Patent Application: US-66266810-A

Abstract:
a method of identifying livestock animal subgroups of the same species , from a group of livestock animals of the same species wherein the subgroup has similar genetic predispositions for response to zilpaterol hydrochloride treatment with respect to marbling , hcw gain , rea size gain , ddmi , % ebf , and yg &# 39 ; s . the genetic potential of each animal to respond to zh treatment is established by determining the leptinarg25cys genotype and segregating individual animals into subgroups based upon the leptinarg25cys genotype .

Description:
in a trial completed at a private research facility in texas , usa ( cactus research , amarillo tex .) leptin genotype was assessed for potential interaction with zilpaterol hydrochloride ( zh ). the trial consisted of 4 , 279 animals and occurred from summer of 2008 and carried through to spring of 2009 . the trial was conducted as a randomized complete block design with approximately 90 animals being placed into pens based on leptin genotype and randomly assigned to drug treatment with pen being the experimental unit . treatment structure was a 3 × 2 factorial including three letting genotypes ( cc , ct and tt ) and two drug treatments ( zero control and drug treatment ). pens were blocked by time , specifically arrival date of the animal to the feedlot . each block was slaughtered on the same day , and the complete process replicated eight times resulting in eight blocks . below is a schematic summary of the trial design . upon arrival into the feedlot animals were individually weighed and back fat was measured using ultrasound . these measured were also taken 65 , days on feed , and then one week prior to zh treatment and 2 - 3 days prior to slaughter . all cattle were slaughtered and usda carcass data were measured . growth data were fitted to a non - linear growth model . fig1 illustrates a schematic summary of the trial design . 1 ) arrival 2 ) 65 days on feed 3 ) 1 week prior to zilpaterol initiation 4 ) 2 - 3 days prior to slaughter 8 total blocks , 6 treatment pens per block , and 4 , 179 head total ( avg initial wt = 875 lbs ) within blocks , all treatments were killed on the same day ( avg days on feed = 129 leptin genotype did affect some response variables independent of zh administration . for some response variables though , response to zh administration was dependent upon leptin genotype and interactions were observed . zh administration significantly interacted with leptin genotype ( p & lt ; 0 . 01 ). as measured by usda stamped quality grade categories , choice + prime , tt animals had the highest % choice + prime , ct animals were intermediate and cc animals had the lowest choice + prime without zh administration . in animals administered zh , cc were unaffected with respect to % choice + prime but tt and ct animals had significant reductions in % choice + prime . see fig4 . fig5 illustrates the interaction between leptin genotype and zh on marbling score . zh administration significantly interacted with leptin genotype ( p & lt ; 0 . 02 ) as measured by marbling score . cc &# 39 ; s administered zh had only a slight reduction in marbling score where as tt &# 39 ; s and ct &# 39 ; s administered zh had a much greater reduction in marbling score . see fig5 . fig6 . interaction between leptin genotype and zh on hcw gain . zh administration has a statistical tendency to interact with leptin genotype ( p = 0 . 14 ) with respect to hot carcass weight gain . response to zh administration varied by genotype with the tt &# 39 ; s having the lowest response to zh administration . cc &# 39 ; s and ct &# 39 ; s have the largest response to zh administration . there is a 3 . 4 kg ( 7 . 4 lb ) hcw response difference between cc and tt animals ( p & lt ; 0 . 10 ). see fig6 . fig7 illustrates the interaction between leptin genotype and zh on daily dry matter intake ( ddmi ). zh administration has a statistically significant interaction with leptin genotype ( p = 0 . 