Performance Of Beef Cows Research Articles

Effects of vaccination against foot-and-mouth disease virus on reproductive performance of beef cows.

This study compared reproductive performance of cows vaccinated against the foot-and-mouth disease (FMD) virus before timed AI or during early pregnancy (Exp. 1), as well as rectal temperature (RT) and plasma concentrations of the acute-phase protein haptoglobin in cattle vaccinated or not against the FMD virus (Exp. 2). Cattle utilized in Exp. 1 and 2 originated from herds with no historical occurrences of FMD and that received vaccination against the FMD virus biannually. In Exp. 1, 604 lactating, multiparous, nonpregnant Nelore cows were randomly assigned on d -31 of the experiment to receive 1) vaccination against the FMD virus on d ≥ 31 (VACPRE; = 291) and 2) vaccination against FMD virus on d 30 (VACGEST; = 313). From d -11 to 0, all cows were assigned to an estrus synchronization + timed AI (d 0) protocol. Pregnancy status to AI was verified on d 30 and 90 via transrectal ultrasonography. A treatment × day interaction was detected ( < 0.01) for pregnancy rates to AI, which were similar ( = 0.17) between VACPRE and VACGEST on d 30 (61.8% vs. 56.2%, respectively; SEM = 2.8) but greater ( < 0.01) for VACPRE on d 90 (59.4% vs. 46.9%, respectively; SEM = 2.8). Pregnancy loss from d 30 to 90 was greater ( < 0.01) in VACGEST compared with VACPRE (16.5% vs. 3.9%, respectively; SEM = 2.2). In Exp. 2, 40 pregnant Nelore females (20 nulliparous and 20 multiparous cows; BCS = 4.73 ± 0.12) were ranked by parity and assigned to receive (VAC; = 20) or not receive (NOVAC; = 20) vaccination against the FMD virus. Blood samples were collected and RT was recorded before (h 0) and 24, 72, 120, and 168 h after treatment administration. Treatment × day interactions were detected ( < 0.01) for RT and plasma haptoglobin. The RT was greater ( < 0.01) in VAC compared with NOVAC at 24 h after treatment administration and was similar ( ≥ 0.31) between treatments at all other sampling hours. Plasma haptoglobin concentration was similar ( = 0.98) between VAC and NOVAC before treatment administration ( = 0.48) and greater ( < 0.01) in VAC at 24, 72, 120, and 168 h after treatment administration. In summary, vaccinating beef cows against the FMD virus resulted in a 4-fold increase in pregnancy loss when the vaccine was administered 30 d after timed AI compared with 31 d before timed AI. These outcomes can be associated with inflammatory and acute-phase reactions elicited by the FMD vaccine, which are known to impair pregnancy maintenance in cattle.

Supplementation with a mixture of whole rice bran and crude glycerin on metabolic responses and performance of primiparous beef cows

ABSTRACT - This study investigated the effect of a supplement containing whole rice bran and crude glycerin for 21 days before mating on metabolic, productive, and reproductive responses of 28 primiparous suckling beef cows. Cows were randomly assigned to a control group (CON, n = 14), grazing on grasslands, and a supplemented group (SUP, n = 14), grazing on grasslands and supplemented daily individually with 1 kg dry matter (DM) of whole rice bran + 550 mL crude glycerin (224 g kg−1 DM of methanol) per cow. After 33 days of natural mating, cows that had not expressed estrus were subjected to a fixed-time artificial insemination protocol. Ten days after the insemination program, bulls were reintroduced for 21 days. Supplementation increased milk yield (SUP: 5.7±0.2 vs. CON: 5.0±0.2 kg d−1), milk protein content (SUP: 3.1±0.2 vs. CON: 2.8±0.2%), and body weight of cow (SUP: 379±2 vs. CON: 373±2 kg) and calf (SUP: 150±2 vs. CON: 142±2 kg). Supplementation improved the energy balance, increased plasma concentrations of cholesterol (SUP: 223.2±6.4 vs. CON: 202.1±6.4 mg dL−1) and glucose (SUP: 72.0±1.2 vs. CON: 68.6±1.2 mg dL−1), and reduced non-esterified fatty acids (SUP: 0.45±0.02 vs. CON: 0.56±0.02 mmol L−1). The percentage of cows on superficial anestrous after supplementation was greater in SUP than in CON group (57 vs. 21%, respectively); however, no difference in final pregnancy rate was found (SUP: 79 vs. CON: 64%). There was no evidence that the ingestion of crude glycerin with high content of methanol induced clinical or hepatic disorders. Supplementation of whole rice bran and crude glycerin is not toxic, and can improve the energy balance, reflecting in increase in milk yield and calf growth, with a slight effect on the reproductive activity.

