Continuous Suckling Research Articles

PSVII-25 Utilization of a Small Ruminant Model for Teaching/ Learning Scientific Approaches to Nutritional and Reproductive Management

Abstract This study used Spanish Kiko goats as a small ruminant model (SRM) for teaching animal science courses via experiential laboratory-based methods at a small liberal arts college in the Southeastern United State. Perceivably, the SRMs presents an accessible and sustainable teaching tool for undergraduate education at institutions with limited resources, such as cattle facilities. The use of mature (> 3 years old) bucks (male model 1, 2 & 3), does (female model 1 & 2), and kids (kid model 1, 2, 3; 8 months old) as SRMs in 4 courses and resultant learning is reported herein. SRMs were fed, late weaned, and continuously bred to simulate the nutritional and reproductive management practiced in rotationally grazed strictly forage-fed cattle. Growth performances amongst bucks (pre and post pubertal; Figure 1), does (pre- and post-partum Figure 2), and kids (pre and post weaning Figure 3) were recorded and analyzed. Feed intake trials (Figures 4 and 5), fecal analysis, and apparent DMD were conducted. The benefits of continuous suckling and postweaning management of does and kids were realized as 100% of does and kids successfully transited each breeding period. In addition, kids approached market weights (15.53 kg) at 136 days postpartum (Figure 3) and does were rebred at first postpartum estrus (62 days). The use of pre-breeding season reproductive tract examinations via ultrasound and BSE in female and male SRMs enabled effective evaluations of the poor reproductive performance of the cattle herd (59.3% pregnancy rate in 2022). The use of SRMs allowed for learning ruminant gastrointestinal and reproductive system physiology. Subsequently, comprehension of the impact of mineral and vitamin deficiencies on the annually declining reproductive performance of rotationally grazed cattle was enhanced. Conclusively, the use of SRMs supported my learning and is recommended for teaching/learning in animal sciences at institutions with limited resources.

Knowledge and Attitude of Postpartum Complications in Lebanese Women

Background: Poor knowledge and attitude of postpartum complication (KAPC) among women delays their management and increases Maternal Mortality Ratio (MMR).1 MMR in Lebanon increased from 24 deaths per 100,000 live births in 2005 to 29 in 2017.2 This study aims to assess the perceived KAPC of Lebanese women and how it differs according to their level of education and age groups, in different regions in Lebanon. Methods: This community-based cross-sectional study was conducted among 500 women aged 17-50 years old from 2018 to 2020 regardless of having children or not. A questionnaire was developed, and its internal validity was found to be within the acceptable range (Richard's Kurdson = 0.75). The questionnaire was translated from English to Arabic and administered for data gathering through face-to-face interviews. Chi-square and ANOVA were applied to identify the statistical difference. A confidence interval of 95% was reported, and statistical significance was declared at p < 0.05. Results: The majority of women who regarded proteins and dairy products as essential are those living in Beirut [p = 0.020] [0.019]. Women who attended university demonstrated more knowledge of alarming urinary tract infection symptoms than those who attended secondary or high school level [p = 0.05]. Females living in Beirut knew better about deep vein thrombosis symptoms than those living in the South and Nabatieh [p = 0.047] (Table 1). Regarding the best method for breast emptying, 64.8% of women aged 36-50 chose continuous suckling compared to 47.2% of females aged 18-25 year-old (Table 2). Conclusion: KAPC among Lebanese women is distinct from one complication to another, and this is influenced directly or inversely by mainly the effect of the Lebanese geographical regions and educational level. Therefore, an awareness campaign must be implemented at several levels, targeting the most distant regions, especially the rural ones like Beqaa, and vulnerable age groups, particularly the young.

