Pregnancy rates in lactating dairy cows subjected to protocols for timed insemination using different progesterone intravaginal devices and doses of prostaglandin

SCANDOLO LUCINI, DIEGO GERMÁN; BILBAO, MARÍA GUILLERMINA; MASSARA, NESTOR; MORÁN, KAREN DAIANA; FARCEY, MARÍA FLORENCIA; ZAPATA, LUIS OSCAR; PESOA, JESÚS; TURIC, ESTEBAN; BARTOLOMÉ, JULIÁN ALBERTO

Santa Rosa, La Pampa

Congreso; XXXVIII Congreso de la Asociación Argentina de Producción Animal; 2015

Asociación Argentina de Producción Animal

IntroductionFertility of lactating dairy cows has been reduced due to intensification of production systems and increase in milk production. These changes resulted in reduction of estrus expression, estrus detection and pregnancy per AI (Santos, 2010). High milk production increase metabolic rate and reduce circulating concentration of estrogen and progesterone (Sangsritavong et al., 2002). Therefore, the incidence of anestrus, anovulation and embryo mortality is increased. The addition of progesterone in synchronization protocols improve follicular development and enhance fertility in cows without a corpus luteum (Bisinotto et al., 2015). In addition, size of the cows and metabolic rates suggest the possibilities of reduced luteolytic effect of commercial compounds. The hypothesis was that a 3 g intravaginal progesterone device will benefit noncyclic cows and a double dose of prostaglandin will also increase fertility is synchronized lactating dairy cows. The objective was to compare pregnancy per AI in lactating dairy cows synchronized using progesterone intravaginal devices with different amounts of progesterone and single or double dose of prostaglandin.Materials and methodsThe study was conducted in a large dairy farm with 1350 milking cows in a dry lot system located in the Northwest of Buenos Aires province. Cows with more than 60 days in milk were randomly assigned to four experimental groups in a 2x2 experimental design. On Day 0, cows (n=337) received 10 µg of busereline diacetate (2.5 mL, i.m., Gonaxal, Biogenesis Bago, Argentina) and either a 1 g or 3 g intravaginal progesterone device (Elastec SRL, Argentina). On Day 7, the progesterone intravaginal device was removed and cows randomly assigned to receive either a single dose of 0.300 mg D-cloprostenol (4 mL, i.m., Enzaprost®, Biogénesis Bagó) or two doses 24 h apart of 0.150 mg (2 mL, i.m., Enzaprost). Estrus detection and IA at estrus was conducted for 72 h and cows not in estrus were timed inseminated (TAI) and treated with 10 µg of busereline diacetate (2.5 mL, i.m., Gonaxal) at 72 h after device removal (Day 10). On Day 0, lactation, days in milk, milk production, body condition score and stage of the estrous cycle was recorded. At insemination, sire, technician and type of insemination (estrus or TAI) was also recorded.Baseline comparisons between treatment groups for lactation, body condition score, stage of the estrous cycle, sire, technician and type of insemination were stablished using contingency tables and chi-squared statistic and for days in milk and milk production using ANOVA. The effect of group on pregnancy per AI adjusted for different variables and interactions was analyzed using the backward elimination procedure in Proc Genmod of the SAS System. Significant effects were declared at P < 0.05 and tendencies declared at P ≤ 0.10. Results and discussionPregnancy per AI for cows receiving a 1 g intravaginal progesterone device was 25.3 % (41/162) and for cows receiving a 3 g intravaginal device was 30.3 % (53/175) (P = 0.32). Pregnancy per AI for cows receiving a single dose of 0.300 mg of cloprostenol was 25.3 % (42/166) and for cows treated with two doses of 0.150 mg of cloprostenol 24 h apart was 30.4 % (52/171)(P = 0.31). Pregnancy per AI in normal cyclic cows was 29.2 and 31.2 for cows receiving a 1 g and 3 g intravaginal progesterone device, respectively (Non-significant).However, in anestrus cows, pregnancy per AI was 11.1 and 29.7 % and in cows with normal ciclicity was 30.7 and 30.4 % for cows receiving a 1 g and 3 g intravaginal progesterone device, respectively (Non-significant).Despite of the fact that results were as expected, there were not statistical differences for main effects, probably due to the sample size, therefore further studies are necessary.Conclusion An intravaginal device containing 3 g of progesterone in noncyclic cows and a double dose of prostaglandin 24 h apart seems to increase fertility in lactating dairy cows subjected to an Ovsynch/TAI protocol, however, a larger sample size is necessary to confirm these results.