Performance of beef cows of different genetic groups in natural and cultivated pastures

The objective was to assess the performance of 96 pregnant cows of the genetic groups (GG) Charolais (C), Nellore (N), ½ CN and ½ NC, subjected to the following treatments: kept exclusively in natural pastures (NP) throughout the experimental period; kept in cultivated pastures (CP) from July 15 to Setp 15 (CPNP) or from Sept 15 to Nov 15 (NPCP) and the remainder of the experimental period in NP. The weight at the end of the first grazing period (Sept 15) was higher for the CPNP cows than those of the NPCP and NP. The weight at the end of the second period (Nov 15) was 456, 428 and 392 kg respectively for NPCP, CPNP and NP. At calving, the heaviest cows were the CPNP, followed by the NPCP and the NP. At weaning, 90 days postpartum, the heaviest were the NPCP, followed by the CPNP and NP. Nelore cows were less heavy in all evaluations, followed by C, with the F1s’ weight higher than the purebreds. The grazing sequences did not affect the percentages of the cows in estrus and pregnancy, but did influence the invervals between calving and first estrus postpartum (ICE). The GG influenced the rate of cows in estrus, pregnant and the ICE which was lower in the F1 (103 days), followed by the C (109 days) and had the largest interval N (119 days). The grazing sequences affect the average daily weight gain (ADG) of calves until weaning at 90 days of age. The GG of the calf affected the ADG at to 210 days.

Influence of prepartum dietary energy on beef cow performance and calf growth and carcass characteristics

Objectives were to evaluate the effects of prepartum dietary energy intake on cow performance as well as performance and carcass characteristics of subsequent progeny. Spring-calving, mature cows (n=106 total) were blocked by BW and allotted to 1 of 2 treatments: ground hay and dried distillers grains plus solubles (REQ: TDN=61.8%, CP=11.0%, fat=2.1%), or corn bran and ground cornstalks (HE: TDN=70.3%, CP=10.0%, fat=5.7%). Treatments were limit-fed as isonitrogenous rations with REQ and HE providing 100% and 125% of TDN requirements, respectively, and were fed from 83±10d prepartum to calving. All cows were fed a common diet postpartum. Cow BW and BCS were recorded at the beginning of the feeding period, 24h post-calving, and at breeding. Milk production was estimated via the weigh–suckle–weigh technique 65±9 and 120±9d postpartum. Calf BW was measured at birth and at weaning (120±9d of age). Calves (n=86) were fed a common feedlot diet beginning 2d after weaning, and individual feed intake was monitored using GrowSafe. Progeny were slaughtered in 3 groups at an average 12th rib fat thickness of 1.3cm. From initiation of experiment to breeding, cow BW change was greater (P<0.01) and BCS change tended to be greater (P=0.09) for HE relative to REQ cows. Birth BW was greater (P=0.02) for calves born to cows fed HE with no increase (P=0.30) in percentage of unassisted births. There were no effects (P≥0.27) of treatment on calving date, milk production, or subsequent pregnancy rate. Calf weaning BW, initial feedlot BW, final BW, and days on feed were not affected (P≥0.20) by treatment. Feedlot DMI, ADG, and G:F were not different (P≥0.35). There was no effect (P≥0.27) of treatment on progeny morbidity. Although progeny born to HE dams tended (P=0.10) to have greater marbling scores at weaning, there was no effect (P≥0.60) of treatment on carcass marbling score or other carcass traits. Feeding cows 125% of TDN requirement during late gestation increased cow BW change and progeny birth body weight. Feeding cows 125% of TDN requirement during late gestation had no effect on pregnancy rate or progeny performance.

Effects of chromium supplementation to beef cows during gestation on beef cow performance and progeny development before weaning

Angus-cross cows (n = 66) were fed 1 of 2 supplements through mid and late gestation: (1) 1.81 kg/d of corn as fed (control) or (2) 1.81 kg of corn fortified with 3 mg/d of Cr as fed (Chrom). Chromium supplementation did not affect (P ≥ 0.24) pre- or postpartum cow BW or BCS, or BW and BCS change. There was an interaction (P < 0.01) of days in gestation and Cr supplementation for glucose concentrations only. During mid gestation, plasma glucose concentrations in cows fed Chrom decreased 0.282 mmol/L compared with cows fed control; however, by late gestation, glucose concentrations in cows fed Chrom increased 0.321 mmol/L compared with cows fed control. Supplementation with Cr did not affect (P ≥ 0.58) insulin concentrations or insulin:glucose; however, insulin and glucose concentrations were reduced (time effect; P < 0.01) as days in gestation increased, regardless of Cr supplementation. There was no effect of dam treatment on calf BW at birth (P = 0.40) or weaning (P = 0.56). Chromium supplementation did not affect (P ≥ 0.20) estimated 24-h milk weight in mid or late lactation. Milk composition was not affected (P ≥ 0.25) by Cr at mid lactation. In late lactation, cows fed Chrom had greater (P = 0.01) milk urea nitrogen compared with cows fed control, with no other differences observed (P ≥ 0.23). In this experiment, supplemental Cr during gestation did not affect cow BW, BCS, milk production, or calf birth and weaning BW. Regardless of treatment, as cows neared parturition, plasma glucose and insulin concentrations of cows decreased.

