Three-year-old Angus x Gelbvieh beef cows nutritionally managed to achieve a BCS of 4 +/- 0.07 (479.3 +/- 36.3 kg of BW) or 6 +/- 0.07 (579.6 +/- 53.1 kg of BW) at parturition were used in a 2-yr experiment (n = 36/yr) to determine the effects of prepartum energy balance and postpartum lipid supplementation on cow and calf performance. Beginning 3 d postpartum, cows within each BCS were assigned randomly to be fed hay and a low-fat control supplement or supplements with either high-linoleate cracked safflower seeds or high-oleate cracked safflower seeds until d 60 of lactation. Diets were formulated to be isonitrogenous and isocaloric, and safflower seed supplements were provided to achieve 5% of DMI as fat. Ultrasonic 12th rib fat and LM area were lower (P < 0.001) for cows in BCS 4 compared with BCS 6 cows throughout the study. Cows in BCS 4 at parturition maintained (P = 0.02) condition over the course of the study, whereas cows in BCS 6 lost condition. No differences (P = 0.44 to 0.71) were detected for milk yield, milk energy, milk fat percentage, or milk lactose percentage because of BCS; however, milk protein percentage was less (P = 0.03) for BCS 4 cows. First-service conception rates did not differ (P = 0.22) because of BCS at parturition, but overall pregnancy rate was greater (P = 0.02) in BCS 6 cows. No differences (P = 0.48 to 0.83) were detected in calf birth weight or ADG because of BCS at parturition. Dietary lipid supplementation did not influence (P = 0.23 to 0.96) cow BW change, BCS change, 12th rib fat, LM area, milk yield, milk energy, milk fat percentage, milk lactose percentage, first service conception, overall pregnancy rates, or calf performance. Although cows in BCS of 4 at parturition seemed capable of maintaining BCS during lactation, the overall decrease in pregnancy rate indicates cows should be managed to achieve a BCS >4 before parturition to improve reproductive success.

Our objectives were 2-fold: to determine the effect of dietary linoleate on milk fat composition and on transcript abundance of acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS), lipoprotein lipase (LPL), and stearoyl-CoA desaturase (SCD) mRNA in mammary tissue, and to evaluate milk somatic cell mRNA as a source of mammary tissue mRNA for these enzymes. Eighteen primiparous, crossbred beef cows (BW = 411 +/- 24 kg; BCS = 5.25) were offered Foxtail millet hay at 1.68% of BW daily and either a low-fat control (n = 9) or a high-linoleate (79% 18:2n-6), cracked safflower seed supplement (n = 9). Diets were isonitrogenous and isocaloric, and the linoleate diet contained 5.4% of DMI as fat. At slaughter (37 +/- 3 d postpartum), mammary tissue was sampled and immediately frozen in liquid N2 before being stored at -80 degrees C. Milk samples were obtained from the same mammary glands and immediately centrifuged at 1,200 x g to pellet somatic cells. A ribonuclease protection assay was used to quantify the mRNA in the mammary gland and milk somatic cells. Effects of diet, tissue, or their interaction were not observed for ACC (P = 0.28, 0.89, and 0.35, respectively), FAS (P = 0.38, 0.66, and 0.20, respectively), LPL (P = 0.09, 0.15, and 0.43, respectively), or SCD (P = 0.45, 0.19, and 0.29, respectively). Dietary effects on fatty acid profile of the milk fat suggested that linoleate supplementation might have decreased de novo lipogenesis while increasing uptake of dietary fatty acids; this effect was consistent with a trend toward greater LPL mRNA for linoleate-fed cows (P = 0.09). Correlations (r values) between mammary tissue and milk somatic cell data for each mRNA for the low-fat control diet were: ACC, 0.76 (P = 0.02); FAS, 0.69 (P = 0.04); LPL, 0.68 (P = 0.04); and SCD, 0.73 (P = 0.05), and for the linoleate diet were: ACC, 0.85 (P = 0.003); FAS, 0.75 (P = 0.02); LPL, 0.90 (P = 0.001); and SCD, 0.73 (P = 0.03). We conclude that milk somatic cells obtained from lactating beef cows can be used as a source of RNA to study nutritional regulation of mammary gland lipogenesis in cows fed dietary fat supplements.

