Genomic Analysis of Purebred and Crossbred Angus Cows Quantifies Heterozygosity, Breed, and Additive Effects on Components of Reproduction

Multiple studies have quantified the production differences of Hereford Angus crossbreds compared to purebred Angus for a range of traits including growth, carcass, and reproductive traits. This study aims to quantify breed and heterosis effects on maternal performance using genomics. Thirty Hereford and thirty Angus sires were mated to 1100 Angus heifers and cows in a large commercial herd run on pasture at Musselroe Bay, Tasmania, Australia. Approximately 1650 calves were born. Heifers were weaned, scanned for attainment of puberty prior to joining at approximately 15 months of age, joined, and then recorded for status of pregnancy, calving, lactating, 2nd pregnancy, and weaning of second calf. Heterozygosity effects were significant for heifer pre-joining weight and height as well as proportion pubertal. Breed differences were significant for the same traits plus pregnancy rate at second joining and proportion rearing two calves. Genetic parameters were reported for 13 traits. On average, higher genetic merit (Estimated Breeding Value, EBV percentile) Hereford bulls were used than Angus for growth and puberty, but they were similar for fat and reproduction. Days to calving BREEDPLAN EBVs of the sires were related to puberty and reproduction. Scrotal size BREEDPLAN EBVs of the sires were related to attainment of puberty genomic EBVs calculated. In summary, breed differences in growth and puberty were due to heterosis, but there was an advantage of Hereford genes for reproductive performance. Ongoing emphasis on selection for reduced days to calving and estimation of multi-breed EBVs is important.

PSXI-14 Enteric methane and nitrogen emissions in cattle consuming tanniferous and non-tanniferous legumes, grass or a ration

Incorporation of legumes into forage systems has been a widely adopted strategy to increase pasture productivity and forage nutritive value, while reducing N inputs. In addition, some legumes contain beneficial chemicals like condensed tannins (CT), which could enhance the efficiency of energy and protein use in ruminants relative to other forages. We assessed (i) animal performance, (ii) methane emissions (SF6 technique), and (iii) concentration of nitrogen in urine and blood in cattle grazing a CT-containing legume (birdsfoot trefoil; BFT), a legume without tannins (cicer milkvetch; CMV), a grass (meadow brome; MB), or in cattle fed a total mixed ration (TMR). Fifteen Angus heifers were randomly assigned to one of three treatment pastures: (1) BFT, (2) CMV, and (3) MB. Each treatment had 5 spatial replications, randomly divided into three paddocks (64 × 57m), seeded with BFT, CMV or MB, and one heifer was assigned to each paddock. Five Angus heifers were randomly assigned to individual adjacent pens and received a TMR ration (25% of alfalfa hay, 25% corn silage and 50% chopped barley) during the same period. Response variables were analyzed as a split-plot design, with experimental units as the random factor and treatment as a fixed factor with day as the repeated measure. Cows grazing BFT (1.9% condensed tannins) or fed the TMR showed greater weight gains than cows grazing CMV or MB (P = 0.0006). Methane emissions did not differ among treatments (P > 0.05; Table 1). Blood urea nitrogen concentrations were similar in cows grazing BFT or CMV (P = 0.1202), but greater than in animals grazing MB or fed TMR (P < .0001). Urinary nitrogen concentrations were similar among treatments (P = 0.5266). These results suggest grazing tanniferous legumes enhanced BW gains with similar methane and urinary nitrogen emissions to grass and confinement alternatives and greater levels of production than grass or CMV.

