Five experiments evaluated the effects of rumen-protected PUFA supplementation on reproductive function of Bos indicus beef cows. In Exp. 1, 910 lactating primiparous Nelore cows were randomly assigned to receive 0.4 kg/d of a protein-mineral mix in addition to 0.1 kg/d of a rumen-inert PUFA source (PF) or 0.1 kg/d of kaolin (rumen-inert indigestible substance; control), from the beginning of estrus synchronization protocol (d -11) until 28 d after fixed-time AI (TAI; d 28). Cows supplemented with PF had greater (P = 0.04) pregnancy rates compared with control cows (51.2 vs. 39.6%). In Exp. 2, 818 lactating primiparous Nelore cows were assigned to the same TAI schedule from Exp. 1 and randomly allocated to receive 1) control from d -11 to 28, 2) PF from d -11 to 16 and control from d 17 to 28, or 3) PF from d -11 to 28. Cows receiving PF until d 28 had greater (P = 0.02) pregnancy rates compared with control cows and tended to have greater (P = 0.10) pregnancy rates compared with cows receiving PF until d 16 (42.9, 31.3, and 35.8%, respectively). In Exp. 3, 435 nulliparous and multiparous lactating B. indicus-crossbred cows were randomly assigned to receive control or PF from the end of synchronization protocol (d 0) until 21 d after fixed-time embryo transfer (d 28). Cows supplemented with PF had greater (P = 0.07) pregnancy rates compared with control cows (49.6 vs. 37.7%). In Exp. 4, 504 lactating multiparous Nelore cows were randomly assigned to receive PF or a similar supplement containing a rumen-protected SFA source (SF) for 28 d beginning after TAI. Cows supplemented with PF had greater (P = 0.02) pregnancy rates compared with SF cows (47.9 vs. 35.5%). In Exp. 5, 9 nonlactating, nonpregnant, ovariectomized Gir x Holstein cows inserted with an intravaginal progesterone (P4)-releasing device were stratified by BW and BCS and divided into 3 squares. Squares were randomly assigned to receive control, PF, or a protein-mineral mix containing 0.2 kg/d of rumen-inert PUFA source (PF2), in a Latin square 3 x 3 design containing 3 periods of 14 d each. Cows supplemented with PF had greater (P = 0.03) mean serum P4 concentrations compared with control and PF2 cows (1.81, 1.66, and 1.68 ng/mL, respectively). These results indicate that supplementing 0.1 kg/d of rumen-inert PUFA to beef cows, particularly after breeding, may be a method of enhancing their reproductive performance, perhaps by increasing circulating P4 concentrations.

Eighty-four multiparous, nonlactating, pregnant Angus × Hereford cows were ranked by pregnancy type (56 AI and 28 natural service), BW, and BCS and allocated to 21 drylot pens at the end of their second trimester of gestation (d 0). Pens were assigned to receive forage-based diets containing 1) sulfate sources of Cu, Co, Mn, and Zn (INR); 2) an organic complexed source of Cu, Mn, Co, and Zn (AAC; Availa 4; Zinpro Corporation, Eden Prairie, MN); or 3) no supplemental Cu, Co, Mn, and Zn (CON). Diets were offered from d 0 until calving and formulated to meet requirements for energy, protein, macrominerals, Se, I, and vitamins. The INR and AAC diets provided the same daily amount of Cu, Co, Mn, and Zn. Cow BW and BCS were recorded and liver samples were collected on d -10 and 2 wk (d 75) before the calving season. Within 3 h after calving, calf BW was recorded, liver samples were collected, and the expelled placenta was retrieved ( = 47 placentas). Calves were weaned on d 283 of the experiment, preconditioned for 45 d (d 283 to 328), transferred to a growing lot on d 328, and moved to a finishing lot on d 440 where they remained until slaughter. Liver Co, Cu, and Zn concentrations on d 75 were greater ( ≤ 0.05) for INR and AAC cows compared with CON cows, whereas INR cows had reduced ( = 0.04) liver Co but greater ( = 0.03) liver Cu compared with AAC cows. In placental cotyledons, Co concentrations were greater ( ≤ 0.05) in AAC and INR cows compared with CON cows, whereas Cu concentrations were increased ( = 0.05) only in AAC cows compared with CON cows. Calves from INR and AAC cows had greater ( < 0.01) liver Co concentrations at birth compared with calves from CON cows. Liver Cu and Zn concentrations at birth were greater ( ≤ 0.05) in calves from AAC cows compared with cohorts from CON cows. Weaning BW was greater ( ≤ 0.05) in calves from AAC cows compared with cohorts from CON cows, and this difference was maintained until slaughter. In the growing lot, calves from AAC cows had reduced ( < 0.01) incidence of bovine respiratory disease compared with CON and INR cohorts. Collectively, these results suggest that feeding the AAC diet to late-gestating beef cows stimulated programming effects on postnatal offspring growth and health compared with the CON diet. Therefore, supplementing late-gestating beef cows with an organic complexed source of Co, Cu, Zn, and Mn instead of no supplementation appears to optimize offspring productivity in beef production systems.

