A Demonstration Project in New York and Virginia: Retrofitting Cost-Effective Roll-over Protective Structures (CROPS) on Tractors.

The NIOSH cost-effective roll-over protective structure (CROPS) demonstration project sought to determine whether three prototype roll-over protective structures (ROPS) designed to be retrofitted on Ford 8N, Ford 3000, Ford 4000, and Massey Ferguson 135 tractors could be installed in the field and whether they would be acceptable by the intended end users (farmers). There were a total of 50 CROPS. demonstrators (25 in New York and 25 in Virginia), with 45 observers attending the New York CROPS demonstrations and 36 observers attending the Virginia CROPS demonstrations, for a total of 70 participants in New York and 61 in Virginia. The oldest retrofitted tractors were 77 to 62 years old, while the newest retrofitted tractors were 40 to 37 years old. The most frequently retrofitted tractor in the CROPS demonstration project was a Ford 3000 series tractor (n = 19; 38%), followed by Ford 4000 (n = 11; 22%), Massey Ferguson 135 (n = 11; 22%), and Ford 8N (n = 9; 18%). A major issue of CROPS retrofitting was the rear wheel fenders. The effort involved in disassembling the fenders (removing the old bolts was often faster by cutting them with a torch), modifying the fender mounting brackets, and then reinstalling the fenders with the CROPS generally required the most time. In addition, various other semi-permanent equipment attachments, such as front-end loaders, required additional time and effort to fit with the CROPS. Demonstrators were asked to rank the reasons why they had not retrofitted their tractors with ROPS until they had enrolled in the CROPS demonstration program. ROPS "cost too much" was ranked as the primary reason for participants in both states (80% for New York and 88% for Virginia). The second highest ranked reasons were "ROPS wasn't available" for Virginia (80%) and "hassle to find ROPS" for New York (69%). The third highest ranked reasons were "not enough time to find ROPS" for New York (67%) and "hassle to find ROPS" for Virginia (79%). All demonstrators and observers indicated that they were glad to have participated in the CROPS project.

Long-term growth after hypophyseal stalk transection and hypophysectomy of beef calves.

Hypothalamic hormones regulate episodic and basal secretion of hormones from the anterior pituitary gland that affect metabolism and growth in cattle. This study focused on long-term growth in young calves subjected to hypophysectomy (HYPOX), hypophyseal stalk transection (HST), and sham operation control (SOC). Cross-bred (Hereford x Aberdeen Angus) and Hereford, and Aberdeen Angus calves were HYPOX (n = 5), HST (n = 5), or SOC (n = 8) at 146 +/- 2 days of age, whereas another group was HST (n = 5) or SOC (n = 7) at 273 +/- 5 days of age. Body weight was determined every 21 days from birth to 1008 days of age. Anterior vena cava blood was withdrawn at 4-day intervals from day 64-360 for RIA of GH, TSH, T4, T3, and LH, and at 20-min intervals for 480 min to determine episodic hormone secretion. Daily feed intake was determined in HST and SOC calves during an 80-day period. Birth weight averaged 35 +/- 1 kg (+/- SE) and was 142 +/- 4 kg at 126 days and 208 +/- 8 kg at 252 days before surgery. From day 146-1008, growth was arrested (P < 0.001) in HYPOX (0.06 +/- 0.01 kg/day) compared with SOC (0.50 +/- 0.04 kg/day) calves. Growth continued but at a significantly lower rate (P < 0.05) in calves HST at 146 days (0.32 +/- 0.07 kg/day) and 273 days (0.32 +/- 0.06 kg/day) compared with SOC (0.50 +/- 0.09 kg/day). Growth continued to be impaired to 1008 days, but more so in those HST at 146 days (432 +/- 43 kg BW) than 273 days (472 +/- 5 kg BW) and less (P < 0.05) than SOC (586 +/- 37 kg BW). Daily feed intake was consistently less (P < 0.05) in HST compared with SOC calves. Although episodic GH secretion was abolished and peripheral serum GH concentration remained consistently lower in HST (2.4 ng/ml) than SOC (5.5 ng/ml; P < 0.01), the calves continued to grow throughout 1008 days. Peripheral serum TSH concentration was less (P < 0.05) HST compared with SOC calves. There was an abrupt decrease (P < 0.001) in serum T4 (4-fold) and T3 (3-fold) concentration after surgery that remained to 360 days in HST compared with SOC calves. At the time calves were killed, pituitary gland weight was markedly reduced (P < 0.001) in HST (0.18 +/- 0.01 g/100 kg BW) compared with SOC (0.54 +/- 0.03 g/100 kg BW). Histological examination of pituitary glands from HST calves indicated the persistence of secretory GH and TSH cells in the same areas of the adenohypophysis as SOC calves. Coronal sections of the gland stained with performic acid-Alcian blue-periodic acid-Schiff-orange G, revealed GH and TSH secreting cells in HST calves similar to controls. These results indicate that long-term growth continues, but at a slower rate, after hypophyseal stalk transection of immature calves in spite of complete abolition of episodic GH secretion and consistently decreased basal secretion of GH, TSH, T4, and T3 compared with sham-operated animals. Growth was abolished after hypophysectomy of immature calves in which circulating GH and TSH was undetectable.

