The body condition score (BCS) of a dairy cow is an assessment of the proportion of body fat that it possesses, and it is recognized by animal scientists and producers as being an important factor in dairy cattle management. The scale used to measure BCS differs between countries, but low values always reflect emaciation and high values equate to obesity. The intercalving profile of BCS is a mirror image of the milk lactation profile. Cows lose condition for 50 to 100 d postcalving, because of homeorhetic changes that occur in the somatotropic axis and the sensitivity of peripheral tissues to insulin, and the upregulation of lipolytic pathways in adipose tissue. Management and feeding have little effect on early postcalving BCS loss (wk 1 to 4 postcalving) until the natural period of insulin resistance has passed and the somatotropic axis has recoupled. There is evidence, however, that management and diet can influence the timing of recoupling of the somatotropic axis and the sensitivity of peripheral tissues to insulin, and gene expression differences in adipose tissue 30 d in milk confirm an effect of energy intake on lipogenic enzymes. The BCS in which a cow calves, nadir BCS, and the amount of BCS she loses postcalving are associated with milk production, reproduction, and health. Body condition score may also be a valid indicator of animal welfare, but further research is required to determine the effect of BCS and BCS change on how a cow "feels." Although the actual strength of the association may vary, there is relative consistency in the associations among calving and nadir BCS, and BCS change on milk production, postpartum anestrous, the likelihood of a successful pregnancy and days open, the risk of uterine infection, and the risk of metabolic disorders. For many production and health variables, the association with BCS is nonlinear, with an optimum calving BCS of 3.0 to 3.25 (5-point scale); lower calving BCS is associated with reduced production and reproduction, whereas calving BCS >/=3.5 (5-point scale) is associated with a reduction in early lactation dry matter intake and milk production and an increased risk of metabolic disorders. Ongoing research into the automation of body condition scoring suggests that it is a likely candidate to be incorporated into decision support systems in the near future to aid producers in making operational and tactical decisions.

Plasma samples were taken every 10 min for periods of 8 h on 3 occasions during the post-partum period from 8 cows milked twice daily (Groups M1 and M2) and from 4 cows each suckling 4 calves (Group S). All samples were assayed for LH, and ovarian activity was monitored by measurement of milk progesterone. Three of the Group M1 cows had a delayed return to ovarian activity after calving (greater than 70 days) whereas all 4 Group M2 cows resumed ovarian cycles by 25.25 +/- 3.35 days post partum. Three Group S cows resumed cycles by a mean of 47.7 days post partum while the fourth had not done so by Day 100. Mean plasma LH concentrations were low pre partum (0.67 +/- 0.05 ng/ml) and up to day 5 post partum (0.80 +/- 0.03 ng/ml, Group S; 0.90 +/- 0.12 ng/ml, Group M1; 0.80 +/- 0.25 ng/ml, Group M2). Concentrations then increased up to Day 12 (1.23 +/- 0.20, 1.66 +/- 0.16 and 1.67 +/- 0.21 ng/ml in Groups S, M1 and M2 respectively). Between Days 13 and 20 a distinct pulsatile pattern was seen in the profiles of milked but not of suckling cows. The pulse frequency was lower (approximately 2/8 h) in those milked cows in which ovarian activity was delayed and varied from 4 to 10 episodes/8 h in milked cows that commenced ovarian activity early in the post-partum period. It is suggested that the pulsatile LH pattern is a prerequisite for the onset of ovarian cycles.

No abstract

Summary. The

The control of reproductive seasonality was studied in farmed adult red deer hinds that had been either ovariectomized or ovariectomized and oestradiol-treated (s.c. implants). The breeding season, delineated by progesterone secretion in intact hind herdmates, was characterized by high (mean 0.6, range 0.1-2.5 ng ml-1 plasma) LH concentrations in ovariectomized oestradiol-treated hinds. In contrast, during the non-breeding season plasma LH concentrations in these animals were significantly lower (mean 0.1, range 0-0.9 ng ml-1 plasma). LH secretion in ovariectomized untreated hinds also displayed a marked seasonal pattern, approximately the inverse of daily photoperiod (that is, a winter peak and summer trough). The pituitary LH response to 10 micrograms exogenous GnRH was also maximal during the breeding season in ovariectomized (mean 7.4, range 1.2-14.6 ng ml-1) and ovariectomized, oestradiol-treated (mean 16.4, range 1.4-32.3 ng ml-1) hinds. These results indicate that LH secretion in the hind is regulated by both steroid-dependent and -independent mechanisms.

No abstract

No abstract

No abstract