Milk yield and reproductive performance of Holstein cows testing positive for bovine tuberculosis.

The objective of this study was to determine if high milk-yielding Holstein cows testing positive for bovine tuberculosis (bTB) are affected in their reproductive performance and milk yield. For this purpose, 1044 healthy cows and 105 bTB reactor cows were used. Tuberculosis reactor cows were from four large commercial dairy operations from the same region which were transferred from their barns to an isolated dairy facility. Cows free from this disease were placed in the same barn as the bTB reactor cows but in an isolated division and served as control animals. The analysis of variance with a general linear model for binary data showed that the reproductive performance of bTB reactors was impaired; overall pregnancy per artificial insemination differed (P < 0.05) between bTB reactor and non-reactor cows (16.9 vs. 20.7%). Cows that were TB reactors required 4.7 ± 2.9 services per pregnancy compared with 4.3 ± 2.8 for control cows (P > 0.05). The intervals between calving and conception were similar between bTB reactors (154 ± 78 days) and control animals (150 ± 80 days). Control cows tended (P = 0.08) to produce more milk than bTB reactors over a 305-day lactation (10,684 ± 1720 vs. 10,345 ± 1736; mean ± SD). Serum metabolites indicative of nutritional stress did not differ between bTB reactor and non-reactor cows. It was concluded that both reproductive performance and milk yield decreased marginally in bTB reactor cows, which explains the reluctance of milk producers to get rid of these animals.

Estrus induction in anestrous mixed-breed goats using the "female-to-female effect".

A trial was conducted during the anestrous period in female goats to determine: (a) whether estrus can be induced in anestrous goats by administration of equine chorionic gonadotropic hormone (eCG) and PGF2α under pen conditions and (b) whether these sexually active female goats can elicit sexual arousal in sexually inactive bucks. One hundred and fifteen pluriparous, nonlactating mixed-breed female goats were randomly assigned to one of four treatment groups: (1) administration of a single dose of 240 IU of eCG, 50 µg PGF2α i.m., and 25 mg progesterone (P4) (eCG; n=30); (2) administration of P4 and exposure to female goats treated with eCG-PGF2α (P4; n=39); (3) administration of 0.5 ml saline and P4 (Sal; n=23); and (4) P4 plus exposure to female goats treated with saline (Con; n=23). After hormone administration, all goats were put together with adult sexually inactive bucks for 15 days. The percentage of goats in estrus during these 15 days was similar in eCG-treated animals and untreated animals exposed to the eCG animals (97 and 95%). Pregnancy rate was also similar (63 vs. 64%) between these two groups. eCG-treated goats exhibited estrus earlier (P<0.05) than the treated goats in contact with the eCG goats. Furthermore, eCG-treated goats had larger litters (1.9 ± 0.2 vs. 1.6 ± 0.1, P<0.05) than the untreated goats in contact with the eCG goats. These results show that fertile estrus can be induced in anestrous female goats by exposing them to female goats induced to estrus with eCG. This female-female interaction triggers the stimulation cycle leading to the sexual arousal of bucks.

Influence of sexually inactive bucks subjected to long photoperiod or testosterone on the induction of estrus in anovulatory goats.

The objective of this study was to evaluate the efficacy of treating sexually inactive bucks with artificial long photoperiod or testosterone on the induction of estrus in anovulatory grazing goats. A total of 91 multiparous mixed-breed anestrous goats were randomly assigned to one of three treatment groups: (1) joining with bucks subjected to 2.5 month of artificial long days (16 h of light/day; n=31), (2) joining with testosterone-treated bucks (n=30), and (3) joining with untreated bucks (control; n=30). There were no differences between the light-treated (100%) and testosterone-treated (93%) bucks in their ability to induce estrus in anovulatory does. On the other hand, none of the goats in contact with control bucks exhibited estrus. The interval from start of mating to estrus was shorter in goats with the light-treated bucks (37.9 ± 4.8 h) compared with does in contact with testosterone-treated bucks (58.3 ± 8.7 h). The overall pregnancy rate in goats joined with light-treated, testosterone-treated and control bucks was 84%, 77% and 0%, respectively, with no difference (P>0.05) between the first two groups. Anogenital sniffing, approaches, mounting attempts, and mounts were highest (P<0.01) in light-treated bucks and lowest in control bucks. It was concluded that testosterone-treated bucks and long-day-treated bucks were equally effective in synchronizing estrus in anovulatory goats and resulted in similar levels of fertility. Given that light-treated bucks are unviable in communal production systems of goats raised by resource-poor farmers, the sexual arousal of bucks with testosterone is a practical and reliable method to induce ovulation in anovulatory goats in pastoral goat systems in hot environments.

Effect of body condition score of does and use of bucks subjected to added artificial light on estrus response of Alpine goats.

The effects of body condition score of does and exposure to sexually active bucks after exposure to long-day artificial photoperiod were examined in mature anovulatory French Alpine goat in Northern Mexico. In June, goats in good (2.3 +/- 0.2, scale 1 to 4; n = 10) or poor (1.6 +/- 0.3; n = 10) body condition were exposed during 15 day to sexually active bucks, which had been exposed to long photoperiod (16:8-h light-dark cycle, starting in December). A third group of goats in good body condition was exposed to bucks kept under the natural photoperiod of this region (26 degrees N). All goats in good body condition exposed to bucks treated with prolonged photoperiod exhibited estrus behavior, whereas only 50% of the does in poor body condition showed estrous behavior during the 15-day buck exposure. None of the does in good body condition showed estrus when exposed to bucks under natural photoperiod. These results revealed that a good body condition is required for maximum estrus response in anestrous Alpine goats and that exposure of bucks to long photoperiod in winter is essential for an adequate stimulus to reestablish estrus cycles in anovulatory Alpine does in Northern Mexico.

Management of photoperiod to control caprine reproduction in the subtropics.

Reproductive seasonality is observed in some breeds originating from or adapted to subtropical latitudes. In 'photoperiodic flexible breeds', such as Australian cashmere goats, the annual breeding season can be manipulated through nutrition, whereas in 'photoperiodic rigid breeds', such as Creole goats from subtropical Mexico, sexual activity can be controlled by altering the photoperiod. In males from the latter breed, artificial long days, whether or not accompanied by the administration of melatonin, stimulate sexual activity during the non-breeding season. These treated males are able to induce the sexual activity of anoestrous females through the male effect under intensive or extensive conditions. Photoperiodic treatments and the male effect can be easily integrated into different breeding management systems in subtropical latitudes.