The Effect of Stocking Rate and Supplementary Concentrate Feeding on Milk Production

Abstract

The effect of stocking rate and of feeding a supplement of barley on milk yield and quality was studied in an experiment with 18 spring‐calved Ayrshire cows grazing from early May until early September in 1964 and 1965. Three treatments were compared: (A) grazing at a normal stocking rate with no supplements fed (the control); (B) grazing at a high stocking rate with no supplements fed; (C) grazing at a high stocking rate, as on treatment B, with a supplement of 8 Ib rolled barley per cow daily. On treatment A, 0.92 ac/cow was used for grazing, plus some conservation, and on treatments B and C, 0.70 and 0.58 ac in 1964 and 1965, respectively. The average daily milk yields were 35.4, 32.9 and 37.0 Ib (16.1, 14.9 and 16.8 kg), respectively, on treatments A, B and C in 1964, and 39.1, 32.3 and 38.8 Ib (17.8, 14.7 and 17.6 kg) in 1965. Milk production/ac was 24 and 32% higher on treatment B than on treatment A in 1964 and 1965, respectively. The response to the barley feeding on treatment C was equivalent to an extra 1 gallon milk from 20 Ib barley in 1964 and from 12 Ib barley in 1965 (10 litres of milk from 20 and 12 kg barley). The total‐solids content of the milk from the three treatments was not significantly different. It is concluded that, at the present price of barley and the price received for milk, an increase in stocking rate, with a consequent increase in the milk yield per acre, was more profitable than feeding barley.

Some Factors Affecting Milk Production From Grassland at the Hannah Institute, 1951–70

“…The importance of milk yield/ cow per year should not be underestimated, and in our results it was clear that increases in this measure were partly responsible for the increases in total farm output. In short-term grazing experiments the yield of milk per cow generally decreases as the stocking rate increases, although the total amount of milk produced/ac increases (5,9). This did not occur in this study and indeed yields increased from about 700 to 950 gal/cow as the acreage of land decreased from about 2 acres to 1-5 ac/cow.…”

“…Since 1950 considerable reliance has been placed on grassland for milk production on the farm at the Hannah Institute. Numerous shortterm summer-grazing experiments (5,9) and winter-feeding experiments (4,8) have been conducted and, in addition to these, the farm itself has been the subject of detailed investigations. Grassland management has always been a complementary study to the other experiments; one of the purposes of the farm has been to explore and develop methods which would increase milk production from grass economically.…”

Effect of Stocking Rate on Pasture Production, Milk Production, and Reproduction of Dairy Cows in Pasture-Based Systems

“…This is consistent with the positive association between milk production per hectare and SR in many studies (Gordon, 1973;Baker and Leaver, 1986;Dillon et al, 1995). However, many of these experiments were short term (Castle et al, 1968;Gordon, 1973;Baker and Leaver, 1986;Kennedy et al, 2006), compared insufficient SR treatments (<3) to determine an optimum SR (Foot and Line, 1960;Castle et al, 1968;Gordon, 1973;Dillon et al, 1995), or included the use of purchased supplementary feeds (Fales et al, 1995), in effect modifying the true effect of SR on the biological (pasture utilization, milk production/cow, milk production/ha) and economic variables measured. Furthermore, much of this research is more than 30 yr old and may no longer be applicable to the modern dairy cow breed and strains being used globally.…”

“…Previous research investigating the effect of SR in grazing systems on milk production per cow and per hectare did not allow us to predict the effect of SR change. The research in question was either short-term and unable to account for the complete farm system (Castle et al, 1968;Baker and Leaver, 1986;Kennedy et al, 2006), was undertaken more than 30 yr ago (McMeekan, 1956;Foot and Line, 1960;Castle et al, 1968;Gordon, 1973), and considering the advances in cow genetics and farm management over that time, may no longer be applicable; or they merely compared "high" vs. "low" SR treatments, making it impossible to determine an optimum SR for any production system or to extend their results beyond the system investigated (Foot and Line, 1960;Castle et al, 1968;Gordon, 1973;Dillon et al, 1995).…”

“…Stocking rate (SR) is defined as the number of animals allocated to an area of land (i.e., cows/ha), and it has been recognized as the primary driver of milk production per hectare and profitability in grazing systems for over half a century (McMeekan, 1956;Castle et al, 1972). Extension of short-term studies investigating the effect of pasture allowance on DMI and pasture utilization indicates an increase in pasture utilization and a decrease in per cow production as SR increases (Castle et al, 1968;Gordon, 1973;Baker and Leaver, 1986;Kennedy et al, 2006), and this is consistent with full lactation studies (Dillon et al, 1995). Increasing SR therefore negatively affects the amount of pasture available to each animal, but increases the amount of pasture harvested per hectare.…”