Insemination of four cows per dose of frozen semen with a fixed-time artificial insemination protocol

The aim of the study was to evaluate the practicality of a 1: 4 dilution of doses of semen in fixed - time artificial insemination ( FTAI ) programs. Nelore cows (n = 803 ) were synchronized by a conventional FTAI protocol. For AI in the dilut ed group (n = 392) , 0.5 ml semen straws were thawed and 0.5 ml of extender conta ining amino acids and methylxanthine derivatives was added. The straws were fractionated into four straws of 0.25 ml each (dilution 1:4) with approximately 2.5 x 10 6 spermatozoa each and the insemination was performed in the ipsilateral horn to the ovary c ontaining the dominant follicle . In the control group (n = 411), AI was performed in the uterine body with one straw of 0.5 ml (10 x 10 6 spermatozoa) containing seme n from the same bull and batch . The conception rate was 49.2% (193/392) for the diluted gro up and 50.1% (206/411) for the control group, with 1.97 and 0.50 pregnancies per dose of semen , respectively . T he dilution of semen provide d a pregnancy index similar to the control group ; however, the technique increased the number of pregnancies per dos e , allowing for the best use of semen of high genetic value and reducing the cost per pregnancy.

Ovarian follicle reserve: emerging concepts and applications

This paper presents new concepts in the study of folliculogenesis and describes some of the current applications to reproductive biotechnology. The importance of better understanding this issue is addressed both for basic and applied research. After a brief review of the basic conceptions of the origin, formation, and growth of follicules according to stablished concepts, some controversial points, as the postnatal production of the follicles and the role of multioocyte follicles, are discussed. The importance of the ovarian follicular reserve is considered for fertility and reproductive parameters, as well as some questiones about the presence of multioocyte follicles in adult ovaries. Finally, some future prospects are proposed.

Insemination of four cows per dose of frozen semen with a fixed-time artificial insemination protocol

The aim of the study was to evaluate the practicality of a 1: 4 dilution of doses of semen in fixed - time artificial insemination ( FTAI ) programs. Nelore cows (n = 803 ) were synchronized by a conventional FTAI protocol. For AI in the dilut ed group (n = 392) , 0.5 ml semen straws were thawed and 0.5 ml of extender conta ining amino acids and methylxanthine derivatives was added. The straws were fractionated into four straws of 0.25 ml each (dilution 1:4) with approximately 2.5 x 10 6 spermatozoa each and the insemination was performed in the ipsilateral horn to the ovary c ontaining the dominant follicle . In the control group (n = 411), AI was performed in the uterine body with one straw of 0.5 ml (10 x 10 6 spermatozoa) containing seme n from the same bull and batch . The conception rate was 49.2% (193/392) for the diluted gro up and 50.1% (206/411) for the control group, with 1.97 and 0.50 pregnancies per dose of semen , respectively . T he dilution of semen provide d a pregnancy index similar to the control group ; however, the technique increased the number of pregnancies per dos e , allowing for the best use of semen of high genetic value and reducing the cost per pregnancy.(AU)

Ovarian follicle reserve: emerging concepts and applications

This paper presents new concepts in the study of folliculogenesis and describes some of the current applications to reproductive biotechnology. The importance of better understanding this issue is addressed both for basic and applied research. After a brief review of the basic conceptions of the origin, formation, and growth of follicules according to stablished concepts, some controversial points, as the postnatal production of the follicles and the role of multioocyte follicles, are discussed. The importance of the ovarian follicular reserve is considered for fertility and reproductive parameters, as well as some questiones about the presence of multioocyte follicles in adult ovaries. Finally, some future prospects are proposed.(AU)

Reproductive performance of ewes treated with an estrus induction/synchronization protocol during the spring season

The aim of this study was to evaluate the reproductive performance of ewes treated with eCG and an exogenous progestagen protocol during the spring season. Forty - eight mixed - breed wool and hair ewes ( body condition score of 2.8 ± 0.5 and 41 ± 3 kg ) were randomly assigned into two groups ( n = 24/group), which received (G - Sync) or not (G - Control) an intravaginal device ( Day 0) containing 60 mg of medroxyprogesterone acetate. On D ay 7, ewes of the G - Sync were injected with 300 IU of eCG and 30 ug of d - C loprostenol, im . On D ay 9, the device was removed and 12 h later males were introduced into the G - Sync and G - Control groups in a proportion of 1:6. Estrus response observation and mating were performed during D ays 10, 11 and 12 from 7 to 9 AM and 4 to 6 PM. After D ay 12, males were s eparated from females for 10 days and later reintroduced into the flock for 45 days. Estrus rates for the G - Control and G - Sync group s during D ays 10, 11 and 12 were 4 and 88 % (P < 0.05) , respectively . Pregnancy rates fr om initial mating on D ays 10, 11 and 12 were 0 (G - Control) and 4 6% (G-Sync;P < 0.05). Total pregnancy rates for the whole mating season were 50 (G-Control) and 79% (G-Sync;P< 0.05). The exogenous progestagen protocol plus eCG used for estrus induction/s ynchronization improved the pregnancy rate of mixed-breed wool and hair ewes by about 29% points at the end of the breeding season. Thus, this procedure seems to be appropriate to be implemented as part of the reproductive management of some ovine farms during the non-breeding season.

