Realized Versus Expected Gains in Milk and Fat Production of Holstein Cattle, Considering the Effects of Days Open

Abstract

The objective of this study was to determine whether differences in first lactation production, unadjusted or adjusted for days open, were correctly predicted by pedigree estimates for two lines of Holstein cattle. Data on 875 cows from two selection lines were collected from 1970 to 1988. Lines were created by mating foundation females of high or low pedigree merit to sires selected for high or average PTA milk. Both lines were managed identically to minimize environmental differences. The number of days open was analyzed with a fixed effects model containing year, season, interaction of year and season, sire line, foundation group, and interaction of sire line and foundation groups. The high milk line had significantly more days open than did the average line. Adjusted and unadjusted records for milk and fat were analyzed with the model described previously, plus the interaction of sire line and year. Least squares means and estimates for mean parent average were used to calculate realized and expected differences in production between lines within and across years. Adjustment of records for days open reduced estimates of realized gain, but not significantly. Regressions of realized gain on expected gain indicated that expected gains were matched or exceeded by unadjusted or adjusted realized gain.

A Comparison of Different Methods of Estimating Sire Transmitting Ability of Some Milk Traits in a Herd of Holstein Friesian

“…Significant (p<0.01) effects of month and year of caving on each of the traits studied were found. These results are agreement with the findings reported on Friesian raised in other countries by Milagres et al (1989), Rege (1991), Kaya (1996), Makuza and McDaniel (1996) and Kelm et al (1997). Differences in milk yield and lactation period attributed to month and year of calving were interpreted to be due to climatic, nutritional and managerial conditions which changed from one year or month of calving to another.…”

Seasonal Age Correction Factors for 305 Day Milk Yield in Holstein Cattle

“…Least squares mean of 305 day milk yield was 4738 ± 76 kg ( Table 1). The present mean was lower than those reported by Kaya (1996); Makuza and McDaniel (1996), Kelm et al (1997) and Yener et al (1998) working on Holstein Friesian cattle in different countries and ranged from 5040 to 8383 kg while, the present mean was higher than those estimated reported by Khattab and Sultan (1991) and Abdel Glil (1996), being (2954 kg and 2254 kg, respectively). The differences between our results and those of other workers could be due to differences in climatic and management conditions and/or genetic differences in herds.…”

“…These findings are in close agreement with those of Ashmawy (1991), Khattab and Sultan (1991) and Yener et al (1998). Also, Kaya (1996), Makuza and McDaniel (1996) and Kelm et al (1997) found significant effect of month of calving on milk yield, all working on Holstein Friesian. However, Eltawil et al (1976) observed a consistent trend in season of calving effect on milk yield although not attaining statistical significance in most cases.…”

“…Effects of year of calving on 305 day milk yield (Table 2) were highly significant (p<0.01) for each season of calving and for all data, but no specific trend was noticed the significant effect of year of calving on 305 day milk yield (Table 1). Mourad et al (1986), Ashmawy (1988, 1990), Khattab and Sultan (1991), Ashmawy (1991), Kaya (1996), Makuza and McDaniel (1996), Kelm et al (1997) and Yener et al (1998) with different herds of dairy cattle reported significant effect of year of calving on 305 day milk yield. They indicated that differences in this respect may be due to differences between years in feeding system and managerial practices.…”

A comparison of different methods of estimating sire transmitting ability of some milk traits in a herd of Holstein Friesian cattle

“…These results are agree with the findings were also reported on Friesian raised in other countries by MILAGRES et al (1989). REGE (1991), KAYA (1996), MAKUZA and McDANIEL (1996) and KELM et al (1997). Differences in milk yield and lactation period attributed to month and year of calving were interpreted to be due to climatic, nutritional and managerial conditions which changed from one year or month of calving to another.…”