Pregnancy, parturition, and lactation in hypophyseal stalk-transected beef heifers.

Progesterone secretion is crucial for maintaining pregnancy to parturition in mammalian species, and in cattle the corpus luteum is the primary source of this hormone. This study determined the roles of prolactin (PRL), growth hormone (GH) and luteinizing hormone (LH) in the luteotropic process in beef heifers hypophyseal stalk-transected (HST, n=7) or sham operated (sham operated controls, SOC, n=9) during midgestation. The main finding was that endogenous PRL and GH maintained progesterone secretion in HST heifers in a similar manner to that in SOC throughout pregnancy. Serum PRL averaged 37 vs 187 and GH 2 vs 4 ng/ml in HST heifers compared with SOC, whereas LH abruptly decreased to undetectable levels after HST compared with a modest 0.4 ng/ml in SOC heifers. The second finding was that parturition and lactation occurred in HST heifers with calf delivery induced to occur at the same time as SOC. Milk production in HST animals was severely limited, and postpartum estrus obliterated compared with SOC. The suckling stimulus sustained milk ejection in HST heifers in spite of diminished PRL, GH, thyroid stimulating hormone, thyroxine and tri-iodothyronine secretion. The results suggest that PRL, GH and possibly placental lactogen are luteotropic during pregnancy in cattle.

Maternal serum metabolites during prolonged starvation in pregnant pigs.

Pregnancies in pigs were sustained during periods of prolonged starvation in spite of maternal body weight losses exceeding 40 kg. Maternal stores of protein were made available for feto-placental development during starvation of the dam. Concentrations of maternal serum proteins, urea nitrogen, electrolytes, and iron were determined in sequential blood samples of healthy Yorkshire pigs during a prolonged period of 40 days inanition (water only) in either the middle third (days 30-70) or last third (days 70-110). Serum protein levels remained similar to full-diet controls throughout these two periods, whereas serum concentrations of albumin and urea N increased primarily during the last third of gestation in starved dams. Serum Na+ levels declined during prolonged inanition while Ca2+ increased and K+ remained unchanged. It was only near term that Fe2+ levels decreased in those dams starved during a period of 40 days in the last third of pregnancy. These results indicated that maternal serum components were sustained at adequate levels to maintain normal development of conceptuses during prolonged starvation in either the middle third or last third of pregnancy in the pig.

Secretion of dopamine and norepinephrine in hypophyseal portal blood and prolactin in peripheral blood of Holstein cattle.

