ABSTRACT
This experiment evaluated the effects of supplementing narasin during late-gestation and lactation on productive and physiological responses of Bos indicus beef heifers and their offspring. Pregnant, nulliparous Nelore heifers (N = 88) that conceived under the same fixed-time artificial insemination protocol and to the same sire were used. Heifers were ranked by maternal ability genomic score, body weight (BW) and body condition score (BCS) and allocated to 44 drylot pens (2 heifers per pen; 10 × 25 m). Pens were ranked by these traits and alternatively assigned to receive (NAR) or not (CON) 0.260 mg of narasin/kg of heifer BW daily (Elanco Saúde Animal, São Paulo, Brazil). Narasin was mixed into a supplement offered at 0.30% of heifer BW from day 0 until heifers weaned their calves (day 316), whereas CON heifers received the same supplement without narasin addition. Heifers received Urochloa brizantha hay and water for ad libitum consumption (days 0 to 316) and calved between days 97 to 112 of the experiment. After calving, heifers and offspring had access to hay and supplement; hence, supplements and narasin were offered according to heifer + calf BW beginning on day 162. No treatment differences were detected (P ≥ 0.18) for heifer BW and BCS during the experiment, although BW loss from day 0 to calving was less (P = 0.04) in NAR compared to CON heifers. Hay intake during the experiment did not differ (P = 0.79) between treatments. Serum IGF-I concentrations were greater (P = 0.05) for NAR heifers on day 60 of the experiment and did not differ (P ≥ 0.28) between treatments 24 h and 30 d after calving (treatment × day interaction; P = 0.04). No treatment effects were detected (P ≥ 0.58) for calf birth BW. Serum concentrations of total protein 24 h after birth were greater (P = 0.04) in calves from NAR compared with CON heifers, and a tendency (P = 0.10) for a similar outcome was noted for serum IgG concentrations. Diarrhea incidence did not differ (P = 0.16) between treatments, although the number of total diarrhea cases per calf were greater (P = 0.03) in the CON offspring. Growth rate of calves from NAR heifers tended (P = 0.08) to be greater, resulting in heavier calves at weaning (P ≤ 0.04) compared with CON offspring. Collectively, these outcomes indicate narasin supplementation to beef heifers as a nutritional alternative to improve cow-calf productivity via developmental programming effects during gestation, as well as direct consumption by their nursing offspring.
ABSTRACT
Heat stress negatively impacts production, reproduction, and health of ruminants and strategies to alleviate these losses are warranted. Therefore, four experiments evaluated different cooling strategies on vaginal temperature (VT) of Holstein × Gir cows. Experiment 1 compared different amounts of water (2- or 4-L) over a 1-hour period from 1000 to 1100 h and 1600 to 1700 h. Experiment 2 evaluated the effects of sprinkling duration (in hours; 1- or 2-H), whereas Experiment 3 evaluated the effects of water amount (4- or 8-L) applied for 1- or 2-H. Lastly, the effects of a cooling strategy on specific hours of the day, starting at either 0700 (T-1) or 1100 h (T-2; Experiment 4), were evaluated. In all experiments, 12 Holstein × Gir cows were used in a 2 × 2 Latin Square Design containing two periods of 6 days each. Temperature and humidity index (THI) were recorded hourly and VT was recorded every 10-min throughout the experiments. As expected, an hour effect was observed for THI (P < 0.0001), which peaked early in the afternoon. In Experiment 1, a treatment × hour interaction was observed (P < 0.0001) for VT, as animals assigned to receive 4-L had a reduced VT at 1100, 1600, 1700, and 2300 h (P ≤ 0.03). During the cooling applications, cows receiving 4-L for 1 h had a reduced VT from 60 to 150 min (P ≤ 0.04). In Experiment 2, a treatment × hour interaction was observed (P < 0.0001) for VT, as animals assigned to receive 4-L of water for 2-H had a reduced VT at 1200 h (P = 0.05). Moreover, during the cooling process, VT was reduced for 2-H cows from 140 to 170 min after the beginning of the cooling process (P ≤ 0.05). In Experiment 3, animals assigned to receive 4-L + 2H had a reduced VT at 1200, 1700, 1800, and 1900 h (P < 0.001). A treatment × hour interaction was observed (P < 0.0001), as VT was reduced for 4-L + 2-H cows from 130 to 180 min after the beginning of the cooling process (P ≤ 0.05). In Experiment 4, by the time when the first cooling cycle of T-1 was applied (0700 h), T-1 cows consistently had (P ≤ 0.05) a reduced VT up to the hottest hours and greatest THI of the day (1400 and 1500 h). This pattern was maintained until the end of the last cooling cycle, whereas T-2 cows had a reduced VT. In summary, 4 L of water over a 5-min cycle for a period of 2 hours twice a day maintained VT of Holstein × Gir cows at lower levels. Moreover, the hour at which the first cooling cycle starts also should be considered when evaluating the efficacy of a cooling strategy for an entire day.
ABSTRACT
The objectives of the study were to evaluate the growth, physiological parameters, and liver trace mineral status of beef heifers provided low-quality warm-season forage and different forms (meal vs. block) of trace mineral-fortified supplementation. One hundred yearling Nellore heifers were blocked by initial body weight (BW) (184 ± 2.5 kg) and randomly assigned into 1 of 20 drylot pens (5 heifers/pen). Treatments were randomly assigned to pens (5 pens/treatment) and consisted of heifers receiving: 1) a loose meal trace mineral supplement (TM; De Heus Animal Nutrition Industry); 2) free choice access to a low-moisture, cooked sugarcane molasses-based protein block (LMB); 3) isocaloric and isonitrogenous, loose meal protein supplement pair-fed to LMB supplement dry matter (DM) intake (PSPF); and (4) loose meal protein supplement offered at 0.2% of BW (PS). Supplements were formulated to achieve same daily intake of supplemental trace mineral among treatments. Hence, TM supplement was offered at 66.6% of the supplement DMI of LMB heifers. Heifers were offered free choice access to water and ground brachiaria (Brachiaria brizantha) hay from day 0 to 45. Overall average daily gain from day 0 to 45 was the least for TM heifers (P ≤ 0.05) and did not differ among LMB, PSPF, and PS heifers (P ≥ 0.60). Daily hay DMI did not differ among treatments (P ≥ 0.63). Total intake of DM and TDN were least for TM heifers (P ≤ 0.03) and did not differ (P ≥ 0.66) among LMB, PSPF, and PS heifers. Total supplemental intake of crude protein (CP) and rumen degradable protein (RDP) and total intake of CP and RDP (supplement + hay) were least for TM and greatest for PS heifers (P ≤ 0.05), and intermediate for LMB and PSPF heifers (P ≥ 0.70). Effects of treatment × day and treatment were not detected (P ≥ 0.61) for plasma concentrations of insulin-like growth factor 1 (IGF-1), and non-esterified fatty acids (NEFA). Effects of treatment were detected for plasma concentrations of PUN (P = 0.005) and tended to be detected for plasma concentrations of glucose (P = 0.08), which were least for TM heifers (P ≤ 0.03) and did not differ (P ≥ 0.17) among LMB, PSPF, and PS heifers. Trace mineral intake and liver concentrations of all trace minerals did not differ (P ≥ 0.13) among treatments. Hence, the use of LMB supplementation resulted in positive effects on growth without impacting trace mineral status compared to a loose meal trace mineral salt, and similar growth performance and trace mineral status compared to a conventional protein supplementation offered at 0.2% of body weight.
