A meta-regression analysis to evaluate the effects of narasin on grow-finish pig performance.

Ionophores are feed additives that decrease gram-positive microbial populations by disrupting the ion transfer across cell membranes resulting in improved growth performance. Narasin (Skycis; Elanco Animal Health, Greenfield, IN) is an FDA-approved ionophore utilized for increased rate of weight gain and improved feed efficiency in growing-finishing pigs. A meta-regression analysis was conducted to evaluate the effects of added narasin in growing-finishing pig diets to predict its influence on average daily gain (ADG), feed efficiency (G:F), and carcass yield. A database was developed containing 21 technical reports, abstracts, and refereed papers from 2012 to 2021 representing 35 observations for growth performance data in studies ranging from 35 to 116 d in length (overall data). In addition, within these 35 observations, individual period data were evaluated (143 observations) using weekly, bi-weekly, or monthly performance intervals (period data). Regression model equations were developed, and predictor variables were assessed with a stepwise manual forward selection procedure. The ADG model using the overall data included ADG, ADFI, and G:F of the control group, added narasin dose, and narasin feeding duration categorized as longer or shorter than 65 d. Predictor variables included in the G:F model using overall data were ADG, ADFI, and G:F of the control group and added narasin dose. For carcass yield, the final model included ADFI and G:F of the control group, added narasin dose, and narasin feeding duration of longer than 65 d. In the period model for ADG, the predictors included ADG, ADFI, and G:F of the control group, added narasin dose, and average BW of the control group categorized into greater than or less than 105 kg. For period data for G:F, the model selected ADG, ADFI, and G:F of the control group and added narasin dose. Based on the results, the overall response to added narasin for ADG and G:F was quadratic and tended to decrease as ADG and G:F increased. A similar quadratic response was observed for the individual period data. In summary, using median values from the database for predictor variables, this meta-analysis demonstrated narasin would be expected to improve ADG between 1.06% and 1.65%, G:F between 0.71% and 1.71%, and carcass yield by 0.31% when fed continuously for longer than 65 d.

Effects of different antibiotic feeding programs on morbidity and mortality and growth performance of nursery pigs housed in a wean-to-finish facility.

The objective of this study was to evaluate the effects of two antibiotic feeding programs in comparison to nonmedicated controls on the incidence of morbidity and mortality and growth performance of nursery pigs in a commercial setting. The study used 2,250 crossbred pigs in a randomized complete block design (blocking factor = start date). There were two dietary phases with three treatments in each phase: 1) nonmedicated controls vs. 2) 39 mg/kg (35 g/ton) tiamulin + 441 mg/kg (400 g/ton) chlortetracycline fed for 14 d (TIACTC) followed by 39 mg/kg (35 g/ton) tiamulin fed for 21 d (TIA) vs. 3) 28 mg/kg (25 g/ton) carbadox + 441 mg/kg (400 g/ton) oxytetracycline fed for 14 d (CAROTC) followed by 55 mg/kg (50 g/ton) carbadox fed for 21 d (CAR). Necropsy results from mortalities during the study confirmed the presence of pathogens including Pasteurella multocida and Escherichia coli, as well as Mycoplasma hyopneumoniae, Haemophilus parasuis, and Streptococcus suis. The study was carried out for a fixed time of 35 d from 6.7 ± 0.57 to 25.5 ± 2.23 kg BW. Pigs were housed in single-sex pens of 25 in a commercial wean-to-finish facility and there were 30 replicates of each treatment. All pigs were weighed as a group (i.e., pen) on days 0 (start), 14, and 35 (end) of study. Pigs had ad libitum access to feed and water throughout the study period; all feed additions to the feeder were recorded. There was no effect (P > 0.05) of antibiotic feeding program on the incidence of morbidity and mortality at any point during the study. During phase 1, TIACTC- and CAROTC-fed pigs were heavier (P < 0.05) at day 14 and had greater (P < 0.05) ADG (8.3% and 5.6% for TIACTC and CAROTC, respectively) and ADFI (4.3% and 6.5%, respectively) than controls. Pigs fed TIACTC in the first 14 d had greater (P < 0.05) G:F than the other treatments, which were similar for this measurement. In phase 2, feeding CAR resulted in greater (P < 0.05) ADG than controls, with pigs fed TIA being intermediate and different (P < 0.05) than the other treatments. Feeding antibiotics, regardless of treatment, resulted in greater (P < 0.05) ADFI than controls, but there were no differences in G:F. For the overall 35-d study period, feeding antibiotics resulted in greater (P < 0.05) ADG than controls (3.8% and 5.8%, respectively), but no difference (P > 0.05) between treatments for overall G:F. The results of this study confirm the advantage of feeding antibiotics on nursery pig growth.

