Influence of feed efficiency classification on diet digestibility and growth performance of beef steers

Phenotypic and genetic parameters of circadian rhythms from core body temperature profiles and their relationships with beef steers' production efficiency profiles during successive winter feeding periods

This 2-year study evaluated differences in circadian parameters obtained from measures of core body temperatures using telemetric reticulo-rumen and rectal devices during two winter feeding regimes in western Canada. The study also estimated phenotypic correlations and genetic parameters associated with circadian parameters and other production traits in each feeding regime. Each year, 80 weaned steer calves (initial age: 209 ± 11 days; BW: 264 ± 20 kg) from the same cohort were tested over two successive regimes, Fall-Winter (FW) and Winter-Spring (WS) at Lanigan, Saskatchewan, Canada. The steers received forage-based rations in both regimes where the individual feed intake was measured with automatic feeding units. During the trial, the reticulo-rumen (RTMP) and rectal (RCT) temperatures were simultaneously measured every 5 min using telemetric devices. These were used to calculate the circadian parameters (Midline Estimating Statistic Of Rhythms, amplitude, and acrophase/peak time) for both temperature measures. Growth and efficiency performance traits were also determined for all steers. Each steer was assigned into inefficient, neutral, and efficient classes based on the SD of the residual feed intake (RFI), residual gain (RG), and residual intake and gain (RIG) within each year and feeding regime. Higher (p < 0.0003) RTMP and rectal temperature MESORs were observed in the Fall-Winter compared to the Winter-Spring regime. While the two test regimes were different (p < 0.05) for the majority of the RTMP or RCT temperature parameters, they did not differ (p > 0.10) with the production efficiency profiles. The heritability estimates were higher in FW (0.78 ± 0.18 vs. 0.56 ± 0.26) than WS (0.50 ± 0.18 vs. 0.47 ± 0.22) for the rumen and rectal MESORs, respectively. There were positive genetic correlations between the two regimes for the RTMP (0.69 ± 0.21) and RCT (0.32 ± 0.59). There was a negative correlation (p < 0.001) between body temperature and ambient temperature. The high heritability estimates and genetic correlations for rumen and rectal temperature parameters demonstrate their potential as beef genetic improvement tools of economic traits associated with the parameters. However, there are limited practical implications of using only the core-body temperature as a proxy for production efficiency traits for beef steers during winter.

Identification of Predictor Genes for Feed Efficiency in Beef Cattle by Applying Machine Learning Methods to Multi-Tissue Transcriptome Data

Machine learning (ML) methods have shown promising results in identifying genes when applied to large transcriptome datasets. However, no attempt has been made to compare the performance of combining different ML methods together in the prediction of high feed efficiency (HFE) and low feed efficiency (LFE) animals. In this study, using RNA sequencing data of five tissues (adrenal gland, hypothalamus, liver, skeletal muscle, and pituitary) from nine HFE and nine LFE Nellore bulls, we evaluated the prediction accuracies of five analytical methods in classifying FE animals. These included two conventional methods for differential gene expression (DGE) analysis (t-test and edgeR) as benchmarks, and three ML methods: Random Forests (RFs), Extreme Gradient Boosting (XGBoost), and combination of both RF and XGBoost (RX). Utility of a subset of candidate genes selected from each method for classification of FE animals was assessed by support vector machine (SVM). Among all methods, the smallest subsets of genes (117) identified by RX outperformed those chosen by t-test, edgeR, RF, or XGBoost in classification accuracy of animals. Gene co-expression network analysis confirmed the interactivity existing among these genes and their relevance within the network related to their prediction ranking based on ML. The results demonstrate a great potential for applying a combination of ML methods to large transcriptome datasets to identify biologically important genes for accurately classifying FE animals.

