Y. Couture

Long-chain omega-3 fatty acids regulate bovine whole-body protein metabolism by promoting muscle insulin signalling to the Akt–mTOR–S6K1 pathway and insulin sensitivity

The ability of the skeletal musculature to use amino acids to build or renew constitutive proteins is gradually lost with age and this is partly due to a decline in skeletal muscle insulin sensitivity. Since long‐chain omega‐3 polyunsaturated fatty acids (LCn–3PUFA) from fish oil are known to improve insulin‐mediated glucose metabolism in insulin‐resistant states, their potential role in regulating insulin‐mediated protein metabolism was investigated in this study. Experimental data are based on a switchback design composed of three 5 week experimental periods using six growing steers to compare the effect of a continuous abomasal infusion of LCn–3PUFA‐rich menhaden oil with an iso‐energetic control oil mixture. Clamp and insulin signalling observations were combined with additional data from a second cohort of six steers. We found that enteral LCn–3PUFA potentiate insulin action by increasing the insulin‐stimulated whole‐body disposal of amino acids from 152 to 308 μmol kg−1 h−1 (P= 0.006). The study further showed that in the fed steady‐state, chronic adaptation to LCn–3PUFA induces greater activation (P < 0.05) of the Akt–mTOR–S6K1 signalling pathway. Simultaneously, whole‐body total flux of phenylalanine was reduced from 87 to 67 μmol kg−1 h−1 (P= 0.04) and oxidative metabolism was decreased (P= 0.05). We conclude that chronic feeding of menhaden oil provides a novel nutritional mean to enhance insulin‐sensitive aspects of protein metabolism.

Hormonal changes following an acute stress in control and somatostatin-immunized pigs

Sixteen Yorkshire pigs (49 +/- 2 kg BW at 17 weeks) were immunized against somatostatin (SRIF; 4 males, 4 females) or its conjugated protein, bovine serum albumin (BSA; controls; 4 males, 4 females). Immunizations were done at 10, 12 and 14 weeks of age. Jugular vein cannulae were surgically inserted at 17 weeks of age. Five d later, half of each sex from the control and SRIF-immunized groups were stressed. The other half were subjected to the same stress 48 hr later. On both days, remaining animals were used as unstressed controls. The stress consisted of 5 min of snare restraint. Blood samples were collected from all pigs on both days at -20, -15, -10, -5, 0 (beginning of stress), 2, 6, 10, 15, 20, 30, 40, 60, 90, 120, 150, 180 and 240 min. Samples were radioimmunoassayed for cortisol, growth hormone (GH), prolactin (Prl), insulin, triiodothyronine (T3), thyroxine (T4) and insulin-like growth factor I (IGF-I). Mean antibody titers against SRIF (1:150 dilution) at 15 weeks were 0.49 +/- .09% and 54.5 +/- 4.9% for control and SRIF immunized pigs, respectively. Gender and immunization against SRIF had no effect on any of the variables measured (P greater than 0.05), except for T3 levels which were greater in females than in males (P less than 0.05). The stress by time of sampling interaction was significant (P less than 0.01) for all hormones measured. Cortisol values almost tripled within 15 min of stress, reaching concentrations above 100 ng/mL. Maximal increases were seen at 2 min for T4 (14%), at 6 min for T3 (36%), at 15 min for Prl (46%) and at 10 min for insulin (141%). An increase of 129% in GH concentration was present at 20 min in stressed pigs; however, an increase of 97% was also seen at 120 min in control pigs. Concentrations of IGF-I decreased (21%) by 60 min in the stressed pigs and remained depressed for up to 150 min. Stress associated with snare restraint, therefore, induces major changes in the concentrations of a series of hormones in growing pigs. On the other hand, immunization against SRIF did not alter any of the hormonal profiles measured. Since snare restraint is widely used to handle pigs during jugular puncture, any study of hormonal secretion in this species should be carried out under carefully controlled conditions in terms of blood sampling technique.

Serum growth hormone release during a 60-hour period in growing pigs

Growth hormone (GH) profiles were measured during a 60-hour period in four castrated male and five female, 20-week-old Yorkshire pigs. During this period, GH release was not affected by feeding when measured at 2, 4 and 8 hr before and after feeding time. A photoperiod of 12 hr light and 12 hr darkness produced a decrease (P less than .05) in baseline mean GH levels from 4.0 to 3.5 ng/ml during periods of darkness. This effect was observed in both genders. Females and castrated males exhibited (P greater than .05) similar baseline GH levels and identical numbers of GH peaks during feeding and photoperiod studies. However, during these periods, the amplitude of the GH peaks and areas under the GH curves were greater (P less than .05) in females. These results indicate that: 1) feeding did not influence GH secretion; 2) darkness produced a decrease in the baseline GH levels in both sexes; and 3) females secreted more GH than castrated males of the same age.

