Environmental Effects on Pregnancy Rate in Beef Cattle

Ten years of calving records were examined from Bos taurus crossbred cows (mean of 182 cows/ yr) to quantify the effects of environmental conditions during the breeding season on pregnancy rate. Estimated breeding dates were determined by subtracting 283 d from the calving date. Relationships were determined between the proportion of cows bred during the periods from the beginning of the breeding season until d 21, 42, and 60 of the breeding season and the corresponding environmental variables. Weather data were compiled from a weather station located approximately 20 km from the research site. Average daily temperature and relative humidity were used to calculate daily temperature-humidity index (THI). Daily averages for each environmental variable were averaged for each period. Minimum temperature (MNTP) and THI for the first 21 and 42 d of the breeding season were negatively associated (P \u3c 0.001) with pregnancy rate. For the 0- to 21-d, 0- to 42-d, and 0- to 60-d breeding periods, respective r2 for average temperatures were 0.32, 0.37, and 0.11, whereas r2 for MNTP were 0.45, 0.40, and 0.10 and r2 for THI were 0.38, 0.41, and 0.11, respectively, for the same breeding periods. The negative associations of temperature and THI with pregnancy rate are most pronounced during the first 21 d of the breeding season, with a −3.79 and −2.06% change in pregnancy rate for each unit of change in MNTP and THI, respectively. A combination of environmental variables increased the R2 to 0.67. In this analysis, windspeed was found to be positively associated with pregnancy rate in all equations and increased the R2 in all breeding periods. Optimum MNTP for the 0- to 21-d, 0- to 42-d, and 0- to 60- d breeding periods was 12.6, 13.5, and 14.9°C, respectively. For the 0- to 60-d breeding period, optimum THI was 68.0, whereas the THI threshold, the calculated level at which cattle will adapt, was found to be 72.9. Reductions in pregnancy rate are likely when the average MNTP and THI equal or exceed 16.7°C and 72.9, respectively, and for Bos Taurus beef cows that are pasture bred during a 60-d spring-summer period

Leiden behornte Milchkühe weniger unter leichtem bis moderatem Hitzestress als enthornte?

Es wird vermutetet, dass Hörner bei der Thermoregulation von Rindern eine Rolle spielen könnten. Deshalb wurde die Atemfrequenz, als Indikator für Hitzestress, von behornten und enthornten Europäischen Milchkühen, die gemeinsam in einer Herde im Stall gehalten wurden, erfasst. Die Gruppenzusammensetzung (N=7) war bezüglich Laktationsstand (35-354 d), Milchleistung (5,6-36,6 kg/d) und Fellfarbe balanciert. Die Atemfrequenz jedes Tieres wurde an fünf aufeinanderfolgenden Tagen durch eine Person erfasst. Der Temperature Humidity Index (THI) wurde alle 10 min. im Stall gemessen. Zur Datenanalyse wurde ein gemischtes Modell verwendet (zufälliger Faktor: Tier, fixe Faktoren: Hornstatus, THI). Der THI lag zwischen 71,9-81,5 (Mittel=75,9). Mit steigendem THI, stieg auch die Atemfrequenz an (Modellschätzwert=0,9, P=0,0341). Die Atemfrequenz lag zwischen 29,6-78,5 (Mittel=55,0). Der Hornstatus hatte keinen Einfluss auf die Atemfrequenz (P=0,5294). Im Stall hatte die Behornung keinen abschwächenden Effekt auf leichten bis moderaten Hitzestress

Influence of Ionophore Supplementation on Growth Performance, Dietary Energetics and Carcass Characteristics in Finishing Cattle during Period of Heat Stress.

Forty-eight crossbred heifers (378.1±18 kg) were used in a 56-d feeding trial (four pens per treatment in a randomised complete block design) to evaluate the influence of ionophore supplementation on growth performance, dietary energetics and carcass characteristics in finishing cattle during a period of heat stress. Heifers were fed a diet based on steam-flaked corn (2.22 Mcal NEm/kg) with and without an ionophore. Treatments were: i) control, no ionophore; ii) 30 mg/kg monensin sodium (RUM30); iii) 20 mg/kg lasalocid sodium (BOV20), and iv) 30 mg/kg lasalocid sodium (BOV30). Both dry matter intake (DMI) and climatic variables were measured daily and the temperature humidity index (THI) was estimated. The maximum THI during the study averaged 93, while the minimum was 70 (THI average = 79.2±2.3). Compared to controls, monensin supplementation did not influence average daily gain, the estimated NE value of the diet, or observed-to-expected DMI, but tended (p = 0.07) to increase (4.8%) gain to feed. Compared to controls, the group fed BOV30 increased (p≤0.03) daily gain (11.8%), gain to feed (8.3%), net energy of the diet (5%), and observed-to-expected DMI (5.2%). Daily weight gain was greater (7.6%, p = 0.05) for heifers fed BOV30 than for heifers fed MON30. Otherwise, differences between the two treatments in DMI, gain to feed, and dietary NE were not statistically significant (p>0.11). Plotting weekly intakes versus THI, observed intake of controls was greater (p<0.05) at THI values ≤77 than ionophore groups. When THI values were greater than 79, DMI of control and MON30 were not different (p = 0.42), although less than that of groups fed lasalocid (p = 0.04). Variation in energy intake was lower (p>0.05) in the ionophores group (CV = 1.7%) than in the control group (CV = 4.5%). Inclusion of ionophores in the diet resulted in relatively minor changes in carcass characteristics. It is concluded that ionophore supplementation did not exacerbate the decline of DM intake in heat-stressed cattle fed a high-energy finishing diet; on the contrary, it stabilised feed intake and favoured feed efficiency. Ionophore supplementation reduced estimated maintenance coefficients around 10% in finishing cattle during a period of heat stress. This effect was greatest for heifers supplemented with 30 mg lasalocid/kg of diet