The objective was to test the hypothesis that dopamine regulates prolactin (PRL) secretion by determining acute changes in catecholamine concentrations in hypophyseal portal blood of cattle, and their relation to peripheral blood concentration of PRL in hypophyseal stalk-transected (HST) and sham-operated controls (SOC). Holstein heifers (606 +/- 21 kg BW; mean +/- SE) were subjected to neurosurgery for 8 h to collect hypophyseal portal blood with a stainless steel cannula designed with a cuff placed under the pituitary stalk and peripheral blood via a jugular vein catheter. PRL plasma concentration was measured by radioimmunoassay, and dopamine and norepinephrine in portal plasma by radioenzymatic assay. During anesthesia before HST or SOC, PRL plasma concentration ranged from 20-40 ng/ml throughout 255 min. PRL abruptly increased and remained above 90 ng/ml after HST compared with a steady decrease to <20 ng/ml in SOC heifers throughout 440 min. Within 5 min after severing the hypophyseal stalk, dopamine in portal blood (>8 ng/ml) was significantly increased (P < 0.05) compared with peripheral blood (<2 ng/ml). Norepinephrine concentration in portal blood was significantly greater (P < 0.05) than in peripheral blood during the first 60 min. The sustained high PRL level in peripheral plasma after severing the hypophyseal stalk stimulated hypothalamic dopamine secretion from hypophyseal portal vessels during the prolonged period of blood collection. Norepinephrine concentration in these cattle was greater in hypophyseal portal than in peripheral blood, implicating both an important hypothalamic source of the catecholamine as well as an adrenal gland contribution during anesthesia.

Pituitary response to thyrotropin, corticotropin, and gonadotropin-releasing hormones in lactating cows treated with sometribove for a fourth consecutive lactation.

The effect of chronic treatment with recombinant methionyl bovine somatotropin (USAN, sometribove) on anterior pituitary secretions and its target organs was investigated in six control and six sometribove-treated British Friesian cows. Cows averaged 112 and 119 d postpartum in their fourth lactation of treatment and, except for one control, had active corpora lutea. During each lactation, treated cows received sometribove injections (500 mg) every 2 wk (injection cycle) starting 60 +/- 3 d postpartum. On Day 9 of one injection cycle, blood was sampled for 390 min, starting 30 min before an intravenous injection of thyrotropin (TRH, 0.33 microgram/kg), corticotropin (100 microgram), and gonadotropin (GnRH, 200 micrograms)-releasing hormones. Baseline somatotropin (bST) and adrenocorticotropin (ACTH) were higher in sometribove-treated cows vs. controls (3.27 vs. 1.03 ng/ml and 35.24 vs. 19.28 pg/ml, respectively). Baseline total thyroxine, free thyroxine, triiodothyronine, prolactin, follicle stimulating and luteinizing hormones, estradiol, and progesterone (P4) were similar across treatments. Circulating cortisol levels did not differ between control and sometribove cows, indicating a reduced adrenal ACTH responsiveness in the latter. Releasing factors induced similar changes across treatments in hormones studied with the following exceptions: a bST spike was seen in control cows only, cortisol response to ACTH was reduced in treated cows, and a significantly higher P4 concentration was detected in the plasma of sometribove-treated cows, suggesting increased ovarian responsiveness to GnRH-stimulated P4 output. The study demonstrated reduced bST response to TRH, consistent with physiologic feedback mechanisms, whereas the release profiles of the other pituitary hormones were unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)

Seasonal regulation of prolactin secretion in hypophyseal stalk transected beef calves.

