Pregnancy Rates Per Artificial Insemination for Cows and Heifers Inseminated at a Synchronized Ovulation or Synchronized Estrus

Biological tenderness differences between longissimus muscles (LM) from Bos indicus and Bos taurus breeds were evaluated. Steers and heifers of Hereford x Angus (H x A, n = 10), 3/8 Sahiwal x H, A or H x A (3/8 SAH, n = 6) and 5/8 Sahiwal x H, A or H x A (5/8 SAH, n = 11) crosses were utilized. Muscle temperature and pH were monitored every 3 h for the first 12 h and at 24 h. Samples were obtained within 1 h and at 24 h postmortem from the LM for determination of calcium-dependent protease (CDP) -I and -II and CDP inhibitor (INH) activities. At 1 and 14 d postmortem, LM samples were removed for determining cathepsin B and B + L activity, soluble and total collagen, sarcomere length, muscle-fiber histochemistry, shear force and sensory-panel traits. Data were analyzed using least squares procedures with fixed effects of breed cross, sex and their interaction. No significant breed cross effects were observed for carcass traits or rates of pH and temperature decline. Steaks from H x A had lower (P less than .05) shear-force values and higher (P less than .05) sensory scores for tenderness at 1 and 14 d postmortem than steaks from 3/8 and 5/8 SAH. Correspondingly, 5/8 SAH had lower (P less than .05) myofibril fragmentation indices than H x A at 1, 3, 7 and 14 d postmortem. Breed cross effects were not significant for sarcomere length, fiber types, soluble and total collagen, cathepsin B and B + L specific activity, CDP-I and -II activity and INH activity within 1 h postmortem. However, INH total activity/100 g of muscle was greater (P less than .01) at 24 h postmortem for 5/8 SAH (208.8 +/- 14.8) and 3/8 SAH (195.6 +/- 19.3) than for H x A (136.3 +/- 14.9). For H x A, SDS-PAGE revealed that by d 1 desmin had been subjected to proteolysis, and by d 14 desmin could not be detected, but a 30,000-dalton component was clearly evident. However, in 5/8 SAH, desmin remained visible at d 14 without a 30,000-dalton component appearing. This reduced protein hydrolysis may account for less tender meat in SAH; INH apparently influences this process.

Evaluation of attributes that affect longissimus muscle tenderness in bos taurus and bos indicus cattle

Increasing food production for the growing human population off a constraining land base will require greater efficiency of production. Genetic improvement of feed efficiency in cattle, which is cumulative and permanent, is one likely vehicle to achieving efficiency gains. The objective of this review is to summarize genetic parameters for feed efficiency traits in dairy and beef cattle and also to address some of the misconceptions associated with feed efficiency in these sectors, as well as discuss the potential use of feed efficiency in breeding programs. A meta-analysis of up to 39 scientific publications in growing cattle clearly showed that genetic variation in feed efficiency exists with a pooled heritability for residual feed intake (RFI) and feed conversion efficiency of 0.33 ± 0.01 (range of 0.07 to 0.62) and 0.23 ± 0.01 (range of 0.06 to 0.46), respectively. Heritability estimates for feed efficiency in cows were lower; a meta-analysis of up to 11 estimates revealed heritability estimates for gross feed efficiency and RFI of 0.06 ± 0.010 and 0.04 ± 0.008, respectively. Meta-analysis of genetic correlations between feed intake, feed efficiency and other performance traits are presented, and selection index theory is used to calculate the proportion of genetic variation in feed intake that can be explained by easy to measure, and often already collected, data. A large proportion of the genetic variation in feed intake could be explained in both growing animals and lactating animals using up to 5 predictor traits, including BW, growth rate, milk yield, body composition, and linear type traits reflecting body size and muscularity. Knowledge of genetic merit for feed intake can be used, along with estimates of genetic merit for energy sinks, to calculate genetic merit for feed efficiency. Therefore, the marginal benefit of collecting actual feed intake data, using the genetic parameters used in this study, appears to be low. There is now sufficient information available to develop a road map on how best to direct research to ensure long-term food security for a growing human population. Gaps in knowledge are identified here, and possibilities to address these gaps are discussed.

Cell Biology Symposium: genetics of feed efficiency in dairy and beef cattle.

Invited review: Treatment of cows with an extended postpartum anestrous interval.

