Subsequent Conception Rate Research Articles

278 Phytogenic feed additive increased sow lactation average daily feed intake, litter weaning weight, and subsequent conception rate when fed in summer environmental conditions

Abstract An experiment was conducted to test the hypothesis that feeding a phytogenic feed additive (Fresta F, Delacon, Austria) to sows during lactation would increase lactation average daily feed intake (ADFI) during natural heat stress from summer environmental conditions. At the time of entry to lactation facilities, 192 sows were randomly allotted by parity and within farrowing batch to one of two treatments. A basal lactation diet based primarily on corn, soybean meal, and dried distiller’s grains with solubles (DDGS) served as the control treatment, whereas the test treatment contained 0.04% phytogenic feed additive at the expense of corn. Before farrowing, sows were limit fed, but once farrowing occurred, sows were provided with ad libitum access to feed. Individual feed disappearance was recorded daily, and sow was considered the experimental unit. Sow body weights (BW) and ultrasound backfat thickness were recorded at the time of entry to and exit from the lactation facilities. Litter weights were recorded at birth and at weaning, and litter inventories were recorded at birth, upon completion of cross-fostering within treatment, on d 5 of lactation, and at weaning. Ultimately, 185 sows completed the study and were included in statistical analyses. Data were analyzed using the lme4 package of R 4.1.2, and the statistical models included the fixed effect of treatment and the random effects of parity and farrowing batch. Data were assumed to be normally distributed, except for pig survival and conception rate, which were analyzed using generalized linear mixed models specifying a binomial distribution. Total and live litter size did not differ at birth, nor did litter birth weight (Table 1). Inclusion of the phytogenic feed additive increased (P < 0.05; ADFI in lactation from 6.21 to 6.74 kg per day. In turn, the phytogenic feed additive tended (P < 0.10) to increase litter wean weight, which was driven by numerically increased piglet survival (87.47% for control and 89.37% for phytogenic, P = 0.126) and a tendency (P < 0.10) for increased average pig weaning weight. Sow BW did not differ at entry to lactation, though sow weight at weaning tended to be greater (P < 0.10) when the phytogenic feed additive was fed. The phytogenic feed additive also increased (P < 0.05) subsequent conception rate from 88.7 to 97.8%. In conclusion, feeding a phytogenic feed additive during summer conditions increased lactation feed intake, which resulted in increased weaning weight and improved subsequent conception rate.

Ad libitum feeding systems for lactating sows: effects on productivity and welfare of sows and piglets

The nutritional requirements of sows change during lactation and thus require adapted and dynamic feeding regimes that consider the sows’ behavioral needs and production traits. The present study evaluated the effect of four different feeding systems on productivity and aspects of the welfare of 61 sows and their piglets during lactation. A non-ad libitum system (CON) was compared with two computer-monitored (COMP, COMP + ) ad libitum feeding systems, that allowed sows to access feed via displacement of an electronic sensor, as well as a third purely mechanical ad libitum feeding system (MECH). Daily feed disappearance, piglet growth, piglet growth per feed disappearance as well as sows’ weight and conception rate were recorded. Health indicators of sows and piglets were scored as well as sow behavior analyzed for a total of 96 hours/sow from video recordings taken on days 2–4 and 23 postfarrowing (n = 35 sows). Sows from all three ad libitum systems (COMP, COMP+, MECH) showed a lower feed disappearance than CON (P < 0.01). Additionally, average daily piglet growth tended to be higher (P = 0.05) and piglet growth per sow feed disappearance was significantly higher in all three ad libitum systems than in CON (P < 0.01). Piglet mortality, sow weight loss and subsequent conception rates did not differ between treatment groups. Piglets in COMP and COMP + had fewer head lesions (P = 0.01). Sows in all three ad libitum systems spent more time with their head in the trough than in the non-ad libitum system (P < 0.01). Occurrence of sow stereotypies (vacuum chewing, biting fixtures) was rare (typically < 2% of scans) and did not differ between treatments. Our data suggest that sows fed ad libitum eat what they need and can convert feed more efficiently into the piglets’ growth without additional weight loss. Furthermore, the increased time sows spent in ad libitum systems with their head in the trough points toward longer feeding times, which might be beneficial in terms of meeting pigs’ behavioral need to forage. Taken together, our initial studies on sow feeding behavior and feed efficiency will benefit the development of new lactation feeding systems that promise to improve animal welfare and productivity while reducing feed costs.

