Most Probable Producing Ability Research Articles

Most probable producing ability of ewes in relation to early growth traits

Data on 8586 lambs from 930 Rambouillet, 936 Targhee and 630 Columbia ewes were studied to determine the relationship of the ewe's own birth weight (BW), 60d weight (60W) and 120d weight (120W) with her subsequent most probable producing ability (MPPA) for these traits in lambs. Ewe/year of birth, age of ewe, lamb sex type of birth, rearing of lamb and regression on birth date affected BW, 60W and 120W ( P < 0.01). Year of birth of ewe, ewe breed and the interaction of ewe year of birth × ewe breed affected MPPA-BW, MPPA-60 and MPPA-120 ( P < 0.01). Effect of years of birth of ewe, breed of ewe and type of birth and rearing of the ewe, although statistically significant, were very small in magnitude. Residual correlations among growth traits and subsequent MPPA were small in magnitude but positive. Correlations between year of birth for BW with MPPA-BW, 60W with MPPA-60 and 120W with MPPA-120 were 0.47, −0.03, and −0.45, respectively. Similar correlations for age of the ewe's dam subclasses for early growth traits of ewe with the MPPA's were −0.76 between BW and MPPA-BW, −0.42 between 60W and MPPA-60 and −0.95 between 120W and MPPA-120. Correlations of the type of birth and rearing means for MPPA-BW with BW was −0.83, for 60W with MPPA-60 was −0.92 and for MPPA-120 with 120W was −0.99. Results of this study indicate that early growth traits are not a good predictor of subsequent ewe productivity as measured by MPPA for growth of lambs to weaning. Repeatability estimates for BW, 60W and 120W, respectively, were 0.29, 0.22 and 0.24 for Rambouillet, 0.30, 0.17 and 0.17 for Targhee and 0.36, and 0.19 and 0.18 for Columbia.

Pregnancy rate, calf mortality and calving date in unsupplemented hereford range cows

Pregnancy rate and calf mortality to weaning were characterized in a herd of registered Hereford cattle maintained under extensive range conditions with no supplemental feeding. Data consisted of 7771 records over a 19-year period (1957–1975). Large variation was noted in pregnancy rate among years (71.6–92.3%, P<0.01). Youngest (3-year-old) and oldest (10+ years) cows had the lowest pregnancy rates and did not differ ( P>0.05) from each other. Both year and age of dam significantly affected calf mortality. Average calf mortality was 5.9% in 3-year-old heifers (first calf), and differed ( P<0.05) from all other age of dam classes except 7 year olds. A subset of 1723 records was used to evaluate calving date as a measure of reproductive efficiency, with separate analyses for dry and lactating cows. Dry cows calved 11 days earlier in the subsequent calving season than lactating cows. Both linear and quadratic effects for age of cow were significant in lactating cows, while neither were significant among dry cows. Youngest and oldest age categories had later calving dates. The regression of current calving date on previous calving date was 0.312 ( P<0.01), while the regression of current calving date on calf birth weight of the previous calving was 0.352 ( P<0.01). The statistical model for lactating cows accounted for 29% of total variation. Heritability of calving date as a dam trait (lactating cows) was 0.09±0.07. Most probable producing ability (MPPA) was not a significant source of variation for calving date. Yearly variation in climate and forage production appear to be the major factors influencing performance in unsupplemented range herds.

Genetic parameters, maternal ability and related selection criteria for unsupplemented Hereford range cows.

Data on 5,130 unsupplemented Hereford range cattle were used to evaluate genetic and phenotypic parameters of growth to 2 yr of age under extensive range conditions. From those data, records on 769 heifers saved as replacements were used to evaluate the relationship between growth and subsequent productivity expressed as most probable producing ability (MPPA). Variation in weight largely was due to the year effect. Also, age of dam, the interaction between age of dam and year and the regression on day of birth significantly affected weaning weight. Heritabilities among males and females, respectively, were: birth weight, .53 +/- .09 and .52 +/- .09; weaning weight, .05 +/- .03 and .18 +/- .05; 12-mo gain, .24 +/- .10 and .10 +/- .04; 20-mo gain, .62 +/- .18 and .29 +/- .08; 24-mo gain, .45 +/- .16 and .17 +/- .07. The traits evaluated may have been a response to nutritional stress as well as gainability. The genetic correlation between gain from weaning to 12 mo (a period of weight loss) and gain from 12 to 20 mo (greatest weight gain) was -.93 +/- .45. Metabolic processes favoring growth in a good nutritional environment may result in greater weight loss in a stressful nutritional environment. The genetic correlation between a heifer's gain from weaning to 12 mo and her subsequent MPPA was .47 +/- 28, whereas the correlation between gain from 12 to 20 mo and subsequent MPPA was -.55 +/- .23.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of the beef recipient female on embryo transplant offspring

Embryo transfer techniques were employed to investigate the importance of prenatal and postnatal maternal breed effects on calves of high growth potential (Chianina) and low growth potential (Angus). Six crossbred cow breed groups of known producing ability were used as recipients. These crossbred recipient females had been produced by artificia ly inseminating Angus and Hereford cows with semen from Chianina, Maine Anjou and Simmental bulls. Prior production records on the recipients cipients were used to calculate Most Probable Producing Ability (MPPA) estimates for each cow for birth weight and weaning weight. Donor breed differences were evaluated (P<0.01 to P<0.001) for all growth traits with Chianina calves having longer gestation lengths, heavier weights at all ages and greater hip heights than Angus calves. Chianina calves also were found to be more aggressive than Angus calves as determined by their higher scores (P<0.001) when entering the working chute and while restrained in the squeeze chute. Differences among the six crossbred recipient dam groups were not significant for any growth trait. From linear contrasts it was noted that Angus crossbred dams produced heavier calves at birth (P<0.005) and weaning (P<0.10) than Hereford crosses. When recipient females were grouped into quartiles based on MPPA estimates, no differences were detected among MPPA groups for either birth weight or weaning weight of their embryo transfer calves. Information to date from the present study suggests that the bovine recipient female has less influence on the performance of embryo transfer calves than would be anticipated based on earlier breed comparison studies. Apparently, if recipient cows from breeds that are reasonably similar in milking ability and mature size are used in an embryo transfer program, the maternal environmental differences are not great enough to prevent the transplant calves from expressing their growth potential. Crossnursing may also occur, so that transplant offspring with higher growth potentials may obtain enough milk from other dams to allow them to express their genetic potential. The potential milk producing ability of the beef recipient should still remain as a primary consideration by those involved in the transplantation of bovine embryos.