Comparison of two intravaginal progesterone-releasing devices in lactating Holstein cows synchronized with a 5-d GnRH-based timed-AI protocol.

The objective of the study was to compare the effectiveness of CIDR vs. PRID-Delta devices for use in a 5-day Ovsynch protocol for TAI in lactating Holstein cows that were either not in estrus after the end of the voluntary waiting period or non-pregnant and not returning to estrus following the previous AI. Cows fitted with a collar-mounted automated activity monitoring system (Alta Cow Watch) were subjected to a standard 5-d Ovsynch protocol [100 µg of gonadorelin (GnRH) on Day 0 and 500 µg of cloprostenol on Days 5 and 6] and allocated randomly to receive either an intravaginal device containing 1.35 g (CIDR; n = 304) or 1.55 g (PRID ® DELTA; n = 304) of progesterone between Day 0 and 5. All cows received a second administration of GnRH at approximately 56 h and timed-AI (TAI) 72 h after intravaginal device removal. Inseminations were done using conventional frozen-thawed semen. Estrus events prior to TAI were recorded and transrectal ultrasonography was done on Day 0 to determine presence of a corpus luteum (CL) and 33 and 61 d post-TAI, respectively, to diagnose and confirm pregnancy. Cows had an average of 2.2 lactations, 124.3 days in milk, and a milk yield of 43.6 kg/d at enrollment. The overall percentage of cows with a CL at initiation of treatment was 68.8 % and did not differ between treatment groups. Cows with a CL had greater pregnancy per AI (P/AI) at 33 and 61 d post-TAI than cows without a CL (P < 0.01; 46.9 and 42.3 % vs. 32.1 and 27.4 %, respectively). The overall percentage of cows that expressed estrus prior to TAI was 24.8 % and did not differ between treatment groups; however, estrus expression prior to TAI affected P/AI at 33 and 61 d post-TAI (P < 0.01; 53.6 and 49.0 % vs. 38.5 and 33.9 % for those expressing or not expressing estrus, respectively). Pregnancy per AI at 33 d post-TAI tended to differ between treatment groups (P = 0.08; 46.1 vs. 38.5 % for PRID and CIDR groups, respectively) and P/AI at 61 d post-TAI was greater (P < 0.01) for PRID-treated cows (43.8 %) compared to CIDR-treated cows (31.6 %). Thus, PRID-treated cows had lower pregnancy loss than CIDR-treated cows (P < 0.01; 5.0 vs. 17.9 %). Also, treatment with a PRID tended (P = 0.08) to result in fewer twin pregnancies (7.9 vs. 14.5 % for PRID and CIDR treated cows, respectively). In conclusion, lactating dairy cows subjected to a 5-d Ovsynch TAI protocol plus a PRID-Delta had greater P/AI at 61 d post-TAI, lower pregnancy loss between 33 and 61 d post-TAI, and fewer twin pregnancies compared to cows subjected to a 5-d Ovsynch protocol plus a CIDR.

Reproductive outcomes in Holstein heifers synchronized with timed-AI protocols that provide for a lengthened proestrus.

This study compared reproductive outcomes among two protocols for synchronization of ovulation that provide for a lengthened proestrus with the conventional oestradiol-based protocol currently used for timed-AI (TAI). Holstein heifers (13-15 months) at one location were assigned randomly to one of three TAI protocols. Heifers (n = 150) in the 7-day oestradiol benzoate (EB) group received a progesterone device (Cue-Mate) and 2 mg EB on Day 0; 500 µg of cloprostenol (PGF) and Cue-Mate removal on Day 7; 1 mg of EB on Day 8 and TAI on Day 9 (54 h after Cue-Mate removal). Heifers (n = 150) in the 5-day CO-Synch (CO) group received a Cue-Mate and 100 µg of gonadotropin-releasing hormone (GnRH) on Day 2; Cue-Mate removal and PGF (twice, 12 h apart) on Day 7; and GnRH along with TAI on Day 10 (72 h after Cue-Mate removal). Heifers (n = 150) in the J-Synch (JS) group received a Cue-Mate and 2 mg of EB on Day 1; PGF and Cue-Mate removal on Day 7; GnRH and TAI on Day 10 (72 h after Cue-Mate removal). Heifers were inseminated by one technician with frozen-thawed conventional semen from one of four commercially available sires. Plasma progesterone (P4) concentrations (ng/mL) were determined at Cue-Mate removal and TAI. Ovarian ultrasonography was done in a subset of 217 heifers at the initiation of protocols, at Cue-Mate removal; TAI; and 7 days after TAI. Approximately, 28 and 50 days after TAI pregnancy status was determined by ultrasonography. Mean (±SEM) plasma P4 concentration at Cue-Mate removal was greater (p < .01) in CO (6.02 ± 0.2) and JS (6.51 ± 0.2) compared to EB heifers (4.53 ± 0.2). Mean (±SEM) plasma P4 concentration at TAI was lowest in the JS (0.28 ± 0.05), intermediate in CO (0.46 ± 0.02), and greatest in EB heifers (0.66 ± 0.05, p < .01). The diameter of the ovulatory follicle (mean ± SEM) was the smallest in the JS group compared to that in the CO and EB groups (15.8 ± 0.5; 13.9 ± 0.5; and 12.7 ± 0.5 mm for EB, CO and JS, respectively). More (p < .01) heifers in the JS group had their oestrous cycle synchronized (50.0, 78.8 and 82.4% for EB, CO and JS groups), and were pregnant at 28 (40.3, 51.3 and 63.3% for EB, CO and JS groups) and 50 days after TAI (32.6, 46.0 and 60.0% for EB, CO and JS groups). In summary, heifers subjected to the J-Synch TAI protocol had lower P4 at TAI, and better overall response to hormonal treatments, which resulted in increased P/AI at 28 and 50 days after TAI compared to those heifers subjected to either a 7-day EB protocol or a 5-day CO-synch protocol.

A high dose of initial GnRH increased ovulatory response and fertility in Holstein heifers subjected to a progesterone based 5-d CO-Synch protocol.