Suckling and Excess Fat in the Postpartum Reproductive Activity of Hair Sheep

Objective: To evaluate the effect of excess fat and suckling control on postpartum reproductive activity of hair ewes. Design/Methodology/Approach: Eighty-one (81) hair ewes with average weight of 58±8 kg were used, which on postpartum day 7 were assigned to one of four treatments under a completely randomized design with 2×2 factorial arrangement. Factor A is the type of suckling [continuous suckling (CS) and suckling control (SC)] and factor B, excess fat (with or without). In CS, ewes remained with their offspring 24 hours a day (n=16). In continuous suckling plus fat (CSF), ewes remained with the offspring all day plus the addition of 8% in dietary fat (n=24). In SC, it was 30 min of suckling only twice per day (n=14). In suckling control plus fat (SCF), controlled suckling lasted 30 min, twice a day plus 8% fat (n=25). Results: The response to the treatments was similar (p > 0.05) in onset of estrus, return rate, gestation, prolificacy and fertilization; for the lambing rate variable, there were differences (p ≤ 0.05), the SCF treatment was higher (68%) compared to CS (50%) and CSF (50%), but equal (p < 0.05) to SC (57.1%). Implications: In this experiment, it was observed that the SCF treatment presented a better response, implying that controlling suckling and providing excess fat helps to restore ovarian activity sooner after lambing. Conclusions: Suckling control plus inclusion of dietary excess fat in ovulation induction protocols during early postpartum (around day 25 postpartum) can be included in routine reproductive management of flocks, improving the reproductive efficiency of hair sheep.

Kisspeptin Stimulates the Pulsatile Secretion of Luteinizing Hormone (LH) during Postpartum Anestrus in Ewes Undergoing Continuous and Restricted Suckling.

Simple SummaryOne of the major impediments to improving the efficiency of sheep production systems is the difficulty of breeding the females before their young are weaned. A major physiological barrier is suckling, because it prevents the initiation of a new reproductive cycle by inhibiting the pulsatile secretion of gonadotropin-releasing hormone (GnRH) and thus the secretion of LH pulses. It has now become clear that, at brain level, the secretion of GnRH is controlled primarily by the neuropeptide kisspeptin (Kp), a central player in the ‘KNDy’ system that generates GnRH pulses. Here, we report that intravenous administration of Kp stimulates pulsatile LH secretion in ewes during postpartum anestrus. Moreover, the response was greater when suckling was restricted to 30 min twice a day. We conclude that kisspeptin application increases pulsatile LH secretion in suckling ewes, suggesting that suckling inhibits ovulation by reducing the activity of kisspeptin neurons.This study tested whether the intravenous application of kisspeptin can stimulate the pulsatile secretion of LH in suckling ewes during postpartum anestrus. Ten days after lambing, Pelibuey ewes were allocated among two groups: (1) continuous suckling (n = 8), where the lambs remained with their mothers; and (2) restricted suckling (n = 8), where the mothers suckled their lambs twice daily for 30 min. On Day 19 postpartum, the ewes were individually penned with ad libitum access to water and feed and given an indwelling catheter in each jugular vein. On Day 20, 4 mL of blood was sampled every 15 min from 08:00 to 20:00 h to determine LH pulse frequency. At 14:00 h, four ewes in each group received 120 μg of kisspeptin diluted in 3 mL of saline as a continuous infusion for 6 h; the remaining four ewes in each group received only saline. The interaction between kisspeptin and suckling type did not affect LH pulse frequency (p > 0.05). Before kisspeptin administration, pulse frequency was similar in all groups (1.50 ± 0.40 pulses per 6 h; p > 0.05). With the application of kisspeptin, pulse frequency increased to 3.50 ± 0.43 pulses per 6 h (p ≤ 0.014), so the concentration of LH (1.11 ± 0.14 ng mL−1) was greater in kisspeptin-treated ewes than in saline-treated ewes (0.724 ± 0.07 ng mL−1; p ≤ 0.040). The frequency of LH pulses was greater with restricted suckling than with continuous suckling (2.44 ± 0.29 versus 1.69 ± 0.29 pulses per 6 h; p ≤ 0.040). We conclude that intravenous application of kisspeptin increases the pulsatile secretion of LH in suckling ewes and that suckling might reduce kisspeptin neuronal activity, perhaps explaining the suppression of ovulation. Moreover, the effects of kisspeptin and suckling on pulsatile LH secretion appear to be independent, perhaps operating through different neural pathways.

