The effect of daylength and level of feeding on serum prolactin in growing lambs.
Twenty-four castrated male lambs initially maintained on a photoperiod of 12 h light:12 h dark were allocated to a factorial experiment with two daylengths (8 h L: 16 h D or 16 h L: 8 h D) and two levels of feeding (restricted or ad libitum). Blood samples were taken every 4 h for 24 h during the introductory period and after 24, 51 and 79 days of treatment. There were highly significant positive effects of daylength and level of feeding on serum prolactin: mean concentrations increased from a mean of 38 plus or minus 1 ng/ml during the introductory period until at day 79 they were: 8L: 16D (restricted diet), 81 ng/ml; (food ad libitum), 167 ng/ml; 16L:8D (restricted diet), 262 ng/ml; (food ad libitum), 262 ng/ml (S.E. of treatment mean plus or minus 4). Long daylength and feeding ad libitum also significantly increased growth rate.
D000818:Animals; D001835:Body Weight; D002940:Circadian Rhythm; D004435:Eating; D005260:Female; D008027:Light; D008055:Lipids / Q000096:biosynthesis; D008297:Male; D010507:Periodicity; D011388:Prolactin / Q000097:blood*; D012621:Seasons; D012756:Sheep / Q000097:blood* / Q000254:growth & development; D013312:Stress, Physiological; D013997:Time Factors
D008055:Lipids; D011388:Prolactin