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[en] Several researchers have provided sufficient evidence to sustain that the best crossbreeding program to produce milk in the tropics is the direct cross between Bos Taurus and Bos indicus (F1). The problem arises when the farmer faces the challenge to breed the crossbred animal. If the choice is to cross with Bos Taurus the resulting product is quite vulnerable to the harsh environmental conditions in the tropics. If, on the other hand, the selection is to sire with Bos indicus then the offspring will be deficient in milk production. Another alternative is to transfer F1 embryos to F1 dams, hence avoiding the hazards of crossbreeding. Although the technique of embryo transfer (ET) has been available for many years, there are several pitfalls at least under tropical conditions, which need to be considered. Selection of recipients for embryo transfer: The first one is related to the selection of the recipients. These are usually animals displaying spontaneous oestrus or treated with drugs to synchronize their oestrus. The short comings of either of these methods have been experienced by Montiel et al. In short, the use of spontaneous oestrus is time consuming and inaccurate and the response to oestrus with an ensuing ovulation can be as little as 30% if the animals selected are not in reasonable body condition. Embryo transfer programs in small community farms can be tricky because the selection of recipients is restricted to a few animals in the herd and the distance between farms can pose a serious threat to the success of the program. Thus, just because of this constraint, several government programs have ceased to be functional when the subsidy runs out. Production of embryos (F1): The main components of successful embryo production can de divided into three. The quality of the superovulatory response in the donor cow, the ability of the individual to recover as many embryos as possible and the accuracy of the technician to judge the quality of the embryo destined for freezing which has proven to be a difficult task at least under tropical conditions. In relation to the former, figures for embryo production can vary enormously, although some groups demand that the number of good quality embryos cannot be less than eight. However, others have not been so successful. In short, the superovulatory response can be directly related to the follicular dynamics now of treatment. The recovery of embryos can be difficult especially as it has been reported that almost 30% of the donor cows have curved cervices increasing the difficulties in negotiating the catheter. Embryo production can be affected if the conditions are not favourable, in a detailed study, Marquez et al., showed that the number of healthy embryos evaluated by their resistance to freezing and their degree of apoptosis, was affected if the embryos were produced in the spring or the autumn. Economical feasibility of ET among small community farmers: Government organizations in developing countries have launched initiatives to popularize the evident benefits of ET, particularly in enterprises not bigger than 50 cows per unit. These programs have experienced a high degree of acceptance, especially those with a substantial subsidy. However, when the program folds UP, it has proven not to be sustainable for the farmers themselves, thus disappointment is the natural course of events. In a recent study found the estimation of the cost involved in the preparation of the donor and embryo recovery was about US 600.00. The average number of embryos recovered was 3.8. Taking into consideration the cost of gestation, calculated by the percentage of animals pregnant (27%); the cost for preparing the donor, the technique of embryo transfer and the cost of production of the embryo itself, the overall cost per gestation was $1320. Considering a 50-50 ratio of males-females born, the cost for a replacement heifer was 2640 dollars, which surpassed by far the commercial cost of a crossbred heifer (approximately 900 dollars). Considering the difficulties in distributing F1 embryos among farmers in small enterprises, the cost of production and the low success rate found in terms of fertility, for the time being IT does not seem profitable for farmers themselves to sustain a program of this investiture. Government organizations would need to play a more active and systematic role to ensure the reduction of the costs inherent embryo transfer techniques. (author)

[en] In response to many requests from our readers, I will continue to highlight a practical topic related to animal production and health in this section of the newsletter. Increasing the efficiency of animal reproduction is a critical component of a holistic approach to sustainably increase animal productivity in developing Member States. For example, the resources spent to formulate and obtain the ingredients for dairy rations are wasted when a significant proportion of the cows in the herd are dry due to delays in achieving pregnancy. Effective genetic selection to improve productivity is only possible if a regular supply of potential replacements is generated by the females already in the herd or flock. For this reason, improving reproductive efficiency is a key aspect of many of the APH projects

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[en] Risk factors for stillbirth were studied in a dairy operation in northern Mexico (25°N). Data set consisted of 29406 full term calving records. Factors affecting stillbirths were analyzed using a step-wise multivariable logistic regression models. The predictive indicators of stillbirth risk were: temperature-humidity index (THI) during pregnancy and at calving, season of calving, calf birth weight, gestation length, semen characteristics (conventional or sexed), gender of calves, hour of calving and type of parturition (normal or dystocic). Throughout the study period, 7.3 (95%, confidence interval= 7.0–7.6) of every 100 calving events had a stillborn calf. Stillborns were higher with severe dystocia compared with non-assisted births (29.0% vs. 6.2%, p<0.0001) and calves with birth weights <35 kg compared with heavier calves at calving (19.3% vs. 2.3%, p<0.0001), and was lower in calves whose gestation length was >278 d compared with calves with shorter gestation periods (2.8% vs. 30.0%, p<0.0001). Cows in a severe state of heat stress prenatally and at birth (THI >83 units) had 1.3 higher risk of stillbirths than cows suffering reduced heat stress (p<0.0001). Evidence for a greater (p<0.001) stillbirth rates in cows with parturitions between 18:00 and 19:00 h compared with cows calving during other hours of the day was found (9.1% vs. 7.1%). Together, these results demonstrate that ameliorating heat stress during the peripartum period is an important management practice to reduce stillbirths in Holstein cows in this warm climate. Additionally, a greater attention of parturition around sunset can lower the current stillbirth rates.

[en] Forty-eight pregnant zebu cows were equally divided in 2 groups (GO and GC). They were fed on natural pasture and only GC received a concentrate, 1.76 FU and 489.9 DNM/kg DM. From the 7th day post-partum to the 4th of lactation, cows in each group were reallocated in 2 lots, a control (GOO and GCO) and a complemented lot (GOC and GCC). Body weight (BW) and score were monthly recorded in cows and calves. Plasma progesterone was determined from weekly sampled blood. Cows BW at calving did not differ, 264.2 kg in GO and 269.7 kg in GC. Concentrate supply increased BCS (1.5 vs. 0.5, P < 0.05) at calving and complemented cows lost more BCS (-0.9 in GCO and -0.5 in GCC, P < 0.05). At week 21 of lactation, calves from cows in GCC gained more BW when compared to those in GOO (43.4 vs. 34.6 kg, P < 0.05). The intervals between calving and reactivation of the ovarian cycle were 31 d in GCC vs. 42 d in GCO, and 56 d in GOC vs. 78 d in GOO. The percentage of reactivation of the ovarian cycle was 50, 42.8, 27 and 25% in these respective groups. (author)

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