THE COMBINED EFFECT OF SUCKLING SYSTEM AND WEANING WEIGHT ON MILK TRAITS OF NATIVE SHEEP

Data of the current stud, were collected on 32 Iraqi native sheep aged 2-5 years maintained on commercial flock. At lambing, the 32 ewes were divided into two equal groups, lambs in the 1st group were left with their dams till weaning and then were milked twice daily till they dry off (Continuous), whereas the 2nd group, lambs were separated at night for 12 hr. and the ewes were milked once daily at morning (Restricted). Then each main group was subdivided into two group to be weaned their lambs when they reached 3 or 4 times of their birth weight (WB1 and WB2). Results revealed that ewes of restricted suckling produced significantly (P < 0.05) more post weaning (80.80 vs.49.44 L), total milk yield (135.01 vs. 109.94 L) and sealable milk (99.86 vs. 49.44 L) and had significantly longer lactation period (169.3 vs. 140.2 days) compared ewes in continuous suckling. Also, results obtained indicate that daily gain in weight averaged 0.23 kg from birth to weaning and from birth to marketing and 0.24 kg from weaning to marketing and neither suckling system nor weaning weight affected these trait significantly. It can be concluded that restricted suckling resulted in an increase in sealable milk without any adverse effect on growth of lambs.

Short- and long-term effects of temporary early cow–calf separation or restricted suckling on well-being and performance in zebu cattle

Information on weaning techniques in the tropics is scarce, particularly regarding the long-term effect of temporary early cow–calf separation or restricted suckling. Therefore, we studied the effects of these two handling practices on well-being and performance at 150 days postpartum in fifteen zebu cow–calf pairs randomly assigned to three treatments. Continuous suckling (CS) where calves remained with their dams from birth to weaning; restricted suckling (RS) calves were allowed to suckle 30 min/day from Day 34 until weaning at Day 150 and kept separated the rest of the time; temporary separation (TS) calves were separated for 72 h from their dams from Day 33 to 36 but remained with their dams the rest of the time. Blood samples and behavioral data were collected on Days 32–36 (1st period) and 149–153 (2nd period). In the 1st period, a greater percentage of RS and TS calves were observed close to the fence line (<10 m) that separated them from their dams (P < 0.0001) and vocalized more than CS calves (P < 0.0001), while in the 2nd period, RS calves had the highest cortisol concentration and vocalization rate (P < 0.05). Similarly, during the 1st period, a greater percentage of RS and TS cows were observed close to the fence line than CS cows (P < 0.0001), with TS cows vocalizing the most (P = 0.001). In the 2nd period, RS cows had greater cortisol concentration than TS (P = 0.037) and CS cows (P = 0.003). More TS and CS cows than RS were observed close to the fence line (P = 0.03 and P = 0.05). On Day 150, TS calves and cows vocalized more than RS and CS animals (P < 0.0001). Before calf–cow separation, 27 out of 45 cows were cycling (CS = 10; RS = 6; TS = 11). After separation, 12 of the remaining 18 cows resumed ovarian activity (CS = 3; RS = 5; TS = 4), and all cows were cycling after estrous synchronization treatment. The pregnancy rate was similar between CS, RS, and TS (60, 53, and 60% respectively). In conclusion, temporary separation increased calf distress response to definitive weaning even four months later, while restricted suckling seemed to reduce it.

The functional development of the rumen is influenced by weaning and associated with ruminal microbiota in lambs

Rumen development is critical for the development of early lambs. This work aims to evaluate the effects of abrupt weaning at day 21 on rumen fermentation, histomorphological traits and the ruminal microbiota compared with continuous suckling. Twelve pairs of artificially reared full-sib neonatal male Hu lambs were allocated to two groups, one of which was weaned at day 21 (EW group) and the other which was not weaned (CON group). At day 26 and day 49, six lambs from each group were randomly selected and sacrificed to collect ruminal contents and rumen tissue samples. Results showed that weaning influenced the fermentation parameters in the rumen, and altered the microbial community composition on day 49 (p < 0.05). Several genera were associated with rumen fermentation parameters (p < 0.05). Volatile fatty acid (VFA) concentration is the key parameter impacting microbiota composition. Weaning influenced the expression of genes associated with VFA metabolism and regulation of cell proliferation (p < 0.05). In conclusion, weaning significantly influenced the morphological and functional development of the rumen, and bacterial community composition. The microbial community composition was strongly associated with rumen weight and fermentation profiles, but not with morphological development.