Description of cow-calf productivity in Northwestern Quebec and path models for calf mortality and growth

Abstract A random sample of 651 assumed-pregnant cows was drawn from 26 randomly selected beef herds in Northwestern Quebec, Canada. The cows were followed with their calves (n = 568) for one production period. Data were collected on calving conditions, calf mortalities, and the presence of diarrhea and pneumonia in calves during the first 2 weeks of life. The calves were weighed and measured for withers height, at 3–4 weeks of age and at the weaning (median of 203 days of age). Cow-calf productivity was described and two path models were built, one for calf mortalities and the other for calf growth. The percentage of weaned calves was 78.8%, the risk of perinatal mortality, within 24 h of birth, 4.4%, and the risk of neonatal mortality, from 24 h to 30 days of age, 7.7%, were estimated. The mean 200 day weight (adjusted for sire breed) was 217 kg for female calves and 232 kg for male calves. Birth with assistance and birth between December and March (versus in April or May) were associated with an increased risk of dying during the perinatal period; birth in a maternity pen was associated with a decreased risk of perinatal mortality. The presence of diarrhea or pneumonia during the first 2 weeks of life was associated with an increased risk of dying between 24 h and 30 days of age and with a decreased achieved growth at 30 days without a subsequent full compensatory gain at the weaning.

Regulation of glucose and protein metabolism in growing steers by long-chain n-3 fatty acids in muscle membrane phospholipids is dose-dependent

A previous study showed that long-chain n-3 polyunsaturated fatty acids (LCn-3PUFA; >18 carbons n-3) exert an anabolic effect on protein metabolism through the upregulation of insulin sensitivity and activation of the insulin signaling pathway. This study further delineates for the first time whether the anabolic effect of LCn-3PUFA on metabolism is dose responsive. Six steers were used to test three graded amounts of menhaden oil rich in LCn-3PUFA (0%, 2% and 4%; enteral infusions) according to a double 3 × 3 Latin square design. Treatment comparisons were made using iso-energetic substitutions of control oil for menhaden oil and using 6-week experimental periods. The LCn-3PUFA in muscle total membrane phospholipids increased from 8%, 14% to 20% as dietary menhaden oil increased. Feeding graded amounts of menhaden oil linearly decreased plasma insulin concentration (49, 35 and 25 μU/ml, P = 0.01). The insulin-stimulated amino acid disposal rates as assessed using hyperinsulinemic-euglycemic-euaminoacidemic clamps (20, 40 and 80 mU/kg per h) were linearly increased by the incremental administrations of menhaden oil from 169, 238 to 375 μmol/kg per h (P = 0.005) during the 40 mU/kg per h clamp, and from 295, 360 and 590 μmol/kg per h (P = 0.02) during the 80 mU/kg per h clamp. Glucose disposal rate responded according to a quadratic relationship with the incremental menhaden oil amounts (P < 0.05). A regression analysis showed that 47% of the amino acid disposal rates elicited during the hyperinsulinemic clamp was related to muscle membrane LCn-3PUFA content (P = 0.003). These results show for the first time that both protein and glucose metabolism respond in a dose-dependent manner to menhaden oil and to muscle membrane LCn-3PUFA.

Castration and testosterone effects on endogenous and somatocrinin-induced growth hormone release in intact and castrated male pigs☆

Growth hormone (GH) release is influenced mainly by two hypothalamic factors, growth hormone-releasing factor (GRF) and somatostatin and is modulated by other hormones such as gonadal steroids. The objective of this study was to determine if castration (CA) and exogenous testosterone (TE) affect endogenous and GRF-induced GH release. Purebred Yorkshire male pigs (n = 32) were assigned to one of the following treatments: T1:CA; T2:CA +/- TE; T3: intact (IN); T4: IN +/- TE, in a 2 x 2 factorial design. Piglets were castrated at 3 days of age. Testosterone propionate (1.0 mg/kg) in sesame oil (2 ml) or sesame oil alone was injected sc SID during a 10-day period before each sampling day at 9, 15 and 21 weeks of age. Jugular blood samples were collected for a 6-hr period preceding and following iv injection of hGRF (1-29)NH2 (10 micrograms/kg). These procedures were repeated at 9, 15 and 21 weeks of age. The overall mean GH levels and the area under the GH peaks before and after GRF stimulation were lower (P less than .05) in castrated animals than in intact animals. Testosterone treatment increased (P less than .05) circulating TE levels and increased the amplitude of the endogenous GH peaks but did not affect (P greater than .05) the GRF-induced GH release. Increasing age produced a marked reduction of the amplitude of the GH peaks, the area under the GH peaks, the baseline mean and the overall mean GH levels during the 6-hr period preceding GRF injection. The present data support the hypothesis that castration in pigs reduces circulating and GRF-induced GH release. Exogenous testosterone for 10 days did not stimulate endogenous or GRF-induced GH release with the exception of the amplitude of the endogenous GH peaks.

Milk flow obstruction caused by varicose vein of the teat in dairy cattle.

