Growth Performance of Nursery Pigs in the Immediate Post-Weaning Period According to Different Vaccination Strategies

The objective of this study was to evaluate the growth performance of nursery pigs immediately after weaning based on different vaccination strategies. A total of 300 weaned pigs (DNA 241 × 600, DNA Genetics, Columbus, NE) with an initial body weight (BW) of 14.0 lb and approximately 21 d of age were used in this trial. Pigs were allotted to pens in a completely randomized design with 5 pigs per pen and a total of 60 pens. All pigs received one dose of a commercial combination vaccine for Porcine Circovirus Type 2 and Mycoplasma hyopneumoniae at approximately d 7 of age. At weaning, 30 of the 60 pens of pigs were randomly selected to receive the second dose of the vaccine. Pigs were fed common diets based on corn and soybean meal. Pigs were weighed and feed disappearance was recorded on d 0, 2, 4, 6, and 8 to determine average daily gain (ADG), average daily feed intake (ADFI), and feed-to-gain ratio (F/G). The results of this study demonstrate no evidence (P > 0.05) of difference for the effect of vaccination or interaction between vaccination and day on growth performance after weaning. However, there was evidence (P < 0.0001) for an effect of day on BW, ADG, ADFI, and F/G. In the first 2 d after weaning, pigs consumed nearly no feed and, consequently, lost weight (P < 0.0001). In the following days, pigs gradually increased feed intake and gained weight from d 2 to 4 (P < 0.0001), but lost weight from d 4 to 6 (P < 0.0001). A significant increase (P < 0.0001) in feed intake and weight gain was observed from d 6 to 8 after weaning, resulting in an increase in BW. In conclusion, weanling pigs have a slow start on feed and low growth performance during the first week after weaning, but rapidly increase feed intake and weight gain toward the end during the end of the first week of nursery. Vaccination at the moment of weaning was not an aggravating factor to post-weaning growth performance in this study.


Summary
The objective of this study was to evaluate the growth performance of nursery pigs immediately after weaning based on different vaccination strategies. A total of 300 weaned pigs (DNA 241 × 600, DNA Genetics, Columbus, NE) with an initial body weight (BW) of 14.0 lb and approximately 21 d of age were used in this trial. Pigs were allotted to pens in a completely randomized design with 5 pigs per pen and a total of 60 pens. All pigs received one dose of a commercial combination vaccine for Porcine Circovirus Type 2 and Mycoplasma hyopneumoniae at approximately d 7 of age. At weaning, 30 of the 60 pens of pigs were randomly selected to receive the second dose of the vaccine. Pigs were fed common diets based on corn and soybean meal. Pigs were weighed and feed disappearance was recorded on d 0, 2, 4, 6, and 8 to determine average daily gain (ADG), average daily feed intake (ADFI), and feed-to-gain ratio (F/G). The results of this study demonstrate no evidence (P > 0.05) of difference for the effect of vaccination or interaction between vaccination and day on growth performance after weaning. However, there was evidence (P < 0.0001) for an effect of day on BW, ADG, ADFI, and F/G. In the first 2 d after weaning, pigs consumed nearly no feed and, consequently, lost weight (P < 0.0001). In the following days, pigs gradually increased feed intake and gained weight from d 2 to 4 (P < 0.0001), but lost weight from d 4 to 6 (P < 0.0001). A significant increase (P < 0.0001) in feed intake and weight gain was observed from

Introduction
Weaning imposes abrupt and simultaneous stressors on pigs, including social, environmental, physiological, and nutritional factors. Moreover, management factors contrib- ute to an impact on post-weaning performance, in particular vaccination protocols. 2 As a result, the early weaning period is typically associated with low feed consumption, poor growth performance, an increase in the incidence of diarrhea, and intestinal villous atrophy. 3 This post-weaning 'growth check' is considered a major limitation to production efficiency. Therefore, it is important to characterize the growth performance of newly-weaned pigs to further develop strategies to minimize the negative impact of weaning. The objective of this study was to evaluate growth performance of weaned pigs, with or without vaccination at weaning, in the immediate post-weaning period.