Reproductive response of Pelibuey sheep to the application of recombinant bovine somatotropin and a metabolic restorative preparation

Abstract: The objective of this work was to evaluate the effect of recombinant bovine somatotropin (rBST) and of the metabolic restorative preparation Metabolase (MR) on the reestablishment of the post-partum ovarian activity of Pelibuey sheep. Ninety-four ewes, with their respective lambs, were randomly assigned to one of the following treatments: T1, continuous suckling (CS); T2, CS + MR; T3, CS + rBST; and T4, CS + MR + rBST. Ovulating percentages, weight changes in ewes and lambs, incidence of estrus, onset and return to estrus, calving, fecundity, and prolificacy were evaluated. The highest ovulation percentages were recorded for CS in T1 and T2, and the lowest ones for rBST in T3 and T4. The treatments had a significant effect on lamb weight. Ewes in T3 had the lowest incidence of estrus (52.9%), besides a greater onset (26.8±1.9 hours) and return to estrus (66.6%). Calving (86.2%) and fecundity (1.8±0.2) were significantly higher in T2. The application of rBST in ewes increases lamb body weight, due to increased milk production, but affects negatively post-partum reproductive activity due to the loss of ewe body weight.

External stimuli help restore post-partum ovarian activity in Pelibuey sheep

Post-partum anestrus is a problem on farms, and its duration depends on the frequency and intensity of suckling which affects reproduction and production efficiency to become a determining economic factor. The aim of this study was to determine the post-partum reproductive response in ewe to a male effect with an ovulation induction protocol of five days using progesterone and the application of a metabolic restorative (MR; Metabolase ®). One hundred and twenty females were randomly assigned to one of four treatments: T1: Continuous suckling (CS; n = 29), T2: CS + MR (n = 29), T3: CS + Male Effect (ME; n = 32), and T4: CS + MR + ME. The percentage of females in ovulation, weight changes among females and lambs, the onset of estrus, calving, fecundity, and prolificacy were also determined. The ovulation percentage was higher in CS + ME and CS + MR + ME (75.0 and 73.3%) than in the other treatments. Weight changes in females and lambs were different among periods. The onset of estrus was similar for CS and CS + MR (25.9 ± 1.9 and 25.7 ± 0.7 h, respectively). The calving percentage was higher for CS + MR (86.2%) than other treatments. Male presence positively affected the postpartum cyclic ovarian re-establishment and the metabolic restorative could even improve the fertility of hair ewes in continuous suckling with similar hormone protocol Keywords : Male effect, metabolic stimulation, post-partum anestrus

Resumption of ovarian function, the metabolic profile and body condition in Brahman cows (Bos indicus) is not affected by the combination of calf separation and progestogen treatment

To evaluate the effect of different calf separation procedures after a progestogen treatment on the resumption of ovarian function, body condition and metabolic profile, 59 multiparous Brahman cows grazing on a mixed grass pasture were studied. No supplementation was given at any time. Body condition score (BCS), fat thickness (FAT) and blood metabolites were measured fortnightly from the beginning of the last trimester of gestation until 96days postpartum. At 30days postpartum all animals received a progesterone (P4)-releasing device (CIDR) which was withdrawn 9days later when prostaglandin F2α was applied. At this time, treatments TW (n=28), where calves were separated from their dams for 48h; RS (n=21), calves were allowed to suckle once a day for 1h; and continuous suckling (CS; n=10). Ovarian function was assessed by blood concentrations of progesterone on days −14, −9, 10, 13, 30 and 33 after CIDR removal. At the end of the experimental period, an average of 20% of the cows had not initiated estrous cycles. There were no changes of FAT or BCS during the last trimester of pregnancy in all cows (P>0.05). During the postpartum period cows of all groups lost (P<0.05) BCS and FAT with a nadir at 60–80days postpartum, regardless of treatment. At 10days after CIDR withdrawal the percentage of cows having ovulations was 75, 61 and 80 (P>0.05) for TW, RS and CS groups. Blood metabolites follow a similar pattern in the three groups. With the conditions of the present study, the method of calf separation after a progestogen treatment, does not affect the resumption of ovarian function or metabolic profile.

Effect of system of lamb rearing and season on early post-partum fertility of ewes and growth performance of lambs in Katahdin sheep.

