The objective of this study was to evaluate the use of blood lactate concentration as an objective measure of beef cattle temperament and determine if the temperament of steers affected growth rate and tenderness of beef steaks. Angus×Simmental steers (n=154) were evaluated for blood lactate (BL), exit velocity (EV) and chute score (CS), and humanely harvested. Carcass characteristics were assessed and loin samples were obtained for tenderness evaluation. All measures of the temperament were significantly correlated to each other (r=0.14-0.47; P≤0.04). Steaks from steers in the medium BL classification were significantly more tender than steaks from steers from the high BL classification. The steers with faster EV tended to result in steaks with higher shear force values (P=0.07). The steers classified as fast growing resulted in steaks with lower shear force values (P=0.02) compared to steaks from steers classified as slow growing. Results suggest that the temperament contributes to variations in growth rate, blood lactate, and tenderness.

The objective of this study was to evaluate the effect of growth implants on the carcass characteristics and tenderness of steers and heifers with different genetic potentials for growth, lean meat yield production, and marbling. Two experiments were conducted. Experiment 1 evaluated Angus steers sired by bulls with high EPD for retail product yield or marbling. Implant treatment was imposed randomly within sire groups. Loins (Institutional Meat Purchasing Specifications 180) were collected from each carcass and cut into three 2.54-cm steaks aged for 7, 14 and 21 d to evaluate tenderness. The second experiment evaluated steers and heifers of British and Continental breed descent. Steers and heifers were slaughtered after 120 d on feed. Loin sections were collected, and one 2.54-cm steak aged 7 d was used for tenderness analysis. When implants were used in Angus steers, HCW and LM area increased, whereas internal fat and marbling decreased (P < 0.01). In Angus steers, sire type did not affect shear force values of steaks; however, implant use significantly increased shear force values (P < 0.01). Carcasses from cattle of Continental breed descent were significantly heavier than carcasses of British breed descent with larger LM area, slightly less fat, and a reduced yield grade (P < 0.01). Also, steer carcasses were heavier than heifer carcasses with larger LM (P < 0.05), but no effect of sex on fat depth, internal fat, yield grade or marbling was observed. No significant interactions were seen between growth implant and breed or between growth implant and sex for shear force values. Shear force values were significantly less for steaks from steers and heifers of British decent compared with steers and heifers of Continental descent (P < 0.01). Steaks from implanted steers and heifers had significantly (P < 0.01) greater shear force values than steaks from steers and heifers not implanted. Use of growth implants in growing cattle resulted in significantly heavier carcass weights, larger LM area, and reduced internal fat. However, implant use also reduced the amount of marbling along with contributing to reduced tenderness. Complicating the tenderness issue is the increased shear force values reported for heifers as well as steers of Continental breed descent. Use of implants may contribute to tenderness variability because of different animal responses to implants.

Reproduction is the most important factor to profitability of the cow herd when compared with other economically important traits, such as growth and carcass characteristics. By increasing the proportion of heifers calving at two yr of age, producers can increase the revenue and selection intensity of their herds. Therefore, the primary objective of this project was to estimate breed effects and heterosis values for heifer pregnancy. Reproductive records collected on 651 purebred and crossbred commercial beef females, comprised of Hereford, Simmental, and Tarentaise, from Montana State University's Northern Agricultural Research Center in Havre, Montana were analyzed as a binary trait. Females were born from 1976 to 1995. Data included calving records on two- and three-yr-old cows. Heifer Pregnancy was defined as a success if her first calving record was at two yr of age, but a failure if her first calving record was at three yr of age. Heifer pregnancy was able to be defined this way because young cows in this herd were not culled unless they were open for two consecutive years. Comparison of direct genetic effects showed that Simmental females were the most likely and Hereford females were the least likely to calve at two yr of age with Tarentaise being intermediate to the other two breeds. Comparison of maternal genetic effects showed that females out of Tarentaise dams were the most likely and females out of Hereford dams were the least likely to calve at two yr of age with no estimation on females out of Simmental dams. Comparison of paternal genetic effects showed that females out of Tarentaise sires were most likely and females out of Simmental sires were least likely with females out of Hereford sires being intermediate. Heterosis was estimated to be -2.79%, -0.52%, and 9.56% for direct, maternal and paternal heterosis, respectively, which is a favorable response that indicates that crossbreeding will increase the proportion of females calving at two yr of age. age.