The effects on cow performance and calf birth and weaning weight of replacing grass silage with brewers grains in a barley straw diet offered to pregnant beef cows of two different breeds.

The effects on cow and calf performance of replacing grass silage with brewers grains in diets based on barley straw and fed to pregnant beef cows are reported. Using a 2×2 factorial arrangement of breed and diet, cows pregnant by artificial insemination (n=34) of two breeds (cross-bred Limousin, n=19 and pure-bred Luing, n=15) were fed diets adlibitum which consisted of either (g/kg dry matter) barley straw (664) and grass silage (325; GS) or barley straw (783) and brewers grains (206, BG) and offered as total mixed rations. From gestation day (GD) 168 until 266, individual daily feed intakes were recorded and cow body weight (BW) and body condition score (BCS) measured weekly. Calving date, calf sex, birth and weaning BW, and calf age at weaning were also recorded. Between GD 168 and 266, cross-bred Limousin cows gained more weight than Luing cows (p<0.05) and cows offered BG gained more weight than cows offered GS (p<0.001). Luing cows lost more BCS than cross-bred Limousin cows (p<0.05), but diet did not affect BCS. There were no differences in dry matter intake as a result of breed or diet. Calf birth BW, however, was greater for cows fed BG than GS (44 vs. 38kg, SEM 1.0, p<0.001) with no difference between breeds. At weaning, calves born to BG-fed cows were heavier than those born to GS-fed cows (330 vs. 286kg, SEM 9.3, p<0.01). In conclusion, replacement of grass silage with brewers grains improved the performance of beef cows and increased calf birth and weaning BW. Further analysis indicated that the superior performance of cows offered the BG diet was most likely due to increases in protein supply which may have improved both energy and protein supply to the foetus.

Prepartum supplement level and age at weaning: I. Effects on pre- and postpartum beef cow performance and calf performance through weaning1

Objectives were to determine the interaction of prepartum supplement level and age at weaning on cow BW, BCS, milk production, reproduction, and calf performance up to weaning in a fall-calving system over 2 yr. Mature, multiparous, Angus × Simmental cows (yr 1: 326 cows, 9 pastures, BW = 632 ± 67 kg, and BCS = 5.7 ± 0.58; yr 2: 383 cows, 9 pastures, BW = 606 ± 70 kg, and BCS = 5.8 ± 0.74) were used in a split-plot design that included 3 supplement levels-no supplement (NS), low supplement (LS; 2.16 kg∙cow∙d), or high supplement (HS; 8.61 kg∙cow∙d)-and 2 ages at weaning-78 ± 11 d of age (early weaned; EW) or 186 ± 11 d of age (normal weaned; NW). Cows grazed endophyte-infected tall fescue/red clover pastures and were bunk fed supplement (70% dried distillers' grains with solubles and 30% soybean hulls) 103 ± 11 d prepartum to 2 ± 11 d postpartum. Cow BW was greater ( < 0.01) for cows fed HS at precalving (49 ± 11 d prepartum), postcalving (26 ± 11 d postpartum), and postbreeding (81 d after AI) compared with cows fed NS and LS. Prepartum supplementation did not affect ( ≥ 0.62) calf birth BW, percent of calves dead at birth, or percent of cows calving unassisted. Prepartum supplementation tended ( = 0.10) to improve AI conception. Early weaning increased ( ≤ 0.05) AI conception and postbreeding cow BW and BCS compared with cows with NW calves. Neither prepartum supplementation nor age at weaning affected ( ≥ 0.28) overall pregnancy rate. At time of early weaning, BW was increased ( = 0.05) for steers from cows fed LS compared with steers from cows fed NS. Steer BW at time of normal weaning and ADG between early and normal weaning was greater ( < 0.01) for EW steers compared with NW steers. A year × age at weaning interaction occurred ( < 0.01) for ultrasound marbling score at time of normal weaning. In yr 1, marbling was decreased ( = 0.04) for EW steers compared with NW steers; however, in yr 2, marbling was increased ( < 0.01) for EW steers compared with NW steers. In conclusion, there was no interaction between level of supplement during late gestation and age at weaning on cow BW, BCS, milk production, AI conception, and overall pregnancy rate in mature beef cows nor in their steer progeny's BW or ultrasound marbling. Both prepartum supplementation and early weaning improved cow BW, BCS, and reproduction. Minimal effects of dam prepartum supplement level on calf performance up to weaning were observed. Early weaning improved calf growth but had inconsistent effects on ultrasound marbling across years.

Effects of late gestation distillers grains supplementation on fall-calving beef cow performance and steer calf growth and carcass characteristics.