Seasonal regulation of prolactin secretion was investigated in crossbred beef heifer calves. Calves were randomly assigned to hypophyseal stalk transection (HST, n = 6) or sham-operation control (SOC, n = 6) groups and fitted 1 day before surgery with an indwelling external jugular catheter. Prolactin (PRL), growth hormone (GH), thyroid stimulating hormone (TSH), thyroxine (T4), and tri-iodothyronine (T3) in peripheral serum were measured by radioimmunoassay in samples obtained before and after HST or SOC. During the first 8 days after HST, PRL concentrations remained significantly greater than SOC, but then decreased in both HST and SOC calves to 4 +/- 2 (+/- SE) and 10 +/- 3 ng/ml, respectively (P < 0.001). PRL remained low in both HST and SOC groups for three months after surgery. By four months, HST calves had lower basal PRL (5 +/- 1 ng/ml) than observed in SOC (40 +/- 4 ng/ml), and seasonal changes in PRL blood concentration also were attenuated by HST. Although HST reduced PRL secretion, it did not abolish the effect of seasonal changes (P < 0.01); circulating PRL concentration increased six-fold by shifts in photoperiod and temperature from winter to summer in these stalk-transected calves. The SOC group had higher serum GH during the winter (3.8 +/- 0.8) than in July (1.3 +/- 0.03 ng/ml). The HST group had the opposite profile of GH concentration, however, with concentrations being higher during May through July. Thyroid stimulating hormone secretion was partly sustained after stalk transection possibly by negative feedback of reduced circulating thyroxine and tri-iodothyronine. These results in both hypophyseal stalk-transected and sham-operated beef calves maintained in a natural environment strongly suggest that hypothalamic regulation of PRL secretion by adenohypophyseal cells is extremely sensitive to seasonal changes throughout the year. Additionally, immediately after HST, PRL blood concentration remains significantly greater than in SOC calves but eventually decreases to low blood concentration in HST calves, and unlike that seen after HST in primates. Regardless, basal PRL serum concentration responds to seasonal changes, but a less distinct change in basal GH serum concentration in HST calves than seen in the SOC calves.

Growth, puberty and reproduction in gilts born to dams deprived of nutrients during pregnancy.

Reproductive performance through two gestations was evaluated in a random selection of gilts born to dams deprived of nutrients or full-fed during pregnancy. After weaning, gilts born to dams previously subjected to inanition during the middle third or last third of gestation (O kcal/d; water only; 40 d), and those born to full-fed (7.028) kcal/d) control dams throughout gestation were raised in the same outdoor lot. At approximately 150 d of age, the gilts were observed for estrous behavior and mated at the third estrus. Age at puberal estrus was earlier (P less than .01) for gilts born to nutrient-deprived dams. Gilts from control dams exhibited first estrus at 250 d, whereas puberal estrus in gilts born to dams deprived of nutrients during the middle or last third of pregnancy occurred at 208 and 219 d, respectively. Fifteen of 18 mated gilts from the nutrient-deprived dams remained pregnant to term, compared with seven of eight gilts from control dams. Birth weights of first-parity living neonates from gilts born to nutrient-deprived dams were similar to those of newborns from controls. First-parity litter weights at birth also were similar for the experimental and control groups. Litter size at birth of first-parity living neonates averaged 7.9 piglets for gilts born to nutrient-deprived dams and was similar (P less than .05) to that for gilts from full-fed controls (9.4 piglets). Second-parity pregnancy rate, birth weight, litter weight and litter size at birth and weaning were similar for all gilts born to nutrient-deprived and control dams. These results indicate that brief segments of maternal nutrient deprivation during middle or late pregnancy have little detrimental effect on subsequent growth and reproduction of the female progeny in this litter-bearing species.

Adoption of rollover protective structures (ROPS) on U.S. farm tractors by state: 1993-1995, 2001, and 2004.

