Reproductive status of Kansas dairy herds

There has been no appreciable change in the reproduction status of Kansas dairy herds over the last 25 yr. For example, the average calving interval was 398 days in 1965 and 405 days in 1988. Analysis of other measures show similar results. Although the long-stated management goal for a dairy herd has been a calf-a-year or 365-day calving interval, few herds realize this efficiency. On the positive side, the stability of reproductive performance is noteworthy, since genetic antagonism exists between production and reproduction. From 1965 to 1988, average yearly milk production in production-tested herds (DHI) has increased 41%.; Dairy Day, 1989, Kansas State University, Manhattan, KS, 1989; The 1989 Annual KSU Dairy Day is known as Dairy Day, 1989


Introduction
There has been no appreciable change in the reproduction status of Kansas dairy herds over the last 25 yr.For example, the average calving interval was 398 days in 1965 and 405 days in 1988.Analysis of other measures show similar results.Although the long-stated management goal for a dairy herd has been a calf-a-year or 365-day calving interval, few herds realize this efficiency.On the positive side, the stability of reproductive performance is noteworthy, since genetic antagonism exists between production and reproduction.From 1965 to 1988, average yearly milk production in production-tested herds (DHI) has increased 41%.

Measures of Reproductive Efficiency
Several measurements may be considered when evaluating reproductive performance, namely, No one measure is all conclusive.For example, average calving interval may be ideal, but if a significant part of the herd has not been bred and averages more than 70 days open, serious economic consequences result.
The KSU Dairy Herd Analyzer (KSU-DHA) provides an economic evaluation of four areas of herd management, as noted in Table 1.Any comparative analysis requires assumptions and/or goals.In the KSU-DHA, the stated goals (and economic consequences) are defined as follows: 1.
Days dry 45-60 days < 45 or > 60 d -$3 loss per day The value of the KSU-DHA is not the specific economic loss at any point in time but the comparison over time to evaluate management changes.For example, if a preventive herd health program (PHHP) were initiated, then the KSU-DHA would be an excellent way to evaluate the program after a year.Reproduction is the most difficult management area to evaluate in the dairy business and the easiest to overlook.Open cows (not pregnant but should be) are not sick or debilitated.
Reproductive losses are insidious.

Production vs Reproduction
Genetic antagonism exists between production and reproduction.Simply stated, higher producing cows are more difficult to settle.This relationship between production and reproduction is confounded by a management tendency to delay breeding back the higher producers, which also tend to be more difficult to detect in heat.The physiological basis for lowered efficiency in higher producing cows is difficult to determine.
Table 2 examines some reproductive measurements in herds at various levels of yearly production.The negative effect of production on reproduction is not apparent from the data under farm conditions.Apparently, managers of higher producing herds "over manage" the antagonism by getting more cows bred earlier in lactation.This fact is especially evident when comparing cows open, not-yetbred, and the percent of cows open more than 120 days in Table 2.Although conception to first breeding is higher at lower production levels, there is little difference in percent of cows pregnant among herds after two breedings.

Identifying Reproductive Problems
Every open cow is a potential problem, because only 90% will conceive and deliver a calf under the management goals set by most producers.The basic problem in most herds is one of infertility-not sterility.The most common mistake in most herds is the failure to get cows bred back soon after calving.As noted in Table 2, the average number of days to first breeding is 82.Since conception to service is 50% and about one-half of heat periods are missed, the calving interval is dictated to be 400+ days.
Studies confirm that the fundamental difference between herds with high and low reproductive efficiency is awareness-awareness that cows need to be serviced before they can possibly become pregnant.Adequate records are necessary to identify those cows not bred-but should be.Such records also should identify those cows serviced that are open at pregnancy exam.These two conditions contribute the majority of reproductive losses in Kansas dairy herds.The proper use of synchronizing agents (prostaglandins) can contribute markedly in reducing reproductive losses.

Tools are Available
Adequate record systems are available to "keep on top" of reproductive problems in dairy herds and minimize losses.The basic Dairy Herd Improvement (DHI) provides both a cow and herd evaluation on a monthly basis.The Flexible Management Report (FMR) will provide even more detailed information.Herds enrolled in the Electronic Barn Sheet option (EBS) can further fine tune reproductive management.As with any record system-simple or complex-there is little value to be gained unless it is used.