Different combinations of monensin and narasin on growth performance, carcass traits, and ruminal fermentation characteristics of finishing beef cattle.

The objective of this study was to evaluate the effects of different combinations of monensin and narasin on finishing cattle. In Exp. 1, 40 rumen-cannulated Nellore steers [initial body weight (BW) = 231 ± 3.64 kg] were blocked by initial BW and assigned to one of the five treatments as follows: Control (CON): no feed additive in the basal diet during the entire feeding period; Sodium monensin (MM) at 25 mg/kg dry matter (DM) during the entire feeding period [adaptation (days 1-21) and finishing (days 22-42) periods]; Narasin (NN) at 13 mg/kg DM during the entire feeding period (adaptation and finishing periods); Sodium monensin at 25 mg/kg DM during the adaptation period and narasin at 13 mg/kg DM during the finishing period (MN); and narasin at 13 mg/kg DM during the adaptation period and sodium monensin at 25 mg/kg DM during the finishing period (NM). Steers fed MM had lower dry matter intake (DMI) during the adaptation period compared to NM (P = 0.02) but not compared to CON, MM, MN, or NN (P ≥ 0.12). No differences in DMI were observed among the treatments during the finishing (P = 0.45) or the total feeding period (P = 0.15). Treatments did not affect the nutrient intake (P ≥ 0.51) or the total apparent digestibility of nutrients (P ≥ 0.22). In Exp. 2, 120 Nellore bulls (initial BW = 425 ± 5.4 kg) were used to evaluate the effects of the same treatments of Exp. 1 on growth performance and carcass characteristics of finishing feedlot cattle. Steers fed NM had greater DMI during the adaptation period compared to CON, MM, and MN (P ≤ 0.03), but no differences were observed between NM and NN (P = 0.66) or between CON, MM, and NN (P ≥ 0.11). No other differences between treatments were observed (P ≥ 12). Feeding narasin at 13 mg/kg DM during the adaptation period increases the DMI compared to monensin at 25 mg/kg DM, but the feed additives evaluated herein did not affect the total tract apparent digestibility of nutrients, growth performance, or carcass characteristics of finishing cattle.

Milk yield and composition from ewes fed diets containing narasin and their lambs' performance.

The changes promoted by feed additives in ruminal fermentation, especially increasing the availability of propionate, can improve the energy balance of an animal, which is of great importance in the lactation period. This trial aimed to evaluate the inclusion of narasin in the diet of lactating ewes on milk yield, composition, dry matter intake (DMI), and plasma metabolites of the ewes and growth rate of lambs. Thirty-two lactating ewes (59.0 ± 2.42 kg) were assigned to a randomized complete block design. The experimental diets contained 500 g/kg of dry matter (DM) of coast cross (Cynodon dactylon (L.) Pers) hay and 500 g/kg DM of concentrate, and the treatments were: N0-no narasin inclusion; N13-inclusion of 13 mg of narasin/kg DM. Once a week, from week 2 to 10 of lactation, ewes were separated from their lambs, injected with oxytocin, and milked mechanically to empty the udder. After 3 h, the milk production was recorded, using the same procedure, and sampled to evaluate the composition. The blood samples were taken weekly, 4 h after feeding. The average daily gain (ADG) and starter DMI of the lambs were evaluated weekly from week 2 to 12 of age. The inclusion of narasin did not affect (P = 0.93) DMI of ewes; however, it increased milk production (P < 0.01) and feed efficiency (P = 0.02; FE). Ewes fed N13 had a greater milk fat (P < 0.01), protein (P < 0.01), lactose (P = 0.04), and total solids production (P < 0.01). Narasin inclusion in ewe's diet increased plasma glucose concentration (P = 0.05) at weeks 8, 9 and 10; however, there was no effect on plasma urea concentration (P = 0.96). The lambs of N0 ewes had a greater starter DMI (P < 0.01) at weeks 7, 8, 9, and 10; however, the ADG and body weight at weaning and after weaning were similar between treatments (P > 0.05). The results showed that the inclusion of 13 mg of narasin/kg DM improved the milk production and FE of the ewes without altering the composition of the milk. The lower initial consumption of concentrate by N13 lambs before weaning was caused by the higher production of milk. The results obtained in the present study demonstrate the possible productive gain with the inclusion of narasin in diets for lactating ewes.

