The relationship of changes in mammary blood flow and plasma progesterone at the time of parturition in the ewe

Bioinformatics and Gene Network Analyses of the Swine Mammary Gland Transcriptome during Late Gestation

We used the newly-developed Dynamic Impact Approach (DIA) and gene network analysis to study the sow mammary transcriptome at 80, 100, and 110 days of pregnancy. A swine oligoarray with 13,290 inserts was used for transcriptome profiling. An ANOVA with false discovery rate (FDR < 0.15) correction resulted in 1,409 genes with a significant time effect across time comparisons. The DIA uncovered that Fatty acid biosynthesis, Interleukin-4 receptor binding, Galactose metabolism, and mTOR signaling were among the most-impacted pathways. IL-4 receptor binding, ABC transporters, cytokine-cytokine receptor interaction, and Jak-STAT signaling were markedly activated at 110 days compared with 80 and 100 days. Epigenetic and transcription factor regulatory mechanisms appear important in coordinating the final stages of mammary development during pregnancy. Network analysis revealed a crucial role for TP53, ARNT2, E2F4, and PPARG. The bioinformatics analyses revealed a number of pathways and functions that perform an irreplaceable role during late gestation to farrowing.

Endocrine and metabolic factors involved in the effect of nutrition on the production of colostrum in female sheep

We investigated the physiological relationship between diet during pregnancy and colostrum production in ewes to test the hypothesis that for ewes that are in low body condition, with low fat reserves, the food supply will be the main source of energy for colostrum synthesis. To this end, we measured the amount of colostrum accumulated by ewes under two levels of nutrition. We also measured the circulating concentrations of metabolites and hormones associated with lactogenesis (beta-hydroxybutyrate, glucose, progesterone, prolactin, cortisol, growth hormone, leptin, insulin and insulin-like growth factor-I) Ewes were either under-fed at 70 (n = 15) or well-fed at 110% (n = 10) of their daily metabolisable energy requirement during the last two months of pregnancy. Colostrum accumulation up to parturition was 168 +/-48 g for under-fed ewes and 451 +/-103 g for well-fed ewes. After birth, under-fed ewes produced less colostrum than well-fed ewes but the difference was no longer significant. The level of nutrition also influenced the plasma concentrations of hormones and metabolites related to lactogenesis. Progesterone concentrations decreased before lambing in all animals but in under-fed ewes the fall appeared to be too small to initiate the onset of colostrum production. Beta-hydroxybutyrate concentrations were higher in under-fed than in well-fed ewes, suggesting that the under-fed ewes were mobilising more adipose tissue but they still did not meet their ME requirements for colostrum production. We concluded that, in underfed ewes, there are insufficient nutrients for adequate lactation and the hormone regime is inappropriate for good udder development and colostrum synthesis.

Colostrum production and hormone responses of parturient ewes fed varying amounts and types of supplement

Low perinatal lamb loss and fast lamb growth rates are important measures for efficient sheep production. To understand the role of ewe nutrition in late pregnancy, 100 adult Border Leicester × Merino ewes were joined at a synchronised oestrus. Ewes were nutritionally managed to maintain maternal body condition until day 130 of pregnancy at which time 50 twin-bearing ewes entered single pens. Thirteen ewes were allocated as controls and 14, 11 and 12 ewes for the 3 treatments groups. All were fed a base diet of lucerne hay (17.3% crude protein; 9.4 MJ ME/kg DM). Three of the 4 treatment groups were supplemented with oaten grain, formaldehyde-treated sunflower meal or lupin grain at 1 of 3 nominal feeding levels: 250, 500 or 750 g/ewe.day of supplement. Actual intake was less than amounts offered. Intakes measured in the final 5 days prepartum, were used in the analysis. Data were collected on peripheral progesterone and insulin-like growth factor-1 at 4 days prepartum and 50 min postpartum; peripheral oestrone sulfate at 4 and 3 days prepartum and 50 min postpartum; and colostrum weight and score at 50 min postpartum. Feeding level of supplement, but not type of supplement, significantly increased insulin-like growth factor-1 and decreased progesterone and oestrone sulfate levels. Correlations of energy and nitrogen intake with insulin-like growth factor-1, progesterone and oestrone sulfate levels were positive (P<0.01), as were the correlations of colostrum weight with these traits. An unexpected high correlation between energy and nitrogen intake masked any differential effects on colostrum production and hormone response. Nevertheless, the supply of energy and protein supplements were associated with elevated colostrum weights and scores, and lower progesterone concentration. Lowering progesterone levels is considered necessary for successful parturition. Oaten grain was the least desirable grain supplement. These observations support the practical importance of providing adequate nutrition in late pregnancy and its effect on colostrum yield and presumably lamb survival and growth.