Metabolomics Analysis Discovers Estrogen Altering Cell Proliferation via the Pentose Phosphate Pathway in Infertility Patient Endometria.

Estrogen therapy is widely used as a supplementary treatment after hysteroscopy for female infertility patients owing to its protective function that improves endometrial regeneration and menstruation, inhibits recurrent adhesions, and improves subsequent conception rate. The endometrial protective function of such estrogen administration pre-surgery is still controversial. In the current study, 12 infertility patients were enrolled, who were treated with estrogen before hysteroscopy surgery. Using cutting-edge metabolomic analysis, we observed alterations in the pentose phosphate pathway (PPP) intermediates of the patient’s endometrial tissues. Furthermore, using Ishikawa endometrial cells, we validated our clinical discovery and identified estrogen–ESR–G6PD–PPP axial function, which promotes estrogen-induced cell proliferation.

Dynamics of Selected Trace Minerals during Estrus Induction in Anestrus Sahiwal Cattle

The present study evaluated the effect of circulatory trace mineral profiles on fertility response during estrus induction by progesterone based therapy in acyclic Sahiwal cattle. Sahiwal cows and post-pubertal heifers (n=25 each) with true anestrus condition (acyclicity confirmed ultrasonographically) were subjected to CIDR-based protocol (intravaginal CIDR application for 7 days, 500 IU eCG at CIDR removal, followed by estrus observation and AI). In heifers, additionally an injection of 5.0 mg estradiol valerate at CIDR insertion was given. Blood samples on days 0 (before CIDR application), 3, 5, 7 and 9 were collected. Almost similar estrus induction (68% vs. 64%) and subsequent conception rates (41.2% vs. 50%) during the first induced estrus were recorded in cows and heifers, respectively. During the course of treatment, significant (P 0.05) was recorded for iron concentration vis-a-vis estrus induction response. Hence, it is indicated that circulatory copper, zinc and manganese profiles influence the reproductives energy in acyclic animals and their suboptimal profiles may reduce the efficacy of estrus induction protocols in Sahiwal cattle.

Vaginal Bacterial Profile in Buffaloes Following Treatment with Progesterone Insert

The objective of this study was to characterize the vaginal bacterial flora and subsequent conception rates after AI in buffaloes subjected to 3 different estrous induction regimes-the use of CIDR and use of two intravaginal sponges (Polyurethane sponges with micronized progesterone and Polyurethane sponges with micronized progesterone with Carboxy methyl cellulose). The estrus induction was 100% in Group I and II followed by 91.67% in group III. The pregnancy rates were Group I, II and III were 50.00, 66.67 and 54.55% respectively. All the vaginal swabs in all three groups yielded growth of bacteria and the predominance of mixed isolates over single isolates 81.94% vs 18.06% was indicative of dominance of mixed culture over single isolates. E. coli, Staphylococcus, Proteus and Klebsiela spp. were the commonest isolates obtained prior to insertion and after removal of implants in postpartum anestrus buffaloes. The gram positive bacteria were Staphylococcus, Streptococcus and Bacillus spp. while, gram negative bacteria were E. coli, Proteus and Klebsiella spp. These organisms could be considered as a part of the normal bacterial flora of the buffalo.