Two experiments evaluated the effects of temperament and acclimation to handling on reproductive performance of Bos taurus beef females. In Exp. 1, 433 multiparous, lactating Angus × Hereford cows were sampled for blood and evaluated for temperament before the breeding season. Cow temperament was assessed by chute score and exit velocity. Chute score was assessed on a 5-point scale according to behavioral responses during chute restraining. Exit score was calculated by dividing exit velocity into quintiles and assigning cows with a score from 1 to 5 (1 = slowest, 5 = fastest cows). Temperament score was calculated by averaging chute and exit scores. Cows were classified for temperament type according to temperament score (≤ 3 = adequate, > 3 = aggressive). Plasma cortisol concentrations were greater (P < 0.01) in cows with aggressive vs. adequate temperament. Cows with aggressive temperament had reduced (P ≤ 0.05) pregnancy and calving rate and tended to have reduced (P = 0.09) weaning rate compared with cows with adequate temperament. Hence, kilogram of calf born per cow was reduced (P = 0.05) and kilogram of calf weaned per cow tended to be reduced (P = 0.08) in aggressive cows. In Exp. 2, 88 Angus × Hereford heifers (initial age = 206 ± 2 d) were weighed (d 0 and 10) and evaluated for temperament score (d 10). On d 11, heifers were ranked by these variables and assigned to receive or not (control) an acclimation treatment. Acclimated heifers were processed through a handling facility 3 times weekly for 4 wk (d 11 to 39; Mondays, Wednesdays, and Fridays), whereas control heifers remained undisturbed on pasture. Heifer puberty status, evaluated via plasma progesterone concentrations, was assessed on d 0 and 10, d 40 and 50, 70 and 80, 100 and 110, 130 and 140, 160 and 170, and 190 and 200. Blood samples collected on d 10 and 40 were also analyzed for plasma concentrations of cortisol and haptoglobin. Temperament score was assessed again on d 40 and d 200. Acclimated heifers had reduced (P = 0.01) concentrations of cortisol and haptoglobin on d 40 and reduced (P = 0.02) exit velocity on d 200 compared with control heifers. Puberty was hastened in acclimated heifers compared with control (P = 0.01). Results from this study indicate that B. taurus beef cows with aggressive temperament have impaired reproductive performance compared with cohorts with adequate temperament, whereas acclimation to human handling after weaning hastens reproductive development of replacement heifers.

This study evaluated the effects of narasin on intake and rumen fermentation characteristics of Bos indicus steers offered a high-forage diet for 140 d. On day 0 of the study, 30 rumen-fistulated Nellore steers [initial body weight (BW) = 281 ± 21 kg] were assigned to 30 individual pens in a randomized complete block design according to their initial BW. Animals were randomly assigned to 1 of the 3 treatments: 1) forage-based diet without narasin (CONT; n = 10), 2) CONT diet plus 13 ppm of narasin (13NAR; n = 10), and 3) CONT diet plus 20 ppm of narasin (20NAR; n = 10). The forage used was Tifton-85 (Cynodon dactylon spp.), whereas the carrier for narasin was a 50:50 mixture of soybean hull:corn. The experimental period was divided into 5 periods of 28 d each. Throughout the experimental period, total dry matter intake (DMI) was recorded daily, whereas mineral salt intake was recorded weekly. Blood and ruminal fluid samples were collected on day 0 (prior to treatment feeding), 28, 56, 84, 112, and 140 of the study. Moreover, total tract apparent nutrient digestibility was performed for a 5-d period every 28 d. No treatment effects were observed on forage, mineral, concentrate, or total DMI (P ≥ 0.22). Nonetheless, 13NAR tended to have a greater mineral intake vs. 20NAR cohorts (P = 0.08) Narasin-supplemented animals had reduced rumen acetate, Ac:Pr ratio, as well as greater (P ≤ 0.02) rumen propionate concentrations vs. CONT cohorts. Moreover, 13NAR increased rumen propionate and decreased butyrate, Ac:Pr vs. 20NAR cohorts (P ≤ 0.01). Throughout the experimental period, narasin-supplemented animals had reduced ammonia concentrations vs. CONT cohorts (P &lt; 0.01), whereas no differences were observed between 13NAR and 20NAR (P = 0.80). No treatment or dose effects were observed (P ≥ 0.23) on DM, organic matter (OM), protein, neutral detergent fiber (NDF), acid detergent fiber (ADF), and mineral digestibility. Animals fed 13NAR had a reduced mean plasma urea concentration vs. CONT cohorts (P = 0.03), whereas no further differences were observed (P ≥ 0.12). In summary, narasin supplementation to beef steers offered a high-forage diet did not impact forage, mineral, and total DMI, as well as nutrient digestibility, whereas rumen fermentation characteristics, rumen ammonia, and plasma urea concentrations were positively impacted and lasted throughout the experimental period. Additionally, 13 ppm of narasin resulted in a reduced Ac:Pr ratio and rumen ammonia when compared to animals supplemented with 20 ppm.

