Identification of nonpregnant beef cows based on CL size vs. luteal blood perfusion at 21 days after timed artificial insemination

The aim was to evaluate the efficiency of two different ultrasonographic systems, Doppler mode vs. Two-dimensional mode (B mode), to identify the pregnancy status of beef cows and heifers on day 21 (D21) after Timed Artificial Insemination (TAI). The experiment was performed on a commercial beef farm in central-west region of Brazil using 1895 Nelore heifers and cows. All females had ovulation synchronized for a TAI that was performed on D0. Twenty-one days after the TAI, all animals had their ovaries evaluated by ultrasound for pregnancy diagnosis based on the size of the corpus luteum (CL). Using B mode ultrasonography, females without a CL or with a CL ≤ 10 mm in diameter were considered nonpregnant, whereas females with a CL > 10 mm in diameter were considered potentially pregnant. After the B mode examination, the Doppler mode was turned on, and the CL was evaluated by the subjective percentage of blood perfusion in the total area of the CL. Using Doppler mode, females were considered nonpregnant if they had no CL or the CL had ≤25 % of the total area with detectable blood perfusion, whereas animals with >25 % blood perfusion in the CL were considered potentially pregnant. The results for each method (potentially pregnant or nonpregnant) were later compared with the gold standard technique, which was a pregnancy diagnosis on D33 after TAI using ultrasound with visualization of an embryonic heartbeat. The accuracy was determined using the 2 × 2 contingency table approach. The area under the curve using the receiver operating characteristic curve for Doppler mode and B mode were 0.929 and 0.902 (P < 0.01), respectively. There were almost no false negatives (designated non-pregnant but later pregnant at D33) with either technique (0.2 % vs. 0.3 %; P = 0.65 for Doppler mode vs. B mode, respectively). False positives (designated pregnant but non-pregnant on D33) were greater for B mode compared to Doppler (19.1 % vs. 14.0 %; P < 0.01). This resulted in Doppler mode having similar high values as B mode for Negative Predictive Value (99.9 vs. 99.6 %; P = 0.85) and Sensitivity (99.8 vs. 99.7 %; P = 0.86) but there were differences in Specificity (86 vs. 80.9 %; P < 0.01), Positive Predictive Value (88 vs. 84.3 %; P < 0.01), and Accuracy (93.0 vs. 90.4 %; P < 0.01). In conclusion, evaluation of CL blood perfusion by Doppler produced greater accuracy in the early identification of nonpregnant heifers and cows on D21 after TAI than measurement of CL diameter with B mode ultrasound; although both had over 90 % accuracy in identifying pregnant and nonpregnant females.

Optimizing ReBreed21 II: Fertility and reproductive efficiency in different parities during a shortened breeding season in beef cattle

This study evaluated the efficiency of a rapid reinsemination program allowing timed AI (TAI) every 21d (ReBreed21) in a commercial beef cow-calf operation. Nelore females from different parities (n = 2085) were synchronized for first TAI (D0 = TAI) using an estradiol/progesterone (E2/P4) protocol and assigned to one of three reinsemination programs: Resynch33 (n = 753), traditional resynch program with second TAI at D42 after first TAI; ReBreed21 (n = 687); or ReBreed21+EC (n = 670). The ReBreed females (n = 1357) received intravaginal P4 insert on D12, on D19 P4 was removed, and a dose of equine chorionic gonadotropin (eCG) was administered, then, ReBreed21 females received 0.6 mg of EC (ReBreed21+EC) or nothing (ReBreed21) and on D21, nonpregnancy (NP) was determined using Doppler ultrasound to detect corpus luteum (CL) blood flow (BF) (NP: <25 % BF pixels of total CL area) and NP cows received immediate TAI and GnRH to induce ovulation. Pregnancy diagnosis was performed at D33 after TAI following all TAIs. Cows considered pregnant at D21, based on CL BF, but NP on D33 were designated False-Positives (FP) and false negatives (FN) were number of nonpregnant cows/heifers on d21 based on the CL BF found to subsequently be pregnant on D33 divided by the total number pregnant. Pregnancy/AI (P/AI) did not differ for the first TAI (55.1 %) among the treatments. Heifers had similar P/AI at the second AI in all groups and similar to the first AI. Primiparous had greater P/AI in ReBreed21+EC and Resynch33 at s TAI compared to ReBreed21, 51.7 %, 55.8 %, 34.2 %, respectively. Multiparous had greater P/AI at second TAI in Resynch33 (60.9 %) than ReBreed21 programs (34.7 %). The percentage FP and FN among ReBreed21 programs did not differ, 13.8 and 0.2 %, respectively. Overall accumulative pregnancies on D21 of the breeding season were greater for ReBreed21 and ReBreed21+EC than Resynch33 (69.7 %, 71.6 %, and 55.5 %, respectively). However, on D42 of the breeding season, only heifers had greater pregnancies in ReBreed21 programs than Resynch33 (73.3 %, 74.3.6 %, and 63.2 %, respectively). Average days to pregnancy were less (P = 0.01) for ReBreed21 and ReBreed21+EC than Resynch33. Thus, the ReBreed21 strategy can improve the efficiency of TAI programs in beef cattle. Of interest, ReBreed21 was particularly effective in nulliparous, somewhat effective in primiparous when EC was added to the program, but relatively ineffective in multiparous beef cattle.

