Covariate Period Research Articles

The effect of amount of protein in the concentrates on hay intake and rate of passage, diet digestibility and milk production in British Saanen goats

ABSTRACTDuring the first 2 weeks after kidding, 27 multiparous British Saanen goats were offered 1·5 kg hay (98 g crude protein (CP) per kg dry matter (DM)) and from 0·45 increasing to 0·70 kg concentrates (152 g CP per kg DM) daily. Week 2 was used as a covariance period. At week 3 of lactation all the goats were allocated to one of three groups and were offered hay ad libitum and 1 kg concentrates containing 117 (LP), 152 (MP) or 185 (HP) g CP per kg DM daily to week 15. During weeks 4 to 15, hay intake and milk yield were highest in the HP group. With increasing protein in the concentrates, hay DM intake was 1·20, 1·19 and 1·37 (s.e. 0·060) kg/day respectively and milk yield was 3·04, 3·21 and 3·36 (s.e. 0·080) kg/day respectively (linear response P < 001). There was no significant effect on the concentration of solids-not-fat, fat, total nitrogen or casein in milk. The digestibility of dietary organic matter, acid-detergent fibre and total nitrogen measured after week 15 was significantly greater with HP than with LP (P < 0·05), with MP values being intermediate (linear response P < 005). The rate of passage of ytterbium-labelled hay was unaffected by the treatments. The results indicate that, with lactating goats given hay and concentrates, beneficial responses may be expected to increasing concentrate CP to at least 185 g CP per kg DM.

Influence of Intake of Rumen Undegradable Protein on Milk Production of Late Lactation Holstein Cows

Twenty Holstein cows, in late lactation, were assigned to five equal groups in an orthogonal design to determine effects of a rapidly rumen degraded protein source (canola meal) low in estimated rumen undegradable protein substituted for a slowly rumen degraded protein source (corn gluten meal) high in rumen undegradable protein on feed intake, milk production, and milk composition. Cows were fed total mixed rations based upon barley silage, haycrop silage, barley grain, and supplemental protein in three 4-wk periods, subsequent to a 4-wk covariate period. In situ rumen incubation of extreme diets and estimation of intermediate diets indicated that all diets exceeded Agricultural Research Council (United Kingdom) recommendations for rumen degradable and undegradable protein as well as NRC recommendations for rumen degradable protein. However, two to four diets, dependent upon assumed ruminal turnover rates, did not meet NRC recommendations for undegradable protein. Dry matter intake and milk yield were not influenced by substitution of canola meal with corn gluten meal to increase dietary undegradable protein content. Daily yield and milk percent of lactose, fat, and protein were not influenced by substitution. Results do not support NRC recommendations to supplement diets based upon these ensiled forages and barley grain for late lactation cows with protein sources resistent to rumen degradation. Results broadly support lower amounts of rumen undegraded protein recommended by the Agricultural Research Council.

Effect of concentrate energy source on lactation performance of dairy cows

Over recent years there has been increasing interest in the diversity of materials which may be used as energy sources in dairy cow concentrates. Traditionally, many dairy concentrates have been based upon cereals with the cereal starch providing a rapidly fermentable energy source. Such diets, particularly on systems where the feeding frequency is low, may depress rumen pH and promote low rumen volatile fatty acid ratios of acetic + butyric : propionic which are associated with the production of milk of low fat content. The feeding of dairy concentrates based upon materials containing appreciable quantities of digestible fibre may be expected to alleviate this problem. The purpose of the trial reported here was to investigate the effect of concentrate energy source on lactation performance of dairy cows.30 autumn calving multiparous Friesian cows were fed one of two concentrates which were formulated to isoenergetic extremes of starch and fibre content.Three weeks before their expected calving date cows were housed in cubicles with access to Calan individual feeders. Following equalised concentrate feeding in a post-parturn covariance period, one of each pair (Pairing having been on the basis of previous milk yield, milk composition and expected calving date) was gradually introduced to its designated concentrate over a five day period. Cows were flat rate fed at 7, 10 or 13 kg concentrate DM/d (depending upon yield potential) from day 20 of lactation for 10 weeks. Concentrates were fed in three equal feeds daily.