ABSTRACT:,Sixty-eight Rambouillet ram lambs (average weight of 32 kg ± 5.94 kg and average age of 156 d ± 5 d) were used in a 2 x 2 factorial arrangement,of treatments to determine the effect of energy source and level of Vitamin E on feedlot performance. Rams were weighed,after an 18 h shrink and randomly assigned to one of 12 feedlot pens. Each pen was randomly assigned to 1 of 4 diet treatment combinations in a completely randomized design. Pen was the experimental unit with either 5 or6 lambs in each pen. Energy treatments were either a 6% oil ration using whole safflower seeds (SS) or a starch based isocaloric and isonitrogenous control (SC) combined with either 400 IU (VE) or 0 IU (VC) of supplemental Vitamin E. All rams started on a 70% roughage, 30% energy concentrate diet. Rams had ad libitum access to water. Salt and mineral were included in both the VE and VC supplements. Diets were pelleted, hand mixed, and placed in self feeders allowing rams ad libitum access to their respective diets. Over an 18 d period, the amount,of concentrate in the diets was increased until a finishing diet with 1.79 NEm and 1.16 NEg was achieved. Rams received the finishing diet for 61 d. Rams were weighed,at the beginning and end of the trial, as well as when transitioning from the step-up

Rebreeding a first calf heifer to produce her second calf at 3 yr of age can be challenging for beef producers. Heifers generally require more recovery time following their first calf which may delay the onset of estrus to a point beyond the normal breeding season. In an effort to improve heifer rebreeding, data on beef cows at 2 and 3 yr of age were analyzed to determine if rebreeding of first calf heifers is under any degree of genetic control. Records on 399 females born from 1976 - 2001 were analyzed to determine genetic parameters for probability of rebreeding. Animals included in the analysis were the Line 4 Herefords which are maintained at Montana State University's Northern Agricultural Research Center in Havre, Montana. Young cows in this herd were only culled if they were open, so any cow calving at 2 yr of age, but not at 3 yr of age was considered to fail at rebreeding. Overall, 69.9% of females were successful in breeding back to produce a calf at 3 yr of age. To estimate the genetic parameters associated with this trait, data were analyzed using MTDFREML with year of birth as a categorical fixed effect and percentage of individual inbreeding fit as a linear and quadratic covariate. On the observed scale, heritability was estimated to be 0.14 (0.12). Converting the observed trait to the underlying scale produced a heritability estimate for rebreeding of 0.24. Probability of rebreeding to produce a second calf at three yr of age has a genetic component and selection against females who fail to rebreed should result in a positive genetic response.

Twin-bearing Targhee ewes (Exp. 1, 1 yr, n = 42) and 1,182 single- and twin-bearing whiteface range ewes (Exp. 2, n = 8 experimental units over 2 yr) were used in a 2 x 2 factorial arrangement of treatments to determine the effect of supplemental energy source and level of vitamin E supplement on lamb serum metabolites and thermogenesis (Exp. 1) and on lamb growth (Exp. 2). During late gestation, ewes were individually fed (Exp. 1) or group-fed (Exp. 2) a daily supplement. Supplements were 226 g/ewe of daily safflower seed (DM basis; SS) with either 350 IU/ewe daily (VE) or no added supplemental (VC) vitamin E; or 340 g/ewe daily of a barley-based grain supplement (DM basis; GC) and either VE or VC. One hour postpartum in Exp. 1, twin-born lambs were placed in a 0 degrees C dry cold chamber for 30 min. Lamb rectal temperature was recorded every 60 s and blood samples were taken immediately before and after cold exposure. In Exp. 2, lambs were weighed at birth, at turnout from confinement to spring range (32 d of age +/- 7; turnout), and at weaning (120 d of age +/- 7). Ewes were weighed at turnout and weaning. In Exp. 1, a level of vitamin E x energy source interaction was detected (P < 0.10) for body temperature and change in NEFA and glucose concentrations. Lambs from SSVC ewes had the lowest (P = 0.01) body temperature and had decreased (P = 0.08) NEFA concentration. The SS lambs tended to have decreased (P < 0.11) concentrations of blood urea N (BUN) and thyroxine at 0 min than did lambs born to GC ewes. After 30 min of cold exposure, SS lambs had increased and GC lambs had decreased BUN, triiodothyronine, and triiodothyronine:thyroxine concentrations (P < 0.10). In Exp. 2, kilograms of lamb per ewe at turnout and weaning and lamb survival at weaning were greater (P < 0.07) for GC than SS lambs. Based on the decreased body temperature in SSVC lambs at birth, the greater change in BUN during the cold exposure for SS than GC lambs, and the decreased survival rate for SS than GC lambs, SSVC-supplemented ewes appeared to give birth to lambs with an apparently decreased energetic capacity. This may compromise the ability of the newborn lamb to adapt to extreme environmental conditions.

