Milk Replacer vs. Ewe’s Milk

It’s time to look ahead to this spring’s lambing season. Should you feed milk replacer or ewe’s milk to the 2016 lamb crop? New research from Cornell University provides insight to this query.

The study, conducted by Ann DiPastina in conjunction with Dr. Debbie Cherney, looked to answer two questions: Does the composition of ewe’s milk change through lactation? And, are the growth rates different between lambs on milk replacer compared to those on ewe’s milk.

For the study, twin lambs were separated into two groups: lambs fed milk replacer and lambs left with the ewes to be raised naturally. Artificially reared lambs were housed in a little more than 9-square-foot pens in pairs and offered free-choice access to Land O’Lakes Ultra Fresh Optimum lamb milk replacer. Naturally reared lambs were housed with their dams in 12-square-foot pens with access to a slightly smaller creep area.

Read on to discover the team’s findings:

QUESTION 1: DOES THE COMPOSITION OF EWE’S MILK CHANGE THROUGH LACTATION?

The first phase of the research focused on the ewes and their milk production. The objective was to measure potential changes in milk composition.

With this concept in mind, the Cornell team collected 35 milliliter (about 1.7 cups) milk samples from each ewe six times per day at lacta-tion days 18, 19, 20, 38, 39 and 40. Samples were analyzed for percent fat, protein and lactose by time of day and stage of lactation.

“There was a significant difference in average protein and lactose percent between the two periods; Period 2 was higher in protein and lower in lactose than Period 1 milk,” said DiPastina, adding that averages over time were equal to milk replacer components.

Differences were also noticed  based on the time of day the milk was collected.

By volume, ewes in early lactation produced the highest milk volume at 4 a.m. and 8 a.m. with a drop be-tween noon and 8 p.m. Production then increased again near midnight. A similar trend was found as lactation progressed but with a second peak occurring earlier in the evening at 8 p.m.

“While these nutrient levels are fixed in milk replacers, composition varies in ewes’ milk due to many environmental factors, litter size, nutrition and breed,” DiPastina found. “Fat percent has been shown to drop rapidly in the first three weeks of lactation with a gradual increase until 250 days in milk.”

QUESTION 2: ARE GROWTH RATES DIFFERENT BETWEEN LAMBS FED MILK REPLACER AND EWE’S MILK?

Realizing the differences in consistency, the researchers next looked into growth rates between lambs fed milk replacer and ewe’s milk.

As outlined earlier, lambs were randomly split into two groups: those offered lamb milk replacer and those who remained with the ewe. Lambs were weighed daily at 8 a.m. until 30 days of age; creep feed and milk replacer intake were measured three times daily.

The results were on par with views on consistency, with average growth rates higher for lambs fed milk replacer (0.66 pound/day as compared to 0.62 pound/day for lambs naturally reared). The consistency in nutrition also helped fallouts match their counterparts.

“The artificially-reared lambs were smaller, on average, than naturally-reared lambs at birth but tended to reach the same final weight at day 30,” says DiPastina.

Creep feed consumption between the two groups was nearly uniform; thus, the researchers point to consistency in nutrition as a driver in the increased growth rates.

“A potential reason for the elevated growth rates in artificially-reared lambs could be the consistency of energy intake,” says DiPastina. “Results indicated that milk yield varies significantly throughout the day. Lambs’ intake levels may have therefore fluctuated throughout the day as well.”