GROWTH AND ATTAINMENT OF PUBERTY IN HEIFERS FROM COWS SUPPLEMENTED WITH LINSEED MEAL DURING EARLY LACTATION

Preliminary studies in our group suggested diets during early lactation for beef cows may influence puberty onset and offspring growth. This study examined the effects of supplementing cows with phytoestrogen rich linseed meal (LSM) during lactation on heifer calf growth and reproduction. Immediately after parturition, multiparous cow-calf pairs were allotted randomly to one of 12 pens, with six pens supplemented with LSM and six pens fed a control pellet consisting primarily of dried distillers grain plus solubles (CON). Both supplements were pelleted, isocaloric, and isonitrogenous and were offered prior to feeding alfalfa hay each day for the first 60 d of lactation. Heifer calves (n = 91) were followed from birth to 315 d of age. Birth wt, sixty d BW, and actual weaning weights were recorded, and adjusted weaning wt was calculated. On d 229.2 ± 1.5 of age and every 14 d until d 313.2 ± 1.5 of age, heifers were weighed, and venous blood samples were collected for progesterone analysis. Visual body condition score (BCS) was taken on ~d 229, 287, and 313. Birth weights were not different between groups and there was no effect of treatment on d 60 wt (P > 0.20; 39.5 ± 1.1 and 99.7 ± 2.2 kg, respectively). There was a tendency (P = 0.11) for heifers from LSM cows to have a greater adjusted weaning wt compared to heifers from CON cows (254.3 vs 243.0 ± 5.2 kg). Heifer BCS was not affected (P = 0.22) but heifers from LSM cows were heavier (P = 0.04) than heifers from CON cows (292.4 vs 286.1 ± 2.4 kg). Previous studies indicated that some heifers start to cycle at 7 mo of age, however in the current study only 27 heifers attained puberty by the completion of the trial (14 CON and 11 LSM; P = 0.40). Initial data regarding LSM supplementation during early lactation indicates that LSM does not appear to impact onset of puberty in heifer calves. However, it appears that LSM supplementation may enhance wt gain without influencing BCS of heifer calves. Further research is needed to explain the effects of phytoestrogens on growth and development of livestock.