Plasma progesterone levels in sows with induced cystic ovarian follicles.

Large multiple cystic ovarian follicles were induced in three sows and small multiple cystic ovarian follicles were induced in three other sows by injections of adrenocorticotrophic hormone (ACTH) during the follicular phase of the oestrous cycle. Plasma progesterone levels in sows with large cysts were relatively high, while those of sows with small cystic follicles were low. Removal of the ovaries with large cysts from one sow resulted in a precipitous drop in progesterone levels indicating that the large cysts were primarily the source of progesterone. The method by which ACTH may induced cystic ovaries was also investigated. Plasma progesterone levels in two ovariectomised sows during ACTH treatment fluctuated markedly during a 24 h period achieving peak values of 4 or 5 ng/ml. The results suggest that progesterone of adrenal cortical origin may be a factor in the development of the cystic ovarian condition.     

Endocrine changes in sows exposed to elevated ambient temperature during lactation

Seven sows were placed into one of two environmental chambers at 22 C, 5 d prior to farrowing. On day 9 of lactation, one chamber was changed to 30 C (n = 4) and the other remained at 22 C (n = 3). On days 24 and 25, blood samples were collected every 15 min for 9 hr and 7 hr, respectively. On day 24, thyrotropin releasing hormone (TRH) and gonadotropin releasing hormone (GnRH) were injected iv at hour 8. On day 25 naloxone (NAL) was administered iv at hour 4 followed 2 hr later by iv injection of TRH and GnRH. Milk yield and litter weights were similar but backfat thickness (BF) was greater in 22 C sows (P less than .05) compared to 30 C sows. Luteinizing hormone (LH) pulse frequency was greater (P less than .003) and LH pulse amplitude was less (P less than .03) in 22 C sows. LH concentrations after GnRH were similar on day 24 but on day 25, LH concentrations after GnRH were greater (P less than .05) for 30 C sows. Prolactin (PRL) concentrations were similar on days 24 and 25 for both groups. However, PRL response to TRH was greater (P less than .05) on both days 24 and 25 in 30 C sows. Growth hormone (GH) concentrations, and the GH response to TRH, were greater (P less than .0001) in 30 C sows. Cortisol concentrations, and the response to NAL, were less (P less than .03) in 30 C sows. NAL failed to alter LH secretion but decreased (P less than .05) PRL secretion in both groups of sows. However, GH response to NAL was greater (P less than .05) in 30 C sows. Therefore, sows exposed to elevated ambient temperature during lactation exhibited altered endocrine function.     

Risk factors associated with cystic ovarian disease in Norwegian dairy cattle

Background

The aims of this study were to establish the incidence of cystic ovarian disease (COD) and its geographical and seasonal variation in Norway, investigate the effect of COD on culling rates, and describe the effects of COD on subsequent reproductive performance and its association to twins.

Methods

Diagnosis of COD was made by veterinary surgeons in the field. Four statistical models were made all including herd as random effect: The four different dependent variables investigated were: 1) Diagnosis of COD between 40 and 165 days in milk or not; (n = 511,657); 2) Twins or singleton; data restricted to lactations with new calving (n = 156,661): 3) Culling/removal or not (n = 573,184): 4) Culling due to reproductive problems; data included only lactations which ended in culling (n = 234,232). Model 1, 3 and 4 applied Cox regression models, and model 2 logistic regression. Independent variables were parity, twins/singletons, calving season, herd size, region, COD occurrence in present lactation (if not dependent), and COD diagnosis in previous lactation.

Results

The incidence was 0.82% per lactation. COD increased with increasing parity, was smallest at herd size between 35 and 85 cows. Cows in 1^st parity and calved in spring had lowest hazard of COD and hazard for COD diagnosis was highest in autumn with HR = 2.6 (1.9 - 3.4) compared to spring. There was an interaction between parity and season. COD incidence was lower south of 60°N. Cows which experienced COD had an increased odds of giving birth to twins OR = 2.2 (1.7 - 2.7). Of those that were culled, those with COD were culled more frequently because of reproductive problems; HR = 2.1 (1.9 - 2.3) for higher parity than 2. Having COD diagnosed in the preceding lactation was a hazard for diagnosis in the lactation studied.

Conclusion

COD diagnosis is strongly associated with season (autumn calving) and parity. Herds north of 60°N have more COD. Occurrence of COD is associated with twin births as well as culling due to reproduction.     