The objectives of this study were to investigate the effect of presynchronization or dose of GnRH on ovulatory response to initial GnRH, estrus expression and reproductive outcomes in Holstein heifers subjected to a progesterone based 5-d CO-Synch protocol. Heifers were fitted with a collar-mounted automated activity monitoring system on Day -5 and were assigned randomly to one of three groups: 1) G100 (n = 111), a 5-d CO-Synch plus PRID protocol with administration of 100 µg of GnRH at the time of PRID insertion (Day 0), 500 µg of cloprostenol (PGF) at the time of PRID removal (Day 5) and again 24 h later (Day 6); 2) G200 (n = 112), same as G100 except 200 µg GnRH was administered on Day 0; 3) P10 (n = 111), PRID + PGF on Day -5 followed by a 5 d CO-Synch with administration of 100 µg of GnRH on Day 0, PGF at the time of PRID removal (Day 5) and again 24 h later (Day 6). Approximately 72 h after PRID removal (Day 8), all heifers were timed-inseminated (TAI) and concurrently 100 µg of GnRH was administered to those not exhibiting estrus. All inseminations were done by one technician using either sex-sorted (n = 265) or conventional (n = 69) frozen-thawed semen. Transrectal ultrasonography was done to determine ovarian cyclicity and normalcy of the reproductive tract, ovarian dynamics and pregnancy. All heifers were cyclic and ovulatory response to initial GnRH was greater (P < 0.01) in G200 (51.8%) and P10 (47.7%) compared to G100 (27.9%). Estrus expression rate tended to be greater (P = 0.08) in G100 (93.7%) compared to G200 (85.7%) and intermediate in P10 (89.2%). Expression of estrus was associated positively with P/AI at 45 d post-TAI (P < 0.01; 70.2 vs. 31.4% for heifers expressing or not expressing estrus). Heifers in the G200 group had greater P/AI at 30 (P < 0.01) and 45 (P = 0.01) d post-TAI (79.5 and 75.9%, respectively) compared to those in G100 (63.1 and 60.4%) or P10 (64.0 and 62.2%) groups. Pregnancy loss did not differ among treatment groups (overall 3.9%). Results indicate that increasing the dose of the initial GnRH from 100 to 200 µg resulted in increased ovulatory response and improved P/AI in Holstein heifers subjected to a progesterone based 5-d CO-Synch protocol. Although heifers presynchronized with a combination of PRID and PGF had an increased ovulatory response to the initial GnRH, P/AI did not differ from the standard progesterone based 5-d CO-Synch protocol.

Estrous activity and pregnancy outcomes in Holstein heifers subjected to a progesterone based 5-d CO-Synch protocol with or without administration of initial GnRH.

The objectives of this study were to investigate whether estrous activity and its impact on pregnancy outcomes would differ in heifers subjected to a 5 d CO-Synch plus progesterone releasing intravaginal device (PRID) protocol with or without an initial GnRH treatment. Holstein Heifers (n = 308) were fitted with a collar-mounted automated activity monitoring system approximately 1 week prior to the initiation of the synchronization protocol (Day -7). Heifers were assigned randomly to a 5 d CO-Synch plus PRID protocol either with (GnRH; n = 154) or without (NGnRH; n = 154) an initial administration of 100 µg of GnRH at the time of PRID insertion (Day 0). Heifers received a single administration of 500 µg of cloprostenol (PGF) at the time of PRID removal (Day 5) and again 24 h later (Day 6). Approximately 72 h after PRID removal (Day 8), heifers were timed-inseminated (TAI) and concurrently 100 µg of GnRH was administered to those not exhibiting estrus. All inseminations were done by one of two technicians using either sex-sorted (n = 252) or conventional (n = 56) frozen-thawed semen. Transrectal ultrasonography was done on Day 0 to determine ovarian cyclicity and normalcy of the reproductive tract and 30 and 45 d post-TAI to determine and confirm pregnancy, respectively. The percentage of heifers determined to be in estrus following PRID removal was greater in the GnRH than in the NGnRH group (94 vs. 82%, respectively; P < 0.01). The mean interval from PRID removal to the onset of estrus was shorter for GnRH- than NGnRH-treated heifers (50.8 vs. 59.2 h, respectively; P < 0.01). Pregnancy per AI (P/AI) at 30 d post-TAI tended to be greater for GnRH than NGnRH heifers (68 vs. 59%, respectively; P = 0.1). However, P/AI at 45 d post-TAI (65 vs. 57%, respectively) and pregnancy loss between 30 and 45 d post-TAI (6 vs. 4.5%, respectively) did not differ. The association between the interval from PRID removal to the onset of estrus and P/AI at 30 d post-TAI was linearly negative for GnRH heifers; for every 1 h increase in the interval from PRID removal to the onset of estrus, the predicted probability of P/AI at 30 d post-TAI tended (P = 0.08) to be reduced by 2.7%. The association between the interval from PRID removal to the onset of estrus and P/AI at 30 d post-TAI was not significant for NGnRH heifers. In addition, the interval from TAI to subsequent estrus, in non-pregnant heifers, was approximately 3 d longer for the GnRH than the NGnRH group (20.7 vs. 17.5 d, respectively). In summary, the initial GnRH treatment in a 5 d CO-Synch plus PRID protocol increased estrus expression and reduced the interval from PRID removal to the onset of estrus in Holstein heifers and tended to increase P/AI at 30 d, but did not affect P/AI at 45 d post-TAI.

Superovulatory response, anti-Müllerian hormone concentration and antral follicle count in Holstein cattle with short or long anogenital distance.