A study was conducted on foothill rangeland to determine if breed of sire affected grazing distribution patterns and to evaluate relationships between individual grazing patterns and performance of beef cows. Angus (AN), Charolais (CH), Piedmontese (PI), and Salers (SA) sires were mated to dams with Hereford and Tarentaise breeding to produce cows observed during the summers of 1998–2001. Locations of individual cows were recorded two to three times per week during 1.5–2.5-h periods in the morning by observers on horseback. Terrain use was analyzed using a mixed statistical model that included breed of sire, dam terrain use category as fixed effects and cow as a random effect. Piedmontese-sired cows were observed farther (P<0.05) horizontally from water and showed a tendency toward higher (P=0.09) pasture ratios (PR) of terrain use than AN-sired cows. Cows from dams that used steeper slopes and areas farther from water grazed farther (P<0.05) vertically from water, tended to be observed farther (P=0.09) horizontally from water, and had a PR greater (P<0.05) than cows from dams that used gentle terrain near water. Relationships between terrain use and animal performance were evaluated each year using residual correlations from a model that included sire breed, dam breed, cow age, and pasture. In 1998 and 2001, cows that were heavier (P<0.05) and in 1998 taller (P<0.05) traveled farther horizontally from water than did lighter cows. Relationships between cow weight or hip height and horizontal distance to water were not observed during other years. No other relationships between terrain use and cow performance were found (P>0.05). Terrain use was not correlated (P>0.05) to calving date, actual weaning weight, or age-adjusted weaning weight. Pregnant cows used steeper (P<0.05) slopes in 2001, but no differences were detected in the other 3 years (P>0.05). Cows sired by bulls from breeds developed in mountainous terrain appeared to use rugged extensive pastures more uniformly than cows sired by bulls from breeds developed in gentler terrain. As observed in an earlier study, terrain use of cows grazing foothill rangeland was not consistently related to their weight, hip height, body condition, reproductive performance, or calf weight.

Data of 9051 weights measured on 642 cows in the Line 4 inbred Hereford herd at the Northern Agricultural Research Center in Havre, Montana from 1976 to 1997 were analyzed. Age of cow ranged from 18 mo to 15 yr. Previous reports described the 1995 calf crop from this line to have an average inbreeding coefficient of 20.7%. After pedigree reconstruction, the average inbreeding coefficient of the 1995 calf crop was determined to be 33.8% and increasing at a rate of 0.3% per year from 1976 to 1995. A maximum of six weigh dates per year were analyzed as part of this study in a univariate repeatability model. Estimates of genetic parameters were not significantly different from the previously reported estimates that included reduced estimates of inbreeding. Estimates of genetic parameters (and associated s.e.) from this analysis were 0.69 (0.13), -0.63 (0.19), 0.09 (0.05), and 0.13 (0.08) for direct heritability, direct-maternal genetic correlation, maternal heritability, and proportion of variance due to direct permanent environmental effects, respectively. Genetic trends for direct breeding values were small, but three times greater (in absolute value) than had been previously reported with an estimate of -0.19 kg/yr. Average direct breeding values (DBV) by year of birth were generally smaller with the correct estimates of inbreeding, with differences from the previous estimates ranging from -2.4 to +0.4 kg. Average maternal breeding values (MBV) by year of birth were larger, with differences from the previous estimates ranging from 0.7 to 1.3 kg compared to the previous estimates. Spearman rank correlations comparing the new and old estimates were 0.98 and 0.98 for DBV and MBV, respectively. Incorrect estimates of inbreeding have little effect on genetic trends and relative ranking, but do alter the actual breeding values reported for animals.