Fall-calving, mature Angus and Simmental × Angus cows ( = 251 total) and their progeny were used to evaluate the effects of late gestation dried distillers grains plus solubles (DDGS) supplementation on cow performance and progeny growth and carcass characteristics. Cows were blocked by breed and allotted to 12 tall fescue pastures (6.8 ha average). Pastures were randomly assigned to 1 of 2 treatments: cows were offered 2.1 kg DM DDGS·cow·d (SUP; CP = 23%, fat = 7%; = 6 pastures) or were not offered a supplement (CON; = 6 pastures) 69 ± 9 d before expected calving date. Cows remained on treatments until calving. Once weekly, cows that had calved were removed from treatment pastures and were moved to new tall fescue pastures (21.6 ha average) where cows from both treatments were comingled without further supplementation. Cows ( = 74) were removed from study for calving more than 30 d after expected calving date, calf loss and injury, or euthanasia. Cow BW and BCS were recorded at the beginning of the supplementation period, after calving, and at breeding. Calf BW was taken at birth and early weaning (82 ± 14 d of age). After weaning, 71 steer progeny (representative of dam breed and treatment pastures) were transitioned to a common feedlot diet with individual feed intake monitored using the GrowSafe feeding system. Steers were slaughtered at 47 ± 4 d after a minimum 12th rib fat thickness (back fat) estimation of 0.6 cm, with cattle being shipped in 3 groups. Forage availability was not different between treatments ( = 0.69). Cows offered SUP gained more BW and BCS ( ≤ 0.02) during the supplementation period. There were no differences ( ≥ 0.12) in calving date, calf birth or weaning BW, or preweaning ADG. Cow BW at breeding was not different ( = 0.19); however, BCS at breeding was greater ( < 0.01) for cows offered supplement. No differences ( ≥ 0.11) in milk production, AI conception, or overall pregnancy rate were detected. For steer progeny, initial feedlot BW, final BW, and days on feed were not different ( ≥ 0.35); no difference ( = 0.77) in feedlot ADG was detected. Feedlot DMI and G:F were not different ( ≥ 0.52) across treatments. No differences ( = 0.62) in morbidity were observed in the feedlot. No differences ( ≥ 0.19) were detected for HCW, LM area, marbling score, or yield grade. Prepartum DDGS supplementation improved cow BW and BCS but did not alter milk production, subsequent reproduction, or subsequent calf performance or carcass characteristics.

Limited creep-feeding supplementation effects on performance of beef cows and calves grazing limpograss pastures

Limpograss (Hemarthria altissima) is a warm-season grass used by cow–calf producers in South Florida; however, limpograss protein concentration may limit animal performance. The objective of this study was to test the effects of creep-fed protein supplement on performance of cow–calf pairs grazing limpograss pastures. The experiments were conducted in Ona, FL from June to September 2011 (Experiment 1) and from June to August 2012 (Experiment 2). Twenty-four cows and calves [Angus-sired calves on crossbred cows (approximately 63% Bos taurus and 37% Bos indicus)] were randomly distributed in eight limpograss pastures (1.0ha/pasture). In Experiment 1, calves received 200g/d of soybean meal (SBM, 48% CP) daily by creep-feeding or no supplement (control). Treatments were distributed in a randomized complete block design with four replicates. In Experiment 2, calves received 200 or 400g/d of SBM daily by creep-feeding or no supplement (control) distributed in a randomized incomplete block design with three replicates for 200g/d and control and two replicates for 400g/d. In Experiment 1, there was no difference in HM (P=0.54; mean=4500±800kg/ha), in vitro digestible organic matter (IVDOM; P=0.92; mean=62±1.4%) and crude protein concentration (CP; P=0.14; mean=14.3±0.9%) between treatments. In addition, there was no difference in cow and calf ADG (P=0.51; mean=0.25±0.1kg/d and P=0.24; 0.55±0.1kg/d for cows and calves ADG, respectively). In Experiment 2, there was no effect of creep-feeding on HM (P=0.28; mean=6800±700kg/ha), IVDOM (P=0.31; mean=52±3.5%), and CP (P=0.63; mean=11.1±0.5%) concentrations; however, there was a linear (P=0.03) increase in ADG from 0.33 to 0.62kg/d for calves receiving from 0 to 400g/d SBM. Cow ADG was similar among treatments (P=0.44; mean=0.23±0.12kg/d). Calves receiving 400g/d SBM had 0.75kg BW/kg feed added gain efficiency {[BW gain of creep-fed calves (kg) – BW gain of control calves (kg)]/[amount of feed consumed during the experimental period (kg)]}, and a tendency for 70% linear increase in economic return (P=0.06), when compared with the control calves. Limited creep-feeding of SBM supplement may be an effective management practice to improve weaning weights of beef calves on limpograss pastures.

Performance of beef cows and calves fed different sources of rumen-degradable protein when grazing stockpiled limpograss pastures.