Nutrition and colostrum production in sheep. 2. Metabolic and hormonal responses to different energy sources in the final stages of pregnancy

Lupins and maize, with similar concentrations of metabolisable energy, should produce similar responses in colostrum production at parturition when fed during the last week of pregnancy, but, in the present study, we tested the proposal that the physical form of whole lupins would restrict intake and, therefore, the response compared with cracked lupins or maize. Fifty-five twin-bearing ewes were divided into four groups: in the last 15 days of pregnancy, 14 were fed whole lupins, 13 were fed cracked lupins, 14 were fed cracked maize and 14 received no supplement. The cracked supplements were fed in increasing amounts for 6 days to avoid acidosis. The whole lupins were fed only from Day −8. All supplementary grains increased the intake of metabolisable energy by >35%, but only ewes eating maize accumulated significantly more colostrum at parturition: control, 207 g; cracked maize, 452 g; cracked lupins, 206 g; whole lupins, 231 g (P < 0.05). Plasma urea concentrations were extremely high (approximately 10 mmol L–1) for both groups eating lupins and approximately double those of control ewes or those receiving maize (P < 0.05). We conclude that gut distention is not a cause of a poor response to lupins, but the ammonia associated with near-toxic concentrations of plasma urea may be affecting the production of colostrum.

The effect of diet in late pregnancy on progesterone concentration and colostrum yield in ewes

In the ewe, high level feeding is associated with low levels of circulating progesterone and that progesterone withdrawal is a prerequisite for lactogenesis and the onset of copious milk secretion. A total of 108 ewes was allocated to a 3 x 2 factorial experiment to determine the effect of diet on serum progesterone (P4) concentration and colostrum yield. On D 96 of pregnancy, the ewes were offered either grass silage, molassed sugar beet pulp (beet pulp) silage or grass silage supplemented with beet pulp. All ewes were given ad libitum access to silage. From D 126 of pregnancy, half the diets were supplemented with soybean meal with the aim of achieving a total crude protein intake of 220 g/ewe/day. Blood samples were taken on D 142 of pregnancy and at 1, 10 and 18 h post lambing for P4 determination. Metabolizable energy intakes (Mega Joules/ewe/day) of 9.1, 11.2 and 12.1 (SEM 0.37) and crude protein intakes (g/ewe/day) of 142.8, 167.4 and 162.0 (SEM 3.46) were recorded for grass silage, beet pulp ensiled and beet pulp supplemented silages, respectively, from D 126 to D 147 of pregnancy. Soybean meal supplementation increased the crude protein intake from 97.1 to 217.0 g/ewe/day (SEM 2.86) and Metabolisable Energy intake from 9.0 to 12.6 Mega Joules/ewe/day (SEM 0.31). Supplementation with soybean meal decreased P4 concentration (ng/ml) on D 142 (P < 0.05) and at 1 h (P < 0.01), 10 h (P < 0.01) and 18 h post lambing (P < 0.01). Ewes offered grass silage had higher P4 concentrations on D 142 (P < 0.01) and at 1 h after lambing (P < 0.05) than the beet pulp-supplemented ewes. There were negative linear relationships between P4 concentration at D 142 and colostrum yield at 1 h (P < 0.01) and between P4 concentration at 1 h and colostrum yield at 1 h (P < 0.001) and total yield at 18 h (P < 0.001). In conclusion, ewes which were underfed had higher P4 concentrations at all times, and there were negative linear relationships between colostrum yield and P4 concentrations on D 142 of pregnancy and at 1 h post lambing.

The effect of medroxyprogesterone acetate on premature labor in the sheep

The ability of medroxyprogesterone acetate to delay premature delivery was investigated in nine chronically catheterized pregnant sheep (125 to 130 days' gestation). Catheters were placed for measurement of intrauterine pressure and uterine vein concentrations of progesterone, 17 beta-estradiol, and 15-keto-13,14-dihydroxyprostaglandin F2a. Premature parturition was induced in all animals by infusion of dexamethasone (1 mg/24 hours) to the fetus. Three ewes served as controls, three ewes received oral medroxyprogesterone acetate (5 mg/kg/day) 48 hours prior to the start of and during dexamethasone (early medroxyprogesterone acetate), and the remaining three animals received oral medroxyprogesterone acetate 12 hours after the onset of dexamethasone infusion (late medroxyprogesterone acetate). The lengths of time from dexamethasone until the onset of labor and from dexamethasone until delivery were compared, and were significantly longer for each group compared to control times. Of all endocrine events analyzed, the fall in plasma progesterone was the most consistent in all groups, showing that animals with rapid falls in progesterone levels (control group) tended to deliver earlier. These results demonstrate that medroxyprogesterone acetate can delay premature parturition in the sheep. Also medroxyprogesterone acetate appears to delay the endocrinologic events that normally occur at this time.

Mammary blood flow regulation in the nursing rabbit

Cardiac output and mammary blood flow distribution prior to and after suckling were studied in 10 nursing rabbits by means of radionuclide-labeled microspheres. Suckling was followed by a 5.8% rise in cardiac output and a 20.4% rise in mammary blood flow. Determinations of intraglandular blood flow distribution have shown that there was a 43% increase in blood flow to the glands suckled from as compared to a 22.7% rise to the contralateral untouched glands and a 4.9% rise in the remainder of untouched glands. The conclusion is that a local mechanism may be involved in the regulation of mammary blood flow in the nursing rabbit.