title: 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.
authors.affiliation: Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada.
authors.forename: Alysha
authors.initials: A
authors.lastname: Dance
authors.affiliation: Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada.
authors.forename: Jacob
authors.initials: J
authors.lastname: Thundathil
authors.affiliation: Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, AB T1J 4B1, Canada.
authors.forename: Randy
authors.initials: R
authors.lastname: Wilde
authors.affiliation: L'Alliance Boviteq Inc., Saint-Hyacinthe, QC J2T 5H1, Canada.
authors.forename: Patrick
authors.initials: P
authors.lastname: Blondin
authors.affiliation: Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada. Electronic address: jpkastel@ucalgary.ca.
authors.forename: John
authors.initials: J
authors.lastname: Kastelic
mesh_terms: D000821:Animal Feed / Q000032:analysis*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002417:Cattle / Q000254:growth & development*; D004032:Diet / Q000662:veterinary*; D006062:Gonadotropins / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D009752:Nutritional Status; D009753:Nutritive Value; D015800:Protozoan Proteins; D013737:Testis / Q000254:growth & development
chemical_list: D006062:Gonadotropins; D015800:Protozoan Proteins; C072098:aginactin protein, Dictyostelium; D007334:Insulin-Like Growth Factor I
keywords: Holstein bull; nutrition; puberty; testes