Enhanced early-life nutrition promotes hormone production and reproductive development in Holstein bulls

Abstract

Holstein bull calves often reach artificial insemination centers in suboptimal body condition. Early-life nutrition is reported to increase reproductive performance in beef bulls. The objective was to determine whether early-life nutrition in Holstein bulls had effects similar to those reported in beef bulls. Twenty-six Holstein bull calves were randomly allocated into 3 groups at approximately 1 wk of age to receive a low-, medium-, or high-nutrition diet, based on levels of energy and protein, from 2 to 31 wk of age. Calves were on their respective diets until 31 wk of age, after which they were all fed a medium-nutrition diet. To evaluate secretion profiles and concentrations of blood hormones, a subset of bulls was subjected to intensive blood sampling every 4 wk from 11 to 31 wk of age. Testes of all bulls were measured once a month; once scrotal circumference reached 26cm, semen collection was attempted (by electroejaculation) every 2 wk to confirm puberty. Bulls were maintained until approximately 72 wk of age and then slaughtered at a local abattoir. Testes were recovered and weighed. Bulls fed the high-nutrition diet were younger at puberty (high=324.3 d, low=369.3 d) and had larger testes for the entire experimental period than bulls fed the low-nutrition diet. Bulls fed the high-nutrition diet also had an earlier and more substantial early rise in LH than those fed the low-nutrition diet and had increased concentrations of insulin-like growth factor-I (IGF-I) earlier than the bulls fed the low-nutrition diet. Furthermore, we detected a temporal association between increased IGF-I concentrations and an early LH rise in bulls fed the high-nutrition diet. Therefore, we inferred that IGF-I had a role in regulating the early gonadotropin rise (in particular, LH) and thus reproductive development of Holstein bulls. Overall, these results support our hypothesis that Holstein bull calves fed a high-nutrition diet reach puberty earlier and have larger testes than those fed a low-nutrition diet, and they provide clear evidence that nutritional modulation of Holstein bull calves during early life has profound effects on reproductive development.

Effects of nutrition on sexual development of bulls

“…In a similar study performed recently on Holstein-Friesian and Jersey bull calves between 3 to 49 weeks of age these results could be confirmed (Byrne et al, 2017). In addition, Dance et al (2015) noticed at 72 weeks, that bulls fed the highnutrition diet had greater paired testes weights. The estimated number of sperm produced by day in the bulls of the high-nutrition group was about 9% higher compared to the bulls of medium-nutrition group and about 30% higher than the number estimated in bulls of the low-nutrition group, while no differences in sperm quality were noticed depending on nutrition of the bulls (Dance et al, 2016).…”

“…The estimated number of sperm produced by day in the bulls of the high-nutrition group was about 9% higher compared to the bulls of medium-nutrition group and about 30% higher than the number estimated in bulls of the low-nutrition group, while no differences in sperm quality were noticed depending on nutrition of the bulls (Dance et al, 2016). Overall, the results obtained by Dance et al (2015Dance et al ( , 2016 and Byrne et al (2017) are consistent with the studies from Brito et al (2007a, c, d), who modified the nutrition of beef bulls starting at the prepubertal period. All these studies provide clear evidence that nutritional modulation of bull calves before puberty has profound effects on reproductive development.…”

“…All these studies provide clear evidence that nutritional modulation of bull calves before puberty has profound effects on reproductive development. Because Dance et al (2015) and Byrne et al (2017) modulated the nutrition during the infantile and prepubertal periods, it is unclear, however, whether a nutritional modulation is required for both periods to obtain these effects on reproductive development or whether a shorter time interval would be as effective.…”

“…In one study (Bratton et al, 1956) carried out more than 60 years ago, restriction of feed intake in Holstein bull calves from 1 to 80 weeks of age had a tremendous negative effect on pubertal development. In recently published studies, Dance et al (2015Dance et al ( , 2016 examined the effects of early life nutrition on reproductive development in Holstein bulls. Twenty-six Holstein bull calves were randomly allocated into 3 groups at approximately 1 week of age to receive either a low-, medium-, or high-nutrition diet from 2 to 31 weeks of age.…”

Effect of breed, plane of nutrition and age on growth, scrotal development, metabolite concentrations and on systemic gonadotropin and testosterone concentrations following a GnRH challenge in young dairy bulls

“…Other authors concluded that daily gains of greater than 1.2 kg/day during calf-hood should be targeted to ensure earlier attainment of puberty in bulls [9]. More recently, a higher plane of nutrition led to a greater scrotal circumference (SC) and thus hastened age at puberty in Holstein-Friesian bulls [10]. It has also been suggested that SC can be used as a predictor of sperm output potential in young dairy bulls [11].…”