Effect on Nursery Growth Performance and Health Status of an Antibiotic-Free Feeding Program, with or without Polyclonal Egg Igy Antibodies As Compared to a Program with Antibiotics

This study evaluated the effects on pig performance of a feeding program developed for antibiotic free (ABF) production (including acidifiers, enzymes, probiotics, and prebiotics) with or without polyclonal IgY egg antibodies (PEAb), compared to feeding that same program with an antibiotic. A total of 707 pigs (PIC 359; BW=5.8 kg) were allocated randomly to three dietary treatments: 1) positive control with 73 g/ton avilamycin (POS); 2) negative control without antibiotics nor PEAb (NEG); and 3) NEG with 1.5% PEAb (ABF+). There were 8 replications/treatment and 28-32 pigs/pen. Pigs received the dietary treatments on d 0-21 and a common diet on d 21-42. Pen weights and feed disappearance were determined on d 0, 21, and 42 to calculate BW, ADG, ADFI, and G:F. On select days, fecal score/pen (1=firm; 2=soft; 3=very soft, spreads readily; 4=watery) was recorded. Morbidity and mortality were recorded. Data were analyzed as randomized complete block design using GLM model in Minitab. Data were considered significant at P<0.05 using Fisher’s exact test. During d 0-21, NEG pigs had lower (P=0.006) ADG (g/d; 226 vs. 261 and 246, respectively) due to reduced (P=0.016) ADFI (g/d; 300 vs 327 and 326, respectively) compared to POS or ABF+ pigs. No differences observed (P=0.282) for G:F. By d 42, POS pigs were the heaviest with NEG pigs being the lightest and ABF+ pigs being intermediate. Overall, NEG pigs had lower ADG compared to ABF+ pigs while pigs fed ABF+ had lower ADG than POS pigs. POS and ABF+ pigs had a higher ADFI in contrast to NEG pigs. Pigs fed POS and ABF+ had higher G:F than the NEG pigs. There were no statistical differences in morbidity or mortality (P≥0.235), but ABF+ was numerically lower than POS and NEG. No stool differences (P≥0.393) were observed except on d 41 when pigs fed NEG tended to have looser stools compared to POS pigs while ABF+ pigs were intermediate. In conclusion, the use of PEAb in an ABF program improved performance compared to an ABF program without PEAb, but was lower than the POS.

Table 1. Growth and health performance (overall)

	POS	NEG	ABF+	SEM	P-value
BW (d 42), kg	21.6a	19.3c	21.0b	0.6	<0.001
ADG, g	377a	323c	359b	13	<0.001
ADFI, g	535a	485b	535a	20	<0.001
G:F	0.704a	0.662b	0.671a	0.015	<0.001
Fecal score (d 41)	2.0y	2.2z	2.1y,z	0.2	0.088
Mortality %	2.58	2.87	0.78	2.65	0.267