Effect of supplementing a Saccharomyces cerevisiae fermentation product during a preconditioning period prior to transit on receiving period performance, nutrient digestibility, and antioxidant defense by beef steers

Forty-eight newly weaned crossbred beef steers from a single-source were used to determine the effects of feeding a Saccharomyces cerevisiae fermentation product (SCFP; NaturSafe, Diamond V) on receiving period performance, nutrient digestibility, and antioxidant defense. Seven days after arrival, steers were stratified by BW (257 ± 18 kg), sorted into pens (n = 1 pen/treatment), and pens assigned to dietary treatments: SCFP at 0 (CON), 12 (SCFP12), 18 (SCFP18), or 0 g·steer^-1·d^-1 during preconditioning (PRE; days -19 to 0), then 18 g·steer^-1·d^-1 during receiving (REC; days 0 to 58; CON18). On day -1 BW and blood were collected, steers were loaded onto a semitruck and transported 1,748 km over 19 h. Upon return, steers were weighed, stratified by BW within treatment and sorted into pens with GrowSafe bunks (n = 12 steers/treatment). Steers were weighed on days -1, 0, 29, 30, 57, and 58. Blood was collected from all steers on days -1, 1, and 8 and liver biopsies were performed on all steers on days -20, -3, and 59. Titanium dioxide was included as an indigestible marker in the diet of all steers from days 14 through 29 to determine total tract nutrient digestibility. Data were analyzed as a completely randomized design using ProcMixed of SAS with the fixed effect of treatment. Steer was the experimental unit for REC period variables. Contrast statements compared the linear and quadratic effects of feeding SCFP throughout the trial (CON, SCFP12, and SCFP18) and the effect of supplementation at 18 g·steer^-1·d^-1 for the entire trial or starting in REC (SCFP18 vs. CON18). Steers fed SCFP12 exhibited the greatest ADG and G:F from days 0 to 30 (quadratic P ≤ 0.04). Total tract digestibility of NDF and ADF was linearly decreased by SCFP (linear P ≤ 0.03). On day -3, SCFP12-fed steers tended to have the greatest liver concentrations of total, oxidized, and reduced glutathione (quadratic P = 0.06). Red blood cell lysate Mn:total-superoxide dismutase activity was 16% greater 1 d posttransit compared with pretransit values (day P ≤ 0.01). Timing of SCFP supplementation (SCFP18 vs. CON18) did not affect any of the variables assessed herein (P ≥ 0.19). Supplementing SCFP at 12 g·steer^-1·d^-1 tended to affect antioxidant capacity prior to transit and improved early receiving period performance; however, overall receiving period performance was not affected by SCFP supplementation. Further research is necessary to determine the optimal dose and timing of SCFP supplementation for beef cattle.

Effects of replacing canola meal with camelina expeller on intake, total tract digestibility, and feeding behavior of beef heifers fed high-concentrate diets

To assess the effect of inclusion of camelina expeller in beef cattle diets, 24 Simmental heifers were used. Two experiments were carried out. In the first, two free-choice tests, one without and another with molasses, were conducted to know the preference of animals for a total mixed ration (TMR) made with a 90 to 10 concentrate to barley straw ratio, where canola meal (CM) or camelina expeller (CE) was used in the concentrate as a protein source. Heifers were allotted in four pens with two independent feedbunks, one for each diet. In the second, a replicated 4 × 4 Latin square design was used to assess the effects of the replacement of CM with CE on intake, digestibility, and sorting and animal behavior. The experiment was performed in four 28-d periods during which groups of three animals were allotted in each pen of 12.5 m². Diets were formulated with a 90 to 10 concentrate to barley straw ratio and fed as TMR, and they were designed to contain 1) CM as main protein source and 0% of CE (0CE), 2) 3% of CE replacing CM (3CE), 3) 6% of CE replacing CM (6CE), and 4) 9% of CE replacing CM (9CE). In the free-choice test without molasses, heifers showed a greater preference for CM than for CE (38.6 vs. 8.7 kg/d; P < 0.001). When molasses were added to the diet, the preference for CM was maintained (39.1 vs. 9.8 kg/d; P < 0.001). Dry matter (DM), organic matter (OM), crude protein (CP), and neutral detergent fiber (NDF) intake was unaffected by the level of replacement of CM by CE (P > 0.10), and there was no effect of this replacement on DM, OM, CP, and NDF apparent digestibility (P > 0.10). Intake of long particle size increased lineally as CE proportion increased (P = 0.015). In addition, extension of sorting behavior for long particle size tended to increase lineally (P = 0.07), and sorting against this particle size was detected in 0CE and 3CE, but not in 6CE and 9CE (P < 0.05). However, the results recorded for long particle size intake and for sorting behavior against these particles did not translate into more time spent ruminating in heifers fed diets with higher proportion of CE. In conclusion, when canola meal was replaced with camelina expeller at more than 14% of inclusion, heifers preferred the canola meal diet. However, replacing canola meal with camelina expeller up to 9% of inclusion in diets for beef cattle did not affect intake and digestibility but promoted a greater intake of long particle size of barley straw.