283 Precision versus Group Supplementation at Two Levels on Growth and Development of Replacement Heifers

Two experiments were conducted to evaluate use of the Super SmartFeeder (SSF; C-Lock, Inc.) for individual versus group supplementation of heifers grazing stockpiled, novel tall fescue. In experiment 1, Angus heifers (n = 64; 267 + 31.7 kg) had access to the SSF and were allowed 3.6 kg/d of grower supplement. Individual intake was recorded daily and analyzed to determine adoption. Twenty-four percent of the heifers did not adopt to individual SSF supplementation (P < 0.05). In experiment 2, heifers (n = 64; BW= 275 + 31.3 kg) were allotted, based on adoption to SSF, to supplementation system of group feeding (n = 2 reps/level; GRP) or SSF precision feeding (n =16/level; PRE) at two levels (0.5% or 1% of BW) for 127-d in a 2 x 2 factorial. Data were analyzed using Mixed procedure. The interaction between supplementation level and feeding system tended to be significant (P = 0.10) for overall ADG. Average daily gain was greater for 1% BW than 0.5% BW (0.81 vs. 0.47 kg/d) for PRE but did not differ for GRP (0.69 kg/d). Daily supplement dry matter intake differed (P < 0.05) by supplementation level and total BW gain was greater (P < 0.05) by 24.3 kg for 1% versus 0.5% supplementation level. Ultrasound ribeye area and fat thickness measures were greater (P < 0.05) for 1% BW supplement compared to 0.5% BW at the end of the 127d study. When PRE was analyzed independently, heifer BW differed (P < 0.05) on d 91, 117 and 127 between supplement levels. The correlation between individual heifer daily supplement intake and overall ADG for PRE was 0.68 (P < 0.0001). The use of technology to precisely control intake in a grazing system created greater divergence in growth by supplementation level compared to group feeding systems.

PSXII-16 Fertility affects in yearling beef heifers grazing triticale before artificial insemination

Our objective was to compare two systems of pre-breeding heifer development, drylot (D) or grazing winter triticale (T) on heifer fertility. In each of 4 years (yr), Black Angus heifers (n = 168, 86, 97 and 103, respectively) were allotted to treatment (trt) 32 to 50 days (d) prior to artificial insemination (AI). Each year a 14-d CIDR PG protocol was used to synchronize estrus (d-30 to d-16: 1.38 g progesterone intravaginal insert, CIDR; d 0: 25 mg dinoprost tromethamine injection; + 66 hours: 100 µg gonadorelin hydrochloride injection, and AI). Starting body weight and body condition were similar between treatments but differed by year (P < 0.01). After CIDR removal, 83% were in estrus by d -10 and did not differ with trt or yr. Weight at AI was greater (P < 0.01) for T (384 kg ± 2) than D (378 kg ± 2) with a trt by yr interaction. Body condition change between start of treatment and AI was greater (P < 0.01) for T (0.44 ± 0.03) than D (-0.02 ± 0.04) with a trt by yr interaction (P < 0.01) due to the magnitude of difference. A trt by yr interaction occurred for estrous response before AI (P < 0.01). Treatment means for AIPR were 59.1% (143/242) for D and 42.1% (101/240) for T (trt; P < 0.01). AIPR was similar between treatments in yr 1 and higher for D than T in subsequent yr (trt x yr, P < 0.05). Blood urea nitrogen was greater (P < 0.05) in T than D on d 0 and at AI. At the time of AI, triticale was more mature in yr 1 when there was no difference in AIPR. Grazing triticale during estrus synchronization and AI resulted in acceptable gains but decreased fertility in yearling beef heifers.

Forage intake by heifers on alexander grass (Urochloa plantaginea (Link.) Hitch) fertilized with different levels of nitrogen

