The effect of ammonia treatment on the intake of straw and hay when offered with rations of concentrates to ewes in late pregnancy

Effect of feeding level in late pregnancy and early lactation and fibre level in mid lactation on body mass, milk production and quality in Awassi ewes

In west Asia, it is traditional for sheep to gain body condition when low-cost native pastures are available and to mobilize reserves thus built up at other times. With diminishing shares of native pasture, crop by-products and food grains are increasing in sheep diets, and facilitate feeding for constant body condition.

In a 2 × 2 × 2 factorial experiment, 48 Awassi ewes were individually fed indoors, nursed single lambs for 42 days, and were hand-milked from day 29 after lambing. Dietary treatments were imposed at different times: level of feeding (i) in the last 24 days of pregnancy (Lconstv. Lmob), (ii) in days 18 to 60 after lambing (Lconstv. Lmob), and (iii) level of fibre in days 60 to 102 after lambing (Fhighv. Flow). RationsPconst, Lconst, Flowand Fhighwere calculated to maintain body condition. Fhighprovided the calculated maximum ingestible quantity of barley straw and Flowprovided 0·08 kg barley straw per kg diet. Live weights (M) of ewes and lambs, milk yield and milk quality were recorded.

WithPconst, andPmob(0·51 and 0·33 MJ metabolizable energy (ME) per kg M0.75per day), M gains were 140 and 23 g/day (P< 0·001). Lamb birth mass and subsequent maternal milk yield were not affected. WithLconstandLmob(0·81 and 0·61 MJ ME per kg M0.75 per day), M changes were -28 and -70 g/day (P< 0·001) and milk yields (calculated in part from lamb growth) were 1042 and 892 g/day (P < 0·01). Fhighand Flow(385 and 170 g acid-detergent fibre per kg dry matter) were compared in a two-period change-over design experiment. Milk yields were similar (414 and 427 g/day), milk fat concentrations were 64·8 and 72·9 g/kg (P < 0·001) and milk fat yields were 26·5 and 31·1 g/day (P < 0·001) but solids-not-fat and protein yields were not affected.

There were benefits and costs in manipulating body reserves in Awassi sheep. M at lambing affects milk yield and body condition around mating is known to improve lambing rate. The existence of body reserves also allows body condition to be lost in late pregnancy and early lactation without affecting health or apparent welfare, which simplifies management of pregnant ewes, permits feeding of milk-fat-increasing high-fibre diets but the ME to maintain increased body reserves must not be ignored.

The performance of ewes offered concentrates containing olive by-products in late pregnancy and lactation

Ewes of the Segureña breed were allocated to groups and were group-fed different diets composed of concentrates and roughage (lucerne hay in experiment 1 and barley straw in experiment 2), in late pregnancy and lactation. The concentrates were formulated with sunflower cake and barley, either alone (control group) or partly replaced with olive cake (OLC) and olive molasses (OLM) in a 5:1 ratio. The OLC was either untreated or was treated with NaOH or ammonia. Concentrates were given to provide proportionately 0·4 and 0·7 of calculated metabolizable energy (ME) requirements in experiments 1 and 2 respectively. In experiment 2 a further group grazed pasture and was given barley at a reduced rate.

In experiment 1, the mean ME intake during late pregnancy (5+1 weeks pre-lambing) for all treatment groups was about 796 kj/kg M0·75 per day and largely exceeded their average energy requirements, whereas it was close to requirements (601 kj/kg M0·75 per day) in experiment 2. During lactation, ME intake was adjusted to the theoretical needs for ewes suckling a single lamb (835 to 870 kj/kg M0·75 per day) and was slightly deficient (990 to 1020 kj/kg M0·75 per day) for ewes with twins, irrespective of both treatment (except the group at pasture) and experiment.

Minor differences in animal performance, attributed to the type of concentrate offered, were found. In pregnancy, alkali treatment of OLC significantly improved live-weight gains (P < 0·01). Live-weight gains of ewes in experiment 2 were lower than those in experiment 1 in accordance with their lower ME intake, the lowest gains being found in the group at pasture (P < 0·05). Weight losses in lactating ewes in experiment 1 were 17 to 100 and 9 to 165 g per ewe per day for ewes suckling single and twin lambs respectively. In experiment 2 ewes with twins gained weight, while those with single lambs showed little weight change, although differences between experiments were too small to attain statistical significance. No differences in barley straw intake by pregnant ewes were found between treatment groups. However, the intake of barley straw by lactating ewes in the groups offered concentrates containing OLC and OLM was significantly higher than that by controls (P < 0·05).

Birth weight of lambs tended to be higher in experiment 2 when ewes consumed less ME during pregnancy, although variations were not statistically significant. The most important cause of growth rate variation was the number of lambs born to a ewe (P < 0·001). The growth rate of lambs in the outdoor group was significantly lower than that of lambs in the indoor groups (P < 0·05).