Optimizing ReBreed21 I: Evaluation of endocrine and ovarian dynamics in non-bred Bos indicus heifers

The present study evaluated follicular and endocrine dynamics during ReBreed21, a reproductive strategy that allows resynchronization of ovulation every 21 days in Bos indicus (Nelore) heifers. A synchronized estrous cycle was induced using a standard timed ovulation protocol (d -10: P4 implant inserted + 2 mg estradiol benzoate; d -2: P4 removed+ 0.5 mg cloprostenol + 0.6 mg estradiol cypionate + 200 IU equine chorionic gonadotropin (eCG); d0: 8.4 μg buserelin) without AI to ensure nonpregnancy in heifers. Day of GnRH was designated d0 of estrous cycle. On d12, heifers (n = 80) were randomized into three experimental groups: (1) ReBreed21 (n = 28) d12 P4 device inserted, d19 P4 device withdrawal plus 200 IU eCG, and d21 8.4 μg buserelin (GnRH); (2) ReBreed21+G (n = 26) same as ReBreed21 plus GnRH (16.8 μg) treatment on d12; and (3) Control (n = 26) no treatment. ReBreed21+G increased two-fold (62.9%; 18/26) percentage of heifers with synchronized follicular wave emergence compared to Control (34.6%; 9/26) whereas ReBreed21 (53.6%; 15/28) was intermediate. The ReBreeed21 groups (eCG on d19) increased (P < 0.01) follicular growth between d19 and d21 in ReBreed21 (2.3 ± 0.2 mm) and ReBreed21+G (3.4 ± 0.2 mm) compared with Control (1.2 ± 0.3 mm), resulting in greater (P < 0.01) follicle diameter on d21 for ReBreed21 (10.7 ± 0.4 mm) and ReBreed21+G (10.8 ± 0.4 mm) compared with Control (9.1 ± 0.5 mm). Structural luteolysis was similar among groups (P = 0.51), although the average day when P4 was <1 ng/mL was later (P < 0.01) for ReBreed21 (20.5 ± 0.2) and ReBreed21+G (20.7 ± 0.2) compared to Control (19.2 ± 0.4). Overall ovulation at the end of the estrous cycle was increased (P = 0.03) for ReBreed21 groups (83.3%; 45/54) compared with Control (57.7%; 15/26). Synchronized ovulation on day 22-23 was greater (P < 0.01) for ReBreed21 (78.6%; 22/28) and ReBreed21+G (76.9%; 20/26) compared with Control (30.8%; 8/26). Thus, the ReBreed21 resynchronization program produced acceptable endocrine and follicular dynamics, including synchronized ovulation at the end of the protocol in nonpregnant heifers providing good rationale for testing the fertility and practical implementation of this protocol under field conditions.

Efficacy of a modified Double-Ovsynch protocol for the enhancement of reproductive performance in Hanwoo cattle

OBJECTIVE

We aimed to evaluate the efficacy of a modified Double-Ovsynch protocol vs artificial insemination following estrus detection (AIED) for the enhancement of reproductive performance in Hanwoo cattle.

METHODS

Four hundred twelve Hanwoo cows were allocated to two treatment groups. The first group of cows were administered gonadotropin releasing hormone (GnRH) on Day 36 (±0.6), prostaglandin F2α (PGF2α) on Day 46 (8 to 12 days later), and GnRH on Day 49, which was followed by Ovsynch, consisting of an injection of GnRH on Day 56, PGF2α on Day 63, and GnRH 56 h and timed AI (TAI) 16 h later (modified Double-Ovsynch group, n = 203). The second group of cows underwent AIED (AIED group, n = 209) and were designated as controls.