Mastitis outcomes on pre-ovulatory follicle diameter, estradiol concentrations, subsequent luteal profiles and conception rate in Buffaloes

The objectives of this study was to investigate the outcome of mastitis, in its clinical or subclinical forms, on the mean diameter of pre-ovulatory follicle (POF), plasma estradiol concentration on the day of estrus, subsequent luteal profile and subsequent conception rate in buffaloes. Sixty dairy buffalo (Bubalus bubalus) conducted in this study were divided into three groups {healthy (H), n=20; subclinical mastitis (SCM), n=18; and clinical mastitis (CM), n=22}. Ultrasonography of ovaries revealed that mean diameter of POF was larger (P<0.05) in H buffalo (14.35mm) compared to SCM (12.40mm) and CM (10.25mm). Also, plasma estradiol concentration on the day of estrus was higher (P<0.05) in H buffalo compared to SCM and CM counterparts; 34.95 vs. 32.87 and 27.50pg/ml, respectively. Besides, positive correlation was observed between the POF diameter with plasma estradiol concentration in H, SCM and CM buffaloes (r=0.64, 0.74, 0.72 respectively, P<0.05). Moreover, positive correlations (P<0.01) were found on days 9, 12, 16, and 21 post-ovulation between POF diameter and luteal profile. Thus, the conception rate in H buffalo was higher (P<0.05) compared with SCM and CM counterparts; 55% vs. 38.89 and 18.18%, respectively. In conclusion, mastitis in its clinical or subclinical forms disrupts the functioning of the pre-ovulatory follicle on the day of estrus, associated with low follicular estradiol production, resulting in suppression to subsequent luteal profile leading to substantial decrease in pregnancy consequence of buffaloes.

Impact of Buserelin Acetate or hCG Administration on the Day of First Artificial Insemination on Subsequent Luteal Profile and Conception Rate in Murrah Buffalo (Bubalus bubalis).

This study was designed to investigate the impact of buserelin acetate (BA) or human chorionic gonadotropin (hCG) administration on the day of first artificial insemination (AI) on subsequent luteal profile (diameter of corpus luteum (CL) and plasma progesterone) and conception rate in Murrah buffalo. The present experiment was carried out at two locations in 117 buffalo that were oestrus-synchronized using cloprostenol (500μg) administered (i.m.) 11days apart followed by AI during standing oestrus. Based on treatment (i.m.) at the time of AI, buffalo were randomly categorized (n=39 in each group) into control (isotonic saline solution, 5ml), dAI-BA (buserelin acetate, 20μg) and dAI-hCG (hCG, 3000 IU) group. Out of these, 14 buffalo of each group were subjected to ovarian ultrasonography on the day of oestrus to monitor the preovulatory follicle and on days 5, 12, 16 and 21 post-ovulation to monitor CL diameter. On the day of each sonography, jugular vein blood samples were collected for the estimation of progesterone concentrations. All the buffalo (n=117) were confirmed for pregnancy on day 40 post-ovulation. The conception rate was better (p<0.05) in dAI-BA (51.3%) and dAI-hCG (66.7%) groups as compared to their control counterparts (30.8%). Furthermore, the buffalo of dAI-hCG group had improved (p<0.05) luteal profile, whereas the buffalo of dAI-BA group failed (p>0.05) to exhibit stimulatory impact of treatment on luteal profile when compared to control group. In brief, buserelin acetate or hCG treatment on the day of first AI leads to an increase in conception rate; however, an appreciable impact on post-ovulation luteal profile was observed only in hCG-treated Murrah buffalo.

Impact of buserelin acetate or hCG administration on day 5 post-ovulation on subsequent luteal profile and conception rate in Murrah buffalo (Bubalus bubalis)