The objective of this experiment was to compare fatty acid (FA) concentrations in plasma and reproductive tissues as well as hormones and expression of genes associated with pregnancy establishment in beef cows supplemented or not with Ca salts of soybean oil (CSSO) beginning after timed AI. Ninety nonlactating multiparous Nelore (Bos indicus) cows were timed inseminated on d 0 of the experiment and divided into 18 groups of 5 cows/group. Groups were randomly assigned to receive (as-fed basis) 100 g of a protein-mineral mix plus 100 g of ground corn per cow daily in addition to 1) 100 g/cow daily of CSSO (n = 9) or 2) 100 g/cow daily of kaolin (CON; rumen-inert indigestible substance; n = 9). All groups were maintained in a single Brachiaria brizanta pasture (24 ha) with ad libitum access to forage and water. However, groups were segregated daily and offered treatments individually at the working facility during the experimental period (d 0 to 18). Blood samples were collected and transrectal ultrasonography was performed to verify ovulation and estimate corpus luteum (CL) volume immediately before AI (d 0) and on d 7 and 18 of the experiment. On d 19, 36 cows (18 cows/treatment; 2 cows/group) diagnosed without the presence of a CL on d 0 but with a CL greater than 0.38 cm(3) in volume on d 7 and 18 were slaughtered for collection of conceptus, uterine luminal flushing, and tissue samples from the CL and endometrium. Cows receiving CSSO had greater concentrations of linoleic and other ω-6 FA in plasma (P < 0.01), endometrium (P ≤ 0.05), CL (P ≤ 0.05), and conceptus (P ≤ 0.08) compared to CON. On d 7 of the experiment, CSSO-supplemented cows had greater plasma progesterone concentrations (P < 0.01) and CL volume (P = 0.02) compared to CON, whereas no treatment effects were detected (P ≥ 0.15) for these parameters on d 18 (treatment × day interaction; P < 0.01). Cows receiving CSSO tended (P = 0.09) to have greater concentrations of interferon-tau in the uterine flushing media compared with CON. However, no treatment effects were detected for mRNA expression genes associated with pregnancy establishment in endometrial, CL, and conceptus samples (P ≥ 0.12). In summary, supplementing beef cows with 100 g of CSSO beginning after AI favored incorporation of ω-6 FA into their circulation, reproductive tissues, and conceptus, without impacting expression of genes associated with pregnancy establishment on d 19 of gestation.