Two studies were conducted to evaluate the effects of postweaning management of British crossbred heifers on growth and reproduction. In Exp. 1, 239 spring-born, crossbred heifers were stratified by weaning BW (234 ± 1 kg) and allotted randomly to 1 of 2 treatments. Treatments were fed at a rate equivalent to 1.14 kg/d while grazing dormant forage (6.5% CP and 80% NDF, DM basis) and were 1) 36% CP containing 36% RUP (36RUP) or 2) 36% CP containing 50% RUP (50RUP). Supplementation was initiated in February (1995 and 1996) or November (1997 and 1998) and terminated at the onset of breeding season (mid May). Heifers were weighed monthly up to breeding and again at time of palpation. After timed AI, heifers were exposed to breeding bulls for 42 ± 8 d. In Exp. 2, 191 spring-born, crossbred heifers were stratified by weaning BW to treatments. Heifer development treatments were 1) pasture developed and fed 0.9 kg/day of a 36% CP supplement containing 36% RUP (36RUP), 2) pasture developed and fed 0.9 kg/day of a 36% CP supplement containing 50% RUP (50RUP), and 3) corn silage-based growing diet in a drylot (DRYLOT). Heifers receiving 36RUP and 50RUP treatments were developed on dormant forage. Treatments started in February and ended at the onset of a 45-d breeding season in May. Heifer BW and hip height were taken monthly from initiation of supplementation until breeding and at pregnancy diagnosis. In Exp. 1, BW was not different (P ≥ 0.27) for among treatments at all measurement times. However, 50RUP heifers had greater (P = 0.02; 80 and 67%) pregnancy rates than 36RUP heifers. In Exp. 2, DRYLOT heifers had greater (P < 0.01) BW at breeding than 36RUP or 50RUP developed heifers. However, BW at pregnancy diagnosis was not different (P = 0.24) for between treatments. Pregnancy rates tended to be greater (P = 0.10) for 50RUP heifers than 36RUP and DRYLOT. Net return per heifer was US$99.71 and $87.18 greater for 50RUP and 36RUP heifers, respectively, compared with DRYLOT heifers due to differences in pregnancy and development costs. Retention rate after breeding yr 3 and 4 was greatest (P ≤ 0.01) for 50RUP heifers. Thus, increasing the supply of MP by increasing the proportion of RUP in supplements fed to heifers on dormant forage before breeding increased pregnancy rates, cow herd retention, and net return compared with heifers fed in drylot.

Our objectives were to evaluate ruminal fermentation patterns, apparent ruminal biohydrogenation, and site and extent of nutrient disappearance in cattle fed supplemental cracked safflower seeds differing in 18 C fatty acid profile. Nine Angus x Gelbvieh heifers (641 +/- 9.6 kg) fitted with ruminal and duodenal cannulas were used in a triplicated 3 x 3 Latin square. Cattle were fed (OM basis) 9.1 kg of bromegrass hay and either 1) 1.8 kg of corn and 0.20 kg of soybean meal (Control); 2) 0.13 kg of soybean meal and 1.5 kg of cracked high-linoleate (67.2% 18:2) safflower seeds (Linoleate); or 3) 1.5 kg of cracked high-oleate (72.7% 18:1) safflower seeds (Oleate). Safflower seed supplements were formulated to provide similar quantities of N and TDN and 5% dietary fat. Single degree of freedom orthogonal contrasts (Control vs. Linoleate and Oleate; Linoleate vs. Oleate) were used to evaluate treatment effects. True ruminal OM and ruminal NDF disappearances (percentage of intake) were greater (P < or =0.02) for Control than Linoleate and Oleate. True ruminal N degradability (% of intake) was not different (P = 0.38) among treatments. Apparent ruminal biohydrogenation of dietary 18:2 was greatest (Linoleate vs. Oleate, P < 0.001) for Linoleate, whereas biohydrogenation of dietary 18:1 was greatest (Linoleate vs. Oleate, P = 0.02) for Oleate. Duodenal flow of 18:0 was least (P < 0.001) for Control but did not differ (P = 0.92) between Oleate and Linoleate. Total flow of unsaturated fatty acid to the duodenum was greatest (P < 0.001) in cattle fed safflower seeds, and was greater with Linoleate (P < 0.001) than with Oleate. Duodenal flow of 18:1 and 18:2 increased (P < 0.001) in Oleate and Linoleate, respectively. Duodenal flow of 18:1trans-11 was greater (P < 0.001) in cattle fed safflower seeds and in Linoleate than in Oleate. Postruminal disappearance of saturated fatty acids was greatest (P < 0.001) for Control; however, postruminal disappearance of total unsaturated fatty acids was greater (P = 0.002) for Linoleate vs. Oleate. Supplemental high-linoleate or high-oleate safflower seeds to cattle fed forage-based diets may negatively affect ruminal OM and fiber disappearance but not N disappearance. Provision of supplemental fat in the form of safflower seeds that are high in linoleic acid increased intestinal supply and postruminal disappearance of unsaturated fatty acids, indicating that the fatty acids apparently available for metabolism are affected by dietary fat source.