To understand the mechanisms underlying the inverse relationship between anogenital distance (AGD) and fertility in dairy cattle, we determined if embryo yield and quality differed between cattle of short- and long-AGD (Study 1), and whether anti-Müllerian hormone (AMH), antral follicle count (AFC) and superovulation responses differed by AGD group (Study 2). In Study 1, records of embryo yield and quality in Holstein heifers (n = 43) and cows (n = 14) from two commercial dairy herds were analyzed, retrospectively. Short- and long-AGD groups were based on the median AGD cut-points of 113 and 134 mm, for heifers and cows, respectively. The mean numbers of total (7.4 vs. 9.0; 9.4 vs.12.9), fertilized ova (5.6 vs. 6.2; 6.6 vs. 6.9), and viable embryos (4.4 vs. 4.8; 5.9 vs. 5.3) per heifer and cow did not differ between cattle of short vs. long AGD. Short-AGD cows, however, had greater proportions of fertilized ova (69.7 vs. 53.3%; P = 0.07) and viable embryos (62.1 vs. 41.1%; P = 0.03) than long-AGD cows. The odds of short-AGD cows yielding fertilized ova and viable embryos were 2.0 and 4.0 times greater, respectively, than the odds of long-AGD cows. In Study 2, lactating cows (n = 24) of a research herd had their AGD categorized as in Study 1, and AFC, AMH, and superovulation responses (i.e., no. of preovulatory follicles [≥ 10 mm] and CL) were determined. Mean AFC (27 ± 4.5 vs. 21 ± 4.0) and CL (9 ± 1.6 vs. 7 ± 1.4) per cow did not differ between short- and long-AGD groups. Serum AMH concentration (pg/mL) was lesser in short-AGD cows compared with long-AGD cows (114 ± 30.4 vs. 200 ± 26.8; P = 0.05), but the no. of preovulatory follicles was greater (15 ± 1.9 vs. 8 ± 1.7; P = 0.01) in short-AGD than in long-AGD cows. The overall proportion of follicles ≥10 mm was also greater in short-AGD cows than in long-AGD cows (56 vs 44%; P = 0.03). Preovulatory follicle number was affected by a parity x AGD group interaction (P = 0.04), with multiparous short-AGD cows accounting for the largest number of follicles. No associations were found among AGD, AFC and AMH. The associations between AFC and superovulation responses (follicles: r = 0.67, and CL: 0.58; P < 0.01) were moderate but AMH was not associated with superovulation responses. In summary, whereas AGD-associated differences in the yield and quality of embryos were not evident in heifers, the proportions of fertilized ova and viable embryos were greater in short-AGD than in long-AGD cows. In addition, the proportion of preovulatory follicles, an indicator of superovulatory response, was greater in short-AGD cows than in long-AGD cows.

Economic comparison of an ear tag automated activity monitor for estrus detection with timed-AI in Holstein heifers.

The objective of this study was to compare the economic performance of an ear tag automated activity monitor system (AAM) versus a timed-AI (TAI) protocol in Holstein heifers. In total, 340 heifers were enrolled onto the study at 13.5 mo of age and randomly assigned to receive either an AAM (n = 170) or TAI (n = 170) protocol before breeding eligibility (D 0). Heifers in the AAM group were fitted with an ear tag AAM and bred based on high activity alert from the system. Heifers in the TAI group received a progesterone releasing intravaginal device on D -8, followed by device removal and prostaglandin on D -3 and gonadotropin-releasing hormone with TAI on D 0. In both treatments, the majority of heifers received sex-sorted semen for the first AI and conventional semen for subsequent AIs, with three opportunities to become pregnant. All heifers were diagnosed for pregnancy approximately 25 d post AI using transrectal ultrasonography, with confirmation at 30 and 45 d. Non-pregnant heifers in the TAI group, were resynchronized using the same TAI protocol. A partial budget was used to compare the costs and benefits of switching from a TAI to an AAM protocol in heifers, including protocol, labour, and rearing costs for each treatment, as well as estimated calf and milk value. Sensitivity analyses were also conducted to determine the effect of pregnancy per AI (P/AI), outsourcing AI, AAM tag cost and herd size on the net outcome. There was no difference in overall P/AI or days to pregnancy between treatments. However, number of AI was greater in the TAI than the AAM group. For the first AI, the P/AI was less in the TAI compared to the AAM group; however, the interval to first AI was less in TAI. There was minimal difference in performance for the second and third AI. There was a net gain of $11.97 per heifer when switching from a TAI to AAM protocol, due to the increased P/AI to the first AI and reduced cost of hormones. Several variables in the sensitivity analyses affected the net outcome. Considering only the first AI, switching to an AAM collar and a larger herd size all increased the net gain. Considering a greater P/AI to the first AI in the TAI group, outsourcing AI, using more AAM ear tags, and smaller herd sizes resulted in a net loss when switching from TAI to AAM. The AAM system resulted in exceptional P/AI and may be an economically viable alternative to improve heifer reproductive efficiency in herds with suboptimal P/AI to TAI.

Impact of genetic potential for residual feed intake and diet fed during early- to mid-gestation in beef heifers on carcass characteristics and meat quality attributes of their castrated male offspring.

Carcass attributes of steers were examined for influences of selection for residual feed intake (RFI), and exposure to different levels of prenatal nutrition. Heifers characterized for RFI corrected for backfat were mated to bulls with genetic potential for either High-RFI or Low-RFI, such that the progeny were expected to be H/H or L/L RFI (sire/dam). Pregnant heifers were assigned to a low diet (Ldiet; 0.40 kg/d ADG), or moderate diet (Mdiet; 0.57 kg/d ADG), from 30 to 150 days of gestation, after which all heifers were managed similarly. Steer offspring (n = 23) were also managed similarly until slaughter. Dressing percentage of steers from H-RFI dams/sires exposed to Ldiet during gestation was lower than all other groups (P = 0.02). Marbling was greater for steers from H-RFI parents, as was fat content of longissimus thoracis et lumborum and triceps brachii (P ≤ 0.02). Results suggest that parental selection for RFI and prenatal maternal diet can influence carcass characteristics of progeny.

Comparison of two intravaginal progesterone-releasing devices in shortened-timed artificial insemination protocols in beef cattle.

