Effects Of Oral Melatonin On Performance, Carcass And Meat Quality For Growing-Finishing Pigs

To test the effects of oral melatonin on performance, nutrients digestibility ,carcass and meat quality of growing-finishing pigs, 15 pigs (Landrace×Yorkshire) (initial weight 35kg approximately) were employed and divided into 3 groups with 5 replicates of 1 pig . One group were fed high level melatonin (3.0mg MT/kg body weight/d), one group were fed low level melatonin (1.5mg MT/kg body weight/d), and one group as the control were fed basal diet without melatonin. The results showed that:(1) Effects of MT on performance:For phase Ⅰ (from 35kg to 80 kg approximately): high level MT reduced the average daily gain (ADG) and feed intake (ADFI) of pigs by 11.31%(P<0.01) and 13.63% (P<0.01) respectively, and the feed to gain ratio (F/G) also was reduced (P>0.1) compared to the control. The ADG and ADFI of pigs in low level MT group were similar to the control, but the feed to gain ratio (F/G) reduced significantly by 5.85%(P<0.05).For phase Ⅱ (from 80kg to 95kg approximately): there was no difference in ADG among treatments. The ADFI of pigs in the high or low level MT group decreased by 12.88% (P<0.05) or 19.31% (P<0.01) respectively compared to the control. The feed to gain ratio(F/G) in high level MT group were similar to the control, while decreased by 21.39% (P<0.05) in low level MT group compared to the control.For total phase (from 35kg to 95kg approximately):The ADG , ADFI and F/G in high level MT group reduced by 8.37% (P<0.01) ,12.94% (P<0.01) and 4.73%( P<0.05) respectively compared to the control. In low level MT group ,the ADFI and F/G also reduced by 9.41% (P<0.01) and 11.04% (P<0.01) respectively, but the ADG had no difference compared to the control.(2) Effects of MT on nutrients digestibility:Two levels of MT had no significant influences on apparent digestibility of feed gross energy and total organic nutrients for pigs, but the apparent digestibility of crude fat(CEE) was reduced by 6.19%( P<0.05 )and 5.27%(P=0.056) for high and low level MT respectively compared to control .Apparent digestibility of crude protein(CP) was reduced in high level MT group, but improved in low level MT group, and there was significant different between high level and low level MTgroups. The apparent digestibility of carbohydrates had the tendencies to be improved in high level MT group.(3) Effects of MT on carcass quality:There was no significant difference in carcass weight between the two levels of MT group and the control. But there were the tendencies that low level MT increased the carcass weight, high level MT reduced the carcass weight. While the carcass weight of low level MT group was increased by 13.66%(P=0.131) compared to that of high level MT group. The slaughter ratios of the two levels of MT group were improved to some extent, especially the low level MT group with 7.61% (P=0.082) increased . The loin muscle area of high level MT group was 34.62% and 38.41%(P<0.05 Mower than those of control group and low level MT group respectively , while there was no notable difference in loin muscle area between low level MT group and control group. The thickness of back fat of high level MT group was reduced by 2.11% (P=0.084) compared to the control, and low level MT also trended to reduce thickness of back fat. The MT of two levels both reduced the leaf fat weight of pigs. The leaf fat weight of group were fed high and low level MT were respectively reduced by 25.71%(P=0. 187) and 12.74% (P=0. 571) compared to the control. The two levels MT both reduced the leaf fat to carcass weight ratio of swine, which of high level of MT group was reduced by 17.72%(P=0.268) .(4) Effects on parameters related to meat quality:The significant difference in pH45(the detected pH value of loin muscle at 45min post- slaughter) were not observed among treatments, but higher pH24(the detected pH value of loin muscle at 24h after post-slaughter) were observed in the two levels MT groups, and the 0.1) level MT group lower than that of the control, and the b values of loin muscle in high level MT group tend to be lower(p=0.07). The drip loss of loin muscle in high or low level MT group increased by 87.82% (P=0.083) and 33.33%(P>0.1) respectively compared to the control. There were no difference in marbling score, intramuscular fat contents and MDA levels of loin muscle among three treatments.It can be concluded that oral 3.0 mg/kg BW/d or 1.5mg/kgBW/d MT could affect performance, digestibility of feed CP and CEE for growing-finishing pigs. The oral MT could decrease the deposit of body protein and fat of pigs, which might improve the pH24 and drip loss of meat, decrease the a and b values of meat detected at 24h post-slaughter.