Enrichment of beef muscle with n-3 fatty acids (FA) is one means to introduce these FA into the diet, but ruminal biohydrogenation limits their bioavailability. To address this problem, we evaluated the ability of condensed tannin (quebracho), in the presence or absence of casein, to protect 18:3n-3 in flaxseed from hydrogenation by ruminal microbes in cattle using an in vitro fermentation approach coupled with evaluation in cattle in vivo. Treated and untreated flaxseed was incubated with bovine rumen fluid for 0 and 24 h. With tannin treated flaxseed, hydrogenation of 18:3n-3 was limited to only 13% over 24 h compared to 43% for untreated flaxseed, while addition of casein to the tannin added no additional protection. To determine if a similar level of protection would occur in vivo, we used two groups of five steers fed either a grain-based or forage-based diet. Five steers were given a grain-based diet during the trial and were fed either ground flaxseed or tannin treated flaxseed for 15 days prior to blood collection for plasma lipid fatty acid analysis. The forage fed steers followed the same regimen. Ingestion of tannin-treated flaxseed did not increase 18:3n-3 and 20:5n-3 in plasma neutral lipids as compared to non-treated flaxseed. Thus, we demonstrated that treating ground flaxseed with quebracho tannin is not useful for increasing 18:3n-3 in the neutral lipid of bovine blood plasma, and suggest caution when interpreting results from in vitro trials that test potential treatments for protecting fatty acids from hydrogenation by ruminal microbes.

Our objective was to determine duodenal and ileal flows of total and esterified fatty acids and to determine ruminal fermentation characteristics and site and extent of nutrient digestion in sheep fed an 80% concentrate diet supplemented with high-linoleate (77%) safflower oil at 0, 3, 6, and 9% of DM. Oil was infused intraruminally along with an isonitrogenous basal diet (fed at 2% of BW) that contained bromegrass hay, cracked corn, corn gluten meal, urea, and limestone. Four crossbred wethers (BW = 44.3 +/- 15.7 kg) fitted with ruminal, duodenal, and ileal cannulas were used in a 4 x 4 Latin square experiment, in which 14 d of dietary adaptation were followed by 4 d of duodenal, ileal, and ruminal sampling. Fatty acid intake increased (linear, P = 0.004 to 0.001) with increased dietary safflower oil. Digestibilities of OM, NDF, and N were not affected (P = 0.09 to 0.65) by increased dietary safflower oil. For total fatty acids (free plus esterified) and esterified fatty acids, duodenal flow of most fatty acids, including 18:2c-9,c-12, increased (P = 0.006 to 0.05) with increased dietary oil. Within each treatment, duodenal flow of total and esterified 18:2c-9,c-12 was similar (P = 0.32), indicating that duodenal flow of this fatty acid occurred because most of it remained esterified. Duodenal flow of esterified 18:1t-11 increased (P = 0.08) with increased dietary safflower oil, indicating that reesterification of ruminal fatty acids occurred. Apparent small intestinal disappearance of most fatty acids was not affected (P = 0.19 to 0.98) by increased dietary safflower oil, but increased (P = 0.05) for 18:2c-9,c-12, which ranged from 87.0 to 97.4%, and for 18:2c-9,t-11 (P = 0.03), which ranged from 37.9% with no added oil to 99.2% with supplemental oil. For esterified fatty acids, apparent small intestinal disappearance was from 80% for 18:3c-9,c-12,c-15 at the greatest level of dietary oil up to 100% for 18:1t-11 and 18:1c-12 with 0% oil. We concluded that duodenal flow of 18:2c-9,c-12 was predominately associated with the esterified fraction, suggesting that the extent of ruminal lipolysis was decreased with increased dietary high-linoleate safflower oil. Furthermore, biohydrogenation intermediates observed in the esterified fatty acids indicated that some reesterification occurred, and the high level of apparent absorption of esterified fatty acids indicated that intestinal lipolysis did not limit overall digestion of the fatty acids fed to the sheep.

