Impacts of polyclonal antibody preparations from avian origin on nutrient digestibility and performance of backgrounding beef cattle.

This study evaluated the effects of feeding an avian-derived polyclonal antibody preparation ( PAP ; CAMAS, Inc.) against Streptococcus bovis , Fusobacterium necrophorum , and lipopolysaccharides ( LPS ; 40%, 35%, and 25% of the preparation, respectively) on growth performance (Exp. 1) and apparent total tract digestibility of nutrients (Exp. 2) of beef cattle consuming a backgrounding diet. In Exp. 1, Angus crossbred heifers ( n = 70; 360 ± 24 kg of initial body weight; BW ) and steers ( n = 20; 386 ± 24 kg of BW) were used in a generalized randomized block design. Heifers and steers were allocated to 1 of 18 concrete-surfaced pens (6 pens per treatment) to receive a common ad libitum diet (35% cottonseed hulls, 34% dry-rolled corn, and 20% corn gluten pellets; 15.9% crude protein on a dry matter [ DM ] basis, 1.58 Mcal/kg DM of net energy [ NE ] of maintenance, and 0.98 Mcal/kg DM of NE of gain) and 1 of the 3 treatments consisting of feeding 1 ( PAP1 ), 3 ( PAP3 ), or 0 g ( CON ) of PAP per day for 56 d. Feed intake was recorded daily and BW was obtained on days -1, 0, 14, 28, 42, 55, and 56 to assess average daily gain ( ADG ), dry matter intake ( DMI ), and gain:feed ( G:F ). Plasma concentrations of glucose and haptoglobin were measured on days 0, 14, 28, 42, and 56. In Exp. 2, 25 Angus crossbreed steers (390 ± 24 kg BW) were used in a completely randomized design to receive the same diet and treatments from Exp. 1 (CON: n = 8; PAP1: n = 9; and PAP3: n = 8). Following a 14-d adaptation to diets, feed and fecal samples were collected to determine apparent total tract nutrient digestibility. In Exp. 1, overall BW, DMI, ADG, G:F, and plasmatic measurements did not differ among treatments over the 56-d period ( P ≥ 0.16). However, from days 0 to 14, a quadratic effect was observed for ADG, in which cattle receiving PAP1 had greater ( P = 0.04) ADG compared with CON. In Exp. 2, no difference in DMI was observed ( P = 0.88), yet DM, organic matter, neutral and acid detergent fiber, and starch digestibility were least ( P ≤ 0.05) for PAP3, whereas digestibility of neutral detergent fiber was greatest ( P < 0.01) for PAP1. In summary, feeding 1 g/d of a PAP against S. bovis , F. necrophorum , and LPS improved growth performance in the first 14 d and increased fiber digestibility of beef cattle consuming a backgrounding diet. Further research is needed to understand the impaired responses on nutrient digestibility when greater doses are provided.