This work was conducted to study the efficiency of using nitrogen on Alexander Grass (Urochloa plantaginea (Link.) Hitch) through information about the characteristics of the pasture and forage intake of beef heifers. The experiment was carried out at the Federal University of Santa Maria (Universidade Federal de Santa Maria, UFSM) in Santa Maria, Rio Grande do Sul, Brazil, from January to April of 2014. The treatments consisted of doses of zero, 150, or 300 kg/ ha nitrogen (N) in the form of urea. The study used a rotational pasture method and 16 Angus heifers with a mean initial age and body weight (BW) of 15 months and 276 ± 17.4 kg, respectively. Forage intake was evaluated by treating two picketed test heifers with chromium oxide (Cr2O3) for eleven days as an external indicator of fecal production. The experimental design was completely randomized, and the measurements were repeated over time with three treatments and two repetitions per area. Crude protein content was 3.4% higher under 300 kg/ha nitrogen fertilization compared to 150 kg/ ha (18.7%). Independent of the N application rate, the heifers ingested 2.2 ± 0.09 kg DM 100/ kg BW of forage. Nitrogen fertilization of Alexander grass modified the structure of the pasture, increasing the quality and total production of the forage. Heifers pastured on Alexander grass fertilized with 300 kg/ha nitrogen harvested forage with higher levels of crude protein. The structural change in the canopy let the heifers reduce their consumption of forage at the end of the Alexander grass life cycle.

Characterization of Phytoestrogens in Medicago sativa L. and Grazing Beef Cattle

Phytoestrogens are plant-produced bioactive secondary metabolites known to play an integral role in plant defense that frequently accumulate in times of stress and/or microbial infection. Phytoestrogens typically belong to two distinct chemical classes; flavonoids (isoflavones) and non-flavonoids (lignans and coumestans). Upon consumption by livestock, high concentrations of phytoestrogens can cause long-term disruption in reproduction due to structural similarities with mammalian estrogens and their tendency to bind estrogen receptors. Wide variation in phytoestrogen concentration has been reported in pasture legumes and corresponding silage or hay. Lucerne is a common perennial pasture legume in temperate climates, but information on phytoestrogen production or accumulation in grazing livestock is currently limited. Therefore, metabolic profiling using UHPLC-MS-QToF was performed to identify and quantitate key phytoestrogens in both fresh and dried lucerne fodder from replicated field or controlled glasshouse environments. Phytoestrogens were also profiled in the blood plasma of Angus cattle grazing field-grown lucerne. Results revealed that phytoestrogens varied quantitatively and qualitatively among selected lucerne cultivars grown under glasshouse conditions. Fresh lucerne samples contained higher concentrations of coumestans and other phytoestrogenic isoflavones than did dried samples for all cultivars profiled, with several exceeding desirable threshold levels for grazing cattle. Coumestans and isoflavones profiled in plasma of Angus heifers grazing lucerne increased significantly over a 21-day sampling period following experimental initiation. Currently, threshold concentrations for phytoestrogens in plasma are unreported. However, total phytoestrogen concentration exceeded 300 mg·kg−1 in fresh and 180 mg·kg−1 in dried samples of selected cultivars, suggesting that certain genotypes may upregulate phytoestrogen production, while others may prove suitable sources of fodder for grazing livestock.

Investigating the Effects of Distillers Grains on Heifer Feeding Behavior in the Finishing Phase

The objective was to determine the effect of low inclusion levels of dried distillers grains (DDG) on feeding behavior in heifers consuming a high-moisture corn-based diet in the finishing phase. Simmental × Angus heifers (N = 90; 323 ± 50 kg) were fed for 180 d. Heifers were blocked by initial body weight (BW) into two groups, stratified by sire, and assigned to 15 pens with six heifers each. Pens were randomly assigned to one of three dietary treatments: 0% DDG inclusion (0DG), 7% DDG inclusion (7DG), or 14% DDG inclusion (14DG). Treatments did not affect (p > 0.59) BW, average daily gain, and gain:feed. Although there was a treatment × time effect (p = 0.05) for dry matter intake (DMI), with 0DG having greater DMI during the last 70 d, no differences in overall DMI were detected. Treatment affected (p < 0.01) bunk visit duration and head down duration, with 7DG and 14DG having less minutes per day. Bunk visit frequency (p = 0.02) was less variable for heifers fed 14DG and DMI tended (p = 0.08) to be less variable for both distillers treatments. While dietary inclusion of DDG has minimal effects on overall heifer performance, low levels of DDG inclusion can affect feeding behavior and intake variation.