To determine the effects of BCS at parturition and postpartum lipid supplementation on blood metabolite and hormone concentrations, 3-yr-old Angus x Gelbvieh beef cows, which were nutritionally managed to achieve a BCS of 4 +/- 0.07 (479.3 +/- 36.3 kg of BW) or 6 +/- 0.07 (579.6 +/- 53.1 kg of BW) at parturition, were used in a 2-yr experiment (n = 36/yr). Beginning at 3 d postpartum, cows within each BCS were assigned randomly to be fed hay and a low-fat control supplement or lipid supplements with either cracked high-linoleate or high-oleate safflower seeds until d 61 of lactation. The diets were formulated to be isonitrogenous and isocaloric, and the safflower seed supplements were formulated to achieve 5% DMI as fat. On d 31 and 61 of lactation, blood samples were collected preprandially and then hourly postprandially (at 0, 1, 2, 3, and 4 h). Serum insulin (P = 0.27) and glucose (P = 0.64) were not affected by BCS at parturition. The mean concentrations of plasma NEFA (P = 0.08) and beta-hydroxybutyrate (P = 0.08) tended to be greater, and serum IGF-I was greater (P < 0.001) in BCS 6 than BCS 4 cows. Conversely, serum GH was greater (P = 0.003) for BCS 4 cows, indicating that regulation of IGF by GH may have been uncoupled in BCS 4 cows. The postpartum diet did not affect NEFA (P = 0.94), glucose (P = 0.15), IGF-I (P = 0.33), or GH (P = 0.62) concentrations. Oleate-supplemented cows had greater (P = 0.03) serum insulin concentrations, whereas control cows had greater (P = 0.01) plasma beta-hydroxybutyrate concentrations. Concentrations of NEFA (P = 0.05) and glucose (P < 0.001) were greater, and beta-hydroxybutyrate tended (P = 0.07), to be greater at d 3, whereas serum IGF-I was greater (P = 0.003) at d 6 of lactation. Similar concentrations of NEFA, glucose, GH, and IGF-I indicate that the nutritional status of beef cows during early lactation was not influenced by lipid supplementation. However, perturbations of the somatotropic axis in BCS 4 cows indicate that the influence of energy balance and BCS of the cow at parturition on postpartum performance should be considered when making managerial decisions.

Integrated crop-livestock systems have been purported to have numerous agronomic and environmental benefits, yet information documenting their long-term impact on the soil resource is lacking. This study sought to quantify the effects of an integrated crop-livestock system on near-surface soil properties in central North Dakota, USA. Soil bulk density, electrical conductivity, soil pH, extractable N and P, potentially mineralizable N, soil organic carbon (SOC) and total nitrogen (TN) were measured 3, 6 and 9 years after treatment establishment to evaluate the effects of residue management (Grazed, Hayed and Control), the frequency of hoof traffic (High traffic, Low traffic and No traffic), season (Fall and Spring) and production system (integrated annual cropping versus perennial grass) on near-surface soil quality. Values for soil properties were incorporated into a soil quality index (SQI) using the Soil Management Assessment Framework to assess overall treatment effects on soil condition. Residue management and frequency of hoof traffic did not affect near-surface soil properties throughout the evaluation period. Aggregated SQI values did not differ between production systems 9 years after treatment establishment (integrated annual cropping = 0.91, perennial grass = 0.93; P = 0.57), implying a near-identical capacity of each system to perform critical soil functions. Results from the study suggest that with careful management, agricultural producers can convert perennial grass pastures to winter-grazed annual cropping systems without adversely affecting near-surface soil quality. However, caution should be exercised in applying results to other regions or management systems. The consistent freeze/thaw and wet/dry cycles typical of the northern Great Plains, coupled with the use of no-till management, modest fertilizer application rates and winter grazing likely played an important role in the outcome of the results.