| Abstrakt: |
Soybean meal can be used as an alternative protein source for growing bulls, but contains phytoestrogens that potentially impact male fertility if fed at elevated levels for extended periods of time. The age of dam (AOD) effect is also an important consideration in bull development. The objective of this study was to investigate the interaction of phytoestrogens and AOD effects in bull development programs. Angus bulls (n=63) from 2 subsequent years were stratified by weaning weight, AOD, and sire across 2 diet treatments: a phytoestrogen consuming group with 10% soybean meal as a protein source (SBM), and a phytoestrogen naïve group with cottonseed meal as a protein source (CSM). At d -42 in each year bulls were weaned, weighed, and sorted into ad libitum diet treatment groups. Body weights were collected again at d 0, 21, 54, and 86 with ADG being calculated between intervals. On d 79 and 86 semen samples were collected via electro-ejaculator. The d 79 sample verified tract dispels on all bulls and was discarded while semen quality characteristics were recorded using the d 86 samples. Semen motility scores were assessed via the same trained personnel in both years using a 5-point scale. Semen concentration was determined via Dupree densimeter. Data was compiled and MIXED procedures of SAS were used to analyze weights with a model that included effects of day(year), diet, AOD, diet × AOD, and d -42 weight as a covariate. This model was analyzed as repeated measures using the AR(1) option. Semen quality parameters and ADG were analyzed with a similar model that excluded the repeated measure statements. In all models least squares means were separated and P ≤ 0.05 was considered different. Bulls from 3, 4, and 5+ year old cows achieved higher ADG when fed SBM (P ≤ 0.03), compared to CSM consuming bulls produced by similar aged cows. Semen concentration of SBM consuming bulls from 2 year old cows was greater than CSM consuming bulls by 2 year old cows, but a reverse trend was observed in bulls produced by 5+ year old cows as CSM consuming bulls recoded higher semen concentration compared to SBM consuming bulls (P ≤ 0.01). Because a diet × AOD interaction was detected in these data, further data is needed to explain this relationship. [ABSTRACT FROM AUTHOR] |