Effects of a Saccharomyces cerevisiae fermentation product in receiving diets of newly weaned beef steers. II. Digestibility and response to a vaccination challenge1

Thirty-six newly weaned, crossbred beef steers (323 ± 12 kg; SD) from a single-source were used in a 56-d study to examine the effects of a Saccharomyces cerevisiae fermentation product (SCFP; Original XPC, Diamond V, Cedar Rapids, IA) on total tract nutrient digestibility and response to a vaccination challenge. Twelve days after arrival, steers were blocked by body weight (BW) and randomly assigned to treatments: SCFP at 0 (CON), 14 (SCFP14), or 28 (SCFP28) g·steer-1·d-1. Steers were fed via bunks that measured individual intake and received ear tags (CowManager, Select Sires, Plain City, OH) that recorded rumination and activity. BWs were collected on days 1, 0, 14, 28, 42, 55, and 56. Titanium dioxide was fed as an indigestible marker to all steers from days 12 to 27, followed by consecutive day fecal samples, for determination of total tract nutrient digestibility. On day 34, steers received a Mannheimia haemolytica vaccination (One Shot, Zoetis, Kalamazoo, MI) to induce an acute phase protein response. Blood was collected from all steers on day 34 (prior to vaccination) and 3, 6, 9, 11, and 14 d post-vaccination. Data were analyzed using Proc Mixed of SAS (experimental unit = steer; n = 12 per treatment); the model included the fixed effect of treatment and block and the random effect of steer. Blood measures, ear tag, and dry matter intake (DMI) data for the 15-d vaccination period were analyzed as repeated measures. Contrast statements (CON vs. SCFP14; SCFP14 vs. SCFP28) were used to compare treatment means. Digestibility of dry matter (DM) and organic matter was greater for SCFP14 vs. SCFP28 (P ≤ 0.03). Steers fed SCFP14 exhibited greater crude protein digestibility compared with CON (P < 0.01). Steers fed SCFP14 exhibited greater DMI for 15 d post-vaccination (P = 0.02) and greater average daily gain from days 28 to 56 (P = 0.05) vs. SCFP28-fed steers. Post-vaccination, steers fed SCFP14 spent less time ruminating per kg of DM, neutral detergent fiber (NDF), and physically effective NDF consumed than CON or SCFP28 (P ≤ 0.07). Serum IL-8 and haptoglobin concentrations tended to be lesser for steers fed SCFP14 vs. SCFP28 (P ≤ 0.08). Ceruloplasmin concentrations were lesser on day 14 post-vaccination for steers fed SCFP14 vs. CON or SCFP28 (treatment × d; P = 0.004); there were no differences on other sampling days due to treatment. Although no overall performance benefit was noted, steers fed SCFP14 responded better to a vaccination challenge vs. SCFP28-fed steers.