Influence On Growth Performance And Beef Quality Of Holstein Culling Cows And Dairy Bull Fed Different Nutrition Levels In Diet

This experiment studied the influence on growth performance and beef quality ofHolstein culling Cows and dairy bulls fed different nutrition levels in diet. It was toconfirm the levels of nutrition in fattening Holsein culling cows and dairy bulls and toimprove beef quality, finally, it could provide scientific basis for fattening Holsein cullingcows and dairy bulls.This study included two experiments:Experiment1: Influence on Growth Performance and Beef Quality of HolsteinCulling Cows Fed Different Nutrition Levels in Diet.According to a single factorial design, thirty-two healthy culling Holstein cows withsimilar body weight were selected and randomly divided into four groups, groupⅠ(lownutrition), group Ⅱ (medium nutrition), group Ⅲ (high nutrition), group Ⅳ (highernutrition), the test included two stage. The nutrition levels of earlier stage were different，digested energy(DE)=12.54,12.99,13.44,13.90MJ/kg, crude protein(CP)=12.02%,13.56%,15.05%,16.52%(DM); Latter stage of experiment: DE=12.99,13.44,13.90,14.35MJ/kg, CP=12.00%,13.51%,15.00%,16.52%(DM). The results showed that:With the levels of nutrition raising, the average daily gain(ADG) was also improved,the group Ⅳ enhanced ADG by30.84%(P<0.05), the feed efficiency improved by31.80%(P<0.05) and back fat thickness increased by73.33%(P<0.05) comparing with thegroupⅠ. The slaughter rate and net meat percentage were no significantly different(P>0.05), they were the highest in group Ⅱ(51.49%and42.03%); Glutamic-oxalacetictransaminease(AST) in groupⅠ was the highest and that in group Ⅱ was the lowest，their values were69.15U/L and62.15U/L, groupⅠsignificantly increased by11.25%(P<0.05) than group Ⅱ;The serum thyroxin (T4) in group Ⅳ was higher56.51%(P<0.01)，40.25%(P<0.01),45.55%(P<0.01) respectively, in comparision withother groups; The apparent digestibility of crude protein and crude fat were significantlydifferent (P<0.05), they were the highest in group Ⅲ (72.47%and80.64%).The meat cooking rate, fat content and fatty acid content of beef were significantlyaffected (P<0.01) by nutrition levels in diet. The group Ⅲ meat cooking rate was49.73% that significantly higher6.03%（P<0.01）、7.87%（P<0.01）、4.30%（P<0.01）than othergroups;The fat content of beef enhancend by70.10%(P<0.05) when compared group Ⅳ(6.94%) with groupⅠ(4.08%),whereas, other nutrition content were not significant; PUFAcontent of group Ⅳ was the lowest and that of group Ⅱ was the highest, group Ⅱobviously improved by61.58%(P<0.05) than group Ⅳ. Compared with groupⅠandgroup Ⅳ, PUFA content of group Ⅲ was obviously higher2.47%(P>0.05) and58.31%(P<0.05);Compared with the breed benefit, the group Ⅱ(1.99yuan) was increased by0.43yuan than group Ⅲ. Therefore, for finishing Holstein culling cows, weighed from410to470kg, it is suggested that the nutrient levels of the dry matter intake (DMI), digestedenergy intake(DE intake) and crude protein intake(CP intake) are11.03～11.53kg/d,147.86～150.05MJ/d and1.57～1.66kg/d (DM), respectively; While, in terms of fatteningcows, weighed from470to530kg, it is suggested that the nutrient levels of DMI, DEintake, CP intake are10.76～11.23kg/d,149.18～151.21MJ/d and1.53～1.62kg/d(DM),respectively. In the whole experiment period, the ADG is1.20～1.29kg.Experiment2: Influence on Growth Performance and Beef Quality of Holstein BullsFed Different Nutrition Levels in Diet.According to a single factorial design, forty healthy Holstein bulls with similar bodyweight were selected and randomly divided into four groups, groupⅠ(low nutrition),group Ⅱ(medium nutrition), group Ⅲ(high nutrition), group Ⅳ(higher nutrition), the testincluded two stages. The nutrition levels of earlier stage were: DE=12.54,12.81,13.08,13.35MJ/kg, CP=13.00%,14.00%,15.00%,16.00%(DM); Latter stage of experiment:DE=12.81,13.08,13.35,13.63MJ/kg, CP=13.03%,14.01%,15.00%,16.01%(DM). Theresults showed as follow.ADG of bulls was improved along with the nutrition levels increasing, ADG risedfrom1.14kg/d to1.44kg/d, relatively increased by26.32%(P<0.05). Meanwhile, the backfat thickness and apparent digestibility of crude protein were significantly affected bynutrition in diet (P<0.05); compared with other groups, back fat thicknes of group Ⅳ(0.65cm) obviously raised by96.97%(P<0.01),91.17%(P<0.01) and12.07%(P>0.01),respectively; The crude protein digestibility of group Ⅲ was higher2.78%than that ingroup Ⅳ.Results indicated that increasing nutrition levels in diet, the shear force was decreased,fat and fatty acid content were enhanced significantly, thus, increasing nutrition levels canimprove beef quality. On the one hand, the shear force were significantly different(P<0.05)at48h and72h, and they were the lowest in group Ⅳ(4.36and3.97); Compared withother groups, the shear force of group Ⅳ decreased by22.02%(P<0.01),25.92%(P<0.01),10.55%(P<0.01) at48h and that obviously reduced by13.85%(P<0.05),6.30%(P>0.05) and8.31%(P>0.05) at72h, respectively.On the other hand, the fat content of group Ⅱ(2.27%) was obviously enhanced by60.99%(P<0.05) than that in groupⅠ(1.41%); MUFA content was the highest in group Ⅱ(42.57%) that was obviously higher4.96%(P<0.05) than group Ⅳ;The breed benefit of group Ⅲ(9.77yuan) was increased by2.70yuan in comparisionwith group Ⅳ(6.34yuan).In conclusion, for finishing Holstein dairy bulls, weighed from350to430kg, it is suggested that the nutrient levels of DMI, DE intake and CP intake are8.85～9.15kg/d,113.91～119.89MJ/d and1.25～1.37kg/d (DM); While, in terms offattening bulls, weighed from430to510kg, it is suggested that the nutrient levels of DMI,DE intake, CP intake are8.75～9.03kg/d,115.09～120.76MJ/d and1.23～1.36kg/d(DM). In the whole experiment period, the ADG is1.35～1.44kg.