VN May 2023

Vetnews | Mei 2023 7 Reproduction Goats are seasonal breeders. The breeding cycle in some breeds is very limited due to daylight length, but many breeds have evolved to breed almost all year round. The oestrus cycle can be induced out of season using hormones, the buck effect and light manipulation. Goats do not short cycle as much as sheep do after a period of anoestrus, but it occurs. They will often have silent heat after an anoestrus period. An oestrus cycle is about 21 days, and pregnancy is slightly longer than sheep at about 149 days. Maintenance of pregnancy is mostly dependent on progesterone from the corpus luteum. This means that goats are much more prone to abortions than sheep. Culling for abortions is important as there seems to be a genetic trend with some does becoming habitual aborters. Abortions “storms” can be brought on by changes in nutrition, handling, adverse weather, infections, mineral deficiencies and transportation. Pseudopregnancy is also a problem because if the corpus luteumpersists, the“pregnancy”will bemaintained .2,16,17,18,19,26 Pregnancy toxaemia is a problem in goats, especially if they are overfed because of the fat in the abdomen, which leads to limited space for the rumen. It can often be fatal and immediate treatment is necessary. Fluids, energy supplements and induction may save the doe’s life. Treatment depends on the severity of the case. Oral propylene glycol, calcium, magnesium and b-complex vitamins are usually adequate for mild cases. Giving IV fluids, including potassium and insulin, may be necessary for more serious cases. Does develop a metabolic acidosis which can cause blood pH to drop and thus cause death. Research suggests a pH of less than 7.15 is very serious, and these cases need all the above treatment but also either induction or a C-section to save the does and offspring. 3,4,9,21,22 Goats have a much higher milk production than sheep, and milk production is apocrine, meaning milk globules are pinched at the end of the cell, surrounded by a cell membrane, and contain cytoplasmic droplets with mitochondrial DNA. The gland cistern can hold 40-80% of the milk volume compared to 30% in cows. The milk let-down reflex is very important. The doe can be milked out due to the large cistern volume, but if the let-down action does not happen, insufficient oxytocin will result in the milk not containing the alveolar fraction, which contains most of the fat globules. Does can also have ectopic mammary tissue, for example, around the vulva. This will only become apparent during the first lactation. These areas can develop a mastitis-like disease which can cause scarring and infection. 3,4 Leading Article >>> 8