of specific dietary nutrients on milk yield and milk protein yield in Holstein dairy cows. Diets (563) from feeding trials published in the Journal of Dairy Science were evaluated for nutrient composition using 2 diet evaluation programs. Intake of nutrients was estimated based on DM intake and program-derived diet composition. Data were analyzed with and without the effect of stage of lactation. Models based on intake of nutrients improved prediction of milk yield and milk protein yield compared with DM intake alone. Intake of net energy of lactation was the dominant variable in milk yield prediction models derived from both diet evaluation models. Milk protein yield models also improved prediction over the DM intake model. These models were dominated by ruminally undegradable protein intake and included a number of energy-related intake variables. In most models, incorporating stage of lactation improved the model fit.

A meta-analysis examining the relationship among dietary factors, dry matter intake, and milk and milk protein yield in dairy cows.

This meta-analysis was undertaken to determine the impact of dietary components on dry matter intake (DMI), milk yield (MY), and milk protein yield (MPY) in Holstein dairy cows. Diets (n=846) from 256 feeding trials published in Volumes 73 through 83 of the Journal of Dairy Science were evaluated for nutrient composition using 2 diet evaluation models: CPM Dairy (a computer program based on the principles of the Cornell Net Carbohydrate and Protein System) and NRC (2001). Data were analyzed with and without the effect of stage of lactation as a dummy variable (<100 d in milk or > or =100 d in milk). A mixed model regression analysis was used to completely investigate the potential relationships among composition variables and DMI, MY, and MPY. Protein and carbohydrate fractions were the main components within the DMI models, and DMI played a dominant role in estimating MY and MPY. Inclusion of stage of lactation substantially improved the MY models but did not affect model fits or residual structure for DMI and MPY.

Effect of simultaneous thawing of multiple 0.5-mL straws of semen and sequence of insemination on conception rate in dairy cattle.

The objectives of this study were to determine 1) the effect of simultaneous thawing of multiple 0.5-mL straws of semen and sequence of insemination (first, second, third, or fourth) on conception rates in dairy cattle, 2) whether the conception rates achieved following AI by professional AI (PAI) technicians and herdsman-inseminators (HI) differed, and 3) the effect of elapsed time from initiation of thawing straws of semen to seminal deposition on conception rates in dairy cattle. Four dairies with PAI and four with HI participated in the study. Initial data recorded included beginning thaw time, cow identification number, and time of seminal deposition. Herd records were retrieved following pregnancy diagnosis. Conception rates of dairy cows (n = 1025) were not affected by sequence of insemination (first, second, third, or fourth). Conception rates for herds using PAI were 40, 47, 41, and 50%. Conception rates for herds using HI were 24, 20, 33, and 30%. Average conception rates of dairy cows differed between PAI and HI (45 vs. 27%, respectively). The difference in mean conception rate achieved by PAI and HI was not attributable to milk production, parity, service number or stage of lactation. The elapsed time from initial thaw to completion of fourth AI was shorter for PAI than for HI, 7.6 vs. 10.9 min, respectively. Although the average conception rate differed between PAI and HI, elapsed time from initial thaw to completion of fourth AI and sequence of insemination (first, second, third, or fourth) had no effect on conception rate within inseminator group.

Receptor binding and biological activity of the dermorphin analog Tyr-D-Arg(2)-Phe-Sar (TAPS).

The binding of Tyr-D-Arg(2)-Phe-sarcosine(Sar)(4) (TAPS), a proposed mu-opioid receptor-selective tetrapeptide analog of dermorphin to opioid receptors, was studied using selective binding assays for subtypes of mu-, delta- and kappa-opioid receptors. Subtype specific mu-opioid receptor binding was further characterized in the presence of sodium and guanosine nucleotides and the activity of TAPS in isolated guinea pig ileum was compared to other mu-opioid receptor-selective ligands. Further, the antinociceptive properties of TAPS following intrathecal (i.t.) administration in rats, as a model of spinal antinociception, were evaluated. The K(i)-values for TAPS at the mu(1)- and mu(2)-opioid receptor sites were 0.4 and 1.3 nM, respectively, suggesting high affinity binding to mu-opioid receptor binding sites with an increased selectivity to mu(1)-opioid receptor sites. The attenuated reduction of TAPS binding at the mu(2)-opioid receptor subtype in the presence of the stable guanosintriphosphate analog 5'-guanylylimidodiphosphate and sodium suggests a potential partial antagonist mode of action at this site.

