RESUMO
Two experiments were designed to evaluate the effects of altering body condition score (BCS) and the profile of a fatty acid (FA) supplement on the metabolism of Bos indicus Nellore females. In experiment 1, 16 and 24 B. indicus heifers and nonlactating cows, respectively, were assigned to (1) maintenance diet (MNT-MNT; n = 10), (2) maintenance diet and BCS loss (MNT-LSS; n = 10), (3) maintenance diet supplemented with calcium salts of soybean oil for 30 d and BCS loss for 40 d (MNT+CFA-LSS; n = 10), and (4) maintenance diet for 30 d and BCS loss for 40 d with a diet containing calcium salts of soybean oil (MNT-LSS+CFA; n = 10). Following the BCS loss period, MNT-LSS, MNT+CFA-LSS, and MNT-LSS+CFA were fed a diet to promote the gain of BCS. In experiment 2, 40 Bos indicus nulliparous heifers were assigned to (1) maintenance diet (MNT-MNT; n = 10), (2) BCS loss followed by a BCS gain (LSS-REM; n = 10), (3) BCS loss followed by a BCS gain diet with CFA of palm oil (LSS-REM+PLM; n = 10), and (4) BCS loss followed by a BCS gain diet with CFA of soybean oil (LSS-REM+SOY; n = 10). Blood samples were obtained for serum haptoglobin and fecal samples for pH (experiment 2 only). In experiment 1, a treatment × day interaction was observed for BCS during the 60-d BCS loss and gain period. Animals assigned to MNT-MNT had a greater BCS than the other treatment groups on d 40 and 60 of the experiment, but no other differences were observed. Moreover, a treatment × day interaction was observed for serum haptoglobin, as on d 60, MNT-LSS had a greater mean serum haptoglobin concentration. In experiment 2, a treatment × day interaction was also observed for BCS. From d -4 to 0, LSS-REM and LSS-REM+SOY had a reduced BCS versus MNT-MNT, but also lower for LSS-REM versus MNT-MNT on d 1, and LSS-REM+PLM versus MNT-MNT on d -1 and 0. For serum haptoglobin, no treatment or treatment × day interaction was observed. A treatment × day interaction was observed for fecal pH. From d -10 to 0, MNT often had a lower fecal pH, but during realimentation, LSS-REM heifers had a reduced fecal pH on d 1, 4, and 10. In summary, we failed to demonstrate an increase in serum haptoglobin due to a BCS loss. Still, supplementation with calcium salts of FA alleviated the increase in haptoglobin and maintained fecal pH at more stable values during realimentation, regardless of the FA profile of the supplement.
RESUMO
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.