Commercially available intravaginal progesterone (P4) devices differ in shape, surface area and P4 load, which may affect the resulting pregnancy per AI (P/AI) following timed-AI (TAI). The objective of this study was to compare two intravaginal P4 devices on estrus rate, follicular dynamics and P/AI in beef cattle subjected to shortened-TAI protocols. In Expt. 1, nulliparous heifers were randomly assigned to a P4-releasing intravaginal device (PRID-Delta, 1.55 g P4) or a controlled internal drug release (CIDR, 1.38 g P4) at the initiation of a J-synch protocol. Heifers that displayed estrus 72 h following device removal were TAI, or if not in estrus given GnRH at 72 h and TAI at 90 h. In Expt. 2, nulliparous heifers and non-suckling cows were randomly assigned to either PRID or CIDR groups and either 1 or 2 mg of estradiol benzoate (EB) at initiation of a J-synch protocol. All cattle were TAI concurrent with GnRH 72 h after device removal. In Expt. 3, nulliparous heifers and suckling cows were randomly assigned to either PRID or CIDR groups and initiated a 5-d Cosynch protocol, with TAI concurrent with GnRH 72 h following device removal. In each experiment, cattle received estrus detection patches at device removal, which were then scored from 0 to 3 based on color change between initial application and TAI; 0 = unchanged, 1 = ≤50% change, 2 = >50% change, 3 = missing. Estrus was defined to have occurred when the patch was scored 2 or 3. Transrectal ultrasonography was used to determine cyclicity, diagnose pregnancy in all experiments, and the size of the ovulatory follicle in Expt. 3. In Expt. 1, the estrus rate was greater (72.0% vs. 61.0%; P = 0.04) in the PRID compared to the CIDR group. In Expt. 2, a parity by EB dose interaction (P = 0.02) was attributed to an increased estrus rate (52.8% vs. 41.4%; P = 0.05) in heifers given 1 vs. 2 mg EB. In Expt. 3, there was no difference in the ovulatory follicle diameter at device removal (P = 0.22) or TAI (P = 0.28) between P4 groups. Treatment with a PRID tended (P = 0.10) to increase the P/AI in cows compared to a CIDR (73.5% vs. 61.0%). In all experiments combined, the overall P/AI tended to increase (55.2% vs. 51.0%; P = 0.08) and P/AI in cattle exhibiting estrus increased (64.4% vs. 59.7%; P = 0.02) in cattle given a PRID compared to those given a CIDR, respectively. In summary, the type of intravaginal P4 device affected estrus response and P/AI following TAI in beef cows.

Relationship of anogenital distance with fertility in nulliparous Holstein heifers.

Anogenital distance (AGD), defined as the distance from the center of the anus to the base of the clitoris, in lactating dairy cows of first and second parity, has been reported to be inversely related to fertility and moderately heritable. Thus, AGD may be a useful reproductive phenotype for future genetic selection to improve fertility. The objectives of this study were to (1) characterize AGD in nulliparous dairy heifers; and (2) determine if the inverse relationship between AGD and fertility, found in lactating dairy cows, is also evident in nulliparous heifers. We measured AGD in 1,692 Holstein heifers from 16 herds in Western Canada (Alberta and British Columbia) and one herd in the United States (Washington State). Data were analyzed using MEANS, UNIVARIATE, LOGISTIC, ROC, GLIMMIX, and LIFETEST procedures of SAS (SAS Institute Inc.). Mean (±standard deviation) age at AGD measurement was 13.9 ± 1.5 mo, and AGD was normally distributed with a mean of 107.3 ± 10.5 mm, ranging from 69 to 142 mm. With every 1-mm increase in AGD, the predicted probability of pregnancy was reduced by 1.9%. Receiver operating characteristic curve analysis was used to determine the optimum threshold AGD that predicted the probability of pregnancy. Based on the optimum threshold AGD, data from heifers were categorized into short (≤110 mm) and long (>110 mm) AGD groups, and associations between AGD groups and fertility measures were determined. Heifers with short AGD required fewer services per conception (1.5 vs. 1.7) than heifers with long AGD. Consequently, heifers with short AGD conceived earlier (448.4 vs. 454.3 d) and had greater pregnancy to first AI than those with long AGD (58.3 vs. 49.6%). Moreover, heifers with long AGD had reduced hazard (hazard ratio of 0.59) for pregnancy up to 450 d of life compared with those with short AGD. In summary, AGD was normally distributed and highly variable in the population. In addition, an inverse relationship between AGD and fertility measures in nulliparous heifers was evident, confirming an earlier report of a similar relationship in lactating dairy cows. These findings strengthen the potential for AGD to be used as a fertility trait and management tool in future selection programs.

Effects of dietary conjugated linoleic acid on metabolic status, BW and expression of genes related to lipid metabolism in adipose tissue of dairy cows during peripartum.

Conjugated linoleic acid (CLA) dietary supplementation reduces milk fat content and yield, but its effects on lipid metabolism and energy status remain controversial. The objective of this study was to investigate the effects of dietary CLA on adipose tissue (AT) mRNA abundance of genes related to lipid metabolism, plasma indicators of metabolic status, body condition score (BCS) and BW changes in dairy cows. Sixteen multiparous Holstein cows (3.2 ±â€¯1.4 lactations, 615 ±â€¯15 kg BW) were randomly assigned to treatments: 1) CLA; rumen-protected CLA (75 g/d) or 2) Control; equivalent amount of rumen inert fatty acid (FA) as the previous diet (78 g/d), from -20.2 ±â€¯3.2 (mean ±â€¯SEM) to 21d relative to calving (d 0). Subcutaneous AT was biopsied from the tail-head region at d 21 to determine the mRNA abundance of genes related to lipid metabolism. Blood samples were collected at -20.2 ±â€¯3.2, 0, 7, 14 and 21d relative to calving to determine plasma non-esterified fatty acids (NEFA), beta-hydroxybutyrate (BHBA), insulin and glucose. Conjugated linoleic acid decreased milk fat yield and milk fat content by 15 and 16%, respectively. Cows fed CLA had lower plasma NEFA and BHBA and greater glucose and insulin concentrations (P < 0.05). Mean BCS at 21d postpartum was greater (P < 0.01; 2.89 vs 2.25), and BCS loss from the day of enrollment to 21d postpartum was reduced (P < 0.01; -0.13 vs -0.64) in the CLA group. The expression of acylcoenzyme A oxidase, carnitine palmitoyltransferase 1A, hormone-sensitive lipase, ß2 adrenergic receptor and acetyl-CoA carboxylase was downregulated by CLA supplementation, whereas the expression of sterol regulatory element binding protein, lipoprotein lipase and peroxisome proliferator-activated receptor gamma was upregulated (P < 0.01). In summary, CLA-supplemented cows showed signs of better metabolic status and less severe fat mobilization. Moreover, CLA increased mRNA abundance of genes related to lipogenesis and decreased mRNA abundance of genes related to FA oxidation and lipolysis in the AT of dairy cows during early lactation.