The present study aimed to establish the impact of buserelin acetate or hCG administration on day 5 post-ovulation on subsequent luteal profile and conception rate in buffalo. The buffalo (n=45) were subjected to an estrous synchronization protocol (synthetic analog of PGF2α administered, through intramuscular route, 11 days apart), followed by artificial insemination (AI) during mid to late estrus. On day 5 post-ovulation, buffalo were administered (i.m.) normal saline (Control, n=14), buserelin acetate (20μg, d5-BA, n=14) or human chorionic gonadotropin (3000IU, d5-hCG, n=17). Ovarian ultrasonography was conducted on the day of induced estrus and on days 0, 5, 12, 16 and 21 post-ovulation to assess preovulatory follicle or corpus luteum (CL) diameter. Also, on these days, jugular vein blood sampling was conducted for the estimation of plasma progesterone. First service conception rate was greater (χ2=5.18, P>0.05) in d5-BA and d5-hCG groups (71.4% and 47.1%, respectively) as compared to control (28.6%). Both treatment groups had a greater (P<0.05) CL diameter and plasma progesterone during the post-treatment period in comparison to that control treatment group. Treatment-induced accessory CL formation was observed in 92.9% and 76.5% buffalo of d5-BA and d5-hCG groups, respectively. In conclusion, buserelin acetate and hCG administration on day 5 post-ovulation leads to accessory CL formation that may have a role in enhancing conception rate.

Estimation of the optimal standardized ileal digestible lysine requirement for primiparous lactating sows fed diets supplemented with crystalline amino acids.

This experiment was conducted to determine the optimal standardized ileal digestible lysine (SID Lys) level in diets fed to primiparous sows during lactation. A total of 150 (Landrace × Large White) crossbred gilts (weighing 211.1 ± 3.5 kg with a litter size of 11.1 ± 0.2) were fed lactation diets (3325 kcal metabolizable energy (ME)/kg) containing SID Lys levels of 0.76, 0.84, 0.94, 1.04 or 1.14%, through 28 days lactation. Gilts were allocated to treatments based on their body weight and backfat thickness 48 h after farrowing. Gilt body weight loss was significantly (P < 0.05) decreased by increasing dietary SID Lys levels. Fitted broken-line (P < 0.05) and quadratic plot (P < 0.05) analysis of body weight loss indicated that the optimal SID Lys for primiparous sows was 0.85 and 1.01%, respectively. Average daily feed intake (ADFI), weaning-to-estrus interval and subsequent conception rate were not affected by dietary SID Lys levels. Increasing dietary lysine had no effect on litter performances. Protein content in milk was increased by dietary SID Lys (P < 0.05). Dietary SID Lys tended to increase concentrations of serum insulin-like growth factor I (P = 0.066). These results of this experiment indicate that the optimal dietary SID Lys for lactating gilts was at least 0.85%, which approaches the recommendation of 0.84% that is estimated by the National Research Council (2012).

Size of dominant follicle, plasma progesterone and estradiol levels on the day of ovulation and subsequent conception rate in buffalo (Bubalus bubalis) following modified ovsynch + CIDR protocol

The study was designed to compare the size of dominant follicle (DF) achieved, plasma progesterone decline and plasma estradiol level on the day of estrus and subsequent conception in buffaloes subjected to modified ovsynch-based regimen in buffaloes. In estradiol-based protocol (n = 15) on day 0 (beginning of experiment), buffaloes were administered controlled internal drug release (CIDR) device (1.38 g P4) and concurrently received 1.5 mg estradiol-17β in 1.5 ml canola oil (i.m.). On day 9, CIDR was removed and a PGF2α analogue (500 µg, i.m.) administered. On day 11, buffaloes were administered gonadotropin releasing hormone (GnRH) analogue (20 µg, i.m.) and inseminated on day 11 and day 12. Ovsynch-based group (control, n = 15) received GnRH on day 0 in place of estradiol-17β, CIDR insert for 7 instead of 9 days and the remaining protocol and insemination procedures were same as treatment group. The diameter of DF, plasma progesterone and estradiol levels were not different between the groups. The first service conception rate (FSCR) was higher (p < 0.05) in estradiol-based group than in control (53.33 vs. 33.33%, respectively). In conclusion, replacement of first GnRH with estradiol-17β in ovsynch plus CIDR protocol and increasing CIDR exposure by two days leads to higher FSCR.