This research compares state-level rollover protective structure (ROPS) prevalence rates from the early and mid-1990s to those observed in the years 2001 and 2004. In addition, state-level ROPS prevalence rates are compared to state-level tractor overturn fatality rates. Tractor data for 1993-1995 and for 2001 and 2004 for all tractors and ROPS-equipped tractors in use on U.S. farms were derived from surveys conducted for NIOSH by the USDA-NASS. Changes in ROPS prevalence rates at the state level between the two time periods were assessed using a two-sample paired t-test with unequal sample sizes. Poisson regression was used to assess the association between ROPS prevalence rates and tractor overturn fatality rates at the state level. Overall, 49 of the 50 states had an observed increase in the percentage of farm tractors equipped with ROPS from 1993-1995 to 2001 and 2004. This increase was statistically significant for 34 states. Large shifts in ROPS prevalence were found within individual states and in clusters of states. These include a major increase in the southeastern U.S. and some western states. However, a core of states in the northeast (many of them in or near the Appalachian Mountains) through the upper midwest remain in the bottom quartile for ROPS prevalence. For the years 1992 through 2004, the highest fatality rates were observed in many of the same states that were identified previously as having persistently low ROPS prevalence rates. There is a clear relationship between low state-level ROPS prevalence rates and high state-specific tractor overturn fatality rates. While progress has been made in increasing the percentage of ROPS-equipped farm tractors, it is projected that ROPS prevalence rates will not reach a protective level nationally until after 2015. Regionally, the northeast and midwest will not reach protective levels of ROPS-equipped tractors until after 2020. Based on the adoption rates observed, tractor overturn rates will likely continue to be a more localized, but significant, public health issue for several states beyond the year 2020. The results of this study show the geographic areas of the U.S. where the greatest need exists, and where a greater emphasis should be placed on ROPS promotion activities. However, addressing this public health issue on a large scale will require resources and an organized commitment, which have historically been lacking.

Work-related fatalities in the agricultural production and services sectors, 1980-1989.

A total of 6,727 workers died of work-related injuries in the agricultural production and agricultural services sectors between 1980 and 1989, as established by data from the National Institute for Occupational Safety and Health (NIOSH) National Traumatic Occupational Fatalities (NTOF) surveillance system. The agricultural production sector accounted for the higher fatality rate (22.9 deaths per 100,000 workers), due largely to deaths caused by machinery and motor vehicles. The leading cause of death in the agricultural services sector was being struck by falling objects, primarily trees. Fatality rates were highest in the East South Central United States and lowest in the New England states. Blacks had the highest fatality rate (26.4 deaths per 100,000 workers) while workers other than white or black had the lowest rate (18.9 per 100,000 workers). Males were at higher risk of death than females, with the 65 years of age and older male group having the highest rate (60.5 deaths per 100,000 workers). Males 16-24 years of age exhibited the largest decrease in their average annual fatality rate during the 10-year period, down to 7.2 from 20.6 deaths per 100,000 workers. Possible reasons for this decrease are suggested.

Maternal starvation and progesterone secretion, litter size, and growth in the pig.

The relationships of maternal nutrition and progesterone secretion to prenatal fetal loss and neonatal survival and growth were investigated in domesticated pigs that normally experience 40% fetal loss. Yorkshire pigs were subjected to prolonged starvation (40 days; 0 kcal/day; water only) in either the middle third or last third of pregnancy and then gradually realimented to a full diet and allowed to advance to parturition; controls received a full diet (7,028 kcal/day) throughout gestation. Pregnancies were maintained in 74% of the pigs starved during either middle or late gestation compared to 100% in controls. In dams starved from days 30--70, progesterone levels remained similar to controls, but were maintained at lower levels during realimentation between days 72 and 99. Progesterone levels in dams starved days 50--90 and controls were similar from days 50 to 130. At parturition, litter size in starved dams (9.4) was similar to full-diet controls (8.0) although birth weight and neonatal growth of piglets were reduced markedly from dams starved in middle or late pregnancy. These results indicate that severe maternal nutrient deprivation during the middle or last third of gestation has little effect on ovarian progesterone secretion and is not a major limitation to fetal survival in this litter-bearing species. Maternal nutrient deprivation imposes a significant detrimental effect, however, on birth weight and neonatal growth to 80 days of age.

Nucleic acid content and growth of fetal brain, liver and heart during inanition in pigs.