The Invariance of R&D to the Number of Firms in the Industry

Thi spaper presents certain remarkably simple results concerning market's allocation to R&D and its comparison to socially efficient allocations. We posit that a firm can undertake more than one project aimed at the same innovation, and consider a product market characterized by Bertrand competition. Among the results we obtain is that the market R&D (that is, the number of projects undertaken, and the effort spent on different projects) is invariant to the number of firms. We also examine the effects of the number of firms on the gains from innovation to consumers, firms, and society, and show, in particular, that the market undertakes less R&D than is socially desirable.

Evaluation of a Direct Fed Microbial an an Enzymatically Hydrolyzed Yeast Product Fed Alone or in Combination to Beef Steers Administered Ractopamine Hydrochloride 28 Days Prior to Harvest During Summer Months in the Northern Plains

Study Description: Single-sourced, newly weaned steers (n=256; initial BW=542 ± 3.7lb; n=64 steers/treatment; 8 steers/pen) were blocked by location in a 2×2 factorial arrangement of DFM (Certillus CP B1801 Dry; Bacillus subtilis, Lactobacillus plantarum; 28 g/steer·d-1) and YCW (Celmanax; 18 g/steer·d-1). Temperature-humidity index (THI) was calculated as: THI=0.81×ambient temperature+[relative humidity×(ambient temperature-14.40)]+46.40. On d-1 and 2 and d-21 and 22 on RH, respiration rate (RR) and panting scores (PS) were determined before and after AM and PM feedings (0700h, 1100h, 1400h, 1700h). RR (n=3 steers/pen) was calculated from: 600/seconds required for 10 flank movements. PS utilized this scoring system: 0 (not distressed) to 4.5 (severely distressed)

Evaluation of the Interaction of Beta-Adrenergic Agonists Supplementation and Heat Stress on Growth Performance and Carcass Composition in Feeder Lambs

Forty-nine crossbred feeder lambs (wethers, n = 49; 53.3 ± 3.7 kg BW) were utilized to evaluate the interaction of b - adrenergic agonist (bAA) supplementation and heat stress on growth performance and carcass composition. Utilizing and 3 x 2 factorial design, lambs were randomly assigned to one of three bAA supplementation: 1) Control, CON, 2) Ractopamine Hydrochloride at 40 mg/hd/d, RHCL, and Zilpaterol Hydrochloride at 2.5 mg/hd/d, ZHCL for a period of 20 d and one of two environmental conditions (Thermal Neutral: TN and Heat Stress: HS). The TN environment had a constant thermal heat index (THI) of 16.6°C. Within the HS environment, a cyclic design was utilized to achieve a THI of 29.5ºC from 10:00 to 20:00 h and a THI of 24.5ºC from 22:00 to 08:00 h. Starting at 08:01 and continuing to 09:59 h, temperature and RH were gradually increased to achieve a THI of 29.5ºC at 10:00 h and reduction of temperature and RH from 20:01 to 21:59 h to achieve a THI of 24.5ºC at 22:00 h. Regardless of bAA supplementation (P = ≥ 0.09), lambs exposed to the HS environment had reduced DMI (P \u3c 0.001), ADG (P = 0.002), and final BW (P = 0.03). In addition, exposure to the HS environment (regardless of bAA supplementation; P = ≥ 0.07) decreased HCW (P \u3c 0.001), percent change in LM area (P = 0.004) and percent change in LM depth (P = 0.005). There was a bAA x environment interaction associated with RHCL supplementation and heat stress (P = 0.003). Lambs supplemented RHCL in the HS environment had reduced (P = 0.003) respiration rates, when compared to CON and ZHCL supplemented lambs. Supplementation of ZHCL decreased adipose tissue (P = 0.05) and increased percent fat free lean (P = 0.01), when compared to RHCL and CON lambs. Within the current study, both heat stress and bAA supplementation had an impact on growth performance and carcass composition. However, the data does not indicate that there was any significant interaction between bAA supplementation within a heat stress environment on growth performance or carcass composition in feeder lambs. Advisor: Ty B. Schmid

Evaluation of the Interaction of Beta-Adrenergic Agonists Supplementation and Heat Stress on Growth Performance and Carcass Composition in Feeder Lambs