The effect of altering the timing of GnRH administration and artificial insemination in a modified 5-d CO-Synch protocol using sex-sorted semen in dairy heifers.

The objective was to optimize fertility in a modified 5-d CO-Synch protocol by altering the timing of GnRH administration and AI. Holstein heifers (14-16 mo) received a controlled internal drug releasing device (CIDR) on d 0 and on d 5, CIDR were removed, prostaglandin F2α was administered and estrus detection patches were applied. Estrus was detected at 36, 48, 56 and 72 h after CIDR removal. In Experiment 1, control heifers (n = 195) received GnRH concurrent with timed-AI (TAI) 72 h after CIDR removal, regardless of expression of estrus. Treatment heifers expressing estrus at 36 or 48 h were AI at 56 h (n = 101) and the remaining heifers were randomly assigned to one of two groups: GnRH administration at 56 h and TAI at 72 h (GnRH56, n = 147) or GnRH administered concurrently with TAI at 72 h (GnRH72, n = 148). In Experiment 2, heifers expressing estrus at 36 or 48 h following CIDR removal were AI at 56 h (n = 118) and the remaining heifers were either TAI at 72 h (TAI72, n = 102) or 80 h (TAI80, n = 102), with only heifers not displaying estrus by TAI given GnRH concurrent with AI. All heifers were inseminated with sex-sorted semen and pregnancy diagnosis was performed at 28 d following TAI. In Experiment 1, estrus rate (P = 0.81) and pregnancy per AI (P/AI; P = 0.34) did not differ among control, GnRH56 and GnRH72 groups, so GnRH56 and GnRH72 groups were combined into one split-TAI (STAI) group. The P/AI was greater in heifers displaying estrus by 48 h compared to those not displaying estrus and receiving GnRH in both groups (69.5 vs. 31.3%; P < 0.01) and there was a tendency for P/AI to increase in STAI heifers displaying estrus compared to control heifers displaying estrus (73.3 vs. 62.1%; P = 0.10). In Experiment 2, the estrus rate was increased in TAI80 compared to TAI72 heifers (81.4 vs. 62.7%, P < 0.01); however, there was no difference in P/AI (P = 0.74). Heifers displaying estrus in the TAI72 group had a greater P/AI than heifers not displaying estrus in either group (P < 0.01) and tended to have a greater P/AI than heifers in estrus in the TAI80 group (87.5 vs. 69.9%, P = 0.07). Across both experiments, P/AI was increased in heifers that displayed estrus before AI compared with heifers that did not and performing a STAI tended to increase P/AI in heifers that displayed estrus before AI. Other attempts made to optimize P/AI in the modified 5-d CO-Synch protocol by altering the timing of GnRH administration and/or AI were unsuccessful.

Performance and optimization of an ear tag automated activity monitor for estrus prediction in dairy heifers.

The objectives of this study were to evaluate the performance of the SCR eSense ear tag automated activity monitor (AAM) to detect estrus behavior in Holstein heifers and to determine the optimal time from estrus alert to artificial insemination (AI) using sex-sorted or conventional semen. In total, 281 heifers were fitted with the AAM once eligible for breeding (>13.5 m of age). For the first AI, estrus was synchronized using 500 µg of cloprostenol (PGF), given 14 d apart, and heifers were given estrus detection patches (Estrotect™) after the second PGF. Heifers were inseminated at randomly attributed times after high activity alert from the AAM system or if the estrus patch had ≥ 50% colour change. Most heifers received sex-sorted semen for the first AI and conventional semen for subsequent inseminations. Pregnancy diagnosis was performed at 30 d post AI and heifers had four opportunities to become pregnant. In a subset of heifers (n = 149), ovaries were scanned every 12 h from the time of AI until ovulation (OV). The system recorded a heat index (measure of estrus strength), maximum activity change, maximum rumination change and duration of high activity. The sensitivity was 91.0%, with a false positive and false negative rate of 8.0%, and the positive predictive value to detect true estrus events was 83.5%. Pregnancy per AI to first AI was 67.6% and 97.9% of heifers become pregnant after four inseminations. Most false positive estrus events had a heat index < 45 and a rumination change < -20, while false negative events had a rumination change ≥ -20. Odds of pregnancy was not associated with any estrus characteristics measured by the system. However, pre-ovulatory follicle diameter had a weak correlation (r < 0.25) with all estrus characteristics. The average (range) interval of onset of high activity, peak activity and end of high activity to OV was 28 h (16-46 h), 22 h (10-40 h) and 16 h (0-36 h), respectively. For conventional semen, each hour increase in interval from activity onset or peak activity to AI reduced the predicted probability of pregnancy by 3.8 and 4.2%, respectively. For sex-sorted semen, the relationship between activity onset or peak activity to AI and predicted probability of pregnancy was quadratic, but not significant. Overall, the SCR eSense ear tag AAM performed well and strategies to identify false positive and false negative estrus events, along with optimization of timing of AI, should further improve performance in Holstein heifers.

Relationships between early postpartum nutritional and metabolic profiles and subsequent reproductive performance of lactating dairy cows.

