OPINION
Erastus Ngaruka
In many kraals you would observe particular cows and heifers that are exposed to the bull but the ultimate result (the calf) is not realized as with the rest of the herd, including those from the same age group. Many farmers keep asking, “what should I do with that animal?”. These are mostly the best looking animals in the kraal; deceiving the owners with Beauty and giving them hope, hence the reluctance to make that BIG decision, thus, continuing to invest in these animals. At a point, every animal is supposed to pay for its bills (water, feeds, fuel, labour etc.) on the farm. Reproduction is one mode of payment. If the problem is not with the bull and the cow/heifer, then it is indirectly with the farmer. Genetic, environmental and management factors contribute to the problem. The most common factors amongst others include the animals’ nutritional and health statuses.
Nutrition: Naturally, the peak of animals’ breeding activities coincides with the season of plentiful forage resources. Conception rate is influenced by the nutritional status of the cow/heifer before and after calving because nutrition influences the oestrus activities in cows. Reproduction in beef cows is primarily regulated by energy which primarily controls the release of reproductive hormones (oestrogen, progesterone, GnRH, LH and FSH). The release and the activities of these hormones brings the cow on heat and to ovulate for fertilization to take place ones the cow is mated.
When a cow is not adequately fed during gestation (pregnancy), the body condition decreases at parturition (calving) and thus the onset of oestrus (heat) after calving will be delayed, reducing the conception rate. It is therefore necessary to provide adequate energy feeds to cows especially during the last trimester to avoid excessive loss of body condition and meet the energy demand. The energy demand increases significantly during this period and at lactation because the cows’ milk production has drastically increased. If cows ‘energy demand is not adequately met, it uses the body’s energy reserves (e.g. the fat). When this high energy demand exceeds the energy intake, then the cow may develop a nutritional disorder called Ketosis (“Ondumbo” in Otjiherero), characterized by anorexia (loss of appetite) and depression,
Vitamin A also influences conception rates. A deficiency will reduced fertility and conception rates, and in severe cases, reabsorption of a foetus. Protein deficiency also affects conception indirectly as it reduces the animal’s appetite and thus reducing energy intake, leading to loss of weight, and reduced conception rates because the hormonal activities are supressed by the lack of energy.
Health: A cow’s reproductive potential can be compromised by its health status. There are a couple of reproductive diseases that noticeably or unknowingly prevalent prevail in many kraals or farming areas. These diseases may cause infertility in both cows and bulls. They include; brucellosis, Vibriosis, Trichomoniasis, and Bovine Viral Diarrhea (BVD) amongst others. It is therefore important that animals especially bulls are tested for venereal diseases before the breeding season commences, and that annual vaccinations are carried out.
In conclusion, a breeding program on the farm should be planned in accordance with the farm fodder flow plan as well as the animal health plan. In addition, it is very necessary to evaluate your cattle herd performance every year in order to make informed decisions, and this can successfully be achieved with a useful record keeping system in place.
* Erastus Ngaruka is Technical Officer: Livestock within Agribank’s Agri Advisory Services Division, at Agribank.