Selective protein loss in lactating sows is associated with reduced litter growth and ovarian function

This study was designed to test the degree of protein loss that may be sustained by lactating sows before milk biosynthesis and ovarian function will be impaired. First-parity Camborough x Canabrid sows were allocated to receive isocaloric diets (61 +/- 2.0 MJ of ME/d) and one of three levels of protein intake in lactation: 1) 878 g of CP and 50 g of lysine/d (n = 8), 2) 647 g of CP and 35 g of lysine/d (n = 7), or 3) 491 g of CP and 24 g of lysine/d (n = 10). Every 5 d during a 23-d lactation, sow live weight, backfat depth, and litter weight were recorded, and a preprandial blood sample was collected. Milk samples were collected on d 10 and 20 of lactation. Sows were slaughtered on the day of weaning, and liver and ovarian variables were measured. Lower dietary protein intakes elicited progressively larger live weight losses during lactation (-13, -17, and -28 +/- 2.3 kg; P < 0.001), but similar and minimal backfat losses (-1.3 +/- 0.29 mm). Approximately 7, 9, and 16% of the calculated body protein mass at parturition was mobilized by d 23. Lactation performance did not differ among treatments until d 20, at which time approximately 5, 6, and 12% of the calculated protein mass at parturition had been lost. The milk protein concentration on d 20 of lactation reflected the amount of body protein lost, and was lowest (P < 0.05) in sows that lost the most protein. After d 20, piglet growth rate decreased (P < 0.05) in a manner related to the amount of body protein lost. At weaning, ovarian function was suppressed in sows that had mobilized the most body protein; they had fewer medium-sized follicles (> 4 mm; P < 0.05), their follicles contained less (P < 0.01) follicular fluid, and had lower estradiol (P < 0.05) and IGF-I (P < 0.10) contents. Culture media containing 10% pooled follicular fluid (vol/vol) from high-protein-loss sows were less able to support nuclear and cytoplasmic maturation of oocytes in vitro, evidenced by more oocytes arrested at metaphase I (P < 0.05) and showing limited cumulus cell expansion (P < 0.06). Plasma insulin and IGF-I concentrations did not seem to be related to the observed differences in animal performance. Our data suggest that no decline in lactational performance or ovarian function when a sow loses approximately 9 to 12% of its parturition protein mass. However, progressively larger decreases in animal performance are associated with a loss of larger amounts of body protein mass at parturition.     

Ovarian follicular changes after weaning in sows.

Three experiments investigated ovarian follicular development in sows whose litters were weaned at 28 to 31 d of lactation. Unilateral ovariectomy near the time of weaning was used to assess early follicular characteristics and to identify those sows that would not return to estrus within 10 d after weaning. This allowed segregation of and exclusion from the study those sows that had a prolonged interval from weaning to first estrus. In Exp. 1, 82 and 72% of the large follicles that were marked at 48 or 72 h after weaning (10 sows per time point) were subsequently identified as corpora lutea. In Exp. 2, sows (seven to nine per time point) were unilaterally ovariectomized at 0, 6, 12, 18, 24, or 48 h after weaning, and follicular fluid was evaluated for changes in steroid concentrations. Progesterone concentrations in fluid from medium-sized (4 to 6 mm) follicles increased by 6 h after weaning and then declined through 24 h concomitant with increases in testosterone and estradiol. For Exp. 3, follicular fluid and granulosa cells from individual follicles were obtained from sows (seven to nine per time point) at 0, 6, and 24 h after weaning. In follicular fluid, insulin-like growth factor I (IGF-I) concentrations were not correlated (P greater than .05) with concentrations of progesterone, testosterone, or estradiol, or with granulosa cell production of estradiol during culture in androstenedione-supplemented medium.(ABSTRACT TRUNCATED AT 250 WORDS)     

Endocrine and testicular changes associated with season, artificial photoperiod, and the peri-pubertal period in stallions.

The seasonal reproductive cycle of stallions is characterized by an annual regression and recrudescence in testicular function and concentrations of LH, FSH, and testosterone in serum. Maximum reproductive capacity occurs during the increasing day lengths of spring and summer. The annual cycle in LH secretion may reflect a seasonally associated and photosensitive reduction and replenishment in pituitary content of LH. Similar to other seasonal breeders, it appears that stallions may possess an endogenous circannual rhythm in reproductive function that is subject to manipulation by altering the light:dark ratio, i.e., photoperiod. The application of a long-day photoperiod (16 hours light:8 hours dark) in December, following 20 weeks of short days (8 hours light:16 hours dark), was effective in hastening the seasonal sexual recrudescence of stallions but was not effective in prolonging the interval of heightened reproductive capacity. The infantile period in colts lasts approximately 32 weeks and is characterized by low gonadotropin concentrations and little gonadal activity. The start of the pre-pubertal period is marked by changes in the hypothalamic-pituitary axis which result in increased amounts of LH and FSH secretion between 32 and 40 weeks of age. Testosterone concentrations in serum exhibit a dramatic increase at 75 to 80 weeks of age, with puberty (defined as the age when the first ejaculate was obtained containing a minimum of 50 x 10(6) sperm with greater than or equal to 10% progressive motility) occurring at 83 weeks of age.     

