P. Brazeau

Mammary gland development of sows injected with growth hormone-releasing factor during gestation and(or) lactation

Twenty-four gilts received s.c. injections of saline or growth hormone-releasing factor (GRF) in late gestation and(or) lactation. Sows were sacrificed on day 30 of lactation and functional mammary glands were excised for chemical analyses. Weight of parenchymal (P = 0.004) and extra-parenchymal tissues (P = 0.002) were decreased with GRF injections during lactation. Parenchymal mass per milligram of DNA also decreased (P = 0.025) with GRF in lactation while parenchymal DNA concentration increased (P = 0.03). Exogenous GRF given to sows during lactation therefore decreased total parenchymal mass, increased cell density and decreased mammary cell size. Key words: Sow, mammary gland, growth hormone-releasing factor

Effect of hypothalamic factor treatments on the behaviour of sows during lactation and on their behavioural and cortisol responses to weaning

Abstract The effects of daily treatments between Days 5 and 25 of lactation with growth hormone-releasing factor (GRF: 20 μg kg −1 ) and thyrotropin-releasing factor (TRF: 1 or 9 μg kg −1 ) on the behaviour of 51 primiparous lactating sows and on their behavioural and cortisol response to weaning management were studied in two experiments that differed by the weaning techniques (piglets removed, sow removed) and the dose of TRF. The sows were observed for 24 h on Days 17, 27 and 28 (weaning) of lactation. During lactation, the sows receiving TRF alone or in combination with GRF spent a greater proportion of time in lateral recumbency than the control and the GRF-treated animals, in both experiments. We suggest that this difference reflects a stimulation of maternal behaviour. In Experiment 1 (piglets removed), there were no residual treatment effects on sow behaviour on the day of weaning. However, after weaning in Experiment 2 (sow removed), the GRF- and TRF-treated sows spent a greater proportion of time in sternal recumbency and agitation behaviour and a lower proportion in lateral recumbency and had a smaller increase in cortisol levels than the control and GRF+TRF-treated sows. These results suggest that hypothalamic factor treatments may not have detrimental effects on the lactating sows behaviour, but that they can modify the sows response to stressors. In fact, the GRF and the TRF sows appear to have had a greater behavioural and a lesser cortisol response to weaning.

Effect of long-term administration of human growth hormone-releasing factor and(or) thyrotropin-releasing factor on milk production, insulin-like growth factor-I and plasma constituents in dairy cows

Forty-seven Holstein cows (51 ± 7 d of lactation; 607 ± 78 kg BW) were randomly subjected to a 2 × 2 factorial arrangement based on milk production. Milk production and feed intake were recorded every day and milk and feed composition determined once a week for 33 wk (4 wk preinjection, 26 wk of injection and 3 wk postinjection). During the injection period, cows received daily s.c. injections (10:00 h) in the cervical area of saline (control), human growth hormone-releasing factor (1–29)NH2 (GRF; 10 μg kg−1 BW), thyrotropin-releasing factor (TRF; 1 μg kg−1 BW) or the combination of both releasing factors (10 and 1 μg kg−1 BW, respectively). Growth hormone-releasing factor enhanced milk production (P   0.25) or average daily weight gain (P > 0.25). Thyrotrop...