Hutchinson I A, Shalloo L, Butler S T
Teagasc, Animal & Grassland Research and Innovation Centre, Moorepark, Fermoy, Co. Cork, Ireland.
J Dairy Sci. 2013 Oct;96(10):6742-52. doi: 10.3168/jds.2012-6476. Epub 2013 Aug 16.
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.
建立了一个模型，以研究在季节性奶牛生产系统中，对初产小母牛和泌乳母牛使用性别分选精液对后备小母牛数量和牛群扩张速度的影响。根据所使用精液的类型建立了五个独立的牛群：常规冻融精液（Conv）、在繁殖季节的前3周对泌乳母牛使用的性别分选新鲜精液（SFre1）、在繁殖季节的前3周对泌乳母牛使用的性别分选冻融精液（SFro1）、在繁殖季节的前6周对泌乳母牛使用的性别分选新鲜精液（SFre2），或在繁殖季节的前6周对泌乳母牛使用的性别分选冻融精液（SFro2）。在SFro1、SFre1、SFro2和SFre2牛群中，对初产小母牛进行第一次和第二次人工授精时使用性别分选精液。假设性别分选新鲜精液和性别分选冻融精液的受胎率分别为常规冻融精液受胎率的94%和75%。初始牛群规模为100头奶牛，在15年模拟的前2年保持不变，之后保留所有可用的后备小母牛以促进牛群扩张。针对5个牛群中的每一个，研究了两种不同的土地可利用情况：可利用土地允许牛群规模最大扩张到150头奶牛（S1），或可利用土地允许牛群规模最大扩张到300头奶牛（S2）。一旦达到最大牛群规模，停止使用性别分选精液，并在小母牛犊1月龄时出售所有多余的小母牛犊。与扩张相关的所有资本支出均通过15年期贷款融资。从年度农场利润、年度现金流和总贴现净利润方面对10种不同方案进行了评估。与冻融性别分选精液和常规冻融精液相比，使用新鲜性别分选精液产生了更多的后备小母牛，从而使牛群扩张更快。对于SFre1、SFro1、SFre2、SFro2和Conv牛群，在S1情况下，分别在第5年、第5年、第4年、第5年和第7年达到最大牛群规模。在S2情况下，对于SFre1、SFro1、SFre2、SFro2和Conv牛群，分别在第8年、第10年、第7年、第9年和第14年达到最大牛群规模。在S1情况下，与SFre1、SFro1、Conv和SFro2牛群相比，SFre2牛群的总贴现净利润分别高出4130欧元、38869欧元、47231欧元和52089欧元。在S2情况下，与SFre1、SFro1、SFro2和Conv牛群相比，SFre2牛群的贴现净利润分别高出44204欧元、255524欧元、280373欧元和325815欧元。性别分选冻融精液对牛群繁殖力的负面影响降低了农场盈利能力，并将阻碍其在泌乳母牛中的广泛应用。