The objective of this study was to examine the relationship between early postpartum nutritional and metabolic profiles in lactating dairy cows and subsequent pregnancy to first artificial insemination (AI), pregnancy by 150 d in milk (DIM) and pregnancy loss after first AI. A blood sample was collected between 2 and 14 (median = 9) DIM from 869 lactating Holstein cows to determine serum concentrations of metabolites, minerals, and liver enzymes. Associations between analytes and fertility were determined using an adjusted odds ratio (OR). Overall, pregnancy to first AI, pregnancy by 150 DIM and pregnancy loss after first AI were 37.9, 65.8 and 11.2%, respectively. Compared to cows pregnant to first AI, non-pregnant cows had higher (P < 0.05) serum concentrations of aspartate aminotransferase (AST; 92.3 ± 1.6 vs. 84.6 ± 2.0 U/L), non-esterified fatty acid (NEFA; 0.73 ± 0.02 vs. 0.54 ± 0.02 mmol/L), and haptoglobin (0.77 ± 0.04 vs. 0.60 ± 0.05 g/L), and lower (P < 0.05) serum concentrations of Mg (0.86 ± 0.02 vs. 0.89 ± 0.02 mmol/L) and cholesterol (2.1 ± 0.03 vs. 2.4 ± 0.04 mmol/L). Cows non-pregnant by 150 DIM had lower (P < 0.05) serum concentration of Mg (0.86 ± 0.02 vs. 0.88 ± 0.02 mmol/L) and higher serum concentration of haptoglobin (0.82 ± 0.1 vs. 0.63 ± 0.09 g/L) than cows pregnant by 150 DIM. Cows that lost their pregnancy after first AI had greater serum concentrations of haptoglobin than those that did not undergo pregnancy loss (1.1 ± 0.09 vs. 0.5 ± 0.05 g/L; P < 0.01). The odds of pregnancy to first AI (OR; 95% confidence interval [CI]) decreased with increased serum concentrations of AST (OR = 0.99; 95% CI = 0.98-1.00), NEFA (OR = 0.54; 95% CI = 0.37-0.79) and haptoglobin (OR = 0.80; 85% CI = 0.66-0.96) and increased with inreased concentrations of Mg (OR = 3.24; 95% CI = 1.09-9.62) and cholesterol (OR = 1.24; 95% CI = 1.02-1.54). Increased serum concentrations of Mg (OR = 3.06; 95% CI = 1.02-9.20) and haptoglobin (OR = 0.92; 95% CI = 0.69-0.97) were associated with greater and lower odds of pregnancy by 150 DIM, respectively. Only increased concentrations of haptoglobin (OR = 1.58; 95% CI = 1.13-2.20) were associated with increased odds of pregnancy loss after the first AI. In summary, greater early postpartum serum concentrations of AST, NEFA and haptoglobin were associated with reduced fertility, but the opposite was observed for serum concentrations of Mg and cholesterol. In addition, serum concentrations of haptoglobin were positively associated with pregnancy loss.

The relationships among sire's predicted transmitting ability for daughter pregnancy rate and cow conception rate and daughter's reproductive performance in Canadian Holstein cows.

The objectives of this study were to (1) characterize the variability for sire's predicted transmitting ability (PTA) for daughter's pregnancy rate (DPR) and cow conception rate (CCR), (2) determine the relationships among sire's PTA for DPR, sire's PTA for CCR, daughter's parity, and daughter's 305-d mature-equivalent (ME) milk production, and (3) evaluate the associations among sire's PTA for DPR and CCR and daughter's reproductive performance [pregnancy to first artificial insemination (P/AI), pregnancy by 150 d in milk (PR150) and pregnancy loss (PL) after first AI] in Canadian Holstein cows. The data were obtained from 822 lactating Holstein cows from 10 commercial dairy herds located in Alberta. Overall mean (range) for sire's PTA for DPR and CCR was -0.09 (-9.6 to 8.2) and -0.05 (-9.9 to 7.4), respectively. Sire's PTA for DPR was strongly and positively associated with sire's PTA for CCR (r = 0.89; P < 0.01). Sire's PTA for DPR and CCR were weakly and negatively associated with parity (r = -0.15 and -0.17, respectively; P < 0.01); however, the amount of phenotypic variation in sire's PTA for DPR and CCR explainable by parity was small (coefficient of determination; R2 = 0.02). The daughter's 305-d ME milk production tended to be weakly but positively associated with sire's PTA for DPR (r = 0.06; P = 0.07) and CCR (r = 0.06; P = 0.10); however, the amount of phenotypic variation in daughter's 305-d ME milk production explainable by changes in sire's PTA for DPR or CCR was small (R2 = 0.004 and 0.003, respectively). Overall P/AI, PR150 and PL were 38, 65 and 12%, respectively. Sire's PTA for DPR tended to be associated with P/AI (P = 0.08) but was significantly associated with PR150 (P = 0.03). For every unit increase in sire's PTA for DPR, the estimated probabilities for P/AI and PR150 increased by 6.2 and 7.5%, respectively. Sire's PTA for CCR was not associated with P/AI or PR150. Neither sire's PTA for DPR nor CCR were associated with PL. In summary, sire's PTA for DPR and CCR were highly variable and positively correlated. Sire's PTA for DPR was associated with daughter's P/AI and PR150, but sire's PTA for CCR was not associated with any of the measured reproductive outcomes. Therefore, selecting sires with high PTA for DPR has the potential to improve the reproductive efficiency of Canadian dairy herds.

The association of circulating prepartum metabolites, minerals, cytokines and hormones with postpartum health status in dairy cattle.

The objectives were to evaluate differences in circulating prepartum metabolites, minerals, cytokines and hormones based on postpartum disease category and determine critical circulating concentrations of prepartum analytes associated with postpartum disease in 229 cattle from 11 commercial dairies in Alberta, Canada. Blood was collected at 8.8 ± 2.1 d prepartum and analyzed for a wide array of analytes. Cattle were categorized as healthy (n = 76) or as having inflammatory (INF; n = 28), metabolic (MET; n = 34) or inflammatory and metabolic (INFMET; n = 91) postpartum diseases. The prepartum circulating concentrations of Cu were lesser (0.84 vs. 0.90 µg/mL; P = 0.02) and concentrations of Mo (19.1 vs. 16.5 ng/mL; P = 0.04) and NEFA (0.27 vs. 0.18 mmol/L; P = 0.01) were greater in INFMET cattle compared with healthy cattle. The critical threshold for Cu, Mo and NEFA prepartum concentration that predicted INFMET was ≤ 0.81 µg/mL (sensitivity 45.5% and specificity 74.3%), ≥ 9.91 ng/mL (sensitivity 70.0% and specificity 52.7%) and ≥ 0.19 mmol/L (sensitivity 62.2% and specificity 79.7%), respectively. Regardless of differences in the prepartum circulating concentrations of Cu, Mo and NEFA among healthy cattle and those with postpartum disease, the use of these analytes to predict the incidence of postpartum diseases was limited.

