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水平及限飼對母豬乳腺發育的影響。
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.
T4組母豬乳腺外周組織重量顯著低于其它3組，導致乳腺實質組織重量也低于其它3組，但差異不顯著。
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.