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The objective of this study was to compare pre- and postweaning growth performance, carcass characteristics, and meat quality attributes of calves that did not receive an implant or were implanted early or late in the nursing period. Crossbred steer calves (n = 135) were stratified by birth date and birth weight and randomly assigned to the following implant treatments: control (CON; no preweaning implant), 58 d (EARLY; 36 mg zeranol, administered at an average of 58 ± 13 d of age), and 121 d (LATE; 36 mg zeranol, administered at an average 121 ± 13 d of age). After weaning, steers were blocked by initial feed yard BW to 15 pens (5 pens/treatment and 9 steers/pen). All steers were implanted on d 21 after arrival at the feed yard and again on d 108 of finishing. Steer BW and ultrasound assessment of rib eye area (uREA), rib fat thickness (uRFT), and percent intramuscular fat (uIMF) were collected when implants were administered, at weaning, and on harvest day. Carcass measurements included HCW, rib eye area (REA), 12th-rib fat thickness (FT), and marbling score. Objective color (L*, a*, and b*) was recorded, and a 3.8-cm strip loin section was removed from both sides of each carcass and portioned into 2.54-cm steaks that were aged for 3 or 14 d for analysis of cook loss and Warner-Bratzler shear force (WBSF). The remaining portion of each sample was used for analysis of moisture and crude fat. Steer BW, ADG, and G:F did not differ among treatments (P > 0.05). Steers implanted in the EARLY treatment had a greater (P < 0.05) cumulative DMI than CON but were not different from steers implanted in the LATE treatment. Ultrasound REA and uRFT (averaged across all collection days) did not differ (P > 0.05); however, steers on the CON treatment had a greater (P ≤ 0.05) percent uIMF than EARLY implanted steers, whereas steers receiving the LATE implant were intermediate and not different from the other treatments. Hot carcass weight, REA, FT, USDA yield grade, marbling score, and objective color did not differ (P > 0.05) among treatments. The proportion of steers in each USDA yield and quality grade was similar (P > 0.05) among treatments, and no differences were detected for total carcass value or price per 45.4 kg (hundredweight; P > 0.05). Treatment did not influence (P > 0.05) percent cook loss, crude fat, moisture, or WBSF. In conclusion, administering a nursing implant, regardless of timing, did not influence live performance, carcass characteristics, or meat quality of steers fed in this study. [ABSTRACT FROM AUTHOR]

Nutrition models are important in predicting animal growth; however, little research has focused on nursing calf performance submodels. This project's objective was to determine the accuracy and precision of two equations to compute nursing calves' feed intake. Data were collected on 394 nursing calves from 4 sets of cows (years 1953, 1959, 1964, 1974) of various breeds in which monthly milk yield and butterfat content, individual calf feed intake, and birth and weaning weights were measured during their first three lactations. Cows were milked at 14-d intervals to determine milk yield. The calf feed intake equations used to predict observed feed intake were Equation 9.1 (TED06; Tedeschi et al., 2006, In "Nutrient Digestion and Utilization in Farm Animals: Modeling Approaches") and Equation 25 (TED09; Tedeschi and Fox, 2009, J. Anim. Sci. 87:3380). Peak milk was estimated from lactation yield using the NASEM (2016) milk yield equation. The average (SD) peak milk, calf ME intake (MEI) over a 240-day preweaning period, and weaning weight were 10.84 (5.64) kg/d, 1,286 (328.71) Mcal of ME, and 280.93 (46.70) kg, respectively. When compared to the observed calf feed intake, TED06 and TED09 had Pearson correlation coefficients of 0.19 and 0.59, respectively. The MEI mean biases were -355.3 and 190.7 Mcal of for TED06 and TED09, respectively, indicating a 27.6% over prediction and 14.8% under prediction, respectively. The RMSE and R2 from linear regression of observed on predicted values of calf MEI were 308.7 Mcal and 0.0365 for TED06, and 253.2 Mcal and 0.3514 for TED09, respectively. In conclusion, neither equation adequately predicted calf feed intake, but the TED09 equation was more accurate and precise than the TED06 equation. Further research is needed to enhance our understanding of factors affecting feed intake of nursing calves to develop better prediction equations. [ABSTRACT FROM AUTHOR]

Lactobacillus and Bacillus probiotics may serve as an alternative to antibiotics in milk replacer for preruminant calves by altering gastrointestinal microflora to prevent the proliferation of harmful bacteria. However, there are limited studies evaluating their impact on calf growth and efficiency. The objective of this trial was to discover the impact of probiotic-containing milk replacer on pre-ruminating calf growth performance. A total of 44 pre-ruminant calves (50% Angus/50% Holstein, average weight 39.3 kg + 7.5 kg) were fed milk replacer with either no probiotic or 1.25x10-9 colony forming units/head/day of a probiotic blending containing Lactobacillus and two different Bacillus species (Church & Dwight Animal Nutrition (Princeton, NJ). Calves were blocked by age and randomly assigned within block to one of two treatments in a randomized complete block design. Calf was the experimental unit, with 22 calves per treatment. Calf weight and hip height was measured on d 0 and 30 to calculate average daily gain (ADG) and average growth per day. Calves were offered 1.36 kg milk replacer [15% dry matter (DM)] twice daily and up to 0.5 kg starter feed (88% DM) once daily. Refusals were recorded to calculate average daily intake and gain to feed ratio (G:F). Initial weight differed (P = 0.020) between treatments, and was therefore used as a covariate in all response criteria. Calves fed milk replacer with probiotic had greater (P < 0.05) ADG (0.53 vs. 0.42 kg/d, respectively) and G:F (0.50 vs. 0.41, respectively) than those fed the control. There was no evidence (P >0.05) that probiotic inclusion impacted hip height on d 30 or daily intake. In summary, Lactobacillus and Bacillus probiotic inclusion in milk replacer improved calf growth performance without impacting intake. Subsequent research is warranted to elucidate mode of action and evaluate impact relative to an antibiotic-containing positive control. [ABSTRACT FROM AUTHOR]