Previous investigations have indicated that gilts deprived of dietary intake for periods up to 40 days are capable of maintaining pregnancy and producing offspring of normal body weight. The present experiment was designed to study the effects of inanition during middle or late pregnancy on growth and on protein and nucleic acid content of porcine fetal brain, liver and heart. Gilts were subjected to prolonged inanition (40 days; 0 kcal/day; water only) during either the middle third (Days 30-70, n = 3) or last third (Days 70-110, n = 3) of pregnancy; controls received a full diet (7028 kcal/day) until Day 70 (n = 3) or 110 (n = 3) when all dams were hysterectomized. Inanition during middle or late pregnancy had no detrimental effect on fetal brain development. Brain weight, cell size (protein/DNA ratio) and cell number (total DNA) were similar in all fetuses at Day 70 or 110. RNA concentrations at Days 70 and 110, protein concentration at Day 70 and total protein at Day 110 were higher in fetuses from starved dams than in those from controls, indicating greater protein synthetic activity in fetal brains from nutrient-deprived dams. Prolonged inanition during midpregnancy had only a limited effect on fetal liver and heart. Only liver RNA concentration and content at Day 70 differed in fetuses from starved dams; however, 40 days inanition during late gestation had marked detrimental effects. Liver weight, cell size and cell number were reduced in inanition as compared with controls by Day 110.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypothalamic deafferentation and luteinizing hormone-releasing hormone effects on secretion of luteinizing hormone in prepubertal pigs.

The control of luteinizing hormone (LH) secretion was investigated in ovariectomized, prepubertal Yorkshire pigs by comparing the effects of anterior (AHD), complete (CHD), and posterior (PHD) hypothalamic deafferentation to sham-operated controls (SOC). Gilts (n = 16) were assigned randomly to treatments, fitted with an indwelling jugular catheter, and ovariectomized 2 days before deafferentation or sham-operation (Day 0). Blood for radioimmunoassay (RIA) of LH was collected sequentially at 20-min intervals for a period of 2 h before and 24, 48, 72, and 96 h after hypothalamic deafferentation or SOC. Episodic LH release after AHD or CHD was abolished (p less than 0.01), but not after PHD or SOC. Concentrations of serum LH in AHD and CHD dropped (p less than 0.01) at 24 and 48 h after surgery. Levels of LH before and after surgery in PHD and SOC were similar (p greater than 0.05). Infusion of 25 micrograms LH-releasing hormone (LHRH) i.v. at 72 and 96 h after hypothalamic deafferentation and SOC increased (p less than 0.01) serum LH to peak levels within 15 min. after infusion; LH returned to basal levels 60-80 min later. By 96 h after surgery, LH response to LH-releasing hormone (LHRH) was less in AHD and CHD as compared with the response at 72 h postinjection. Concentrations of LH in PHD and SOC were similar (p greater than 0.05) at 72 and 96 h, respectively. The results from this study clearly indicate that neural stimuli originating or traversing the neural areas rostral to the median eminence are required for secretion of LH in the pig.(ABSTRACT TRUNCATED AT 250 WORDS)

Traumatic injuries in agriculture.

The National Coalition for Agricultural Safety and Health (NCASH) in 1988 addressed issues in agriculture and noted "a sense of urgency... arose from the recognition of the unabating epidemic of traumatic death and injury in American farming . . ." This article provides an update to the NCASH conference on traumatic injuries in agriculture, a history on how the facts and figures were arrived at for the NCASH conference, and a current report on the status of traumatic injuries in agriculture in the U.S. Fatal and nonfatal injuries are addressed along with national and regional surveillance systems. The Census of Fatal Occupational Injuries (CFOI) was used for reporting national agricultural production fatal injuries from 1992-1998 (25.8 deaths per 100,000 workers), the Traumatic Injury Surveillance of Farmers (TISF) 1993-1995 was used to report nonfatal injuries occurring nationally (7.5/100 workers), and Regional Rural Injury Studies I and II (RRIS-I and RRIS-II) were used to illustrate a regional approach along with in-depth, specific analyses. Fatality rates, which showed some decline in the 1980s, were fairly constant during the 1990s. Changes in nonfatal injury rates for this sector could not be assessed due to a lack of benchmark data. The main concerns identified in the 1989 NCASH report continue today: tractors are the leading cause of farm-related death due mostly to overturns; older farmers continue to be at the highest risk for farm fatalities; and traumatic injuries continue to be a major concern for youth living or working on U.S. farms. Fatal and nonfatal traumatic injuries associated with agricultural production are a major public health problem that needs to be addressed through comprehensive approaches that include further delineation of the problem, particularly in children and older adults, and identification of specific risk factors through analytic efforts. Continued development of relevant surveillance systems and implementation of appropriate interventions are the primary challenges for the current decade.