No abstract

Angus×Hereford steers (n = 42) and heifers (n = 21) were ranked by gender and BW on d 0 of the experiment and randomly assigned to 1 of 3 treatments: 1) no transport and full access to feed and water (CON); 2) continuous road transport for 1,290 km (TRANS), or 3) road transport for 1,290 km, with rest stops every 430 km (STOP; total of 2 rest stops). Treatments were applied from d 0 to 1 of the experiment. Cattle from TRANS and STOP treatments were transported in separate commercial livestock trailers, within a single 2.1×7.2 m compartment, but through the exact same route. During each rest stop, STOP cattle were unloaded and offered mixed alfalfa-grass hay and water for ad libitum consumption for 2 h. Upon arrival of STOP and TRANS on d 1, cattle were ranked by sex and BW within each treatment and assigned to 21 feedlot pens (7 pens/treatment; 2 steers and 1 heifer/pen). Full BW was recorded before (d -1 and 0) treatment application and at the end of experiment (d 28 and 29). Total DMI was evaluated daily from d 1 to 28. Blood samples were collected on d 0 (before loading of TRANS and STOP cattle), 1 (immediately after unloading of TRANS and STOP cattle), 4, 7, 10, 14, 21, and 28. Body weight shrink from d 0 to d 1 was reduced (P<0.01) in CON compared to TRANS and STOP, and reduced in STOP compared to TRANS. Mean ADG was greater (P<0.05) in CON compared to TRANS and STOP, but similar (P=0.68) between TRANS and STOP. No treatment effects were detected (P≥0.18) on hay, concentrate, and total DMI. Mean G:F was greater (P=0.05) in CON compared to STOP, tended to be greater (P=0.08) in CON compared to TRANS, and similar (P=0.85) between TRANS and STOP. Plasma cortisol concentrations were greater (P≤0.04) in TRANS compared to CON and STOP on d 1, and greater (P=0.04) in TRANS compared to CON on d 4. Serum NEFA concentrations were greater (P<0.01) in TRANS compared to CON and STOP on d 1, and greater (P≤0.05) in TRANS compared to CON on d 4 and 7. Mean plasma ceruloplasmin concentrations were similar (P=0.19) among treatments. Plasma haptoglobin concentrations were greater (P≤0.04) in TRANS compared to CON and STOP on d 1, and in STOP compared to CON on d 1. In conclusion, inclusion of rest stops during a 1,290-km transport prevented the increase in circulating cortisol and alleviated the NEFA and haptoglobin response elicited by transport, but did not improve feedlot receiving performance of transported cattle.

The aim of the present study was to evaluate the inclusion of narasin, salinomycin, or flavomycin for 140 d on ruminal fermentation parameters, apparent nutrient digestibility, and performance of Nellore cattle offered a forage-based diet. In experiment 1, 32 rumen-cannulated Bos indicus Nellore steers [initial body weight (BW) = 220 ± 12.6 kg] were assigned to individual pens in a randomized complete block design according to their initial shrunk BW. Within block, animals were randomly assigned to 1 of 4 treatments: (1) forage-based diet without feed additives (CON; n = 8), (2) CON diet plus 13 ppm of narasin (NAR; n = 8), (3) CON diet plus 20 ppm of salinomycin (SAL; n = 8), or (4) CON diet plus 3 ppm of flavomycin (FLA; n = 8). The experimental period lasted 140 d and was divided into 5 periods of 28 d each. The inclusion of feed additives did not impact (P ≥ 0.17) dry matter intake (DMI), nutrient intake, and apparent total tract digestibility of nutrients. Nonetheless, steers fed NAR had lower (P &lt; 0.01) molar proportion of acetate compared with CON, SAL, and FLA steers, whereas ruminal acetate tended to be greater (P &lt; 0.09) for SAL vs. CON and FLA, but did not differ (P = 0.68) between CON vs. FLA steers. Ruminal propionate was the highest (P &lt; 0.01) for steers fed NAR and did not differ (P &gt; 0.20) between CON, SAL, and FLA. Consequently, NAR steers had the lowest (P &lt; 0.01) Ac:Pr ratio, whereas Ac:Pr did not differ (P &gt; 0.18) among CON, SAL, and FLA. Total volatile fatty acids were greater (P &lt; 0.04) for NAR and CON vs. SAL and FLA, but did not differ (P &gt; 0.67) among NAR vs. CON and SAL vs. FLA. In experiment 2, 164 Nellore bulls (initial shrunk BW = 299 ± 2.5 kg) were assigned to feedlot pens for 140 d in a randomized complete block design. Within block (n = 10), animals were randomly assigned to the same treatments used in experiment 1. Average daily gain was greater (P &lt; 0.01) in NAR vs. CON, SAL, and FLA bulls, and did not differ (P &gt; 0.12) between CON, SAL, and FLA bulls. Bulls fed NAR had greater (P &lt; 0.02) DMI (as kg/d or % BW) and final shrunk BW compared with CON, SAL, and FLA bulls, whereas DMI and final shrunk BW did not differ (P &gt; 0.26) between CON, SAL, and FLA bulls. Feed efficiency, however, was not impacted (P = 0.51) by any feed additives used herein. Collectively, narasin was the only feed additive that benefited performance and ruminal fermentation of Nellore animals fed a forage-based diet.