Impact of buserelin acetate or hCG administration on day 12 post-ovulation on subsequent luteal profile and conception rate in buffalo (Bubalus bubalis)

The present study investigated the impact of gonadotropic hormone administration on day 12 post-ovulation on subsequent luteal profile and conception rate in buffaloes. All the buffaloes (n=48) were estrus synchronized by a synthetic analogue of prostaglandin F2α (PGF2α), administered 11 days apart, followed by insemination during mid to late estrus. To examine the effect of mid-luteal phase hormonal treatment, buffaloes were randomly divided into control (normal saline, n=14), d12-BA (buserelin acetate, 20μg, n=17) and d12-hCG (hCG, 3000IU, n=17) groups. Ovaries were scanned on the day of induced estrus to measure the preovulatory follicle (POF) diameter and on days 5, 12, 16 and 21 post-ovulation to examine the alterations in corpus luteum (CL) diameter. On the day of each sonography, blood samples were collected for the estimation of plasma progesterone. In treatment groups, luteal profile (CL diameter and plasma progesterone) on day 16–21 post-ovulation was better (P<0.05) as well as first service conception rate was higher (52.9% in each treatment group vs. 28.6%, P>0.05) compared to controls. All the pregnant buffaloes exhibited higher (P<0.05) plasma progesterone on various post-ovulation days than their respective non-pregnant counterparts. Treatment-induced accessory corpus luteum (ACL) formation was observed in 58.8 per cent and 70.6 per cent buffaloes of d12-BA and d12-hCG group, respectively, that also had higher (P<0.05) plasma progesterone compared to controls. Compared to the spontaneous CL, the diameter of ACL was less (P<0.05) in the treatment groups. In conclusion, buserelin acetate and hCG administration on day 12 post-ovulation leads to accessory CL formation, improves luteal profile and consequently increases conception rate in buffaloes.

Impact of norgestomet supplementation during early luteal phase on subsequent luteal profiles and conception rate in buffalo: a preliminary study

The current study was aimed to establish the impact of progesterone supplementation (norgestomet progestagen) between days 4 to 10 post-ovulation on subsequent luteal profile and conception rate in buffaloes. The 28 Murrah buffaloes of second to fourth parity, having normal reproductive organs, were estrus synchronized by double PGF(2α) protocol at 11 days apart. The buffaloes were inseminated during mid- to late estrus and thereafter repeated at 24 h interval. The buffaloes were randomly assigned into two groups: (1) control (no treatment, n = 14) and (2) treatment group (CRESTAR ear implant, n = 14). The CRESTAR ear implant (3 mg, norgestomet progestagen) was inserted subcutaneous between days 4 to 10 post-ovulation. The ovaries were scanned at estrus and thereafter on days 4, 10, 16, 21, and 40 post-ovulation to examine the preovulatory follicle (POF) and corpus luteum (CL) diameter. Each ultasonography was followed by blood sample collection for analysis of plasma progesterone concentrations following ovulation. The conception rate was similar (p > 0.05) between treated and control buffaloes. The pregnant buffalo of the control group had larger (p < 0.05) POF diameter than nonpregnant counterparts. The CL diameter was similar (p > 0.05) in both treated and untreated control as well as in their pregnant and nonpregnant buffaloes of the respective groups. The plasma progesterone concentrations were higher (p < 0.05) in the treatment group on the day 10 post-ovulation as compared to the control buffaloes. It is concluded that norgestomet supplementation had no impact on conception rate and CL diameter but enhances the plasma progesterone concentrations following treatment in buffaloes.

Postpartum Variations of Plasma IGF and IGFBPs, Oocyte Production and Quality in Dairy Cows: Relationships With Parity and Subsequent Fertility