Use of bovine somatotropin in the tropics: the effect of sometribove on milk production in western, eastern, and southern Africa.

Seven field studies conducted in western, eastern, and southern Africa to determine the effect of a prolonged-release formulation of bovine somatotropin (bST) administered at 14-d intervals on milk production of indigenous, crossbred, and purebred cows are described. Studies in Gambia showed that 334 mg of a prolonged-release formulation of bST increased milk production of N'Dama cattle by 205 ml/d, which represented a 22% increase in milk production, and increased the body weight gain of calves. In small dairy units in Zimbabwe, 500 mg of a prolonged-release formulation of bST increased milk production of crossbreds from 8.0 to 10.0 kg/d. Milk production response of crossbred cows in Kenya increased 2.5 kg/d after the lower dose rate (334 mg); no further increases were observed when the dose rate was increased to 500 mg. A study with Holsteins showed that delaying treatment of 500 mg of a prolonged-release formulation of bST from 90 to 120 or 150 d postpartum resulted in similar milk production responses of 3.5, 3.4, and 3.2 kg/d, respectively. The milk production response (6.1 kg/d) recorded in another study with Holsteins was attributed to an excellent plane of nutrition and delayed treatment initiation. For nonpregnant cows that were classified to be culled, the prolonged-release formulation of bST was efficacious and could potentially be used to extend lactation.

Progesterone secretion and fetal development during prolonged starvation in the pig.

Roles of ovarian progesterone secretion and maternal nutrition in fetal development were investigated in a species that normally experiences considerable embryonic and fetal mortality. Pregnancies were maintained in 81% of Yorkshire pigs during prolonged starvation (e.g., 40 days; 0 kcal/day, water only) in either the middle third (days 30-70) or last third (days 70-110) of gestation compared with 100% in full-fed controls (7,028 kcal/day). In spite of severe maternal deprivation, fetal survival rates averaged 65% in starved dams and 63% in controls; mean number of living fetuses was 9.9 in starved and 9.6 in control dams. Fetal growth was reduced by maternal starvation during the middle third, but not the last third of pregnancy. Placental insufficiency was the primary cause of reduced fetal growth and resulted in abortion in a few of the dams. Progesterone in peripheral serum of dams starved either during middle or late pregnancy was maintained at levels similar (P greater than 0.05) to those in controls. Abortion occurred in starved dams only when serum progesterone concentrations dropped to less than 10 ng/ml within 3 days before loss of conceptuses.

Effect of recombinant bovine somatotropin on milk production and composition of cows with Streptococcus uberis mastitis.

The protective effect of bovine somatotropin (bST) during experimental Streptococcus uberis mastitis in cows was studied. The left quarters of 10 cows were infected with 500 cfu of S. uberis O140J. Five cows were subcutaneously treated with 500 mg of recombinant bST 7 d before and after infection, and 5 control cows received the excipient. In the treated cows, total milk production significantly increased after the first and second bST treatments. After infection, milk production decreased 24 and 40% in the infected quarters, 6 and 14% in the uninfected quarters, and 15 and 28% overall for treated and control cows, respectively. In the bST group, milk production was completely restored after 3 wk, but, in the control group, total production and the production of the infected quarters remained lower than preinfection production. The increase in somatic cell count occurred earlier and more rapidly in the control group, and the return to normal values was also more rapid in these cows. The amount of bacteria in milk was higher in the control cows. Changes in milk composition, such as lactose, protein, fat, Na+, K+, and Cl-, were significantly more pronounced in the control cows. Also, clinical symptoms were more prominent in the control cows. Somatotropin protected the mammary gland from excessive production losses and compositional changes during a subsequent episode of experimentally induced Streptococcus uberis mastitis and significantly improved the normalization of production and composition, which indicates a beneficial effect on the restoration of the integrity of the blood-milk barrier.