Two experiments evaluated the effects of different sources of RDP on forage characteristics, animal performance, and ruminal and blood parameters of beef cattle grazing stockpiled limpograss (Hemarthria altissima) from January to May 2011 and 2012. In Exp. 1, 24 mature lactating beef cows and their respective calves were allocated to 8 stockpiled limpograss pastures (3 pairs/pasture). Treatments were 2 different sources of RDP, urea or cottonseed (Gossypium spp.) meal (CSM), distributed in a completely randomized design with 4 replicates. Feather meal and corn (Zea mays) meal were added to the urea treatments to balance RUP and energy. Treatments were mixed in sugarcane (Saccharum officinarum) molasses, which resulted in 3 kg DM/cow per day of supplement. There were no differences (P > 0.10) in herbage mass (HM; 3,200 ± 400 kg DM/ha), herbage allowance (HA; 1.9 ± 0.2 kg DM/kg of BW), CP (5.2 ± 0.2%), and in vitro digestible organic matter (IVDOM; 47 ± 0.5%) concentrations. There was a decrease (P < 0.10) in HM (from 4,100 to 2,600 kg/ha), IVDOM (from 46 to 39.9%), and HA (from 2.5 to 1.4 kg DM/kg BW) from January to March. Cow ADG (0.23 ± 0.08 kg/d), BCS (4.6 ± 0.2), milk yield (7.0 ± 0.4 kg/d), and plasma urea nitrogen (PUN; 16.1 ± 0.8 mg/dL) and calf ADG (0.71 ± 0.05 kg/d) were similar (P > 0.10) among treatments. Sixteen cow-calf pairs were moved to 8 drylot pens after Exp. 1, maintained on the same treatment, and evaluated for forage and total DMI. There was no difference in forage (P = 0.16; 2.1 ± 0.1% BW) and total DMI (P = 0.12; 2.5 ± 0.1% BW) between treatments. In Exp. 2, 2 rumen-cannulated steers were used in a 2 × 2 Latin square design, replicated in 2011 and 2012, to test the effects of the same treatments on rumen fluid and blood parameters. There was no difference (P > 0.10) in ruminal NH3-N (12.9 ± 0.3 mg/dL), pH (6.5 ± 0.1), propionic acid (25 ± 2.2 mol/100 mol), acetic acid (69.2 ± 2.9 mol/100 mol), and butyric acid (4.5 ± 0.5 mol/100 mol) as well as branched-chain VFA (1.3 ± 2.2 mol/100 mol) concentrations in the rumen. In addition, there was no difference (P = 0.91) in PUN (7.9 ± 0.3 mg/dL) concentration between treatments. Therefore, urea can be as effective as CSM as the main source of RDP in the molasses-based supplement offered to mature lactating beef cows grazing stockpiled limpograss pastures.

Calm temperament improves reproductive performance of beef cows.

Profitability of a beef operation is determined by the proportion of cows attaining pregnancy early in the breeding season and those that are pregnant at the end of breeding season. Many factors, including temperament, contribute to those reproductive parameters. The objective of this study was to evaluate effects of temperament on reproductive performance of beef cows. In Experiment 1, Angus and Angus-cross beef cows (n = 1546) from eight locations were assigned a body condition score (BCS; 1 = emaciated; 9 = obese) and chute exit and gait score (1 = slow exit, walk; calm temperament; 2 = jump, trot or run; excitable temperament). Cows were grouped with bulls (1 : 25 to 1 : 30; with satisfactory breeding potential and free of venereal disease) for an 85-day breeding season. Pregnancy status and stage of gestation were determined (transrectal palpation) 35 days after the end of the breeding season. Controlling for BCS (p < 0.01) and handling facility (p < 0.0001) and handling facility by temperament score interaction (p < 0.001), breeding season pregnancy rate was lower in excited versus calm cows [88.6% (798/901) vs 94.1% (607/645); p < 0.001]. Cows with an excitable temperament took 24 more days to become pregnant compared to calm cows (median days to pregnancy, 35 vs 59 days; p < 0.0001). In Experiment 2, Angus and Angus-cross beef cows (n = 1407) from 8 locations were assigned scores for body condition and chute exit and gait (as described in Experiment 1) and assigned to bulls (breeding sound and free of venereal disease; 1 : 25 to 1 : 30) for 85 days. Pregnancy status was determined by transrectal palpation at 2 and 6 months after the onset of the breeding season. Controlling for BCS (p < 0.05), pregnancy loss was higher in excited versus calm cows [5.5% (36/651) vs 3.2% (20/623), p < 0.0001]. In conclusion, beef cows with an excitable temperament had significantly lower reproductive performance than calmer cows. The modified two-point chute exit-gait scoring method was repeatable and identified cattle with an excitable temperament.

Effects of mannan oligosaccharide on beef-cow performance and passive immunity transfer to calves

This experiment investigated the effects of feeding mannan oligosaccharide to beef cows during late gestation through 30 d of lactation on cow and calf performance and calf passive immunity. Angus and Angus×Hereford cows (n=69; BW=569±68 kg; age=5.3±7 yr) were allotted by BW and age in a completely randomized designed. Cows were assigned to 1 of 2 treatments including 1) 1.36 kg/d during gestation of a cottonseed meal–based 30% CP supplement and 1.81 kg/d during lactation of a cottonseed meal–based 38% CP supplement (control); 2) control plus 10 g/d of Bio-Mos (Bio-Mos; Alltech Inc., Nicholasville, KY). Experimental supplementation began on February 14, 2012, and was terminated after cows consumed the lactation diet for at least 30 d. Cow and calf blood and colostrum were collected within 12 h of parturition. Cows fed Bio-Mos tended to maintain more BW from parturition through the end of the feeding period (P=0.10). Similarly, cows consuming Bio-Mos were better able to maintain BCS from initiation of the experiment through weaning (P=0.05). At parturition, no differences for IgG1 concentrations in colostrum (P=0.28), cow serum (P=0.19), or calf serum (P=0.70) were detected. Similarly, parturition calf serum IgG2, IgA, or IgM concentrations were not different (P>0.14). Adding Bio-Mos to winter supplement may limit BCS loss following parturition in spring-calving beef cows; however, there was no effect on passive immunity characteristics.

