A daily herd Markov-chain model to study the reproductive and economic impact of reproductive programs combining timed artificial insemination and estrus detection

Abstract

Our objective was to compare the economic and reproductive performance of programs combining timed artificial insemination (TAI) and different levels of AI after estrus detection (ED) using a daily Markov-chain model. A dairy herd was modeled with every cow following daily probabilistic events of aging, replacement, mortality, pregnancy, pregnancy loss, and calving. The probability of pregnancy depended on the combination of probability of insemination and conception rate (CR). All nonpregnant cows had a probability of pregnancy between the end of the voluntary waiting period and days in milk cutoff for AI. After the cutoff, cows were labeled as do not breed and replaced when milk production was below a minimum milk threshold. A similar model was created to represent a replacement heifer herd to simulate and adjust the supply and demand of replacements. The net value (NV) of a program was the sum of milk income over feed cost, replacement and mortality cost, income from newborns, and reproductive costs. The model was used to compare the NV of 19 programs. One program used 100% TAI (42% CR for first TAI and 30% for second-and-later services), whereas the other programs combined TAI with ED. The proportion of cows receiving AI after ED for the combined programs ranged from 30 to 80%, with levels of CR of 25, 30, and 35%. As the proportion of cows receiving AI after ED increased, the CR of cows receiving TAI decreased. The combined programs with CR of 35% for cows receiving AI after ED had the greatest NV and reproductive performance at all levels of ED. The program using 100% TAI had greater NV and better reproductive performance than all programs with 25% CR after ED inseminations, whereas it had very similar performance to combined programs with up to 60% of cows receiving AI after ED and 30% CR. The factor with the greatest relative contribution to the differences among programs was income over feed cost, followed by replacement and reproductive costs. Adjusting the days in milk cutoff for AI to match the supply and demand of heifer replacements improved the NV of all programs except for those with 25% CR after ED, which had either no change or a decrease in NV. In summary, the economic value of reproductive management programs combining TAI and ED depended on the proportion of cows receiving AI after ED and the resulting CR. Adjusting the heifer supply and demand increased the NV of programs with heifer surplus and decreased the NV of programs with heifer deficit.

Economics of fertility in high-yielding dairy cows on confined TMR systems

“…These factors seem to be the most important determinants of economic reproductive efficiency (Giordano et al, 2012;Galvao et al, 2013). However, the overall value of improving reproductive efficiency is a combination of all economic factors interacting with no single factor being defined as the most important in all situations.…”

“…Milk productivity, milk sales and milk income over feed cost As milk productivity increases, feed costs also increase and although some studies found that the milk income over feed cost increased with reproductive performance (Giordano et al, 2012;Kalantari and Cabrera, 2012), other studies reported that the milk income over feed cost could, at times, decrease slightly as reproductive performance increases (Cabrera, 2012;Galvao et al, 2013). The relationship between milk production and feed consumption is complex and interacts with many factors such as the herd structure, feeds prices and the shape and persistence of lactation curves.…”

“…Herd net return on high yielding confined total mixed ration (TMR) systems is strongly associated with reproductive performance (Giordano et al, 2012;Galvao et al, 2013). Efficient reproductive programme regulate herd population dynamics and herd structure allowing cows to take advantage of the most efficient part of the lactation curve (Ferguson and Galligan, 1999), while maximising production of on-farm replacements (Giordano et al, 2012), minimising costs associated with replacements and mortality (Giordano et al, 2011 and2012;Galvao et al, 2013), and minimising the relative costs associated with reproduction (Giordano et al, 2012).…”

“…Efficient reproductive programme regulate herd population dynamics and herd structure allowing cows to take advantage of the most efficient part of the lactation curve (Ferguson and Galligan, 1999), while maximising production of on-farm replacements (Giordano et al, 2012), minimising costs associated with replacements and mortality (Giordano et al, 2011 and2012;Galvao et al, 2013), and minimising the relative costs associated with reproduction (Giordano et al, 2012). Most of high-yielding dairy farms in the United States use a combination of synchronisation/ovulation control protocols and oestrous detection (OD) for their reproductive management (Caraviello et al, 2006;Giordano et al, 2012;Galvao et al, 2013). Although there are a number of metrics for reproductive performance (e.g.…”

“…However, it is difficult for them to assess the overall economic impacts of reproductive programme. A series of simulation studies in recent years (Giordano et al, 2011(Giordano et al, , 2012(Giordano et al, and 2013Galvao et al, 2013) attempt to provide responses to these difficult questions and are the main subject of this review paper. Some of these studies also provide decision support tools that could be customised for herd-specific economic assessments related to reproduction.…”