Impact of dietary lysine intake during lactation on follicular developmentand oocyte maturation after weaning in primiparous sows

Primiparous sows (n = 36) were used to evaluate the effects of dietary lysi ne intake in lactation on follicular development and oocyte maturation afte r weaning. Sows were assigned randomly to one of three diets containing .4% (low lysine, LL), 1.0% (medium lysine, ML), or 1.6% thigh lysine, HL) tota l lysine. All diets contained 2.1 Meal NE/kg and exceeded NRC (1988) requir ements for all other nutrients. Actual lysine intakes over an 18-d lactatio n were 16, 36, and 56 g/d for sows consuming LL, ML, and HL, respectively. Ovarian data were analyzed for sows determined to have been slaughtered dur ing the first proestrus period after weaning, using previously established criteria. Compared with sows fed ML and HL, sows fed LL tended to have lowe r uterine weight, follicular fluid volume, and follicular fluid (FF) estrad iol (E-2) content (P < .15), but similar ovarian weight and follicular flui d IGF-I concentration. Within the largest 15 preovulatory follicles, sows f ed LL had a lower percentage of large (greater than or equal to 7.0 mm) fol licles (33 vs 50 and 58%; P < .01) and a higher percentage of medium (5.5 t o 7.0 mm) follicles (62 vs 44 and 39%; P < .01) but a similar percentage of small (less than or equal to 5.5 mm) follicles (4.4 vs 5.9 and 3.7%; P > . 15), respectively, compared with sows fed ML or HL. Standardized pools of o ocytes aspirated from follicles of prepubertal gilts were incubated for 44 h with pooled FF recovered from the largest 15 follicles of each experiment al sow. Fewer oocyte nuclei matured to metaphase II of meiosis when culture d with FF recovered from sows fed LL, than from sows fed ML or HL (47.1 vs 59.8 and 63.8%, respectively; P < .01). Our results suggest that low lysine (protein) intake in primiparous lactating sows impaired follicular develop ment and reduced the ability of follicles to support oocyte maturation. How ever, high compared with medium lysine (protein) intake had no further posi tive effects on ovarian function.