Suplementação com gordura protegida para vacas de corte desmamadas precocemente mantidas em pastagem natural

Avaliaram-se os desempenhos produtivo e reprodutivo de vacas de corte, bem como o desempenho de seus bezerros, de acordo com os tratamentos alimentares: PRE: suplementação com gordura protegida (GP) 45 dias antes do parto; PREPOS: suplementação com GP 45 dias antes do parto e 63 dias pós-parto; POS: suplementação com GP 63 dias pós-parto; PN: sem suplementação. O desempenho produtivo das vacas não foi influenciado pelo manejo alimentar (P&gt;0,05), exceto para o escore da condição corporal (ECC) no final do período de acasalamento, que foi mais baixo para as vacas do PRE e do PREPOS, sendo que esta última apresentou ECC semelhante ao das vacas do POS e do PN. O intervalo entre partos foi menor para as vacas do tratamento PREPOS - 376 dias -, não diferindo das vacas do PN - 383 dias. As vacas do PREPOS desmamaram 4,4% mais quilos de bezerro para cada 100kg de vaca ao parto - 22,6kg - do que as vacas do PRE e do POS - 21,6kg e 21,6kg, respectivamente - e 8,4% mais quilos de bezerro para cada 100kg de vaca ao parto do que as vacas mantidas em pastagem nativa - 20,7kg. A suplementação com gordura protegida durante os períodos pré e/ou pós-parto não afeta o desempenho de vacas e bezerros.

Using corn stover and dried distillers grains with solubles to conserve stockpiled forages and improve reproductive performance and progeny growth in fall-calving beef cows

Angus-cross, fall-calving beef cows (n = 153) were used in this experiment. The objective was to determine whether incorporating a period of corn stover and dried distiller grains with solubles (DDGS) feeding into a preexisting nutritional program that included grazing stockpiled tall fescue affects reproductive performance and progeny growth. On Julian d 267 cows were stratified and allotted by BW, BCS, and calving date (if calved) to receive 1 of 2 isocaloric dietary treatments through timed AI (TAI; Julian d 336): stockpiled tall fescue (CON) or corn stover plus DDGS (DG; DDGS at 0.7% of BW/d). Following timed AI, CON cows were fed grass hay, and DG cows were placed on stockpiled tall fescue until grass was exhausted (Julian d 20) and then fed grass hay. Cow BW and BCS did not differ during the supplementation period. The proportion of cows cycling at breeding-season initiation tended (P = 0.06) to be greater in CON(92.2%) than in DG-treated (80.6%) cows. Pregnancy rates from timed AI did not differ between the CON (42.4%) and DG (50.0%) treatment. However, breeding-season pregnancy rates were greater (P = 0.03) in the DG (89.6%) than CON (74.2%) treatment. Progeny from cows fed DG were heavier at 62 d of age and at weaning (P ≤ 0.03) when compared with CON progeny. In summary, including a dietary period of corn stover and DDGS to a traditional management practice of grazing stockpiled tall fescue and feeding hay resulted in greater breeding-season pregnancy rates and heavier progeny.

Feeding behavior, ruminal fermentation, and performance of pregnant beef cows differing in phenotypic residual feed intake offered grass silage1