The effect of concentrate level on the intake of grass silages by ewes in late pregnancy

In two experiments, six silages were offered either alone or with constant daily levels of a barley-based concentrate (450 or 900 g fresh weight per ewe) to Finn Dorset ewes carrying between one and four foetuses in the last 6 weeks of pregnancy. The silages (SI to S3, experiment 1 and S4 to S6, experiment 2) had dry matter (DM) concentrations of 256, 190, 278 and 294, 216, 201 g/kg fresh weight and crude protein (CP) concentrations of 106, 164, 212 and 119, 148, 194 g/kg DM. Mean metabolizable energy (ME) concentrations of the silages (digestible energy × 0·81), in weeks 16 and 20, were 9·2, 10·3, 12·0 and 8·8, 10·9, 11·0 MJ/kg DM. Total ME intakes were 12·6, 13·5, 18·6 and 14·5, 15·1, 16·8 MJ/day in week 16 of gestation and were 11·6, 11·2, 17·2 and 12·2, 11·8, 13·3 MJ/day in week 20. Total ME intakes were increased by offering higher levels of concentrates and for levels of 0, 450 or 900 g/day these were 12·3, 14·8, 17·9 MJ/day in week 16 and 9·6, 12·8, 15·5 MJ/day in week 20. Intakes were similar for ewes carrying twins or multiples in experiment 1, but in experiment 2, intakes by ewes with twins or multiples were proportionately 0·97 and 0·85 of those for ewes with singles. Replacement rates of forage by concentrates were —0·09, —0·08, —0·60 and —0·06, —0·25, —0·38 g silage organic matter (OM) per g concentrates OM for silages SI to S3 and S4 to S6. Only on silage S6 did the replacement rate differ significantly from zero.

Nutrition over the winter period — the breeding female

Due to the wide variation in both the productivity of sheep systems and the quality of the food resources that they utilize, the formulation of successful feeding strategies for individual flocks during pregnancy and lactation is best achieved from a knowledge of how these physiological states affect food digestion and nutrient utilization. This paper reviews recent data on the principles of food digestion and nutrient utilization in the breeding ewe and translates them into practical feeding regimens that take account of forage quality, the amount and quality of the concentrate supplement and the contribution that body and dietary lipids can make to production.

Voluntary dry-matter intake and digesta kinetics of twin- or single-bearing Manchega ewes given Italian ryegrass hay or alfalfa hay in late pregnancy

Forty-eight pregnant Manchega dairy ewes bearing twins or singles penned in groups of six during the last 11 weeks of gestation were used to study the effects offorage type (Italian ryegrass hay or alfalfa hay) and number of foetuses (one or two) on voluntary dry-matter (DM) intake and digesta kinetics. Hays were supplemented with 0·6 kg/day of concentrate. When measured directly for group-fed ewes, forage DM intake was affected byforage type (P < 0·01), whereas litter size had no significant effect. An internal (rumen-undegradable DM) and an external (chromium III oxide) marker were also used to determine intake of individual ewes to account for errors in diagnosing litter size. Estimated DM intake confirmed the effect offorage type on DM intake and revealed the effect of litter size on food intake (F < 0·05). Forage type also affected chromium III oxide fractional outflow rate and flow of undegradable DM, whereas litter size only had an effect at the end of pregnancy by reducing hay intake, rate of passage and digesta flow mainly with alfalfa diets. In conclusion, DM intake, rate of passage and digesta flow was higher with alfalfa hay than with ryegrass hay, in spite of the similar DM apparent digestibilities of both hays. Furthermore, litter size affected DM intake at the end of pregnancy causing an intake decline, which was greater with alfalfa hay than with ryegrass hay.

Rumen degradation of straw 1. Untreated and ammonia-treated barley, oat and wheat straw varieties and triticale straw

The dry-matter degradation of 19 varieties of barley, 14 varieties of wheat, 11 varieties of oats and one variety of triticale straws, both untreated and ammonia treated were studied using the nylon-bag technique. There were significant differences between the untreated varieties of all the types of cereal straw studied with respect to dry-matter loss (DML) values. When the barley and wheat straws were treated with ammonia, the differences between the varieties were also significant although ammonia treatment tended to improve those with lower values to a greater extent than those with higher values. There were also significant differences between the DML values of the oat straws when they were treated with ammonia but only after 48-h incubation. There was a significant negative relationship between the 48-h DML values of the untreated oat straws and the improvement in the DML values with ammonia treatment (r = −0·65; P < 0·05). Grain yield, straw length and nitrogen concentration had no significant relationship with the DML values of the untreated straws. Barley and oat straws had generally higher DML than the wheat and triticale straws.

The intake and digestion of a range of temperate forages by sheep and fibre-producing goats

The voluntary intake, digestibility and mean retention time of six temperate forages differing in their chemical composition by 12 adult castrated male Scottish blackface sheep, aged 15 months, and fibre-producing castrated male goats, aged 27 months, and of similar live weight, 40kg, were described. The creation of a range of chemical compositions was effected through the use of barley straw, and a low- and high-digestibility hay, and the use of ammonia treatment of these forages. A wide range of voluntary intakes (42-78gDM/kgW(0.75)/day), digestibility of dry matter (0.46-0.60) and mean retention times of undigested residues (36-72h) was achieved through feeding the six forages. Across all the forages fibre-producing goats had higher voluntary intakes, expressed on a metabolic live weight basis, and lower digestibility values than sheep, whereas the mean retention time of the undigested residues was similar for the two species. Within forages goats selected a diet of potentially higher nutritive value, as predicted from chemical composition, with a smaller particle size than sheep. It was concluded that the differences in intake and digestion of temperate forages between sheep and fibre-producing goats are broadly similar to those observed in other experiments between sheep and goats ingesting tropical forages.