The effect of season (S), lamb rearing system (RT) and grain supplementation (GS) on post-partum fertility in Katahdin ewes and growth in Katahdin lambs was evaluated. Katahdin ewes were bred to lamb in fall (n=36) or spring (n=56) and at approximately 2.5months post-partum were randomly assigned to be permanently separated or to continue to suckle their lambs for an additional 3months. All ewes were joined with rams following treatment to synchronize oestrus. Weaned (W, n=84) and continuously suckled lambs (CSK, n=88) were fed forage only (n=84; hay and pasture for fall- and spring-born lambs respectively) or were supplemented (n=88; 18% crude protein ration adlibitum) and all weighed biweekly. Ewes rebred in the fall had a shorter ram introduction to lambing interval (p<0.05), higher prolificacy (p=0.001) and higher lambing rates (p=0.02); however, the proportion of ewes lambing was not affected by season. The first service lambing rate was lower in ewes continuously suckling lambs in the spring, but not in the fall breeding season (S×RT, p=0.03). Lambs that continuously suckled their dams and were supplemented grew quicker and gained more (p<0.001) than their weaned and unsupplemented counterparts. The effect of CSK on growth rate of lambs was greater in the spring (RT×S; p=0.05), and the effect of supplementation on growth rate of lambs was greater in the fall (GS×S; p<0.0001). In conclusion, Katahdin lambs achieved higher weight gains from continuous suckling and grain supplementation. Moreover, Katahdin ewes are capable of early rebreeding post-partum while suckling their lambs, which makes them suited for use in accelerated lambing programmes.

Do Developmental Constraints and High Integration Limit the Evolution of the Marsupial Oral Apparatus?

Developmental constraints can have significant influence on the magnitude and direction of evolutionary change, and many studies have demonstrated that these effects are manifested on macroevolutionary scales. Phenotypic integration, or the strong interactions among traits, has been similarly invoked as a major influence on morphological variation, and many studies have demonstrated that trait integration changes through ontogeny, in many cases decreasing with age. Here, we unify these perspectives in a case study of the ontogeny of the mammalian cranium, focusing on a comparison between marsupials and placentals. Marsupials are born at an extremely altricial state, requiring, in most cases, the use of the forelimbs to climb to the pouch, and, in all cases, an extended period of continuous suckling, during which most of their development occurs. Previous work has shown that marsupials are less disparate in adult cranial form than are placentals, particularly in the oral apparatus, and in forelimb ontogeny and adult morphology, presumably due to functional selection pressures on these two systems during early postnatal development. Using phenotypic trajectory analysis to quantify prenatal and early postnatal cranial ontogeny in 10 species of therian mammals, we demonstrate that this pattern of limited variation is also apparent in the development of the oral apparatus of marsupials, relative to placentals, but not in the skull more generally. Combined with the observation that marsupials show extremely high integration of the oral apparatus in early postnatal ontogeny, while other cranial regions show similar levels of integration to that observed in placentals, we suggest that high integration may compound the effects of the functional constraints for continuous suckling to ultimately limit the ontogenetic and adult disparity of the marsupial oral apparatus throughout their evolutionary history.

The effect of permanent or temporary contact with the lamb and contact with males on the lambing to first ovulation interval in Saint Croix sheep

The effect of suckling and presence of the lamb, or ram, on the lambing to first ovulation interval in Saint Croix sheep was determined. Ten days after lambing 50 ewes and their lambs were assigned to three different suckling treatments: continuous suckling (CS), restricted suckling (RS), restricted lamb presence (RP). Ewes from each treatment were allocated to groups that had contact with a ram (TR) or remained isolated from rams (IR). Therefore, overall, there were six groups with 2 factors: CS-IR (n=7) CS-TR (n=7); RS-IR (n=11); RS-TR (n=11); RP-IR (n=7), and RP-TR (n=7). The presence of the ram (P=0.01) and restricted suckling (P=0.05) reduced the interval from lambing to first ovulation, while no interaction was found (P>0.05) between these two factors. An effect of treatment and its interaction influenced significantly the number of vocalizations and growth rate in lambs. At the day of weaning RP vocalized more than RS (P<0.01), which in turn vocalized more than CS (P<0.01), followed by a general decline to pre-weaning levels 48h later. Lambs in RP had greater growth rate during first 3 d after weaning compared with RS (P<0.05), which displayed greater growth rate that CS (P<0.05). In addition, an effect of treatment (P=0.05) was found in cortisol concentration. Our results indicate that Saint Croix ewes respond to the ram effect in early postpartum, shortening the resumption of postpartum ovarian activity. When this technique is combined with restricted suckling, additional benefits are achieved for lambs with reduced weaning stress.

