Using artificial insemination (AI) allows a dairy farmer access the best bulls in the world so as to get the desired improvements in the daughters born from this bull. For size, this improvement will be seen after birth and during the growth of the calf and for milk, this will be seen after about 2.9 years from the day the mother conceived after the daughters give birth. This long time line and the fact that you will not want to maintain a poor cow means you should get the best possible improvements in the heifer as compared to their mother.
Therefore all farmers are advised to carefully choose the bull to use for AI in their heifer/cow and confirm that your inseminator will have it in stock long before the animal will need it.
Choosing the best bull to use on your heifer
Semen is produced from highly selected bulls by organisations authorised to do so by veterinary bodies in many countries in the world. In theory, you can access any of their bulls but in practice, for most people, you will be limited by its availability or its price (due to demand and supply forces) or as determined by their marketing agencies. Today, the Kenya Animal Genetic Resource Centre (KAGRIC) formerly the Central Artificial insemination Centre (CAIS), a government parastatal, is the only local producer of semen.
However, there are many companies importing semen from around the world. Both the local and imported semen are regulated by the Veterinary Authority to ensure semen sold in Kenya meets the required standards. They all have agents in all or most counties whose farmers are using AI from where farmers and inseminators can access the semen of their choice. Obtain their location from the nearest veterinary office or your inseminator.
Individual farmers may also import their own semen after satisfying the necessary conditions and procedures set by the Veterinary Authority. Also if a farmer feels she’s got an outstanding bull she wants to use, she can get the experts to collect semen from the animal at a cost. But she can only use the semen in her own animals and not anyone else’s. In order to choose a bull, you will need to go through booklets called a Sire Catalogue found at the marketing agents or with your inseminator.
Each semen producer provides the sire catalogue in which it provides pictures of its bulls, dam and daughters of these bulls. It gives details about its parents (pedigree), its daughter’s milk production including butterfat and protein yields, it gives specifics on quality of udder, feet and legs plus characters that make a cow a strong dairy type such as thin thighs and legs.
It also tells how fertile the animal is, how easily it gives birth, how easy it is to milk it and how long it is expected to live while still producing reasonable amounts of milk among many other traits. The quality of these traits are described on a scale that is standardised and accepted across the livestock industry. Using this information, you can choose a bull that possesses the characteristic(s) that you desire to be passed on to the daughters you aim to get.
For example, if your cow is a good producer, but has a sagging udder that is prone to injury and mastitis, you can choose a bull that has an excellent rating for improving udders by passing on the characteristic for a strong udder suspensory ligament. For a farmer to get the best choice of a bull, she should have her cow(s) examined (classified) for the characteristics described above to choose a bull that will provide the best chances of correcting any poor characteristics that may be in the cow while still retaining the good traits. Since there are many characteristics that need to be considered, one needs the assistance of a match mating computer programme.
Smaller cows and poor milk production than expected
As a general rule, the bigger the dairy cow is, the more milk it can produce than a smaller cow if both are given maximum feeds and care as recommended. But note that to produce more milk the cow must eat more. A farmer can choose to have a huge cow but she must give it sufficient food for it to produce many litres of milk. Remember bulls that give bigger cows or smaller cows within a breed are there for you to choose.
However, just having a big cow does not guarantee a lot of milk. Today, many farmers are having relatively big cows gotten from AI that are producing as little as 10 kg per day or even less when they could be producing 20-30 kg per day or more. This poor milk yield than expected can be due to inbreeding. This is where the parents of a cow are closely related as in sire and daughter, dam and son, sister and brother. Smaller sized cows than expected can also result from inbreeding even though the parents are bigger. The weight in kilos for heifers of Friesian, Aryshire, Guernsey, Jersey should be about 420-450, 420-450, 375-400, 350-375 respectively by the time they are giving birth at about 24 months.
There are measuring tapes you can buy from reputable veterinary outlets and agrovets to assist you to estimate a heifers/cows weight by measuring its girth. Estimating the weights regularly will tell you whether you are on track during the growth of the heifer and in case you are not you will need to decide to take the corrective action as soon as possible. It is suspected that the inbreeding problem is quite significant in small holder farms where farmers are keeping animals without any records of their parents. This is so in situations where farmers are using AI or neighbours or communal bulls and where farmers have bought cows/heifers from outside where no parental records exist.
A research in such small holder farms indicated that many farmers do not properly store the AI certificate set they are issued with and in subsequent months or years cannot produce it and neither do they record the information anywhere and so the sire of their heifer will remain unknown to them. A significant number of farmers were also found to be purchasing heifers/cows from other regions with no records so that their sires will remain unknown. Another significant group of farmers use neighbours/communal/own bulls of unknown parentage. So you are advised to always have parental records of all your heifers/cows to avoid inbreeding!