The aim of this study was to determine whether postpartum variations of plasma IGF-1 and IGFBP concentrations, oocyte production and quality were related to parity and subsequent conception rate in Holstein dairy cows. Holstein dairy cows [10 primiparous (PP) and 22 multiparous (MP)] were allotted in six batches and sampled once weekly between calving and oestrous synchronization treatment started at 71.2 ± 2.0 days postpartum. During the 3 weeks before treatment, ovum pick-up (OPU) was performed twice weekly. Oocytes were scored on a 4-point scale, and oocytes from OPU1, 3 and 5 were fertilized in vitro. Seventeen cows became pregnant after first and second AI and were considered as fertile (F), while the others were considered to be subfertile (SF). Logistic regression was carried out to investigate the relationships between repeated measurements and fertility including parity and batch effects in the models. Likelihood of fertility significantly increased when plasma urea and IGFBP-3 concentrations decreased and was higher in PP compared with MP cows. There was a trend for fertility to increase when plasma IGF-1 concentrations increased (p = 0.07). In vitro cleavage and development rates were similar between SF and F cows (46.4% and 28.3% in SF vs 55.0% and 22.1% in F). Parity had an effect on plasma IGF-1 concentrations (PP: 61.65 ± 2.67 vs MP: 41.63 ± 5.81 ng/ml, p < 0.001), mean number of follicles aspirated per session (PP: 5.7 ± 1.3 vs MP: 9.5 ± 0.8, p < 0.05) and fertility (PP: 8/10 = 80% vs MP: 9/22 = 41%, p < 0.05) but not on the number of oocytes recovered per session nor their quality. In conclusion, postpartum plasma urea and IGFBP-3 concentrations, but not oocyte production and quality before breeding, were related to subsequent conception rate in our experimental design. Parity had a significant effect on energy status, follicular growth and fertility and needs to be considered when investigating relationships between nutrition and reproduction.

RELATIONSHIPS BETWEEN BODY AND SCROTAL MEASUREMENTS, AND SEMEN CHARACTERISTICS IN YANKASA RAM

The study was conducted to determine the relationsh ips between body measurements, scrotal and seminal characteristics using 62 Yankasa rams at th e Teaching and Research Farm of the Department of Animal Science, Ahmadu Bello University, Zaria, Nigeria. Body measurements related positively with testicular measurements (0.40-0.83). Body (0.27-0.4 8) and testicular (0.25-0.48) measurements were positively related to semen characteristics. Howeve r, the relationship between semen pH and sperm concentration was negative (-0.29 to -0.38), with t esticular dimension (-0.30 to -0.38) and with body measurements (-0.29 to -0.38). The study revealed t hat efficient fertility of Yankasa rams and subsequent conception rate in ewes would depend on the interactions of these variables.

Impact of pre-ovulatory follicle diameter on plasma estradiol, subsequent luteal profiles and conception rate in buffalo (Bubalus bubalis)

The present study was designed to investigate the impact of pre-ovulatory follicle (POF) diameter on the day of estrus on plasma estradiol concentration, subsequent luteal profile (corpus luteum, CL, diameter and plasma progesterone concentration) and conception rate in buffaloes. Twenty-eight buffaloes were synchronized with synthetic analogue of prostaglandin F2α (PGF2α) administered 11 days apart. Transrectal ultrasonography and jugular vein blood sampling was carried out on the day of estrus and on days 0 (day of ovulation), 5, 12, 16 and 21 post-ovulation. Out of 28 buffaloes, 11 (39.3%) were diagnosed pregnant on day 40 post-ovulation. Retrospective analysis revealed that the buffaloes getting pregnant had larger (p<0.05) POF diameter. In fact, all the buffaloes (n=5/5) having POF diameter between >14 and 16mm conceived, whereas, conception rate in buffaloes with POF diameter between >12 and ≤14mm (n=6/17) or <12mm (n=0/6) was 35.3% and 0.0%, respectively. A positive correlation (r=0.57, p<0.05) was observed between POF diameter and plasma estradiol concentration at estrus. On day 5 post-ovulation, luteal profile was positively correlated (CL: r=0.34, p<0.05; plasma progesterone concentration: r=0.27, p>0.05) with POF diameter. Further, on the same day, plasma progesterone concentration was positively correlated (r=0.47, p<0.05) with CL diameter, however, this correlation was absent (r=0.05, p>0.05) during the subsequent luteal phase. Nevertheless, the post-ovulation luteal profile of pregnant buffaloes was higher (p<0.05) compared to non-pregnant counterparts. In conclusion, the diameter of POF in buffaloes has positive impact on plasma estradiol concentration at estrus, post-ovulation luteal profile and conception rate. The diameter of CL can be used as an indicator of luteal function at early but not at mid or late luteal phase of estrus cycle in buffaloes.