The effects of SB 206284A, a novel neuronal calcium-channel antagonist, in models of cerebral ischemia.

The effects of SB 206284A, 1-[7-(4-benzyloxyphenoxy)heptyl] piperidine hydrochloride, have been investigated in vitro on calcium and sodium currents in rat-cultured dorsal root ganglion (DRG) neurones and potassium-mediated calcium influx in rat synaptosomes. Cardiovascular hemodynamic effects in both anesthetized and conscious rats, and neuroprotective activity in in vivo cerebral ischemia models were also investigated. In the rat DRG cells, SB 206284A caused almost complete block of the sustained inward Ca2+ current (IC50 = 2.4 microM), suggesting that the compound is an effective blocker of slowly inactivating, high-voltage calcium current. SB 206284A reduced locomotor hyperactivity in the gerbil bilateral carotid artery occlusion model without affecting ischemia-induced damage in the hippocampal CA1 region. In the rat middle cerebral artery occlusion model, SB 206284A reduced lesion volume in the posterior forebrain, and in the rat photochemical cortical lesion model, lesion volume was reduced even when treatment was delayed until 4 hours after occlusion. At neuroprotective doses, SB 206284A had no cardiovascular effects. These findings show that SB 206284A is a novel calcium channel antagonist that shows neuroprotective properties.

SB 201823-A antagonizes calcium currents in central neurons and reduces the effects of focal ischemia in rats and mice.

BACKGROUND AND PURPOSE: Excessive calcium entry into depolarized neurons contributes significantly to cerebral tissue damage after ischemia. We evaluated the ability of a novel neuronal calcium channel blocker, SB 201823-A, to block central neuronal calcium influx in vitro and to reduce ischemic injury in two rodent models of focal stroke. METHODS: Patch-clamp electrophysiology and intracellular Ca2+ imaging in rat hippocampal and cerebellar neurons were used to determine effects on neuronal calcium channel activity. Middle cerebral artery occlusion was performed in Fisher 344 rats and CD-1 mice to determine the effects on rodent focal ischemic injury and neurological deficits. Cardiovascular monitoring in conscious rats was conducted to determine cardiovascular liabilities of the compound. RESULTS: In cultured rat hippocampal cells, calcium current measured at plateau was reduced by 36 +/- 8% and 89 +/- 4% after 5 and 20 mumol/L SB 201823-A, respectively. In cerebellar granule cells in culture, pretreatment with 2.5 mumol/L SB 201823-A totally prevented initial calcium influx and reduced later calcium influx by 50 +/- 2.5% after N-methyl-D-aspartate/glycine stimulation (P < .01). KCl depolarization-induced calcium influx also was reduced by more than 95%. In rats, a single treatment with 10 mg/kg IV SB 201823-A beginning 30 minutes after focal ischemia decreased (P < .05) hemispheric infarct by 30.4% and infarct volume by 29.3% and reduced (P < .05) forelimb deficits by 47.8% and hindlimb deficits by 36.3%. In mice, treatments with 10 mg/kg IP SB 201823-A beginning 30 minutes after focal ischemia significantly reduced infarct volume by 41.5% (P < .01). No blood pressure effects were observed with the therapeutic dose of the compound. CONCLUSIONS: These results indicate that the new neuronal calcium channel blocker SB 201823-A can block stimulated calcium influx into central neurons and can provide neuroprotection in two models of focal cerebral ischemia without affecting blood pressure. Data from several different studies now indicate that the neuronal calcium channel antagonists are a promising therapy for the postischemic treatment of stroke.