Expanding the dairy herd in pasture-based systems: The role of sexed semen use in virgin heifers and lactating cows

Abstract

A model was developed to examine the effects of sexed semen use in virgin heifers and lactating cows on replacement heifer numbers and rate of herd expansion in a seasonal dairy production system. Five separate herds were established according to the type of semen used: conventional frozen-thawed (Conv), sexed fresh semen used in lactating cows for the first 3 wk of the breeding season (SFre1), sexed frozen-thawed semen used in lactating cows for the first 3 wk of the breeding season (SFro1), sexed fresh semen used in lactating cows for the first 6 wk of the breeding season (SFre2), or sexed frozen-thawed semen used in lactating cows for the first 6 wk of the breeding season (SFro2). In the SFro1, SFre1, SFro2, and SFre2 herds, sexed semen was used for the first and second artificial insemination in virgin heifers. Pregnancy rates achieved with sexed fresh and sexed frozen-thawed semen were assumed to be 94 and 75% of those achieved with conventional frozen-thawed semen, respectively. Initial herd size was 100 cows, which was maintained for the first 2 yr of the 15-yr simulation, after which all available replacement heifers were retained to facilitate herd expansion. Two different scenarios of land availability were examined for each of the 5 herds: land available allowed expansion to a maximum herd size of 150 cows (S1), or land available allowed expansion to a maximum herd size of 300 cows (S2). Once maximum herd size was reached, sexed semen use was discontinued and all excess heifer calves were sold at 1 mo old. All capital expenditure associated with expansion was financed with a 15-yr loan. Each of the 10 different options was evaluated in terms of annual farm profit, annual cash flow, and total discounted net profit. The use of fresh sexed semen generated more replacement heifers, leading to faster herd expansion compared with frozen-thawed sexed semen and conventional frozen-thawed semen. Maximum herd size under S1 was reached in yr 5, 5, 4, 5, and 7 for the SFre1, SFro1, SFre2, SFro2, and Conv herds, respectively. Under S2, maximum herd size was reached in yr 8, 10, 7, 9, and 14 for the SFre1, SFro1, SFre2, SFro2, and Conv herds, respectively. Total discounted net profit under S1 for the SFre2 herd was €4,130, €38,869, €47,231, and €52,089 greater compared with the SFre1, SFro1, Conv, and SFro2 herds, respectively. Under S2, discounted net profit for the SFre2 herd was €44,204, €255,524, €280,373, and €325,815 greater compared with the SFre1, SFro1, SFro2, and Conv herds, respectively. The negative effects of the sexed frozen-thawed semen on herd fertility reduced farm profitability and will prevent its widespread use in lactating cows.

Applications and cost benefits of sexed semen in pasture-based dairy production systems

“…The impending abolition of EU milk quotas, coupled with an ambitious target set by the Irish government in the Food Harvest 2020 report for a 50% increase in national milk output by 2020 (DAFM, 2010) presents a real opportunity for Irish dairy farmers to increase herd size and milk output. Bio-economic modelling was used to investigate the effects of using sexed semen on either virgin heifers only (Hutchinson et al, 2013a) or on both virgin heifers and lactating cows on herd expansion (Hutchinson et al, 2013b).…”

“…Based on the 2013 field data on the fertility performance of fresh and frozen sexed semen, some modifications to both the fertility assumptions and the scenarios used in the models (Hutchinson et al, 2013a and2013b) are required.…”

“…Updated simulation models with preliminary field study data In order to provide the most relevant and current information in this review, we have re-run the simulation models developed in the previous studies (Hutchinson et al, 2013a and2013b) using the preliminary results from a sexed semen field trial that was conducted in Ireland in spring 2013. Full details on the methodology involved in the development of the model and assumptions have been previously described (Hutchinson et al, 2013a and2013b).…”

Development and evaluation of the herd dynamic milk model with focus on the individual cow component

“…with parity = −0.1 for primiparous and +0.1 for multiparous, BCS calv the BCS of the cow at calving and the theoMOBmax expressed in units of BCS and coeff_parity = 0.75 for party 1, 0.92 for parity 2 and 1 otherwise (Hutchinson et al, 2013). …”

“…This potential was determined by evaluating the performance of the average actual cows through the 3 years. The average MY of the cattle was adjusted to parity 3 equivalents by assuming that parity 1 and parity 2 yield were 75% and 92% of parity 3 yields (Hutchinson et al, 2013). As the SRs were balanced for MY, the same theoMYmax yield has been applied across SR. Then the level of feeding effect has been included in the calculations as low (SR2) and very low (SR1) leading to a correction of the potential of 1.25 and 1.40, respectively, compared with the actual milk deliveries.…”