The effect of strain of Holstein-Friesian cow and feeding system on postpartum ovarian function, animal production and conception rate to first service

Three strains of Holstein-Friesian (HF): high production North American (HP), high durability North American (HD) and New Zealand (NZ) cows were assigned, within strain, to one of three pasture-based feeding systems: (1) the Moorepark (control) system (MP), (2) a high concentrate system (HC), (3) a high stocking rate system (HS). Ovarian function was assessed using milk progesterone samples, collected from 117 cows in each of two successive years, with 81 animals being common to both years. Milk samples were collected thrice weekly, beginning day 5 post-calving and continued to day 26 after first AI. Data from animals subsequent to reproductive hormonal treatment were removed from the analysis. Feed system and strain of HF by feeding system interaction had no significant effect on re-establishment of ovarian activity and subsequent conception rate to first AI. Strain of HF had no significant effect on interval to commencement of luteal activity (CLA). The mean interval to CLA was 32.9 days (S.E. 1.18), ranged from 6 to 100 days, with 42 and 85% of cows ovulating by day 26 and 60, respectively. The HD (62%) and NZ (57%) strains had a higher conception rate to first AI than the HP strain (40%), ( P < 0.05). Retrospective analysis categorised all cows into four quartiles based on interval to CLA (<20 days, 20–26 days, 27–44 days and >44 days). Cows in the first and fourth CLA quartiles had a longer calving to conception interval ( P < 0.05). Cows with abnormal progesterone profiles (38.4%) had an earlier mean calving date, with a similar submission rate and conception rate to first service compared to cows with normal hormonal profiles. There was no significant difference in luteal activity or reproduction performance, apart from calving to conception interval, between cows that conceived or did not conceive to first service. These results indicate that while conception rate to first service differed between strains of HF cow, this was not associated with differences in the onset and pattern of luteal activity post partum.

Body lipid reserves and the reproductive cycle: towards a better understanding

The aim of this paper was to develop a framework describing the relationship between body lipid reserves and the reproductive cycle. This is derived from consideration of the underlying cycle of reproductive priorities and strategies of dealing with environmental constraints. A way to quantify reproductive priority is proposed, based on the rate of maternal energy investment in the offspring. The majority of environmental constraints alter body energy mobilisation, which in turn affects reproductive factors such as the duration of post-calving anoestrus and subsequent conception rate. The accumulation of body lipid reserves in pregnancy is an important strategy for safeguarding reproductive investment. Consequently, body lipid reserves vary through the reproductive cycle in a predictable manner. These issues are discussed and then developed into a conceptual framework. Simple functions describing the negative effects of increasing lipid mobilisation rate and decreasing body fatness on the likelihood of onset of oestrus cycling postpartum are presented. The approach taken appears to be of value, not least because it raises a number of issues that merit further investigation. The resulting framework provides a basis for evaluating the pressures on reproduction and a way to predict the impact of future management and selection strategies.

Type of Cottonseed and Level of Gossypol in Diets of Lactating Dairy Cows: Plasma Gossypol, Health, and Reproductive Performance

Objectives were to determine effects of altering gossypol intake by feeding whole linted Upland (WUP) or a 1:2 blend of WUP and cracked Pima (BUPCP) cottonseed on plasma gossypol (PG) concentrations, reproduction, and health of Holstein cows. Cows, 813, on three dairy farms were assigned to one of two diets starting at 13±11 d in milk for a 170-d experiment. Diets contained 717 and 951mg of free gossypol/kg of dry matter from WUP and BUPCP, respectively. Concentrations of PG, as well as the proportion of total gossypol (TG) as the minus isomer were higher for cows fed BUPCP vs cows fed WUP. Conception rate at the first postpartum artificial insemination did not differ between treatments. However, cows consuming the higher gossypol diet had reduced subsequent conception rates and a lower pregnancy rate. Incidence of abortions increased in the higher gossypol diet, and cows that aborted or remained open had higher PG concentrations. Increasing PG concentrations resulted in reduced conception rates and extended days open. The probability of conception after the first artificial insemination declined at a decreasing rate as the plasma TG increased. Incidence of health disorders were unaffected by gossypol intake and PG concentrations. Similarly, gossypol intake and PG concentrations had no effect on culling or mortality. Six cows died in each diet, and none had postmortem signs compatible with gossypol toxicity. Consumption of a high gossypol diet for 170 d had no effect on health of lactating dairy cows, but it increased PG concentrations and impaired reproductive performance.