Reproductive performance of ewes treated with an estrus induction/synchronization protocol during the spring season

The aim of this study was to evaluate the reproductive performance of ewes treated with eCG and an exogenous progestagen protocol during the spring season. Forty - eight mixed - breed wool and hair ewes ( body condition score of 2.8 ± 0.5 and 41 ± 3 kg ) were randomly assigned into two groups ( n = 24/group), which received (G - Sync) or not (G - Control) an intravaginal device ( Day 0) containing 60 mg of medroxyprogesterone acetate. On D ay 7, ewes of the G - Sync were injected with 300 IU of eCG and 30 ug of d - C loprostenol, im . On D ay 9, the device was removed and 12 h later males were introduced into the G - Sync and G - Control groups in a proportion of 1:6. Estrus response observation and mating were performed during D ays 10, 11 and 12 from 7 to 9 AM and 4 to 6 PM. After D ay 12, males were s eparated from females for 10 days and later reintroduced into the flock for 45 days. Estrus rates for the G - Control and G - Sync group s during D ays 10, 11 and 12 were 4 and 88 % (P < 0.05) , respectively . Pregnancy rates fr om initial mating on D ays 10, 11 and 12 were 0 (G - Control) and 4 6% (G-Sync;P < 0.05). Total pregnancy rates for the whole mating season were 50 (G-Control) and 79% (G-Sync;P< 0.05). The exogenous progestagen protocol plus eCG used for estrus induction/s ynchronization improved the pregnancy rate of mixed-breed wool and hair ewes by about 29% points at the end of the breeding season. Thus, this procedure seems to be appropriate to be implemented as part of the reproductive management of some ovine farms during the non-breeding season.(AU)

Reproductive performance of ewes mated in the spring when given nutritional supplements to enhance energy levels

The objective of this study was to evaluate the reproductive performance of ewes mated in the spring when given nutritional supplements to enhance energy levels. Ewes were assessed for weight and body condition at the beginning and end of flushing periods. Lambing rates and rates of proliferation were also evaluated. Crossbred woolly ewes (n = 46), 36 ± 2 months of age and rated 3.0 ± 0.1 on a body condition scale that spanned from 1 to 5 were divided into four treatment groups. One group received no feed supplements (NFS), while the others were supplemented for 64 days: 21 days before and 43 days during the mating season. The latter groups were fed soybean hulls at 0.6% (S06), 0.9% (S09) and 1.2% (S12) of their body weight (BW), calculated using dry mass. Ewes were mated for 50 days with four rams by means of natural breeding in October and November, which is spring in Brazil. There was no significant difference among the treatments based on mean BW of the ewes before and after the supplementation period (P > 0.05). Similarly, no differences were found in the rates of proliferation (P > 0.05). The S09 treatment presented the highest lambing rate (82%, 9/11), while the NFS treatment correlated with the lowest rate (42%, 5/12; P < 0.05). There was a positive linear effect for body condition score as the supplementation level increased (P < 0.05). We conclude that a supplementation level of 0.9% BW seems to improve lambing rates for ewes that undergo springtime mating.(AU)

Reproductive performance of ewes mated in the spring when given nutritional supplements to enhance energy levels

The objective of this study was to evaluate the reproductive performance of ewes mated in the spring when given nutritional supplements to enhance energy levels. Ewes were assessed for weight and body condition at the beginning and end of flushing periods. Lambing rates and rates of proliferation were also evaluated. Crossbred woolly ewes (n = 46), 36 ± 2 months of age and rated 3.0 ± 0.1 on a body condition scale that spanned from 1 to 5 were divided into four treatment groups. One group received no feed supplements (NFS), while the others were supplemented for 64 days: 21 days before and 43 days during the mating season. The latter groups were fed soybean hulls at 0.6% (S06), 0.9% (S09) and 1.2% (S12) of their body weight (BW), calculated using dry mass. Ewes were mated for 50 days with four rams by means of natural breeding in October and November, which is spring in Brazil. There was no significant difference among the treatments based on mean BW of the ewes before and after the supplementation period (P > 0.05). Similarly, no differences were found in the rates of proliferation (P > 0.05). The S09 treatment presented the highest lambing rate (82%, 9/11), while the NFS treatment correlated with the lowest rate (42%, 5/12; P < 0.05). There was a positive linear effect for body condition score as the supplementation level increased (P < 0.05). We conclude that a supplementation level of 0.9% BW seems to improve lambing rates for ewes that undergo springtime mating.