Endocrine changes associated with a dietary-induced increase in ovulation rate (flushing) in gilts

Effects of an increased level of dietary energy (flushing) on plasma concentrations of FSH, LH, insulin, progesterone and estradiol-17 beta and ovulation rate were studied in 16 gilts. Gilts received 5,400 kcal ME/d for one estrous cycle and the first 7 d of a second. On d 8 of the second estrous cycle, gilts received either 5,400 kcal ME/d (control [C], n = 8) or 11,000 kcal ME/d (flushed [F], n = 8) for the remainder of the estrous cycle. Blood was collected daily at 15-min intervals for 6 h from d 8 through estrus. Gilts were examined by laparotomy 6 d after estrus. Ovulation rate was greater (P less than .05) in F than C gilts (16.0 vs 9.4). Mean daily concentrations of FSH were greater (P less than .05) in F gilts at 5 d, 4 d and 3 d prior to estrus compared with C females. In both C and F gilts, FSH decreased (P less than .05) prior to estrus. Mean daily concentrations of LH and LH pulse amplitude were not different (P greater than .05) between treatments. Mean number of LH pulses/6 h at 4 d, 3 d and 2 d prior to estrus were greater (P less than .05) in F than in C gilts. In both treatments, LH pulse amplitude decreased (P less than .05) and pulse frequency increased (P less than .07) prior to estrus. Mean plasma concentrations of insulin tended to be higher (P less than .07) in F than in C females during the 7-d period before estrus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pathological findings associated with locomotory disturbances in lactating and recently weaned sows.

Nineteen lactating or recently weaned sows that had a history of lameness, weakness or paralysis were studied at necropsy. Ten sows had osteoporosis and pathological fractures while six had lumbar vertebral osteomyelitis. Values for bone ash, specific gravity of bone and the cortical to total ratio were significantly reduced in sows with osteoporosis and pathological fractures.     

Changes in tissue composition associated with mammary gland growth during lactation in sows.

Twenty-four primiparous sows were used to determine the extent of mammary gland growth during lactation. Litter size was set to nine or 10 pigs immediately after birth. Sows were slaughtered in groups representing d 0 (within 12 h after farrowing), 5, 10, 14, 21, and 28 of lactation. Sows were provided 17.5 Mcal ME and 65 g of lysine per day during lactation. Mammary glands were collected at slaughter and trimmed of skin and extraneous fat pad. Each gland was weighed, cut in half to measure cross-sectional area, and ground for chemical analysis. Dry matter content, dry fat-free tissue (DFFT) content, protein content, amino acids composition, ash content, and DNA content were measured. Only glands known to have been suckled were included in these data. Wet and dry tissue weight; cross-sectional area; and the amount of DFFT, tissue protein, and amino acids in each suckled mammary gland increased (P < .05) during lactation to a peak on d 21. Fat percentage of each suckled gland declined (P < .05) and the percentage of protein and DFFT increased (P < .05) as lactation progressed. These results suggest that hypertrophy occurred in the tissue during lactation. There was a linear increase in the amount and percentage of DNA during lactation (P < .05), suggesting hyperplasia of the mammary tissue. Mammary tissue growth continues in suckled glands during lactation in sows, with gland wet weight increased by 55% and total gland DNA increased by 100% between d 5 and 21 of lactation.     

Protein-losing enteropathy associated with cystic mucoid changes in the intestinal crypts of two dogs

Two dogs were emaciated and hypoalbuminemic due to protein-losing enteropathy associated with a severe, focal, mucoid, cryptal ectasia of the duodenum and marked villus atrophy. In one case, diseased portions of the duodenum were obvious endoscopically and were limited to discrete, focal areas in the small intestine, with apparently more undiseased tissue than diseased tissue being present. The signs and lesions in one dog resolved after initiating combination dietary and pharmacological therapy.     

Post-partum oestrous behaviour in sows is not associated with ovulation

Sows occasionally show oestrous behaviour within 5 days of farrowing; this is termed post-partum oestrus (PPO). This study investigated the incidence and possible causes of PPO on nine Dutch farms. Lactation records (n=1374) were used, backfat thickness was measured (n=25), and ovarian condition was assessed by transrectal ultrasonography. The incidence of' PPO ranged from 0% to 62% on the different farms. On average, PPO started 59 hours after farrowing and lasted for 55 hours. Sows with PPO were younger than sows without PPO (parity 3.8 +/- 0.2 vs 4.4 +/- 0.1, respectively; P < 0. 05) and had more backfat than sows without PPO (21.3 +/- 1.2 vs 17.9 +/- 1.2 mm, respectively; P < 0.10). Occasionally, some follicle growth was observed in sows with PPO, but ovulation did not occur. PPO did not affect the weaning-to-mating interval or piglet mortality during lactation.