The pregnancy-associated glycoproteins (PAG) constitute a large family of recently duplicated genes. They show structural resemblance to pepsin and related aspartic proteinases. A total of 21 bovine (bo) PAG and 9 ovine (ov) PAG cDNA have been identified. Phylogenetic analysis indicated that the PAG are divided into two main groupings that accurately reflect their tissue expression, as determined by in situ hybridization. In the first pattern, represented by ovPAG-2 and boPAG-2, -8, -10, and -11 (where the numbering is arbitrary and reflects order of discovery within species), expression occurred throughout the outer epithelial layer of the placenta (trophectoderm). The second pattern was predominant localization to binucleate cells. Ribonuclease protection assays, which allow discrimination between closely related transcripts, have shown that the expression of PAG varies in a temporal manner over pregnancy. Of those bovine PAG expressed predominantly in binucleate cells, boPAG-1, -6, and -7 are expressed weakly, if at all, by Day 25 placenta, but are present at the middle and end of pregnancy. Others, such as boPAG-4, -5, and -9, are expressed at Day 25 and at earlier stages. Although not among the earliest PAG produced by the trophoblast, boPAG-1 has been used for pregnancy diagnosis, particularly in dairy cows, where there is a major need for a sensitive method capable of detecting pregnancy within 1 mo of conception. It seems likely that some of the newly discovered PAG will be better candidates than PAG-1 for pregnancy diagnosis.

https://bioone.org/journals/biology-of-reproduction/volume-62/issue-6/biolreprod62.6.1624/Pregnancy-Associated-Bovine-and-Ovine-Glycoproteins-Exhibit-Spatially-and-Temporally/10.1095/biolreprod62.6.1624.pdf

Pregnancy-associated bovine and ovine glycoproteins exhibit spatially and temporally distinct expression patterns during pregnancy.

Reducing the incidence of short estrous cycles in beef cows with norgestomet

Effect of stage of the estrous cycle on interval to estrus after PGF2α in beef cattle

/pdf/effects-of-milk-and-forage-intake-on-calf-performance-4lbxa4btoi.pdf

Effects of milk and forage intake on calf performance.

To determine whether the uterus was the source of serum pregnancy-specific protein B (PSPB) after calving, five beef cows were hysterectomized at 21 d postpartum and five served as intact controls. A single blood sample was taken from all cows immediately after calving and then twice weekly until 21 d postpartum. Beginning on d 22, blood samples were taken from all cows at 3-h intervals for 4 d and then twice weekly until 53 d postpartum. When the half-life calculated for the interval from d 1 to 21 was used as a covariate, the adjusted d-22 to -53 half-lives were 8.4 d for control cows vs 7.3 d for hysterectomized cows (P = .044). Data show that PSPB has a long half-life in the circulation and that the uterus is a minimal, if any, source of postpartum circulating PSPB. In another experiment, PSPB was measured weekly after calving in serum of 58 Polled Hereford and Simmental cows. Cows were exposed to fertile bulls and allowed to mate at every estrus. Observations were made for estrus, and progesterone concentrations in serum were measured to estimate the time of ovulations. Levels of PSPB were highest at approximately the time of calving, then decreased rapidly. Concentrations of PSPB were < 1 ng/mL by 80 d in eight cows that had not conceived since calving. Two cows eventually had nondetectable PSPB levels, one by 86 d and the other by 96 d after calving.(ABSTRACT TRUNCATED AT 250 WORDS)

Pregnancy-specific protein B in serum of postpartum beef cows.

Milk EPD, used to predict the milk production potential of a parent's daughters, have been reported by all major cattle breed associations. Our objectives were to determine the relationship of milk EPD of a dam to actual milk production (both fluid and components) and offspring weaning weight. Angus (AN; n = 114) and Simmental (SM; n = 82) cows were machine-milked at approximately 60, 104, and 196 d postpartum after overnight calf removal. In addition, one herd of AN was also milked at approximately 35 and 145 d postpartum. A lactation curve was fitted to these measurements to estimate total milk production during lactation. Simple correlations between 205-d total milk yields (TMY) and adjusted 205-d calf weaning weight (WW) were .30 (P < .001) and .47 (P < .001) for AN and SM, respectively. Furthermore, milk EPD was positively correlated to adjusted WW (r = .38 P < .001; r = .39, P < .001) and TMY (r = .32, P < .001; r = .44, P < .001) for AN and SM cows, respectively. A 1-kg change in TMY changed WW by .014 +/- .006 kg (P < .001) in AN and by .032 +/- .009 kg (P < .001) in SM. A 1-kg change in milk EPD resulted in a 4.85 +/- 1.14 kg change in WW (P < .001) in AN and a 3.74 +/- 1.73 kg (P < .05) change in SM. Corresponding changes in TMY were 42.1 +/- 16.6 kg (P < .01) and 69.3 +/- 16.0 kg (P < .001) for AN and SM, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

R.R. Schalles

Papers

Reducing the incidence of short estrous cycles in beef cows with norgestomet

Effect of stage of the estrous cycle on interval to estrus after PGF2α in beef cattle

Effects of milk and forage intake on calf performance.

Pregnancy-specific protein B in serum of postpartum beef cows.

Relationship of milk production, milk expected progeny difference, and calf weaning weight in angus and simmental cow-calf pairs.