Procedures
The Kansas State University Institutional Care and Use Committee approved the protocol used in this experiment. The experiment was conducted at the Kansas State Swine Teaching and Research Center in Manhattan, KS. Nursery pigs were housed in 4-× 4-ft pens with a 4-hole dry self-feeder and one nipple waterer to provide ad libitum access to feed and water. Diets were manufactured at the Kansas State University O.H. Kruse Feed Technology Innovation Center in Manhattan, KS.
A total of 300 weaned pigs (DNA 241 × 600, DNA Genetics, Columbus, NE) with an initial BW of 14.0 lb were used in a 20-d nursery trial. Pigs were weaned at approximately 21 d of age and allotted to pens in a completely randomized design based on BW at weaning. There were 5 pigs per pen and a total of 60 pens.
All pigs received one dose of a commercially available combination vaccine for Porcine Circovirus Type 2 and Mycoplasma hyopneumoniae (Circumvent G2, Merck Animal Health, Summit, NJ) at approximately 7 d of age. To determine whether the second dose of the vaccine affected growth performance after weaning, 30 of the 60 pens of pigs were randomly selected to receive the second dose of the vaccine on the day of weaning.
Pigs were fed common diets based on corn and soybean meal in two dietary phases: Phase 1 was fed from d 0 to 8 in pellet form; and Phase 2 was fed from d 8 to 20 in meal form (Table 1). Pigs were weighed and feed disappearance was recorded at the same time on d 0, 2, 4, 6, and 8 to determine ADG, ADFI, and F/G during Phase 1. Pigs were also weighed on d 20 to determine BW at the end of Phase 2.
Data were analyzed using a linear mixed model testing for fixed effects of day, vaccination, and interactions. Day was analyzed as repeated measures within pen. Statistical models were fitted using the GLIMMIX procedure of SAS version 9.4 (SAS Institute Inc., Cary, NC). Pen was the experimental unit for all analysis. Results were considered significant at P ≤ 0.05.

Results and Discussion
There was no evidence (P > 0.05) of difference for the effect of vaccination at weaning or interaction between vaccination at weaning and day on growth performance after weaning (Table 2). However, there was an effect (P < 0.0001) of day on BW, ADG, ADFI, and F/G during the period after weaning (Table 3, Figure 1). In the first 2 d after weaning, pigs consumed nearly no feed and, consequently, lost weight (P < 0.0001). In the following days, pigs gradually increased feed intake and gained weight from d 2 to 4 (P < 0.0001), but then lost weight from d 4 to 6 (P < 0.0001). A pronounced increase (P < 0.0001) in feed intake and weight gain was observed from d 6 to 8 after weaning, resulting in an increase in BW. In Phase 2, there was no evidence for difference (P > 0.05) in growth performance according to vaccination strategy at weaning, with mean ADG of 0.56 lb from d 8 to 20 and mean BW of 21.1 lb on d 20.
The early period following weaning is clearly a period of challenge for weaned pigs. The effects of vaccination at the moment of weaning would be considered as an aggravating factor in the post-weaning, but in this study the vaccine utilized exerted no detrimental effect on growth performance. Both vaccinated and non-vaccinated pigs increased their weaning weight by only 0.3 lb during an 8-d period into the nursery. As demonstrated in this study, pigs consumed nearly no feed during the first week after weaning and, consequently, lost 0.5 lb of BW in this period. Interestingly, toward the end of the first week of being in the nursery, pigs rapidly increased feed intake and weight gain. Moreover, pigs seemed to have adapted to the nursery diet and environment and presented adequate growth by d 20 after weaning.
As reviewed by Dong and Pluske, 4 the factors affecting feed intake after weaning are many, including nutritional factors. Dietary approaches to improve feed consumption or minimize anorexia in the early period after weaning include using good quality ingredients, supplying the nutrient requirements, providing highly digestible diets, and improving palatability. 3 Finding means to enhance feed intake in the newly-weaned pig is of utmost importance to improve growth performance, reduce post-weaning diarrhea, and prevent intestinal villous atrophy.
In conclusion, weanling pigs have a slow start on feed and low growth performance during the first week after weaning, but rapidly increase feed intake and weight gain towards the end of the first week in the nursery. Vaccination at the moment of weaning was not an aggravating factor to post-weaning growth performance in this study.   A total of 300 weaned pigs (DNA 241 × 600, DNA Genetics, Columbus, NE) with an initial BW of 14.0 lb and 21 d of age were used in a nursery trial. Pigs were allotted to pens in a completely randomized design with 5 pigs per pen and a total of 60 pens.

2
There was no evidence for effect (P > 0.05) of vaccination or interaction between vaccination and day. There was an effect (P < 0.0001) of day on average daily gain (ADG), average daily feed intake (ADFI), and feed-to-gain ratio (F/G). Different superscripts indicate significant difference (P < 0.0001) within a row.