Restablecimiento de la actividad reproductiva posparto en ovejas de pelo

The purpose of this study was to determine the effect of suckling, postpartum (PP) synchro-nization protocol and the ram effect on repro-ductive performance of hairy sheep. Isolated from the rams, 96 ewes were randomly assigned to one of two groups at lambing (n=48): continuous suckling for 18 h (Ac) and controlled suckling for 30 minutes twice a day (Lc). On day 35 PP, both groups were synchronized with CIDR (Controlled Internal Drug Release) for 10 days, 48 hours before CIDR removal, 7,5 mg of dinoprost was administered and the effect of the ram (Ca) 48 hours before and at the time of CIDR removal were tested. We determined progesterone (P4) por radioimmunoassay at 30, 35, 50, 55 y 64 days PP. The ewes were inseminated intrauterine by abdominal laparoscopy 12 to 15 hours after estrus onset. The response variables were: percentage of ovulation before 35 days PP, time of estrus onset, pregnancy rate, prolificacy, fecundity and live weight of the ewes and their lambs. The information obtained was analyzed using logistic regression and Poisson, chi-square test, survival curves and repeated measures analysis. The percentage of ewes that ovulated before 35 days PP was higher (p 0.05) between treatments. The weight of lambs was higher (p<0.05) in Ac after 41 days PP and there was no mortality during lactation. After CIDR removal all ewes showed estrus, being those of Lc (p<0.05) the first to manifest estrous behavior (50 hours). Pregnancy rate, prolificacy and fecundity were not different between treatments and averaged 82.3, 1.84 and 1.51 %, respectively. The results indicate that controlling lactation increases and concentrates the number of ewes that ovulated before 35 days PP. All ewes responded to the synchronization postpartum and the ram effect showing estrous behavior and only one ewe presented corpora lutea of shortened lifespan.

21 DIFFERENT SUCKLING REGIMENS AND RETURN TO POSTPARTUM CYCLIC OVARIAN ACTIVITY IN SANTA INÊS EWES

The aim of this study was to evaluate the effect of different suckling regimens on body condition and interval from lambing to onset of the cyclic ovarian activity in Santa Inês ewes. Thirty-two ewes were allocated to blocks according to parity, number of lambs, and body weight and submitted to 3 treatments: continuous suckling (n = 11 ewes, 13 lambs), controlled suckling (n = 10 ewes, 14 lambs) with 2 suckling periods per day for 1 h from Day 10 postpartum (pp), or early weaning (n = 11 ewes, 14 lambs) with total separation of the lambs from Day 10 pp. The animals were evaluated in the interval from Day 12 pp to first estrus or to Day 60 pp. Dry matter intake was evaluated daily. The body weight of ewes and lambs and body condition score (scale 1 = thin and 5 = fat) of ewes were evaluated at lambing and at every 6 days after. Lambs were weighed at weaning. Estrus was monitored twice daily with a teaser ram. Blood samples for progesterone measurement were collected and ovarian ultrasonography was done at intervals of 3 days from Day 12 pp to first estrus or to Day 60 pp. Dry matter intake was analyzed over time, considering 9 periods, with PROC MIXED of SAS (2008; SAS Institute Inc., Cary, NC, USA). Body weight, body condition score, interval from lambing to first ovulation, and weaning weight were analyzed using the GLM procedure, ANOVA, and an F-test. The intervals from lambing to first estrus and to follicles with a diameter ≥5 mm were analyzed considering a Poisson distribution and the percentage of estrus manifestation was analyzed considering a Bernoulli distribution, by generalized linear models, using PROC GENMOD. The dry matter intake did not differ (P &gt; 0.05) among treatments (2.3 ± 0.1, 2.2 ± 0.0, and 1.6 ± 0.0 kg day–1), but it differed over time (P &lt; 0.05). The body weight gain (3.3 ± 1.0, 3.0 ± 0.9, and 2.1 ± 1.4 kg), body condition score gain (0.2 ± 0.1, 0.2 ± 0.1, and 0.2 ± 0.1), percentage of estrus manifestation (63.6, 50.0, and 54.5%), interval from lambing to first estrus (45.0 ± 3.9, 44.0 ± 7.2, and 32.3 ± 5.4 days), follicle with a diameter ≥5 mm (31.0 ± 3.3, 33.9 ± 3.0, and 34.9 ± 4.5 days), and ovulation (38.0 ± 3.6, 35.6 ± 3.9, and 26.5 ± 3.2 days) did not differ among treatments (P &gt; 0.05). The dry matter intake was correlated with body weight in ewes that were submitted to continuous suckling (r = 0.7; P &lt; 0.01) and controlled suckling (r = 0.6; P &lt; 0.01), but not in those submitted to early weaning (r = 0.2; P &gt; 0.05). The body condition score was correlated with body weight in ewes submitted to continuous suckling (r = 0.8; P &lt; 0.01), controlled suckling (r = 0.4; P &lt; 0.01), and early weaning (r = 0.5; P &lt; 0.01), and with dry matter intake in those submitted to continuous suckling (r = 0.4; P &lt; 0.01). Weaning weight was lower (P &lt; 0.05) in lambs subjected to early weaning (19.0 ± 1.0, 18.3 ± 1.0, and 15.2 ± 0.6 kg), but their health was not compromised. Continuous suckling did not delay the return to postpartum cyclic ovarian activity and did not influence the postpartum body condition of Santa Inês ewes and should be used by producers. The financial support of Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) is acknowledged.