Effects of two feeding periods of tiamulin fed in combination with chlortetracycline for control and treatment of swine respiratory and enteric disease and subsequent growth performance of growing-finishing pigs.

The objective of this study was to evaluate the effects of two dietary feeding periods of tiamulin in combination with chlortetracycline for the control and treatment of swine respiratory and enteric disease and subsequent growth performance. The study used 1,151 commercial crossbred barrows and gilts in a randomized complete block design. Pigs were housed in single-sex groups of 25 at a floor space of 0.69 m2/pig. There were two dietary treatments: 1) nonmedicated controls and 2) 39 mg/kg tiamulin + 441 mg/kg chlortetracycline (TIACTC) fed from days 7 to 20 and again days 49 to 62. There were 23 pens per treatment group. Daily observations were made throughout the study, including the number of pigs in each pen coughing, with diarrhea, or showing signs of lameness as well as the number of pigs in each pen requiring individual therapy treatment for each symptom. Pigs were weighed as a group on days 0 (for allocation purposes), 7, 21, 49, 61, 89 (start of marketing), and at time of slaughter. Within pen, animals were selected by visual appraisal and sent for slaughter over 4 wk to a commercial slaughter facility where HCW was collected and used to calculate carcass yield. There was no difference (P > 0.05) between treatments for the incidence of morbidity or mortality. Pigs fed TIACTC tended to have less coughing observations (P = 0.10) and less diarrhea observations (P = 0.08) during the study period, and had less observations of lameness (P < 0.001) and required less treatments than nonmedicated controls (P < 0.001). For the overall study period, pigs fed TIACTC had greater (P < 0.05) total BW gain (43.3 kg greater/pen) and greater (P < 0.05) ADG and ADFI than controls. There was no effect (P > 0.05) of treatment on G:F. Overall, pigs fed TIACTC weighed 1.3 kg heavier (P < 0.05) at the start of marketing and completed the study with an overall BW advantage of 1.6 kg (P < 0.05) compared to controls. The difference between treatments for live BW increased with marketing group (1.0 kg in marketing group 1 and 3.3 kg in marketing group 4). Pigs fed TIACTC had greater (P < 0.05) HCW (1.0 kg) than controls; however, there was no difference (P > 0.05) between treatments for carcass yield. The results of this study suggest that feeding TIACTC was successful at controlling respiratory and enteric disease and, consequently, improved growth performance and carcass weight of grow-finish pigs.

Birth weight threshold for identifying piglets at risk for preweaning mortality.

Several studies have suggested there is a critical relationship between piglet birth weight and preweaning mortality. Thus, the objective of the current work was to identify a birth weight threshold value for preweaning mortality. Birth weight and survival data from two studies involving a combined total of 4,068 piglets from 394 litters on four commercial farms (three European, one U.S.) were compiled for a pooled, multistudy analysis. Overall preweaning mortality across the two studies was 12.2%. Key variables used in the analysis were piglet birth weight (measured within 24 h of birth) and corresponding survival outcome (dead or live) by weaning at 3-4 wk of age. A mixed effects logistic regression model was fit to estimate the relationship between preweaning mortality and birth weight. A random effect of study was included to account for overall differences in mortality between the two studies. A piecewise linear predictor was selected to best represent the drastic decrease in preweaning mortality found as birth weight increased in the range of 0.5-1.0 kg and the less extreme change in weight above 1.0 kg. The change point of the birth weight and preweaning mortality model was determined by comparing model fit based on maximizing the likelihood over the interval ranging from 0.5 to 2.3 kg birth weight. Results from the analysis showed a curvilinear relationship between birth weight and preweaning mortality where the birth weight change point value or threshold value was 1.11 kg. In the combined data set, 15.2% of pigs had birth weights ≤1.11 kg. This subpopulation of pigs had a 34.4% preweaning mortality rate and represented 43% of total preweaning mortalities. These findings imply interventions targeted at reducing the incidence of piglets with birth weights ≤1.11 kg have potential to improve piglet survivability. Additional research is needed to validate 1.11 kg as the birth weight threshold for increased risk of preweaning mortality.