PSI-8 Evaluating the Effects of Individual Eating Rates of Feedlot Heifers on Ruminal Fermentation Using an Ex vivo Model

The objective was to determine if the eating rate of individual feedlot heifers affects ruminal fermentation using an ex vivo model. Differences in eating rate could affect ruminal fermentation and predispose an animal to be susceptible to metabolic disorders. From a contemporary group of Simmental × Angus heifers (n = 90; BW = 323 kg), 14 heifers were selected for divergent individual eating rates. During the initial 30 d on the finishing diet, a GrowSafe feed intake system was used to identify the heifers with the 7 fastest (7.60 kg DM / h; 9.25 kg DMI in 1.2 h) and 7 slowest (1.38 kg DM / h; 9.24 kg DMI in 6.7 h) eating rates. Prior to feeding, rumen fluid was collected via esophageal tubing 1 d after intake evaluation period. Each rumen fluid sample was mixed with McDougall’s buffer and a common feed substrate (similar to finishing diet). Then the samples were incubated for 24 and 48 h. In vitro dry matter disappearance (IVDMD), pH, volatile fatty acids (VFA), and ammonia were measured following incubation. The MIXED procedure of SAS 9.4 was used for statistical analysis. No eating rate by incubation time interactions (P ≥ 0.11) were observed. Although heifer eating rate did not affect (P = 0.65) IVDMD, values were greater (P &lt; 0.01) at 48 h compared with 24 h. While time affected pH as it decreased (P &lt; 0.01) from 24 to 48 h, heifer eating rate did not affect (P = 0.84) pH. Eating rate had no effect (P ≥ 0.10) on ammonia, total VFA, and molar proportions of acetate, propionate, isobutyrate, butyrate, valerate, and isovalerate at 24 h. Overall, the results indicated individual eating rates of feedlot heifers did not affect ruminal fermentation using an ex vivo model.

A Case Study on the Use of Virtual Fencing to Intensively Graze Angus Heifers Using Moving Front and Back-Fences

Virtual fencing contains and controls grazing cattle using sensory cues rather than physical fences. The technology comprises a neckband-mounted device that delivers an audio cue when the animal nears a virtual boundary that has been set via global positioning system, followed by an electrical stimulus if it walks beyond the boundary. Virtual fencing has successfully been used to intensively graze cattle using a simple virtual front-fence, but a more complex intensive grazing system comprising moving virtual front and back-fences has not been assessed. We studied the effectiveness of virtual fencing technology to contain groups of Angus heifers within grazing cells defined by semi-permanent electric side-fences and virtual front and back-fences, compared to groups of heifers contained in cells defined only by electric fencing. Four groups of 10 Angus heifers were randomly allocated to a “control” (grazed with a conventional electric front and back-fence, n = 2 groups) or “virtual fence” treatment (grazed with a virtual front and back-fence, n = 2 groups). The groups of heifers grazed four adjacent experimental paddocks that were established using TechnoGrazing™ infrastructure. An estimated 9.5 kg pasture DM/heifer.day was offered in each of three 3 day allocations (9 day study period). Data collected include cues delivered by the neckbands, time beyond the virtual boundaries, pasture consumption for each allocation and heifer live weight changes over the study period. The virtual front and back-fences successfully contained one group of heifers in their grazing cell, but the second group of heifers spent an increasing amount of time in the exclusion zone during the second and third allocations and consequently received an increasing number of audio and electrical stimuli. There were no effects of electric or virtual-fence treatment on live weight change or pasture utilization. By grazing heifers in adjacent paddocks our experimental design may have produced a motivation for some heifers to cross the virtual boundary to regain close contact with familiar conspecifics. Despite this, valuable learnings were gained from this study. Most notably, virtual fencing should not be used to manage cattle that have close visual contact to other mobs. We conclude that the successful application of virtual fencing technology needs to accommodate the natural behaviors of cattle.