Cocaine- and amphetamine-regulated transcript (CART) expression is differentially regulated in the hypothalamic paraventricular nucleus of lactating rats exposed to suckling or cold stimulation

Neural stimuli, such as suckling or cold exposure, increase TRH mRNA in the paraventricular nucleus (PVN) of the rat hypothalamus, yet only suckling induces prolactin secretion. As TRH co-localizes with cocaine- and amphetamine-regulated transcript (CART) in hypophysiotropic neurons of the PVN, and CART inhibits TRH-induced prolactin release but not TRH-induced TSH release in adenohypophyseal cell cultures, we raised the possibility that differential regulation of CART gene expression in the PVN may explain the differences in prolactin secretion following each of the two stimuli. Primiparous female rats were mated and handled daily during the pre- and postpartum periods. After delivery, the litter was adjusted to 8 pups and at mid-lactation, dams were separated from their pups for 8 h and exposed to either 1 h of cold or 30 min of suckling. Long-term effects of suckling were studied by separating pups from their mothers for 24 h, followed by a 12 h period of continuous suckling. Serum TSH levels increased in response to cold exposure, while prolactin levels were increased by suckling and diminished by cold exposure. CART mRNA levels increased in rostral and mid parts of the medial parvocellular PVN following cold exposure but not after suckling stimulation. These data demonstrate a differential regulation of CART gene expression in hypophysiotropic neurons in response to stimuli that increase TRH mRNA levels, and suggest that CART activation in the PVN may contribute to the decrease in PRL release when the thyroid axis is activated by cold exposure.

A new tool for measuring the suckling stimulus during breastfeeding in humans: the orokinetogram and the Fourier series.

The Fourier series was used to analyse the oral movements recorded by the orokinetogram during breastfeeding in human babies. This is a new method that allows recording of oral movements without introducing any extrinsic element between the nipple and the mouth of the baby. The advantage of displaying suckling activity after fast Fourier transform (FFT) is that this algorithm allows storage, quantification and frequency analysis of the oral movements throughout a suckling bout, which enables the total oral activity to be measured. Two types of oral movements are found: slow high amplitude (SHA) and fast low amplitude (FLA). FLA movements may be derived from peristaltic movements of the tongue that result in tickling stimuli to the mechanoreceptors of the nipple and milk expression. The frequency bandwidth of oral movements is wider (0-8 Hz) than has been described previously (0-3 Hz) and this is due to the presence of the FLA oral movements. An indirect measurement of the energy of oral movements during suckling is obtained by the pattern of energy distribution used in each individual frequency band by oral movements. This pattern changes in relation to the periods of continuous and intermittent suckling activity. SHA and FLA oral movements are more intense during continuous suckling. Statistical analysis showed a correlation between the energy of SHA and FLA waves throughout the suckling bout, and also that the highest level of energy during suckling activity is displayed during the first 2 min. The novel tools described in this paper allow investigation of the role of suckling stimulus in reflex hormone release and other mother-infant interactions.

