261 HIGH NUTRITION DURING EARLY LIFE IMPROVES REPRODUCTIVE POTENTIAL OF HOLSTEIN BULLS

Abstract

The objective was to determine effects of early-life nutrition on reproductive potential of Holstein bulls. Twenty-six bull calves were randomly allotted to 3 groups and fed ~70, 100, or 130% of National Research Council recommendations for both energy and protein from 2 to 31 wk; thereafter, all were fed a 100% diet (adequate vitamins and minerals were constantly available) until slaughter (72 wk). Growth rate, scrotal circumference, and paired testis volume were determined every 4 wk during the differential feeding period. Once scrotal circumference reached 26 cm, semen collection was attempted (to confirm puberty). Post-pubertal semen quality was monitored; once bulls were producing 70% morphologically normal sperm, semen was cryopreserved (programmable freezer). These semen samples (3 bulls per group and 3 ejaculates per bull) were used in an IVF system to determine the fertilizing ability of sperm and developmental competence of resulting embryos. In the low-, medium-, and high-nutrition groups, respectively, bulls were 369.3 ± 14.1, 327.4 ± 9.5, and 324.3 ± 11.7 days at puberty; their paired testes weights were 561.6 ± 23.1, 611.1 ± 59.1, and 727 ± 33.0 g; cleavage rates were 68.0 ± 8.7, 77.1 ± 3.5, and 68.7 ± 4.5%; and blastocyst rates were 31.5 ± 5.6, 41.4 ± 4.9, and 33.7 ± 4.6% (no significant differences among the 3 nutrition groups for rates of cleavage or blastocyst formation). We concluded that early-life supplementation of energy and protein hastened puberty (P < 0.05) and increased testicular size (P < 0.05), without compromising sperm fertilizing ability. Therefore, feeding dairy bull calves a high plane of nutrition early in life is recommended as a management strategy to improve their reproductive potential.