This study examined the relationship of residual feed intake (RFI) and performance with feeding behavior and ruminal fermentation variables in pregnant beef cows offered a grass silage diet. Individual grass silage DMI (dry matter digestibility = 666 g/kg) was recorded on 47 gestating (mean gestation d 166, SD = 26 d) Simmental and Simmental × Holstein-Friesian beef cows for a period of 80 d. Cow BW, BCS, skeletal measurements, ultrasonically scanned muscle and fat depth, visual muscular score, ruminal fermentation, blood metabolites, and feeding behavior were measured. Phenotypic RFI was calculated as actual DMI minus expected DMI. Expected DMI was computed for each animal by regressing DMI on conceptus-adjusted mean BW(0.75) and ADG over an 80-d period. Within breed, cows were ranked by RFI into low (efficient), medium, or high groups. Overall mean (SD) values for DMI (kg/d), RFI, initial conceptus-adjusted BW, and conceptus-adjusted ADG were 8.41 (1.09) kg/d, 0.01 (0.13) kg/d, 646 (70) kg, and -0.07 (0.32) kg, respectively. High-RFI cows ate 25% and 8% more than low- and medium-RFI cows, respectively. Live weight and ADG were not correlated (P > 0.05), and DMI was positively correlated (r = 0.80; P < 0.001) with RFI. The low- and high-RFI groups had similar (P > 0.05) BW, ADG, BCS, visual muscular scores, skeletal measurements, blood metabolites, calf birth weight, and calving difficulty scores. All ultrasonic fat and muscle depth measurements were similar (P > 0.05) for low- and high-RFI cows except for back fat thickness change, where low-RFI cows gained less fat (P < 0.05) than high-RFI cows. Low-RFI cows had greater pH and lower ammonia concentrations in ruminal fluid compared to their high-RFI contemporaries. Low-RFI cows had fewer (P < 0.001) daily feeding events, but these were of longer (P < 0.001) duration (min·feed event(-1)·d(-1)). Despite this, total daily duration of feeding was shorter (P < 0.001; min/d) for low- compared to high-RFI cows. High-RFI cows had more and a longer total duration of nonfeeding events (P < 0.001) than low-RFI cows. This study showed that compared to cows with high RFI, those with low RFI consumed less feed for similar levels of productivity, spent less time engaged in feeding-behavior-related activities, and differed in ruminal fermentation parameters. Feeding events are a significant (17%) contributory factor to variation in RFI in pregnant beef cows offered grass silage.

Incorporation of sexed semen into reproductive management of cow–calf operations

The objective of this experiment was to compare reproductive performance and weaning outcomes of beef cows inseminated with sexed or conventional semen. Over 2 consecutive years, lactating Angus×Hereford cows were assigned to an estrus synchronization+artificial insemination (AI) protocol. At the time of AI, cows were ranked by parity and assigned to be inseminated with conventional non-sorted semen (CONV; n=454) or with semen sorted for male sperm (SEXED; n=439). Beginning 18 days after AI, cows from both treatments were grouped and exposed to mature bulls for 50 days (1:25 bull to cow ratio). Cow pregnancy status to AI was verified by detecting a fetus via transrectal ultrasonography 40 days after AI. Calf birth date, sex, and birth BW were recorded during the subsequent calving season. Cows that were diagnosed as pregnant during the transrectal ultrasonography exam and gave birth during the initial 2 weeks of the calving season were considered pregnant to AI. Pregnancy rates to AI and final pregnancy rates (AI+bull breeding) were reduced (P≤0.05) in SEXED compared with CONV cows. The proportion of male calves born to AI or AI+bull breeding was greater (P<0.01) in SEXED compared with CONV cows. No treatment effect was detected (P=0.34) for weaning rate, whereas SEXED cows had a greater (P<0.01) proportion of steers in the weaned calf crop compared with CONV cows. Steers and heifers from SEXED cows were younger (P<0.01), whereas only SEXED heifers were lighter (P=0.05) at weaning compared with cohorts from CONV cows. Across genders, calves from SEXED cows had reduced (P≤0.01) weaning age and BW compared with calves from CONV cows. Cows assigned to SEXED had greater (P=0.05) kg of steer weaned/cow exposed to breeding, but reduced kg of heifer weaned/cow exposed to breeding (P<0.01) compared with CONV cows. Across genders, SEXED cows tended (P=0.09) to have reduced kg of calf weaned/cow exposed to breeding compared with CONV cows. In summary, inseminating beef cows with sexed semen reduced pregnancy rates, but increased the proportion of steers weaned and kg of steers weaned/cow exposed to breeding. However, overall kg of calf weaned/cow exposed to breeding was not improved by the use of sexed semen, particularly because of its negative impacts on weaning age and BW of the heifer progeny.

Genetics of reproductive performance in seasonal calving beef cows and its association with performance traits

Due primarily to a lack of phenotypic data, little research has been undertaken on the genetics of reproductive performance in beef cattle. The objective of this study was to quantify, using data from the Irish national cattle herd, the contribution of additive genetics to phenotypic differences in reproductive performance in beef cattle and to investigate whether routinely available early predictors of genetic merit for reproductive performance exist. Up to 218,718 parity records from 156,506 animals were used to estimate variance components for a range of reproductive traits using repeatability animal linear mixed models. Covariances with performance traits were estimated using bivariate sire linear mixed models. The reproductive traits were age at first calving, calving in the first 42 d of the calving seasons (defined separately in heifers and cows), calving interval between consecutive calving events, and survival to the next lactation. Performance traits included calving dystocia, linear type traits describing the skeletal, muscular, and functional characteristics of an animal, live weight and price, carcass traits, and producer subjectively scored traits of weanling quality and docility. Heritability for age at first calving was 0.31 while the heritability of the remaining reproductive traits ranged from 0.01 to 0.06; repeatability estimates varied from 0.02 to 0.06. Increased muscularity, measured either by trained assessors or producers on live animals, or by mechanical grading machines on slaughtered animals (i.e., carcass conformation), was genetically correlated with reduced reproductive performance for some of the reproductive variables assessed. This is one of the largest studies undertaken on the genetics of reproduction in beef herds and clearly shows that genetic selection for improved reproductive performance in beef herds is feasible. However, breeding goals that select for muscularity and live weight or growth rate should be cognizant of indirect response to selection that may cause any deterioration in reproductive performance.