Oxytocin and milk removal are required for post-partum mammary-gland development.

The oxytocin (OT)-neurophysin preprohormone is synthesized in the paraventricular and supraoptic nuclei of the hypothalamus. OT is cleaved from its precursor, transported from the magnocellular neurons to the posterior pituitary and secreted during labour and upon the suckling stimulus of pups. OT induces the contraction of myoepithelial cells surrounding the mammary alveoli, which leads to the ejection of milk. Mice deficient in OT are unable to nurse their young. Administration of OT enabled OT-deficient dams to nurse. We now show that OT and milk removal are also required for post-partum alveolar proliferation and mammary-gland function. Alveolar density and mammary epithelial-cell differentiation at parturition was similar in wild-type and OT-deficient dams. However, within 12 h after parturition approx. 2% of the alveolar cells in wild-type dams incorporated DNA and proliferated, but virtually no proliferation was detected in OT-deficient dams. Continuous suckling of pups led to the expansion of lobulo-alveolar units in wild-type but not in OT-deficient dams. Despite suckling and the presence of systemic lactogenic hormones, mammary tissue in OT-deficient dams partially involuted. Our studies demonstrate that post-partum alveolar proliferation requires not only systemic lactogenic hormones, such as prolactin, but also the presence of OT in conjunction with continued milk removal.

Maternal interactions prior to separation potentiate isolation-induced calling in rat pups.

The vocal response rates of 12-13-day-old infant rats to isolation in a bare test box are markedly increased by brief (1-min) periods of contact with an anesthetized dam prior to isolation, without affecting other isolation-induced behaviors. No such potentiation followed brief contact with littermates, novel test conditions, or experimenter handling. Brief contact with the dam was equally effective in the test chamber or home cage and was not further enhanced by repeated contact-separation sequences. Passive contact became ineffective when prolonged to 30 min, and potentiation could not be restored by providing the additional reinforcing events of continuous suckling, periodic oxytocin-induced milk letdown, or bouts of simulated maternal licking. However, when pups engaged in active interaction with an awake dam, potentiation was significantly enhanced following 1-, 10-, and 30-min periods. A working hypothesis is outlined for the adaptive role of potentiation in the development of the rat pup.

Expression of Fos-related antigens, oxytocin, dynorphin and galanin in the paraventricular and supraoptic nuclei of lactating rats.

The magnocellular oxytocin neurons within the paraventricular and supraoptic nuclei (PVN and SON) of the hypothalamus are important relays in the milk ejection reflex in lactating animals, and are activated by suckling. It has been suggested that proto-oncogene transcription factors such as Fos/Jun act as early nuclear transducers of sensory stimuli in neurons. Therefore, we have studied with immunohistochemistry Fos-related antigens (FRAs) as a marker for neuronal activity in the PVN and SON during suckling in lactating rats. In nonlactating rats, only few cells exhibiting FRAs were observed in these nuclei. Also in lactating rats subjected to continuous suckling Fos-like activity was low. In contrast, lactating rats separated from their pups for 4 h and then exposed to suckling for 1 h expressed strong Fos-like immunoreactivity, both in vasopressin and oxytocin neurons. Using in situ hybridization and immunohistochemistry we have also investigated the expression of the mRNAs for oxytocin, dynorphin, galanin and galanin message-associated peptide and of oxytocin and dynorphin in the PVN of lactating and nonlactating rats. In lactating rats, an increase in oxytocin and dynorphin and their mRNAs was observed, whereas mRNAs for galanin and galanin message-associated peptide were downregulated. With the help of immunohistochemistry and double-staining methods, a substantial coexistence between oxytocin- and dynorphin-like immunoreactivities was shown in magnocellular neurons. These results indicate that FRAs are activated in the PVN in the beginning of a suckling period, while this response cannot be seen after continuous stimulation. Furthermore, in the PVN of lactating rats, an upregulation of oxytocin and dynorphin occurs while galanin expression decreases. Finally, the coexistence between oxytocin and dynorphin is more pronounced in lactating rats and nonlactating female rats than has previously been described in male rats.