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Rump Structure and How it Affects the Mammary System

By Lorelei Hallock, Coyote Kidz

Rump- strong, uniformly wide and nearly level from hips to pin bones and thurl to thurl; thurls set two thirds of the distance from hips to pin bones; well defined and wide pin bones set slightly lower than the hips; tailhead slightly above and smoothly set between pin bones; tail symmetrical to body and free from coarseness; vulva normal in size and shape in females (normal sheath and testes in males).

Sr. Does-5 Jr. Does- 7 Bucks-6

Recently ADGA made changes to the official score card separating the rump into its own sub-category under general appearance. This is a really good change to emphasize just how important the rump structure is in relation to milk production. Quoting advanced ADGA Judge Trinity Smith Malmanis, the rump is like a garage for the mammary. We want Mac Truck sized udders, but if we have a garage built for a Prius and we try to park a Mac Truck in that garage, there is going to be damage to both the vehicle and the garage. So how exactly does the rump effect the mammary? Let’s take a closer look.

First off, when we start honing in on one aspect of the scorecard, it is important to keep in mind other aspects of the animal’s conformation and how biomechanics of one trait will affect other traits. In other words, the rump needs to be balanced with the rest of the body. We as breeders like seeing long rumps but that length should be in proportion to the rest of the back. The chine, loin and rump should be relatively equal in length for each of those parts to be level and smoothly blended into each other. When one of those parts is too short or excessively long, the other parts can be thrown off kilter. Much like when you have a set of link-n-logs. If one log in the basic frame is the wrong length the balance and structure is then warped. When we’re looking at a goat and we notice a steep rump, that can be caused from the rump structure being too short (from hips to pins) or too long in proportion to a shorter chine or loin. While a steep rump isn’t ideal some slope from the hips to pins is necessary. If the rump is too level or the pins are higher than the hips, we may start to see issues with conception rates as the cervix is put in a position that makes breeding difficult. This can also cause issues after kidding with those goats not being able to fully flush the birthing fluids which could lead to infections.

The length of rump will directly affect the capacity of the mammary when viewed from the side profile. When we look internally, the mammary is primarily supported by the medial suspensory ligament. This divides the halves of the udder and connects to the hip bone structure to hold the mammary close to the body. Much like supportive trusses on a bridge, the hips need to be a sturdy wide structure for the cables or connective tissue to attach to. A short and narrow rump then allows for less area for that connective tissue. Does with a short rump will often have little to no extension or fullness in the fore udder. Does with a longer rump structure tend to have more balanced capacity, one-third of the capacity visible in front of the leg, one-third under the leg, and one-third behind the leg.

We talk about width a lot in several aspects of the scorecard, and the rump is no exception. Width is what allows a goat to have room for birthing kids and a full mammary system when viewed from the rear. Anyone who has ever had to reposition a kid will tell you how much easier it is when a doe is naturally build wide and “roomy” for those kids with really big heads to come out. Width in the rump is also going to give more space between the rear legs for a larger “Mac Truck” mammary. When we have a doe that is not showing width between the thurls and/or pins, that doe is going to have a more difficult time moving her legs around a very full udder. This can lead to bruising and if severe enough, cause chronic issues with mastitis from that bruising. The wider hip structure is equivalent to stronger framework of a larger garage. When there is lots of width from thurl to thurl, the hip joint is going to allow a smoother motion of the femur and thus a stronger straighter motion in the whole leg as the goat moves. If the pin bones are wide with the rest of the hip structure, that will help the width of the rear udder and arch into the escutcheon. The continued width of the hips will allow the goat to have more natural width between the hocks, again allowing for the rest of the leg to function smoothly, walking around a large mammary instead of rubbing against it.

There are many more things that can be said about the rump, but these few things are a good start when learning to look at the rump of a dairy goat. Keep in mind this is just one portion of a bigger picture. Each part of the goat is going to have a function with cause and effect on other parts of the goat. Learning to understand the function of each area of the scorecard is a step in understanding the building blocks we use to breed balanced, healthy and efficient dairy goats.

ANDDA May 2022 Newsletter - Copyright 2022

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