Relationship between body condition score loss and mRNA of genes related to fatty acid metabolism and the endocannabinoid system in adipose tissue of periparturient cows.

The endocannabinoid system (ECS) controls feed intake and energy balance in nonruminants. Recent studies suggested that dietary management alters the expression of members of the ECS in the liver and endometrium of dairy cows. The aim of this study was to determine the relationship between body condition score (BCS) loss and the mRNA abundance of genes related to fatty acid metabolism and the ECS in the subcutaneous adipose tissue (AT) of dairy cows. The BCS was determined in multiparous (3.2 ± 0.5 lactations) Holstein cows at -21 and 42 days relative to calving (designated as d = 0). Cows were grouped into three categories according to BCS loss between both assessments as follows: (1) lost ≤0.25 unit (n = 8, low BCS loss (LBL)), (2) lost between 0.5 and 0.75 units (n = 8, moderate BCS loss (MBL)) and (3) lost ≥1 unit (n = 8, high BCS loss (HBL)). Concentrations of haptoglobin and non-esterified fatty acids (NEFAs) were determined in plasma. Real-time PCR was used to determine mRNA abundance of key genes related to fatty acid metabolism, inflammation and ECS in AT. Milk yield (kg/day) between week 2 and 6 post-calving was greater in the LBL group (49.4 ± 0.75) compared to MBL (47.9 ± 0.56) and HBL (47.4 ± 0.62) groups (P < 0.05). The overall mean plasma haptoglobin and NEFA concentrations were greater in MBL and HBL groups compared with the LBL group (P < 0.05). The mRNA abundance of TNF-α, Interleukin-6 (IL-6) and IL-1ß was greatest at 21 and 42 days post-calving in HBL, intermediate in MBL and lowest in LBL groups, respectively. Cows in the HBL group had the greatest AT gene expression for carnitine palmitoyltransferase 1A, hormone sensitive lipase and adipose triglyceride lipase at 21 and 42 days post-calving (P < 0.05). Overall, mRNA abundance for very long chain acyl-CoA dehydrogenase and peroxisome proliferator-activated receptor gamma, which are related to NEFA oxidation, were greater in MBL and HBL groups compared to the LBL group at 42 days post-calving. However, mRNA abundance of fatty acid amide hydrolase was lower at 21 and 42 days post-calving in HBL cows than in LBL cows (P < 0.05). In summary, results showed a positive association between increased degree of BCS loss, inflammation and activation of the ECS network in AT of dairy cows. Findings suggest that the ECS might play an important role in fatty acid metabolism, development of inflammation and cow's adaptation to onset of lactation.

Postpartum health disorders in lactating dairy cows and its associations with reproductive responses and pregnancy status after first timed-AI.

The objective was to evaluate the association between postpartum health disorders, reproductive responses and pregnancy status in lactating multiparous cyclic Holstein cows. Cows were retrospectively categorized as healthy (n = 70) or sick (n = 60) based on postpartum health records and serum metabolites. Sick cows were further categorized as having metabolic (MET; n = 35), infectious (INF; n = 15), or both diseases (MET/INF; n = 10). Blood samples were collected on d 7 and 14 after calving to determine serum concentrations non-esterified fatty acids (NEFA), ß-hydroxybutyrate (BHB) and aspartate aminotransferase (AST), on d 0 (TAI), 8, 16, 18 and 20 after TAI to determine concentrations of progesterone (P4; d 0, 8, 16, 18 and 20) and prostaglandin F metabolite (PGFM; d 16, 18 and 20) and interferon-stimulated gene-15 (ISG15; d 16) relative mRNA expression. Cyclicity was determined by transrectal ultrasonography 30 d postpartum and cows were subjected to a GnRH-based TAI protocol (to classify cows bearing a visible CL as cyclic). Prediction of pregnancy status on d 16 after TAI was determined by ISG15 mRNA gene expression relative to ß actin and following, pregnancy was diagnosed by transrectal ultrasonography at 32 and 60 d after TAI. An interaction (P = 0.04) between occurrence of disease and pregnancy status was detected for the expression of ISG15 in blood, with healthy pregnant healthy cows having the greatest relative expression of ISG15. Postpartum health disorders were associated with reduced concentration (P < 0.05) of serum P4 post TAI. However, serum P4 concentrations at TAI were greater (P = 0.01) in sick cows (0.65 ±â€¯0.09, 0.86 ±â€¯0.13 and 0.75 ±â€¯0.10 ng/mL for MET, INF and MET/INF cows, respectively) compared with that in healthy cows (0.24 ±â€¯0.10 ng/mL). Serum concentrations of PGFM after TAI was reduced in healthy cows, regardless of pregnancy status. Pregnancy status on d 16 after TAI predicted by ISG15 mRNA expression and P/AI on d 32 and 60 after TAI based on ultrasonography, were negatively affected (P < 0.05) by occurrence of health disorders. Similarly, pregnancy loss from d 16 to 32 and d 16 to 60 after TAI was greater (P < 0.05) in sick cows compared to that in healthy cows. However, neither P/AI nor pregnancy loss were associated to the category of postpartum health disorder. Cows affected by postpartum health disorders had overall reduced P4 and greater PGFM serum concentrations after TAI, which were associated with reduced pregnancy success and enhanced pregnancy loss. Collectively, our findings support the hypothesis of a carryover effect of disease on reproductive responses, embryo survival and maintenance of pregnancy in lactating dairy cows independent of the category of postpartum health disorder.

Comparison of the effects of two shortened timed-AI protocols on pregnancy per AI in beef cattle.