Effects of maternal nutrient restriction followed by realimentation during early and midgestation on beef cows. I. Maternal performance and organ weights at different stages of gestation1,2

The objectives were to evaluate the effects of nutrient restriction during early to midgestation followed by realimentation on maternal performance and organ mass in pregnant beef cows. On d 30 of pregnancy, multiparous, nonlactating cows (initial BW = 620.5 ± 11.3 kg and BCS = 5.1 ± 0.1) were assigned to 1 of 3 dietary treatments: control (CON; 100% NRC; n = 18) and restricted (RES; 60% NRC; n = 30). On d 85, cows were slaughtered (CON, n = 6; R, n = 6), remained on control (CC; n = 12) and restricted (RR; n = 12), or were realimented to control (RC; n = 11). On d 140, cows were slaughtered (CC, n = 6; RR, n = 6; RC, n = 5), remained on control (CCC, n = 6; RCC, n = 5), or were realimented to control (RRC, n = 6). On d 254, all remaining cows were slaughtered. Cows were weighed before slaughter and all maternal organs were dissected and weighed. The diet consisted of grass hay to meet 100 or 60% NEm recommendations for fetal growth and to meet or exceed recommendations for other nutrients. At d 85 slaughters, BW and empty BW (EBW) were not affected (P ≥ 0.84) by maternal nutrition. However back fat was decreased (P = 0.05) in RES vs. CON cows. Large intestine and abomasum mass were increased (P ≤ 0.05) in RES cows vs. CON. At d 140, BW was decreased (P = 0.05) and EBW tended to be decreased (P = 0.10) in RRC cows vs. CCC and RCC being intermediate. Liver mass was decreased (P = 0.02) in RR vs. CC with RC being intermediate. Ruminal mass was decreased (P = 0.003) in RR vs. CC and RC cows. At d 254, BW and EBW were similar (P ≥ 0.78) across treatments. We observed partial changes in maternal weight and organ masses due to different lengths of maternal nutrient restriction followed by realimentation. It appears that the dam undergoes some adaptations during an early to midgestation nutrient restriction and becomes more efficient in the utilization of nutrients after being realimented and as gestation advances.

BEEF SPECIES SYMPOSIUM: An assessment of the 1996 Beef NRC: Metabolizable protein supply and demand and effectiveness of model performance prediction of beef females within extensive grazing systems1,2,3

Interannual variation of forage quantity and quality driven by precipitation events influence beef livestock production systems within the Southern and Northern Plains and Pacific West, which combined represent 60% (approximately 17.5 million) of the total beef cows in the United States. The beef cattle requirements published by the NRC are an important tool and excellent resource for both professionals and producers to use when implementing feeding practices and nutritional programs within the various production systems. The objectives of this paper include evaluation of the 1996 Beef NRC model in terms of effectiveness in predicting extensive range beef cow performance within arid and semiarid environments using available data sets, identifying model inefficiencies that could be refined to improve the precision of predicting protein supply and demand for range beef cows, and last, providing recommendations for future areas of research. An important addition to the current Beef NRC model would be to allow users to provide region-specific forage characteristics and the ability to describe supplement composition, amount, and delivery frequency. Beef NRC models would then need to be modified to account for the N recycling that occurs throughout a supplementation interval and the impact that this would have on microbial efficiency and microbial protein supply. The Beef NRC should also consider the role of ruminal and postruminal supply and demand of specific limiting AA. Additional considerations should include the partitioning effects of nitrogenous compounds under different physiological production stages (e.g., lactation, pregnancy, and periods of BW loss). The intent of information provided is to aid revision of the Beef NRC by providing supporting material for changes and identifying gaps in existing scientific literature where future research is needed to enhance the predictive precision and application of the Beef NRC models.

Effects of corn steep liquor supplementation on performance and herbivory patterns of beef Cows Grazing Native Range Infested with Sericea Lespedeza (Lespedeza cuneata) (2014)

Increased grazing pressure on sericea lespedeza by beef cattle, the most economically relevant herbivore in the region, may slow its spread and facilitate some measure of biological control. Unfortunately, mature plants contain high levels of condensed tannins that decrease protein digestion by beef cattle, and these compounds are potent deterrents to grazing. Supplementing corn steep liquor has been shown to alleviate the negative effects associated with ingestion of condensed tannins when beef cattle are fed prairie hay contaminated with sericea lespedeza. In addition, beef cows supplemented with corn steep liquor did not discriminate between sericea lespedeza-contaminated and sericea lespedeza-free prairie hay in a preference trial. Therefore, the objective of our study was to evaluate the effects of supplemental corn steep liquor on herbivory patterns and performance of beef cows grazing native tallgrass rangeland infested with sericea lespedeza.