Records for 1971 calves produced in the Line 4 Hereford herd at the Northern Agricultural Research Center (NARC) in Havre, Montana from 1976 to 2004 were analyzed to determine the current status of this closed herd. From 1976 to 1995, selection in this line was performed using an index of adjusted yearling weight minus 3.2 times adjusted birth weight. Since 1995, selection has been based on single trait selection for scrotal circumference. Records available across the majority of years included birth weight, weaning weight, weaning wither height, and weaning condition score. The average inbreeding coefficient for calves born in 2004 was 36.4%. Genetic parameters for all traits were analyzed using a univariate model. Estimates of direct heritability (and associated s.e.) were 0.51 (0.09), 0.21 (0.07), 0.28 (0.11), and 0.24 (0.09) for birth weight, weaning weight, weaning wither height, and weaning condition score, respectively. Estimates of maternal heritability were 0.08 (0.04), 0.09 (0.06), 0.13 (0.07), and 0.09 (0.07), respectively. The estimate of the direct-maternal genetic correlation was non-significant for most traits with estimates of 0.15 (0.26), -0.12 (0.35), -0.52 (0.22), and -0.48 (0.29), respectively. The proportion of variance due to maternal permanent environmental effects was only significant for weaning weight and weaning condition score with estimates of 0.30 (0.05) and 0.14 (0.04), respectively. Birth weight direct breeding value (DBV), maternal breeding value (MBV), and phenotypic trends were estimated to be -0.005, -0.004, and -0.034 kg/yr, respectively. Weaning weight trends were estimated to be +0.289, +0.082, and +0.276 kg/yr, respectively. Weaning wither height trends were +0.025, +0.010, and -0.130 cm/yr, respectively. Weaning condition score trends were +0.0061, - 0.0002, and +0.0040 score/yr. Trends for these traits are relatively flat for the period of time studied.

A group of mature Angus cows from the Bair Ranch near Martinsdale, MT were artificially inseminated from 1999 through 2001 to Angus bulls with either high EPD for marbling (MB) or high EPD for retail product (RP). Heifer calves from these matings were retained as replacements in the herd. These females were artificially inseminated to a single sire that was also used as the clean-up sire. This study was initiated to evaluate the impact of different selection criteria on reproduction within a herd of western range cattle. Total pregnancy (AI and natural service) of heifers as yearlings (BRED), re- breeding pregnancy rate of 2-yr-old dams (REBRED), pre-breeding body weight (COWWT), and weaning weight of first calves (WWT) was analyzed. Reproductive traits were analyzed by categorical modeling with the model including year and sire type. Cow and calf weights were analyzed by general linear modeling. The model for COWWT included year and type (MB or RP), and WWT included calf age as a covariate, year, sex, and dam type. No differences in COWWT due to type were found (P=0.2). Year was significant (P<0.001) with those heifers born in 2001 being heavier than the other years. Significant calf age effects were found for WWT (P<0.01), but type and sex were not significant sources of variation (P>0.3). Each day of age of calves increased WWT by 0.75 kg. Statistical analysis showed calves weaned by dams born in 2001 were not as heavy as calves weaned in other years, though overall year affect was not significant. Year was a significant source of variation for BRED and REBRED (P<0.05), but type was not. Probabilities for non-pregnant heifers were high in 2001 (32%) compared with other years (15%). Conception to AI was at approximately 35% in 2001 heifers compared with 50% in other years. However, this trend was reversed in REBRED with 2001 born heifers averaging 5% non- pregnant compared with 20% for the other years.

Weights were measured on 642 cows in the Line 4 inbred Hereford herd at the Northern Agricultural Research Center in Havre, Montana from 1976 to 1997. The Line 4 Hereford herd descended from Miles City Line 1. The herd had been selected based on an index of adjusted yearling weight minus 3.2 times adjusted birth weight from 1976 to 1995 and had reached an average inbreeding of 20.7% at the conclusion of this selection experiment. Over the course of the study, there was a maximum of seven weigh dates per year. Weights were measured prior to calving, after calving, at two different milk test dates, prior to breeding, after breeding, and at calf weaning. Cows averaged 14.5 cow weight records during their lifetime and 3.8 records per year. Maternal genetic effects were determined to be statistically significant for mature cow weight and were included in the model with direct genetic effects, direct-maternal genetic covariance, and the proportion of variance due to direct permanent environmental effects. Weights were analyzed individually as repeated records within seasons across years as well as combined in a single univariate analysis combining all seasons. Estimates of genetic parameters (and associated s.e.) from the single analysis including all seasons were 0.64 (0.13), -0.64 (0.20), 0.07 (0.05), and 0.15 (0.08) for direct heritability, direct-maternal genetic correlation, maternal heritability, and proportion of variance due to direct permanent environmental effects, respectively. Over the course of the experiment, genetic trends were small and estimated to be 0.38 kg/yr and -0.15 kg/yr for direct and maternal breeding values, respectively. Selection for increased yearling weight and decreased birth weight in this index does not appear to have an effect on mature cow weight.