John B. Hall, Maggie R. Bloomsburg, and Sandra A. Goddard
Nancy M. Cummings Research, Extension and Education Center, University of Idaho, Carmen, ID 83462, USA
Department of Animal, Veterinary, and Food Science, University of Idaho, Moscow, ID 83844, USA
INTRODUCTION
Development of replacement heifers is a critical and expensive enterprise of the cow-calf operation. Nutrition during the postweaning development phase will impact heifer reproductive development as well as direct costs. Addition of ionophores in replacement heifer diets improve average daily gain (ADG) and may decrease age of puberty. However, the use of ionophores is not allowed in natural and organic programs.
In a previous study, Excell™ a lactobacillus fermentation product from Pacer Technology, Inc. showed increased average daily gain (ADG) and dry matter intake (DMI) compared to steers supplemented with Monensin. Therefore, an experiment was designed to compare supplementation of Excell™ to Monensin on pre-breeding growth, DMI, feed efficiency, and pregnancy rate in confinement fed heifers. The hypothesis was that Excell™ supplementation would produce results similar to Monensin and offer an alternative to ionophores in heifer diets for all natural programs.
RESULTS
Across all analyses,there were no significant differences (P > 0.50) for preweaning grazing location or backgrounding regime,or their interactions with feed additive. Figure 1).
Overall ADG was similar (P < 0.99) between MON and Excell™ heifers averaging 0.9 ± 0.1 kg/d and body weights were similar (P = 0.169) for heifers receiving MON or Excell™ at all weighing events.
Animals and Experimental Design
162 crossbred replacement beef heifers were stratified by age and weight, and randomly assigned to receive diets containing either Monensin (MON; 200 mg animal; n = 81) or Excell™ (5 mL animal n = 81) feed additive.
All heifers were fed in a Grow Safe System with a 14-d warm-up period followed by a 98-d experimental period.
Pre-breeding body weights were not different(P > 0.28) between MON and Excell™ heifers (Figure 2).
The percentage of heifers expressing estrus after synchronization was increased (P < 0.01) in MON compared to Excell™. There was a tendency for more MON heifers to conceive to AI than Excell™ heifers (P < 0.07). However, pregnancy rates were similar at 60 d (P = 0.33) and 100 d (P = 0.66) after AI for heifers consuming MON or Excell™, and across feed additives averaged 80.4% and 90.5% for 60 and 100 d, respectively.
DISCUSSION
This study compared growth, feed intake, and reproductive responses of peripubertal heifers to a feed additive which improves growth and feed efficiency, Monensin, to heifers receiving the prebiotic, Excell™.
Overall, the prebiotic-treated heifers responded similarly to the ionophore-supplemented heifers.
In summary, the use of Excell™, a L. acidophilus fermentation product as a prebiotic may be a viable substitute for ionophores in replacement heifer diets. Based on the conditions of the present study, growth, and reproductive responses to this prebiotic appears to be similar to Monensin in diets containing sufficient energy to support recommended growth rates in heifers.
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