The average lactation yield and the fat and protein composition of milk for three dairy breeds are shown in the table below: | Breed | Milk Yield (kg) | Fat (%) | Protein (%) | |-------|-----------------|---------|-------------| | A | 4350 | 5.3 | 4.1 | | B | 6450 | 4.1 | 3.5 | | C | 5240 | 4.8 | 3.9 | (i) Which breeds are represented by A, B, and C? (ii) Give a reason for your choice in each case - Leaving Cert Agricultural Science - Question 5 - 2016

A (Jersey) is known for its high butterfat content; B (Holstein) is known for its high yield; C (Frisian) typically has a lower yield but relatively high butterfat and protein percentages.

The percentage of fat in colostrum typically ranges from 4% to 7%, and protein can range from 14% to 16%.

1. Age of cow: Older cows may have different fat content due to hormonal changes.
2. Stage of lactation: Early lactation may yield lower fat, while later can yield higher fat content.
3. Diet quality: Higher energy diets lead to increased fat in milk.
4. Health status: Health issues can alter metabolic processes and affect fat synthesis.

Young heifers (around 15 months) should weigh between 500-580 kg at calving. If they are underweight or in poor condition, they may face irregular heat cycles leading to delayed conception. Conversely, well-conditioned heifers are likely to breed earlier, ensuring timely calving.