RESULTS

The pregnancy per AI 60 days after the first AI was higher in the modified Double- Ovsynch (68.5%) than in the AIED (56.5%) group, resulting in a higher probability of pregnancy per AI (odds ratio: 1.68, p<0.05). Moreover, cows in the modified Double- Ovsynch group were more likely (hazard ratio: 1.28, p<0.05) to be pregnant by 150 days after calving than cows in the AIED group, and this difference was associated with a lower mean number of AIs per conception (1.27 vs 1.39, p<0.05) and a shorter median interval between calving and pregnancy (72 vs 78 days, p<0.1).

CONCLUSION

The modified Double-Ovsynch protocol, adjusted according to the herd visit schedule, can be readily used to increase the pregnancy per AI following the first AI and to shorten the interval between calving and pregnancy in beef herds.

An agent-based simulation model to compare different reproductive strategies in cow-calf operations: Technical performance

The objective of this study was to create a stochastic, agent-based simulation model of a synthetic population of beef cattle, and then use it to compare the technical performance of different reproductive strategies. The model was parameterized using data from a real beef cattle herd and from the peer-reviewed scientific literature to represent a Nelore cattle herd in the state of São Paulo, Brazil. Ten scenarios were evaluated: natural mating (NM) only (ONM); one timed artificial insemination (TAI) plus NM (1TAI + NM); two TAI plus NM, with 24, 32, and 40 days between inseminations (2TAI/24 + NM, 2TAI/32 + NM, and 2TAI/40 + NM, respectively); three TAI without NM, with 24, 32, and 40 days between TAI (3TAI/24, 3TAI/32, and 3TAI/40, respectively); and three TAI plus NM, with 24 and 32 days (3TAI/24 + NM and 3TAI/32 + NM, respectively). NM began 10 days after the last TAI and was performed until the end of the breeding season. The size of the female herd was set to contain up to 400 individuals. The bull population was established at 0, 7, or 15 bulls depending on the used scenario. Simulation was performed for 5000 days. The outcomes for each scenario are means ± S.E. assessed on 32 farms at 1-day time intervals and on an animal-by-animal basis after steady state was reached (1825 days). The 3TAI/24 + NM scenario resulted in a greater number of births (279.85 ± 0.47 births), while the ONM scenario had the least value (202.38 ± 0.43 births). The heaviest males and females at weaning belonged to 3TAI/24, with 190.85 ± 0.17 kg for males and 173.89 ± 0.13 kg for females. The ONM scenario had the lightest males (166.84 ± 0.18 kg) and females (151.75 ± 0.16 kg). The greatest and least total pregnancy rates were found in 3TAI/24 + NM (0.91 ± 0.00) and ONM (0.62 ± 0.00), respectively. The ONM scenario required 52.5 days more than scenarios that included TAI to reach 50% of pregnancy. The greatest ages at culling for cows was 3TAI/24 + NM (3658.88 ± 10.41 days). In contrast, the lowest age at culling was found in ONM (2823.93 ± 8.28 days). We concluded that the proposed model represents the main interactions of a real beef cattle herd. It has all the advantages of a physical experiment, but does not require incurring significant expenses nor altering the real system. This study offers evidence that the scenarios that present the best technical performance are those that used TAI with a 24-day interval between inseminations.

The Potential for New Donkey Farming Systems to Supply the Growing Demand for Hides

The demand for donkey hides for ejiao, a Traditional Chinese Medicine, has resulted in rapidly increasing prices for donkey hides and donkeys. This has put pressure on donkey populations globally and has implications for donkey welfare and the livelihoods of those who rely on donkeys as working animals. The aim of the research was to explore the feasibility of setting up new donkey farming systems to supply the rising demand for ejiao using a system dynamics model of donkey production. Results show that the size of the initial female breeding herd, reproductive performance, age of reproduction, percentage of female births and average breeding life of donkeys are key variables affecting the time to build up the donkey population to supply the demand for hides, which will be at least ten to fifteen years. The implications of this are: (i) prices for donkey hides will continue to increase, (ii) companies producing ejiao will use other ingredients, (iii) China will continue to source donkey hides from around the world, and (iv) there will be continued theft and illegal trade of donkeys and concerns for rural households reliant on donkeys for their livelihoods and adverse impacts on donkey welfare.