Influence of nutrition and lactation on ovulation and conception in red deer

Reproduction incurs a high energetic cost and failure to meet nutritional needs results in reproductive failure. In red deer hinds, the interaction between nutrition, summer lactation and subsequent ovulation/conception is of particular interest for farmed deer production in NZ due to climatic constraints to summer pasture production in many areas. However, few studies have focussed on the potential perturbing effects of poor nutrition on lactational outputs and potential flow-on effects on ovulation/conception. As lacta tion in red deer naturally persists well beyond the autumn mating period, lactational anoestrus (through hormonal feedback mechanisms) is not a normal feature of the species reproduction. However, lactation is of high nutritional cost to the hind and can potentially exert considerable influence on the incidence and timing of conception via changes in hind liveweight, lipid depots and general body condition. Supporting evidence for this hypothesis is derived from studies of wild red deer within habitats marginal to species survival (e.g. Isle of Rhum, Scotland), where climatic variables greatly influence annual reproductive success of hinds. Under such conditions, even the differences in maternal investment (via lactation) required to raise male and female calves have been demonstrated to influence the subsequent success and timing of conceptions. Studies of farmed red deer in Scotland also demonstrated that hinds on different levels of pasture nutrition during lactation exhibited significant differences in conception date, with earlier conceptions favouring hinds on higher levels of nutrition. There is a growing body of evidence from monitoring of farmed red deer in New Zealand that the interaction between lactation and hind body condition score (BCS)/ liveweight influences subsequent conception rate and date. Recent studies on pre-rut versus post-rut calf weaning practices demonstrated effects of lactation on hind BCS and liveweight, calf growth rates and hind conception dates. These studies highlight the need to better understand the "costs" of lactation on reproductive performance, particularly under conditions of nutritional constraints. Keywords: lactation, nutrition, red deer, reproduction

Limit-feeding corn as an alternative to hay for gestating beef cows.

Three experiments were conducted to determine the efficacy of limit-feeding corn-based diets as an alternative to hay for beef cows in gestation and early lactation. Seventy or 71 mature, pregnant Simmental crossbred cows (average weight = 589 +/- 10 kg) were used in each trial. Each of 29 or 30 cows was fed approximately 5 kg of whole shelled corn, 1.2 kg of a pelletted supplement, and 1 kg of hay daily from November to April to meet nutritional needs for gestation. The remaining 41 cows were fed first-cutting round-baled hay free choice. Cows with ad libitum hay intake consumed approximately twice as much feed as cows limit-fed the corn-based diet. Body weight change during the winter was not affected (P > .10) by feeding system in Trials 1 and 2. Limit-feeding the corn-based diet had no detrimental effects on subsequent cow performance or conception rate or on calf weaning weight following summer grazing on pasture. The cost to feed a cow hay was nearly double that of limit-feeding corn-based diet. Two additional experiments were conducted to determine the effect of supplemental monensin (200 mg/d) on performance of gestating Simmental-Angus first-calf heifers fed corn-based diets. In Trial 4, monensin-supplemented heifers were fed 10% less corn than control heifers. In Trial 5, both groups were fed equal amounts of feed. No adverse effects of feeding the corn-based diets were observed. It was concluded from these trials that corn-based diets can meet the nutrient requirements of pregnant beef cattle without adverse effects on production and at a lower cost than feeding hay.