Mares lactation

Body lipids are mobilized during exercise and are oxidized readily during strenuous exercise like gafloping. Physically conditioned horses oxidize fat more efficiently than nonconditioned horses. Hyperlipidemia is an important clinical problem in small pony breeds. It is most common in mares in late gestation and lactation and occurs when the animal is in negative energy balance. 

Mares with placentitis may exhibit signs of premature lactation, vaginal discharge and fever in late... 

Oxytocin may be used to facilitate the contraction of the mammary alveolar myoepithelial cells and thus promote milk ejection. After the mammary gland has been emptied manually, i.v. oxytocin (20 lU) will allow the additional collection of milk from lactating mares. 

Mastitis may be observed at any stage of lactation and has also been seen in non-lactating, nul-liparous mares and in fillies. Mastitis occurs most commonly in the summer months and is often associated with Strep, equi subsp. zooepidemicus infection. The treatment of mastitis usually includes the parenteral administration of appropriate antimicrobial agents (see Ch. 2). The udder may also be treated using frequent milking, hydrotherapy and infusion of commercially available intramammary preparations for cattle. A NSAID may be administered to treat both the fever and the discomfort associated with mastitis. 

These results suggest that the effects of endophyte consumption on digestibility and growth rate may be lessened by the inclusion of concentrates in the diet. In contrast, energy supplementation has no beneficial effects for alleviating lactation and reproductive problems in gravid mares that graze E+ pasture (Earle et al., 1990). 

The yield of milk varies with breed, age, stage of lactation, nutrient intake in the late stages of pregnancy, current nutrient intake, and water availability. Some typical milk yields for mares of different liveweights are given in Table 16.20. 

Table 16.20 Typical milk yields (kg/day) of mares of various body weights during weeks 1-25 of lactation...

Yield for brood mares (kg/day) may be predicted as 3 per cent of liveweight during the first 3 months of lactation and 2 per cent of liveweight for months 4-6. For ponies the corresponding percentage values are 4 per cent and 3 per cent respectively. Alternatively, milk yield may be estimated as follows ... 

In addition to the requirement for the production of milk, the diet of the lactating mare must provide the energy for maintenance. NRC (2007) proposes for mares of less than 700 kg that DE required for maintenance (DE j) is calculated as follows ... 

The net protein requirement for milk production is the protein content of the milk. Up to day 22 of lactation, the crude protein content of milk (g/kg) can be estimated as 10 X (3.43 - 0.066 d), where d = days in milk. After day 22, milk protein concentration is assumed to be 19.6 g crude protein/kg. Using an efficiency of utilisation of 50 per cent and a digestibility of 79 per cent results in a dietary crude protein requirement for milk production of approximately 50 g/kg milk. Previous protein requirements were based on digestible crude protein, but more recently NRC (2007) argues that the lack of information regarding digestible crude protein content of feed-stuffs commonly fed to horses does not justify its use, and that requirements should be based on dietary crude protein. The crude protein requirement (g/day) for maintenance is therefore calculated as 1.44 W and total requirements for milk production as CP requirement = 1.44W + 50Y. For a 500 kg mare producing 15 kg of milk, the daily crude protein requirement (g/day) is estimated as 720 + 750 = 1470. 

The amino acid balance in the protein is considered by NRC (2007) to be the sum of that required for maintenance and milk production. Lysine requirements for maintenance are 4.3 per cent of CP requirements and lactation requirements are 3.3 g/kg milk. For a 500 kg mare producing 15 kg of milk per day, total lysine requirements (g/day) are ... 

The mineral composition of mare s milk varies with stage of lactation. For the purpose of estimating dietary requirements, the following values are acceptable ... 

Table 16.21 Suggested minimum and maximum aiiowances of some vitamins for lactating mares...

BOX 16.14 Calculation of the nutrient requirements of a 500 kg mare producing 16 kg of milk in early lactation... 

The milk yield of the mare is related to body weight and stage of lactation. 

The mare s protein requirement for maintenance is related to metabolic liveweight and breed. Production requirement depends primarily on stage of lactation. 

Calculate the digestible energy, crude protein, lysine, calcium and phosphorus requirements for a 600 kg mare producing 15 kg of milk per day in early lactation. 

Maintenance Pregnant and lactating mares Growing horses Working horses... 

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