Dietary supplementation with an amino acid blend enhances intestinal function in piglets

The traditionally classified nutritionally non-essential amino acids are now known to be insufficiently synthesized for maximal growth and optimal health in piglets. This study determined the effects of dietary supplementation with an amino acid blend (AAB; glutamate:glutamine:glycine:arginine:N-acetylcysteine = 5:2:2:1:0.5) on piglet growth performance and intestinal functions. Sixteen piglets (24-day-old) were randomly assigned to a corn and soybean meal-based diet supplemented with 0.99% alanine (isonitrogenous control) or 1% AAB. On day 20 of the trial, blood and intestinal tissue samples were obtained from piglets. Compared with the control, AAB supplementation reduced (P < 0.05) diarrhoea incidence; plasma alanine aminotransferase and diamine oxidase activities; intestinal concentrations of hydrogen peroxide, malondialdehyde, and heat shock protein-70, and intestinal mRNA levels for interleukin-1β, interferon-γ, and chemokine (C-X-C motif) ligand-9; and the numbers of Enterobacterium family, Enterococcus genus and Clostridium coccoides in the colon digesta. Furthermore, AAB supplementation enhanced (P < 0.05): the plasma concentrations of serine, aspartate, glutamate, cysteine, tyrosine, phenylalanine, tryptophan, lysine, arginine, citrulline, ornithine, taurine, and γ-aminobutyric acid; intestinal villus height and surface area, villus height/crypt depth ratio, antioxidative enzyme activities, and mRNA levels for porcine β-defensin-1, sodium-independent amino acid transporters (b^0,+AT and y⁺LAT1), aquaporin (AQP) 3, AQP8, AQP10, nuclear factor erythroid 2-related factor 2 and glutathione S-transferase omega-2, and protein abundances of AQP3, AQP4, claudin-1, occludin and myxovirus resistance 1; and the numbers of Bifidobacterium genus and Lactobacillus genus in the colon digesta. Collectively, these comprehensive results indicate that dietary AAB supplementation plays an important role in improving piglet growth and intestinal function.

A deterministic, dynamic systems model of cow-calf production: The effects of breeding replacement heifers before mature cows over a 10-year horizon

Some cattle production experts believe that cow-calf producers should breed replacement heifers (nulliparous cows) before cows (primiparous and multiparous cows), sometimes referred to as providing a heifer lead time (tHL). Our objective was to model the effects different durations of tHL may have on measures of herd productivity, including the percent of the herd cycling before the end of the first 21 d of the breeding season (%C21), the percent of the herd pregnant at pregnancy diagnosis (%PPD), the distribution of pregnancy by 21-d breeding intervals, the kilograms of calf weaned per cow exposed (KPC), and the replacement percentage (%RH), using a deterministic, dynamic systems model of cow-calf production over a 10-yr horizon. We also wished to examine differences in the effect of tHL related to the primiparous duration of postpartum anestrus (dPPA). The study model examined 6 different dPPA for primiparous cows (60, 70, 80, 90, 100, or 110 d). The multiparous cow duration of postpartum anestrus was set to 60 d. The breeding season length for nulliparous cows was 63 d, as was the breeding season length for primiparous and multiparous cows. Nulliparous cows were modeled with a tHL of 0, 7, 14, 21, 28, 35, or 42 d. Results are reported for the final breeding season of the 10-yr horizon. Increasing tHL resulted in a greater %C21 for the herd and for primiparous cows. Length of tHL had minimal impact on the %PPD unless the dPPA was 80 d or greater. For a dPPA of 110 d, a 0 d tHL resulted in the herd having 88.1 %PPD. When tHL was 21 d, the %PPD increased to 93.0%. The KPC was 161.2 kg when the dPPA was 110 d and tHL was 0 d and improved to 183.2 kg when tHL was increased to 42 d. The %RH did not vary much unless the dPPA was 90 d or greater, but increasing tHL resulted in decreased %RH. Based on the model results, increasing tHL improves the production outcomes included in the analysis, but herds with dPPA of 90 d or greater had the greatest degree of improvement. For these herds, approximately two-thirds of the improvement in outcomes by increasing tHL from 0 d to 42 d was realized when tHL was 21 d. Costs are likely incurred when implementing tHL in a breeding management program, and an ideal tHL likely depends on the dPPA of the herd, the expected improvement in productivity, and the costs associated with increasing tHL. Determining the dPPA of a herd could help veterinarians and producers develop optimal herd management strategies.