01 ) with respect to daily dry matter intake ( ddmi ). in the absence of zh administration , tt &# 39 ; s had the highest ddmi , cc &# 39 ; s had the lowest ddmi and the ct &# 39 ; s consumed the intermediate amount ( fig8 ). when the tt &# 39 ; s were administered zh they had the lowest ddmi as compared to the cc &# 39 ; s which had the highest ddmi . again the ct &# 39 ; s had an intermediate amount and had a ddmi lower than the cc animals . in summary , the cc animals had no change in ddmi during zh treatment , but ct & amp ; tt animals had a significant reduction in ddmi during zh treatment . see fig7 . fig8 illustrates the effect of leptin genotype on feed intake ( ddmi ). leptin genotype significantly impacted daily dry matter intake ( fig8 ). specifically total ddmi was assessed for the complete feeding period , and the final 24 days of the feeding period . this assessment did not consider animals fed zh or any interactions . therefore , it only considered animals not fed β - aa &# 39 ; s . tt animals have a significant increase in ddmi over the complete feeding period and the final 24 days on feed time period in comparison to ct and cc animals , respectively . fig9 illustrates the interaction between leptin genotype and zh on size of rib eye area ( rea ) gain . zh administration has a statistical tendency to interact with leptin genotype ( p = 0 . 118 ) with respect to rib eye area ( in 2 ). response to zh administration varied by genotype with the cc &# 39 ; s having the lowest response to zh administration . tt &# 39 ; s and ct &# 39 ; s have the largest response to zh administration . tt and ct animals had a gain of 1 . 4 square inches compared to cc &# 39 ; s having a gain of 0 . 35 square cm &# 39 ; s ( 0 . 9 square inches ). see fig9 . fig1 illustrates the interaction between leptin genotype and zh on % empty body fat (% ebf ). zh administration tends to interact with leptin genotype ( p = 0 . 09 ) with respect to % ebf . response to zh administration varied by genotype with the cc &# 39 ; s having the lowest response to zh administration . tt &# 39 ; s and ct &# 39 ; s have the largest response to zh administration . tt and ct animals respectively had the largest reductions in % ebf , with the tt animals having the largest reduction in % ebf . since % ebf is a mathematical formula ( 23 ), which relies on the amount of marbling ( quality grade ), it is understood that the % ebf is in part a function of the marbling interaction between leptin genotype and zh . as tt animals have the largest reduction in marbling when fed zh it is no surprise that tt animals have the largest in % ebf when fed zh . concurrently , since cc animals experience no reduction in marbling when fed zh it is very supportive that they too experience the smallest reduction in % ebf when fed zh . see fig1 . what was observed and discovered out of the trial work described herein is that mass application of zilmax ® and optaflexx ® is not necessary and does not yield optimal results . this is due the several interactions observed between leptin genotype and the β - aa &# 39 ; s . these interactions teach that selective application of these growth promoting agents based on leptin genotype can yield results not obtained when the β - aa &# 39 ; s are mass applied to pens of cattle . specifically , application of zilmax ® to cc genotype animals yields the most optimal results for this genotype . this is due to the larger than “ label ” or expected response in hcw , and small or no reduction in marbling and quality grade ( usda choice or better ). marbling is an important attribute in carcass composition , and is commonly factored into how an animals &# 39 ; value is determined . therefore , reaching a threshold amount of marbling is important to producers , and any factor that reduces the amount of marbling is a negative factor for producers ; such as mass application of zilmax ®. in addition , rea size is optimal when it is kept to a size such that an acceptable portion size can be obtained , which in practice means that as the rea continues to get larger it is detrimental . therefore , as zilmax ® is known to increase rea size , feeding zilmax ® to cc &# 39 ; s can limit the downside in this area . also , the detrimental effect of zilmax ® on % ebf is limited when fed to cc animals . and , importantly , no reduction in ddmi is observed when zilmax ® is fed to cc animals , which is contributing to the increased hcw observed in cc animals . conversely , when observing the tt animals fed zilmax ® it is clear that there are specific detrimental effects on important phenotypes . ddmi is reduced in tt animals fed zilmax ® in comparison to ct & amp ; cc animals , respectively , which is a contributor to the reduction in marbling and quality grades ( usda choice or better ). the reduction in ddmi in tt animals is detrimental to the economics of the animal as it increases its overall proportional maintenance cost . that is , as a proportion of the total energy available for gain , tt animals fed zh have a smaller proportion out of their total energy intake per day than cc & amp ; ct animals . the reduction in marbling is also backed up by the fact that there is also the largest reduction in % ebf when tt animals are fed zilmax ® in comparison to ct & amp ; 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