Decreasing from 9 to 7 days the permanence of progesterone inserts make possible their use up to 5 folds in suckled Nellore cows.

This study aimed to evaluate the effects of decreasing permanence period of progesterone (P4) inserts from 9 (9d) to 7 (7d) days in timed-AI (TAI) protocol, as well as their reuse on pregnancy per AI (P/AI) during 7d protocol. At the beginning of all protocols, cows received 2 mg of estradiol benzoate (EB) and a vaginal insert containing 1.9 g of P4. In the 7d protocol, the P4 insert was removed, and cows were given 25 mg of prostaglandin F2α, 0.6 mg of estradiol cypionate and 300 IU of eCG 7 days later. In the 9d protocol, the P4 insert was removed, and cows received the same hormones that were administrated in 7d protocol, however, they were applied on the 9th day of the protocol. In the experiment I, 302 suckled Nellore cows were undergone to 7d protocol, and AI was performed 10-14 h later after estrus detection. In the experiment II, 679 suckled Nellore cows were assigned to receive either 7d or 9d protocols. In the experiment III, 999 suckled Nellore cows were assigned to receive either a new P4 insert (CIDR1), or a P4 insert used previously for 7 (CIDR2), 14 (CIDR3), 21 (CIDR4) or 28 (CIDR5) days, and 227 Nellore heifers received a P4 insert used previously for 21 (CIDR4) or 35 (CIDR6) days during the 7d protocol. When 7d protocol was used, 45% of cows exhibited estrus 48 h after P4 removal. Thus, the AI was performed 55 h after P4 removal in experiments II and III when 7d protocol was used. There was no difference in estrus detection rate (72 vs 74%; P = 0.60), ovulation rate (80 vs 88%; P = 0.13) and P/AI (56 vs 54%; P = 0.49) between 7d and 9d protocols, respectively. In the 7d protocol, the P/AI was similar (P = 0.72) using a new P4 insert (47%), or a P4 insert used previously for 7 (48%), 14 (45%), 21 (54%), or 28 (49%) days in Nellore suckled cows. In addition, P/AI was similar (P = 0.15) in heifers that received a P4 insert used previously for 21 (52%), or 35 (61%) days during the 7d protocol. In conclusion, cows submitted to 7d or 9d protocols had similar reproductive performance, and the reuse of P4 inserts up to 6 folds (five in suckled cows plus one in heifers) did not affect reproductive performance of Nellore cattle in 7d protocol.

Effect of reproductive methods and GnRH administration on long-term protocol in Santa Ines ewes.

This study aimed to determine whether reproductive performance of ewes submitted to laparoscopic timed artificial insemination (TAI) would be similar to ante meridiem (AM)/post meridiem (PM) rule and assisted natural mating (NM), and whether GnRH may enhance the pregnancy rate in TAI. In experiment I, 191 non-lactating ewes were synchronized, then TAI was performed either 48 h after progesterone (P4) removal (TAI-48 h) or 12 h after estrus detection (AM/PM); moreover, some ewes were submitted to NM (NM) as control treatment. In experiment II, 247 non-lactating ewes were allocated in five treatments, a control (no-GnRH on protocol) and four treatments arranged in a factorial design 2 × 2. The factors were time and dose of GnRH: ewes that received either 10 µg (TAI-10 µg-36 h) or 25 µg of GnRH (TAI-25 µg-36 h) 36 h after P4 removal and ewes that received either 10 µg (TAI-10 µg-48 h) or 25 µg of GnRH (TAI-25 µg-48 h) at time of insemination, 48 h after P4 removal. In experiment I, pregnancy rate in TAI-48 h was lower (P = 0.03) than AM/PM and NM. Moreover, the probability of pregnancy in TAI-48 h was higher (P = 0.06) in ewes detected in estrus early. In experiment II, the use of GnRH in TAI protocols increased (P < 0.01) pregnancy rate at synchronization, and TAI-25 µ-48 h and TAI-10 µg-36 h treatments increased (P = 0.02) pregnancy rate compered to TAI-10 µg-48 h. We conclude that TAI decreased pregnancy rate compered to NM and AM/PM, which may be improved by GnRH use in TAI to synchronize ovulation.