Forty-nine crossbred feeder lambs (wethers, n = 49; 53.3 ± 3.7 kg BW) were utilized to evaluate the interaction of b - adrenergic agonist (bAA) supplementation and heat stress on growth performance and carcass composition. Utilizing and 3 x 2 factorial design, lambs were randomly assigned to one of three bAA supplementation: 1) Control, CON, 2) Ractopamine Hydrochloride at 40 mg/hd/d, RHCL, and Zilpaterol Hydrochloride at 2.5 mg/hd/d, ZHCL for a period of 20 d and one of two environmental conditions (Thermal Neutral: TN and Heat Stress: HS). The TN environment had a constant thermal heat index (THI) of 16.6°C. Within the HS environment, a cyclic design was utilized to achieve a THI of 29.5ºC from 10:00 to 20:00 h and a THI of 24.5ºC from 22:00 to 08:00 h. Starting at 08:01 and continuing to 09:59 h, temperature and RH were gradually increased to achieve a THI of 29.5ºC at 10:00 h and reduction of temperature and RH from 20:01 to 21:59 h to achieve a THI of 24.5ºC at 22:00 h. Regardless of bAA supplementation (P = ≥ 0.09), lambs exposed to the HS environment had reduced DMI (P \u3c 0.001), ADG (P = 0.002), and final BW (P = 0.03). In addition, exposure to the HS environment (regardless of bAA supplementation; P = ≥ 0.07) decreased HCW (P \u3c 0.001), percent change in LM area (P = 0.004) and percent change in LM depth (P = 0.005). There was a bAA x environment interaction associated with RHCL supplementation and heat stress (P = 0.003). Lambs supplemented RHCL in the HS environment had reduced (P = 0.003) respiration rates, when compared to CON and ZHCL supplemented lambs. Supplementation of ZHCL decreased adipose tissue (P = 0.05) and increased percent fat free lean (P = 0.01), when compared to RHCL and CON lambs. Within the current study, both heat stress and bAA supplementation had an impact on growth performance and carcass composition. However, the data does not indicate that there was any significant interaction between bAA supplementation within a heat stress environment on growth performance or carcass composition in feeder lambs. Advisor: Ty B. Schmid

Environmental factors affecting daily water intake on cattle finished in feedlots

Records from 7 studies conducted during 1999 to 2005 were utilized to assess the effects of environmental factors on daily water intake (DWI) of finishing cattle. Data from unshaded feedlot pens (up to 24 pens utilized per study; 6 to 9 animals·pen−1) containing predominantly Angus crossbred cattle were obtained by dividing total water intake by the number of animals utilizing that waterer. Each waterer was shared by 2 pens; therefore, data were derived from a database containing 72 experimental units comprising 144 pen records. Climatic data were compiled from weather stations located at the feedlot facility. The database included daily measures of mean ambient (Ta), maximum (Tmax), and minimum (Tmin) temperature (°C), precipitation, relative humidity (%), wind speed (m∙s−1), solar radiation (SR, W∙m−2), and temperaturehumidity index (THI), as well as DMI (kg∙d−1) and DWI (L∙d−1). Simple and multiple regression analyses were conducted by season and for the overall data set. Results confirmed that DWI increases during the summer (P < 0.01). When seasons were combined and analyzed by linear regression, the best predictors of DWI were THI (r2 = 0.57), Ta (r2 = 0.57), Tmin (r2 = 0.56), and Tmax (r2 = 0.54). In multiple regression analyses, smaller coefficients of determination (R2 < 0.25) were found within summer and winter seasons. Across season, the largest R2 (0.65) were obtained from the following prediction equations: 1) DWI = 5.92 + (1.03∙DMI) + (0.04∙SR) + (0.45∙Tmin); and 2) DWI = −7.31 + (1.00∙DMI) + (0.04∙SR) + (0.30∙THI). In conclusion, Ta, Tmin, and THI were found to be the primary factors that influence DWI in finishing cattle, whereas SR and DMI were found to have a smaller influence on DWI

Comparison of ambient temperature, relative humidity, and temperature-humidity index between on-farm measurements and official meteorological data

The objectives of the study were to compare the climate conditions of 7 dairy farms with the climate recorded at the closest official meteorological station. Specifically, we set out to compare the ambient temperature, relative humidity, and the resulting temperature-humidity index (THI) from 7 different barns with those data obtained from the closest official meteorological stations and to compare the climate conditions between 4 different locations within 1 barn. Measures of correlation and agreement demonstrated that climate conditions differ significantly between the barn and the corresponding official meteorological stations as well as between 4 different locations inside 1 barn. The ambient temperature was higher (6.4 ± 3.6°C) in the barn than at the official meteorological station. The relative humidity was higher at the official meteorological station (0.2 ± 7.2%) than in the barn. The THI was higher (11.1 ± 6.5) in the barn than at the official meteorological station. Days with an average THI ≥ 72 were 64 and 4 out of 756 experimental d in the barn and at the official meteorological station, respectively. Also, in a comparison of 7 different barns, ambient temperature and THI were significantly higher than at the closest corresponding official meteorological station. These results indicate that climate conditions should be obtained from on-farm measurements to evaluate potential heat stress and to develop effective measures to abate heat stress of dairy cows