Effect of Total Digestible Nutrient Intake from Birth to Four Years of Age on Growth and Reproductive Development and Performance of Dairy Bulls

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Abstract
Neonatal Holstein bull calves were assigned to 4 levels of energy intake representing 70, 100, 115, and 130% of the National Research Council recommended TDN allowances. The groups were designated L, N, M, and H, respectively. Two additional groups were on a changeover at 104 weeks of age[long dash]LH changed from 70 to 130% and HL from 130 to 70%. Data were collected on growth, onset of semen production, and semen quantity and quality until the bulls reached 208 weeks of age. The average age at the onset of semen production was 61, 45, 41, and 44 weeks, respectively, for the L, N, M, and H groups. At 80 weeks of age, the average motile sperm output per ejaculate was 1.15 billion for the L group; this was about 50% of that for the H group. After 112 weeks of age there was no difference in output of motile sperm per ejaculate associated with level of energy intake. Between 156 and 208 weeks of age, the H bulls became much slower in sexual reaction time than bulls in other groups. During this period weaknesses of the feet and legs also became evident in the H bulls. Sperm output and extra-gonadal sperm reserves were similar among bull groups. Fertility data collected on the L, N, and H groups showed no marked difference attributable to the level of TDN intake.