| Light is an important environmental factor affecting beef cattle industry.Study on the effect of light time on beef cattle is the basis of modernize production for beef cattle industry.The aim of this study was to determine the effects of 16 hour light time on production performance,behavior and blood biochemical index in Jinjiang bull and heifer.It is helpful to further reveal the influence and cause of long-day photoperiod on Jinjiang bull’s performance and diurnal rhythm by increasing the long-day photoperiod to 16 hours in autumn and winter.The trail includes three parts:1 Effect of Long-Day Photoperiod on Growth in Jinjiang CattleTo investigate the effects of long-day photoperiod on the production performance ofJinjiang cattle,a total of 26 healthy Jinjiang cattle(16 bulls 275.93±7.26 kg;10 heifers 145.15±15.60 kg)were selected.According to sex,they were randomly divided into two groups(16 h light group and natural light group),and 8 bulls and 5 heifers in each group.The body weight of each heifer was recorded at the 1th,35th,70th and 117th day to calculate the average daily gain(ADG).Population feeding and residual feeding were recorded to calculate dry matter intake(DMI)and feed-to-weight ratio(F/G).The results showed that:(1)The final weight and average daily gain of Jinjiang cattle increased significantly(P<0.01)and the dry matter intake increased but the ratio of feeding to weight decreased;(2)At 15.6-35.4℃,the effect of long-day photoperiod on Jinjiang cattle was the best(P<0.05),and the effect of gaining weight of heifers at 1.2-15.2℃ was the best(P<0.05).It can be concluded that increasing light to 16 hours can increase feed intake of Jinjiang cattle,and improve their production performance.2 Effect of Long-Day Photoperiod on Blood Biochemical Indexes in Jinjiang CattleThis research was conducted to investigate the effect of long-day photoperiod on blood biochemical indexes of Jinjiang cattle,the grouping and design of the trial were the same as the first chapter.Blood samples were collected from jugular vein at end of the trial,and blood routine examination was measured.Meanwhile,blood samples of Jinjiang cattle were collected at intervals of 2 hours during 24 hours,and the concentrations of melatonin,growth-related hormone and immune-related hormone were measured.The results showed that:(1)The content of melatonin in 16 h light group was decreased,and the decrease was the greatest during Artificial Supplementary light,Long-day photoperiod can affect GH and IGF-1 secretion through Mel;(2)The content of GH and IGF-1 in 16 h light group was increased,and there was a linear correlation between GH and IGF-1(bull,r=0.81,P=0.001;heifer,r=0.78，P<0.01),and the content of LEP was decreased;(3)IgA and TNF-α in 16 h light group were increased,and there was a significant linear correlation between IgA and TNF-α(bull r=0.83,P<0.001;heifer r=0.84,P<0.001),and WBC and MON of bulls were significantly higher than that of natural light group(P<0.05).In summary,Mel and GH have a 24-hour cycle,but long-day photoperiod can increase the amplitude of Mel cycle and promote the increase of GH and IGF-1,It can also improve the level of immune related indicators..3.Effects of Long-Day Photoperiod on Hormone and Behavior Daily Rhythm in Jinjiang CattleThis part was to study the effects of long-day photoperiod on hormone and behavior diurnal rhythm of Jinjiang cattle,the grouping and design of the trial were the same as the first chapter.On the 3rd-21st,32nd-44th and 68th-80th day of the trial period,the behavior of beef cattle was observed continuously from 8:00 a.m to 17:30 p.m.The feeding time,times,rumination time,lying time and times of each cattle were recorded respectively.On the 5th-15th,43rd-49th and 73rd-80th day,the number of Jinjiang cattle at 8:00,9:30,11:30,13:00,15:00 and 17:00 of the day,were calculating by instantaneous observation to gain the lying rate.On 39th-49th and 74th-85th day,three in each group were randomly selected to record 24-hour activity for continuous 3 days.The results showed that:(1)The feeding time and each feeding time decreased significantly(P<0.01),the rumination time and the lying time increased significantly(P<0.01)and the number of rumination increased significantly(P<0.05).(2)The lying rate of bulls in 16 hour light group was increased by 83.80%,39.98%and 105.86%at 8:00,13:00 and 15:00 respectively(P<0.01);the lying rate of heifers in 16 hour light group was increased by 288.63%,307.88%84.08%,309.77%and 699.43%(P<0.01)at 8:00,9:30,11:30,15:00 and 17:00 respectively,and the16 h light group increased by 40.30%(P<0.05)at 13:00.(3)The average activity of 16 hours light group was decreased by 39.21%at 1:00-6:00,it was significantly decreased at 12:00-13:00 and 14:00-15:00(P<0.05),and at 13:00-14:00 and 15:00-16:00,the difference was extremely significant(P<0.01).(4)Jinjiang cattle’s activity level was negatively correlated with Mel content(natural light group,r=0.71,P=0.011;16 h light group,r=0.65,P=0.023),but not significantly correlated with GH content.There was a significant linear correlation between the activity level and T3 content(r=0.67,P=0.017)in 16 h light group,but no significant linear relationship between activity and T3 content in natural light group(r=0.56,P=0.060).It can be concluded that the long-day photoperiod can increase rumination time,lying time and the lying rate of Jinjiang bull,and reduce Jinjiang bull’s activity level,which is affected by Mel and T3 level. |
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