Objective To describe varicose vein as a cause of obstruction of the teat cistern in dairy cattle and to report therapeutic options and outcome. Study Design Retrospective case series. Animals Dairy cows (n = 22). Methods Medical records (1998–2011) of dairy cows admitted for milking difficulties caused by a teat varicose vein were reviewed. Three treatment approaches were used: sclerotherapy, ligation of the vein associated with sclerotherapy, and phlebectomy. Long-term outcome was obtained ≥6 months after treatment and defined as a milking improvement. Descriptive statistics were used to determine the population at risk and a chi square test was used to evaluate the relationship between treatments and outcomes. Results Twenty-four teats (22 cows) had a varicose vein. Forequarters were more frequently affected than rear quarters (P < .01). Three sclerotherapies, 12 ligations associated with sclerotherapy and 6 phlebectomies were performed. Five veins were not treated. Overall prognosis with treatment was good (84%) at ≥ 6 months and was not significantly different between treatment types (P = .38). Recurrence of the obstruction by the varicose vein occurred in 3 of 19 teats. Conclusions and clinical relevance Several surgical options are available for treatment of teat varicose veins. The overall prognosis of return to normal milking is good.OBJECTIVE To describe varicose vein as a cause of obstruction of the teat cistern in dairy cattle and to report therapeutic options and outcome. STUDY DESIGN Retrospective case series. ANIMALS Dairy cows (n = 22). METHODS Medical records (1998-2011) of dairy cows admitted for milking difficulties caused by a teat varicose vein were reviewed. Three treatment approaches were used: sclerotherapy, ligation of the vein associated with sclerotherapy, and phlebectomy. Long-term outcome was obtained ≥ 6 months after treatment and defined as a milking improvement. Descriptive statistics were used to determine the population at risk and a chi square test was used to evaluate the relationship between treatments and outcomes. RESULTS Twenty-four teats (22 cows) had a varicose vein. Forequarters were more frequently affected than rear quarters (P < .01). Three sclerotherapies, 12 ligations associated with sclerotherapy and 6 phlebectomies were performed. Five veins were not treated. Overall prognosis with treatment was good (84%) at ≥ 6 months and was not significantly different between treatment types (P = .38). Recurrence of the obstruction by the varicose vein occurred in 3 of 19 teats. CONCLUSIONS AND CLINICAL RELEVANCE Several surgical options are available for treatment of teat varicose veins. The overall prognosis of return to normal milking is good.

Milk flow obstruction caused by varicose vein of the teat in dairy cattle: Varicose Vein of the Teat in Dairy Cattle

Objective To describe varicose vein as a cause of obstruction of the teat cistern in dairy cattle and to report therapeutic options and outcome. Study Design Retrospective case series. Animals Dairy cows (n = 22). Methods Medical records (1998–2011) of dairy cows admitted for milking difficulties caused by a teat varicose vein were reviewed. Three treatment approaches were used: sclerotherapy, ligation of the vein associated with sclerotherapy, and phlebectomy. Long-term outcome was obtained ≥6 months after treatment and defined as a milking improvement. Descriptive statistics were used to determine the population at risk and a chi square test was used to evaluate the relationship between treatments and outcomes. Results Twenty-four teats (22 cows) had a varicose vein. Forequarters were more frequently affected than rear quarters (P < .01). Three sclerotherapies, 12 ligations associated with sclerotherapy and 6 phlebectomies were performed. Five veins were not treated. Overall prognosis with treatment was good (84%) at ≥ 6 months and was not significantly different between treatment types (P = .38). Recurrence of the obstruction by the varicose vein occurred in 3 of 19 teats. Conclusions and clinical relevance Several surgical options are available for treatment of teat varicose veins. The overall prognosis of return to normal milking is good.OBJECTIVE To describe varicose vein as a cause of obstruction of the teat cistern in dairy cattle and to report therapeutic options and outcome. STUDY DESIGN Retrospective case series. ANIMALS Dairy cows (n = 22). METHODS Medical records (1998-2011) of dairy cows admitted for milking difficulties caused by a teat varicose vein were reviewed. Three treatment approaches were used: sclerotherapy, ligation of the vein associated with sclerotherapy, and phlebectomy. Long-term outcome was obtained ≥ 6 months after treatment and defined as a milking improvement. Descriptive statistics were used to determine the population at risk and a chi square test was used to evaluate the relationship between treatments and outcomes. RESULTS Twenty-four teats (22 cows) had a varicose vein. Forequarters were more frequently affected than rear quarters (P < .01). Three sclerotherapies, 12 ligations associated with sclerotherapy and 6 phlebectomies were performed. Five veins were not treated. Overall prognosis with treatment was good (84%) at ≥ 6 months and was not significantly different between treatment types (P = .38). Recurrence of the obstruction by the varicose vein occurred in 3 of 19 teats. CONCLUSIONS AND CLINICAL RELEVANCE Several surgical options are available for treatment of teat varicose veins. The overall prognosis of return to normal milking is good.

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...