The possible roles of dietary protein level and feed restriction in regulating mammary development of prepubertal gilts were investigated.
本試驗的研究目的是評估后備母豬青春期日糧蛋白質(zhì)水平及限飼對母豬乳腺發(fā)育的影響。
Crossbred gilts were fed a commercial diet until 90 d of age and then divided into four nutritional regimens based on two pelleted diets (as-fed basis): a high-protein diet (HP = 13.8 MJ of ME, 1.0% total lysine, 18.7% CP) and a low-protein diet (LP = 13.8 MJ of ME, 0.7% total lysine, 14.4% CP).
Nutritional regimens were as follows:1) HP ad libitum until slaughter (n = 22, T1); 2)HP ad libitum until 150 d of age followed by LP untilslaughter (n = 20, T2); 3) LP ad libitum until slaughter(n = 21, T3); and 4) HP with a 20% feed restriction untilslaughter (n = 19, T4).
Gilts were weighed, their backfat thickness was measured, and jugular blood samples were obtained on d 90, 150, and at slaughter to determine concentrations of prolactin, IGF-I, leptin, and glucose. Gilts were slaughtered 8 ± 1 d after their first or second estrus (202.7 ± 14.5 d of age). Mammary glands were excised, parenchymal and extraparenchymal tissues were dissected, and composition of parenchymal tissue (protein, fat, DM, DNA, protein/DNA) was determined.
The T4 gilts weighed less (P < 0.01) and had less backfat (P < 0.01) than did gilts on other treatments on d 150 and at slaughter.
T4組母豬150日齡、屠宰時體重、背膘厚顯著低于其它3組。
Treatments had no significant effects on prolactin, IGF-I, or glucose concentrations, but there was a treatment × day interaction (P< 0.01) for leptin, with concentrations being lower at slaughter in restricted-fed (T4) vs. LP (T3) gilts (P <0.05).
There was less extraparenchymal mammary tissue (P < 0.01) in T4 gilts than in gilts from the other groups and a tendency (P = 0.13) for the amount of parenchymal tissue to be lower in T4 gilts.
In conclusion,a lower lysine intake during prepuberty did not hinder mammary development of gilts, but a 20% feed restriction decreased mass of parenchymal and extraparenchymaltissues. The effect of feed restriction on extraparenchymal tissue is most likely associated with the lower fat deposition.