The objective was to compare pregnancy per AI (P/AI) between two shortened timed-AI (TAI) protocols in beef cattle. This study also determined whether administration of eCG in heifers and timing of AI in cows would affect P/AI. Cattle were submitted at random to either a modified 5-d Co-synch protocol (Day 0 = progesterone releasing device (CIDR); Day 5 = CIDR removal and 500 µg of cloprostenol (PGF); Day 8 = 100 µg GnRH concurrent with AI) or J-synch protocol (Day 0 = CIDR insertion and 2 mg of estradiol benzoate i.m.; Day 6 = CIDR removal and 500 µg PGF; Day 9 = 100 µg GnRH concurrent with AI). In Experiment 1, 1135 heifers (13-15 mo of age) received an estrus detection patch (Estrotect™) on Day 5 and 579 were selected at random to receive 300 IU of equine chorionic gonadotropin (eCG) at the time of CIDR removal. Patches were scored from 0 to 3 based on color change between initial application and AI; 0 = unchanged, 1 = ≤ 50% change, 2 = > 50% change, 3 = missing. Estrus was defined to have occurred when the patch was scored 2 or 3. In Experiment 2, 399 cyclic, non-lactating beef cows from 1 location were submitted to either the modified 5-d Co-synch or J-synch protocol and within each protocol cows were TAI at either 66 ±â€¯1 (n = 199) or 72 ±â€¯1 h (n = 200) following CIDR removal. Transrectal ultrasonography was used in both experiments to determine presence of a corpus luteum (CL) on Day 0, and to diagnose pregnancy 35 d after TAI. In Experiment 1, eCG increased estrus rate only in heifers without a CL on day 0 that were submitted to the modified 5-d Co-synch protocol (41.9 vs. 69.6%). Heifers submitted to the J-synch protocol had greater (P = 0.03) P/AI compared with those in the modified 5-d Co-synch (48.7 vs. 41.1%) and heifers that expressed estrus before AI had increased (P < 0.0001) P/AI compared to those that did not (53.6 vs. 36.5%). Administration of eCG and presence of a CL tended to affect P/AI (P = 0.13). In Experiment 2, cows submitted to the J-synch protocol tended (P = 0.07) to have greater P/AI compared to those in the modified 5-d Co-synch (74.1 vs. 66.5%). There was no association between P/AI and timing of AI. In summary, the J-synch protocol resulted in greater P/AI than the modified 5-day Co-synch protocol in heifers and cows. Administration of eCG increased estrus rate in heifers without a CL at the start of the protocol and tended to improve P/AI in all heifers. Timing of AI (66 vs. 72 h) had no effect on P/AI in cows subjected to either TAI protocol.

Anti-Müllerian hormone in grazing dairy cows: Identification of factors affecting plasma concentration, relationship with phenotypic fertility, and genome-wide associations.

The objectives of this study were to (1) characterize the distribution and variability of plasma anti-Müllerian hormone (AMH) concentration; (2) evaluate factors associated with phenotypic variation in plasma AMH; (3) examine the associations between categories of plasma AMH and reproductive outcomes [pregnancy to first artificial insemination (P/AI), and pregnancy rates within 21, 42, and 84 d after the mating start date (MSD)]; (4) estimate pedigree and genomic heritability for plasma AMH; and (5) identify and validate SNP associated with phenotypic variation in plasma AMH. Plasma AMH concentration (pg/mL) was determined from a blood sample collected (mean ± standard deviation) 10 ± 2 d after first insemination at detected estrus (IDE) in 2,628 first- and second-parity Irish dairy cows. Overall, plasma AMH had a positively skewed distribution with mean (± standard deviation), median, minimum, and maximum concentrations of 326 ± 231, 268, 15, and 2,863 pg/mL, respectively. Plasma AMH was greatest for Jersey, followed by Holstein × Jersey, Holstein × Norwegian Red, and Holstein cows (410, 332, 284, and 257 pg/mL, respectively). Second-parity cows had greater plasma AMH than first-parity cows (333 vs. 301 pg/mL, respectively). Samples collected at 7 and 8 d after first IDE had lesser plasma AMH than those collected on d 9, 10, 11, 12, and 13 after first IDE (291 and 297 vs. 317, 319, 331, 337, and 320 pg/mL). Plasma AMH was not associated with either body condition score at first IDE or the interval from calving to MSD. Cows were categorized into low (≤150 pg/mL; n = 526; lowest 20%), intermediate (>150 to ≤461 pg/mL; n = 1,576; intermediate 60%), and high AMH (>461 pg/mL; n = 526; highest 20%) groups based on plasma AMH, and associations with reproductive outcomes were tested. Cows with high and intermediate plasma AMH had 1.42- and 1.51-times-greater odds of becoming pregnant within 84 d after the MSD than those with low plasma AMH (90.3 and 90.8 vs. 86.8%, respectively); however, P/AI and pregnancy rate within 21 and 42 d after the MSD did not differ among AMH categories. Plasma AMH was moderately heritable (pedigree heritability of 0.40 ± 0.06 and genomic heritability of 0.45 ± 0.05), and 68 SNP across Bos taurus autosomes 7 and 11 were associated with phenotypic variation in plasma AMH. Out of 68 SNP, 42 were located in a single quantitative trait locus on Bos taurus autosome 11 that harbored 6 previously identified candidate genes (NR5A1, HSPA5, CRB2, DENND1A, NDUFA8, and PTGS) linked to fertility-related phenotypes in dairy cows.

Evaluation of infrared thermography compared to rectal temperature to identify illness in early postpartum dairy cows.

This study evaluated and compared infrared thermography (IRT) and rectal temperature (RT) as screening tests to identify sick transition dairy cows. Holstein cows (n = 72; 42 primiparous) had RT and IRT temperatures taken daily from 1 to 12 days in milk (DIM). Health examinations were performed daily to diagnose retained fetal membrane, milk fever and metritis, and blood was analyzed for ß-hydroxybutyrate at 6 and 9 DIM to diagnose ketosis. Plasma concentrations of cortisol, interleukin-6, tumor necrosis factor α and serum amyloid A at 3, 6, 9 and 12 DIM were included as additional indicators of illness. Cows were categorized as true sick if clinically diagnosed with an illness, or if at least 2 blood parameters were above the normal range. Diagnostic test performances for RT and IRT variables were determined for each variable at a test referent value that provided the highest Youden's (J) index. The best performing screening test depended on the definition of true sickness. In general, the J index for RT was 0.15-0.17 whereas the highest J index for the IRT variables was 0.22 for the mean eye temperature and 0.19 for the mean cheek temperature. Infrared thermography was at least comparable to RT and some IRT variables performed better as a screening tests than RT. Future studies into the automation of IRT for surveillance of early postpartum diseases is warranted.