Don't chase milk litres at expense of cow condition
Published 21/09/2010 | 05:00
Awell-known and practically minded scientist once told me that in autumn there are only three points that need to be considered on a spring-calving, grass-based dairy farm. These are cow condition, cow condition and cow condition. Obviously this is a simplistic view. However, while autumn milk production provides necessary income, do not be tempted to milk on and forgo body condition score to chase milk litres in the tank.
Having spring calving cows in the correct body condition score by the end of December is critical to the success of next year. Milking condition score off cows will cost you dearly in terms of both next year's milk production and reproductive performance. For example, a study by McNamara et al (2001) showed that cows that calved below a condition score of 2.75 produced on average four litres a day less during the first eight weeks of lactation, compared to cows that calved at a condition score 3.0.
Other studies have also shown negative effects on the anoestrus period (8-10 days longer), three-week submission rate, and the pregnancy rate to first service and after 42 days. It's also a consequence of these negative effects on reproductive performance that milk production will also be reduced in the following year due to a prolonged calving interval. The double whammy.
Reading this you may feel that you can quick-fix condition score during the dry period of December and January. However, in the past eight weeks of pregnancy, cow liveweight increases by almost 0.6kg/day due to the growth of the foetus and placenta alone.
Consequently, over this eight-week period, a well-fed animal achieving a good daily liveweight gain of 1kg is only equivalent to about 0.4kg in actual body weight and will result in an increase of only about 0.5 units in condition score. So, put simply, taking into consideration that during the actual process of drying off, where cows do not put condition score on and may actually loose a bit for a good week to two weeks, by mid-November cows need to a minimum condition score of 2.75 plus to hit the target calving condition score of 3.25 by February. And this is not a desired average score. This is the target for the light, thin cows and heifers too. Remember, your first calvers generally have a lower condition score than the cows.
So from September onwards, condition score moves to the top of the priority list, and even above cash flow. So how do we learn the skill and implement it on farm? Condition scoring is a visual assessment of the cow's body reserves. Most of you would have walked into the paddock where the cows are grazing on your own farm, or as part of a discussion group, and given your opinion freely on how you felt they looked on the day. The common comments of 'they're generally fine', 'they're good', 'a good 2.9', for example, all spring to mind but is this good enough? I'm afraid not. As condition score is a subjective measure, all dependent on personal opinion, eyes need to be calibrated in and around 20-30pc of the cows to be scored. An average score is then calculated from these individual scores and, more importantly, the percentage of cows that are less than 2.75 noted.
Condition-scoring is not a hard skill to learn and to get your eye calibrated, either on your own farm or as part of a group, line up 12-15 cows of varying condition. Handle the animals to determine the amount of flesh covering the key body points of the backbone, ribs, short ribs, hip bone, thurl (between hip bone and pin bone), pin bone and tail head. To aid you in this process next week I will give you a simple chart. However, this week, if you're concerned and feel your cow condition score needs to be addressed, do the following:
- Identify your thin cows and heifers that have very visible notches in the backbone and with sharp and angular ribs, hips, and pin bones, along with a very depressed tail head.
- Take either your scanning data or mating data and identify your January/February calvers.
- If any cows or heifers fall into both categories of being thin and early calving, get ready to dry them off in October. Thin cows need extra time and extra feed.
Condition scoring also applies to cows that are being mated as an autumn calving block/herd. For any very thin cows or heifers, mitigate against any additional factor that may have caused them to be thin (eg, lameness, cow hierarchy etc), feed them well and consider once-a-day milking to help them have a chance during mating.