The influence of a formulated excess of rumen degradable protein or undegradable protein on milk production in dairy cows in early lactation

ABSTRACTFollowing a 3-week covariance period, 30 group-housed dairy cows were individually given one of three diets from week 4 to week 13 of lactation to determine any possible advantage in milk yield and production of feeding levels of undegradable protein (+UDP) or rumen-degradable protein (+RDP) above the minimum levels (control) proposed by the Agricultural Research Council (ARC, 1984). The three concentrates given were formulated to be of equivalent metabolizable energy (ME, 13·5 MJ/kg dry matter (DM)) concentration and each consisted of rolled barley plus a protein supplement: control (crude protein (CP), 129 g/kg DM) 0·35 kg DM fish meal per day; +UDP (CP, 167 g7kg DM) 1·0 kg DM fish meal per day; and +RDP (CP, 167 g/kg DM) 1+5 kg DM soya per day. For each group the total ‘concentrate’ allowance per animal per day was 11·6 kg fresh weight and was given in three equal feeds. Grass silage (CP 122 g/kg DM, ME 106 MJ/kg DM) was given ad libitum. For the control, +UDP and +RDP treatments, respectively, mean grass silage intakes were 8·29, 8·62 and 8·65 kg/day and mean milk yields were 26·6, 26·3 and 26·1 kg/day. These were not significantly different (P > 0·05). Milk fat concentration was lower (P < 0·05) for the +UDP treatment (36·4 g/kg) in comparison with the control (38·6 g/kg) or the +RDP treatment (39·7 g/kg) but no other milk constituent was significantly influenced by treatment. There was a trend for a greater live-weight gain with treatment +UDP (0·81 kg/day) compared with the other two treatments (control 0·50, +RDP 0·51 kg/day) but there were no differences in condition-score change between treatments. In this trial there was no advantage to feeding formulated levels of UDP or RDP above those proposed by ARC (1984).

A comparison of four patterns of allocating maize during lactation to Friesian cows grazing tropical pastures

Milk yields were compared over a 280-day lactation using four patterns of allocation of a fixed amount of grain. Four groups of four Friesian cows grazed a mixed tropical grass (Panicum maximum) and legume (Neonotonia wightii cv. Tinaroo) pasture at 1.1 cows/ha from January to December 1980. The lactation was split into four feeding periods: days 1 - 10,11- 100,10 1 - 190, 191-280. All cows were fed a total of 610 kg hammermilled maize, with 10 kg grain fed during the initial covariate period. The four feeding patterns were: (i) flat rate (FR), where cows received 2.22 kg grain/day; (ii) all early (AE), where cows received 600 kg grain between days 11 and 100; (iii) high early, low late (HELL), where cows were fed 3.5, 2.17 and 1.0 kg/day for periods 11-100,101-190and 191- 280 days of lactation; and (iv) low early, high late (LEHL), where cows were fed in the reverse pattern to HELL. Milk yields per cow over 280 days were 4145, 3942, 3794 and 3630 kg [l.s.d. (P=0.05)= 436 kg] for HELL, FR, LEHL and AE respectively. There was very poor utilization of grain by cows fed AE. The relation between milk yield and grain intake in days 1 1-100 of lactation was described by the equation: Y= 13.9+ 1.77X-0.18X2 (P<0.01, s.e.b1= 0.48, s.e.b2 = 0.06), where Y = milk yield (kg/cow.day) and X = grain intake (kg/cow.day). Apportioning more grain to late lactation, when pasture on offer was low, did not compensate for the loss of milk production in early lactation by cows fed LEHL. Cows fed LEHL lost more liveweight in early lactation than all other treatments, but regained this weight in late lactation. Cows in all treatments had similar liveweights (mean 518 kg) at 280 days. Milk butterfat and solids-not-fat yields over 280 days were not significantly different (P>0.05) for any of the four treatments.

Effect of Dietary Protein Degradability on Cows in Early Lactation

Five completely mixed isocaloric diets were formulated with ratio of 50:50 roughage: concentrate (dry matter) to vary in protein degradability. Three diets at 14% crude protein included 10.8% soybean meal (diet 1), 8.0% corn gluten meal plus .5% urea (diet 2), or 10.6% corn gluten meal (diet 3) as the protein source. Diet 4 was 17% crude protein with soybean meal and diet 5, 12.6% protein with urea. Protein disappearance after 24-h nylon bag incubation in rumen fistulated steers was 54, 49, 43, and 58% for diets 1 to 4. Diets were fed to 45 Holstein cows averaging 35 (±14) days postpartum with a 2-wk covariate and a 6-wk experimental period. Cows were fed diet 1 during the covariate period. Treatment means adjusted by covariance for the variable and days postpartum, for average daily milk yield, milk fat percent, milk protein percent, milk lactose percent, and solids-corrected milk were 30.8, 2.95, 3.07, 5.08, and 28.5; 32.9, 2.40, 2.96, 5.20, and 26.2; 34.2, 2.71, 2.88, 5.18, and 27.8; 36.7, 2.81, 3.09, 5.10, and 28.5; 31.7, 2.43, 2.93, 5.24, and 25.4 for diets 1 to 5. Decreasing dietary protein degradability at a 14% crude protein increased milk production, decreased milk protein percent and had a quadratic effect on milk fat percent. Increasing dietary protein percent raised milk yields, milk protein percent, and solids-corrected milk yield.